Abstract 3666: Follicle-stimulating hormone inhibits apoptosis and autophagy in ovarian cancer cells by activating survivin and Rab25

Abstract

Abstract Follicle-stimulating hormone (FSH) has been demonstrated to increase the risk of ovarian malignancy, but the mechanisms remains unclear. Our previous results showed that FSH increases the expression of VEGF through activation of survivin, which is mediated by the activation of the PI3K/AKT signaling pathway. We reported, herein, that FSH promoted ovarian cancer cells proliferation and prevented apoptosis in vitro and in vivo. FSH up-regulated the expression of survivin and down-regulated the expression of programmed cell death 6 (PDCD6) and death receptor 5 (DR5), two molecules required for apoptosis induction. Further, we have defined that the decreased expression of DR5, but not PDCD6, was mediated by survivin. We have established animal xenografts tissue arrays, the tumors from the groups with FSH treatment had higher expression of survivin and lower expression of DR5 comparing with the tumors from untreated groups, further confirming the interaction of FSH-survivin-DR5. In addition, we have demonstrated that FSH does not only inhibit apoptosis, but also inhibit autophagy. FSH inhibits autophagy by activating mTOR pathway in ovarian cancer cells under different stress conditions, including serum starvation. By Reverse Phase Protein Arrays (RPPA) analysis and western blot confirmation, we found that FSH stimulation increases the level of Rab25 in multiple ovarian cancer cells in a dose dependent manner. Rab25, a small GTPase, is found to be associated with the progression of ovarian tumor. Rab25, belongs to Rab11 supfamily, was shown to involve in endosomal recycling. To study the role of FSH-Rab25 interaction in regulating autophagy, we knocked down Rab25 expression in ES-2, Hey and SKOv3 ovarian cancer cell lines by siRNA, and examined the effects of FSH on autophagy. Rab25 knockdown increased the starvation induced autophagy through the inhibition of pAkt, while FSH administration could partly reverse the effects of Rab25 knockdown, due to the increase of Rab25 expression stimulated by FSH. Our findings indicated that Rab25 is one of the molecules regulated by FSH in ovarian cancer cells that has a novel role as a regulator in autophagy. Taken together, we have demonstrated that FSH promotes ovarian cancer development through regulating expression of survivin, Rab25, PDCD6 and DR5, which in turn regulates cell proliferation, apoptosis as well as autophagy. Further understanding the molecular mechanisms of FSH in the process of ovarian carcinogenesis and development will ultimately help developing an effective cancer prevention method, and find a novel targeted therapy for ovarian cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3666.