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1
Jones, Dan, Justin Windham, Brian Stewart, Luis Fayad, Alma Rodriguez, and Fredrick B. Hagemeister. "Differential JAK-STAT Pathway Activation in Primary Mediastinal Large B-Cell Lymphoma: Two Subgroups with Differential Cytokine Activation Patterns and Predicted Responses to Kinase Inhibitors." Blood 114, no. 22 (November 20, 2009): 968. http://dx.doi.org/10.1182/blood.v114.22.968.968.
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Abstract Abstract 968 Background: Primary mediastinal large B-cell lymphoma (PMBCL) is a specialized type of diffuse large B-cell lymphoma which shows diagnostic and pathogenetic overlap with mediastinal classical Hodgkin lymphoma. Approximately 60% of patients with PMBCL have good response to conventional chemoradiotherapy with the rest often showing distant relapses. Microarray studies of PMBCL have revealed overexpression of components and targets of the JAK-STAT signaling pathways including upregulation of IL13 receptor and STAT1; a subset of PMBCL have genome amplification of JAK2 or deletion of the JAK suppressor SOCS1. Given this complexity, we examined the most common mechanism and effects of JAK-STAT dysregulation in a series of newly diagnosed and recurrent PMBCL. Methods: Fifty-three biopsies from 23 patients with PMBCL were assessed and correlated with outcome. JAK2 and SOCS1 copy number status were determined by quantitative PCR on genomic DNA. JAK-STAT pathway activation was probed using reverse transcription quantitative (RQ)-PCR for JAK2, JAK3, and a panel of IL-4 and IL-13 transcriptional targets. JAK-STAT activation was assessed in tissue arrays using antisera against phospho-activation epitopes of STAT1, STAT3, STAT5, and STAT6 using immunohistochemistry (IHC). Activation patterns were modeled in the PMBCL cell line Karpas (K)1106P at baseline and following IL-4 and IL-13 stimulation with or without a range of small molecule inhibitors and blocking antibodies. Growth parameters were measured by MTT and protein levels by flow cytometry, Western blot, RQ-PCR and kinase profiling. Results: JAK2 genomic amplification was present in 40% of PMBCL and SOCS1 deletion in 10% as well as in the K1106P line. By phospho-activation IHC, tumors in 20/23 (87%) patients showed STAT activation, mostly due to STAT1 (60.8%) followed by STAT3 (26.1%), with 6 cases showing mixed patterns. In different tumors, localized and uniform STAT activation patterns were seen. Constitutive STAT activation was correlated with high expression of IL-4 transcription targets including CCL17 and IL13RA as well as JAK2 autophosphorylation and inferior outcome (p = .007). Tumors with more localized foci of activation were associated with alternate transcription patterns. In the K1106P cell line, IL-4 but not IL-13 treatment led to inducible STAT1 activation whereas baseline STAT3/6 activation was highly regulated by cytokine exposure. The JAK2 inhibitor JSI124 blocked IL-4 induced STAT1 activation whereas the JAK inhibitors AG-490, NSC7908 and WHI-P154 did not but did block IL-4/IL-13-induced STAT3 activation. The JAK3 inhibitor ZM39923 was most effective in blocking cell growth but did not block STAT1 activation. Conclusions: JAK2-STAT pathway activation characterizes nearly all cases of PMBCL but genetic mechanisms are distinct leading to distinct patterns of STAT1 activation (driven predominantly through the type I IL-4 receptor) and STAT3/6 activation (driven predominantly through the type II IL13RA/IL4RA) with differential effects on growth parameters and gene regulation. The patterns of STAT activation and target gene expression in primary tumors comprising these two groups mirrored the response to small molecule inhibitors following cytokine exposure in vitro in the K1106P line and highlights differences between IL-4 and IL-13 signaling in PMBCL. Profiling of PMBCL biopsies with phosphoactivation IHC for STAT isoforms may be useful to subcategorize cases and select the optimal JAK-STAT pathway inhibitors for adjuvant therapy. Disclosures: No relevant conflicts of interest to declare.
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Hu, Cheng-Ping, Jun-Tao Feng, Yu-Ling Tang, Jin-Qi Zhu, Min-Juan Lin, and Ming-En Yu. "LIF Upregulates Expression of NK-1R in NHBE Cells." Mediators of Inflammation 2006 (2006): 1–8. http://dx.doi.org/10.1155/mi/2006/84829.
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Leukemia inhibitory factor (LIF), a cytokine at the interface between neurobiology and immunology, is mainly mediated through JAK/STAT pathway and MAPK/ERK pathway. Evidence suggested LIF is related to the higher expression of neurokinin-1 receptor (NK-1R) in asthma. In this study, the immunohistochemistry stain showed the expressions of NK-1R, LIF, p-STAT3, and p-ERK1/2 in the lung tissues of allergic rats were increased compared with the controls, and the main positive cell type was airway epithelial cell. Normal human bronchial epithelial cells were treated with LIF in the presence or absence of AG490 (JAK2 inhibitor), PD98059 (MEK inhibitor), and the siRNA against STAT3. Western blot and RT-PCR indicated that LIF induced the expression of NK-1R, which was inhibited by the inhibitors mentioned above. No significant interaction was found between JAK/STAT pathway and MAPK/ERK pathway. In summary, bronchial epithelial cell changes in asthma are induced by LIF which promotes the expression of NK-1R, and JAK/STAT pathway and MAPK/ERK pathway may participate in this process.
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Zhang, Xuekang, Jun Zhou, Qian Hu, Zhengren Liu, Qiuhong Chen, Wenxiang Wang, Huaigen Zhang, Qin Zhang, and Yuanlu Huang. "The Role of Janus Kinase/Signal Transducer and Activator of Transcription Signalling on Preventing Intestinal Ischemia/Reperfusion Injury with Dexmedetomidine." Journal of Nanoscience and Nanotechnology 20, no. 5 (May 1, 2020): 3295–302. http://dx.doi.org/10.1166/jnn.2020.16416.
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Dexmedetomidine (Dex) works as a crucial agent for the treatment of intestinal ischemia/reperfusion (I/R), but its mechanism remains unclear. Recent articles demonstrated the pivotal role of Janus kinase/signal transducer and activator of transcription (JAK2/STAT3) signalling in I/R. Therefore, it is reasonable to explore the associated mechanism of JAK2/STAT3 signalling in Dex treatment. The study purpose was to evaluate the JAK2/STAT3 signalling regulatory mechanisms of Dex in preventing I/R. Anaesthetized rats were subjected to superior mesenteric artery occlusion consisting of 1 h of ischemia and 2 h of reperfusion while served as controls. Animals received subcutaneous administration of 50 μg/kg Dex, JAK1 and JAK2 inhibitor, Ruxolitinib, selective JAK2 inhibitor, 10 mg/kg AG490 or STAT inhibitor and 0.4 mg/kg rapamycin; or Dex-treatment in the presence of α2-adrenoceptor antagonists Atip or Dex-treatment alone after I/R. Injury was scored histologically, apoptosis was detected via the apoptotic mediators caspase-3 and Bcl-2/Bax and the degree of activation of the JAK/STAT pathway was evaluated. Dex inhibited I/R injury by decreasing apoptosis significantly with rescue of cleaved caspase-3 and the Bcl-2/Bax ratio. Furthermore, phosphorylation of JAK2, STAT1 and STAT3 was affected, suggesting the involvement of activated JAK/STAT in response to Dex. Meanwhile, the JAK2 or STAT inhibitors AG490 and rapamycin, but not Ruxolitinib, exhibited a similar but even greater JAK2 and STAT3 regulatory effect, thus leading to a greater benefit. JAK2/STAT3 activation is crucial to the diminishing effect of Dex on mesenteric I/R injury; however, the efficacy and timing of Dex administration should be considered in clinical practice.
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Zhao, Lan-Juan, Sheng-Fei He, Yuan Liu, Ping Zhao, Zhong-Qi Bian, and Zhong-Tian Qi. "Inhibition of STAT Pathway Impairs Anti-Hepatitis C Virus Effect of Interferon Alpha." Cellular Physiology and Biochemistry 40, no. 1-2 (2016): 77–90. http://dx.doi.org/10.1159/000452526.
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Background/Aims: Signal transducer and activator of transcription (STAT) pathway plays an important role in antiviral efficacy of interferon alpha (IFN-α). IFN-α is the main therapeutic against hepatitis C virus (HCV) infection. We explored effects of IFN-α on HCV replication and antiviral gene expression by targeting STAT. Methods: In response to IFN-α, STAT status, HCV replication, and antiviral gene expression were analyzed in human hepatoma Huh7.5.1 cells before and after cell culture-derived HCV infection. Results: IFN-α treatment induced expression and phosphorylation of STAT1 and STAT2 in Huh7.5.1 cells. Pretreatment of Huh7.5.1 cells with a mAb to IFN alpha receptor (IFNAR) 2 decreased IFN-α-dependent phosphorylation of STAT1 and STAT2, whereas pretreatment with an IFNAR1 mAb increased such phosphorylation, suggesting that IFNAR mediates IFN-α-triggered STAT signaling. During HCV infection, STAT1 and STAT2 phosphorylation could be rescued by IFN-α and IFN-α-induced phosphorylation of STAT1 and STAT2 was impaired. Inhibition of STAT pathway by Jak inhibitor I significantly enhanced HCV RNA replication and viral protein expression. Antiviral genes coding for IFN regulatory factor 9 and IFN-stimulated gene 15 were up-regulated by IFN-α during HCV infection but such up-regulation was abrogated by Jak inhibitor I. Conclusion: These results establish that activation of STAT pathway is essential for anti-HCV efficacy of IFN-α. Impairment of IFN-α-triggered STAT signaling by HCV may account for evading IFN-α response.
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Kim, Byung-Su, Chansu Lee, Juwon Park, Kwang-Sung Ahn, Byoung Kook Kim, Seonyang Park, Young-Yiul Lee, and Sung-Soo Yoon. "Inactivation of JAK/STAT Cell Signaling by SK-7041, a Novel HDAC Inhibitor, Effectively Inhibits Growth of Acute Myeloid Leukemia Cells." Blood 112, no. 11 (November 16, 2008): 4005. http://dx.doi.org/10.1182/blood.v112.11.4005.4005.
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Abstract Activation of the JAK/STAT pathway appears common in AML, occurring in up to 70% of AML patients. Therefore, JAK/STAT signal inhibitors are promising as candidate anti-cancer agents in AML. Recently, we reported that SK-7041, an HDAC inhibitor, inhibited the growth of AML cells via activation of caspase-3 and down-regulation of cyclin D1. These findings lead us to further examine whether SK-7041 inhibits the growth of KG1 AML cells via inactivation of JAK/STAT signals. Multi-immunoblotting technique (Kinetworks™ analysis) showed that expression of p-STAT-3, p-STAT-5, and p-Erk was down-regulated in KG1 cells treated with SK-7041. These results were confirmed by individual western blot analysis. In addition, IL-6-induced activation of STAT-3 and Erk was inhibited by treatment of SK-7041. Combined treatment of SK-7041 and JAK inhibitor (AG490) showed additive anti-leukemic effect as evidenced by caspase-3 activation, down-regulation of cyclin D1 (cMYC), and inhibition of phosphorylation of STATs (−1, −3). These results suggest that HDAC inhibitor, SK-7041, inhibited AML cell growth via inactivation of JAK/STATs pathway.
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Barclay, J. L., T. Wonisch, S. T. Anderson, M. J. Waters, and J. D. Curlewis. "124. Regulation of SOCS3 expression by prostaglandin, prolactin and growth hormone: challenging the Jak/STAT signalling dogma." Reproduction, Fertility and Development 17, no. 9 (2005): 74. http://dx.doi.org/10.1071/srb05abs124.
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SOCS3 is an inhibitor of various cytokine-receptor signalling pathways and is therefore involved in suppression of cellular responsiveness to these critical regulators. SOCS3 expression is thought to be regulated by a STAT responsive element (SRE). However, our research suggests the involvement of other signalling pathways. In T-47D breast cancer cells, we found that PGE2 induces a 3–5 fold increase in SOCS3 mRNA, as determined by real-time PCR. This effect was not due to phosphorylation of STATs, or inhibited by the Jak2 inhibitor, AG490, but was inhibited by the PI3Kinase inhibitor, LY294002, Akt Inhibitor IV and partially inhibited by the PKA inhibitor, H89. It was not affected by inhibitors of MEK, PDK1, mTOR or p38-MAPK. We concurrently examined PRL-induced SOCS3 expression, and found that although STAT1 and 5 phosphorylation was increased, SOCS3 expression was again inhibited by Akt Inhibitor IV and H89 but unaffected by AG-490. To explore this further, we used a model of GH signalling, BaF3 cells stably expressing GH receptor. GH induced a 15–20 fold increase in SOCS3 mRNA, which was accompanied by increased STAT5 phosphorylation. However the SOCS3 response was not inhibited by AG-490 or H89, but was diminished by Akt Inhibitor IV. Analysis of the SOCS3 promoter revealed a FOXO binding site. When we mutated this site in a mouse SOCS3 promoter–luciferase construct, basal and GH-induced promoter activity was significantly increased. These results are consistent with FOXO acting as a repressor, which is inactivated by Akt. We propose that in T-47D cells, SOCS3 expression involves cross-talk between PI3K/Akt and cAMP/PKA, whereas in BaF3 cells, expression is enhanced by Akt phosphorylation and subsequent FOXO inactivation. These findings contrast with the accepted Jak/STAT regulation of SOCS3 expression. This work is supported by the Australian Research Council.
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Kitanaga, Yukihiro, Emiko Imamura, Yutaka Nakahara, Hidehiko Fukahori, Yasutomo Fujii, Satoshi Kubo, Shingo Nakayamada, and Yoshiya Tanaka. "In vitro pharmacological effects of peficitinib on lymphocyte activation: a potential treatment for systemic sclerosis with JAK inhibitors." Rheumatology 59, no. 8 (November 25, 2019): 1957–68. http://dx.doi.org/10.1093/rheumatology/kez526.
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Abstract Objectives Peficitinib, a novel Janus kinase (JAK) inhibitor, demonstrated promising results in treating RA in phase 3 clinical trials. This in vitro study was undertaken to characterize the pharmacological properties of peficitinib and investigate the involvement of JAK and signal transducer and activator of transcription (STAT) pathways in the pathological processes of SSc, which is also an autoimmune disease. Methods Phosphorylation levels of STAT molecules were assessed in peripheral blood mononuclear cells collected from patients with RA or SSc and healthy subjects, and in skin specimens obtained from 19 patients with SSc. In vitro inhibition of STAT phosphorylation and cytokine/chemokine production by peficitinib, tofacitinib and baricitinib were also characterized. Results Higher spontaneous STAT1 or STAT3 phosphorylation was observed in peripheral T-cells and monocytes from patients with RA and SSc compared with healthy subjects. In skin sections from patients with SSc, phosphorylated STAT3–positive cells were found in almost all cases, irrespective of disease subtype or patient characteristics. Conversely, phosphorylated STAT1-positive cells were observed only in samples from untreated patients with diffuse disease of short duration. Peficitinib inhibited STAT phosphorylation induced by various cytokines, with comparable efficacy to tofacitinib and baricitinib. Peficitinib also suppressed cytokine and chemokine production by peripheral blood mononuclear cells and skin fibroblasts. Conclusion Our results suggest that JAK/STAT pathways are constitutively activated in SSc and RA, and that the JAK inhibitor may represent a novel therapeutic option for SSc.
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Zhou, Jianbiao, Chonglei Bi, Lai Fong Poon, Viraj J. Janakakumara, Jiaying Khng, Hanry Yu, Keith B. Glaser, Daniel H. Albert, Davidsen K. Davidsen, and Chien-Shing Chen. "Overactivation of STAT Pathways and Overexpression of Survivin Confer Resistance to FLT3 Inhibitors and Could Be Therapeutic Targets in AML." Blood 110, no. 11 (November 16, 2007): 2367. http://dx.doi.org/10.1182/blood.v110.11.2367.2367.
