CD44 and cancer: The pathogenic role of cancer-specific isoforms has been extensively demonstrated across all aspects of cellular physiology, including cellular adhesion and metastasis (CD44 and RON), cell growth and tumorigenesis (PKM2, MDM2, FGFR2, CRK, NUMB), cell cycle (PYK), angiogenesis (VEGF), apoptosis (GS3KB, CD95, Bcl-X, caspase-2, caspase-9), metabolism (PK), and drug resistance (AR and MRP-1) [20]–[24].