The Role of Angiogenesis in the Persistence of Chemoresistance in Epithelial Ovarian Cancer

Objective: Chemoresistance remains a major challenge in the treatment of ovarian cancer. As part of a survival mechanism, tumor cells have been shown to release proangiogenic factors, such as vascular endothelial growth factor (VEGF), through a mechanism that involves the upregulation of hypoxia-induced factor (HIF)-1α. The objective of this study was to compare the expression of VEGF and its receptors (R1 and R2) as well as HIF-1α in chemoresistant epithelial ovarian cancer (EOC) cells to their chemosensitive counterparts and determine their impact on angiogenesis. Methods: Two human EOC cell lines, MDAH-2774 and SKOV-3, and their cisplatin- or taxotere-resistant counterparts were used. Total RNA and protein were subjected to real-time reverse transcriptase-polymerase chain reaction, immunoprecipitation/Western blot and enzyme-linked immunosorbent assay to evaluate the expression of VEGF, VEGF receptors (R1 and R2), and HIF-1α. Angiogenesis was assessed with an in vitro angiogenesis assay. Data were analyzed using independent Student t tests and chi-square. Results: Both taxotere- and cisplatin-resistant MDAH-2774 and SKOV-3 EOC cell lines manifested a significant decrease in VEGF, VEGF receptors, HIF-1α messenger RNA, and protein levels as compared to their chemosensitive counterparts. There was a significant decrease in the number and thickness of polygon blood vessel formation in chemoresistant EOC cells compared to chemosensitive counterparts. Conclusion: Cisplatin- and taxotere-resistant EOC cells are characterized by lower VEGF, VEGF receptors, and HIF-1α, and decreased angiogenesis. These findings may indicate a decrease in drug delivery at the tumor site, hence allowing the persistence of chemoresistant EOC cells.