title: Decitabine-induced demethylation of 5' CpG island in GADD45A leads to apoptosis in osteosarcoma cells.
abstract: GADD45 genes are epigenetically inactivated in various types of cancer and tumor cell lines. To date, defects of the GADD45 gene family have not been implicated in osteosarcoma (OS) oncogenesis, and the role of this pathway in regulating apoptosis in this tumor is unknown. The therapeutic potential of Gadd45 in OS emerged when our previous studies showed that GADD45A was reexpressed by treatment with the demethylation drug decitabine. In this study, we analyze the OS cell lines MG63 and U2OS and show that on treatment with decitabine, a significant loss of DNA methylation of GADD45A was associated with elevated expression and induction of apoptosis. In vivo affects of decitabine treatment in mice showed that untreated control xenografts exhibited low nuclear staining for Gadd45a protein, whereas the nuclei from xenografts in decitabine-treated mice exhibited increased amounts of protein and elevated apoptosis. To show the specificity of this gene for decitabine-induced apoptosis in OS, GADD45A mRNAs were disrupted using short interference RNA, and the ability of the drug to induce apoptosis was reduced. Understanding the role of demethylation of GADD45A in reexpression of this pathway and restoration of apoptotic control is important for understanding OS oncogenesis and for more targeted therapeutic approaches.
authors.affiliation: Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada.
authors.forename: Khaldoun
authors.initials: K
authors.lastname: Al-Romaih
authors.forename: Bekim
authors.initials: B
authors.lastname: Sadikovic
authors.forename: Maisa
authors.initials: M
authors.lastname: Yoshimoto
authors.forename: Yuzhuo
authors.initials: Y
authors.lastname: Wang
authors.forename: Maria
authors.initials: M
authors.lastname: Zielenska
authors.forename: Jeremy A
authors.initials: JA
authors.lastname: Squire
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D001374:Azacitidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D015153:Blotting, Western; D001859:Bone Neoplasms / Q000235:genetics / Q000473:pathology; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D018899:CpG Islands / Q000235:genetics*; D019175:DNA Methylation / Q000187:drug effects*; D015254:DNA Modification Methylases / Q000037:antagonists & inhibitors; D000077209:Decitabine; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D007124:Immunoenzyme Techniques; D008297:Male; D051379:Mice; D008819:Mice, Nude; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D010006:Osteoblasts / Q000378:metabolism / Q000473:pathology; D012516:Osteosarcoma / Q000235:genetics* / Q000473:pathology*; D034741:RNA, Small Interfering / Q000494:pharmacology; D014183:Transplantation, Heterologous; D014407:Tumor Cells, Cultured; D000097642:GADD45 Proteins
chemical_list: D001374:Azacitidine; D018797:Cell Cycle Proteins; D015254:DNA Modification Methylases; D000077209:Decitabine; D004791:Enzyme Inhibitors; D009687:Nuclear Proteins; D034741:RNA, Small Interfering; C439070:GADD45A protein, human; D000097642:GADD45 Proteins; C499072:Gadd45a protein, mouse