Original Article
Copyright ©2014 Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Sep 7, 2014; 20(33): 11770-11779
Published online Sep 7, 2014. doi: 10.3748/wjg.v20.i33.11770
Connexin 32 and 43 promoter methylation in Helicobacter pylori-associated gastric tumorigenesis
Yu Wang, Li-Hua Huang, Can-Xia Xu, Jing Xiao, Li Zhou, Dan Cao, Xiao-Min Liu, Yong Qi
Yu Wang, Can-Xia Xu, Jing Xiao, Li Zhou, Dan Cao, Xiao-Min Liu, Department of Gastroenterology, Third Xiangya Hospital, Central South University, Changsha 410013, Hunan Province, China
Yu Wang, Department of Internal Medicine, The Third People’s Hospital of Huaihua, Huaihua 418000, Hunan Province, China
Li-Hua Huang, Center for Medical Experiments, Third Xiangya Hospital, Central South University, Changsha 410013, Hunan Province, China
Yong Qi, Clinical Laboratory, Third Xiangya Hospital, Central South University, Changsha 410013, Hunan Province, China
Author contributions: Wang Y and Huang LH contributed equally to this work and should be considered as co-first authors; Wang Y detected the expression and methylation of Connexin 32 and 43 and wrote the manuscript; Huang LH guided the detection of Connexin 32 and 43 expression and methylation, and translated and revised the manuscript; Xu CX designed the study, performed the endoscopic procedures, collected specimens and guided the writing and revising of the manuscript; Xiao J, Zhou L, Cao D, and Liu XM collected the specimens; Qi Y performed the H. pylori culture.
Supported by The National Natural Science Foundation of China, No. 81172301; and Changsha Municipal Science and Technology Project, No. K1106036-31
Correspondence to: Can-Xia Xu, MD, Professor, Department of Gastroenterology, Third Xiangya Hospital of Central South University, 138 Tongzipo Street, Changsha 410013, Hunan Province, China. xucanxia2000@163.com
Telephone: +86-731-88618631 Fax: +86-731-88618012
Received: November 28, 2013
Revised: March 11, 2014
Accepted: March 19, 2014
Published online: September 7, 2014
Abstract

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), and gastric 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.

Keywords: Gastric cancer, Helicobacter pylori, Cx32, Cx43, DNA methylation

Core tip: The relationship between Connexin (Cx) 32 and Cx43 mRNA expression and gene promoter methylation at different gastric carcinogenesis stages with H. pylori infection, that is, non-atrophic gastritis, atrophic gastritis, intestinal metaplasia, dysplasia, and gastric cancer, is not clear. Here, gastric mucosa biopsy specimens from these carcinogenic stages, as well as normal gastric mucosa without H. pylori infection, were examined for Cx32 and Cx43 mRNA expression and promoter methylation by real-time polymerase chain reaction and methylation detection. Cx32 and Cx43 mRNA expression decreased gradually during gastric carcinogenesis, and it is associated with hypermethylation of these genes’ promoter.