Dissertations / Theses on the topic 'Onkologin'

The incidence of urinary bladder carcinoma is increasing and many patients die every year of this disease despite assumed radical therapy. Thus, there is a need for improved methods of diagnosis and therapy. Radionuclide targeting is based on achieving specific delivery of radioactive nuclides to tumour cells with minimal damage to surrounding normal tissues. Two possible target structures are the epidermal growth factor (EGF) receptor and the related receptor HER-2.

Cellular binding and retention of ¹²⁵I-EGF-dextran conjugates was investigated in two bladder carcinoma cell lines. The conjugate bound specifically to the EGF receptor with delayed maximum binding, limited intracellular degradation and prolonged cellular retention compared to ¹²⁵I-EGF.

EGF was labelled using different radionuclides and methods. All the labelled variants bound specifically to the tumour cells although the cellular binding patterns and retention varied considerably. ¹¹¹In-DTPA-EGF had highest cellular retention and in decreasing order ²¹¹At-benzoyl-EGF and ¹²⁵I-labelled EGF.

Bladder cancer spheroids bound both ¹²⁵I-EGF-dextran as well as ¹²⁵I-EGF. Conjugate binding increased during a 48 h incubation period and was most prominent in the outer cell layers. The length of the dextran chain appeared not to alter the binding pattern.

The expression of EGF receptors and HER-2 in metastases and primary bladder carcinoma tumours was investigated. Both receptors were expressed in the majority of metastases and primary tumours.

Targeting the EGF receptor and/or HER-2 in urinary bladder carcinoma is an exciting new concept.

Tyrosine phosphorylation is a central mechanism in cellular signalling leading to proliferation, migration or differentiation. Protein tyrosine phosphorylation is regulated by the coordinated actions of protein tyrosine kinases and protein tyrosine phosphatases. This thesis investigates the involvement of tyrosine phosphatases in contact-induced growth inhibition of cells. Furthermore, it describes the structure and function of the extracellular domain of the receptor-like tyrosine phosphatase DEP- 1.

Tyrosine phosphatases, negatively regulating tyrosine kinases, have been suggested being involved in contact-induced growth inhibition of cells. Both endogenous EGF-receptors and transfected PDGF receptors showed a decreased ligand-induced tyrosine phosphorylation in cells of dense cultures. This difference was found to be due to increased receptor-directed tyrosine phosphatase activity in dense cultures.

Density enhanced tyrosine phosphatase-1 (DEP-1) is a receptor-like tyrosine phosphatase. It was found that DEP-1 contains chondroitin sulfate chains, thus identifying DEP-1 as a proteoglycan. Furthermore, DEP-1 was found to interact with a heparan sulfate proteoglycan.

No ligands have been identified for DEP-1. We have established a biacore-based assay for the identification of molecules interacting with the extracellular domain of DEP-1. A library of cell conditioned media was screened with the biacore assay. One of the samples was found to contain DEP-1 interacting molecules. Purification of the ligand has been initiated.

In an attempt to identify modulators of DEP-1 activity, Matrigell™ , a preparation of extracellular matrix was investigated. Stimulation with Matrigel™ was found to increase the specific activity of DEP-1 through interactions between the extracellular domain of DEP-1 and Matrigel™ component(s).

The DNA double-strand break (DSB) is a critical lesion which, if not completely restored, can have serious biological consequences. The relative biological effectiveness (RBE) of many severe end-points are closely related to radiation quality, with increased effectiveness at elevated ionization density. Data presented provide information about the influence of radiation quality on the initial processes causing DNA damage, and the mechanisms leading to its restoration. Such information will increase the understanding of radiation action mechanisms in mammalian cells.

Human cells were irradiated with accelerated ions having linear energy transfer (LET) values in the range 40-225 keV/μm, and ⁶⁰Co-photons. Detailed analyses of the DNA fragment distributions were performed in the size-range 5 kilobasepairs to 6 megabasepairs by pulsed-field gel electrophoresis.

A non-random fragmentation of DNA was evident, with an elevated number of small and medium-sized fragments for ion irradiation, and the total number of breaks increased by 80-110% when these fragments were included in the analyses. The RBE for DSB induction was 1.2-1.5. A two-fold increase of the number of breaks induced per nitrogen ion passing the cell nuclues was found when LET was increased from 80 to 225 keV/μm, indicating a possible role of particle track structure in DSB induction. Furthermore, the ability to repair DNA was closely related to radiation quality, with an increased proportion of unrejoined breaks for densely ionizing radiation. Surprisingly, the majority of breaks were rapidly rejoined even following exposure to high-LET radiation. The proportion of breaks restored by the slow phase showed a five-fold increase for the highest LET tested, compared with photons. The results presented nominates the complexity of breaks as one determining factor for reduced reparability reported following high-LET exposure.

