CD44 and colorectal cancer: Since miRNA-638 has been reported to be down-regulated to promote apoptosis and autophagy by Rh2 in several cancer cell types [18,19,20], other miRNAs may also be involved in the development of colorectal cancers, such as TGFBR1:miR-532-5P, SMAD7:miR-375, PI3KCA:miR-520a, and CD44:miR-509-3P [46].