| Abstract |
Introduction: The endothelial barrier is the anatomical boundary that controls tumor growth rate and metastasis, supplying the tumor with oxygen and nutrients. The interaction between the endothelial barrier and the primary tumor can be well described by angiogenesis, a process that involves several endothelial features such us growth rate, migration ability and permeability. The tumor environment consists of several factors secreted either by the tumor cells or by stromatic cells and acts as the angiogenic switch, thus controlling whether endothelial cells will acquire an angiogenic profile. Another component that regulates angiogenesis, is inflammation. It is described that inflammatory cells secrete cytokines that interfere with the angiogenic process usually as inducers. However there is always a possibility for the inflammatory cells to participate in hosts local immune defense, thus suppressing tumor growth. Materials and methods: A group of normal breast tissue samples and a group of breast tissue samples were randomly chosen from the archives of the Pathology Laboratory of the University of Crete. In this study several molecules (VEGFR-1, VEGFR-2, PDGFRα, PDGFRβ, COX-2, VCAM-1, ICAM-1, E-Selectin) were assessed by immunohistochemistry (IHC) in order to detect differences in expression between normal and malignant breast tissue. At the same time angiogenesis was quantified by Chalkey count using CD31 and CD105 as endothelial markers. Endothelial cell cycle inhibitor p21WAF1/Cip1 expression was detected both in tissue samples and in a co-culture model of endothelial cells (EA hy 926) and breast cancer cells (MDA-MB 468) and by RT-PCR it was defined whether p21WAF1/Cip1 alterations due to transcription regulation or not. Applying TAT technology a TAT-p21waf1 fusion protein was designed, expressed, isolated and administered to ΕA hy 926 cells grown in tumor conditioned medium, in the aim of canceling the tumor-derived angiogenic message. Finally, having in mind to increase the endothelial permeability in order to maximize drug delivery to the tumors, we 20 examined the effects of imatinib on the EA.hy 926 endothelial cell line. Results: Angiogenesis quantification revealed a significant increase of the microvascular density (MVD) in the breast cancer tissue samples (p<0.05). Moreover CD105 was found to be a more sensitive marker regarding tumor angiogenesis. From all the above mentioned molecules only PDGFRβ, Cox-2 and VCAM-1 were significantly altered in breast cancer, with the first two to present an increased and the third a decreased expression. P21waf1 was significantly decreased (p<0.05) in breast cancer as shown both by the IHC results and by the results on the ΕΑ.hy 926 endothelial cells. This decrease was rather transcriptional. TAT-p21WAF1 fusion protein succeeded in canceling the angiogenic message, as shown by the cell growth rate of cells grown in TCM with or without TAT-p21. Finally imatinib resulted in increased endothelial permeability possibly via Ve-cadherin down-regulation. At the same time imatinib was proved to induce apoptosis to endothelial cells, a fact that supports imatinibs anti-angiogenic effect. Discussion: This study suggests a certain molecular profile of the endothelial cells participating in breast cancer angiogenesis. This profile may be a possible molecular target in the future. Our findings suggest that in breast cancer the disease progresses via local immunosuppression, a fact that seems to be different from the thesis that inflammation is necessary for the primary tumor to progress and disseminate. It seems that breast cancer may support its own angiogenesis. To our knowledge it is the first time that TAT technology is applied to inhibit tumor angiogenesis. Our results are though very primitive and further experimentation is imperative in the aim of clarifying clinical applicability and efficiency. Finally our results suggest imatinib as a future anti-angiogenic agent. However caution is needed in order to extract safe conclusions. The most possible way to test imatinibs anti-angiogenic action is in locoregional therapy modes. It is highly possible for imatinib to increase endothelial permeability, thus maximizing the therapeutic benefit with lower concentrations of cytotoxic drugs administered.
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Επίδραση του νεοπλασματικού περιβάλλοντοςστον αγγειακό ενδοθηλιακό φραγμό και αλλαγή της διαπερατότητας του στα κυτταροστατικά φάρμακα
