title: Reduced expression of MUTYH with suppressive activity against mutations caused by 8-hydroxyguanine is a novel predictor of a poor prognosis in human gastric cancer.
abstract: The MUTYH gene encodes a DNA glycosylase that can initiate the excision repair of adenine mispaired with 8-hydroxyguanine (8OHG) and is responsible for a susceptibility to multiple colorectal adenomas and carcinomas. To determine whether the MUTYH gene is involved in gastric carcinogenesis, we first examined the expression level of MUTYH in gastric cancer. The reduced expression of MUTYH mRNA transcript was detected in both gastric cancer cell lines and primary gastric cancers using qRT-PCR analysis. Immunohistochemical analysis also showed a significant reduction in MUTYH protein expression in gastric cancer, compared with non-cancerous gastric epithelium (immunohistochemical score, 175.5 ± 43.0 versus 281.5 ± 24.8; p < 0.0001). Among the gastric cancers, the MUTYH expression level was significantly associated with the histopathology (p < 0.0001) and the pT stage (p < 0.001). The outcome of patients with gastric cancer exhibiting low MUTYH expression was significantly worse than the outcome of patients with gastric cancer exhibiting high MUTYH expression (p = 0.0007, log-rank test) and a multivariate analysis revealed that reduced MUTYH expression was an independent predictor of a poor survival outcome among the gastric cancer patients (hazard ratio, 1.865; 95% confidence interval, 1.028-3.529; p = 0.0401). We next compared the functional effects of MUTYH on gastric cancer cells, based on their MUTYH expression levels. MUTYH-over-expressing stable clones of the gastric cancer cell line AGS showed: (a) higher DNA cleavage activity towards adenine:8OHG mispair-containing substrates; (b) higher suppressive activity against mutations caused by 8OHG in a supF forward mutation assay; and (c) higher suppressive activity for cellular proliferation than empty vector-transfected AGS clones. These results suggested that MUTYH is a suppressor of mutations caused by 8OHG in gastric cells and that its reduced expression is associated with a poor prognosis in gastric cancer.
authors.affiliation: 1st Department of Pathology, Hamamatsu University School of Medicine, Hamamatsu, Japan. kzshinmu@hama-med.ac.jp
authors.forename: Kazuya
authors.initials: K
authors.lastname: Shinmura
authors.forename: Masanori
authors.initials: M
authors.lastname: Goto
authors.forename: Masaya
authors.initials: M
authors.lastname: Suzuki
authors.forename: Hong
authors.initials: H
authors.lastname: Tao
authors.forename: Hidetaka
authors.initials: H
authors.lastname: Yamada
authors.forename: Hisaki
authors.initials: H
authors.lastname: Igarashi
authors.forename: Shun
authors.initials: S
authors.lastname: Matsuura
authors.forename: Matsuyoshi
authors.initials: M
authors.lastname: Maeda
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Konno
authors.forename: Tomonari
authors.initials: T
authors.lastname: Matsuda
authors.forename: Haruhiko
authors.initials: H
authors.lastname: Sugimura
mesh_terms: D000368:Aged; D014408:Biomarkers, Tumor / Q000096:biosynthesis* / Q000235:genetics; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism; D045647:DNA Glycosylases / Q000096:biosynthesis* / Q000235:genetics; D015536:Down-Regulation; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006147:Guanine / Q000031:analogs & derivatives; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation; D009363:Neoplasm Proteins / Q000096:biosynthesis / Q000235:genetics; D009367:Neoplasm Staging; D011379:Prognosis; D012333:RNA, Messenger / Q000235:genetics; D012334:RNA, Neoplasm / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D013274:Stomach Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D014407:Tumor Cells, Cultured
chemical_list: D014408:Biomarkers, Tumor; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D012334:RNA, Neoplasm; C024829:8-hydroxyguanine; D006147:Guanine; D045647:DNA Glycosylases; C061738:mutY adenine glycosylase