ERBB2 and neoplasm: We have thus been able to assess the efficacy of DNA vaccines against rat and human ErbB2 by challenging wild-type mice naturally tolerant to mouse but not to rat and human ErbB2 with syngeneic tumor cells overexpressing rat or human ErbB2, by challenging mice transgenic and tolerant for rat [34,46,47] and human [45] ErbB2 with syngeneic tumor cells overexpressing rat or human ErbB2, and by evaluating the incidence and development of autochthonous mammary carcinomas in mice transgenic and tolerant for rat and human ErbB2.