CD44 and neoplasm: Tumorigenic cells overexpressing P2X7 receptor show an increased tendency to metastasize,44,45 and paralleling CD44 expression is essential for the anchorage-independent growth and tumor-initiating ability of highly tumorigenic mammary epithelial.46 Notably, CD44 proteolytic cleavage serves as a tumorigenic process by enhancing the proliferation/migration of cells.47 The extracellular sCD44 proteolytically released domain affects the function of the membrane form of CD44, acting as an inhibitor of CD44-dependent cell–cell and cell–matrix interactions.48,49