title: Autophagy impairment by Helicobacter pylori-induced methylation silencing of MAP1LC3Av1 promotes gastric carcinogenesis.
abstract: Helicobacter pylori (H. pylori) infection induces methylation silencing of tumor suppressor genes causing gastric carcinogenesis. Impairment of autophagy induces DNA damage leading to genetic instability and carcinogenesis. We aimed to identify whether H. pylori infection induced methylation silencing of host autophagy-related (Atg) genes, impairing autophagy and enhancing gastric carcinogenesis. Gastric mucosae were obtained from 41 gastric cancer patients and 11 healthy volunteers (8 H. pylori-uninfected and 3 H. pylori-infected). Methylation status of Atg genes was analyzed by a methylation microarray and quantitative methylation-specific PCR (qMSP); mRNA expression was assessed by quantitative reverse transcription PCR (qRT-PCR). Cell proliferation, migration and invasion were assessed in normal rat gastric epithelial cells. Gene knock-down was performed by siRNA. Autophagy was assessed by western blotting. Of 34 Atg genes, MAP1LC3A variant 1 (MAP1LC3Av1) and ULK2 were identified by methylation microarray analysis as exhibiting specific methylation in H. pylori-infected mucosae and gastric cancer tissues. Methylation silencing of MAP1LC3Av1 was confirmed by qMSP, qRT-PCR and de-methylation treatment in two gastric cancer cell lines. Knock-down of map1lc3a, the rat homolog of the human MAP1LC3Av1, inhibited autophagy response and increased cell proliferation, migration and invasion in normal rat gastric epithelial cells, despite the presence of map1lc3b, the rat homolog of the human MAP1LC3B gene important for autophagy. Furthermore, MAP1LC3Av1 was methylation-silenced in 23.3% of gastric cancerous mucosae and 40% of non-cancerous mucosae with H. pylori infection. MAP1LC3Av1 is essential for autophagy and H. pylori-induced methylation silencing of MAP1LC3Av1 may impair autophagy, facilitating gastric carcinogenesis.
authors.affiliation: Department of Gastroenterology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan.|Department of Biological and Biomedical Sciences, Faculty of Health Sciences, The Aga Khan University, Karachi, Pakistan.
authors.forename: Jibran Sualeh
authors.initials: JS
authors.lastname: Muhammad
authors.affiliation: Department of Gastroenterology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan.
authors.forename: Sohachi
authors.identifier: http://orcid.org/0000-0002-5826-2893
authors.initials: S
authors.lastname: Nanjo
authors.affiliation: Department of Gastroenterology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Ando
authors.affiliation: Division of Epigenomics, National Cancer Center Research Institute, Tokyo, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Yamashita
authors.affiliation: Second Department of Internal Medicine, School of Medicine, Wakayama Medical University, Wakayama, Japan.
authors.forename: Takao
authors.initials: T
authors.lastname: Maekita
authors.affiliation: Division of Epigenomics, National Cancer Center Research Institute, Tokyo, Japan.
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Ushijima
authors.affiliation: Division of Molecular Genetic Research, Life Science Research Center, University of Toyama, Toyama, Japan.
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Tabuchi
authors.affiliation: Department of Gastroenterology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan.
authors.forename: Toshiro
authors.identifier: http://orcid.org/0000-0001-8757-432X
authors.initials: T
authors.lastname: Sugiyama
mesh_terms: D000818:Animals; D001343:Autophagy; D014408:Biomarkers, Tumor; D063646:Carcinogenesis; D002465:Cell Movement; D049109:Cell Proliferation; D002478:Cells, Cultured; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D005753:Gastric Mucosa / Q000378:metabolism / Q000473:pathology* / Q000821:virology; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D016481:Helicobacter Infections / Q000235:genetics / Q000473:pathology* / Q000821:virology; D016480:Helicobacter pylori; D006801:Humans; D007124:Immunoenzyme Techniques; D008869:Microtubule-Associated Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D009367:Neoplasm Staging; D011379:Prognosis; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013274:Stomach Neoplasms / Q000235:genetics / Q000473:pathology* / Q000821:virology
chemical_list: D014408:Biomarkers, Tumor; C477012:MAP1LC3A protein, human; D008869:Microtubule-Associated Proteins; D012333:RNA, Messenger
keywords: Helicobacter pylori; MAP1LC3Av1; autophagy; gastric cancer; methylation silencing