Genotype-dependent radiosensitivity: clonogenic survival, apoptosis and cell-cycle redistribution.
OBJECTIVE
We describe variations of three radiation-induced endpoints on the basis of cell genotype: Clonogenic survival, expression of apoptosis and cell-cycle redistribution.


METHODS
Clonogenic survival, apoptosis and cell-cycle redistribution are measured in multiple cell lines after exposure to radiation between 2 and 16 Gy. Cell lines varied in clonogenic radiosensitivity and expression of specific genes.


RESULTS
Clonal radiosensitivity is genotype-dependent, associating with four specific genes: A mutated form of Ataxia telangiectasia mutated (mutATM); with two forms of TP53, the gene that is template for tumor protein p53, wildtype TP53 (wtTP53) and mutated TP53 (mutTP53); and an unidentified gene in radioresistant glioblastoma cells. Apoptosis is also genotype-dependent showing elevated levels in cells that express mutATM and abrogated 14-3-3sigma (an isoform of the 14-3-3 gene) but less variation for different forms of TP53. Cell-cycle redistribution varied in mutATM cells. Kinetics of apoptosis are biphasic for both time and dose; cell lines did not express apoptosis at doses below 5 Gy or times before 24 hours. Kinetics of cell-cycle redistribution changed dynamically in the first 24 hours but showed little change after that time.


CONCLUSIONS
Clonogenic survival, radiation-induced apoptosis and radiation-induced redistribution in the cell-cycle vary with cell genotype, but not the same genotypes. There is temporal, not quantitative, correlation between apoptosis and clonal radiosensitivity with apoptosis suppressed by lower, less toxic doses of radiation (<5 Gy) but enabled after larger, more toxic doses. Kinetic patterns for apoptosis and redistribution show a common change at approximately 24 hours.
Williams
Jerry R
JR
Molecular Radiation Biology Laboratory, Department of Radiation Medicine, Loma Linda University Medical Center, Loma Linda, California, USA. jrwilliams_france@yahoo.com
Zhang
Yonggang
Y
Zhou
Haoming
H
Russell
James
J
Gridley
Daila S
DS
Koch
Cameron J
CJ
Little
John B
JB
D048948:14-3-3 Proteins / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D017209:Apoptosis / Q000235:genetics / Q000502:physiology / Q000528:radiation effects*; D064007:Ataxia Telangiectasia Mutated Proteins; D002453:Cell Cycle / Q000235:genetics / Q000502:physiology / Q000528:radiation effects*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D002470:Cell Survival / Q000235:genetics / Q000502:physiology / Q000528:radiation effects; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D016158:Genes, p53 / Q000235:genetics; D005838:Genotype; D005909:Glioblastoma / Q000235:genetics / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D007700:Kinetics; D009154:Mutation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D011836:Radiation Tolerance / Q000235:genetics* / Q000502:physiology; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects
D048948:14-3-3 Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases