Effects of bisphenol A and 17β-estradiol on vascular endothelial growth factor A and its receptor expression in the non-cancer and cancer ovarian cell lines

Abstract
Tumours secrete several pro-angiogenic factors, among which vascular endothelial growth factor (VEGF) and its receptor (VEGF-R) are the most extensively studied but not in ovarian cancer cells. The study was designed to investigate the effect of bisphenol A (BPA) (environmental oestrogen) and of 17β-estradiol (E2) (endogenous estrogen) on the gene (real-time PCR) and protein (Western blotting) expression of VEGF-R2 and VEGF-A in human non-cancer (HOSEpiC) and ovarian cancer cell lines (SKOV-3 and OVCAR-3). In addition, VEGF-A levels were measured in culture supernatants using a colorimetric assay. Cells were exposed to BPA (1, 40 and 100 nM) or 17β-estradiol (0.1, 10 and 40 nM) for 3 to 48 h. Since differential expression levels of basal oestrogen receptor (ERα and ERβ) between non-cancer and cancer cell lines may affect the response to oestrogens, receptor expression was measured both at the gene and protein levels. Basal ERβ expression was similar in all cell lines, and ERα expression was significantly higher in the SKOV-3 cell line. Basal VEGF-R2 expression was higher in cancer than non-cancer cell lines, and in contrast, VEGF-A expression was significantly lower in both SKOV-3 and OVCAR-3 cancer cell lines. Exposure of non-cancer cells to BPA and E2 was associated with a significant increase in VEGF-R2 expression but had no effect on VEGF-A expression or secretion. In contrast, exposure of cancer cells to BPA, but not E2, increased VEGF-R2 and VEGF-A expression and secretion. In conclusion, (1) BPA and E2 regulated VEGF-R2 and VEGF-A expression differently in non-cancer and cancer cells, and (2) BPA has a direct stimulatory effect on VEGF-R2 and VEGF-A expression in both, while E2 appears to be uninvolved in the regulation of VEGF-R2 and VEGF-A expression in cancer cells.