Abstract 591: Reovirus is oncolytic towards organ specific and highly metastatic lung cancer cells: Possible mechanisms of action.

Abstract Introduction: Metastasis from lung adenocarcinoma can occur rapidly to multiple organs within months of diagnosis. Despite early diagnosis and surgical removal, lung adenocarcinoma can relapse within months dispersing to other organs such as lymph nodes, contra-lateral lung, adrenal glands, the bones and the brain. Thus, there is a desperate need for novel therapeutics to target this disease. The oncolytic potential of reovirus towards lung cancer cell lines under in vitro and in vivo conditions has previously been demonstrated by us. However, reovirus's efficacy towards organ specific and highly metastatic lung cancer sublines and its oncolytic mechanism within this histology has not been elucidated yet. Here we demonstrate for the first time that reovirus has similar oncolytic potential towards parental and organ specific lung cancer cell lines and reovirus oncolyses these via apoptosis. Methods: To generate organ specific cells, H1299- luc2 cells (‘Parental’ or PAR) were introduced into the arterial circulation of athymic (nu/nu), beige (NIH-III) mice. These cells metastasized to various sites, including adrenal gland (ADR), bone (BONE), and ovary (OVA). Cells derived from metastatic lesions were harvested, expanded in vitro, and then reintroduced into NIH-III mice. When compared to the parental, cells obtained from metastatic deposits demonstrated a highly enhanced organ specificity and metastatic capacity. Parental and organ specific (ADR, BONE and OVA) cells were incubated with live (LV) or UV-inactivated (DV) reovirus at a multiplicity of infection of 40 for 24, 48, and 72 hours. Viable cell counts, apoptosis and autophagy were assayed using flow cytometry utilizing flow count beads/7-AAD, Annexin V/7-AAD and active caspase 3 and cyto ID-dye respectively. Results: Remarkably, parental and organ specific lung cancer cells (ADR, OVA, BONE) showed significant cytopathic effects with LV but not with DV treatment. A dramatic decrease in viable cell counts were seen with all cell lines (including H23 and H460) at 48 hours post virus infection and this number declined further at 72 hours. Notably, a significant increase in active caspase 3 and annexin V expression was seen in all lung cell lines with LV treatment but not with DV treatment. No difference in median channel fluorescence of cyto-ID was seen in DV or LV treated cells indicating minimal changes in autophagy. Conclusion: Given the inherent variability of the parental and organ specific cell lines in terms of expression of various metastasis related signaling molecules, it was of interest to note that reovirus had similar oncolytic activity towards them. This has important implications for the future use of reovirus as a therapeutic for metastatic lung cancer as presently two reovirus lung cancer clinical trials are underway. Currently research is underway to evaluate the in vivo efficacy of reovirus using organ specific cells. Citation Format: Chandini M. Thirukkumaran, Arvin Singla, Joanne Luider, Frank Jirik, Don Morris. Reovirus is oncolytic towards organ specific and highly metastatic lung cancer cells: Possible mechanisms of action. [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 591. doi:10.1158/1538-7445.AM2013-591