Related Experiment Video
Updated: May 11, 2026
Gastric Mucosa Quantitative Polymerase Chain Reaction Analysis for Detecting Helicobacter pylori and Antibiotic Resistance
Published on: March 7, 2025
MGMT and MLH1 methylation in Helicobacter pylori-infected children and adults
Marisa C Alvarez1, Juliana C Santos, Nathália Maniezzo
1Unidade Integrada de Farmacologia e Gastroenterologia, Universidade São Francisco, Bragança Paulista 12916-900, SP, Brazil.
Aim:
To evaluate the association between Helicobacter pylori (H. pylori) infection and MLH1 and MGMT methylation and its relationship with microsatellite instability (MSI).
Methods:
The methylation status of the MLH1 and MGMT promoter region was analysed by methylation specific methylation-polymerase chain reaction (MSP-PCR) in gastric biopsy samples from uninfected or H. pylori-infected children (n = 50), from adults with chronic gastritis (n = 97) and from adults with gastric cancer (n = 92). MLH1 and MGMT mRNA expression were measured by real-time PCR and normalised to a constitutive gene (β actin). MSI analysis was performed by screening MSI markers at 4 loci (Bat-25, Bat-26, D17S250 and D2S123) with PCR; PCR products were analysed by single strand conformation polymorphism followed by silver staining. Statistical analyses were performed with either the χ(2) test with Yates continuity correction or Fisher's exact test, and statistical significance for expression analysis was assessed using an unpaired Student's t-test.
Results:
Methylation was not detected in the promoter regions of MLH1 and MGMT in gastric biopsy samples from children, regardless of H. pylori infection status. The MGMT promoter was methylated in 51% of chronic gastritis adult patients and was associated with H. pylori infection (P < 0.05); this region was methylated in 66% of gastric cancer patients, and the difference in the percentage of methylated samples between these patients and those from H. pylori-infected chronic gastritis patients was statistically significant (P < 0.05). MLH1 methylation frequencies among H. pylori-infected and non-infected chronic gastritis adult patients were 13% and 7%, respectively. We observed methylation of the MLH1 promoter (39%) and increased MSI levels (68%) in samples from gastric cancer patients in comparison to samples from H. pylori-infected adult chronic gastritis patients (P < 0.001 and P < 0.01, respectively). The frequency of promoter methylation for both genes was higher in gastric cancer samples than in H. pylori-positive chronic gastritis samples (P < 0.05). The levels of MLH1 and MGMT mRNA were significantly reduced in chronic gastritis samples that were also hypermethylated (P < 0.01).
Conclusion:
In summary, MGMT and MLH1 methylation did not occur in earlier-stage H. pylori infections and thus might depend on the duration of infection.
Insights
Helicobacter pylori (H. pylori) infection is linked to MGMT and MLH1 gene methylation in adults, particularly in gastric cancer. This methylation, associated with microsatellite instability, appears to develop over time, not in early infections.
Area of Science:
- Gastroenterology
- Oncology
- Molecular Biology
Background:
- Helicobacter pylori (H. pylori) infection is a known risk factor for gastric diseases.
- Gene promoter methylation, specifically of MLH1 and MGMT, plays a role in cancer development.
- Microsatellite instability (MSI) is a hallmark of certain cancers.
Purpose of the Study:
- To investigate the association between H. pylori infection and MLH1/MGMT promoter methylation.
- To explore the relationship between these methylation events and MSI in gastric tissues.
- To assess methylation patterns across different stages of gastric disease.
Main Methods:
- Analysis of MLH1 and MGMT promoter methylation using methylation-specific PCR (MSP-PCR).
- Quantification of MLH1 and MGMT mRNA expression via real-time PCR.
- MSI analysis using established markers and PCR.
- Statistical analysis including chi-squared tests and Student's t-tests.
Main Results:
- No MLH1 or MGMT methylation was observed in children, irrespective of H. pylori status.
- MGMT promoter methylation was prevalent in adult chronic gastritis (51%) and gastric cancer (66%), associated with H. pylori infection.
- MLH1 methylation was detected in adult gastric cancer (39%) and linked to increased MSI.
- Both genes showed higher methylation frequencies in gastric cancer compared to H. pylori-positive chronic gastritis.
Conclusions:
- MGMT and MLH1 methylation are not present in early H. pylori infections.
- The development of MLH1 and MGMT methylation may be dependent on the duration of H. pylori infection.
- These findings highlight the role of epigenetic alterations in H. pylori-associated gastric carcinogenesis.
Related Concept Videos
01:26Gastritis II: Pathophysiology
01:27Peptic Ulcer
01:16Treating Helicobacter pylori in Peptic Ulcers: Antimicrobial Therapy
01:24Peptic Ulcer Disease II: Pathophysiology
01:28Peptic Ulcer Disease III: Clinical Manifestations and Diagnostic Studies
Few clinical manifestations differentiate gastric ulcers from duodenal ulcers. Distinctions in the location, timing, and pain relief are crucial for healthcare providers in differentiating between gastric and duodenal ulcers during clinical assessments.
01:24Pathophysiology of Peptic Ulcer Disease: Mucosal Defense Factors