Fasting-refeeding stimulates the development of mammary tumors induced by 7,12-dimethylbenz[a]anthracene

The effect of fasting-refeeding during the promotion phase of dimethylbenz[a]anthracene (DMBA)-induced mammary carcinogenesis has been investigated. Female Sprague-Dawley rats were given 130 mg/kg of DMBA and divided into four groups: Group 1 was fed ad libitum; Group 2 was fed ad libitum and, in addition, received daily subcutaneous injections of beta-estradiol and haloperidol for eight days, beginning two weeks after DMBA administration; Group 3 was exposed to three days of fasting one week after carcinogen injection, then fed ad libitum until the end of the experiment; Group 4 was treated as Group 2, except the animals were fasted for three days beginning one week after DMBA administration. Treatment with beta-estradiol and haloperidol enhanced the development of DMBA-induced mammary tumors. Rats fasted after DMBA administration showed increased genesis and growth and reduced latency of mammary tumors. Fasting before beta-estradiol and haloperidol injection resulted in a more pronounced effect on tumor yield and latency than hormones or fasting alone. The data indicate that, in rats fasted during the promotion phase, tumor growth is enhanced and the permissive effects of hormones on mammary carcinogenesis are potentiated.