Functional expression of the angiotensin II type 1 receptor in human ovarian carcinoma cells and its blockade therapy resulting in suppression of tumor invasion, angiogenesis, and peritoneal dissemination.

Angiotensin II is a bioactive peptide of the renin-angiotensin system, acting not only as a vasoconstrictor but also as a growth promoter via angiotensin II type 1 receptors (AT1R). The present study examined AT1R expression in human ovarian carcinoma and attempted to determine whether AT1R blocker could suppress the tumor progression. Expression of AT1R, vascular endothelial growth factor (VEGF), and CD34 was immunohistochemically analyzed in ovarian tumor tissues (n=99). Effects of AT1R blocker on invasive potential and VEGF secretion in ovarian cancer cells were examined in vitro. Effects of AT1R blocker in vivo were evaluated in a mouse model of peritoneal carcinomatosis. AT1R was expressed in 57 of 67 (85%) invasive ovarian adenocarcinomas and 12 of 18 (66%) borderline malignant tumors but in only 2 of 14 (14%) benign cystadenomas. In invasive carcinomas, VEGF expression intensity and intratumor microvessel density were significantly higher in cases that were strongly positive for AT1R (n = 37) compared with those in cases weakly positive (n = 20) or negative (n = 10) for AT1R. Angiotensin II significantly enhanced the invasive potential and VEGF secretion in AT1R-positive SKOV-3 ovarian cancer cells, both of which were completely inhibited by the AT1R blocker candesartan. Administration of candesartan into SKOV-3-transplanted athymic mice resulted in the reduction of peritoneal dissemination, decreased ascitic VEGF concentration, and suppression of tumor angiogenesis. AT1R is functionally expressed in ovarian carcinoma and involved in tumor progression and angiogenesis. AT1R blockade therapy may become a novel and promising strategy for ovarian cancer treatment.