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

Abstract

Purpose High levels of BCL-2 family members in colorectal carcinoma cause resistance to treatment. Inhibition of NANOG or its paralog NANOGP8 reduces the proliferation, stemness, and tumorigenicity of colorectal carcinoma cells. Our hypothesis was that inhibition of NANOG/NANOGP8 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. Experimental Design Lentiviral vector (LV) shRNA to NANOG (shNG-1) or NANOGP8 (shNp8-1) transduced colorectal carcinoma cells that were also exposed to the BH3 mimetics ABT-737 or ABT-199 in vivo in colorectal carcinoma xenografts and in vitro where proliferation, protein and gene expression, and apoptosis were measured. Results Clone A and CX-1 were sensitive to ABT-737 and ABT-199 at IC50s of 2 to 9 μmol/L but LS174T was resistant with IC50s 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 in vivo compared with untreated controls or treatment with only LV shRNA or ABT-737. Conclusions Inhibition of NANOGP8 or NANOG 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.

MCL-1 Depletion Impairs DNA Double-Strand Break Repair and Reinitiation of Stalled DNA Replication Forks

“…Inhibition of MCL-1 sensitizes cancer cells to chemotherapeutic drugs and IR (12,(14)(15)(16). Consistent with the current literature, we found that MCL-1 depletion ( Fig.…”

WITHDRAWN: Overexpression of miR-382 sensitizes hepatocellular carcinoma cells to γδ T cells through inhibiting the expression of c-FLIP

“…High level of c-FLIP may protect cancer cells from the apoptotic signaling exists in circumstance. Therefore, reducing the expression of c-FLIP in tumor cells is able to improve the sensitivity of them to drugs [29,30]. In this study, we demonstrated that overexpression of c-FLIP in HCC can be abolished by miR-382 introduction.…”

BCR signaling inhibitors differ in their ability to overcome Mcl-1–mediated resistance of CLL B cells to ABT-199

“…Interestingly, although Mcl-1 had previously been shown to confer resistance to ABT-737 and ABT-199 in other hematological malignancies and solid tumors, 10,[18][19][20]43,44 its role in mediating resistance in CLL had remained somewhat controversial. For example, in the study of Vogler et al, 15 induction of Mcl-1 expression by stimulation with interleukin-4 or interferon-g was associated with only marginal protection, prompting the authors to conclude that resistance to ABT-737 in CLL is largely Mcl-1 independent.…”

“…17 Previous studies by our group have shown that sustained engagement of the BCR induces Mcl-1, 6 and high levels of Mcl-1 were shown to inversely correlate with treatment response in the phase 1 study of ABT-263 in CLL. 12 In addition, high levels of Mcl-1 have been shown to protect other hematological malignancies and certain solid tumors from ABT-199, [18][19][20] suggesting that Mcl-1 could also confer ABT-199 resistance to CLL cells. To further explore this possibility, we evaluated whether BCR-induced Mcl-1 overexpression can protect CLL cells from ABT-199 and whether this protection can be overcome by available BCR signaling inhibitors.…”