Figure 5

DNA damage response is responsible for FCdR-induced cell cycle arrest. A. Cells were treated with indicated amount of chemicals for 12 h and damaged DNA was detected by alkaline comet assay. B. Olive tail moment in the previous assay was calculated according to manufacturer’s method and the statistic results were shown. C. HCT116 p53^+/+ and p53^−/− cells were treated with FCdR. Markers for DNA damage response (pH2AX, pATM and pCHK1) and cell cycle (Cyclin B1, Cyclin D1 and Cyclin E1) were analyzed by western blot. Histone H3 and β-ACTIN were used as loading controls. D. HCT116 p53^+/+ and p53^−/− cells were treated with FCdR for 8 h and immunofluorescence staining was performed to show FCdR induced H2AX phosphorylation in both cell lines. E. Three drugs were used to treat HCT116 for 8 h and DNA damage responses were investigated by western blotting. FCdR and 5-azaC were able to induce phosphorylation of H2AX, ATM and CHK1, but not SAHA. H3 was used as control. F. The inhibitory effect of LY294002 to FCdR induced DNA damage response was assayed. G. Addition of 50 μM LY294002 restored the G2/M arrest induced by 0.1 μM FCdR. (* p value < 0.05).