Epstein-Barr virus-transformed lymphoblastoid cell lines of ataxia telangiectasia patients are defective in X-ray-induced apoptosis

Abstract

Purpose: To investigate and compare the propensity of EpsteinBarr virus (EBV)-transformed lymphoblastoid cell lines (LCL) obtained from unaffected healthy individuals and ataxia telangectasia (A-T) patients to undergo apoptosis after X-ray exposure. Material and methods: The LCL were exposed to 1-4Gy X-rays at a dose-rate of 1.36Gy/min. At various post-irradiation times (0, 24, 48 and 72h) the induction of apoptosis was analysed by: (1) monitoring the formation of high molecular weight (HMW) DNA fragments by field inversion pulse gel electrophoresis (FIGE); and (2) morphological characterization of apoptotic cells after fluorescence staining. In parallel, cell-cycle distribution, monitored by DNA flow cytometry, was investigated in these cells. Results: The LCL obtained from the A-T homozygotes were resistant to undergoing radiation-induced apoptosis during the observation time used. On the contrary, LCL from unaffected healthy controls displayed significant radiation-induced chromatin fragmentation seen at 48h and 72h after irradiation. In these cells, radiation-induced G1-arrest (24h post-irradiation) preceded chromatin cleavage. In A-T LCL, the defective G1-arrest was not followed by apoptosis. Conclusions: In spite of a defective cell-cycle control, EBVtransformed LCL of A-T patients compared with unaffected healthy controls do not undergo X-ray-induced apoptosis, at least during their first post-irradiation cell cycle.