Oxidative Stress Induces Hypomethylation of LINE-1 and Hypermethylation of the RUNX3 Promoter in a Bladder Cancer Cell Line

Abstract

Increased oxidative stress and changes in DNA methylation are frequently detected in bladder cancer patients. We previously demonstrated a relationship between increased oxidative stress and hypomethylation of the transposable long-interspersed nuclear element-1 (LINE-1). Promoter hypermethylation of a tumor suppressor gene, runt-related transcription factor 3 (RUNX3), may also be associated with bladder cancer genesis. In this study, we investigated changes of DNA methylation in LINE-1 and RUNX3 promoter in a bladder cancer cell (UM-UC-3) under oxidative stress conditions, stimulated by challenge with H 2 O 2 for 72 h. Cells were pretreated with an antioxidant, tocopheryl acetate for 1 h to attenuate oxidative stress. Methylation levels of LINE-1 and RUNX3 promoter were measured by combined bisulfite restriction analysis PCR and methylation-specific PCR, respectively. Levels of LINE-1 methylation were significantly decreased in H 2 O 2 -treated cells, and reestablished after pretreated with tocopheryl acetate. Methylation of RUNX3 promoter was significantly increased in cells exposed to H 2 O 2 . In tocopheryl acetate pretreated cells, it was markedly decreased. In conclusion, hypomethylation of LINE-1 and hypermethylation of RUNX3 promoter in bladder cancer cell line was experimentally induced by reactive oxygen species (ROS). The present findings support the hypothesis that oxidative stress promotes urothelial cell carcinogenesis through modulation of DNA methylation. Our data also imply that mechanistic pathways of ROS-induced alteration of DNA methylation in a repetitive DNA element and a gene promoter might differ.

LINE-1 in cancer: multifaceted functions and potential clinical implications

“…31,84 Oxidative stress can promote L1 hypomethylation and L1 expression in cancer cell lines, along with disrupted expression of genes involved in DNA repair. 81,82 Additionally, some precancerous conditions, such as chronic inflammation, can stimulate oxidative stress. 85,86 Therefore, oxidative stress-induced L1 activation might represent one of the mechanisms linking chronic inflammation and tumorigenesis, which deserves further investigation.…”

Mechanisms of Superoxide Signaling in Epigenetic Processes: Relation to Aging and Cancer

“…Mitochondrial superoxide generation was an important factor of Kras-mediated tumorigenicity [97]. ROS induced hypomethylation of LINE-1 and hypermethylation of the RUNX3 promoter in a bladder cancer cell line [98]. Superoxide silenced the candidate tumor suppressor gene through ROS-induced methylation and may therefore be associated with the progression of colorectal cancer [99].…”

Retrospective Study of Adjuvant Chemotherapy Effects on Survival Rate after Three-Field Lymph Node Dissection for Stage IIA Esophageal Cancer

“…Given the potential role of RUNX3 in TGF-b signaling, it is possible that the tumor suppressor activity of RUNX3 is realized by regulating cell migration and invasion . More and more studies during recent years discovered that RUNX3 inactivation is a crucial factor to determine cancer pathogenesis and clinical outcome in a variety of cancer types, such as gastric, colonic, prostate, breast, lung and bladder cancers (Araki et al, 2005;Suzuki et al, 2005;Ogino et al, 2007;Jiang et al, 2008;Hsu et al, 2009;Wongpaiboonwattana W et al, 2013). It was also reported in esophageal cancer (Sugiura et al, 2008).…”