CCND1 and neoplasm: To date, CD44s remains the most commonly reported isoform in cancer, but the other CD44 variants (CD44v) are also correlated with neoplasia and metastasis in some cancers (52) CD44 is a frequently observed CSC marker in solid tumors, and CD44 was revealed to be a major Wnt target, involved in the Ras-Raf-Mek-Erk-Cyclin D1 pathway, phosphoinositide 3-kinase (PI3K)-Akt signaling, and the Wnt pathway, as well as stimulating EMT, which promotes tumor invasion, progression and metastasis (53–55).