title: Melatonin enhances DNA repair capacity possibly by affecting genes involved in DNA damage responsive pathways.
abstract: BACKGROUND
  Melatonin, a hormone-like substance involved in the regulation of the circadian rhythm, has been demonstrated to protect cells against oxidative DNA damage and to inhibit tumorigenesis.
  
  
  RESULTS
  In the current study, we investigated the effect of melatonin on DNA strand breaks using the alkaline DNA comet assay in breast cancer (MCF-7) and colon cancer (HCT-15) cell lines. Our results demonstrated that cells pretreated with melatonin had significantly shorter Olive tail moments compared to non-melatonin treated cells upon mutagen (methyl methanesulfonate, MMS) exposure, indicating an increased DNA repair capacity after melatonin treatment. We further examined the genome-wide gene expression in melatonin pretreated MCF-7 cells upon carcinogen exposure and detected altered expression of many genes involved in multiple DNA damage responsive pathways. Genes exhibiting altered expression were further analyzed for functional interrelatedness using network- and pathway-based bioinformatics analysis. The top functional network was defined as having relevance for "DNA Replication, Recombination, and Repair, Gene Expression, [and] Cancer".
  
  
  CONCLUSIONS
  These findings suggest that melatonin may enhance DNA repair capacity by affecting several key genes involved in DNA damage responsive pathways.
authors.affiliation: Key Laboratory of Environmental Medicine Engineering, Ministry of Education, School of Public Health, Southeast University, Nanjing, China.
authors.forename: Ran
authors.initials: R
authors.lastname: Liu
authors.forename: Alan
authors.initials: A
authors.lastname: Fu
authors.forename: Aaron E
authors.initials: AE
authors.lastname: Hoffman
authors.forename: Tongzhang
authors.initials: T
authors.lastname: Zheng
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhu
mesh_terms: D000975:Antioxidants / Q000494:pharmacology*; D045744:Cell Line, Tumor; D020552:Comet Assay; D019295:Computational Biology; D004249:DNA Damage / Q000187:drug effects; D004260:DNA Repair / Q000187:drug effects* / Q000235:genetics; D005786:Gene Expression Regulation / Q000187:drug effects*; D053263:Gene Regulatory Networks; D006801:Humans; D061986:MCF-7 Cells; D008550:Melatonin / Q000494:pharmacology*; D008741:Methyl Methanesulfonate / Q000494:pharmacology; D020411:Oligonucleotide Array Sequence Analysis
chemical_list: D000975:Antioxidants; D008741:Methyl Methanesulfonate; D008550:Melatonin