Chidamide increases the sensitivity of Non-small Cell Lung Cancer to Crizotinib by decreasing c- MET mRNA methylation.

Crizotinib is a kinase inhibitor targeting c-MET/ALK/ROS1 used as the first-line chemical for the treatment of non-small cell lung cancer (NSCLC) with mutations. Although c-MET is frequently overexpressed in 35-72% of NSCLC, most NSCLCs are primarily resistant to crizotinib treatment. A set of NSCLC cell lines were used to test the effect of chidamide on the primary crizotinib resistance and . Relationships between the synergistic effect of chidamide and c-MET expression and RNA methylation were systemically studied with a battery of molecular biological assays. We found for the first time that chidamide could sensitize the effect of crizotinib in a set of mutation-free NSCLC cell lines, especially those with high levels of c- expression. Notably, chidamide could not increase the sensitivity of NSCLC cells to crizotinib cultured in serum-free medium without hepatocyte growth factor (HGF; a c-MET ligand). In contrast, the addition of HGF into the serum-/HGF-free medium could restore the synergistic effect of chidamide. Moreover, the synergistic effect of chidamide could also be abolished either by treatment with c-MET antibody or siRNA-knockdown of c- expression. While cells with low or no c- expression were primarily resistant to chidamide-crizotinib cotreatment, enforced c- overexpression could increase the sensitivity of these cells to chidamide-crizotinib cotreatment. Furthermore, chidamide could decrease c- expression by inhibiting mRNA N6-methyladenosine (m6A) modification through the downregulation of and expression. Chidamide-crizotinib cotreatment significantly suppressed the activity of c-MET downstream molecules. Chidamide downregulated c- expression by decreasing its mRNA m6A methylation, subsequently increasing the crizotinib sensitivity of NSCLC cells in a c-MET-/HGF-dependent manner.