CD44 and cancer: Although most inorganic based NPs and bacterial minicells are not naturally tumor-specific, many methods have been employed to achieve the tumor-homing capability of these NPs, including conjugation with an antibody targeting the GD2 antigen overexpressed on neuroblastoma cells [19], conjugation with an antibody targeting the cancer-specific antigen EGFR [16], and conjugation with HA, which targets CD44 on colon cancer cells [33].