H4K20me3 is increased in human bladder cancer tissues, and it is upregulated by reactive oxygen species in bladder cancer cell lines.

Background: Previously, we demonstrated that reactive oxygen species (ROS) provoked oxidative stress, enhanced tumor aggressiveness, and induced a profound change in histone methylation in bladder cancer (BlCa). We also reported an upregulation of H4K20me3 by ROS in hepatocellular carcinoma. In this study, we investigated whether H4K20me3 was upregulated in human BlCa tissues (n = 37) and asked if ROS could induce H4K20me3 formation in BlCa cell lines. Methods: Immunohistochemical (IHC) staining was performed in 37 BlCa sections and 6 adjacent noncancerous tissues (as controls). H4K20me3 upregulated by ROS was investigated in three BlCa cell lines (UM-UC-3, VM- CUB-1 and TCCSUP). Results: H4K20me3 level in BlCa tissues was increased relative to the adjacent noncancerous tissues. The IHC score of H4K20me3 level in BlCa tissues was significantly higher than in noncancerous controls. H 2 O 2 (ROS representative) at 50, 100 and 200 M significantly provoked oxidative stress in UM-UC-3, VM-CUB-1 and TCCSUP cells, respectively, but not significantly alter cell survival. The results from both western blot and immunofluorescent staining showed that treatment with H 2 O 2 markedly increased H4K20me3 formation in all three cell lines. Conclusion: We demonstrated H4K20me3 level in BlCa tissues obtained from Thai BlCa patients was increased compared with the adjacent noncancerous tissues. Evidently, ROS upregulated H4K20me3 formation in BlCa cell lines. Whether ROS-induced BlCa progression is mediated through H4K20me3 formation remains to be elucidated.