88P - Transcription factors of snail family in the regulation of resistance of breast cancer cells to hypoxic conditions

Abstract

BackgroundIn the course of tumor growth, the cells that are far from the blood vessel are exposed to hypoxic conditions. As part of this process transcription factors (TFs) of the Snail family (Snail, Slug, Twist1, and Zeb1) are activated launching the epithelial-mesenchymal transition (EMT) program. Snail family factors are the most studied as stimulators of EMT, promoting tumor progression, migration and invasion of tumor cells. The aim of our research is to study adaptive mechanisms of human breast cancer (BC) cells to hypoxia and the analysis of the role of the TF Snail in this process. MethodsWe used human BC cells MCF-7, MDA-MB-231 and HBL-100 which were cultured in standard DMEM containing 10% fetal calf serum at 37oC and 5% СО2. For hypoxia modeling, the cells were cultured in a CO2-incubator maintaining O2 concentration at 1%. ResultsKnockdown of the Snail by small interfering RNA (siRNA) leads to increased sensitivity of breast cancer cells to hypoxia, due to increased blocking of cells in the S-phase of cell cycle. Cells were more resistant to hypoxia at a lower density, where Snail expression was increased, but further hyperexpression of Snail had not lead to increased resistance to hypoxia. Knockdown of Snail leads to an compensatory increase of Slug`s expression, while the knockdown of Twist1 and Zeb1 leads to decreased Slug expression. Knockdown of Twist1 decreases cell proliferation both in hypoxia and normoxia, through activation of cell cycle inhibitor p21WAF1, specifically in the G2/M phase, in p53-wild type HBL-100 cells. We used a chemical inhibitor of p53-Snail interaction GN25, to examine if blocking of this interaction could lead to increased sensitivity in hypoxia. We have shown that this compound has a greater cytotoxic effect in normoxia than hypoxia, due to increased Snail activity. ConclusionsModulation of Snail-associated signaling pathways is a perspective target for increase of cancer cell tolerance to chronic hypoxia, and inhibition of metastatic process in breast cancer cells. Legal entity responsible for the studyThe authors. FundingGrant no. 14.W03.31.0020 between the Ministry of Science and Education of the Russian Federation and Institute of Gene Biology, Russian Academy of Sciences. DisclosureAll authors have declared no conflicts of interest.