CD44 and colorectal cancer: In addition, recent investigations on cancer stem cells are focused on examining the molecular mechanisms responsible for Wnt signaling in Apc and β-catenin mutated colorectal cancer cell organoids [61,62,63,64,65], the role of DNA repair in stem cell renewal [66], mechanisms for regulation of CD44 in stem cell proliferation [67], the role of one-carbon metabolism in cancer stem cells [68], and the role of ER-β in mammary carcinogenesis [69].