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Abstract Internal tandem duplication (ITD) of fms-like tyrosine kinase 3 (FLT3) receptor plays an important role in the pathogenesis of acute myeloid leukemia (AML). A number of small molecule kinase inhibitors are currently proceeding in different phases of clinical trials. As with imatinib in CML, leukemic cells could develop resistance to these RTK inhibitors when used as monotherapy. Mutations in the ATP-binding pocket have been identified through PCR-based mutagenesis screening in Ba/F3-FLT3-ITD cells and selected for growth in the presence of PKC412, or in a resistant Ba/F3-FLT3-ITD cell line developed by cocultured with SU5416. Resistance to PKC412 resulting from the N676K point mutation in the FLT3 kinase domain has been described in a clinical trial patient. Selection of activating Ras mutations has been found in 2 out of 6 FLT3 inhibitor resistant cell lines, but no point mutation of FLT3 kinase domain was found in all 6 resistant cell lines. To further investigate other potential mechanisms of resistance to FLT3 inhibitors, we developed a resistant cell line by long-term culture of MV4-11 cells with ABT-869, designated as MV4-11-R (IC50: 52 vs 6 nM for the parental MV4-11 cell line), which is also cross resistant to other structurally unrelated inhibitors including SU5416, AG1296 and a FLT3 inhibitor III (MERCK). No point mutation in the kinase domain of FLT3 was found in MV4-11-R cells. Western blot and FACS analysis excluded overexpression of p-FLT3, FLT3 or 3 multidrug resistance related proteins (MDR, MRP1 and LRP) in this resistant line. Gene expression profiling revealed up-regulation of FLT3 ligand (FLT3LG) (2.4 fold) and Survivin (2 fold), while down-regulation of SOCS1, SOCS2, and SOCS3 was observed in MV4-11-R compared to MV4-11 parental cells. Overexpression of FLT3LG and Survivin was also demonstrated at the protein level. Survivin is a unique member of the inhibitor of apoptosis proteins (IAP) family and a known target of the STAT3 pathway. Down-regulation of suppressor of cytokine signaling (SOCS) proteins (negative regulators of STAT pathways) was observed even in the presence of overactivation of the STAT1, STAT3 and STAT5 pathways in the MV4-11-R line. We screened a panel of small molecule inhibitors including a STAT inhibitor (indirubin derivative IDR E804), 3 JAK inhbitors (Tyrene CR4, AG490, and JAK3 Inhibitor II), and a CDK/survivin inhibitor (NU6140). We found that MV4-11-R is most sensitive to IDR E804 (an inhibitor of CDKs and the SRC-STAT3 pathway). The IC50 value of ABT-869 in MV4-11-R was decreased from 52 to 6.2 nM in the presence of 2 nM of IDR E804. Further validation of the therapeutic effect of IDR E804 in combination with ABT-869 in the MV4-11-R mouse xenograft model is ongoing. Targeting Survivin by shRNA and a dominant-negative vector (survivin-T34A) induced MV4-11-R to undergo apoptosis. Taken together, these results demonstrate that overactivation of STAT pathways and overexpression of survivin are the main mechanism of resistance to ABT-869; suggesting that the STAT pathways and survivin could be potential targets for the treatment of patients who develop resistance to FLT3 inhibitors.
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Banes, Amy K., Séan Shaw, John Jenkins, Heather Redd, Farhad Amiri, David M. Pollock, and Mario B. Marrero. "Angiotensin II blockade prevents hyperglycemia-induced activation of JAK and STAT proteins in diabetic rat kidney glomeruli." American Journal of Physiology-Renal Physiology 286, no. 4 (April 2004): F653—F659. http://dx.doi.org/10.1152/ajprenal.00163.2003.
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Clinical and animal studies show that treatment with angiotensin-converting enzyme (ACE) inhibitors or ANG II-receptor antagonists slows progression of nephropathy in diabetes, indicating ANG II plays an important role in its development. We previously reported that hyperglycemia augments both ANG II-induced growth and activation of Janus kinase (JAK)2 and signal transducers and activators of transcription (STAT) proteins in cultured rat mesangial cells. Furthermore, we demonstrated that the tyrosine kinase enzyme JAK2 plays a key role in both ANG II- and hyperglycemia-induced growth in these cells. We hypothesized that the ACE inhibitor captopril and the ANG II-receptor antagonist candesartan would hinder hyperglycemic-induced activation of JAK and STAT proteins in rat glomeruli, demonstrating that ANG II plays an important role in the activation of these proteins in vivo. Adult male Sprague-Dawley rats were given either streptozotocin (STZ; 60 mg/kg iv) or vehicle, and glomeruli were isolated 2 wk later. Activation of JAK and STAT proteins was evaluated by Western blot analysis for specific tyrosine phosphorylation. Groups of rats were given captopril (75–85 mg·kg-1·day-1), candesartan (10 mg· kg-1·day-1), or the JAK2 inhibitor AG-490 (5 mg·kg-1·day-1) for the study's duration. STZ stimulated glomerular phosphorylation of JAK2, STAT1, STAT3, and STAT5. Phosphorylation was reduced in rats treated with captopril, candesartan, and AG-490. Furthermore, both candesartan and AG-490 inhibited STZ-induced increases in urinary protein excretion. In conclusion, our studies demonstrate that hyperglycemia induces activation of JAK2 and the STATs in vivo via an ANG II-dependent mechanism and that these proteins may be involved in the early kidney damage associated with diabetes.
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Alunno, Alessia, Ivan Padjen, Antonis Fanouriakis, and Dimitrios T. Boumpas. "Pathogenic and Therapeutic Relevance of JAK/STAT Signaling in Systemic Lupus Erythematosus: Integration of Distinct Inflammatory Pathways and the Prospect of Their Inhibition with an Oral Agent." Cells 8, no. 8 (August 15, 2019): 898. http://dx.doi.org/10.3390/cells8080898.
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Four Janus kinases (JAKs) (JAK1, JAK2, JAK3, TYK2) and seven signal transducers and activators of transcription (STATs) (STAT1, STAT2, STAT3, STAT4, STAT5A, STAT5B, STAT6) mediate the signal transduction of more than 50 cytokines and growth factors in many different cell types. Located intracellularly and downstream of cytokine receptors, JAKs integrate and balance the actions of various signaling pathways. With distinct panels of STAT-sensitive genes in different tissues, this highly heterogeneous system has broad in vivo functions playing a crucial role in the immune system. Thus, the JAK/STAT pathway is critical for resisting infection, maintaining immune tolerance, and enforcing barrier functions and immune surveillance against cancer. Breakdowns of this system and/or increased signal transduction may lead to autoimmunity and other diseases. Accordingly, the recent development and approval of the first small synthetic molecules targeting JAK molecules have opened new therapeutic avenues of potentially broad therapeutic relevance. Extensive data are now available regarding the JAK/STAT pathway in rheumatoid arthritis. Dysregulation of the cytokines is also a hallmark of systemic lupus erythematosus (SLE), and targeting the JAK/STAT proteins allows simultaneous suppression of multiple cytokines. Evidence from in vitro studies and animal models supports a pivotal role also in the pathogenesis of cutaneous lupus and SLE. This has important therapeutic implications, given the current paucity of targeted therapies especially in the latter. Herein, we summarize the currently available literature in experimental SLE, which has led to the recent promising Phase II clinical trial of a JAK inhibitor.
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Kim, Dong Wook, Young Suk Jo, Hye Sook Jung, Hyo Kyun Chung, Jung Hun Song, Ki Cheol Park, Su Hyeon Park, et al. "An Orally Administered Multitarget Tyrosine Kinase Inhibitor, SU11248, Is a Novel Potent Inhibitor of Thyroid Oncogenic RET/Papillary Thyroid Cancer Kinases." Journal of Clinical Endocrinology & Metabolism 91, no. 10 (October 1, 2006): 4070–76. http://dx.doi.org/10.1210/jc.2005-2845.
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Abstract Context: The oncogenic RET/PTC tyrosine kinase causes papillary thyroid cancer (PTC). The use of inhibitors specific for RET/PTC may be useful for targeted therapy of PTC. Objective: The objective of the study was to evaluate the efficacies of the recently developed kinase inhibitors SU11248, SU5416, and SU6668 in inhibition of RET/PTC. Design: SU11248, SU5416, and SU6668 were synthesized, and their inhibitory potencies were evaluated using an in vitro RET/PTC kinase assay. The inhibitory effects of the compounds on RET/PTC were evaluated by quantifying the autophosphorylation of RET/PTC, signal transducer and activator of transcription (STAT)-3 activation, and the morphological reversal of RET/PTC-transformed cells. Results: An in vitro kinase assay revealed that SU5416, SU6668, and SU11248 inhibited phosphorylation of the synthetic tyrosine kinase substrate peptide E4Y by RET/PTC3 in a dose-dependent manner with IC50 of approximately 944 nm for SU5416, 562 nm for SU6668, and 224 nm for SU11248. Thus, SU11248 effectively inhibits the kinase activity of RET/PTC3. RET/PTC-mediated Y705 phosphorylation of STAT3 was inhibited by addition of SU11248, and the inhibitory effects of SU11248 on the tyrosine phosphorylation and transcriptional activation of STAT3 were very closely correlated with decreased autophosphorylation of RET/PTC. SU11248 caused a complete morphological reversion of transformed NIH-RET/PTC3 cells and inhibited the growth of TPC-1 cells that have an endogenous RET/PTC1. Conclusion: SU11248 is a highly effective tyrosine kinase inhibitor of the RET/PTC oncogenic kinase.
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Shen, Yang, Linyi Meng, Huajun Sun, Yizhun Zhu, and Hongrui Liu. "Cochinchina MomordicaSeed Suppresses Proliferation and Metastasis in Human Lung Cancer Cells by Regulating Multiple Molecular Targets." American Journal of Chinese Medicine 43, no. 01 (January 2015): 149–66. http://dx.doi.org/10.1142/s0192415x1550010x.
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Cochinchina Momordica Seed, which is the dried ripe seed of Momordica cochinchinensis (Lour.) Spreng, has been used as a mainly anticancer ingredient for many years in China. This study aims at investigating the roles of an ethanol-soluble extract of Cochinchina Momordica Seed (ECMS) in suppressing the proliferation and metastasis of human lung cancer cells, and further elucidating underlying molecular mechanisms. Our researches suggest that ECMS dose-dependently decreased the survival rates of A549 and H1299 cells, and inhibited the migration and invasion in A549 cells. ECMS-induced apoptosis was accompanied by up-regulation of p53, Bax and the down-regulation of Bcl-2, PI-3K/Akt signal pathway, and resulted in the dissipation of mitochondrial membrane potential (ΔΨm) and sequentially activated caspase-3 cascade. Pre-treated with specific inhibitors, LY294002 (PI-3K inhibitor) and BAY11-7082 (NF-κB inhibitor) could enhance the anti-proliferation effects of ECMS on A549 cells. Furthermore, ECMS could increase the level of E-cadherin and decrease of the level of STAT-3 and MMP-2, and scarcely affected the expression of VEGF, and resulted in the inhibition of migration and invasion. Pre-treated with specific inhibitors, WP1066 (STAT-3 inhibitor) and TIMP-2 (MMP-2 inhibitor) could enhance the inhibitory effects of ECMS on migration. In conclusion, the current data demonstrated ECMS inhibited the proliferation of A549 cells by inducing apoptosis, at least partly through the activation of p53 and inactivation of PI-3K/Akt signaling. STAT-3 and MMP-2 pathways may be partly involved in anti-metastasis activities of ECMS. Hence, ECMS might be a promising candidate for the therapy of the non-small cell lung cancer by regulating multiple molecular targets.
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SHEN, Xuening, Zhigang TIAN, Michael J. HOLTZMAN, and Bin GAO. "Cross-talk between interleukin 1β (IL-1β) and IL-6 signalling pathways: IL-1β selectively inhibits IL-6-activated signal transducer and activator of transcription factor 1 (STAT1) by a proteasome-dependent mechanism." Biochemical Journal 352, no. 3 (December 8, 2000): 913–19. http://dx.doi.org/10.1042/bj3520913.
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Interleukin 1β (IL-1β) suppresses the IL-6-dependent induction of type II acute-phase response genes, but the underlying mechanism for this suppression remains uncertain. Here we report that treatment of human hepatocullular carcinoma HepG2 cells with IL-1β inhibited the IL-6-dependent binding of signal transducer and activator of transcription factor (STAT)1, but not that of STAT3, to the high-affinity serum-inducible element (‘SIE’). Furthermore, IL-1β selectively down-regulated the IL-6-induced tyrosine phosphorylation of STAT1 without affecting the level of STAT1 or tyrosine phosphorylation of STAT3. Kinase assays in vitro indicated that the inhibition of STAT1 phosphorylation by IL-1β was not due to an upstream blockade of Janus kinase (JAK1 or JAK2) activation. However, pretreatment with the proteasome inhibitor MG132 under conditions that prevented the IL-1β-dependent activation of the nuclear factor NF-κB also blocked the inhibitory effect of IL-1β on IL-6-activated STAT1. In related experiments, the protein tyrosine phosphatase inhibitor Na3VO4 also antagonized the inhibitory effect of IL-1β on the activation of STAT1 by IL-6. Taken together, these findings indicate that, by using a proteasome-dependent mechanism, IL-1β concomitantly induces NF-κB activation and dephosphorylates IL-6-activated STAT1; the latter might partly account for the inhibition by IL-1β of the IL-6-dependent induction of type II acute-phase genes.
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Palmroth, M., K. Kuuliala, R. Peltomaa, A. Virtanen, A. Kuuliala, A. Kurttila, A. Kinnunen, M. Leirisalo-Repo, O. Silvennoinen, and P. Isomäki. "AB0250 TOFACITINIB SUPPRESSES SEVERAL JAK-STAT PATHWAYS IN RHEUMATOID ARTHRITIS AND BASELINE SIGNALING PROFILE ASSOCIATES WITH TREATMENT RESPONSE." Annals of the Rheumatic Diseases 80, Suppl 1 (May 19, 2021): 1150.2–1151. http://dx.doi.org/10.1136/annrheumdis-2021-eular.448.
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Background:Cytokines are important mediators of inflammation and tissue destruction in rheumatoid arthritis (RA) 1. Several cytokines involved in RA pathogenesis act through Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway 2. The effects of JAK-inhibitor tofacitinib on cytokine signaling in vitro are well established, while in vivo evidence in patients remains scarce.Objectives:To investigate in vivo in rheumatoid arthritis patients i) which JAK-STAT pathways are inhibited by tofacitinib and ii) if baseline signaling profile is associated with the treatment response.Methods:Sixteen patients with active RA, despite treatment with conventional synthetic disease-modifying antirheumatic drugs (csDMARDs), received tofacitinib 5 mg twice daily for three months. Levels of basal and cytokine-induced phosphorylated STATs and total STAT1 and STAT3 in peripheral blood monocytes, T cells and B cells were measured by flow cytometry. mRNA expression of JAKs, STATs and suppressors of cytokine signaling (SOCS) were measured from peripheral blood mononuclear cells (PBMCs) by quantitative PCR. Association of baseline signaling profile with treatment response (the change from baseline in disease activity score (DAS28)) was studied by calculating correlation coefficients.Results:Treatment with tofacitinib and csDMARDs decreased median DAS28 from 4.4 to 2.6 (p < 0.001). Tofacitinib significantly decreased cytokine-induced phosphorylation of all JAK-STAT pathways studied. Basal STAT1, STAT3, STAT4 and STAT5 phosphorylation in monocytes and/or T cells was downregulated by tofacitinib. No changes were observed in STAT1 and STAT3 protein levels, while gene expression of STAT3, STAT4, STAT5A, JAK1, JAK3 and all studied SOCSs was significantly suppressed. Baseline STAT phosphorylation levels in T cells and monocytes and SOCS3 expression in PBMCs correlated with treatment response.Conclusion:Tofacitinib suppresses multiple JAK-STAT pathways in RA patients in vivo. Baseline JAK-STAT signaling profile may be applicable as a prognostic marker for treatment response to tofacitinib.References:[1]McInnes, I. B., Buckley, C. D. & Isaacs, J. D. Cytokines in rheumatoid arthritis-shaping the immunological landscape. Nature Reviews Rheumatology vol. 12 63–68 (2016).[2]Schwartz, D. M., Bonelli, M., Gadina, M. & O’Shea, J. J. Type I/II cytokines, JAKs, and new strategies for treating autoimmune diseases. Nat. Rev. Rheumatol.12, 25–36 (2016).Acknowledgements:This study was supported by Pfizer Inc.Disclosure of Interests:Maaria Palmroth Consultant of: Pfizer and from 1/21 a part-time employee of MedEngine and consultant for Pfizer, Krista Kuuliala Grant/research support from: Pfizer, Ritva Peltomaa Speakers bureau: Boehringer Ingelmheim, Pfizer, Sanofi, Paid instructor for: Boehringer Ingelheim, Eli Lilly and Company, Janssen, Abbvie, UCB Pharma, Anniina Virtanen: None declared, Antti Kuuliala: None declared, Antti Kurttila: None declared, Anna Kinnunen: None declared, Marjatta Leirisalo-Repo: None declared, Olli Silvennoinen Speakers bureau: Pfizer, AbbVie, Pia Isomäki Speakers bureau: Abbvie, Eli Lilly and Company, Pfizer, Roche, Paid instructor for: Abbvie, Eli Lilly and Company, Pfizer, Roche, Grant/research support from: Pfizer
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Suzuki, Asuka, Toshikatsu Hanada, Keiichi Mitsuyama, Takafumi Yoshida, Shintaro Kamizono, Tomoaki Hoshino, Masato Kubo, et al. "Cis3/Socs3/Ssi3 Plays a Negative Regulatory Role in Stat3 Activation and Intestinal Inflammation." Journal of Experimental Medicine 193, no. 4 (February 12, 2001): 471–82. http://dx.doi.org/10.1084/jem.193.4.471.
