title: Chromosome aberrations in normal human fibroblasts analyzed in G0/G1 and G2/M phases after exposure in G0 to radiation with different linear energy transfer (LET).
abstract: We have studied the induction of chromosome aberrations in human fibroblasts exposed in G0/G1 to X-rays or heavy ions to study the influence of G1 cell cycle arrest. Confluent normal fibroblasts were exposed to X-rays or accelerated particles with different LET values and chromosome aberrations were investigated in the first G0/G1 and G2//M phase. The particles used here were 490MeV/nucleon Si, 500MeV/nucleon Fe, and 200MeV/nucleon Fe ions. Cells were subcultured 24h after exposure and premature chromosome condensation (PCC) was performed by fusion-induced method for analysis of G0/G1 cells, and chemically-induced method for analysis of G2 and metaphase cells. Chromosome damage was assessed in chromosomes 1 and 3 using whole chromosome fluorescence in situ hybridization (FISH). Cell cycle was analyzed by flow cytometry at different incubation times following subculture. After irradiation with 2Gy of high-LET particles, the yields of chromosome aberrations and fragments were significantly higher in G0/G1 phase than in G2/M phase, whereas similar yields of damage were measured in both phases after exposure to X-rays. In contrast, the yield of misrepair, assessed by the number of color junctions, was similar in the G0/G1 and G2/M phases after exposure to either X-rays or high-LET particles. The yields of chromosome aberrations, fragments, and color junctions in both the G0/G1 and the G2/M phases, increased with LET up to 200keV/μm, then decreased for 440keV/μm Fe particles. A good correlation was found between chromosome aberrations in both G0/G1 and G2/M cells and survival fractions after 2Gy of different LET radiations, although the slopes were steeper for the G0/G1 cells. Flow cytometry analysis indicated that high-LET particles induce more non cycling G0/G1 cells within 48h of subculture than X-rays, suggesting that chromosome aberrations scored at the G2/M phase may not accurately describe the true radiation effect.
authors.affiliation: Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba 263-8555, Japan.
authors.forename: Cuihua
authors.initials: C
authors.lastname: Liu
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Kawata
authors.forename: Yoshiya
authors.initials: Y
authors.lastname: Furusawa
authors.forename: Guangming
authors.initials: G
authors.lastname: Zhou
authors.forename: Kohei
authors.initials: K
authors.lastname: Inoue
authors.forename: Junichi
authors.initials: J
authors.lastname: Fukada
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Kota
authors.forename: Kerry
authors.initials: K
authors.lastname: George
authors.forename: Francis
authors.initials: F
authors.lastname: Cucinotta
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Okayasu
mesh_terms: D002453:Cell Cycle / Q000235:genetics* / Q000528:radiation effects*; D002478:Cells, Cultured; D002869:Chromosome Aberrations / Q000528:radiation effects*; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects*; D005434:Flow Cytometry; D006801:Humans; D007091:Image Processing, Computer-Assisted; D017404:In Situ Hybridization, Fluorescence; D018499:Linear Energy Transfer; D012867:Skin / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects*; D014965:X-Rays
keywords: Cell cycle arrest; Chromosome aberration; Fluorescence in situ hybridization (FISH); High-LET radiation; Premature chromosome condensation (PCC)