title: Centrosome hyperamplification and chromosomal damage after exposure to radiation.
abstract: OBJECTIVE
  In order to elucidate the effects of radiation on centrosome hyperamplification (CH), we examined the centrosome duplication cycle in KK47 bladder cancer cells following irradiation.
  
  
  METHODS
  KK47 cells were irradiated with various doses of radiation and were examined for CH immunostaining for gamma-tubulin.
  
  
  RESULTS
  Nearly all control cells contained one or two centrosomes, and mitotic cells displayed typical bipolar spindles. The centrosome replication cycle is well regulated in KK47. Twenty-four hours after 5-Gy irradiation, approximately 80% of irradiated cells were arrested in G2 phase, and at 48 h after irradiation, 56.9% of cells contained more than two centrosomes. Laser scanning cytometry performed 48 h after irradiation showed the following two pathways: (1) unequal distribution of chromosomes to daughter cells, or (2) failure to undergo cytokinesis, resulting in polyploidy. With mitotic collection, M-phase cells with CH could be divided into G1 cells with micronuclei and polyploidal cells. Fluorescence in situ hybridization analysis showed clear signs of chromosomal instability (CIN) at 48 h after irradiation. The present study had two major findings: (1) continual duplication of centrosomes occurred in the cell cycle-arrested cells upon irradiation, leading to centrosome amplification; (2) cytokinesis failure was due to aberrant mitotic spindle formation caused by the presence of amplified centrosomes. Abnormal mitosis with amplified centrosomes was detected in the accumulating G2/M population after irradiation, showing that this amplification of centrosomes was not caused by failure to undergo cytokinesis, but rather that abnormal mitosis resulting from amplification of centrosomes leads to cytokinesis block.
  
  
  CONCLUSIONS
  These results suggest that CH is a critical event leading to CIN following exposure to radiation.
authors.affiliation: Department of Urology, Kanazawa Medical University, Daigaku Uchinada, Ishikawa, Japan. kawamura@kanazawa-med.ac.jp
authors.forename: K
authors.initials: K
authors.lastname: Kawamura
authors.forename: K
authors.initials: K
authors.lastname: Fujikawa-Yamamoto
authors.forename: M
authors.initials: M
authors.lastname: Ozaki
authors.forename: K
authors.initials: K
authors.lastname: Iwabuchi
authors.forename: H
authors.initials: H
authors.lastname: Nakashima
authors.forename: C
authors.initials: C
authors.lastname: Domiki
authors.forename: N
authors.initials: N
authors.lastname: Morita
authors.forename: M
authors.initials: M
authors.lastname: Inoue
authors.forename: K
authors.initials: K
authors.lastname: Tokunaga
authors.forename: N
authors.initials: N
authors.lastname: Shiba
authors.forename: R
authors.initials: R
authors.lastname: Ikeda
authors.forename: K
authors.initials: K
authors.lastname: Suzuki
mesh_terms: D015153:Blotting, Western; D045744:Cell Line, Tumor / Q000528:radiation effects; D018385:Centrosome / Q000528:radiation effects*; D043171:Chromosomal Instability / Q000528:radiation effects*; D005784:Gene Amplification / Q000528:radiation effects*; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D020287:In Situ Nick-End Labeling; D047569:Laser Scanning Cytometry; D008938:Mitosis / Q000528:radiation effects*; D011123:Polyploidy; D014404:Tubulin / Q000032:analysis; D001749:Urinary Bladder Neoplasms / Q000737:chemistry / Q000235:genetics* / Q000532:radiotherapy*
chemical_list: D014404:Tubulin