ERBB2 and neoplasm: Moreover, HER2 protein is considered a tumour-associated antigen (TAA) that is targeted by trastuzumab, causing anti-tumour effect through apoptosis, cell arrest induction, antibody-dependent cell-mediated cytotoxicity (ADCC), inhibition of HER2 extracellular domain shedding, and inhibition of downstream signaling [7].