Effect of the beta-diketones diferuloylmethane (curcumin) and dibenzoylmethane on rat mammary DNA adducts and tumors induced by 7,12-dimethylbenz[a]anthracene.

Curcumin is a beta-diketone constituent of the spice turmeric that possesses anticarcinogenic properties in several animal models. The present studies were conducted in order to identify beta-diketones structurally-related to curcumin that would be effective dietary blocking agents toward the initiation stage of 7,12-dimethylbenz[a]anthracene (DMBA)-induced rat mammary carcinogenesis. Of the beta-diketone compounds initially screened for their capacity to induce quinone-reductase (QR) activity in wild-type Hepa1c1c7 cells and a mutant subclone, curcumin (diferuloylmethane) and dibenzoylmethane were most effective. However, when added to semipurified diets fed to female rats, dibenzoylmethane (1%), but not curcumin (1%), was effective in inhibiting in vivo mammary DMBA-DNA adduct formation. This inhibitory effect on mammary adduct formation was associated with a significant increase in liver activities of glutathione S-transferase, QR and 7-ethoxyresorufin-O-deethylase activities. Female rats provided diets supplemented with dibenzoylmethane at 0.1, 0.5 and 1.0% for 14 days prior to dosing with DMBA exhibited a significant decrease in mammary tumor development, compared with controls. However, tumor development for animals fed diets containing 1.0% curcumin was not different from that of controls. Therefore, dibenzoylmethane, and possibly other structurally-related beta-diketones, warrant examination as breast cancer chemopreventative blocking agents.