Time kinetics and reproducibility of radiation-induced apoptosis in lymphocytes from a cohort of 60 cancer patients Free

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Purpose. Evaluation of apoptosis induced in T-lymphocytes by gamma radiation in a cohort of 60 cancer patients undergoing therapy.

Methods. Blood was harvested from cancer patients via venipuncture, diluted in RPMI media, exposed to various doses of gamma radiation, and incubated to permit expression of apoptosis. Lymphocytes were stained for cell type and DNA, and analyzed using flow cytometry.

Results. Induction of apoptosis in T-lymphocytes following ionizing radiation follows a sigmoid curve. Data transformation permits frequency distributions of apoptosis induction with respect to time to be constructed. Apoptosis is expressed more rapidly after 8 Gy than 2 Gy radiation, and more rapidly in CD8 T-lymphocytes than in CD4 T-lymphocytes. After 8 Gy the most reliable data are observed at 48 h, and after 2 Gy at 72 h. The most informative data are obtained when average apoptotic yield for a cohort of patients is around 40%. Both CD4 and CD8 T-lymphocytes give reliable results.

Conclusions. Dual-laser flow cytometry and dual cell labeling is a cost and time effective method of determining radiation-induced apoptosis in peripheral blood lymphocytes. The logistic function is an appropriate model to describe time kinetics of induction of apoptosis following radiation exposure. Leukemia selectively sensitizes CD8 T-lymphocytes to radiation-induced apoptosis.