title: Quercetin inhibits HGF/c-Met signaling and HGF-stimulated melanoma cell migration and invasion.
abstract: BACKGROUND
  Melanoma is notorious for its propensity to metastasize, which makes treatment extremely difficult. Receptor tyrosine kinase c-Met is activated in human melanoma and is involved in melanoma progression and metastasis. Hepatocyte growth factor (HGF)-mediated activation of c-Met signaling has been suggested as a therapeutic target for melanoma metastasis. Quercetin is a dietary flavonoid that exerts anti-metastatic effect in various types of cancer including melanoma. In a previous report, we demonstrated that quercetin inhibited melanoma cell migration and invasion in vitro, and prevented melanoma cell lung metastasis in vivo. In this study, we sought to determine the involvement of HGF/c-Met signaling in the anti-metastatic action of quercetin in melanoma.
  
  
  METHODS
  Transwell chamber assay was conducted to determine the cell migratory and invasive abilities. Western blotting was performed to determine the expression levels and activities of c-Met and its downstream molecules. And immunoblotting was performed in BS(3) cross-linked cells to examine the homo-dimerization of c-Met. Quantitative real-time PCR analysis was carried out to evaluate the mRNA expression level of HGF. Transient transfection was used to overexpress PAK or FAK in cell models. Student's t-test was used in analyzing differences between two groups.
  
  
  RESULTS
  Quercetin dose-dependently suppressed HGF-stimulated melanoma cell migration and invasion. Further study indicated that quercetin inhibited c-Met phosphorylation, reduced c-Met homo-dimerization and decreased c-Met protein expression. The effect of quercetin on c-Met expression was associated with a reduced expression of fatty acid synthase. In addition, quercetin suppressed the phosphorylation of c-Met downstream molecules including Gab1 (GRB2-associated-binding protein 1), FAK (Focal Adhesion Kinase) and PAK (p21-activated kinases). More importantly, overexpression of FAK or PAK significantly reduced the inhibitory effect of quercetin on the migration of the melanoma cells.
  
  
  CONCLUSIONS
  Our findings suggest that suppression of the HGF/c-Met signaling pathway contributes to the anti-metastatic action of quercetin in melanoma.
authors.affiliation: Jockey Club School of Chinese Medicine Building, 7 Baptist University Road, Kowloon Tong, Kowloon, China. huizizheng@hotmail.com.
authors.forename: Hui-Hui
authors.initials: HH
authors.lastname: Cao
authors.affiliation: Jockey Club School of Chinese Medicine Building, 7 Baptist University Road, Kowloon Tong, Kowloon, China. brichian@hotmail.com.
authors.forename: Chi-Yan
authors.initials: CY
authors.lastname: Cheng
authors.affiliation: Jockey Club School of Chinese Medicine Building, 7 Baptist University Road, Kowloon Tong, Kowloon, China. 12467324@life.hkbu.edu.hk.
authors.forename: Tao
authors.initials: T
authors.lastname: Su
authors.affiliation: Jockey Club School of Chinese Medicine Building, 7 Baptist University Road, Kowloon Tong, Kowloon, China. 13480405@life.hkbu.edu.hk.
authors.forename: Xiu-Qiong
authors.initials: XQ
authors.lastname: Fu
authors.affiliation: Jockey Club School of Chinese Medicine Building, 7 Baptist University Road, Kowloon Tong, Kowloon, China. 14485265@life.hkbu.edu.hk.
authors.forename: Hui
authors.initials: H
authors.lastname: Guo
authors.affiliation: Jockey Club School of Chinese Medicine Building, 7 Baptist University Road, Kowloon Tong, Kowloon, China. 14485451@life.hkbu.edu.hk.
authors.forename: Ting
authors.initials: T
authors.lastname: Li
authors.affiliation: Jockey Club School of Chinese Medicine Building, 7 Baptist University Road, Kowloon Tong, Kowloon, China. anfernee@hkbu.edu.hk.
authors.forename: Anfernee Kai-Wing
authors.initials: AK
authors.lastname: Tse
authors.affiliation: Jockey Club School of Chinese Medicine Building, 7 Baptist University Road, Kowloon Tong, Kowloon, China. hykwan@hkbu.edu.hk.
authors.forename: Hiu-Yee
authors.initials: HY
authors.lastname: Kwan
authors.affiliation: Jockey Club School of Chinese Medicine Building, 7 Baptist University Road, Kowloon Tong, Kowloon, China. bcalecyu@hkbu.edu.hk.
authors.forename: Hua
authors.initials: H
authors.lastname: Yu
authors.affiliation: Jockey Club School of Chinese Medicine Building, 7 Baptist University Road, Kowloon Tong, Kowloon, China. zlyu@hkbu.edu.hk.
authors.forename: Zhi-Ling
authors.initials: ZL
authors.lastname: Yu
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects*; D004789:Enzyme Activation / Q000187:drug effects; D064429:Fatty Acid Synthases / Q000037:antagonists & inhibitors / Q000378:metabolism; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000378:metabolism; D017228:Hepatocyte Growth Factor / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D008545:Melanoma / Q000378:metabolism* / Q000473:pathology*; D009361:Neoplasm Invasiveness; D010766:Phosphorylation / Q000187:drug effects; D055503:Protein Multimerization / Q000187:drug effects; D019859:Proto-Oncogene Proteins c-met / Q000378:metabolism*; D011794:Quercetin / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects*; D054462:p21-Activated Kinases / Q000378:metabolism
chemical_list: D017228:Hepatocyte Growth Factor; D011794:Quercetin; D064429:Fatty Acid Synthases; D019859:Proto-Oncogene Proteins c-met; D051416:Focal Adhesion Protein-Tyrosine Kinases; D054462:p21-Activated Kinases