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Immune and inflammatory systems are controlled by multiple cytokines, including interleukins (ILs) and interferons. These cytokines exert their biological functions through Janus tyrosine kinases and signal transducer and activator of transcription (STAT) transcription factors. We recently identified two intrinsic Janus kinase (JAK) inhibitors, JAK binding protein (JAB; also referred to as suppressor of cytokine signaling [SOCS1]/STAT-induced STAT inhibitor [SSI1]) and cytokine-inducible SH2 protein (CIS)3 (or SOCS3/SSI3), which play an essential role in the negative regulation of cytokine signaling. We have investigated the role of STATs and these JAK inhibitors in intestinal inflammation. Among STAT family members, STAT3 was most strongly tyrosine phosphorylated in human ulcerative colitis and Crohn's disease patients as well as in dextran sulfate sodium (DSS)-induced colitis in mice. Development of colitis as well as STAT3 activation was significantly reduced in IL-6–deficient mice treated with DSS, suggesting that STAT3 plays an important role in the perpetuation of colitis. CIS3, but not JAB, was highly expressed in the colon of DSS-treated mice as well as several T cell–dependent colitis models. To define the physiological role of CIS3 induction in colitis, we developed a JAB mutant (F59D-JAB) that overcame the inhibitory effect of both JAB and CIS3 and created transgenic mice. DSS induced stronger STAT3 activation and more severe colitis in F59D-JAB transgenic mice than in their wild-type littermates. These data suggest that hyperactivation of STAT3 results in severe colitis and that CIS3 plays a negative regulatory role in intestinal inflammation by downregulating STAT3 activity.
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Xu, FenLan, Liying Xu, Xiaoyan Xu, Zhenhua Huang, and Liang Su. "Dexmedetomidine Inhibited Proliferation and Invasion of Cervical Cancer Cells by Inhibiting the Janus Tyrosine Kinase/Signal Transducer and Activator of Transcription Signaling Pathway." Journal of Biomaterials and Tissue Engineering 11, no. 7 (July 1, 2021): 1293–304. http://dx.doi.org/10.1166/jbt.2021.2702.
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The role of anesthetics in the treatment of cancer has been reported, but the role of Dexmedetomidine (Dex) in the treatment of cervical cancer (CC) has not been reported.In this study, cell viability and proliferation were determined by MTT and cloning formation assay. The expression of proliferation-related proteins ki67 and PCNA was detected by western blot. Wound healing and transwell detected cell migration and invasion, and western blot detected the expression of migration and invasion related proteins MMP4 and MMP9, and epithelial-mesenchymal transformation (ETM)-related proteins N-cadherin, Snail, Vimentin and E-cadherin. Western blot also detected the expression of pathway related proteins p-JAK2, p-STAT1, p-STAT3, JAK2, STAT1 and STAT3. It showed that Dex inhibited the cell viability and proliferation of Hela and siHa and the expression of ki67 and PCNA were also inhibited. Dex inhibited the cell migration and invasion, and inhibited the expression of MMP4 and MMP9. In addition, Dex inhibited the expression of N-cadherin, Snail and Vimentin, and promoted the expression of E-cadherin. Dex inhibited the expression of p-JAK2, p-STAT1 and p-STAT3. After the addition of JAK/STAT signaling pathway agonist IL-6, the inhibition of Dex on proliferation, migration and invasion of CC cells was reversed. And the addition of JAK/STAT signaling pathway inhibitor AG490 could counteract the excitatory effect of IL-6 on the pathway, at which time the cell proliferation, invasion and migration were significantly increased. In conclusion, our study demonstrated that Dex inhibited proliferation, migration, and invasion of cells in CC by blocking the JAK/STAT signaling pathway.
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Kuusanmäki, Heikki, Hanna Rajala, Arjan van Adrichem, Muntasir Mamun Majumder, Emma I. Andersson, Krister Wennerberg, Satu Mustjoki, and Caroline A. Heckman. "Drug Sensitivity Profiling Identifies Drugs for Targeting Constitutively Active Mutant STAT3 and Mutant STAT5B Positive Malignancies." Blood 124, no. 21 (December 6, 2014): 1771. http://dx.doi.org/10.1182/blood.v124.21.1771.1771.
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Abstract Introduction: Constitutive hyperactivation of the STAT3 and STAT5B transcription factors is often observed in cancer. Lately, activating STAT3 mutations have been identified in hematological malignancies including large granular lymphocytic (LGL) leukemia (prevalence 40%), aplastic anemia (7%) and CD30+ T-cell lymphoma (17%). Furthermore, recent studies highlight the importance of STAT5B mutations in the pathogenesis and prognosis of T-cell malignancies such as T-cell prolymphocytic leukemia (36%), T-cell acute lymphoblastic leukemia (8%) and hepatosplenic T-cell lymphoma (33%). While STAT3 and STAT5B mutations lead to constitutive STAT3/STAT5B signaling, several other known gene mutations and mechanisms may also cause JAK/STAT-pathway activation. These findings indicate that inhibiting the JAK/STAT pathway with targeted drugs could be used as a treatment option. Here, we aimed to identify drugs that inhibit STAT3 or STAT5B function and determine if mutant STAT3/5B and wild type STAT3/5B cells respond differently to the tested drugs. In addition, we wished to ascertain if STAT3 inhibition is sufficient to induce apoptosis in patient derived LGL cells with constitutively active STAT3. Methods: High-throughput drug sensitivity testing was performed with a compound collection containing over 300 approved and investigational oncology drugs including many kinase inhibitors (such as those targeting JAK, SRC, VEGFR, mTOR, MEK, and CHK) and small molecule STAT3 inhibitors (Stattic, LLL12, Sta-21). All drugs were tested in 5-8 different concentrations over a 10,000-fold concentration range. Mutant STAT3 (Y640F) and mutant STAT5B (N642H) transformed Ba/F3 cells as well as HEK293 cells containing a STAT5 (pGL4.52[luc2P/STAT5 RE/Hygro]) or STAT3 specific luciferase reporter gene element (HEK-SIE) were used in the screens. In addition, drug sensitivities of five LGL leukemia patient samples were also assessed. Primary patient cells and the Ba/F3 cells were incubated in 384-well plates for three days with the drugs after which cell viability was measured with CellTiter-Glo. STAT3/5B induced luciferase activity in the HEK cells was analyzed after the cells were incubated for 6 or 24 hours with the drugs using the ONE-Glo luciferase assay system. Results: A significant decrease in luciferase activity was detected in STAT3 mutant Y640F, STAT5B mutant N642H and wild type STAT3 transfected HEK-SIE cells in the presence of PI3K/mTOR inhibitors such as PF-04691502 and INK128. In addition, PI3K/mTOR inhibitors significantly decreased the viability of mutant STAT3 and STAT5B transformed Ba/F3 cells compared to wild type cells. Interestingly, JAK inhibitors (e.g. ruxolitinib, gandotinib) did not inhibit mutant STAT3 activity in the HEK-SIE cells, whereas IL6-induced wild type STAT3 activity was completely blocked. A BET family inhibitor (JQ1+) and glucocorticoids (e.g. dexamethasone, methylprednisolone) showed specific and strong cytotoxicity to mutant STAT3 and STAT5B transformed Ba/F3 cells. Although JQ1+ inhibited luciferase activity of STAT5B N642H cells, no effect on the luciferase activity of STAT3 Y640F transfected HEK cells was detected, suggesting that JQ1+ may have a direct effect on mutant STAT5B function while the effect on mutant STAT3 transformed cells may be indirect. Cells from LGL leukemia patients showed high sensitivity against glucocorticoids, the histone deacetylase inhibitor quisinostat, JQ1+ and PF-04691502 when compared to healthy CD8+ T-cells. However, no increase in apoptosis was observed with JAK or other mTOR inhibitors. Conclusions: Our results suggest that JAK inhibitors lack efficacy in STAT3 mutated diseases. However, our ex vivo and in vitro drug screens highlight some other promising agents including PF-04691502 (PI3K/mTOR inhibitor) and JQ1+ (BET family inhibitor) that inhibited mutant STAT5B and STAT3 activity in the cell line models and were effective against primary LGL patient cells. Additional experiments are ongoing to determine how these drugs function to block STAT signaling and induce cell death. As the STAT3 and STAT5 pathways are activated in many other cancer types as well, the results may be applicable to a variety of different malignancies. Figure 1 Figure 1. Table 1. Drug sensitivity scores of the different cell line models and patient samples. DSS value range 0-50. (0 = no drug response with any conc., 50 = maximal drug response with every conc.) Disclosures Mustjoki: Bristol-Myers Squibb: Honoraria, Research Funding; Novartis: Honoraria, Research Funding.
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Koppikar, Priya, Omar Abdel-Wahab, Cyrus Hedvat, Sachie Marubayashi, Jay Patel, Aviva Goel, Nicole Kucine, et al. "Efficacy of the JAK2 inhibitor INCB16562 in a murine model of MPLW515L-induced thrombocytosis and myelofibrosis." Blood 115, no. 14 (April 8, 2010): 2919–27. http://dx.doi.org/10.1182/blood-2009-04-218842.
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Abstract The discovery of JAK2 and MPL mutations in patients with myeloproliferative neoplasms (MPNs) provided important insight into the genetic basis of these disorders and led to the development of JAK2 kinase inhibitors for MPN therapy. Although recent studies have shown that JAK2 kinase inhibitors demonstrate efficacy in a JAK2V617F murine bone marrow transplantation model, the effects of JAK2 inhibitors on MPLW515L-mediated myeloproliferation have not been investigated. In this report, we describe the in vitro and in vivo effects of INCB16562, a small-molecule JAK2 inhibitor. INCB16562 inhibited proliferation and signaling in cell lines transformed by JAK2 and MPL mutations. Compared with vehicle treatment, INCB16562 treatment improved survival, normalized white blood cell counts and platelet counts, and markedly reduced extramedullary hematopoeisis and bone marrow fibrosis. We observed inhibition of STAT3 and STAT5 phosphorylation in vivo consistent with potent inhibition of JAK-STAT signaling. These data suggest JAK2 inhibitor therapy may be of value in the treatment of JAK2V617F-negative MPNs. However, we did not observe a decrease in the size of the malignant clone in the bone marrow of treated mice at the end of therapy, which suggests that JAK2 inhibitor therapy, by itself, was not curative in this MPN model.
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Holloway, Gavan, Vi T. Dang, David A. Jans, and Barbara S. Coulson. "Rotavirus inhibits IFN-induced STAT nuclear translocation by a mechanism that acts after STAT binding to importin-α." Journal of General Virology 95, no. 8 (August 1, 2014): 1723–33. http://dx.doi.org/10.1099/vir.0.064063-0.
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The importance of innate immunity to rotaviruses is exemplified by the range of strategies evolved by rotaviruses to interfere with the IFN response. We showed previously that rotaviruses block gene expression induced by type I and II IFNs, through a mechanism allowing activation of signal transducer and activator of transcription (STAT) 1 and STAT2 but preventing their nuclear accumulation. This normally occurs through activated STAT1/2 dimerization, enabling an interaction with importin α5 that mediates transport into the nucleus. In rotavirus-infected cells, STAT1/2 inhibition may limit the antiviral actions of IFN produced early in infection. Here we further analysed the block to STAT1/2 nuclear accumulation, showing that activated STAT1 accumulates in the cytoplasm in rotavirus-infected cells. STAT1/2 nuclear accumulation was inhibited by rotavirus even in the presence of the nuclear export inhibitor Leptomycin B, demonstrating that enhanced nuclear export is not involved in STAT1/2 cytoplasmic retention. The ability to inhibit STAT nuclear translocation was completely conserved amongst the group A rotaviruses tested, including a divergent avian strain. Analysis of mutant rotaviruses indicated that residues after amino acid 47 of NSP1 are dispensable for STAT inhibition. Furthermore, expression of any of the 12 Rhesus monkey rotavirus proteins did not inhibit IFN-stimulated STAT1 nuclear translocation. Finally, co-immunoprecipitation experiments from transfected epithelial cells showed that STAT1/2 binds importin α5 normally following rotavirus infection. These findings demonstrate that rotavirus probably employs a novel strategy to inhibit IFN-induced STAT signalling, which acts after STAT activation and binding to the nuclear import machinery.
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Ansell, Stephen M., Deanna Grote, Sherine F. Elsawa, Mamta Gupta, Steven C. Ziesmer, Anne J. Novak, and Thomas E. Witzig. "Inhibition of the Jak/Stat Pathway Downregulates Immunoglobulin Production and Induces Cell Death in Waldenström Macroglobulinemia." Blood 114, no. 22 (November 20, 2009): 1691. http://dx.doi.org/10.1182/blood.v114.22.1691.1691.
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Abstract Abstract 1691 Poster Board I-717 Waldenström macroglobulinemia (WM) is a B-cell malignancy that is characterized by the production of a monoclonal IgM protein and a lymphoplasmacytic infiltrate in the bone marrow. The aberrant production of the monoclonal IgM can result in serum hyperviscosity that can cause significant morbidity in patients with this disease. In previous work, we have shown that IL-6 significantly upregulates IgM secretion by WM cells and that IL-6 secretion is regulated by CCL5 (Rantes). We have also shown that IL-6 mediated IgM secretion in WM requires phosphorylation of Stat1 and Stat3. Because IL-6 induced signaling involves the Jak/Stat pathway, we tested whether the use of a Jak/Stat inhibitor, TG101348, would result in down regulation of CCL5, IL-6 and IgM production and inhibit cell proliferation and viability in WM. First, we determined whether TG101348 could inhibit the production of CCL5 because other Jak inhibitors have been shown to inhibit cytokine production. Using the BCWM.1 cell line as well CD19+ malignant cells from bone marrow specimens from WM patients, we measured CCL5 by ELISA in the culture supernatant 24 hours after treatment with increasing concentrations of the inhibitor. We found that CCL5 secretion was decreased by 50% at a concentration of TG101348 of 250nM and was completely inhibited at 2μM. Next, we measured IL-6 production after treatment with TG101348. We had previously shown that stromal cells are the primary source of IL-6 and therefore used the stromal cell line HS-5 to measure IL-6 by ELISA after treatment with the inhibitor. Our previous work had also shown that IL-6 secretion was mediated by GLI (a member of the Hedgehog pathway) rather than the Jak/Stat pathway. Interestingly, we found that IL-6 secretion was inhibited in a dose dependent fashion but required higher doses for complete suppression (8μM). We then measured IgM production by malignant B-cells 24 hours after treatment with TG101348. Our previous work had shown that IL-6 mediated IgM secretion was dependent on the Jak/Stat pathway. We found that IgM production was inhibited by 50% at 500nM and completely suppressed at 2μM. Finally, we measured the effect of TG101348 on cell proliferation and survival. Using the BCWM.1 cell line, we found that cell proliferation as determined by tritiated thymidine uptake was inhibited in a dose dependent fashion with 50% inhibition at 1μM. Inhibition of cell viability as measured by Annexin V/propidium iodide staining, however, required higher concentrations and cell viability was inhibited with an IC50 of 8μM. These data confirm the role of Jak/Stat signaling in the CCL5-IL-6-IgM axis in WM. We found that TG101348 generally suppressed the signaling and growth of WM cells but that pathways that were known to be Jak/Stat dependent required significantly lower doses to be completely inhibited. These data provide a strong rationale for the use of inhibitors of this pathway, such as TG101348, in the treatment of patients with WM. Disclosures No relevant conflicts of interest to declare.
