MET and hepatocellular carcinoma: CD44+ cells demonstrated enhanced sphere-forming ability and tumorigenicity and were found in sorafenib-resistant HCC cell lines,17 whereas knockdown of CD44 could suppress HCC tumorigenicity.18 The co-expression of c-Met and CD44 in CD44+ HCC cells facilitated the maintenance of c-Met-induced stemness phenotypes.18 Furthermore, CD44+CD133+ cells had enhanced sphere-forming ability, and this population of cells was induced by maternal embryonic leucine zipper kinase, which was overexpressed in HCC samples and associated with poorer recurrence-free survival.19