Lack of correlation between ATM protein expression and tumour cell radiosensitivity.
OBJECTIVE
Cells derived from individuals in which the ataxia telangiectasia (ATM) gene is mutated are hypersensitive to ionizing radiation. Whether differences in ATM protein levels exist among human malignant glioma cell lines and whether such differences are correlated with cellular radiosensitivity were determined.


METHODS
Polyclonal antibodies were raised to separate regions of the ATM protein. ATM protein expression in human malignant glioma cell lines, SV40 transformed normal human fibroblasts and SV40 transformed AT fibroblasts was analysed by Western blotting. Reverse transcriptase polymerase chain reaction (RT-PCR) was used to assess the presence of ATM transcript.


RESULTS
While ATM protein was detected in all cell extracts, significant differences in the level of expression were observed. There was no apparent correlation between cellular radiosensitivity and differences in ATM protein levels in these human glioma cells. Extremely low levels of ATM protein were observed in M059J cells, which provide the only example of DNA-dependent protein kinase (DNA-PKcs) deficiency in a cell line of human origin.


CONCLUSIONS
Variations in the levels of ATM protein are insufficient to explain the differences in cellular radiosensitivity observed in a panel of human malignant glioma cell lines.
Department of Biological Sciences, University of Calgary, Alberta, Canada.
D W
DW
Chan
D P
DP
Gately
S
S
Urban
A M
AM
Galloway
S P
SP
Lees-Miller
T
T
Yen
J
J
Allalunis-Turner
D001260:Ataxia Telangiectasia / Q000235:genetics*; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins; D004260:DNA Repair / Q000528:radiation effects; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins; D005720:Gamma Rays / Q000009:adverse effects; D015972:Gene Expression Regulation, Neoplastic / Q000528:radiation effects; D005910:Glioma / Q000378:metabolism; D006801:Humans; D009363:Neoplasm Proteins / Q000032:analysis / Q000528:radiation effects; D009687:Nuclear Proteins; D016133:Polymerase Chain Reaction; D017346:Protein Serine-Threonine Kinases / Q000528:radiation effects; D011506:Proteins / Q000528:radiation effects*; D012333:RNA, Messenger / Q000378:metabolism / Q000528:radiation effects; D011836:Radiation Tolerance / Q000235:genetics*; D013539:Simian virus 40 / Q000235:genetics; D014170:Transformation, Genetic / Q000235:genetics; D014407:Tumor Cells, Cultured / Q000528:radiation effects*; D025521:Tumor Suppressor Proteins
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D011506:Proteins; D012333:RNA, Messenger; D025521:Tumor Suppressor Proteins; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; D017346:Protein Serine-Threonine Kinases