Abstract 1848: A comprehensive image cytometry method to identify and functionally characterize a rare subpopulation of platinum-induced aneuploid tumor cells in high-grade serous carcinoma

Abstract

Abstract Background: Although platinum treatment effectively reduces tumor bulk for high grade serous carcinomas of tubal-ovarian origin, there are often scattered tumor cells exhibiting reparative and aneuploid features that remained within the peritoneal cavity. The biological importance of these aneuploid cells has not been well elucidated. In this study, we used HGSC cell line models and developed an improved image cytometry approach to identify these aneuploid cells for functional interrogation. Methods: We have developed a comprehensive image cytometry approach to assess DNA ploidy and cell cycle phase distribution within a standard flow cytometry software platform and validated this methodology using phase-specific markers (EdU, pRb, Geminin, pH3). We further introduced a novel ‘brightness vs. nuclear size' scatter plot to enhance the cell cycle assessment at the single-nucleus level. The method was applied to correlate the kinetics of the DNA damage and checkpoint response with the cell cycle status and cell viability on HGSC cell lines (OVCAR3, TOV3133G) after in-vitro carboplatin treatment. Results: Using this improved image cytometry method, we identified the emergence of a rare subpopulation of large aneuploid tumor cells at 1 week after platinum treatment. These large aneuploid cells remained viable (PI- and cleaved-PARP negative) but were uniquely dependent on anti-apoptotic signaling for their continual survival. While the bulk population of treated tumor cells underwent mitotic catastrophe following premature G2-M checkpoint exit, a rare subpopulation escaped cell death likely via mitotic slippage as they exhibit characteristic features of aneuploidy. These large aneuploid cells remained KI-67 positive and clonal dilutional experiments are being performed to assess their regrowth potential. Conclusions: This study has identified a rare subpopulation of tumor cells that avoided mitotic cell death after platinum treatment and then survived in an aneuploid state. The derivation of aneuploid cells via mitotic slippage subsequent to platinum treatment is an under-recognized phenomenon but may pose as an important drug-resistant mechanism due to enhanced survival strategies co-opted by these aneuploid cells. Research funding: Ontario Institute for Cancer Research Citation Format: Yu Wing Yeung, Oliver Fung, Mikhail Bashkurov, Robert Rottapel, Andras Kapus. A comprehensive image cytometry method to identify and functionally characterize a rare subpopulation of platinum-induced aneuploid tumor cells in high-grade serous carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1848.