title: Melatonin inhibits the Migration of Colon Cancer RKO cells by Down-regulating Myosin Light Chain Kinase Expression through Cross-talk with p38 MAPK.
abstract: BACKGROUND
  Melatonin, which is mainly produced by the pineal gland, has a good inhibitory effect on cell growth of multiple cancer types. However, the underlying molecular mechanisms of anti-tumor activity for colon cancer have not been fully elucidated. In this study, we investigated the effects of melatonin on migration in human colon cancer RKO cells and the potential molecular mechanisms.
  
  
  METHODS
  The viability of RKO cells was investigated by MTT assay after treatment with melatonin, SB203580 (p38 inhibitor) and phorbol 12-myristate 13-acetate (PMA, MAPK activator) alone or in combination for 48h. The effects of melatonin, and ML-7, a selective inhibitor of myosin light chain kinase (MLCK), and SB203580, and PMA on the migration of RKO cells were analyzed by in vitro scratch-wound assay. The relative mRNA levels of MLCK was assessed by real-time quantitative RT-PCR. Western blotting analysis was performed to examine the expression of MLCK, phosphorylation of myosin light chain (pMLC) and p38 (pp38).
  
  
  RESULTS
  The proliferation and migration of human colon cancer RKO cells were inhibited significantly after treatment with melatonin. The expression levels of MLCK and phosphorylation of MLC of RKO cells were reduced, and real-time quantitative RT-PCR showed that melatonin had significant effects on suppressing the expression of MLCK. Furthermore, the phosphorylation level of p38, which showed the same trend, was also reduced when cells were treated by melatonin. In addition, ML-7 (25umol/l) could down-regulate the phosphorylation of p38.
  
  
  CONCLUSIONS
  Melatonin could inhibit the proliferation and migration of RKO cells, and further experiments confirmed that p38 MAPK plays an important role in regulating melatonin-induced migration inhibition through down-regulating the expression and activity of MLCK.
authors: Laboratory of Molecular Biology and Department of Biochemistry, the First Affiliated Hospital of Anhui Medical University, Anhui Medical University, Hefei, Anhui, China E-mail : wangyuan@ahmu.edu.cn and shenghuahrl@163.com.
authors: Duo-Bing
authors: DB
authors: Zou
authors: Xiao
authors: X
authors: Wei
authors: Ruo-Lei
authors: RL
authors: Hu
authors: Xiao-Ping
authors: XP
authors: Yang
authors: Li
authors: L
authors: Zuo
authors: Su-Mei
authors: SM
authors: Zhang
authors: Hua-Qing
authors: HQ
authors: Zhu
authors: Qing
authors: Q
authors: Zhou
authors: Shu-Yu
authors: SY
authors: Gui
authors: Yuan
authors: Y
authors: Wang
mesh_terms: D000975:Antioxidants / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D002465:Cell Movement / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology*; D015536:Down-Regulation; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D008550:Melatonin / Q000494:pharmacology*; D009219:Myosin-Light-Chain Kinase / Q000037:antagonists & inhibitors*; D010766:Phosphorylation / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors*
chemical_list: D000975:Antioxidants; D012333:RNA, Messenger; D009219:Myosin-Light-Chain Kinase; D048051:p38 Mitogen-Activated Protein Kinases; D008550:Melatonin