Reduction of hypoxia-induced angiogenesis in ovarian cancer cells by inhibition of HIF-1 alpha gene expression

Purpose The goal of this study was to investigate the effects of silencing HIF-1 alpha gene expression with specific small interfering RNA (siRNA) on VEGF production and angiogenesis in epithelial ovarian cancer (EOC) cells. Methods Two EOC cell lines, MDAH-2774 and SKOV-3, were cultured under normoxic (20% O 2 ) and hypoxic (2% O 2 ) conditions using standard techniques. After EOC cells were transfected with siRNA, HIF-1 alpha and VEGF mRNA levels were measured by real-time RT–PCR. Angiogenesis was evaluated utilizing an in vitro assay model consisting of human umbilical vein endothelial cells (HUVEC) and polymerized ECM Matrix. Results Both EOC cell lines evaluated constitutively expressed HIF-1 alpha and VEGF mRNA. HIF-1 alpha and VEGF mRNA levels were significantly increased in response to hypoxia ( P < 0.05). Under hypoxic conditions, inhibition of HIF-1 alpha gene expression by a specific siRNA resulted in a significant reduction in HIF-1 alpha and VEGF mRNA levels ( P < 0.05). In the in vitro angiogenesis model, supernatant from the hypoxic EOC cells induced the HUVEC to form a complex tubular network, a hallmark of angiogenesis. Semi-quantitative analysis of the angiogenesis assay revealed a significant reduction in tube formation when supernatant from HIF-1 alpha siRNA-treated hypoxic EOC cell was used ( P < 0.05). Conclusion Inhibition of HIF-1 alpha expression by specific siRNA resulted in a significant decrease in VEGF production and angiogenesis. Further investigation of HIF-1 alpha inhibition for anti-tumor activity is warranted and may potentially prove HIF-1 alpha as a therapeutic target in the management ovarian cancer.