Fig. 4

HDS impaired DNA damage repair by inhibiting dNTP synthesis. A Gene expression profiling was performed after H929 cells were treated with 50 µM HDS for 48 h. Heat map showed significant pathways affected by HDS. B DNA synthesis in MM cells treated with HDS for 24 h was evaluated by EdU incorporation. EdU incorporation was observed using laser scanning confocal microscopy. The number of EdU-positive cells was quantified. C MM cells were incubated with HDS either without or with exogenous 50 µM dNTPs for 24 h. Percentage of EdU positive cells in flow cytometry was showed in the right panel. D NHEJ and HR in cells treated with HDS (0, 50 and 100 µM) for 24 h were quantified by the GFP and DsRed expression using flow cytometry. E MM cells were treated with 100 µM HDS for 24 h, and then the comet assay was performed. F Expression of cellular γ-H2AX in H929 and ARP-1 cells treated with or without 100 µM HDS for 24 h was detected by immunofluorescence. G Western blot analysis of DNA damage-related proteins in cell lysates of H929 and ARP-1 cells treated with indicated concentration of HDS for 24 h. H Immunofluorescence staining of cellular γ-H2AX in H929 and ARP-1cells treated with 100 µM HDS, either without or with 50 µM exogenous dNTPs for 24 h. I Western blot analysis of DNA damage-related proteins in MM cells incubated with HDS either without or with exogenous 50 µM dNTPs for 24 h. All data are expressed as means ± SD of three independent experiments. *P < 0.05, **P < 0.01, ***P < 0.001