EGFR and breast cancer: The ST/SC system was used to decorate the external surface of P22 WB VLP with either an epidermal growth factor receptor (EGFR) affibody (EGFRaf) or a human epidermal growth factor receptor2 (HER2) affibody (HER2af), and both ligands that can be used to target breast cancer cells by binding with its specific receptor.