title: Chronic low dose-rate radiation down-regulates transcription related to mitosis and chromosomal movement similar to acute high dose in prostate cells.
abstract: OBJECTIVE
  Despite concerns over risks from exposure to low-dose ionizing radiations encountered in the environment and workplace, the molecular consequences of these exposures, particularly at representative doses and dose-rates, remains poorly understood.
  
  
  METHODS
  Using a novel flood source construct, we performed a direct comparison of genome-wide gene expression regulations resulting from exposure of primary human prostate fibroblast cultures to acute (10 cGy and 200 cGy) and longer-term chronic (1.0-2.45 cGy cumulative over 24 h) exposures.
  
  
  RESULTS
  Expression profiling showed significant differential regulation of 396 genes with no measureable changes in the acute 10 cGy dose. However, there were 106 genes in common between samples given an acute 200 cGy dose compared to those given chronic doses, most of which were decreased and related to cell cycle or chromosomal movement in M-phase. Biological pathway analysis showed decreases in cell cycle, chromosomal movement, cell survival and DNA replication, recombination and repair as well as a predicted activation of transcriptional regulators TP53, RB1 and CDKN2A. In agreement with these results, prostate epithelial cells given 200 cGy or chronic doses displayed functional decreases in proliferation and mitotic cells.
  
  
  CONCLUSIONS
  In summary, we showed a contrast to the common observation of constant or reduced effect per unit dose as the dose (acute) was diminished, that even very low total doses delivered chronically could rival the perturbing effect of acute doses 100 times as intense. Underscored is the importance of the means of dose delivery, shown to be as important as dose size when considering biologic effect.
authors.affiliation: Center of Cancer Systems Biology, GeneSys Research Institute (GRI)/Tufts University School of Medicine , Boston.
authors.forename: J Tyson
authors.initials: JT
authors.lastname: McDonald
authors.forename: Christine
authors.initials: C
authors.lastname: Briggs
authors.forename: Heather
authors.initials: H
authors.lastname: Szelag
authors.forename: Michael
authors.initials: M
authors.lastname: Peluso
authors.forename: Douglas
authors.initials: D
authors.lastname: Schneider
authors.forename: Aleksandr
authors.initials: A
authors.lastname: Perepletchikov
authors.forename: Giannoula Lakka
authors.initials: GL
authors.lastname: Klement
authors.forename: Ingolf
authors.initials: I
authors.lastname: Tuerk
authors.forename: Lynn
authors.initials: L
authors.lastname: Hlatky
mesh_terms: D000465:Algorithms; D002453:Cell Cycle / Q000528:radiation effects; D049109:Cell Proliferation / Q000528:radiation effects; D002470:Cell Survival / Q000528:radiation effects; D002875:Chromosomes / Q000528:radiation effects*; D004261:DNA Replication / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D015536:Down-Regulation / Q000528:radiation effects*; D005347:Fibroblasts / Q000378:metabolism / Q000528:radiation effects*; D020869:Gene Expression Profiling; D055106:Genome-Wide Association Study; D006801:Humans; D008297:Male; D008938:Mitosis / Q000528:radiation effects*; D020411:Oligonucleotide Array Sequence Analysis; D011467:Prostate / Q000166:cytology / Q000528:radiation effects*; D011839:Radiation, Ionizing; D011995:Recombination, Genetic / Q000528:radiation effects