AMPK activation overcomes anti-EGFR antibody resistance induced by KRAS mutation in colorectal cancer

Background Colorectal cancer (CRC) is associated with resistance to anti-epidermal growth factor receptor (EGFR) antibodies (both acquired and intrinsic), owing to the amplification or mutation of theKRASoncogene. However, the mechanism underlying this resistance is incompletely understood. Methods DLD1 cells with WT (+/-) orKRASG13D mutant allele were treated with different concentrations of Cetuximab (Cet) or panitumumab (Pab) to study the mechanism underlying theKRASmutation-induced resistance to anti-EGFR antibodies. The function of AMPK inKRASmutation-induced resistance to anti-EGFR antibodies in CRC cells, and the regulatory role of Bcl-2 family proteins in DLD1 cells with WT or mutatedKRASupon AMPK activation were investigated. In addition, xenograft tumor models with the nude mouse using DLD1 cells with WT or mutatedKRASwere established to examine the effects of AMPK activation onKRASmutation-mediated anti-EGFR antibody resistance. Results Higher levels of AMPK activity in CRC cells with wild-typeKRAStreated with anti-EGFR antibody resulted in apoptosis induction. In contrast, CRC cells with mutatedKRASshowed lower AMP-activated protein kinase (AMPK) activity and decreased sensitivity to the inhibitory effect of anti-EGFR antibody. CRC cells with mutatedKRASshowed high levels of glycolysis and produced an excessive amount of ATP, which suppressed AMPK activation. The knockdown of AMPK expression in CRC cells with WTKRASproduced similar effects to those observed in cells with mutatedKRASand decreased their sensitivity to cetuximab. On the contrary, the activation of AMPK by metformin (Met) or 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) could overcome theKRAS-induced resistance to the anti-EGFR antibody in vivo and in vitro. The activation of AMPK resulted in the inhibition of myeloid cell leukemia 1 (Mcl-1) translation through the suppression of the mammalian target of rapamycin (mTOR) pathway. Conclusion The results established herein indicate that targeting AMPK is a potentially promising and effective CRC treatment strategy.