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Callus, Bernard A., and Bernard Mathey-Prevot. "Interleukin-3–Induced Activation of the JAK/STAT Pathway Is Prolonged by Proteasome Inhibitors." Blood 91, no. 9 (May 1, 1998): 3182–92. http://dx.doi.org/10.1182/blood.v91.9.3182.
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Abstract One facet of cytokine receptor signaling involves the activation of signal transducers and activators of transcription (STATs). STATs are rapidly activated via tyrosine phosphorylation by Janus kinase (JAK) family members and subsequently inactivated within a short period. We investigated the effect of proteasome inhibition on interleukin-3 (IL-3) activation of the JAK/STAT pathway following stimulation of Ba/F3 cells. Treatment of Ba/F3 cells with the proteasome inhibitor,N-acetyl-l-leucinyl-l-leucinyl-norleucinal (LLnL), led to stable tyrosine phosphorylation of the IL-3 receptor, beta common (βc), and STAT5 following stimulation. The effects of LLnL were not restricted to the JAK/STAT pathway, as Shc and mitogen-activated protein kinase (MAPK) phosphorylation were also prolonged in LLnL-treated cells. Further investigation showed these stable phosphorylation events were the result of prolonged activation of JAK2 and JAK1. These observations were confirmed using pharmacologic inhibitors. In the presence of LLnL, stable phosphorylation of STAT5 and βc was abrogated if the tyrosine kinase inhibitor, staurosporine, was added. The effect of staurosporine on STAT5 phosphorylation could be overcome if the phosphatase inhibitor, vanadate, was also added, suggesting phosphorylated STAT5 could be stabilized by phosphatase, but not by proteasome inhibition per se. These observations are consistent with the hypothesis that proteasome-mediated protein degradation can modulate the activity of the JAK/STAT pathway by regulating the deactivation of JAK.
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Callus, Bernard A., and Bernard Mathey-Prevot. "Interleukin-3–Induced Activation of the JAK/STAT Pathway Is Prolonged by Proteasome Inhibitors." Blood 91, no. 9 (May 1, 1998): 3182–92. http://dx.doi.org/10.1182/blood.v91.9.3182.3182_3182_3192.
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One facet of cytokine receptor signaling involves the activation of signal transducers and activators of transcription (STATs). STATs are rapidly activated via tyrosine phosphorylation by Janus kinase (JAK) family members and subsequently inactivated within a short period. We investigated the effect of proteasome inhibition on interleukin-3 (IL-3) activation of the JAK/STAT pathway following stimulation of Ba/F3 cells. Treatment of Ba/F3 cells with the proteasome inhibitor,N-acetyl-l-leucinyl-l-leucinyl-norleucinal (LLnL), led to stable tyrosine phosphorylation of the IL-3 receptor, beta common (βc), and STAT5 following stimulation. The effects of LLnL were not restricted to the JAK/STAT pathway, as Shc and mitogen-activated protein kinase (MAPK) phosphorylation were also prolonged in LLnL-treated cells. Further investigation showed these stable phosphorylation events were the result of prolonged activation of JAK2 and JAK1. These observations were confirmed using pharmacologic inhibitors. In the presence of LLnL, stable phosphorylation of STAT5 and βc was abrogated if the tyrosine kinase inhibitor, staurosporine, was added. The effect of staurosporine on STAT5 phosphorylation could be overcome if the phosphatase inhibitor, vanadate, was also added, suggesting phosphorylated STAT5 could be stabilized by phosphatase, but not by proteasome inhibition per se. These observations are consistent with the hypothesis that proteasome-mediated protein degradation can modulate the activity of the JAK/STAT pathway by regulating the deactivation of JAK.
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Croucher, Danielle C., Victor H. Jimenez-Zepeda, Zhi Hua Li, Ellen Wei, Brent DG Page, James Turkson, Patrick T. Gunning, and Suzanne Trudel. "The Potent STAT3/5 Inhibitor, BP-1-102 Demonstrates Significant Anti-Tumor Activity Against Waldenström Macroglobulinemia." Blood 118, no. 21 (November 18, 2011): 5101. http://dx.doi.org/10.1182/blood.v118.21.5101.5101.
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Abstract Abstract 5101 STAT3 is a cytoplasmic transcription factor, transiently activated in response to external stimuli such as growth factors and cytokines. As a transcription factor, STAT3 induces the expression of genes known to be involved in tumorigenesis, implicating STAT3 dysregulation in a number of hallmark oncogenic processes including tumor cell survival, proliferation, angiogenesis, metastasis, and drug resistance. Aberrant STAT3 signaling is prevalent in hematologic malignancies including Waldenstrom Macroglobulinemia (WM), a rare form of B cell non-Hodgkin lymphoma that is characterized by hyper-monoclonal IgM secretion in the peripheral blood. Despite the development of novel therapies and combinatorial treatment regimes, WM remains uniformly fatal, and as the limits of current chemotherapies have been reached, new approaches to treatment are urgently needed to improve patient outcome. Analysis of the gene and protein expression profiles of WM patients suggests that activation of STAT3 signaling plays a critical role in WM, providing rationale for the therapeutic use of STAT3 inhibitors. We have demonstrated pre-clinical efficacy of a novel, highly specific and potent small molecule STAT3/5 inhibitor, BP-1-102, in both hyper-IgM secreting B cell lymphoma cell lines (Mec-1 and RL) as well as two WM cell lines (MWCL-1 and BCWM-1). BP-1-102 directly targets STAT proteins by specifically blocking the SH2 domain that is a required for the phosphorylation, dimerization and nuclear localization of STAT3, ultimately resulting in inhibition of STAT3 transcriptional activation of target genes. We have shown that BP-1-102 directly interacts with STAT3's SH2 domain and is one of the most effective disruptors of STAT3 activity described to date. Treatment of cell lines with low μM doses of BP-1-102 induced dose-dependent decreases in constitutive and IL10-induced STAT3 phosphorylation (pSTAT3) as well as pSTAT3 nuclear localization. We further evaluated the potency of BP-1-102 against STAT1 and 5 compared to STAT3 using phosphor-flow cytometry to measure STAT phosphorylation status. BP-1-102 effectively inhibited GM-CSF induced STAT5 phosphorylation in AML2 cells at low dose concentrations (< 12.5uM) but only weakly inhibited IFNγ induced STAT1 phosphorylation in U937 leukemic cells at similar dose concentrations confirming the selectivity of BP-1-102 for STAT 3 and 5. Using a STAT3 dependent luciferase reporter construct, we confirmed repression of STAT3 transcriptional activity which correlated with a dose-dependent decrease in expression of STAT3 target genes (Mcl-1, Bcl-XL, Survivin and c-Myc). Inhibition of pSTAT3 resulted in decreased cell viability as assessed by MTT assay after 72 hours of in vitro exposure, with IC50 values ranging from 6uM to 10uM. In addition, treatment of cells with BP-1-102 resulted in caspase-dependent apoptosis which correlated with the activation of caspase-3 and PARP cleavage. Interestingly, co-culture of Mec-1 and RL with bone marrow stroma cells reduced the cytotoxicity of BP-1-102 suggesting stroma-conferred resistance, while MWCL-1 were equally sensitive to the cytotoxic effects of BP-1-102 regardless of either culture condition. Preliminary investigation suggests that the efflux system, used by cells to extrude toxic substances and linked to drug resistance in cancer, may be responsible for conferring stroma-mediate resistance to BP-1-102 in Mec-1 and RL cells. Finally, xenograft experiments to determine in vivo efficacy and safety are planned and will be presented. Collectively, these findings demonstrate a critical role for STAT3 signaling in WM pathology and provide the rationale for further development of STAT3 inhibitors for the treatment of WM. Disclosures: No relevant conflicts of interest to declare.
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Zoumpoulidou, Georgia, Marius C. Jones, Silvia Fernandez de Mattos, Julia M. Francis, Luca Fusi, Yun Soo Lee, Mark Christian, Rana Varshochi, Eric W. F. Lam, and Jan J. Brosens. "Convergence of Interferon-γ and Progesterone Signaling Pathways in Human Endometrium: Role of PIASy (Protein Inhibitor of Activated Signal Transducer and Activator of Transcription-y)." Molecular Endocrinology 18, no. 8 (August 1, 2004): 1988–99. http://dx.doi.org/10.1210/me.2003-0467.
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Abstract All cardinal events during the reproductive cycle, including ovulation, implantation, and menstruation, are characterized by a profound tissue remodeling and an associated local inflammatory response. The ovarian hormone progesterone is a key modulator of inflammatory signals in reproductive tissues, but the underlying mechanisms are not well understood. In this study, we report that differentiating human endometrial stromal cells (ESCs) acquire resistance to interferon-γ (IFNγ)-dependent signal transducers and activators of transcription (STAT) 1 signaling, although phosphorylation, nuclear translocation, and binding of STAT1 to DNA, are unaffected. These observations prompted an investigation into the role of nuclear repressors of STAT1 signaling. We demonstrate that protein inhibitor of activated STAT-y is complexed to the progesterone receptor (PR) in human ESCs and that its ability to repress STAT1 signaling is dependent upon activation of PR in response to hormone binding. Conversely, IFNγ and protein inhibitor of activated STAT-y synergistically inhibited PR-dependent transcription, demonstrating that the progesterone and IFNγ signaling pathways engage in reciprocal transcriptional antagonism in human endometrium.
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HUANG, Jau-Shyang, Jinn-Yuh GUH, Wen-Chun HUNG, Mei-Li YANG, Yung-Hsiung LAI, Hung-Chun CHEN, and Lea-Yea CHUANG. "Role of the Janus kinase (JAK)/signal transducters and activators of transcription (STAT) cascade in advanced glycation end-product-induced cellular mitogenesis in NRK-49F cells." Biochemical Journal 342, no. 1 (August 10, 1999): 231–38. http://dx.doi.org/10.1042/bj3420231.
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Advanced glycation end product (AGE) is important in the pathogenesis of diabetic nephropathy, which is characterized by cellular hypertrophy/hyperplasia leading to renal fibrosis. However, the signal transduction pathways of AGE remain poorly understood. The Janus kinase (JAK)/signal transducers and activators of transcription (STAT) pathway has been associated with cellular proliferation in some extra-renal cells. Because interstitial fibroblast proliferation might be important in renal fibrosis, we studied the role of the JAK/STAT pathway in NRK-49F (normal rat kidney fibroblast) cells cultured in AGE/BSA and non-glycated BSA. We showed that AGE dose-dependently (10-200 μg/ml) increased cellular mitogenesis in NRK-49F cells at 5 and 7 days. However, cellular mitogenesis was unaffected by the simultaneous presence of BSA. Regarding the JAK/STAT pathway, AGE (100 μg/ml) induced tyrosine phosphorylation of JAK2 (but not JAK1, JAK3 or TYK2) at 15-60 min; it also induced the tyrosine phosphorylation of STAT1 and STAT3 at 1-2 h and 0.5-4 h respectively. Being a transcription factor, AGE also increased the DNA-binding activities of STAT1 and STAT3 AG-490 (a specific JAK2 inhibitor) (5 μM) inhibited tyrosine phosphorylation of JAK2 and the DNA-binding activities of STAT1 and STAT3. The same results were obtained by using specific ‘decoy’ oligodeoxynucleotides (ODNs) that prevented STAT1 and STAT3 from binding to DNA. Meanwhile, the STAT1 or STAT3 decoy ODN and AG-490 were effective in reversing AGE-induced cellular mitogenesis. We concluded that the JAK2-STAT1/STAT3 signal transduction pathway is necessary for AGE-induced cellular mitogenesis in NRK-49F cells.
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Gorre, M., I. Jilani, H. Kantarjian, F. Giles, A. Hannah, and M. Albitar. "Novel Quantitative Flow Cytometry-Based Signaling Assays Reveal a Potential Role for HSP90 Inhibitors in the Treatment of JAK2 Mutant-Positive Diseases." Blood 106, no. 11 (November 16, 2005): 3526. http://dx.doi.org/10.1182/blood.v106.11.3526.3526.
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Abstract The V617F mutation in the JAK2 tyrosine kinase, recently described in a majority of patients with myeloproliferative disorders (MPDs), confers growth factor independence in vitro and oncogenicity in mice. Therefore, targeted inhibition of mutant JAK2 kinase activity may be an effective strategy for treatment of MPD patients with this mutation. The ability to measure the activation status of JAK2 in patient samples will thus be of substantial value for monitoring therapeutic efficacy. We have developed quantitative flow cytometry-based assays for rapid and reproducible measurement of intracellular total and phosphorylated proteins of the canonical JAK/STAT pathway, as well as heat shock proteins (HSPs). In this study we examined the ability of these assays to detect altered levels of total and phosphorylated JAK/STAT signaling pathway components and HSP in a cell line (HEL) that is homozygous for the V617F JAK2 mutant. HEL cell cultures were incubated with 17AAG, a geldanamycin analog with clinical utility in a broad range of diseases. 17AAG exerts its inhibitory effect by binding to heat shock protein 90 (HSP90), preventing its chaperone association with client oncoproteins. AKT is among these client proteins and a component of the JAK/STAT pathway, representing a potential therapeutic target. 17AAG exposure reduced total AKT protein levels by 42%. 17AAG also inhibited mutant JAK2 activity by 66% and had a smaller effect (17%) on total JAK2 levels, suggesting that mutant JAK2 activation may rely on HSP90, either directly or through dependence on other client proteins. Exposure to 17AAG also reduced levels of P-STAT5 (50%) and, to a lesser extent, total STAT5 (27%). 17AAG-treated cells showed a 55% reduction in HSP90 levels and a 14% increase in HSP70 protein levels. JAK Inhibitor I (Calbiochem), a potent pan-JAK Inhibitor that blocks JAK1, JAK2, and JAK3 activity, caused reductions in P-JAK2 and P-STAT5 levels (29% and 26% decreases, respectively). However, the combining of JAK Inhibitor I with 17AAG did not result in an enhanced effect beyond what was observed with 17AAG treatment alone. Similar results were seen with AG490, a potent and selective JAK2 inhibitor. 17AAG caused a 40% decrease in viable cells after 18 hrs of treatment, compared with a 35% reduction for the pan-JAK inhibitor and a 20% decrease for AG490. Combining 17AAG with the pan-JAK inhibitor or AG490 caused only minor enhancement of these cytotoxic effects (46% and 41% reduction in cell viability, respectively). Our data support the potential utility of HSP90 inhibitors such as 17AAG in the development of small-molecule therapy for mutant JAK2 kinase-positive MPD. These results also show that flow cytometry-based assays for JAK/STAT signaling components and HSPs can be used to quantitatively monitor drug efficacy at the protein level in intact cells. These tests are likely to have broad clinical utility given the spectrum of diseases in which a pathogenic role for mutant JAK2 kinase is implicated.
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Ma, Frank Y., Greg M. Anderson, Travis D. Gunn, Vincent Goffin, David R. Grattan, and Stephen J. Bunn. "Prolactin Specifically Activates Signal Transducer and Activator of Transcription 5b in Neuroendocrine Dopaminergic Neurons." Endocrinology 146, no. 12 (December 1, 2005): 5112–19. http://dx.doi.org/10.1210/en.2005-0770.
