title: Luteolin reduces the invasive potential of malignant melanoma cells by targeting β3 integrin and the epithelial-mesenchymal transition.
abstract: OBJECTIVE
  To investigate whether luteolin, a highly prevalent flavonoid, reverses the effects of epithelial-mesenchymal transition (EMT) in vitro and in vivo and to determine the mechanisms underlying this reversal.
  
  
  METHODS
  Murine malignant melanoma B16F10 cells were exposed to 1% O(2) for 24 h. Cellular mobility and adhesion were assessed using Boyden chamber transwell assay and cell adhesion assay, respectively. EMT-related proteins, such as E-cadherin and N-cadherin, were examined using Western blotting. Female C57BL/6 mice (6 to 8 weeks old) were injected with B16F10 cells (1×10(6) cells in 0.2 mL per mouse) via the lateral tail vein. The mice were treated with luteolin (10 or 20 mg/kg, ip) daily for 23 d. On the 23rd day after tumor injection, the mice were sacrificed, and the lungs were collected, and metastatic foci in the lung surfaces were photographed. Tissue sections were analyzed with immunohistochemistry and HE staining.
  
  
  RESULTS
  Hypoxia changed the morphology of B16F10 cells in vitro from the cobblestone-like to mesenchymal-like strips, which was accompanied by increased cellular adhesion and invasion. Luteolin (5-50 μmol/L) suppressed the hypoxia-induced changes in the cells in a dose-dependent manner. Hypoxia significantly decreased the expression of E-cadherin while increased the expression of N-cadherin in the cells (indicating the occurrence of EMT-like transformation), which was reversed by luteolin (5 μmol/L). In B16F10 cells, luteolin up-regulated E-cadherin at least partly via inhibiting the β3 integrin/FAK signal pathway. In experimental metastasis model mice, treatment with luteolin (10 or 20 mg/kg) reduced metastatic colonization in the lungs by 50%. Furthermore, the treatment increased the expression of E-cadherin while reduced the expression of vimentin and β3 integrin in the tumor tissues.
  
  
  CONCLUSIONS
  Luteolin inhibits the hypoxia-induced EMT in malignant melanoma cells both in vitro and in vivo via the regulation of β3 integrin, suggesting that luteolin may be applied as a potential anticancer chemopreventative and chemotherapeutic agent.
authors.affiliation: Department of Clinical Pharmacy, College of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, China.
authors.forename: Jun-Shan
authors.initials: JS
authors.lastname: Ruan
authors.forename: Yu-Ping
authors.initials: YP
authors.lastname: Liu
authors.forename: Lei
authors.initials: L
authors.lastname: Zhang
authors.forename: Ling-Geng
authors.initials: LG
authors.lastname: Yan
authors.forename: Fang-Tian
authors.initials: FT
authors.lastname: Fan
authors.forename: Cun-Si
authors.initials: CS
authors.lastname: Shen
authors.forename: Ai-Yun
authors.initials: AY
authors.lastname: Wang
authors.forename: Shi-Zhong
authors.initials: SZ
authors.lastname: Zheng
authors.forename: Shao-Ming
authors.initials: SM
authors.lastname: Wang
authors.forename: Yin
authors.initials: Y
authors.lastname: Lu
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D015153:Blotting, Western; D015820:Cadherins / Q000096:biosynthesis; D002448:Cell Adhesion / Q000187:drug effects; D018929:Cell Culture Techniques; D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D058750:Epithelial-Mesenchymal Transition / Q000187:drug effects*; D005260:Female; D007150:Immunohistochemistry; D039661:Integrin beta3 / Q000378:metabolism*; D008175:Lung Neoplasms / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control* / Q000556:secondary; D047311:Luteolin / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D008546:Melanoma, Experimental / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology / Q000556:secondary; D051379:Mice; D008810:Mice, Inbred C57BL; D009361:Neoplasm Invasiveness
chemical_list: D000970:Antineoplastic Agents; D015820:Cadherins; D039661:Integrin beta3; D047311:Luteolin