Prediction of radiosensitivity by measurement of X-ray induced apoptosis in human blood using the comet assay.
BACKGROUND: The aim of this work was to determine whether levels of radiation-induced apoptosis in human peripheral leukocytes could be used as a predictor of radiosensitivity. MATERIALS AND METHODS: Peripheral blood was obtained from venous blood and exposed to 0-3 Gy of X-rays. Apoptosis levels were measured at 4, 24, 48 and 72 hours after exposure using the neutral comet assay. Intra-individual apoptotic response was measured using repeated blood samples from four healthy individuals. Inter-individual variation was investigated in whole blood, granulocytes and mononuclear cells from 8 radiotherapy patients (4 demonstrating a radiosensitive response and 4 demonstrating a normal response to radiation exposures). RESULTS: Amongst the four healthy individuals there was both inter- and intra-individual variation of about the same magnitude. However, when comparing the apoptotic response of the radiosensitive and normal patients, consistent trends were observed at all X-ray doses for all of the patients. CONCLUSION: This indicates that apoptosis has some potential as a predictive assay, however, large intra-individual variation exists. More studies are required to investigate the causes of intra-individual variation and how it might be minimized.