Radiation induced apoptosis in ataxia telangiectasia homozygote, heterozygote and normal cells

Recent reports suggest that the radiation-induced, p53-dependent, apoptotic response is aberrant in ataxia telangiectasia (AT) cells. We investigated the possibility that an aberrant apoptotic response to ionizing radiation m ay also be the characteristic of AT heterozygotes and may facilitate in dis criminating AT heterozygotes from the general population. Log phase, Epstei n Barr virus (EBV) transformed lymphoblastoid cell lines and primary lympho cytes from three AT families were irradiated and the apoptotic response at 30 h post radiation was measured by flow cytometry using TUNEL and hypodipl oid methods. Our results show that the apoptotic response of AT homozygote (ATM-/-), AT heterozygote (ATM+/-) and normal cells (ATM+/+) to ionizing ra diation, measured by the hypodiploid and TUNEL methods using flow cytometry , is dose and time dependent. Furthermore, this response is paradoxical in that ATM (-/-) lymphoblastoid cells were characterized by a reduced post ra diation apoptotic response compared to their normal counterparts. Heterozyg ote (ATM+/-) lymphoblastoid cells displayed an intermediate response to ion izing radiation. In contrast, primary, non-transformed AT cells exhibited t he same apoptotic response as their normal counterparts. Our results thus i ndicate that pre-radiation, EBV-transformed, lymphoblastoid cell lines from individual families may be useful in discriminating ATM status, but patien t-derived, primary AT homozygous, heterozygous and normal primary cultured lymphocytes cannot be discriminated by this assay. (C) 2001 Elsevier Scienc e B.V. All rights reserved.