Abstract
Abstract Background: Oncolytic viruses (OVs) represent a promising option for treatment of advanced cancers. There are few studies assessing the effects of oncolytic viruses in renal cell carcinoma. Oncolytic measles virus (MV) is a novel viral platform that previously been shown to induce cell fusion and cytotoxicity in a CD46-dependent manner. The goals of our study are to identify a pharmacological agent that used in combination with oncolytic MV will enhance the virus cytotoxic effects in renal cell carcinoma (RCC) models. Results: To achieve this goal, we performed in vitro assays combining the Edmonston strain of Measles virus expressing eGFP (MV-GFP), whose oncolytic activity in vitro and in vivo has been demonstrated, with several targeted novel agents that include a new generation multikinase inhibitor used in the treatment of RCC, bromodomain inhibitors associated with epigenetic regulation and Triptolide (T) which has been reported as an apoptosis, ER stress, and oxidative stress inducer and inhibitor of angiogenesis. 786-0 (VHL-mut), A498 (VHL mutant), Caki-1 (VHL-wt) and ACHN (VHL-wt) RCC cells were seeded and treated with oncolytic MV, and the compounds including T. Cell viability as well as cytotoxicity were quantitated at 24, 48 and 72h. Evaluation of single agent activity showed that MV and T were associated with the most significant growth inhibitory or cytotoxic effects. Among the MV-drug combinations, we found that low dose of T was associated with the most significant augmentation of MV oncolysis in RCC cell lines, demonstrated by both viability cell count and by real time monitoring of cell growth by xCELLigence based assays. We found that the treatment sequence (virus infection followed by T treatment) was an important determinant of the combined tumor cytotoxic effects. In addition to enhanced tumor cytotoxicity, we also observed that T enhanced viral replication in RCC, which may explain in part the mechanisms of drug synergy. Finally, we investigated the molecular changes associated with RCC oncolysis by MV alone and in combination with T with RPPA (Reverse Phase Protein Array) and western blot validation and enhanced viral oncolysis induced by the MV-T combination was found to be associated with increased apoptosis (PARP cleavage), ER stress induction (pEIF2a, CHOP) and down regulation of survival and proliferation pathways (pAKT) 36h post-treatment. Conclusion: We identified a novel strategy to enhance RCC viral oncolysis by MV-T combination, by mechanisms that include enhanced viral replication with subsequent increase in the cell death, ER stress pathways and down regulation of pAKT. Current efforts are focused on identifying in vivo antitumor effects and mechanisms of this combination that will open new horizons for the development of rational combinations to improve oncolytic measles virotherapies in RCC, which could lead to long term responses/cures in this disease. Citation Format: Valery A. Chavez, Natasha Khatwani, Ashok Saluja, Jaime Merchan. A novel virus-drug combination to enhance oncolysis in renal cell carcinoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4581.