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The hypothalamic neuroendocrine dopaminergic (NEDA) neurons are crucial in regulating prolactin secretion from the anterior pituitary. Rising prolactin concentrations stimulate these neurons to secrete dopamine, which acts via the pituitary portal vasculature to inhibit additional prolactin release. Prolactin is known to activate Janus kinase (JAK)-signal transducer and activator of transcription (STAT) signaling pathways in other cell types, including neurons. The possible role of JAK-STAT signaling in NEDA neurons has therefore been examined in this study using fetal rat mediobasal hypothalamic cell cultures and an adult rat in vivo preparation. Cultured cells expressing the dopamine synthesizing enzyme tyrosine hydroxylase (TH) responded to prolactin with a time-dependent increase in phospho-STAT5, but not phospho-STAT1 or phospho-STAT3, nuclear labeling. This response was inhibited by the prolactin receptor antagonist Δ1–9-G129R-human prolactin and the JAK inhibitor AG490, but was unaffected by selected serine/threonine kinase inhibitors (H89, KN-93, bisindolymaleimide, or PD98059). Antibodies selective for STAT5a or STAT5b indicated that the response was restricted to STAT5b, with the number of TH cells displaying STAT5b nuclear immunoreactivity rising from less than 10% under basal conditions to approximately 70% after prolactin stimulation. STAT5a nuclear labeling remained unchanged at 6–10% of TH-positive cells. STAT5b selectivity was confirmed in vivo, where the injection of prolactin into bromocriptine-treated rats stimulated a time-dependent increase in STAT5b, but not STAT5a, nuclear staining in the TH-expressing neurons in the arcuate nucleus. These results extend our previous findings with STAT5b-deficient mice and strongly suggest that in NEDA neurons, prolactin signaling via the JAK/STAT pathway is mediated exclusively by STAT5b.
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Kim, Lee, Song, Park, Gadhe, Choi, Lee, Pae, Kim, and Ye. "Development of Oxadiazole-Based ODZ10117 as a Small-Molecule Inhibitor of STAT3 for Targeted Cancer Therapy." Journal of Clinical Medicine 8, no. 11 (November 2, 2019): 1847. http://dx.doi.org/10.3390/jcm8111847.
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Persistently activated STAT3 is a promising target for a new class of anticancer drug development and cancer therapy, as it is associated with tumor initiation, progression, malignancy, drug resistance, cancer stem cell properties, and recurrence. Here, we discovered 3-(2,4-dichloro-phenoxymethyl)-5-trichloromethyl-[1,2,4]oxadiazole (ODZ10117) as a small-molecule inhibitor of STAT3 to be used in STAT3-targeted cancer therapy. ODZ10117 targeted the SH2 domain of STAT3 regardless of other STAT family proteins and upstream regulators of STAT3, leading to inhibition of the tyrosine phosphorylation, dimerization, nuclear translocation, and transcriptional activity of STAT3. The inhibitory effect of ODZ10117 on STAT3 was stronger than the known STAT3 inhibitors such as S3I-201, STA-21, and nifuroxazide. ODZ10117 suppressed the migration and invasion, induced apoptosis, reduced tumor growth and lung metastasis, and extended the survival rate in both in vitro and in vivo models of breast cancer. Overall, we demonstrated that ODZ10117 is a novel STAT3 inhibitor and may be a promising agent for the development of anticancer drugs.
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Thomas, Sally J., Katherine Fisher, Stephen Brown, John A. Snowden, Sarah Danson, and Martin Zeidler. "Methotrexate Is a Suppressor of JAK/STAT Pathway Activation Which Inhibits JAK2V617F Induced Signalling." Blood 124, no. 21 (December 6, 2014): 4577. http://dx.doi.org/10.1182/blood.v124.21.4577.4577.
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Abstract The classical myeloproliferative neoplasms (MPNs) are a group of disorders characterised by activation of the JAK/STAT signalling pathway. A large proportion of patients with MPNs have an acquired mutation, JAK2V617F, which causes constitutive kinase activity. Patients with wild-type JAK2 show gene expression patterns characteristic of JAK/STAT activation, and the majority have mutations in other genes associated with increased pathway activation. Inhibition of JAK/STAT activation represents an attractive therapeutic approach for these disorders. In myelofibrosis, treatment with a JAK inhibitor reduces spleen volume, improves quality of life and prolongs life expectancy, whereas there is evidence that other therapies are no better than placebo. This study aimed to find new treatments for MPNs by identifying compounds that suppress JAK/STAT activation. We screened a small-molecule library consisting of FDA approved drugs, cytotoxic drugs, agrochemicals, and pure natural products to identify modulators of STAT-responsive transcription in the low complexity Drosophila model. We independently identified methotrexate (z-score -8.72) and the chemically similar aminopterin (z-score -8.2) as strong inhibitors of Drosophila JAK/STAT activation. The suppression of transcriptional reporter activity was dose dependent and was observed following activation of the pathway with the Drosophila JAK/STAT ligand Upd and by the gain of function Drosophila JAK HopTuml. To examine whether these results translated to the more complex JAK/STAT signalling pathway of humans we examined the effect of methotrexate in the Hodgkin Lymphoma cell line HDLM-2, which shows constitutive phosphorylation of several JAK/STAT family members. Immunoblotting for phosphorylated pathway components showed that methotrexate produced a dose dependent reduction in levels of tyrosine phosphorylated STAT5 (Y694), without affecting total STAT5 levels. Methotrexate did not affect phosphorylated proteins in other signalling pathways, including pAKT, p c-Jun or pMAPK. To examine the potential of methotrexate as a treatment for MPNs, we used the HEL cell line, which is homozygous for JAK2V617F and shows STAT5 phosphorylation that is dependent on JAK2 activity. Immunoblotting showed that methotrexate produced a dose dependent reduction in levels of pSTAT5. Significant suppression of STAT5 phosphorylation was seen following treatment with methotrexate at concentrations equivalent to those measured in the serum of patients taking low dose oral methotrexate (0.4 – 0.8 mM, p<0.001, one-way ANOVA with Dunnett’s multiple comparisons test). Suppression of STAT5 phosphorylation persisted in the presence of folinic acid at concentrations used to prevent methotrexate toxicity, suggesting that the effect on JAK/STAT signalling is not mediated by impairment of folate metabolism. Methotrexate did not completely prevent signalling via the JAK/STAT pathway, as methotrexate-treated cells were still able to phosphorylate STAT5 following stimulation with the EpoR/JAK2/STAT5 pathway ligand erythropoietin. The reduction in STAT5 phosphorylation produced by treatment with methotrexate was comparable to that produced by the JAK1/JAK2 inhibitor ruxolitinib, although ruxolitinib was a more potent inhibitor of pathway activation. Given that methotrexate is used to treat inflammatory disorders and activation of JAK/STAT signalling is involved in the inflammatory response we examined the effect of methotrexate on rheumatoid arthritis fibroblast-like synoviocytes. Methotrexate also reduced constitutive STAT phosphorylation in these primary cells. Our results suggest that low-dose oral methotrexate should be investigated as a potential treatment for patients with MPNs. We suggest that methotrexate may suppress pathological over-activation of the JAK/STAT pathway sufficiently to control disease and bring about the benefits demonstrated with specific JAK inhibitors, without preventing physiological activation required for haematopoiesis and response to infection. Methotrexate is inexpensive and has advantages as a potential treatment as its safety and adverse effects are already well understood. Furthermore, our results suggest that suppression of JAK/STAT pathway activation may be a mechanism through which methotrexate exerts anti-inflammatory and immunosuppressive effects. Disclosures Off Label Use: Methotrexate is widely used as a chemotherapy drug and to treat inflammatory disorders. This work includes a discussion of the potential use of methotrexate to treat myeloproliferative neoplasms, based on experiments in cell lines.
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Banes, Amy K. L., Seán M. Shaw, Amany Tawfik, Bela P. Patel, Safia Ogbi, David Fulton, and Mario B. Marrero. "Activation of the JAK/STAT pathway in vascular smooth muscle by serotonin." American Journal of Physiology-Cell Physiology 288, no. 4 (April 2005): C805—C812. http://dx.doi.org/10.1152/ajpcell.00385.2004.
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Serotonin (5-hydroxytryptamine, 5-HT) is a vasoconstrictor and mitogen whose levels are elevated in diabetes. Previous studies have shown the presence of 5-HT2A, 5-HT2B, and 5-HT1B receptors in vascular smooth muscle cells (VSMCs). There are currently no data regarding 5-HT2B and 5-HT1B receptor activation of the JAK/STAT pathway in VSMCs and resultant potential alterations in 5-HT signaling in diabetes. Therefore, we tested the hypothesis that 5-HT differentially activates the JAK/STAT pathway in VSMCs under conditions of normal (5 mM) and high (25 mM) glucose. Treatment of rat VSMCs with 5-HT (10−6 M) resulted in time-dependent activation (∼2-fold) of JAK2, JAK1, and STAT1, but not STAT3 (maximal at 5 min, returned to baseline by 30 min). The 5-HT2B receptor agonist BW723C86 and the 5-HT1B receptor agonist CGS12066A (10−9–10−5 M, 5-min stimulation) did not activate the JAK/STAT pathway. Treatment with the 5-HT2A receptor antagonist ketanserin (10 nM) inhibited JAK2 activation by 5-HT. Treatment of streptozotocin-induced diabetic rats with ketanserin (5 mg·kg−1·day−1) reduced activation of JAK2 and STAT1 but not STAT3 in endothelium-denuded thoracic aorta in vivo. 5-HT (10−6 M) treatment resulted in increased cell proliferation and increased DNA synthesis, which were inhibited by the JAK2 inhibitor AG490. Further studies with apocynin, diphenyleneiodonium chloride, catalase, and virally transfected superoxide dismutase had no effect at either glucose concentration on activation of the JAK/STAT pathway by 5-HT. Therefore, we conclude that 5-HT activates JAK2, JAK1, and STAT1 via the 5-HT2A receptors in a reactive oxygen species-independent manner under both normal and high glucose conditions.
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Ishida-Takahashi, Ryoko, Shigeo Uotani, Takahiro Abe, Mikako Degawa-Yamauchi, Tetsuya Fukushima, Naruhiro Fujita, Hiroyuki Sakamaki, Hironori Yamasaki, Yoshihiko Yamaguchi, and Katsumi Eguchi. "Rapid Inhibition of Leptin Signaling by Glucocorticoidsin Vitroandin Vivo." Journal of Biological Chemistry 279, no. 19 (March 1, 2004): 19658–64. http://dx.doi.org/10.1074/jbc.m310864200.
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Elevated secretion of glucocorticoids (GCs) or hypersensitivity to GCs has a permissive effect on the development of obesity and leads to abnormalities of body fat distribution. Recent studies demonstrated GCs act as antagonists of leptin in rodents. However, little is known about the interaction between GCs and leptin signaling. In the present study, we investigated the effects of GCs on leptin actionin vitroandin vivo. GCs rapidly inhibited the leptin-induced STAT3 phosphorylation in a dose- and time-dependent manner, as assayed by Western blotting using anti-phosphospecific-STAT3 in human hepatoma cell lines (Huh7) transiently expressing long form leptin receptor. GCs also inhibited the leptin-induced JAK2 tyrosine phosphorylation but unaltered the specific binding of125I-leptin to the cells. Parallel experiments, however, demonstrated that the inhibitory effects of GCs were not observed in either IL-6- or LIF-induced STAT3 phosphorylation. Furthermore, we examined the feeding behavior and hypothalamic leptin signaling following intracerebroventricular (icv) infusion of GCs prior to icv leptin infusion in Sprague-Dawley rats. The food intake after 24 h of icv leptin injection increased 3-fold in GCs-treated animals. In addition, central infusion of GCs resulted in a marked reduction of hypothalamic STAT3 phosphorylation in response to icv infusion of leptin. To clarify the molecular mechanism by which GCs rapidly reduce leptin-induced JAK/STAT signaling, we examined the intracellular signal transduction pathway potentially mediated by GCs. PD98059, a specific MEK inhibitor, blocked the inhibitory effects of GCs on leptin-induced JAK/STAT activation in Huh7 cells. These results suggest GCs antagonize leptin action by a rapid inhibition of the leptin-induced JAK/STAT pathway partly via MAPK cascade.
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Fiskus, Warren, Rekha Rao Manepalli, Ramesh Balusu, and Kapil N. Bhalla. "Synergistic Activity of Combinations of JAK2 Kinase Inhibitor with PI3K/mTOR, MEK or PIM Kinase Inhibitor Against Human Myeloproliferative Neoplasm Cells Expressing JAK2V617F." Blood 116, no. 21 (November 19, 2010): 798. http://dx.doi.org/10.1182/blood.v116.21.798.798.
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Abstract Abstract 798 The mutant JAK2-V617F tyrosine kinase (TK) is present in the majority of patients with BCR-ABL negative myeloproliferative neoplasms (MPNs). JAK2-V617F activates downstream signaling through the STAT, RAS/MAPK and PI3/AKT pathways, conferring proliferative and survival advantages in the MPN hematopoietic progenitor cells (HPCs). We have previously reported that pan-histone deacetylase (HDAC) inhibitors e.g. panobinostat (PS) (Novartis Pharmaceuticals), depleted mRNA expression of JAK2-V617F, and disrupted the chaperone association of with hsp90 with JAK2-V617F, thereby promoting the degradation of JAK2-V617F by the proteasome. This led to attenuation of the levels and downstream transcriptional activity of STAT3 and STAT5, resulting in growth arrest and apoptosis of MPN HPCs. Additionally, co-treatment with PS and a JAK2 kinase inhibitor, TG101209, further depleted JAK/STAT signaling and synergistically induced apoptosis of JAK2-V617F expressing HEL92.1.7 and Ba/F3-JAK2V617F cells, as well as exerted greater lethality against primary CD34+CD38-Lin- MPN versus normal CD34+ HPCs. In the present studies, we determined the cytotoxic effects of inhibiting JAK2-STAT3/5 in conjunction with pharmacologic targeting of the collateral, pro-growth and pro-survival signaling through PI3K/AKT, RAF-MEK or PIM1 kinases in MPN cells. For this, the cytotoxic effects of co-treatment with TG101209 and the MEK inhibitor (AZD6244, AstraZenaca), dual PI3K/mTOR inhibitor (BEZ235, Novartis) or the PIM1 kinase inhibitor (SGI-1776, SuperGen) were evaluated in HEL92.1.7, Ba/F3-JAK2V617 and primary human MPN cells. Treatment with BEZ235 dose-dependently attenuated the levels of p-JAK2, p-STAT5, p-STAT3, p-AKT, p-ERK1/2 and p-4EBP1. Co-treatment with BEZ235 and TG101209 was synergistically lethal against the cultured MPN and primary CD34+ MF-MPN cells (combination indices < 1.0). Co-treatment with AZD6244 and TG101209 also induced synergistic apoptosis of cultured MPN cells (combination indices of < 1.0). This was associated with greater attenuation of the levels of p-AKT and p-ERK1/2. PIM1 is a cytoplasmic serine/threonine kinase that serves as a downstream effector of several cytokine signaling pathways promoting cell survival and proliferation. PIM1 collaborates in Myc-induced transformation and known to phosphorylate 4EBP1 and eIF4B, thereby promoting protein translation. Co-treatment with TG101209 and the PIM1 kinase inhibitor, SGI-1776 also induced synergistic apoptosis of HEL92.1.7 cells and Ba/F3-JAK2V617F cells (combination indices < 1.0) but not of Ba/F3-hEpoR cells. PIM kinase mediates PRAS40 phosphorylation and induces mTORC1 activity in phosphorylating 4EBP1. Consistent with this, co-treatment with SGI-1776 and TG-101209 inhibited p-PRAS40 and p-4EBP1 levels in cultured MPN but not in normal progenitor cells. These findings demonstrate for the first time that combined treatment with a MEK inhibitor, PIM1 kinase inhibitor or dual PI3K/mTOR inhibitor enhances the anti-JAK2-V617F activity of TG101209 in cultured and primary human MPN cells. Our findings support the rationale to determine the in vivo activity of TG101209 in combination with inhibitors of MEK, PIM1 or PI3K/mTOR kinase against human MPN cells. Disclosures: No relevant conflicts of interest to declare.
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Piairo, Paulina, Rute S. Moura, Maria João Baptista, Jorge Correia-Pinto, and Cristina Nogueira-Silva. "STATs in Lung Development: Distinct Early and Late Expression, Growth Modulation and Signaling Dysregulation in Congenital Diaphragmatic Hernia." Cellular Physiology and Biochemistry 45, no. 1 (December 22, 2017): 1–14. http://dx.doi.org/10.1159/000486218.
