title: Promoter Methylation Analysis Reveals That KCNA5 Ion Channel Silencing Supports Ewing Sarcoma Cell Proliferation.
abstract: Polycomb proteins are essential regulators of gene expression in stem cells and development. They function to reversibly repress gene transcription via posttranslational modification of histones and chromatin compaction. In many human cancers, genes that are repressed by polycomb in stem cells are subject to more stable silencing via DNA methylation of promoter CpG islands. Ewing sarcoma is an aggressive bone and soft-tissue tumor that is characterized by overexpression of polycomb proteins. This study investigates the DNA methylation status of polycomb target gene promoters in Ewing sarcoma tumors and cell lines and observes that the promoters of differentiation genes are frequent targets of CpG-island DNA methylation. In addition, the promoters of ion channel genes are highly differentially methylated in Ewing sarcoma compared with nonmalignant adult tissues. Ion channels regulate a variety of biologic processes, including proliferation, and dysfunction of these channels contributes to tumor pathogenesis. In particular, reduced expression of the voltage-gated Kv1.5 channel has been implicated in tumor progression. These data show that DNA methylation of the KCNA5 promoter contributes to stable epigenetic silencing of the Kv1.5 channel. This epigenetic repression is reversed by exposure to the DNA methylation inhibitor decitabine, which inhibits Ewing sarcoma cell proliferation through mechanisms that include restoration of the Kv1.5 channel function.
  
  
  CONCLUSIONS
  This study demonstrates that promoters of ion channels are aberrantly methylated in Ewing sarcoma and that epigenetic silencing of KCNA5 contributes to tumor cell proliferation, thus providing further evidence of the importance of ion channel dysregulation to tumorigenesis.
authors.affiliation: Department of Pharmacology, University of Michigan, Ann Arbor, Michigan. Translational Oncology Program, University of Michigan, Ann Arbor, Michigan. Department of Pediatrics, University of Michigan, Ann Arbor, Michigan.
authors.forename: Katherine E
authors.initials: KE
authors.lastname: Ryland
authors.affiliation: Translational Oncology Program, University of Michigan, Ann Arbor, Michigan. Department of Pediatrics, University of Michigan, Ann Arbor, Michigan.
authors.forename: Allegra G
authors.initials: AG
authors.lastname: Hawkins
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Southern California, Los Angeles, California. Keck School of Medicine, University of Southern California, Los Angeles, California.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Weisenberger
authors.affiliation: Keck School of Medicine, University of Southern California, Los Angeles, California.
authors.forename: Vasu
authors.initials: V
authors.lastname: Punj
authors.affiliation: Department of Pediatrics, Vanderbilt University, Nashville, Tennessee.
authors.forename: Scott C
authors.initials: SC
authors.lastname: Borinstein
authors.affiliation: Van Andel Research Institute, Grand Rapids, Michigan.
authors.forename: Peter W
authors.initials: PW
authors.lastname: Laird
authors.affiliation: Department of Pharmacology and Therapeutics, University of Florida, Gainesville, Florida.
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Martens
authors.affiliation: Translational Oncology Program, University of Michigan, Ann Arbor, Michigan. Department of Pediatrics, University of Michigan, Ann Arbor, Michigan. Department of Pathology, University of Michigan, Ann Arbor, Michigan. elawlor@umich.edu.
authors.forename: Elizabeth R
authors.initials: ER
authors.lastname: Lawlor
mesh_terms: D001374:Azacitidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D001859:Bone Neoplasms / Q000235:genetics* / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D018899:CpG Islands / Q000187:drug effects; D019175:DNA Methylation / Q000187:drug effects; D000077209:Decitabine; D044127:Epigenesis, Genetic / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D051666:Kv1.5 Potassium Channel / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000187:drug effects*; D012512:Sarcoma, Ewing / Q000235:genetics* / Q000473:pathology
chemical_list: C496981:KCNA5 protein, human; D051666:Kv1.5 Potassium Channel; D000077209:Decitabine; D001374:Azacitidine