As trastuzumab is a monoclonal antibody that binds to the surfaces of HER2-overexpressing cancer cells, it has been postulated that ADCC may play an important role in the mechanism of action of this drug (Cooley et al, 1999; Clynes et al, 2000; Carson et al, 2001; Repka et al, 2003; Gennari et al, 2004). Here, ERBB2 is linked to cancer.