The evolution of chromosomal instability in Chinese hamster cells: a changing picture?
OBJECTIVE
To investigate the kinetics of chromosomal instability induced in clones of Chinese hamster cells following X-irradiation.


METHODS
X-irradiated clones of GM10115, human-hamster hybrid cells containing a single human chromosome 4 (HC4), have been previously established. These clones were defined as unstable if they contained > or = three subpopulations of cells with unique rearrangements of HC4 as detected by FISH. Stable and unstable clones were analysed by FISH and Giemsa staining at various times post-irradiation.


RESULTS
While most of the stable clones continued to show chromosomal stability of HC4 over time, one became marginally unstable at approximately 45 population doublings post-irradiation. Clones exhibiting chromosomal instability had one of several fates. Many of the unstable clones were showed similar levels of instability over time. However, one unstable clone became stable with time in culture, while another became even more unstable over time. Cytogenetic analyses of all clones after Giemsa staining indicated that in some clones the hamster chromosomes were rearranged independent of HC4, demonstrating increased frequencies of chromatid breaks and dicentric chromosomes. The majority of the unstable clones also had higher yields of chromatid gaps.


CONCLUSIONS
These data demonstrate the dynamic nature of chromosomal instability as measured by two different cytogenetic assays.
Ponnaiya
B
B
Department of Radiation Oncology, University of California, San Francisco 94143-0750, USA. ponnaiy@itsa.ucsf.edu
Limoli
C L
CL
Corcoran
J
J
Kaplan
M I
MI
Hartmann
A
A
Morgan
W F
WF
D000818:Animals; D001399:Azure Stains / Q000378:metabolism; D016466:CHO Cells / Q000528:radiation effects*; D002470:Cell Survival / Q000528:radiation effects; D002842:Chromatids / Q000528:radiation effects; D002869:Chromosome Aberrations / Q000235:genetics; D002875:Chromosomes / Q000528:radiation effects*; D002894:Chromosomes, Human, Pair 4 / Q000528:radiation effects; D006224:Cricetinae; D006801:Humans; D006822:Hybrid Cells / Q000528:radiation effects; D017404:In Situ Hybridization, Fluorescence; D014965:X-Rays / Q000009:adverse effects
D001399:Azure Stains