CD44 and colorectal carcinoma: One of the most common CSC prognostic markers widely reported in CRC is cluster of differentiation 44 (CD44), and multiple studies showed that CD44 activates mitogen-activated protein kinase (MAPK), phosphatidylinositol 3-kinase (PI3K)/Akt, and Wnt signaling pathways [24,25], and regulates activities of matrix metalloproteinases 7/9 (MMP7/9) to promote tumor progression and metastasis [26]; however, the molecular role of CD44 in CRC is still unclear [27,28].