Altered apoptotic profiles in irradiated patients with increased toxicity

Purpose: A retrospective study of radiation-induced apoptosis in CD4 and CD 8 T-lymphocytes, from 12 cancer patients who displayed enhanced toxicity to radiation therapy and 9 ataxia telangiectasia patients, was performed to t est for altered response compared to healthy blood-donors and normal cancer patients. Methods and Materials: Three milliliters of heparinized blood from each don or was sent via express post to the Paul Scherrer Institute (PSI) for subse quent examination. The blood was diluted 1:10 in RPMI medium, irradiated wi th 0-, 2-, or 9-Gy X-rays, and incubated for 48 h. CD4 and CD8 T-lymphocyte s were then labeled using FITC-conjugated antibodies, erythrocytes were lys ed, and the DNA stained with propidium iodide. Subsequently, cells were ana lyzed using a Becton Dickinson PACScan flow cytometer. Radiation-induced ap optosis was recognized in leukocytes as reduced DNA content attributed to a poptosis-associated changes in chromatin structure. Apoptosis was confirmed by light microscopy, electron microscopy, and by the use of commercially a vailable apoptosis detection kits (in situ nick translation and Annexin V). Data from hypersensitive individuals were compared to a standard database of 105 healthy blood-donors, and a database of 48 cancer patient blood dono rs who displayed normal toxicity to radiation therapy. To integrate radiose nsitivity results from CD4 and CD8 T-lymphocytes after 2 and 9 Gy, z-score analyses were performed. Results: A cohort of 12 hypersensitive patients was evaluated; 8 showed enh anced early toxicity, 3 showed enhanced late toxicity, and 1 showed both. T he cohort displayed less radiation-induced apoptosis (-1.8 sigma) than aver age age-matched donors. A cohort of 9 ataxia telangiectasia homozygotes dis played even less apoptosis (-3.6 sigma). Conclusion: The leukocyte apoptosis assay appears to be a useful predictor of individuals likely to display increased toxicity to radiation therapy; h owever, validation of this requires a prospective study. (C) 1999 Elsevier Science Inc.