In order to determine whether the establishment of robust anti-tumor immune response before breast cancer has become clinically detected could fully protect the host from tumor growth or distant tumor dormancy, we used FVB mice that are parental strain of FVBN202 transgenic mice, and harbor pre-existing T cell responses against a foreign antigen, rat neu protein expressed in MMC [30, 36]. This evidence concerns the gene ERBB2 and breast cancer.