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Background: Congenital diaphragmatic hernia (CDH) is a life-threatening developmental anomaly, intrinsically combining severe pulmonary hypoplasia and hypertension. During development, signal transducers and activators of transcription (STAT) are utilized to elicit cell growth, differentiation, and survival. Methods: We used the nitrofen-induced CDH rat model. At selected gestational time points, lungs were divided into two experimental groups, i.e., control or CDH. We performed immunohistochemistry and western blotting analysis to investigate the developmental expression profile of the complete family of STATs (STAT1-6), plus specific STATs activation (p-STAT3, p-STAT6) and regulation by SOCS (SOCS3) in normal lungs against those of diseased lungs. The normal fetal lung explants were treated with piceatannol (STAT3 inhibitor) in vitro followed by morphometrical analysis. Results: Molecular profiling of STATs during the lung development revealed distinct early and late expression signatures. Experimental CDH altered the STATs expression, activation, and regulation in the fetal lungs. In particular, STAT3 and STAT6 were persistently over-expressed and early over-activated. Piceatannol treatment dose-dependently stimulated the fetal lung growth. Conclusion: These findings suggest that STATs play an important role during normal fetal lung development and CDH pathogenesis. Moreover, functionally targeting STAT signaling modulates fetal lung growth, which highlights that STAT3 and STAT6 signaling might be promising therapeutic targets in reducing or preventing pulmonary hypoplasia in CDH.
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Rosengren, Sanna, Maripat Corr, Gary S. Firestein, and David L. Boyle. "The JAK inhibitor CP-690,550 (tofacitinib) inhibits TNF-induced chemokine expression in fibroblast-like synoviocytes: autocrine role of type I interferon." Annals of the Rheumatic Diseases 71, no. 3 (November 25, 2011): 440–47. http://dx.doi.org/10.1136/ard.2011.150284.
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ObjectivesThe objective of this study was to investigate the effect of the novel Janus kinase inhibitor CP-690,550 in fibroblast-like synoviocytes (FLSs) from patients with rheumatoid arthritis (RA).MethodsRA FLSs were isolated from tissue obtained by arthroplasty, cultured and serum-starved 48 h prior to stimulation. Messenger RNA and protein levels were determined by quantitative PCR and ELISA or multiplex bead assay, respectively. Phosphorylation of STAT (signal transducers and activators of transcription) proteins was determined by western blot.ResultsInterleukin-6-induced phosphorylation of STAT1 and STAT3 was inhibited by CP-690,550 with IC50 values of 23 and 77 nM, respectively. Unexpectedly, although tumour necrosis factor (TNF) did not induce immediate phosphorylation of either STAT, CP-690,550 inhibited TNF-induced expression of several chemokines (IP-10, RANTES and MCP1) at the messenger RNA and protein levels. Chemokine expression was inhibited by cycloheximide, implying a need for de novo protein synthesis, and cycloheximide abolished the effect of CP-690,550 (tofacitinib). TNF induced early interferon (IFN) β expression and STAT1 phosphorylation beginning at 3 h, which was blocked by CP-690,550. The dependence of TNF-induced chemokine expression on type I IFN was confirmed in FLSs from mice lacking type I IFN receptors (IFNARs) and in RA FLSs using an IFNAR blocking antibody.ConclusionsThe Janus kinase/STAT pathway in FLS is indirectly activated by TNF through autocrine expression of type I IFN, resulting in IFNAR engagement and production of T cell chemokines. These findings illuminate a novel role of CP-690,550 in the treatment of RA: the reduction of chemokine synthesis by FLS, thereby limiting recruitment of T cells and other infiltrating leucocytes.
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Dennis, Robyn M., Brandon Ballard, David John Tweardy, and Karen Rabin. "A Small Molecule Stat Inhibitor Blocks Stat3 and Stat5 Phosphorylation and Demonstrates Cytotoxicity In Acute Lymphoblastic Leukemia." Blood 116, no. 21 (November 19, 2010): 2904. http://dx.doi.org/10.1182/blood.v116.21.2904.2904.
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Abstract Abstract 2904 Survival has improved dramatically in acute lymphoblastic leukemia (ALL), but further gains are unlikely using conventional chemotherapy alone. Several recently discovered, novel cytogenetic lesions with adverse prognostic impact, JAK2 activating mutations and CRLF2 rearrangements, occur in up to 15% of adult and pediatric ALL. These lesions are associated with activation of Jak2 and Stat5, and hold promise as targets for novel therapies affecting these signaling pathways. We performed in vitro testing of a novel small molecule Stat inhibitor, C188-9, in B-lineage ALL cell lines and patient samples with and without JAK2/CRLF2 alterations. C188-9 treatment for one hour at 10 μM inhibited Stat3 and Stat5 phosphorylation in ALL cell lines with JAK2 and CRLF2 alterations, but not in cell lines with wild-type JAK2 and CRLF2, as measured by phospho-flow cytometry (Fig. 1A). Only the cell lines with JAK2 and CRLF2 alterations demonstrated basal Stat5 phosphorylation on Western blot analysis, and this was inhibited by C188-9 treatment (Fig. 1B). C188-9 demonstrated cytotoxicity in ALL cell lines regardless of JAK2/CRLF2 status, with IC50s in the low micromolar concentration range (Fig. 1C). While C188-9 is undergoing investigation currently as a potent inhibitor of Stat3 in acute myeloid leukemia (AML), it also merits further investigation as an agent with Stat5 inhibitory activity and cytotoxicity in ALL. Figure 1. Effects of C188-9 in ALL cell lines. A. Stat3 and Stat5 phosphorylation were determined by flow cytometry in the ALL cell lines MHH-CALL-4 (JAK2/CRLF2 mutated) and Reh (JAK2/CRLF2 wild-type). In each condition, cells were incubated in serum-free media for one hour, followed by incubation with C188-9 or vehicle for one hour, stimulation with vehicle or pervanadate 125 mM for 15 minutes, fixation, permeabilization, phospho-antibody staining for phospho-Stat3 and phospho-Stat5, and flow cytometric analysis. B. Western blot for phospho-Stat5 in K562 cell line (positive control); MHHCALL-4 treated for one hour with C188-9 at 0, 5, or 10 uM; and RS4;11 (JAK2/CRLF2 wild-type ALL cell line). C. IC50 determination by ATP assay for C188-9 in the ALL cell lines MHH-CALL-4 and RS4;11. Each experiment was performed in triplicate. Figure 1. Effects of C188-9 in ALL cell lines. A. Stat3 and Stat5 phosphorylation were determined by flow cytometry in the ALL cell lines MHH-CALL-4 (JAK2/CRLF2 mutated) and Reh (JAK2/CRLF2 wild-type). In each condition, cells were incubated in serum-free media for one hour, followed by incubation with C188-9 or vehicle for one hour, stimulation with vehicle or pervanadate 125 mM for 15 minutes, fixation, permeabilization, phospho-antibody staining for phospho-Stat3 and phospho-Stat5, and flow cytometric analysis. B. Western blot for phospho-Stat5 in K562 cell line (positive control); MHHCALL-4 treated for one hour with C188-9 at 0, 5, or 10 uM; and RS4;11 (JAK2/CRLF2 wild-type ALL cell line). C. IC50 determination by ATP assay for C188-9 in the ALL cell lines MHH-CALL-4 and RS4;11. Each experiment was performed in triplicate. Disclosures: No relevant conflicts of interest to declare.
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Severin, Frezzato, Visentin, Martini, Trimarco, Carraro, Tibaldi, et al. "In Chronic Lymphocytic Leukemia the JAK2/STAT3 Pathway Is Constitutively Activated and Its Inhibition Leads to CLL Cell Death Unaffected by the Protective Bone Marrow Microenvironment." Cancers 11, no. 12 (December 4, 2019): 1939. http://dx.doi.org/10.3390/cancers11121939.
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The bone marrow microenvironment promotes proliferation and drug resistance in chronic lymphocytic leukemia (CLL). Although ibrutinib is active in CLL, it is rarely able to clear leukemic cells protected by bone marrow mesenchymal stromal cells (BMSCs) within the marrow niche. We investigated the modulation of JAK2/STAT3 pathway in CLL by BMSCs and its targeting with AG490 (JAK2 inhibitor) or Stattic (STAT3 inhibitor). B cells collected from controls and CLL patients, were treated with medium alone, ibrutinib, JAK/Signal Transducer and Activator of Transcription (STAT) inhibitors, or both drugs, in the presence of absence of BMSCs. JAK2/STAT3 axis was evaluated by western blotting, flow cytometry, and confocal microscopy. We demonstrated that STAT3 was phosphorylated in Tyr705 in the majority of CLL patients at basal condition, and increased following co-cultures with BMSCs or IL-6. Treatment with AG490, but not Stattic, caused STAT3 and Lyn dephosphorylation, through re-activation of SHP-1, and triggered CLL apoptosis even when leukemic cells were cultured on BMSC layers. Moreover, while BMSCs hamper ibrutinib activity, the combination of ibrutinib+JAK/STAT inhibitors increase ibrutinib-mediated leukemic cell death, bypassing the pro-survival stimuli derived from BMSCs. We herein provide evidence that JAK2/STAT3 signaling might play a key role in the regulation of CLL-BMSC interactions and its inhibition enhances ibrutinib, counteracting the bone marrow niche.
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Bagby, Grover, Winifred Keeble, Tara Koretsky, Dylan Zodrow, Richard Jove, Laura Hays, and Hanqian Carlson. "Oxidative Stress Induces Binding of FANCD2 to STAT5 and Facilitates STAT5-Dependent Survival Signals." Blood 104, no. 11 (November 16, 2004): 33. http://dx.doi.org/10.1182/blood.v104.11.33.33.
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Abstract Fanconi anemia (FA) cells are hypersensitive to oxidative stress and exhibit aberrant STAT activation responses to defined extracellular proteins but whether these abnormalities are linked is unclear. Because oxidative stress is known to induce STAT activation, we hypothesized that proper STAT signaling responses in normal cells exposed to H2O2 require intact FA proteins. In fact, we found that FA-C, FA-G, and FA-D2 cells (fibroblasts) showed a significant increase in apoptosis after H2O2-exposure compared to retrovirally-complemented cells. H2O2 induced higher phospho-STAT5 (P-STAT5) expression in complemented cells than in mutant cells. Conversely, mutant cells expressed higher levels of P-STAT3 in both the ground state and after H2O2-induction than complemented cells. Aberrant STAT activation in FA mutant cells was shown to be both nucleus- and JAK2 kinase-dependent. Only low levels of STAT3 and STAT5 were induced in both mutant and complemented cytoplasts and AG490 (a Jak2 inhibitor) significantly suppressed H2O2-induced STAT5 responses. Seeking a direct role of FANCD2 in regulating proper STAT activation responses to H2O2, we carried out immunoprecipitation experiments (with an antibody to the N-terminal fragment of FANCD2) using PD20, a FA-D2 mutant cell line, and FANCD2 complemented PD20. In FANCD2-complemented and normal cells, anti-FANCD2 antibody immunoprecipitated STAT5. However, in mutant cells the same antibody immunoprecipitated STAT3, not STAT5. Thus, mutant (truncated) FANCD2 preferentially binds to and may activate STAT3 in the ground state. In fact, wild type FANCD2 also binds aberrantly to STAT3 in HSC536 (FA-C lymphoblasts) indicating that FANCC may influence the function of wild type FANCD2 and that binding of wild type FANCD2 to STAT3 does not require FANCD2 ubiquitinylation (FANCD2 is not ubiquitinylated in FA-C). Suspecting that in H2O2-exposed cells STAT5 signaling pathways lead to survival while STAT3 pathways lead to apoptosis, we transduced constitutively active mutants (*) of STATs 3 and 5 in mutant D2 and complemented cells. STAT3* increased apoptotic responses to H2O2 in complemented FA-D2 cells and STAT5* decreased apoptotic responses in H2O2-induced FA-D2 cells. In addition, the STAT5 inducible anti-apoptotic gene Bcl-XL was induced in H2O2-exposed complemented FA-D2 cells but not in FA-D2 cells. We conclude that FANCD2 functions to promote survival by ordering proper STAT signaling responses to oxidative stress and that this function of FANCD2 depends in part upon FA-C. We propose that FA cells are hypersensitive to oxidative stress in part because of imbalanced STAT signal transduction responses.
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Malemud, Charles J. "The role of the JAK/STAT signal pathway in rheumatoid arthritis." Therapeutic Advances in Musculoskeletal Disease 10, no. 5-6 (May 19, 2018): 117–27. http://dx.doi.org/10.1177/1759720x18776224.
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Proinflammatory cytokine activation of the Janus kinase/signal transducers and activators of transcription (JAK/STAT) signal transduction pathway is a critical event in the pathogenesis and progression of rheumatoid arthritis. Under normal conditions, JAK/STAT signaling reflects the influence of negative regulators of JAK/STAT, exemplified by the suppressor of cytokine signaling and protein inhibitor of activated STAT. However, in rheumatoid arthritis (RA) both of these regulators are dysfunctional. Thus, continuous activation of JAK/STAT signaling in RA synovial joints results in the elevated level of matrix metalloproteinase gene expression, increased frequency of apoptotic chondrocytes and most prominently ‘apoptosis resistance’ in the inflamed synovial tissue. Tofacitinib, a JAK small molecule inhibitor, with selectivity for JAK2/JAK3 was approved by the United States Food and Drug Administration (US FDA) for the therapy of RA. Importantly, tofacitinib has demonstrated significant clinical efficacy for RA in the post-US FDA-approval surveillance period. Of note, the success of tofacitinib has spurred the development of JAK1, JAK2 and other JAK3-selective small molecule inhibitors, some of which have also entered the clinical setting, whereas other JAK inhibitors are currently being evaluated in RA clinical trials.
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Zhu, Shiguo, Cecele J. Denman, and Dean A. Lee. "Valproic Acid Selectively Inhibits STAT3 Phosphorylation." Blood 114, no. 22 (November 20, 2009): 1720. http://dx.doi.org/10.1182/blood.v114.22.1720.1720.
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Abstract Abstract 1720 Poster Board I-746 Valproic acid (VPA), a histone deacetylase (HDAC) inhibitor (1), was found to enhance NK cell mediated antitumor activity by upregulating the surface expression of NKG2D ligands MICA and MICB on hepatoma cells (2). In contrast, VPA was found to impair NK cell antitumor activity by downregulating the surface expression of NKp30 and NKp46 on NK cells by blocking NFkB activation (3). Recently, we also found that VPA efficiently upregulates the surface expression of MICA, MICB, and ULBP family ligands on human osteosarcoma and neuroblastoma cells, but downregulates NKG2D surface expression on human NK cells. Similarly, the HDAC inhibitor MS275 efficiently upregulates expression of MICA, MICB, and ULBP family ligands on human osteosarcoma and neuroblastoma cells, but surprisingly, MS275 significantly upregulates NKG2D expression on NK cells. In addition, we found that VPA inhibited the cell growth of osteosarcoma cell lines more readily than MS275. To investigate the mechanism of these differing effects of VPA and MS275, we compared the effect of these HDAC inhibitors on Signal Transducer and Activator of Transcription (STAT) signaling, which are important signaling pathways in NK cells and many cancers. Here we show that VPA is a potent inhibitor of STAT3 phosphorylation at the tyrosine 705 residue in NK cells, whereas MS275 has no effect on STAT3 phosphorylation (Figure A). Moreover, this inhibition is highly specific, as VPA has no effect on STAT1 and STAT5 phosphorylation (Figure B). To further confirm VPA-mediated STAT3 inhibition, we detected STAT3 expression and the degree of tyrosine phosphorylation affected by VPA in a panel human osteosarcoma cells. We found that constitutive STAT3 phosphorylation is present in osteosarcoma SaOS2 and LM7 cells, but not in OS187 cells, which corresponded to the stronger growth inhibition caused by VPA in SaOS2 and LM7 cells compared to OS187 cells. These results are for the first to show that VPA, a HDAC inhibitor, is also a selective STAT3 inhibitor. VPA can upregulate NKG2D ligand expression on the tumor cell surface by HDAC inhibition, but may downregulate NKG2D expression on the NK cell surface by STAT3 inactivation. The antitumor activity of VPA may be via a mechanism of both HDAC inhibition and STAT3 inactivation. The knowledge of potent STAT3 inhibition by VPA is important for identifying potential new clinical applications for this drug. Disclosures No relevant conflicts of interest to declare.
