We have found that polyclonal anti-HER2 antibodies (HER2-VIA) generated by vaccinating mice with an adenovirus expressing human HER2 can retard the growth of established HER2-positive human tumor xenografts in vivo, bind to HER2 at the plasma membrane, induce HER2 internalization, ubiquitination and degradation, and eventually inactivate downstream kinase Akt. This evidence concerns the gene AKT1 and neoplasm.