Abstract 2546: IGR-1R pathway role in oxaliplatin acquired resistance in colon cancer cell lines and its regulation by MMP-7 and IGFBP-2

Abstract

Abstract Background: IGF-1R pathway and MMPs have been implicated in chemotherapy resistance in colorectal cancer. This receptor could be activated by IGF1 or IGF2 ligands, which bioavailability is regulated by IGFBPs, what could be degraded by MMPs. Objectives: To determine the basal levels and the modulation by chemotherapy (oxaliplatin), of the levels of IGF-1R, IGFBPs and MMPs in colon cancer cell lines (HT-29 (IC50: 6,46 uM) and LoVo (IC50: 0,25 uM) and their oxaliplatin resistant cell lines (HT-29OXAR3 (IC50: 29,86 uM) and LoVOXAR3 (2,45 uM)). To analyze the differences in apoptosis between parental and oxaliplatin resistant cell lines when are treated with oxaliplatin. Methods: MMP-7 levels were analyzed by RT-PCR, Western Blot and ELISA. Levels of IGF-1R, activated IGF-1R, IGFBP-2, and IGFBP-3 were determined by Western Blot and/or ELISA. Differences in cell viability were analyzed by MTT, and intrinsic (bcl-2, bax) and extrinsic (Fas, caspase 8) apoptotic pathways, by Western Blot, in parental and oxaliplatin resistant cell lines with dose-response experiments. Results: LoVo and LoVOXAR3 express low levels of MMP-7 and IGF-1R and high levels of IGFBP-2 compared with HT-29 and HT-29OXAR3. In addition, HT-29OXAR3 cells showed increased MMP-7, IGF-1R and pIGF-1R levels compared with HT-29 and lower levels of IGFBP-2. We also observed after oxaliplatin treatment in HT-29 cells a decrement of IGF-1R and IGFBP-2 and an increment in MMP-7 levels. In apoptotic experiments, FAS and caspase 8 (extrinsic pathway) were induced by oxaliplatin in LOVO (0.2 uM) and in LOVOXAR3 (20uM). Bcl-2 and bax (intrinsic pathway) were induced or decremented respectively in LOVO (2uM) and LOVOXAR3 (20uM). No changes in these extrinsic apoptotic proteins were observed in HT29 and HT29OXR3. In HT-29OXAR3 cell line higher doses of oxaliplatin (20 uM instead of 2uM) were needed to induce intrinsic apoptotic (bax) and antiapoptotic proteins (bcl-2) Conclusions: IGF-1R signalling is implicated in acquired oxaliplatin resistance and it is regulated by MMP-7 and IGFBP-2 in a different manner in our two models of cancer colon cell lines. The two apoptotic pathways were implicated in LoVo cell lines, but only intrinsic pathway regulates apoptosis in HT-29 cell lines. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2546.