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Kiper, Hatice Demet, Burcin Tezcanli Kaymaz, Ozlem Purclutepe, Ceyda Tunakan Dalgic, Nur Selvi, Aysegul Dalmizrak, Cigir Biray Avci, et al. "The Potential Role of STAT's in Anti-Leukemic Therapy with Different Drugs." Blood 120, no. 21 (November 16, 2012): 5120. http://dx.doi.org/10.1182/blood.v120.21.5120.5120.
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Abstract Abstract 5120 STAT pathways play a pivotal role in oncogenesis and leukemogenesis, thus targeting STAT signalling appears to be an effective anticancer treatment strategy. It has been described that constitutive activation of STAT3 and STAT5 plays a pro-oncogenic role both in acute and chronic myeloid neoplasms. In this study, we aimed to clarify the potential relationship between drug-induced apoptosis with different agents and STAT pathway. A third-generation bisphosphonate; zoledronate, an angiotensin-converting enzyme inhibitor (ACE-I); enalapril, a proteasome inhibitor which is used for treatment of multiple myeloma; bortezomib and a second-generation tyrosine kinase inhibitor; dasatinib were examined in this goal. Cell viability and cytotoxicity tests were conducted by using Trypan blue dye exclusion and XTT assays, respectively. Apoptotic analyses were performed by AnnexinV-EGFP staining method and fluorescence microscopy. Expression levels of STAT3, −5A and −5B genes were analysed in myeloid cell lines by qRT-PCR. The results showed that zoledronate; bortezomib and dasatinib decreased viability and proliferation and induced apoptosis in CML cell line K562 in a dose- and time-dependent manner which is associated by prominent decrease of STAT3, STAT5A and STAT5B mRNA expressions. Enalapril was also found to be cytotoxic and induced apoptosis in APL cell line HL60 in a dose- and time-dependent manner and the expression levels of STAT5A gene have significantly reduced in enalapril-treated HL60 cells as compared to untreated controls. Treatments of cell lines with other drugs were also associated with significant apoptosis in certain time points. The results and changes in expression of STAT's in mRNA level at 72nd hours are summarized in table. Taken together all these data showed that targeting STAT pathways by different drugs may be an appropriate approach in anti-leukemic therapy. This finding is important to propose that discovery or identification of novel agents targeted STATs may open new windows to the other hematological and solid malignancies which are associated with aberrant STAT expression. Table: The changes in STAT expressions after drug exposure in time-dependent manner with the dose of IC50. DRUGS CELL LINE IC50 APOPTOSIS (%) STAT3 mRNA Down Regulation (%) STAT5A mRNA Down Regulation (%) STAT5B mRNA Down Regulation (%) ENALAPRIL HL-60 7 μM 20 20* 76 5* ZOLEDRONATE K562 60 μM 34 63 31 57 BORTEZOMIB K562 177 μM 37 98 100 99 DASATINIB K562 3,314 nM 75 NA 33 78 * : Not significant NA: not applied Disclosures: No relevant conflicts of interest to declare.
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Xu, Bo, Ashish Bhattacharjee, Biswajit Roy, Hong-Min Xu, David Anthony, David A. Frank, Gerald M. Feldman, and Martha K. Cathcart. "Interleukin-13 Induction of 15-Lipoxygenase Gene Expression Requires p38 Mitogen-Activated Protein Kinase-Mediated Serine 727 Phosphorylation of Stat1 and Stat3." Molecular and Cellular Biology 23, no. 11 (June 1, 2003): 3918–28. http://dx.doi.org/10.1128/mcb.23.11.3918-3928.2003.
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ABSTRACT Interleukin-13 (IL-13) is a cytokine secreted by Th2 lymphocytes that is capable of inducing expression of 15-lipoxygenase (15-LO) in primary human monocytes. We recently demonstrated that induction of 15-LO requires the activation of Jak2 and Tyk2 kinases and Stats 1, 3, 5, and 6. Since IL-13-induced 15-LO expression was inhibited by H7 (a serine-threonine kinase inhibitor), we predicted that Stat serine phosphorylation may also be crucial for 15-LO expression. In this study, we present evidence indicating that IL-13-induced 15-LO mRNA expression was detectable as early as 1 h by real-time reverse transcription-PCR. We found that IL-13 induced a time-dependent serine phosphorylation of both Stat1 and Stat3, detectable at 15 min after IL-13 treatment. In addition, the activation of p38 mitogen-activated protein kinase (MAPK) was detected in a time-dependent fashion, with peak phosphorylation at 15 min after IL-13 treatment. SB202190, a p38 MAPK-specific inhibitor, markedly inhibited IL-13-induced Stat1 and Stat3 serine phosphorylation as well as DNA binding. Furthermore, treatment of cells with Stat1 or Stat3 decoys significantly impaired IL-13-induced 15-LO expression. Taken together, our results provide the first evidence that IL-13 induces p38 MAPK phosphorylation/activation, which regulates Stat1 and Stat3 serine 727 phosphorylation. Both of these events are important steps in IL-13-induced 15-LO expression in human monocytes.
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Jamaluddin, Mohammad, Sanjeev Choudhary, Shaofei Wang, Antonella Casola, Ruksana Huda, Roberto P. Garofalo, Sutapa Ray, and Allan R. Brasier. "Respiratory Syncytial Virus-Inducible BCL-3 Expression Antagonizes the STAT/IRF and NF-κB Signaling Pathways by Inducing Histone Deacetylase 1 Recruitment to the Interleukin-8 Promoter." Journal of Virology 79, no. 24 (December 15, 2005): 15302–13. http://dx.doi.org/10.1128/jvi.79.24.15302-15313.2005.
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ABSTRACT Respiratory syncytial virus (RSV) is a paramyxovirus that produces airway inflammation, in part by inducing interleukin-8 (IL-8) expression, a CXC-type chemokine, via the NF-κB/RelA and STAT/IRF signaling pathways. In RSV-infected A549 cells, IL-8 transcription attenuates after 24 h in spite of ongoing viral replication and persistence of nuclear RelA, suggesting a mechanism for transcriptional attenuation. RSV infection induces B-cell lymphoma protein -3 (Bcl-3) expression 6 to 12 h after viral infection, at times when IL-8 transcription is inhibited. By contrast, 293 cells, deficient in inducible Bcl-3 expression, show no attenuation of IL-8 transcription. We therefore examined Bcl-3's role in terminating virus-inducible IL-8 transcription. Transient expression of Bcl-3 potently inhibited virus-inducible IL-8 transcription by disrupting both the NF-κB and STAT/IRF pathways. Although previously Bcl-3 was thought to capture 50-kDa NF-κB1 isoforms in the cytoplasm, immunoprecipitation (IP) and electrophoretic mobility shift assays indicate that nuclear Bcl-3 associates with NF-κB1 without affecting DNA binding. Additionally, Bcl-3 potently inhibited the STAT/IRF pathway. Nondenaturing co-IP assays indicate that nuclear Bcl-3 associates with STAT-1 and histone deacetylase 1 (HDAC-1), increasing HDAC-1 recruitment to the IL-8 promoter. Treatment with the HDAC inhibitor trichostatin A blocks attenuation of IL-8 transcription. A nuclear targeting-deficient Bcl-3 is unable to enhance HDAC-1-mediated chemokine repression. Finally, small inhibitory RNA-mediated Bcl-3 “knockdown” resulted in enhanced RSV-induced chemokine expression in A549 cells. These data indicate that Bcl-3 is a virus-inducible inhibitor of chemokine transcription by interfering with the NF-κB and STAT/IRF signaling pathways by complexing with them and recruiting HDAC-1 to attenuate target promoter activity.
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Naka, Tetsuji, Minoru Fujimoto, and Tadamitsu Kishimoto. "Negative regulation of cytokine signaling: STAT-induced STAT inhibitor." Trends in Biochemical Sciences 24, no. 10 (October 1999): 394–98. http://dx.doi.org/10.1016/s0968-0004(99)01454-1.
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Demosthenous, Christos, Guangzhen Hu, Thomas E. Witzig, and Mamta Gupta. "Loss-of-Function Missense Mutations in Tyrosine Phosphatase PTPN6 Deregulate STAT3 Signaling in Diffuse Large B-Cell Lymphoma." Blood 124, no. 21 (December 6, 2014): 707. http://dx.doi.org/10.1182/blood.v124.21.707.707.
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Abstract Diffuse large B-cell lymphoma (DLBCL) is the most common type of non-Hodgkin Lymphoma and is characterized by deregulation of several signal transduction pathways. Approximately 50% patients with DLBCL are shown to have aberrant activation of the signal transducer and activator of transcription (STAT) pathway. However, mechanism of aberrant STAT3 signaling in DLBCL is not well understood. Protein tyrosine phosphatases (PTPs) are important enzymes that control the activity of multiple signaling pathways downstream of tyrosine kinases; mutations in PTPN11 have been found associated with the development of myeloproliferative disorder. In the current study, we sequenced a set of 38 DLBCL tumor samples for genetic mutations of PTPN6. Bi-directional sequencing reactions were performed on genomic DNA, and all exons of PTPN6 were amplified and analyzed by Sanger sequencing. We identified 2 novel heterozygous missense mutations in PTPN6 gene in 2 separate patients (2/38; 5.2%). The first missense mutation occurred in the exon 7, resulted in an Asp226 to lysine substitution (N226K), while other missense mutation found on exon 15 resulted in an Ala552 to valine substitution (A552V). In order to elucidate the functional significance of these mutations, we performed site directed mutagenesis to mutate wild type (WT) PTPN6 at codon 226 and 552. Both, wild-type PTPN6 (PTPN6WT) or those containing the N226K (PTPN6N226K) and A552V (PTPN6A552V) mutations were cloned and stably expressed in the HEK-293T cells with a lentiviral expression vector and PTPN6 phosphatase activity was measured. Our results showed marked reduction (70%) in the PTPN6 phosphatase activity in both the PTPN6 mutants as compared to the WT control. Interestingly both the PTPN6 mutants (PTPN6N226K and PTPN6A552V) promoted cell proliferation of HEK-293 cells as compared to WT PTPN6. In order to evaluate that whether or not PTPN6 mutations modulate STATs signaling, we analyzed STAT1, STAT3, STAT5 and STAT6 phosphorylation at tyrosine residue in cells stably transfected with WT or mutant PTPN6. While overexpression of WT PTPN6 reduced STAT3 phosphorylation, however no effect was observed on STAT1, STAT5 and STAT6 phosphorylation. Unlike WT-PTPN6, none of the PTPN6 mutants was able to dephosphorylate STAT3. In addition, PTPN6 A552V mutation was found to decrease the ability of PTPN6 to dephosphorylate STAT3 after induction with interleukin-10. Furthermore JAK2/JAK1 inhibition through the pharmacological inhibitor ruxolitinib (5μM) dephosphorylated STAT3 in WT PTPN6 as well as in PTPN6 mutants within 4 hours. Inhibition of JAK3 through a pharmacological inhibitor WHI-P154 (5μM) was able to completely dephosphorylated STAT3, however both the PTPN6 mutants were found resistant to JAK3 inhibition. Moreover, in a luciferase reporter assay compared to WT PTPN6, expressing either of the PTPN6 mutants (N226K and A552V) enhanced transcriptional activity of STAT3. To determine the effect of the PTPN6 mutations on the downstream targets of the JAK/STAT pathway, we demonstrated that Mcl-1, survivin and Bcl-2 protein level was significantly elevated in both mutant cells than that seen in the WT PTPN6 cells. Overall these results demonstrate that the N226K and A552V PTPN6 mutations occur in 5% of DLBCL tumors. Mutations we have found are both able to cause loss-of-function of PTPN6 that leads to increased STAT3 phosphorylation and increased transcriptional activity resulting in accumulation of Mcl-1, Bcl-2 and survivin proteins. Our data suggest that clinical trials of JAK1/JAK2 inhibitors need not be restricted to tumors with PTPN6 mutations but rather should focus on tumors with demonstrated aberrant STAT3 activation. Taken together, our data suggest that PTPN6 mutations may guide the clinical use of inhibitors of JAK3 kinase in DLBCL. Disclosures No relevant conflicts of interest to declare.
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Jia, Lili, Wenli Yu, Hongli Yu, and Yiqi Weng. "Electroacupuncture Pretreatment Attenuates Intestinal Injury after Autogenous Orthotopic Liver Transplantation in Rats via the JAK/STAT Pathway." Oxidative Medicine and Cellular Longevity 2020 (August 4, 2020): 1–11. http://dx.doi.org/10.1155/2020/9187406.
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Background. Liver transplantation induces self-injury and affects remote organs, such as the lung, kidney, and intestine. Postoperative intestinal dysfunction has been associated with prolonged hospitalization and affects a patient’s health and quality of life. Electroacupuncture (EA) has been proven effective in multiple organ protection. However, the potential mechanism underlying the protective effects of EA on intestinal injury after liver transplantation remains unclear. Methods. After establishing an autogenous orthotopic liver transplantation (AOLT) model, we studied the effects of EA pretreatment on intestinal injury after AOLT. We used the JAK2-specific inhibitor AG490 to explore the underlying mechanism. Histological analysis and apoptosis assays were used to evaluate intestinal injury. Oxidative stress index and inflammatory response were also measured after AOLT. Furthermore, we detected the phosphorylation levels of JAK2, STAT1, and STAT3 by Western blot. Results. We found that pretreatment with EA alleviated intestinal injury after AOLT, as shown by HE staining and TUNEL methods. EA pretreatment inhibited the expressions of p-JAK2, p-STAT1, and p-STAT3 in the intestines after AOLT. Upon treatment with JAK2-specific inhibitor AG490, intestinal injury was balanced. Conclusion. The data indicated EA pretreatment alleviated intestinal injury after AOLT by inhibiting the JAK/STAT signaling pathway. These results provide basic evidence to support the potential therapeutic efficacy of EA.
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Goodman, Michael D., Sheryl E. Koch, Geraldine A. Fuller-Bicer, and Karyn L. Butler. "Regulating RISK: a role for JAK-STAT signaling in postconditioning?" American Journal of Physiology-Heart and Circulatory Physiology 295, no. 4 (October 2008): H1649—H1656. http://dx.doi.org/10.1152/ajpheart.00692.2008.
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Postconditioning (POC), a novel strategy of cardioprotection against ischemia-reperfusion injury, is clinically attractive because of its therapeutic application at the predictable onset of reperfusion. POC activates several intracellular kinase signaling pathways, including phosphatidylinositol 3-kinase (PI3K)-Akt (RISK). The regulation of POC-induced survival kinase signaling, however, has not been fully characterized. JAK-STAT activation is integral to cardiac ischemic tolerance and may provide upstream regulation of RISK. We hypothesized that POC requires the activation of both JAK-STAT and RISK signaling. Langendorff-perfused mouse hearts were subjected to 30 min of global ischemia and 40 min of reperfusion, with or without POC immediately after ischemia. A separate group of POC hearts was treated with AG 490, a JAK2 inhibitor, Stattic, a specific STAT3 inhibitor, or LY-294002, a PI3K inhibitor, at the onset of reperfusion. Cardiomyocyte-specific STAT3 knockout (KO) hearts were also subjected to non-POC or POC protocols. Myocardial performance (+dP/d tmax, mmHg/s) was assessed throughout each perfusion protocol. Phosphorylated (p-) STAT3 and Akt expression was analyzed by Western immunoblotting. POC enhanced myocardial functional recovery and increased expression of p-STAT3 and p-Akt. JAK-STAT inhibition abrogated POC-induced functional protection. STAT3 inhibition decreased expression of both p-STAT3 and p-Akt. PI3K inhibition also attenuated POC-induced cardioprotection and reduced p-Akt expression but had no effect on STAT3 phosphorylation. Interestingly, STAT3 KO hearts undergoing POC exhibited improved ischemic tolerance compared with KO non-POC hearts. POC induces myocardial functional protection by activating the RISK pathway. JAK-STAT signaling, however, is insufficient for effective POC without PI3K-Akt activation.
