title: [Mechanisms for quercetin in prevention of lung cancer cell growth and metastasis].
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Respiration,First Affi liated Hospital, Xinxiang Medical University, Xinxiang Henan 453000, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Zhao
authors.affiliation: Pediatric Intensive Care Unit, First Affiliated Hospital, Xinxiang Medical University, Xinxiang Henan 453000, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Zhang
mesh_terms: D017209:Apoptosis; D045744:Cell Line, Tumor / Q000187:drug effects; D015536:Down-Regulation; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology*; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism*; D061965:Matrix Metalloproteinase Inhibitors / Q000494:pharmacology*; D009362:Neoplasm Metastasis; D011794:Quercetin / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000494:pharmacology; D053773:Transforming Growth Factor beta1 / Q000378:metabolism*
chemical_list: D061965:Matrix Metalloproteinase Inhibitors; D012333:RNA, Messenger; C560822:TIMP1 protein, human; D019715:Tissue Inhibitor of Metalloproteinase-1; D053773:Transforming Growth Factor beta1; D011794:Quercetin; C579270:MMP9 protein, human; D020780:Matrix Metalloproteinase 9