title: Accumulation of DNA damage and cell death after fractionated irradiation.
abstract: The purpose of this work was to determine how fractionated radiation used in the treatment of tumors affects the ability of cancer as well as normal cells to repair induced DNA double-strand breaks (DSBs) and how cells that have lost this ability die. Lymphocytic leukemia cells (MOLT4) were used as an experimental model, and the results were compared to those for normal cell types. The results show that cancer and normal cells were mostly unable to repair all DSBs before the next radiation dose induced new DNA damage. Accumulation of DSBs was observed in normal human fibroblasts and healthy lymphocytes irradiated in vitro after the second radiation dose. The lymphocytic leukemia cells irradiated with 4 × 1 Gy and a single dose of 4 Gy had very similar survival; however, there was a big difference between human fibroblasts irradiated with 4 × 1.5 Gy and a single dose of 6 Gy. These results suggest that exponentially growing lymphocytic leukemia cells, similar to rapidly proliferating tumors, are not very sensitive to fraction size, in contrast to the more slowly growing fibroblasts and most late-responding (radiation therapy dose-limiting) normal tissues, which have a low proliferation index.
authors: Department of Medical Biochemistry, Faculty of Medicine in Hradec Králové, Charles University in Prague, Czech Republic.
authors: Martina
authors: M
authors: Rezáčová
authors: Gabriela
authors: G
authors: Rudolfová
authors: Aleš
authors: A
authors: Tichý
authors: Alena
authors: A
authors: Bačíková
authors: Darina
authors: D
authors: Mutná
authors: Radim
authors: R
authors: Havelek
authors: Jiřina
authors: J
authors: Vávrová
authors: Karel
authors: K
authors: Odrážka
authors: Emilie
authors: E
authors: Lukášová
authors: Stanislav
authors: S
authors: Kozubek
mesh_terms: D017209:Apoptosis / Q000528:radiation effects*; D049109:Cell Proliferation / Q000528:radiation effects; D016922:Cellular Senescence / Q000528:radiation effects; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair; D019583:Dose Fractionation, Radiation; D005347:Fibroblasts / Q000502:physiology / Q000528:radiation effects; D006801:Humans; D007945:Leukemia, Lymphoid / Q000532:radiotherapy; D008214:Lymphocytes / Q000528:radiation effects / Q000648:ultrastructure; D014407:Tumor Cells, Cultured