Abstract 339: Inhibition of NANOG/NANOGP8 downregulates MCL-1 in colorectal cancer (CRC) cells, enhances the efficacy of BH3 mimetics and inhibits clonogenicity

Abstract

Abstract Combining lentiviral (LV) delivered shRNA against NANOG (shNG-1) or NANOGP8 (shNp8-1) with BH3 mimetics (ABT-737 and ABT-199) was undertaken to determine whether inhibition of NANOG/NANOGP8 enhances the cytotoxic effect of these BH3 mimetics in Colorectal Cancer (CRC) cells. NANOG is a key transcription factor important for both pluripotency in embryonic stem cells and malignant transformation and progression of colorectal carcinoma (CRC). Inhibition of NANOG or its paralog NANOGP8 reduces the proliferation, stemness and tumorigenicity of CRC cells. The cytotoxic potential of ABT-737 or ABT-199, as single agents, was tested in the CRC cell lines- Clone A, CX-1 and LS174T that have high levels of anti-apoptotic BCL-2 family proteins. Treatment with ABT-737 or ABT-199 showed variable cytotoxicity in the three CRC lines with LS174T being the most resistant. Inhibition of NANOG and NANOGP8 with LVshNG-1 or LVshNp8-1 in these cell lines decreased expression of MCL-1. The combination of LVshNG-1 and/or LVshNp8-1, with ABT-737 produced enhanced killing of the CRC cells by caspase-dependent apoptosis. These results were were confirmed when LV shNG-1 or LV shNp8-1 was used in combination with ABT-199. siRNA targeting MCL-1 reproduced the effects of NANOG/NANOGP8 inhibition. The CRC cells that survived the combination treatment showed lower regrowth potential and reduced clonogenicity when re-plated in fresh media. These results demonstrate that inhibition of NANOGP8 or NANOG enhances the cytotoxicity of BH3 mimetics that target BCL-2 family members through inhibition of MCL-1 expression. Citation Format: Abid R. Mattoo, Jingyu Zhang, Luis A. Espinoza, Snorri S. Thorgeirsson, J. M. Jessup. Inhibition of NANOG/NANOGP8 downregulates MCL-1 in colorectal cancer (CRC) cells, enhances the efficacy of BH3 mimetics and inhibits clonogenicity. [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 339. doi:10.1158/1538-7445.AM2014-339