[Mechanisms for quercetin in prevention of lung cancer cell growth and metastasis].
To study the effect of quercetin, an inhibitor of matrix metalloproteinases 9 (MMP-9), on the growth and metastasis of lung cancer cells and the underlying mechanisms. We evaluated the inhibitory effect and the inhibitory kinetics of quercetin on MMP-9 by ELISA and enzyme inhibition kinetics, and the inhibitory effect of quercetin on the growth of lung cancer cell (A549) by MTT. The effect of quercetin on levels of MMP-9 (mRNA and protein) and TGF-β1 (protein) in A549 were measured by RT-PCR and Western blot, respectively. The synergistic inhibition effect of quercetin plus TIMP-1 on the growth of lung cancer cell A549 was discussed. Quercetin induced the apoptosis of A549. It was a reversible competitive inhibitor of MMP-9 (half inhibition rate IC50 of 5.25 μmol/L, inhibition constant Ki was 2.18 μmol/L). With the increase in quercetin concentration, the levels of MMP-9 (mRNA and protein) and TGF-β1 (protein) were decreased, and the number of tumor cells on wear filter membrane was reduced. The combination of quercetin (at low concentrations) with TIMP-1 showed synergistic inhibitory effect on the growth of A549 cells. Quercetin is a competitive inhibitor of MMP-9 and could downregulate the expression of MMP-9 and TGF-β1, which plays an important role in A549 apoptosis.