The purpose of this thesis was to evaluate the diagnostic potential of a new ultrasound contrast agent,Sonazoid^TM, intended for use in patients with suspicion of prostate cancer.

The sonographic appearance of normal prostatic vascularity in dogs was evaluated before and after injection of Sonazoid,using different Doppler flow detection modes.The use of Sonazoid significantly improved the visibility of the vascular pattern in normal dog prostate,both with colour and power Doppler imaging.There was a significant difference in the depiction of blood flow in the prostate between the two imaging modalities,showing the power Doppler superior to colour Doppler imaging.The contrast revealed a radial,spoke-like intraprostatic pattern,not seen prior to contrast injection.

Different ultrasound imaging modalities were tested in a small group of young healthy male volunteers to evaluate the visibility of the normal prostate blood flow with and without Sonazoid.

The ultrasound contrast agent improved the visibility of the normal human prostate vascular anatomy for both colour and power Doppler imaging.Again,the improvement was significantly better for power Doppler than for colour Doppler imaging.Using fundamental B-mode,there was no major difference in the ultrasound appearance of the prost ate vascular it y before and after i njection of Sonazoid.Cont rast dynamic st udies of blood flow wit hi n t he normal gland showed a filling from the periphery towards the centre in all subjects,demonstrating a symmetric, radial vascular pattern.

A canine prostate model was used to investigate if Sonazoid,could improve the visualisation of prostatic vessels to better delineate areas on normal and decreased blood flow.Both 2D and 3D power Doppler imaging was performed in this study.The visibility of the prostate blood flow improved significantly following injection of Sonazoid for both 2D and 3D power Doppler imaging.There was,however,no major difference in depicting the vascularity using 2D and 3D imaging.After injection of Sonazoid,a disturbance of the radial vascular pattern and a lack of blood flow symmetry between the two prostate lobes were possible to identify.The added information gained by injection of Sonazoid made it possible to identify areas of decreased blood flow not seen prior to contrast injection.

The vascular pattern of lesions,identified with B-mode imaging in patients with suspicion of prostate cancer,was studied,using Sonazoid.Contrast dynamic inflow in the lesions,compared to the adjacent tissue was investigated in the same study.Prostate cancer lesions appeared hypervasuclar prior to ultrasound contrast agent.Three of six cancer lesions changed from hypervascular to marked hypervascular following injection of Sonazoid,a finding that might be interpreted as a higher level of confidence.None of the non-cancer lesions were assessed as hypervascular after Sonazoid injection,a possible increased value of a negative finding.Four of the cancer lesions enhanced earlier compared to the surrounding prostate tissue,following ultrasound contrast injection.The results indicate that changes in vascular architecture,e.g.induction of angiogenesis by tumour cells,can be observed by ultrasonographically determining the inflow pattern of an intravenously injected ultrasound contrast agent.

Members of the transforming growth factor-β (TGF-β) superfamily of growth and differentiation factors regulate a vast array of biological functions in the adult, and are of great importance in governing cell fate determination and patterning in the developing embryo. The TGF-β signal is propagated intracellularly by Smad proteins resulting in transcriptional responses. Smad6 and Smad7 are inhibitory Smads known to downregulate the TGF-β signal and thereby possibly modulating the biological response. This thesis describes a functional analysis of the inhibitory Smad7 from an in vitro and in vivo perspective.

The prostate gland is dependent on androgens for its growth and differentiation. Androgen withdrawal can cause regression and apoptosis in normal and malignant prostate. Previous studies suggest a role for TGF-β in the apoptotic mechanism. We investigated the expression levels of Smad proteins in the rat ventral prostate as well as in an androgen sensitive prostate tumor model (Dunning R3327 PAP) by immunohistochemistry. We observed an increased immunoreactivity for Smad3, Smad4 and phosphorylated Smad2 in the rat ventral prostate epithelial cells after castration, as well as in the prostate tumor cells. Expression of inhibitory Smad6 and Smad7 were also increased in both normal and malignant prostate in response to castration.

