Pleiotropic effects of quercetin on the transformation of BALB 3T3 cells

The effect of quercetin, a flavonoid, on the in vitro transformation of BALB 3T3 cells was examined. Quercetin at a low concentration (5 micrograms/ml) markedly suppressed the promoting action of 12-O-tetradecanoyl phorbol-13-acetate (TPA, 10 ng/ml) in this transformation system using 20-methylcholanthrene (MCA, 1 microgram/ml) as the initiator. At a concentration higher than 5 micrograms/ml, however, quercetin enhanced transformation by MCA. Quercetin itself was found to induce direct transformation weakly, but definitely, at a slightly higher concentration than that for enhancing MCA-induced transformation. These results indicate that quercetin has pleiotropic effects on the transformation of BALB 3T3 cells.