Abstract 4889: ERa-targeted therapy in ovarian cancer cells using novel Estradiol-Platinum(II) hybrids

Abstract

Abstract Since several cancers in women are estrogen-dependent due to the presence and overexpression of estrogen receptor (ER), we sought to determine the possibility to use ER as a target for directed chemotherapy and have designed unique molecules capable of doing so. We have recently reported the synthesis of a new family of E2-platinum(II) hybrids. Previous study revealed high efficiency of these novel compounds compared to cisplatin towards breast cancer cells which were also selective towards ER+ breast cancer xenografts in nude mice. In the present study, we have investigated, in vitro and in vivo, the antitumor activity of one of the best hybrid VP-128 using ovarian cancer cell (Ovcar-3, Skov-3, A2780 and A2780CP) and investigated its mode of action and its ability to induce apoptosis and autophagy. Annexin V/PI staining using flow cytometry revealed an improved efficiency of VP-128 compared to cisplatin to induce apoptosis of ovarian cancer cells. We also transiently transfected A2780 cells with ERα gene to compare the hybrid in a similar genetic background. The presence of ER in A2780 increased apoptosis induced by VP-128 but not by cisplatin. VP-128 activity was also stronger compared to cisplatin in presence or absence of ER suggesting that the hybrid can act through different mechanisms of action. In vivo, using ovarian cancer cell xenografts in nude mice, we also found that VP-128 had improved antitumour activity compared to cisplatin, and was more specific and selective towards hormone-dependent ER+ than ER- xenografts. To examine VP-128 mechanism of action, we decided to study its ability to induce apoptosis and autophagy. We found that VP-128 induced apoptosis via caspase-dependant (caspase-9; -3 and PARP cleavage) mechanisms but also caspase-independent mechanisms such as AIF translocation to the nucleus, as revealed by Western blot of cytosolic/nuclear cell extracts and immunofluorescence microscopy in A2780(ER-). Conversely, AIF subcellular localization was not modified by VP-128 in Ovcar-3 ER+ cells. Following 8-12h of treatment with VP-128, increased formation of acidic vesicular organelles in cancer cells was observed suggesting the importance of autophagy in this process. We then found by Western blot that LC3B-I was converted to LC3B-II following VP-128 treatment suggesting formation of autophagosome. We then investigated pathways directly (mTor) or indirectly (AKT) possibly involved in the regulation of autophagy. VP-128 decreased the level of both phosphorylated/active mTor and AKT in cancer cells favouring autophagy induction. These results show that VP-128 can not only induce apoptosis but also induce autophagy in ovarian cancer cells. Altogether, this study also highlight the therapeutic value of VP-128 for the treatment of hormone-dependent ovarian cancers, and provide preliminary proof-of-concept for efficient targeting of ERα by E2-Pt(II) linked chemotherapeutic hybrids. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4889. doi:1538-7445.AM2012-4889