Therapy of advanced established murine breast cancer with a recombinant adenoviral ErbB-2/neu vaccine.

ErbB-2 (HER-2/neu) is a transforming oncogene expressed by a substantial fraction of breast cancers, and monoclonal antibody therapy directed toward this antigen is an established treatment modality. However, not all tumors respond, and with a monoclonal antibody directed to a single epitope, there is always the risk of tumor escape. Furthermore, passive antibody therapy requires continual treatment. Whereas cancer vaccines have prevented the growth of tumors, it has been far more difficult to treat large established tumors. Here, we show that vaccination with a recombinant adenovirus expressing a truncated ErbB-2 antigen can cure large established subcutaneous ErbB-2-expressing breast cancers in mice, and can also cure extensive established lung metastatic disease. We also show that the mechanism of protection involves antibody-mediated blockade of ErbB-2 function, independent of Fc receptors. We conclude that a vaccine inducing antibodies to a functional oncogenic receptor could have tremendous therapeutic potential against cancers overexpressing such molecules.