Introduction: The PI3K/Akt/mTOR pathway plays a central role in regulating cancer cell proliferation and survival, and activation of the PI3K/Akt/mTOR pathway is commonly seen in ovarian cancer. NVP-BEZ235 is a novel agent that targets two molecules in this pathway, PI3K and mTOR. Thus, we explored the effects of NVP-BEZ235 on proliferation in human ovarian cancer cell lines and inhibition of tumor growth in a genetically engineered mouse model of serous ovarian cancer.

Methods: Four ovarian cancer cell lines (SKOV3, ES2, HEY, IGROV1) were treated with NVP-BEZ235 (NOVARTIS Pharmaceuticals) at different concentrations for up to 72 hours and proliferation was measured using the MTT assay. Cell cycle progression was evaluated by Cellometer. Apoptosis was determined by Annexin V-FITC assay. Phosphorylated (phos)-Akt, phos-S6 were evaluated by Western blot analysis. Adhesion was assessed by ELISA assay. The K18-gT121+/;p53fl/fl;Brca1fl/fl (KpB) genetically engineered serous ovarian cancer mouse model was used for the in vivo studies. The KpB mice were subjected to a 60% calories-derived from fat in a high fat diet (HFD) versus 10% calories from fat in a low fat diet (LFD) to mimic diet-induced obesity and subsequently exposed to NVP-BEZ235 or placebo for 4 weeks.

Results: NVP-BEZ235 inhibited proliferation in all four ovarian cancer cell lines, in both a dose and time dependent manner (IC50=30 nM for SKOV3, 42 nM for ES2, 7 nM for IGROV1, 30 nM for HEY, p=0.00001). Treatment with NVP-BEZ235 resulted in G1 cell cycle arrest but failed to induce apoptosis. Western blot analysis demonstrated that NVP-BEZ235 decreased phosphorylation of both Akt and S6 within 24 hours of exposure. Cellular adhesion was decreased by 34-51% in the ovarian cancer cell lines at a dose of 50 nM (p=0.00001). In the KpB mice fed a high fat diet (obese) and treated with NVP-BEZ235, tumor weight decreased by 77% (p=0.0015) when compared with control animals. Among KpB mice fed a low fat diet (non-obese), tumor weight decreased by 59% after treatment with NVP-BEZ235 (p=0.03).

Conclusions: NVP-BEZ235 potently inhibited cell growth via G1 arrest and decreased cellular adhesion in human ovarian cancer cells. In vivo studies using the KpB mouse model found that treatment with NVP-BEZ235 inhibited tumor growth in both obese and non-obese mice, but was more efficacious in the obese mice. Given that alterations in the PI3K/Akt/mTOR parthway are common in both obeso- and onco-genesis disease processes, this may explain the enhanced effect of NVP-BEZ235 in the obese KpB mice. This work suggests that NVP-BEZ235 may be a novel chemotherapeutic agent for ovarian cancer treatment that is potentially more beneficial in the obese population.

Citation Format: Yan Zhong, Chunxiao Zhou, Victoria Lin Bae-Jump. Dual targeting of phosphoinositide 3-kinase/mammalian target of rapamycin using NVP-BEZ235 suppressed tumor growth in a genetically engineered mouse model of serous ovarian cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2181. doi:10.1158/1538-7445.AM2013-2181