Loss of p53 function leads to metastasis in ras+myc-initiated mouse prostate cancer.

To study the interactions between dominantly acting oncogenes and tumor suppressor genes we used p53 'knockout' mouse urogenital sinus tissue for retroviral transduction of ras and myc in the mouse prostate reconstitution (MPR) model system. Epithelial hyperplasia was observed in all wild-type p53 MPRs with one small focal cancer and no evidence of metastasis. Prostatic cancer was found in 100% of the heterozygous and homozygous p53 mutant MPRs with metastatic deposits in 95% of the mice. The pattern of metastasis was remarkably similar to that in human prostate cancer with gross metastatic deposits in the lung, lymph nodes, bone and liver of many animals. Progression of carcinomas in the ras+myc-initiated heterozygous p53 mutant MPRs was invariably associated with either complete loss, partial deletion or loss of expression of the wild-type p53 allele. Southern blotting analysis of proviral-cellular DNA junction fragments in primary carcinomas and cell lines derived from metastatic deposits revealed that metastases do not necessarily seed out from the most abundant clone in the primary carcinoma.