First, it was shown that tumor-associated macrophages (TAMs) promoted the expansion in vitro of CD44+ cells isolated from HCC primary tumors and from HCC cell lines; second, it was shown that TAMs produce IL6, which promotes the expansion of CD44+ cells and stimulates tumorigenesis; third, through blockade of IL6 signaling, it was provided evidence that IL6 was at large extent responsible for the tumor-promoting activity of TAMs [134]. Here, CD44 is linked to hepatocellular carcinoma.