CD44 and neoplasm: Due to an upregulation of negatively charged membrane components (e.g., O-glycosylated mucins [55,56] and heparan sulfate proteoglycans [57]) and the breakdown of membrane asymmetry (e.g., phosphatidylserine externalization [58,59]), tumour cells have an increased negative charge on their membranes, thus contributing to initial electrostatic interaction of defensins, such as HBD-2, to tumour cell surface.