High-LET radiation induces apoptosis in lymphoblastoid cell lines derived from atazia-telangiectasia patients.
OBJECTIVE
To investigate and compare the propensity of Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines (LCL), derived from ataxia-telangiectasia (A-T) patients and from unaffected healthy individuals (controls), to undergo apoptosis after exposure to high-linear energy transfer (LET) radiation.


METHODS
Four A-T (ARO, BMA, CSA and RJO) and two control (JAC and KKB3) LCL were exposed to doses of up to 4Gy of accelerated nitrogen ions (32-45 MeV/u, 8-12Gy/min). For comparative purposes X-ray irradiation (1.36 Gy/min) was also performed. The induction of apoptosis was studied 0-48 h after irradiation with the use of two methods: (1) monitoring of high molecular weight (HMW) DNA fragments by field inversion pulse gel electrophoresis (FIGE); and (2) morphological characterization ofapoptotic cells after fluorescent staining. In parallel, cell-cycle distribution, monitored by DNA flow cytometry, as well as measurements of p53/p21(WAF1) protein levels by Western blots, were investigated in these cells.


RESULTS
High-LET radiation-induced apoptosis and G2/M-arrest in both A-T and control LCL. No significant increase in the amount of p53/p21(WAF1) proteins preceded apoptosis in control or in A-T LCL after high-LET irradiation. However, low-LET radiation did induce significant enhanced levels of p53 proteins in control but not in A-T LCL.


CONCLUSIONS
LCL from both A-T homozygous and unaffected healthy individuals undergo apoptosis without accumulation of p53/p21(WAF1) proteins after exposure to high-LET radiation. In contrast, low-LET radiation induces apoptosis and significantly increases levels of p53 protein in control but not in A-T LCL.
Unit of Medical Radiation Biology, Cancer Centre Karolinska R8:00, Karolinska Hospital, Stockholm, Sweden.
A E
AE
Meijer
J
J
Ekedahl
B
B
Joseph
J
J
Castro
M
M
Harms-Ringdahl
B
B
Zhivotovsky
R
R
Lewensohn
D017209:Apoptosis / Q000528:radiation effects*; D001260:Ataxia Telangiectasia; D002453:Cell Cycle / Q000528:radiation effects; D002461:Cell Line, Transformed; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000096:biosynthesis; D053938:DNA Fragmentation / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D020450:Heavy Ions; D006801:Humans; D018499:Linear Energy Transfer; D008214:Lymphocytes / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects*; D009584:Nitrogen; D010315:Particle Accelerators; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis; D014965:X-Rays
C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D016159:Tumor Suppressor Protein p53; D009584:Nitrogen