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Banes-Berceli, Amy K. L., Pimonrat Ketsawatsomkron, Safia Ogbi, Bela Patel, David M. Pollock, and Mario B. Marrero. "Angiotensin II and endothelin-1 augment the vascular complications of diabetes via JAK2 activation." American Journal of Physiology-Heart and Circulatory Physiology 293, no. 2 (August 2007): H1291—H1299. http://dx.doi.org/10.1152/ajpheart.00181.2007.
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The JAK/STAT pathway is activated in vitro by angiotensin II (ANG II) and endothelin-1 (ET-1), which are implicated in the development of diabetic complications. We hypothesized that ANG II and ET-1 activate the JAK/STAT pathway in vivo to participate in the development of diabetic vascular complications. Using male Sprague-Dawley rats, we performed a time course study [ days 7, 14, and 28 after streptozotocin (STZ) injection] to determine changes in phosphorylation of JAK2, STAT1, and STAT3 in thoracic aorta using standard Western blot techniques. On day 7 there was no change in phosphorylation of JAK2, STAT1, and STAT3. Phosphorylation of JAK2, STAT1, and STAT3 was significantly increased on days 14 and 28 and was inhibited by treatment with candesartan (AT1 receptor antagonist, 10 mg·kg−1·day−1 orally in drinking water), atrasentan (ETA receptor antagonist, 10 mg·kg−1·day−1 orally in drinking water), and AG-490 (JAK2 inhibitor, 5 mg·kg−1·day−1 intraperitoneally). On day 28, treatment with all inhibitors prevented the significant increase in systolic blood pressure (SBP; tail cuff) of STZ-induced diabetic rats (SBP: 157 ± 9.0, 130 ± 3.3, 128 ± 6.8, and 131 ± 10.4 mmHg in STZ, STZ-candesartan, STZ-atrasentan, and STZ-AG-490 rats, respectively). In isolated tissue bath studies, diabetic rats displayed impaired endothelium-dependent relaxation in aorta (maximal relaxation: 95.3 ± 3.0, 92.6 ± 7.4, 76.9 ± 12.1, and 38.3 ± 13.1% in sham, sham + AG-490, STZ + AG-490, and STZ rats, respectively). Treatment of rats with AG-490 restored endothelium-dependent relaxation in aorta from diabetic rats at 14 and 28 days of treatment. These results demonstrate that JAK2 activation in vivo participates in the development of vascular complications associated with STZ-induced diabetes.
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Shi, Ce, Lina Han, Yoko Tabe, Hong Mu, Shuo-Chieh Wu, Jin Zhou, Zhihong Zeng, et al. "Dual Targeting of JAK2 Signaling with a Type II JAK2 Inhibitor and of mTOR with a TOR Kinase Inhibitor Induces Apoptosis in CRLF2-Rearranged Ph-like Acute Lymphoblastic Leukemia." Blood 124, no. 21 (December 6, 2014): 3706. http://dx.doi.org/10.1182/blood.v124.21.3706.3706.
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Abstract Philadelphia chromosome-like acute lymphoblastic leukemia (Ph-like ALL) is a subtype of high-risk B-precursor ALL (B-ALL) that carries a high risk of relapse after conventional chemotherapy (Mullighan et al, N Engl J Med. 2009). Rearrangements in CRLF2, leading to overexpression of the receptor for the cytokine thymic stromal lymphopoietin (TSLP), are present in approximately 50% of Ph-like ALLs and are associated with hyperactive JAK/STAT and PI3K/mTOR signaling (Harvey et al, Blood 2010; Tasian et al, Blood 2014). Previous studies established that combining a tyrosine kinase inhibitor (TKI) with an mTOR inhibitor provides greater anti-leukemia efficacy than a TKI alone in Ph+ B-ALL (Janes et al, Nat. Med. 2013). While allosteric mTOR inhibitors such as rapamycin only partially block mTORC1 and do not directly inhibit mTORC2, second-generation ATP-competitive mTOR kinase inhibitors (TOR-KIs) efficiently block both mTOR outputs and show greater efficacy when combined with TKIs. In this study, we investigated anti-leukemia efficacy and intracellular signaling networks in Ph-like CRLF2+ ALL models treated with combinations of a type I or type II JAK-2 inhibitor and a TOR-KI. The inhibitors were tested in human B-precursor Ph-like ALL cell lines MUTZ5 (IGH@-CRLF2 translocation, JAK2 R683G mutation) and MHH-CALL-4 (IGH@-CRLF2 translocation, JAK2 I682F mutation), B-ALL cell line REH (CRLF2wt), and primary CRLF2+ xenograft cells in vitro. For signaling and growth inhibition studies, cells were stimulated with 25 ng IL-7 or TSLP for 30 min, then with JAK2 type I inhibitor ruxolitinib (500nM) or type II inhibitor NVP-BBT594 (500nM) (Andraos et al., Cancer Discov. 2012) and allosteric mTOR inhibitor rapamycin or TOR-KI AZD2014. Effects on intracellular signaling were determined by phospho-flow cytometry. Anti-leukemia effects were characterized by viable cell counts and annexin V flow cytometry. In vitro stimulation of CRLF2-rearranged cells with TSLP robustly induced JAK/STAT signaling (p-JAK2(Tyr1008), p-STAT5(Ty694)) and AKT/pS6 signaling (p-AKT(Ser473), p-rS6(S235/236) (Fig. 1A). Stimulation with IL-7, mimicking support by the normal bone marrow environment, induced a lesser degree of activation of these phospho-proteins, except for p-4EBP1(T37/46), which was constitutively highly expressed in these cells and further induced by IL-7. These findings warranted combination studies of JAK2 and mTOR inhibitors. JAK2 inhibition with ruxolitinib or BBT594 efficiently inhibited TLSP-induced STAT5, AKT, and S6 activation, yet failed to decrease p-4EBP1 (Fig. 1A). AZD2014 but not rapamycin fully inhibited p-4EBP1, consistent with efficient inhibition of TORC1, and caused profound cell cycle arrest and growth arrest in CRLF2+ cells (Fig. 1A, C). In turn, combination of ruxolitinib and AZD2014 further reduced cell proliferation but did not induce apoptotic cell death (Fig. 1B, D). Recent studies indicate persistence of JAK2-mutated cells in myeloproliferative neoplasms upon long-term exposure to a type I JAK2 inhibitor, mediated by JAK2 heterodimerization and reactivation of JAK-STAT signaling (Koppikar et al., Nature 2012). We therefore compared the in vitro efficacy of ruxolitinib and BBT594, a type II JAK2 inhibitor that retains the ability to bind inactive JAK2, in Ph-like ALL cells. In MUTZ-5 but not in MHH-CALL-4 cells, ruxolitinib increased JAK2 activation loop phosphorylation (p-JAK2-Tyr1008) despite suppression of STAT5 phosphorylation; in contrast, BBT594 diminished both p-JAK2 and p-STAT5. Unexpectedly, BBT594 induced apoptotic cell death in both MUTZ5, MHH-CALL-4 (Fig 1B) and in ALL blasts recovered from primary CRLF2+ xenograft and grown in OP9 in vitro co-culture; the combination of BBT594 with AZD2014 increased apoptosis and reduced cell viability even further, in both cell lines and in stroma-attached primary ALL cells. In summary, these results suggest that efficient blockade of JAK2/STAT5 with a type II JAK2 inhibitor translates into cell death of JAK2-addicted CRLF2-rearranged cells and may have the capacity to eliminate JAK2-mutated clones. Concomitant blockade of TORC1 signaling with a TOR-KI reduces B-ALL cell proliferation through potent inhibition of 4EBP1 and causes synthetic lethality, providing avenues for novel, rationally designed combinatorial regimens in this subset of Ph-like B-ALL. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.
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Buglio, Daniela, Manuela Lemoine, Sattva S. Neelapu, Francisco Vega, Donald Berry, and Anas Younes. "NVP-BEZ235, A Dual Inhibitor of Phosphoinositol-3-Kinase (PI3K) and Mammalian Target of Rapamycin (mTOR), Is a Potent Inhibitor of Lymphoma Cell Growth and Survival." Blood 118, no. 21 (November 18, 2011): 4965. http://dx.doi.org/10.1182/blood.v118.21.4965.4965.
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Abstract Abstract 4965 The Phosphatidylinositol-3-kinase (PI3K)/AKT/mTOR pathway is frequently deregulated in Hodgkin (HL) and non-Hodgkin lymphoma (NHL), and has been linked with tumor cell growth and survival. Although several proteins/enzymes in this pathway can be targeted by a variety of small molecules in vitro and in vivo, it remains unclear which protein target is the ideal for clinical testing. Previous studies demonstrated that the clinical activity of mTOR inhibitors may be attenuated by a negative feedback loop that involves activation of AKT, suggesting that a dual inhibition of AKT and mTOR activation may produce a better therapeutic outcome. To test this hypothesis, we evaluated the in vitro activity of NVP-BEZ235, a dual inhibitor of PI3K and mTOR, in a panel of 13 HL and NHL cell lines. NVP-BEZ235 inhibited cell growth and induced apoptosis in lymphoma cell lines in a time and dose dependent manner. After 48 hours of incubation, the IC50 ranged between 50 and 100 nM, and it was equally effective in ABC and GCB-derived DLBCL cell lines. NVP-BEZ235 induced cell death was primarily due to induction of apoptosis, as evident by the annexin-V and PI dual staining method, and the induction of caspase 3 and PARP cleavage. NVP-BEZ235 effectively inhibited the activation of the PI3K pathway at several steps, including decreasing the phosphorylation level of p-Akt (Ser473), p-Akt (Thr308), p-mTOR, p-4-EBPI and pP70S6K. Because lymphoma cells frequently depend on multiple activated signaling pathways to promote their survival, including the JAK/STAT pathway, we investigated the potential synergy between PI3K and JAK/STAT pathway inhibitors. Lymphoma cells were variably sensitive to the JAK1/2 inhibitor INCB16562 in vitro. Submaximal concentrations of NVP-BEZ235 demonstrated a synergistic activity with INCB16562. Collectively, our data show that the PI3K/mTOR inhibitor NVP-BEZ235 is highly effective against a wide range of lymphoma cell lines, and warrants evaluating it alone and in combination with JAK/STAT inhibitors in phase I/II clinical trials in patients with relapsed lymphoma. Disclosures: No relevant conflicts of interest to declare.
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Shi, Ce, Lina Han, Qi Zhang, Kathryn G. Roberts, Eugene Park, Yoko Tabe, Rodrigo Omar Jacamo, et al. "Combined Targeting of JAK2 with a Type II JAK2 Inhibitor and mTOR with a TOR Kinase Inhibitor Constitutes Synthetic Activity in JAK2-Driven Ph-like Acute Lymphoblastic Leukemia." Blood 126, no. 23 (December 3, 2015): 2529. http://dx.doi.org/10.1182/blood.v126.23.2529.2529.
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Abstract Background and rationale: Philadelphia chromosome-like acute lymphoblastic leukemia ("Ph-like ALL") is a subtype of high-risk B-precursor ALL (B-ALL), which carries a high risk of relapse with conventional chemotherapy(Roberts et al, N Engl J Med. 2014). Rearrangements in CRLF2, leading to overexpression of cytokine receptor for thymic stromal lymphopoietin (TSLP), are present in approximately 50% of Ph-like ALL and are associated with hyperactive JAK/STAT and PI3K/mTOR signaling (Harvey et al, Blood 2010;Tasian et al, Blood 2014).In addition,JAK2 fusion proteins, such as PAX5-JAK2 represent a novel class of JAK2-driven cellular transformation in B-ALL (Dagmar et al, Blood 2015). Our prior studies in Ph+ B-ALL established that combining tyrosine kinase inhibitors (TKIs) with second generation ATP-competitive mTOR kinase inhibitors (TOR-KIs) provides greater anti-leukemia efficacy compared to TKIs in Ph+ ALL (Janeset al, Nat. Med. 2013). In this study, we investigated anti-leukemia efficacy and intracellular signaling networks upon combination of type I or type II JAK2 inhibitors and TOR-KIs in JAK2-driven Ph-like ALL models. Methods. The human B-precursor Ph-like ALL cell lines MUTZ5 (which harborsIGH-CRLF2 translocation and JAK2 R683G mutation), MHH-CALL-4 (IGH-CRLF2 translocation and JAK2 I682F),Reh (ETV6-RUNX1 B-precursor ALL cell line)and mouse Arf-null PAX5-JAK2-MIG + IK6-MIR(IL7-dependent primary Arf-/- pre-B cells expressing the dominant negative Ikaros isoform IK6 with PAX5-JAK2 fusion protein) were studied. Signal transduction inhibitors (STIs): JAK2 type I inhibitor ruxolitinib and type II inhibitor NVP-BBT594 (Andraos et al., Cancer Discovery 2012); allosteric mTOR inhibitor rapamycin or mTOR-KI AZD2014. Effects on intracellular signaling were determined using phospho-flow cytometry and Westernblot analysis. Anti-leukemia effects were quantified using CellTiter-Glo viability assay and annexin V flow cytometry. Results. In vitro stimulation of CRLF2-rearranged cells with TSLP robustly induced JAK/STAT signaling (Fig 1D). JAK2 inhibition with ruxolitinib or BBT594 efficiently inhibited TLSP-induced STAT5, AKT, ERK and S6 activation, yet failed to affect4E-BP1 activation. The TOR-KI AZD2014 but not rapamycin fully inhibited phosphorylation of 4E-BP1, consistent with efficient inhibition of TORC1, and caused profound cell cycle arrest and growth inhibition of Ph-like cells. Combination of ruxolitinib and AZD2014 further inhibited cell proliferation, yet did not induce apoptotic cell death. Recent studies indicate persistence of JAK2-mutated cells upon chronic exposure to type I JAK2 inhibitors, through an adaptive resistance mechanism involving JAK2 heterodimerization and reactivation of JAK-STAT signaling (Koppikar et al., Nature 2012). We therefore compared the in vitro efficacy of ruxolitinib and BBT594, a type II JAK2 inhibitor that retains the ability to bind inactive JAK2 in Ph-like ALL cells. In MUTZ-5 but not in MHH-CALL-4 cells, ruxolitinib increased JAK2 activation loop phosphorylation (p-JAK2-Tyr1008) despite suppression of p-STAT5; in contrast, BBT594 diminished bothp-JAK2 and p-STAT5 in both cell lines. Unexpectedly, BBT594 induced apoptotic cell death in all JAK2-driven Ph-like ALL cell lines MUTZ5, MHH-CALL-4 and Arf-null PAX5-JAK2+IK6, but not in REH cells. Combination of BBT594 with AZD2014 further inhibited phosphorylation of JAK2, AKT, 4E-BP1 and eIF4E, and synergistically induced apoptosis and reduced cell viability in Ph-like ALL cell lines(combination index: MUTZ5, 0.71; MHH-CALL-4, 0.57; Arf-nullPAX5-JAK2+ IK6, 0.81). Of importance, BBT594 and AZD2014 combination induced apoptosis in five JAK2-mutant Ph-like ALL xenograft primary samples. In summary, these results suggest that efficient blockade of JAK2/STAT5 with type II JAK2 inhibitors translates into cell death of mutant JAK2-driven Ph-like ALL cells. Furthermore, concomitant blockade of TORC1 signaling with TOR-KI reduces B-ALL cell proliferation through potent inhibition of 4E-BP1 and causes synthetic activity, providing avenues for novel rationally designed combinatorial regimens in this subset of Ph-like B-ALL. The in vivo studies to test these hypotheses are ongoing using patient-derived xenografts. Disclosures Jabbour: Pfizer: Consultancy, Research Funding. Tasian:Incyte: Consultancy; Gilead: Research Funding. Mullighan:Amgen: Honoraria, Speakers Bureau; Cancer Science Institute: Membership on an entity's Board of Directors or advisory committees; Incyte: Consultancy, Honoraria; Loxo Oncology: Research Funding. Konopleva:Novartis: Research Funding; AbbVie: Research Funding; Stemline: Research Funding; Calithera: Research Funding; Threshold: Research Funding.