[en] The foci of phosphorylated histone H2AX (γH2AX) and phosphorylated ataxia telangiectasia mutated (pATM) were visualized using immunocytochemical methods. Flow cytometry was used to assay γH2AX and pATM expression and the cell cycle. The results of immunocytochemical assay showed that the strongest induction of γH2AX and pATM foci appeared at 0.5 h and 4 h after irradiation, and the positivity for γH2AX and pATM foci reached 100% at 24 h with X-ray exposure in higher-dose groups. Flow cytometry results showed that the expression of γH2AX and pATM was related to the cell cycle. The rise of γH2AX and pATM expression was shown in each phase at 0.5 h and 4 h post-exposure, and this increase was more obvious in G0/G1 phase. At 24 h post-exposure, the expression of γH2AX and pATM decreased in G0/G1 and S phase, while increased significantly in G2/M phase. There was significant prevalence of the arrest at the G2-M transition among M059K cells. The above results indicate that the signaling pathways of γH2AX and pATM is involved in X-ray-induced double-strand breaks in M059K cells. (authors)