Autochthonous prostate adenocarcinomas in Lobund-Wistar rats: a model system

An experimental model system for autochthonous prostate adenocarcinoma (PA) has been developed in Lobund-Wistar (L-W) rats. Large primary PAs were induced in 31 of 40 (77.5%) L-W rats within an average of 10.7 months after a single dose of methylnitrosourea (MNU) and subcutaneous implants of testosterone. Metastatic tumors had developed in over 60% of the tumor-bearing rats. In addition, localized in situ PAs had developed in 5 of the 40 test rats. At 14 months 50 untreated L-W rats were free of demonstrable PAs. Two of 20 (10%) L-W rats developed PA at 14 months after inoculation of MNU alone. Six of 42 (14%) L-W rats developed PAs within 14 months after s.c. administration of testosterone implants. Thus, testosterone acted as a tumor promoter of PA for cells that had been initiated by MNU. The manifestations of the PAs in the L-W rats resembled many aspects of the counterpart disease in man.