CD44 and ovarian cancer: Active targeting is achieved by functionalisation of nanoparticles with targeted surface receptors that are highly expressed in tumour cells, such as human epidermal growth factor 2 (HER2), folic acid (FA), CD44 (also referred to as homing cell adhesion molecule, HCAM), or vascular endothelial growth factor (VEGF) in ovarian cancer, is a more specific strategy (Figure 3).