Lung cancer is the most deadly
malignancy in the US.
Chemoprevention is potentially a complementary approach to smoking cessation for
lung cancer control. Recently, we reported that a commercially available form of kava extract significantly inhibits
4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and
benzo(a)pyrene (BaP)-induced lung
tumorigenesis in A/J mice at a dose of 10 mg per gram diet. In the present study, we examined the dose-dependent lung
tumor inhibitory activities of kava and investigated potential active constituent(s). Mice treated with
carcinogen alone contained 12.1±5.8 lung
adenomas per mouse 22 weeks after final
carcinogen administration. Mice that were fed diets containing kava at dosages of 1.25, 2.5, 5, and 10 mg/g of diet had 8.4±3.5, 6.6±3.5, 4.3±2.4, and 3.8±2.3 lung
adenomas per mouse, respectively. This corresponds to a reduction of 31%, 46%, 65% and 69% in
tumor multiplicity, which were all statistically significant (p < 0.05). Analyses of lung
adenoma tissues derived from kava-treated animals revealed that kava significantly inhibited
adenoma cell proliferation while it had no detectable effect on cell death, indicating that kava primarily suppressed lung
tumorigenesis in A/J mice via inhibition of cell proliferation. Flavokawains A, B, and C, three
chalcone-based components from kava, demonstrated greatly reduced chemopreventive efficacies even at concentrations much higher than their natural abundance, suggesting that they alone were unlikely to be responsible for kava's chemopreventive activity. Kava at all dosages and treatment regimens did not induce detectable adverse effects, particularly with respect to liver. Specifically, kava treatment showed no effect on liver integrity
indicator enzymes or liver weight, indicating that kava may be potentially safe for long-term chemopreventive application.