prostates, suggesting a role for androgens in tumor progression. However, castration shortly after prostate morphogenesis did not prevent tumor development, suggesting an androgen-independent phenotype. Tumors

We previously reported that a transgemc mouse line containing the fetal globin promoter linked to the SV4O T antigen (T Ag) viral oncogene (G71f-15) resulted in prostate tumors. In this study, we further explored tumor origin, frequency, invasiveness, androgen sensitivity, and gene expression pattern. T Ag was detected in adult but not fetal and neonatal prostates, suggesting a role for androgens in tumor progression. However, castration shortly after prostate morphogenesis did not prevent tumor development, suggesting an androgen-independent phenotype. Tumors originated within ventral or dorsal prostate lobes and involved intraepi thelial neoplasia, rapid growth in the pelvic region, and metastasis to lymph nodes and distant sites. In addition, the primary cancers could be propagated in nude mice or nontransgenic mice. Seventy-five percent of hemizygous and 100% of homozygous transgenic males developed pros tate tumors, suggesting a T Ag dosage effect. Biochemical characterization of advanced tumors revealed markers of both neuroendocrine and epi thelial phenotypes; markers of terminal differentiation are lost early in tumorigenesis. Tumor suppressor genes (p53 and Rb), normally bound to T Ag, were up-regulated; bcl-2 proto-oncogene, which prevents apoptosis, was slightly up-regulated. Myc, a stimulus to cell cycle progression, was unchanged. We propose the Gy/T-15 transgenic line as a model of highly aggressive androgen-independent metastatic prostate carcinoma with fea tat-es similar to end-stage prostate cancer in humans.