title: Effect of X-irradiation dose rate on the clonagenic survival of human and experimental animal hematopoietic tumor cell lines: evidence for heterogeneity.
abstract: It is a generally accepted principle of radiation biology that hematopoietic progenitor cells demonstrate dose rate independent killing by x-irradiation over the clinically relevant range for total body irradiation (TBI) (5-25 rad/min). To determine whether low dose rate (5 rad/min, or 20 rad/min) compared to conventional dose rate (200 rad/min) x-irradiation altered the clonagenic survival of leukemia and lymphoma cell lines, several permanent cell lines were studied. These included: bg/bg cl 1, mouse basophillic leukemia; LW12, [W/fu rat acute myelogenous leukemia (AML)]; and human cell lines: JY and Daudi (B-cell lymphomas); K45, (T-cell leukemia); K562, (erythroleukemia); HL60 and KG1 (monomyeloid leukemias), and U937 (human histiocytic/monocytic lymphoma). Dose rate independent killing was demonstrated at several plating densities with mouse and rat leukemia lines and all human leukemia lines tested except lines HL60 and U937. With HL60, increased plating density increased the D0 at each dose rate. This effect was not attributable to an increased plating efficiency. With line U937 there was a clear dose-rate effect with increase in D0 from 88 rad, n 4.6 at 200 rad/min, to D0 = 166, n 2.3 at 5 rad/min. The data demonstrate that some human hematopoietic tumor derived cell lines of myeloid/monocyte/macrophage lineage can exhibit atypical repair of irradiation damage in vitro. This repair may be enhanced by conditions relevant to clinical TBI including low irradiation dose-rate and cell to cell interactions by tumor cells in close proximity.
mesh_terms: D000818:Animals; D002460:Cell Line; D002470:Cell Survival / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D007938:Leukemia / Q000473:pathology*; D008223:Lymphoma / Q000473:pathology*; D051379:Mice; D014411:Neoplastic Stem Cells / Q000528:radiation effects*; D051381:Rats