Fig. 4

MGMT inhibition enhanced CDDP-induced DSB in NPC cells. After treatment with O6BG (60 μM), CDDP alone or a combination of both for 24 h, the DSB formation of a HONE-1 and b TW01 cells were analyzed using the neutral comet assay. After electrophoresis, the cell slides were stained with PI for visualization. The percentages of DNA in the tail were quantified by measuring the proportion of tail length in at least 100 comet cells and are presented as bar histograms. Bar values are presented as mean ± SD of at least three independent experiments. *P < 0.05. The expression of γ-H2AX was examined using Western blot analyses in c HONE-1and d TW01 cells following treatment with O6BG (60 μM), CDDP (10 µM), or a combination of both for 24 h. The expression of γ-H2AX induced by CDDP treatment was also examined in MGMT-proficient or -deficient NPC cells. After e HONE-1 and f TW01 cells were transfected with scrambled or MGMT-targeted siRNA for 24 h, these cells were treated with CDDP for another 24 h. Representative images of at least three independent experiments are shown