ERBB2 and neoplasm: Trastuzumab works in several ways: downregulation of HER2 receptor expression; inhibition of proliferation of human tumour cells that over-express HER2 protein; enhancing immune recruitment and antibody-dependent cell-mediated cytotoxicity (ADCC) against tumour cells that overexpress HER2 protein, and downregulation of angiogenesis factors.