title: Distinct signaling pathways after higher or lower doses of radiation in three closely related human lymphoblast cell lines.
abstract: OBJECTIVE
  The tumor suppressor p53 plays an essential role in cellular responses to DNA damage caused by ionizing radiation; therefore, this study aims to further explore the role that p53 plays at different doses of radiation.
  
  
  METHODS
  The global cellular responses to higher-dose (10 Gy) and lower dose (iso-survival dose, i.e., the respective D0 levels) radiation were analyzed using microarrays in three human lymphoblast cell lines with different p53 status: TK6 (wild-type p53), NH32 (p53-null), and WTK1 (mutant p53). Total RNAs were extracted from cells harvested at 0, 1, 3, 6, 9, and 24 h after higher and lower dose radiation exposures. Template-based clustering, hierarchical clustering, and principle component analysis were applied to examine the transcriptional profiles.
  
  
  RESULTS
  Differential expression profiles between 10 Gy and iso-survival radiation in cells with different p53 status were observed. Moreover, distinct gene expression patterns were exhibited among these three cells after 10 Gy radiation treatment, but similar transcriptional responses were observed in TK6 and NH32 cells treated with iso-survival radiation.
  
  
  CONCLUSIONS
  After 10 Gy radiation exposure, the p53 signaling pathway played an important role in TK6, whereas the NFkB signaling pathway appeared to replace the role of p53 in WTK1. In contrast, after iso-survival radiation treatment, E2F4 seemed to play a dominant role independent of p53 status. This study dissected the impacts of p53, NFkB and E2F4 in response to higher or lower doses of gamma-irradiation.
authors.affiliation: Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, Taiwan.
authors.forename: Tzu-Pin
authors.initials: TP
authors.lastname: Lu
authors.forename: Liang-Chuan
authors.initials: LC
authors.lastname: Lai
authors.forename: Be-I
authors.initials: BI
authors.lastname: Lin
authors.forename: Li-Han
authors.initials: LH
authors.lastname: Chen
authors.forename: Tzu-Hung
authors.initials: TH
authors.lastname: Hsiao
authors.forename: Howard L
authors.initials: HL
authors.lastname: Liber
authors.forename: John A
authors.initials: JA
authors.lastname: Cook
authors.forename: James B
authors.initials: JB
authors.lastname: Mitchell
authors.forename: Mong-Hsun
authors.initials: MH
authors.lastname: Tsai
authors.forename: Eric Y
authors.initials: EY
authors.lastname: Chuang
mesh_terms: D002460:Cell Line; D004249:DNA Damage; D004307:Dose-Response Relationship, Radiation; D050704:E2F4 Transcription Factor / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation / Q000528:radiation effects; D020868:Gene Silencing; D016158:Genes, p53 / Q000502:physiology / Q000528:radiation effects*; D006801:Humans; D008214:Lymphocytes / Q000378:metabolism / Q000528:radiation effects*; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D012313:RNA / Q000302:isolation & purification; D015398:Signal Transduction / Q000235:genetics / Q000528:radiation effects; D015533:Transcriptional Activation / Q000235:genetics / Q000528:radiation effects; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*
chemical_list: D050704:E2F4 Transcription Factor; C493762:E2F4 protein, human; D016328:NF-kappa B; D016159:Tumor Suppressor Protein p53; D012313:RNA