Silencing of Glutathione Peroxidase 3 through DNA Hypermethylation Is Associated with Lymph Node Metastasis in Gastric Carcinomas

Abstract

Gastric cancer remains the second leading cause of cancer-related death in the world. H. pylori infection, a major risk factor for gastric cancer, generates high levels of reactive oxygen species (ROS). Glutathione peroxidase 3 (GPX3), a plasma GPX member and a major scavenger of ROS, catalyzes the reduction of hydrogen peroxide and lipid peroxides by reduced glutathione. To study the expression and gene regulation of GPX3, we examined GPX3 gene expression in 9 gastric cancer cell lines, 108 primary gastric cancer samples and 45 normal gastric mucosa adjacent to cancers using quantitative real-time RT-PCR. Downregulation or silencing of GPX3 was detected in 8 of 9 cancer cell lines, 83% (90/108) gastric cancers samples, as compared to non-tumor adjacent normal gastric samples (P<0.0001). Examination of GPX3 promoter demonstrated DNA hypermethylation (≥10% methylation level determined by Bisulfite Pyrosequencing) in 6 of 9 cancer cell lines and 60% of gastric cancer samples (P = 0.007). We also detected a significant loss of DNA copy number of GPX3 in gastric cancers (P<0.001). Treatment of SNU1 and MKN28 cells with 5-Aza-2′ Deoxycytidine restored the GPX3 gene expression with a significant demethylation of GPX3 promoter. The downregulation of GPX3 expression and GPX3 promoter hypermethylation were significantly associated with gastric cancer lymph node metastasis (P = 0.018 and P = 0.029, respectively). We also observed downregulation, DNA copy number losses, and promoter hypermethylation of GPX3 in approximately one-third of tumor-adjacent normal gastric tissue samples, suggesting the presence of a field defect in areas near tumor samples. Reconstitution of GPX3 in AGS cells reduced the capacity of cell migration, as measured by scratch wound healing assay. Taken together, the dysfunction of GPX3 in gastric cancer is mediated by genetic and epigenetic alterations, suggesting impairment of mechanisms that regulate ROS and its possible involvement in gastric tumorigenesis and metastasis.

Troglitazone inhibits the migration and invasion of PC‑3 human prostate cancer cells by upregulating E‑cadherin and glutathione peroxidase 3

“…Our previous study revealed that GPx3 is downregulated in prostates of TRAMP mice and that disruption of GPx3 expression in TRAMP mice increased prostate cancer development and metastasis (50). It has been demonstrated that silencing GPx3 expression promoted cancer metastasis in human thyroid and gastric cancer cells (37,38). In the present study, it was notable that GPx3 expression level was upregulated following treatment with TGZ in human prostate cancer cells.…”

“…It is well known that glutathione peroxidases are among the most important reactive oxygen species scavengers that protect cells from oxidative damage (36). Downregulation of GPx3 by hypermethylation has been revealed in numerous types of cancer (37)(38)(39)(40)(41)(42)(43)(44)(45), including prostate cancer (11,46,47). In prostate cancer, a negative correlation between GPx3 expression levels and poor clinical outcomes has been demonstrated (47,48).…”

DNA Methylation Profiling in Pheochromocytoma and Paraganglioma Reveals Diagnostic and Prognostic Markers

“…This suggests that expression of these three genes may also represent potential markers for metastatic PPGLs. GPX3 silencing has been reported in metastatic tumors, such as in gastric carcinomas, where it increased migration and impaired mechanisms regulating reactive oxygen species (47). RERG was reported as a prognostic marker in breast cancer, whose expression correlated inversely proliferation, patient survival, and development of distant metastases (48).…”

Association of Antioxidative Enzymes Polymorphisms with Efficacy of Platin and Fluorouracil-Based Adjuvant Therapy in Gastric Cancer

“…GPx3 was found frequently down-regulated in cancer tissues including breast, lung and gastric cancer [47], which may due to its promoter hypermethylation [48][49][50]. Silencing or decreased activity of GPX3 is correlated with increased ROS level and contributes to cancer initiation [51] and metastasis [52,53].…”