Luteolin supplementation modulates mammary tumor growth in C3H mice fed diet with high- and low-fat content

In this study we investigated the effects of luteolin supplementation (0.05% w/w) on mammary tumor growth in C3H mice, a strain of mouse mammary tumor virus negative, fed either high-fat (45% fat of energy) or low-fat diet (15% fat of energy). Animals (n = 12/group) were allocated into 4 experimental groups (low-fat diet, low-fat diet + luteolin supplementation, high-fat diet, high-fat diet + luteolin supplementation). Experimental diet were fed for 13 wk and 7,12-dimethylbenz[a]anthracene was administered once a week for 6 wk starting at Week 1 to induce mammary tumors. Study results showed that animals on low-fat diet supplemented with luteolin exhibited longer tumor latency and lower tumor weights and sizes compared to the other groups. Animals fed high-fat diet showed increased serum IGF-1 levels and the elevated mammary tissue expression of Ki-67, IRS-1, pp38, Cdk4, and Cdk6. Luteolin inhibited IRS-1, Cdk4, and Cdk6 expression in high-fat fed animals. The expression of pp38, cyclinD1, and Bcl-xL was suppressed by luteolin supplementation both in the low-fat and high-fat diet groups. These results suggest that excess energy supply increases the risk of mammary tumor formation and luteolin suppresses tumor formation regardless of dietary fat content through its cell cycle regulatory and proapoptotic activity.