PROMOTIONAL EFFECTS OF HIGH FAT DIET ON CHEMICAL CARCINOGENESIS OF PROSTATE

Abstract

The effects of a high fat diet on progression of minimal cancerous lesions to manifest ones were investigated using a chemo-endocrinical carcinogenesis model of rat prostate. Male Fischer 344 rats were alternatively given a diet containing 0.75ppm of ethinyl estradiol (EE) for 3 weeks and the basal diet without EE for the following 2 weeks, and subcutaneously administered with 3, 2′-dimethyl-4-aminobiphenyl (DMAB) at 50mg/kg body weight 2 days after the diet with EE was changed to the basal one. This sequential treatment was repeated 10 times in 50 weeks, and the animals were fed with either normal fat diet (NF) or high fat diet (HF) during the following 30 weeks. At week 80, all the rats were sacrificed for histological examination of the prostate. Atypical hyperplasia and adenocarcinoma were induced in 15.4% (4/26) and 34.6% (9/26) in the rats fed NF and 44.8% (13/29) and 20.7% (6/29) in those group fed HF, respectively. The incidence of adenocarcinoma was significantly higher in the group fed NF than in the other. However, the number of rats with either atypical hyperplasia or adenocarcinoma was not significantly different between the two groups. These observations provided no supporting evidence that high fat content in diet has enhancing effects on prostatic carcinogenesis. Using different species or strain of rats, C3H/He mice and ACI/Seg rats, additional experiments were also conducted by a slightly modified protocol without changing on fat contents. Although ACI/Seg rats were known to spontaneously develop prostate cancer, the histopathological examinations revealed atypical hyperplaisa at 25% (16/64) in mice and microadenocarcinoma at 8.1% (6/74) in rats. Apparently further studies are needed until a more useful and efficient model of prostate carcinogenesis is established.