Tumour specific cell receptors which are usually exploited in targeting and delivering NPPS drugs directly into cancer cells are G-protein coupled receptors, integrins, folate receptors, transferrin receptors, ligand receptors (CD44), epidermal growth factor receptor (EGFR), fibroblast growth factors (FGFRs), sigma receptors, follicle stimulating hormone receptors, C-type lectin receptors, biotin receptors, and neuropilin receptors [4,17,21]. This evidence concerns the gene CD44 and cancer.