ERBB2 and cancer: Conjugation of nanoparticles carrying chemo-/radiotherapeutic agents to a monoclonal antibody that binds to a target expressed exclusively on tumor cells can create a guided missile for precise delivery of the toxic payloads to the tumor tissue, which will not only improve treatments but will also reduce side effects.162,163,165 Epidermal growth factor receptors (EGFR), human epidermal growth factor receptor-2 (HER2), and prostate-specific membrane antigen (PSMA) are three representative targets that have been extensively investigated in mAb-functionalized nanoparticles for cancer therapy.166