Inactivation of XRCC4 is associated with various human carcinogenesis. Here we report expression changes of cancer stem-like cell markers in XRCC4 deficient human colon cancer cells after X-ray or carbon ion beam. FACS analysis showed that the percentage of CD133+, CD44+ and ESA+ cells in HCT116-WT cells were 3.2%, 6.8%, and 7.2%, whereas 1.6%, 19.2% and 20% in HCT116-XRCC4 KO cells. The proportion of CD133+ and CD44+ cells was increased 3 to 4-fold after 2 Gy X-ray irradiation in HCT116-WT cells, in comparison, 4 to 6- fold increment of CD133+ and CD44+ cells was induced in HCT116-XRCC4 KO cells. There was no change in proportion of ESA+ cells in HCT116-WT cells, but 10-fold enhancement of ESA+ cells was induced in HCT116-XRCC4 KO cells after 2 Gy X-ray irradiation. Colony and spheroid formation from CD133+, CD44+/ESA+ cells were higher compared to CD133-, CD44-/ESA- cells in HCT116-XRCC4 KO cells, but extremely decreased compared to HCT116-WT cells. In conclusion, expression of cancer stem-like cell markers significantly increased after X-ray irradiation in XRCC4 deficient cells, suggesting that XRCC4 may be involved in cancer cell stemness.54th Annual Meeting of ASTR
