Abstract
Abstract BACKGROUND: TNF is a dual role cytokine involved both in cell death and survival that is expressed in the tumor microenvironment. However, little is known about the molecular events that mark the biological outcomes of such opposite biological events. Recently, the protein kinase RIP1 has been identified as a new intermediate involved in the responses activated after DNA damage induction. PURPOSE: In this study we investigated how TNF modulates the sensitivity to SN38 in colon cancer cell lines. We focused further on HT29- and HCT116-derived cell lines in which RIP1 or RIP3 proteins expression were stably downregulated. RESULTS: We found that TNF increases cellular sensitivity to different chemotherapeutic drugs under both normoxic and hypoxic conditions over a panel of different colon adenocarcinoma cell lines. Combinations with SN38 were highly synergistic. In HT29 and HCT116 cell lines (TNF resistant and TNF sensitive respectively), we analyzed this interaction by studying P-H2-AX induction, cell proliferation (clonogenic assays and BrdU incorporation) and cell cycle distribution. To study the role of RIP1 and RIP3 on the biological responses triggered by SN38, HT29- and HCT116-derived cell lines expressing low levels of RIP1 and RIP3 were analyzed. While knockdown of RIP3 had no effect on SN38 cytotoxicity, RIP1 down regulation produced a 2.5-fold increased resistance to SN38 under hypoxic conditions. This change in SN38 sensitivity also correlated with a reduction in the levels of P-H2-AX in the presence of TNF, suggesting dependence of DNA damage induction by SN38 on RIP1. CONCLUSIONS: These data suggest that RIP1 may be a key intermediate in determining cell death following SN38 treatment. Additional studies in tumor samples are in progress. Citation Format: Lucia Cabal-Hierro, Peter J. O'Dwyer. RIP1-mediated sensitivity to SN38 induced by TNF in colon adenocarcinoma cell lines. [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 2274. doi:10.1158/1538-7445.AM2014-2274
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