Lack of Modifying Effects of 4-n-Octylphenol on 3,2′-Dimethyl-4-aminobiphenyl-Induced Prostate Carcinogenesis in Rats

The modifying effects of dietary feeding of an estrogenic compound 4-n-octylphenol on 3,2′-dimethyl-4-aminobiphenyl (DMAB) induced prostatic carcinogenesis were investigated in male F344 rats. The authors also assessed the effects of test compound on proliferating cell nuclear antigen (PCNA) index in induced neoplasms, hyperplastic lesions, and nonlesional glands in the prostrate. Rats were given intraperitoneal injections of DMAB (25 mg/kg body wt) every other week, 10 times, to induce prostatic neoplasms. They also received the experimental diet containing 10 or 100 ppm 4-n-octylphenol for 20 weeks, starting one week after the last dosing of DMAB. DMAB exposure produced prostatic adenocarcinoma with an incidence of 21% at the end of the study (Week 39). Dietary administration of 4-n-octylphenol did not affect the incidence of prostatic adenocarcinoma: 17% in DMAB→10 ppm 4-n-octylphenol group; and 12% in DMAB→100 ppm 4-n-octylphenol group. The PCNA indices in adenocarcinomas, hyperplastic lesions, and nonlesional glands in rats treated with DMAB and 4-n-octylphenol were slightly lower than that of the DMAB alone group, but the differences were not statistically significant. These results might suggest that dietary feeding of the weak estrogenic compound 4-n-octylphenol did not have modulating effects on DMAB-induced rat prostatic carcinogenesis.