Inhibition by dietary dibenzoylmethane of mammary gland proliferation, formation of DMBA-DNA adducts in mammary glands, and mammary tumorigenesis in Sencar mice

Dibenzoylmethane (DBM) is a minor constituent of licorice and a P-diketone analogue of curcumin. Feeding 1% DBM in the diet to Sencar mice during both the initiation and the post-initiation periods strongly inhibited 7,12-dim ethylbenz[a]anthracene (DMBA)-induced mammary tumor multiplicity and mammar y tumor incidence by 97%. In further in vivo studies to elucidate the possi ble mechanisms of the inhibitory action of DBM, feeding the 1% DBM in the A IN-76A diet to immature Sencar mice for 4-5 weeks decreased the uterine wet weight by 43%, inhibited the proliferation rate of mammary gland epithelia l cells by 53%, uterine epithelium by 23%, and uterine stroma by 77%, when mice were killed during the first estrus phase of estrous cycle. In additio n, feeding 1% DBM in the diet to Sencar mice at 2 weeks before, during and 1 week after DMBA treatment (intubation of 1 mg DMBA per mouse once a week for 5 weeks) inhibited formation of total DMBA-DNA adducts in mammary gland s by 72% using a post-P-32-labeling assay. Thus, feeding 1% DBM diet to Sen car mice inhibited formation of DMBA-DNA adducts in mammary glands and lowe red the proliferation rate of the mammary gland in vivo. These results may explain the strong inhibitory actions of dietary DBM on mammary carcinogene sis in mice. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.