Dietary Lutein from Marigold Extract Inhibits Mammary Tumor Development in BALB/c Mice

Abstract

High levels of dietary lutein can inhibit mammary tumor growth in mice. However, the antitumor effect of low levels of dietary lutein on mammary tumors is unavailable. Female BALB/c mice and the WAZ-2T (−SA) mammary tumor cell line were used in two experiments. A preliminary tumor cell dose titration study (Experiment 1) was designed to determine the inoculation dose to produce ∼65% tumor incidence. Mice (n = 10/dose) were inoculated with 0 to 1 × 106 tumor cells in the right inguinal mammary fat pad. A tumor cell load of 2.5 × 103 cells/inoculation produced ∼65% tumor incidence. This dose was used in a subsequent study (Experiment 2) of the efficacy of dietary lutein against mammary tumor development. Mice (n = 20/treatment) were fed a semisynthetic diet containing 0, 0.002, 0.02, 0.2 or 0.4% lutein from marigold extract. After 14 d, all mice were inoculated with 2.5 × 103 tumor cells, and tumor growth was measured daily for 70 d at which time blood, liver, spleen and tumors were obtained. Lutein + zeaxanthin uptake increased dose-dependently (P < 0.05) with dietary lutein levels from 0 to 0.02% (spleen) or 0.2% (plasma, liver and tumor). Low levels (0.002 and 0.02%) of dietary lutein lowered (P < 0.05) mammary tumor incidence, tumor growth and lipid peroxidation, and increased tumor latency, whereas higher dietary levels (0.2 or 0.4%) were less effective. Therefore, very low amounts of dietary lutein (0.002%) can efficiently decrease mammary tumor development and growth in mice.