Apoptotic pathways induced by low-dose radiation. (A) An RT-MLPA quantification of 27 apoptotic regulators was performed on the preradiation and postradiation samples of the 15 patients. SNRs between preradiation and postradiation samples were calculated and compared with the SNRs obtained by microarray. Genes significantly increased based on MLPA data are named. (B) Immunostainings for cleaved caspase-9 (intrinsic apoptotic pathway) and cleaved caspase-8 (extrinsic apoptotic pathway) were performed on preradiation and postradiation samples. Number of apoptotic cell clusters were counted for each sample (mean of 3 representative high-power fields). Mean and SEM are shown for each groups. Differences between preradiation and postradiation samples were highly significant for both stainings (P < .001, unpaired Mann-Whitney test). n for cleaved caspase-8 before = 17, after = 18; n for cleaved caspase-9 before = 17, after = 17.