Abstract 2445: Epigenetic modulation of tumor cell tolerance to chemotherapy

Cancer represents a set of diseases that are dynamic and heterogeneous. Their cells are phenotypically and genetically different from each other and, exhibit stochastic fluctuations in their phenotype. Investigations of isogenic populations of tumor cells reveal that tolerance also may emerge through non-genetic mechanisms, often through stochastic fluctuations in key factors in response to drugs. The objective of this work is to measure the dynamics of chemotherapy tolerance phenotype and modulate these dynamics in tumor cells to potentiate the therapy. Glioma cell lines and primary gliomas were plated at low density and after the formation of colonies, cells were treated with Temozolomide (TMZ) for 3 days. Growth rate of individual colonies was measured and the variance of growth rate of colonies with the same size was used to determine the dynamics of the phenotype. We developed a method to measure the dynamics of phenotype called DynaFit and defined a proportion of phenotypic chance in fitness until generation 6 called rCoDyFF (relative Colony DynaFit Factor 6), which is a value between 0% (stable phenotype) and 100% (dynamic phenotype). The untreated glioma cell lines (U251 and A172) and primary gliomas (LS12 and LS17) had rCoDyFF6 of 40%, 33%, 41%, 33% and treatment with 50uM TMZ produced an rCoDyFF6 67% in U251 cells. However, when cells were treated with a combination of epigenetic modulators and chemotherapy agent, 0.5µM Saha plus 3µM Azacytidine, and 50µM TMZ, the rCoDyFF6 result in - 23%, showing a drastic reduction, indicating stabilization of the phenotype. This treatment also increases sensitivity to TMZ. The result demonstrates that epigenetic modulators were able to induce a phenotypically stable state in U251 cells, leading to the copy of the tolerance phenotype of the colony founder cell to all the cells in the colony. Here we showed tumor cells fluctuate their fitness levels in the absence or presence of chemotherapy and this fluctuations can be stabilized by the inhibition of chromatin and DNA modifying enzymes. Citation Format: Jephesson Alex Alex dos Santos, Carolina Nunes Santo, Luiza Cherobini Pereira. Epigenetic modulation of tumor cell tolerance to chemotherapy [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 2445.