Dietary quercetin inhibits proliferation of lung carcinoma cells

Regular consumption of fruits and vegetables is strongly associated with reduced risk of developing chronic diseases. It is estimated that one third of all cancer deaths in the USA could be avoided through appropriate dietary modification. Several studies have indicated that fruits, vegetables and whole grains contain significant amounts of bioactive phytochemicals that have antiproliferative and antineoplastic properties. The bioactive phytochemicals may help protect cellular systems from oxidative damage as well as reduce the risk of chronic diseases. Quercetin and other related flavonoids have been shown to inhibit carcinogen-induced tumors in rodents. In humans, the total average intake of quercetin and kaempferol is estimated at 20 mg/day and consumption of quercetin from onions and apples was inversely correlated with lung cancer risk. In this study, we report that quercetin-inhibited A549 lung carcinoma cell proliferation was associated with activation of the extracellular signal-regulated kinase (ERK). Inhibition of MEK1/2 but not PI3 kinase, p38 kinase or JNK abolished quercetin-induced apoptosis suggesting MEK-ERK activation was required to trigger apoptosis.