Connexin 32 and 43 promoter methylation in Helicobacter pylori-associated gastric tumorigenesis

• Published in: World journal of gastroenterology : WJG 2014-09, Vol.20 (33), p.11770-11779
• Main Authors: Wang, Yu, Huang, Li-Hua, Xu, Can-Xia, Xiao, Jing, Zhou, Li, Cao, Dan, Liu, Xiao-Min, Qi, Yong
• Format: Article
• Language: English
• Subjects: Biomarkers, Tumor - genetics; Biopsy; cancer; Cell Transformation, Neoplastic - genetics; Cell Transformation, Neoplastic - pathology; Connexin 43 - genetics; Connexins - genetics; CpG Islands; Cx32; Cx43; Disease Progression; DNA; DNA Methylation; Down-Regulation; Gap Junction beta-1 Protein; Gastric; Gastric Mucosa - microbiology; Gastric Mucosa - pathology; Gene Expression Regulation, Neoplastic; Helicobacter; Helicobacter Infections - complications; Helicobacter Infections - microbiology; Helicobacter pylori - pathogenicity; Humans; Neoplasm Staging; Original; Polymerase Chain Reaction; Promoter Regions, Genetic; pylori; RNA, Messenger - analysis; Stomach Neoplasms - genetics; Stomach Neoplasms - microbiology; Stomach Neoplasms - pathology
• ISSN: 1007-9327; 2219-2840
• DOI: 10.3748/wjg.v20.i33.11770

AIM: To explore the mechanism of abnormal Connexin(Cx) 32 and Cx43 expression in the gastric mucosa after Helicobacter pylori(H. pylori) infection.METHODS: Biopsy specimens of gastric mucosa in different gastric carcinogenesis stages with H. pylori infection, that is, non-atrophic gastritis(NAG; n = 24), chronic atrophic gastritis(CAG; n = 25), intestinal metaplasia(IM; n = 28), dysplasia(DYS; n = 24), andgastric cancer(GC; n = 30), as well as specimens of normal gastric mucosa without H. pylori infection(NGM; n = 25), were confirmed by endoscopy and pathological examination. Cx32 and Cx43 mRNA expression was detected by real-time polymerase chain reaction(PCR). Cx32 and Cx43 promoter CpG island methylation status was determined by methylation-specific PCR(MSP), bisulfite PCR sequencing(BSP) and MassArray methods. RESULTS: The relative mRNA expression levels in the gastric mucosa of patients with NGM, NAG, CAG, IM, DYS and GC were 0.146 ± 0.011, 0.133 ± 0.026, 0.107 ± 0.035, 0.039 ± 0.032, 0.037 ± 0.01 and 0.03 ± 0.011 for Cx32; and 0.667 ± 0.057, 0.644 ± 0.051, 0.624 ± 0.049, 0.555 ± 0.067, 0.536 ± 0.058 and 0.245 ± 0.121 for Cx43, respectively, which were gradually decreasing and significantly different(GC vs NGM: P < 0.001 for Cx32, P < 0.001 for Cx43). The promoter methylation levels in the gastric mucosa from NGM to GC stages by MSP were 38.8% ± 9.0%, 43.1% ± 9.4%, 56.5% ± 3.1%, 64.4% ± 9.7%, 72.5% ± 4.2% and 79.6% ± 6.8% for Cx32; and 49.0% ± 3.9%, 58.1% ± 5.0%, 66.5% ± 7.9%, 74.0% ± 8.8%, 78.3% ± 3.6% and 88.7% ± 6.2% for Cx43, respectively, which were gradually increasing and significantly different(P = 0.039, P = 0.019). The promoter methylation levels by BSP and MassArray exhibited similar trends. Cx32 and Cx43 mRNA expression was negatively correlated with promoter methylation status and gastric carcinogenesis stages(P < 0.001, P = 0.016).CONCLUSION: Cx32 and Cx43 mRNA expression decreased gradually during H. pylori infection-associated gastric carcinogenesis, and it is associated with hypermethylation of these genes’ promoter.