title: Genetic and epigenetic changes in chromosomally stable and unstable progeny of irradiated cells.
abstract: Radiation induced genomic instability is a well-studied phenomenon, the underlying mechanisms of which are poorly understood. Persistent oxidative stress, mitochondrial dysfunction, elevated cytokine levels and epigenetic changes are among the mechanisms invoked in the perpetuation of the phenotype. To determine whether epigenetic aberrations affect genomic instability we measured DNA methylation, mRNA and microRNA (miR) levels in well characterized chromosomally stable and unstable clonally expanded single cell survivors of irradiation. While no changes in DNA methylation were observed for the gene promoters evaluated, increased LINE-1 methylation was observed for two unstable clones (LS12 and CS9) and decreased Alu element methylation was observed for the other two unstable clones (115 and Fe5.0-8). These relationships also manifested for mRNA and miR expression. mRNA identified for the LS12 and CS9 clones were most similar to each other (261 mRNA), while the 115 and Fe5.0-8 clones were more similar to each other, and surprisingly also similar to the two stable clones, 114 and 118 (286 mRNA among these four clones). Pathway analysis showed enrichment for pathways involved in mitochondrial function and cellular redox, themes routinely invoked in genomic instability. The commonalities between the two subgroups of clones were also observed for miR. The number of miR for which anti-correlated mRNA were identified suggests that these miR exert functional effects in each clone. The results demonstrate significant genetic and epigenetic changes in unstable cells, but similar changes are almost as equally common in chromosomally stable cells. Possible conclusions might be that the chromosomally stable clones have some other form of instability, or that some of the observed changes represent a sort of radiation signature and that other changes are related to genomic instability. Irrespective, these findings again suggest that a spectrum of changes both drive genomic instability and permit unstable cells to persist and proliferate.
authors.affiliation: Department of Radiation Oncology, University of California Irvine, Irvine, California, United States of America.
authors.forename: Janet E
authors.initials: JE
authors.lastname: Baulch
authors.affiliation: Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota, United States of America.
authors.forename: Umut
authors.initials: U
authors.lastname: Aypar
authors.affiliation: Fundamental and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington, United States of America.
authors.forename: Katrina M
authors.initials: KM
authors.lastname: Waters
authors.affiliation: Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland, United States of America.
authors.forename: Austin J
authors.initials: AJ
authors.lastname: Yang
authors.affiliation: Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, United States of America.
authors.forename: William F
authors.initials: WF
authors.lastname: Morgan
mesh_terms: D000818:Animals; D016466:CHO Cells; D002460:Cell Line; D002470:Cell Survival / Q000235:genetics / Q000528:radiation effects; D002999:Clone Cells / Q000378:metabolism / Q000528:radiation effects; D006224:Cricetinae; D003412:Cricetulus; D019175:DNA Methylation / Q000235:genetics* / Q000528:radiation effects; D057890:Epigenomics / Q000379:methods*; D020869:Gene Expression Profiling / Q000379:methods*; D042822:Genomic Instability / Q000235:genetics* / Q000528:radiation effects; D006801:Humans; D006822:Hybrid Cells; D016328:NF-kappa B / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000235:genetics; D059467:Transcriptome / Q000235:genetics* / Q000528:radiation effects
chemical_list: D016328:NF-kappa B