Abstract 496: Adaptive response to chronic oxidative stress involves epithelial-mesenchymal transition in MCF-7 breast cancer cells

Abstract

Abstract Though the increased oxidative stress by endogenous and exogenous factors has been hypothesized as a potential mechanism for breast cancer growth and progression, but there is no direct mechanistic evidence for adaptation to ROS-induced toxicity by the breast cancer cells. Therefore the objective of this study was to evaluate effects of chronic oxidative stress on the growth, survival and tumorigenicity of MCF-7 breast cancer cells. MCF-7 cells were exposed to hydrogen peroxide (H202) induced oxidative stress for both acute (48 hrs) and chronic (3 months) period. Cell growth and viability were evaluated by cell count and MTT assay and were confirmed by cell cycle analysis. Expression of genes related to cell cycle, cell survival, and metastasis were measured by quantitative real-time PCR. Effect of oxidative stress on tumorigenic phenotype was determined in-vitro by soft agar assay. Results of cell count, MTT and cell cycle analysis revealed increased growth, and survival of MCF-7 cells that was chronically exposed to H2O2. This was further confirmed at molecular level by increased expression of cell cycle and cell survival genes, whereas down-regulation of apoptotic genes. Chronic oxidative stress also increased tumorigenic phenotype and metastatic potential of MCF-7 cells as revealed by increase in soft agar grown colonies and expression of metastasis related genes. Additionally, fibroblast-like appearance with down regulation of epithelial markers, whereas up-regulation of mesenchymal markers in cells with chronic exposure to oxidative stress further suggest that adaptation to chronic oxidative stress by MCF-7 cells involves epithelial to mesenchymal transition (EMT). Dysregulation of epigenetic regulatory genes expression also suggest potential role of epigenetic mechanism in increased survival and tumorigencity of breast cancer cells.The findings of this study for the first time provided direct evidence for involvement EMT and epigenetic changes in adaptation of MCF-7 breast cancer cells to chronic oxidative stress. Results of this study are also highly significant in understanding the mechanism for acquired resistance to chemotherapeutic drugs that are known to produce ROS in breast cancer cells. Citation Format: Prathap Kumar S. Mahalingaiah, Logeswari Ponnusamy, Kamaleshwar P. Singh. Adaptive response to chronic oxidative stress involves epithelial-mesenchymal transition in MCF-7 breast cancer cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 496. doi:10.1158/1538-7445.AM2014-496