Several studies have shown that Smad7 is upregulated in response to TGF-β stimuli, suggesting a role in a negative feedback loop attenuating the TGF-β response. We investigated the molecular mechanism behind that response by studying the transcriptional regulation of the Smad7 gene. We identified a palindromic Smad binding element (SBE) in the promoter. Point mutations introduced into the SBE abolished transcriptional activation via TGF-β. We also observed that mutating or deleting binding motifs for Sp1 and AP-1, led to an attenuation of the TGF-β mediated transcriptional induction as well as the basal promoter activity.

Gene ablation of Smad proteins has revealed specific physiological and developmental roles. We analysed mice targeted on the Smad7 locus. The mice appeared viable and fertile with a slight reduction in litter size, suggesting a perinatal loss. Biochemical analysis of mouse embryonic fibroblasts (MEFs) showed no major difference between wild type and mutant MEFs.

The role of platelet-derived growth factor (PDGF) in malignancies involves both autocrine and paracrine stimulation of cells within the tumor. The interstitial fluid pressure (IFP) is one of the forces that govern the transvascular flow of fluids. In both experimental and clinical cancers, the IFP is elevated and is thought to act as a barrier for delivery of drugs. Increasing evidence points to PDGF as a positive regulator of the interstitial fluid pressure in loose connective tissue. In this thesis, the effect of PDGF receptor inhibition on the tumor IFP, transvascular transport and efficacy of anti-cancer drugs is investigated.

All studies were performed using tumor models that display extensive tumor stroma and PDGF receptor expression restricted to stroma cells. Blocking of PDGF receptor signaling significantly reduced the tumor IFP in various tumor models. In parallel, pre-treatment with PDGF antagonists increased the tumor content of cytotoxic agents without affecting the uptake in other organs. Moreover, combination treatment with PDGF receptor inhibitors and chemotherapeutic agents dramatically enhanced the anti-tumor effects of the cytotoxic drugs, whereas treatment with only PDGF receptor inhibitors did not affect the growth of the tumors. Beneficial effects on the tumor reponse to radioimmunotherapy were also produced after concomitant administration of PDGF antagonists. Importantly, anti-angiogenic effects, changes in cell composition and increased tumor cell sensitivity to cytotoxic agents were ruled out as the cause for the synergistic effects.

Studies with different temporal scheduling of PDGF receptor inhibitors demonstrated a perfect correlation between a reduced IFP, an increased transvascular transport and an enhanced therapeutic effect of cytotoxic drugs, strongly suggesting that the phenomena are causally linked.

The studies presented herein illustrate for the first time the potential of cells in the stroma compartment as a target for efforts to treat cancer. In conclusion, a novel, possibly general, strategy to enhance the effects of conventional anti-cancer drugs has been identified.

Infrainguinal bypass grafting is an established method in the treatment of patients with femoropopliteal and crural occlusive disease leading to critical lower limb ischaemia (CLI). However, complications related to surgical procedure are not negligible and percutaneous transluminal angioplasty (PTA) has emerged as an alternative. The present thesis covers some aspects of infrainguinal PTA in patients with chronic severe lower limb ischaemia.

The records of 217 patients undergoing 272 PTA procedures at various infrainguinal arterial segments were analysed. The indication for intervention was subcritical ischaemia in 76 limbs and critical ischaemia in 177 limbs. The role of duplex ultrasound examination in the selection of patients for PTA was retrospectively evaluated following a prospective validation of the method against angiography.

A technically successful PTA was achieved in 89%. The overall 30-day mortality was 2.7%. No patient underwent amputation directly related to failed PTA. The primary success rates at 12 and 60 months following femoropopliteal PTA were 40% and 27% compared, to 51% and 36% in limbs undergoing crural artery PTA. Primary success rate in limbs with SFA occlusion longer than 5 cm was only 12% after 5 years, compared to 32% if the occlusion was equal or less than 5 cm in length (p<0.01). In patients undergoing distal PTA through patent infrainguinal grafts, the primary and primary assisted patency rates at 3 years were 32% and 53%, respectively. The sensitivity of duplex scanning in the selection of lesions for PTA was less satisfactory in the popliteal and crural arteries compared to the superficial femoral arteries.

In conclusion, the results of infrainguinal PTA performed for treatment of subcritical or CLI seemed to be inferior to the results of surgical interventions reported in the literature. However, due to the fact that the PTA procedure does not preclude the performance of bypass grafting, it might be an alternative to surgical intervention in limbs with stenotic or short occlusive lesions.