Data from Inhibition of <i>NANOG/NANOGP8</i> Downregulates MCL-1 in Colorectal Cancer Cells and Enhances the Therapeutic Efficacy of BH3 Mimetics

Abstract

<div>Abstract<p><b>Purpose:</b> High levels of BCL-2 family members in colorectal carcinoma cause resistance to treatment. Inhibition of <i>NANOG</i> or its paralog <i>NANOGP8</i> reduces the proliferation, stemness, and tumorigenicity of colorectal carcinoma cells. Our hypothesis was that inhibition of <i>NANOG/NANOGP8</i> enhances the cytotoxic effect of BH3 mimetics targeting BCL-2 family members in colorectal carcinoma cells through reducing expression of MCL-1, a prosurvival BCL-2 protein.</p><p><b>Experimental Design:</b> Lentiviral vector (LV) shRNA to <i>NANOG</i> (shNG-1) or <i>NANOGP8</i> (shNp8-1) transduced colorectal carcinoma cells that were also exposed to the BH3 mimetics ABT-737 or ABT-199 <i>in vivo</i> in colorectal carcinoma xenografts and <i>in vitro</i> where proliferation, protein and gene expression, and apoptosis were measured.</p><p><b>Results:</b> Clone A and CX-1 were sensitive to ABT-737 and ABT-199 at IC<sub>50s</sub> of 2 to 9 μmol/L but LS174T was resistant with IC<sub>50s</sub> of 18 to 30 μmol/L. Resistance was associated with high MCL-1 expression in LS174T. LVshNG-1 or LVshNp8-1 decreased MCL-1 expression, increased apoptosis, and decreased replating efficiency in colorectal carcinoma cells treated with either ABT-737 or ABT-199 compared with the effects of either BH3 mimetic alone. Inhibition or overexpression of MCL-1 alone replicated the effects of LVshNG-1 or LVshNp8-1 in increasing or decreasing the apoptosis caused with the BH3 mimetic. The combination therapy inhibited the growth of LS174T xenografts <i>in vivo</i> compared with untreated controls or treatment with only LV shRNA or ABT-737.</p><p><b>Conclusions:</b> Inhibition of <i>NANOGP8</i> or <i>NANOG</i> enhances the cytotoxicity of BH3 mimetics that target BCL-2 family members. Gene therapy targeting the NANOGs may increase the efficacy of BH3 mimetics in colorectal carcinoma. <i>Clin Cancer Res; 20(21); 5446–55. ©2014 AACR</i>.</p></div>