Abstract 2290: Rational targeting of inhibitor of apoptosis proteins (IAPs) for effective therapy of colorectal cancer

Abstract

Abstract Background Inhibitor of Apoptosis Proteins (IAPs) are anti-apoptotic proteins which suppress the activation of caspases. IAP proteins have been shown to be overexpressed in several cancers, including colorectal cancer and correlate with poor prognosis. SMAC mimetics are a class of apoptosis inducing drugs that target IAPs by mimicking the N-terminal IAP-binding motif of SMAC. Colorectal cancer has a pro-inflammatory microenvironment with high levels of TNFα. The aims of this study were to assess the efficacy of SMAC mimetic treatment in colorectal cancer. Methods Colorectal cell lines were treated with SMAC mimetics and cell viability was determined using MTT assays. Apoptosis was assessed by Western blotting for caspase activation and PARP cleavage and Flow Cytometry using Annexin V/PI staining. Protein-protein interactions were assessed using co-immunoprecipitation experiments. The pro-inflammatory microenvironment was modelled by addition of exogenous TNFα and also media transfer from and direct co-cultures with macrophages (THP-1, monocytic cell line). Results Colorectal cell lines were resistant to SMAC mimetic treatment alone unless co-cultured with TNFα. Pretreatment of colorectal cancer cells with 5-FU and oxaliplatin sensitised the cells to SMAC mimetic treatment. THP-1 cells were found to secrete soluble TNFα and media transfer experiments and also co-culture with colorectal cell lines, sensitised the cancer cells to SMAC mimetic mediated cell death. Cell death under these conditions was found to be dependent on soluble TNFα through the utilisation of neutralising antibodies. Conclusion Our results to date suggest that the pro-inflammatory microenvironment of colorectal cancer could be exploited to target overexpressed IAP proteins leading to cell death. Citation Format: Nyree T. Crawford, Philip D. Dunne, Patrick G. Johnston, David J. Waugh, Daniel B. Longley. Rational targeting of inhibitor of apoptosis proteins (IAPs) for effective therapy of colorectal cancer. [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 2290. doi:10.1158/1538-7445.AM2014-2290