CD44 and gastric cancer: Metformin has been reported to suppress the expression of CSC markers, including CD44, EpCAM, EZH2, Notch-1, Nanog, and Oct4 in pancreatic cells [133]; CD44 and Sox2 in gastric cancer [110]; Nanog, c-Myc, and TLF4 in NSCLC [62]; and upregulate the expression of differentiation markers, such as Kruppel-like factor 4 (KLF4) and MUC5AC in gastric cancer [110].