Differential Modulation of Specific Gene Expression Following High- and Low-LET Radiations

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Abstract
Experiments were designed to examine the effects of radiation quality on specific gene expression within the first 3 h following radiation exposure in Syrian hamster embryo (SHE) cells. Preliminary work demonstrated the induction of c-fos and .alpha.-interferon genes following exposure to low-linear-energy-transfer (low-LET) radiations (X rays or .gamma. rays). More detailed experiments revealed induction of c-fos mRNA within the first 3 h following exposure to either X rays (75 cGy) or .gamma. rays (90 cGy). We could not detect induction of c-fos following exposure of SHE cells to fission-spectrum neutrons (high-LET) from the JANUS reactor administered at either high (12 cGy/min) or low (0.5 cGy/min) dose rates. Expression of .alpha.-interferon mRNA was similarly induced by low-LET radiations but only modestly by JANUS neutrons. The induction by .gamma. rays was dose-dependent, while induction by neutrons was specific for low doses and low dose rates. These experiments demonstrate the differential gene inductive response of cells following exposure to high- and low-LET radiations. These experiments suggest that these different qualities of ionizing radiation may have different mechanisms for inducing many of the cellular consequences of radiation exposure, such as cell survival and cell transformation.