Published online Sep 7, 2014. doi: 10.3748/wjg.v20.i33.11770
Revised: March 11, 2014
Accepted: March 19, 2014
Published online: September 7, 2014
Processing time: 282 Days and 20.7 Hours
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.
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.