Dietary Carcinogen 2-Amino-1-Methyl-6-Phenylimidazo-[4,5-b]Pyridine-Induced Prostate Carcinogenesis in CYP1A-Humanized Mice

To develop a relevant mouse model for prostate cancer prevention research, we administered a dietary carcinogen, 2-amino-1-methyl-6-phenylimidazo[4,5-b] pyridine (PhIP), to CYP1A-humanized mice. In comparison with mouse C gamma p1a2, human CYP1A2 preferentially activates PhIP to a proximate carcinogen. Following a single oral dose of PhIP (200 mg/kg body weight), we observed inflammation, atrophy of acini, low-grade prostatic intraepithelial neoplasia (PIN; after 20 weeks), and high-grade PIN (HgPIN; after 30 to 50 weeks) in dorsolateral, ventral, and coagulating anterior prostate glands of these mice. These lesions were androgen receptor positive and featured the loss of expression of the basal cell marker p63 and the tumor suppressor PTEN. Similar to human prostate carcinogenesis, glutathione S-transferase P1 (GSTP1) expression was lost or partially lost in HgPIN. E-Cadherin expression was also lost in HgPIN. The expression of DNA methyltransferase 1 was elevated, possibly to enhance promoter hypermethylation for the silencing of GSTP1 and E-cadherin. Prostate carcinogenesis was promoted by a high-fat stress diet, resulting in HgPIN that developed earlier and in advanced lesions displayed features consistent with carcinoma in situ. This dietary carcinogen-induced prostate cancer model, recapitulating important features of early human prostate carcinogenesis, constitutes a new experimental system for prostate cancer research. Cancer Prev Res; 5(7); 963-72. (C) 2012 AACR.