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内容記述 |
Purpose: The X-ray cross-complementing group 4 (XRCC4) is a key gene for DNA double-strand breaks (DSB) in the nonhomologous DNA end-joining (NHEJ) pathway (1, 2). In this study, we investigate the relationship between XRCC4 and cancer stem cell (CSC) properties and the contribution of XRCC4 to radiosensitivity. Methods: Putative CSCs sorted from HCT116-wild type (WT) and XRCC4-knock out (KO) cells were treated with or without carbon-ion beam or X-ray irradiation (IR), then the colony and spheroid formation analysis, fluorescence activated cell sorting (FACS) analysis, gammaH2AX foci immunofluorescence staining and real-time PCR assay were performed. Results: FACS analysis showed that the proportion of CSC markers CD44+ and ESA+ cells was significantly increased but CD133+ cells decreased in XRCC4 KO cells compared to that of HCT116-WT cells. The colony and spheroid formation ability of CSCs from XRCC4-KO cells were markedly decreased compared with those from HCT116-WT cells. The clonogenic assay showed that the doses at D10 for CSCs sorted from XRCC4-KO and HCT116-WT cells were 1.4 and 4.2 Gy for X-ray and 1.0 and 1.9 Gy for carbon ion beam IR, respectively. A much larger number and large-sized gamma H2AX foci were observed in CSCs sorted from XRCC4 KO cells compared to those from HCT116-WT cells, after 24 h of carbon ion beam IR compared with X-ray. Real-time PCR assay showed carbon-ion beam IR enhanced apoptosis- and autophagy-related gene expression in XRCC4 KO cells compared to HCT116-WT cells. Conclusion: Loss of XRCC4 significantly altered the properties of CSCs, rendering them radiosensitive to both carbon ion beams and X-rays, suggesting that XRCC4 may play an important role in regulating the radiosensitivity of CSCs. |
