Expression of SV40 early genes coding for large T-antigen (LT) and small t-antigen (st) drives mammary carcinogenesis by mimicking a variety of genetic alterations commonly seen in human breast carcinomas, like abrogation of the pRB-controlled G1-checkpoint [22], and inactivation of the tumor suppressor p53 [23]. The gene discussed is TP53; the disease is breast carcinoma.