Abstract 488: Inhibition of JNK signaling sensitizes hypoxic colon cancer cells to DNA-damaging agents

Abstract

Abstract BACKGROUND: We have shown that hypoxia induces signaling through stress pathways in the HT29 colon adenocarcinoma cell line, and that modulation of signaling through MKK4/MKK7 exerts the opposite effects on oxaliplatin cytotoxicity under hypoxic conditions: higher sensitivity when MKK4 function is impaired and higher resistance when MKK7 is down- regulated. We also observed differential effects of JNK1 and JNK2 modulation on sensitivity of hypoxic HT29 cells to oxaliplatin treatment which implied a pro-survival function for JNK1. PURPOSE: Here we investigate how modulating signaling through JNK influences the sensitivity of hypoxic HT29 cells to oxaliplatin, SN-38 and 5-FU. We used pharmacological and molecular approaches to inhibit JNK signaling and expanded the cellular model in a panel of colon cancer cell lines. Sensitivity to drugs and induction of stress pathways were investigated in 12 colon cancer cell lines of different genetic backgrounds. We also assessed cell cycle changes and cell death characteristics upon treatment. In addition to HT29-derived cell lines stably expressing dominant negative constructs for MKK4 (HTS13), MKK7 (HTM9), JNK1 (HTJ1.3) and JNK2 (HTJ2.2), we also utilized several colon cancer cell lines (HCT116, RKO1, LoVo and SW620) in which a dominant negative construct for JNK1 or JNK2 was introduced by viral delivery. RESULTS: Our data demonstrate that stress signaling through JNK is induced by hypoxia to various extent and with differing temporal characteristics in all colon cancer cell lines assessed. In HT29 cells, treatment with oxaliplatin or SN-38 alone does not cause significant activation of signaling through JNK, whereas 5-FU treatment leads to induction of this pathway. Inhibition of JNK1 renders HT29 cells more sensitive to oxaliplatin and has no effect upon SN-38 treatment, while inhibition of either isoform sensitizes hypoxic HT29 cells to 5-FU. We also show that pharmacological inhibition of JNK by CC-401 augments cytotoxicity of oxaliplatin, SN-38 and of 5-FU in hypoxic HT29 cells, with CI50 of 0.42, 0.6 and 0.63, respectively. CC-401 and SP600125 have also demonstrated synergy with chemotherapy in other colon cancer cell lines. Finally, we show that colon cancer cell lines differ in their responses to oxaliplatin when JNK1 or JNK2 are down-regulated, from no effect (HCT116, LoVo) to increased sensitivity (HT29, SW620). CONCLUSIONS: Our data demonstrate that inhibition of the JNK pathway is a plausible approach to augment the cytotoxicity of oxaliplatin in colon cancer. However, inhibition of individual isoforms presents a complicated picture. Since enhancement of oxaliplatin cytotoxicity by this approach appears to be model-specific in colon cancer, it should be undertaken following the identification of molecular markers better able to predict the outcome. Citation Format: Irina A. Vasilevskaya, Muthu Selvakumaran, Lucia Cabal-Hierro, Peter J. O'Dwyer. Inhibition of JNK signaling sensitizes hypoxic colon cancer cells to DNA-damaging agents. [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 488. doi:10.1158/1538-7445.AM2014-488