Association of cagA-Positive Helicobacter pylori with MGMT Promoter Hypermethylation Across the Gastric Disease Spectrum and Gastric Cancer

<ns7:p> Background Epigenetic alteration through promoter DNA methylation is associated with gastric carcinogenesis. This study assessed the association between <ns7:italic>Helicobacter pylori</ns7:italic> infection, specifically <ns7:italic>cagA</ns7:italic> -positive strains, and <ns7:italic>MGMT</ns7:italic> promoter hypermethylation within the gastroduodenal disease spectrum in an Iraqi cohort. Methods The study conducted a case control study of 120 participants (40 endoscopy confirmed controls without gastroduodenal disease and 80 patients with gastritis, peptic ulcer disease, lymphoma, or gastric adenocarcinoma). Standard OGD biopsies were collected. <ns7:italic>H. pylori</ns7:italic> status was determined by rapid urease testing, selective culture on blood agar with biochemical identification, and PCR confirmation; <ns7:italic>cagA</ns7:italic> was detected by conventional PCR using validated primers and cycling conditions. Genomic DNA was separated and bisulfite treatment converted. <ns7:italic>MGMT</ns7:italic> promoter methylation was measured by methylation specific PCR primers and bisulfate treatment. Statistical analyses used chi-square or chi-square and reported odds ratios with 95% confidence intervals. Results The results showed a significantly greater incidence of <ns7:italic>H. pylori</ns7:italic> than controls (72.5% vs. 0%; χ <ns7:sup>2</ns7:sup> =56.129, p&lt;0.001; OR=210.60, 95% CI 12.42–3572.22). <ns7:italic>CagA</ns7:italic> was found in 56.3% of patients and 0% of controls (χ <ns7:sup>2</ns7:sup> =36.000, p&lt;0.001; OR=103.82, 95% CI 6.17–1747.38). <ns7:italic>MGMT</ns7:italic> promoter hypermethylation was observed in 66.3% of patients, whereas none of the controls exhibited this condition (χ <ns7:sup>2</ns7:sup> =47.463, p&lt;0.001; OR=157.58, 95% CI 9.33–2661.18). Methylation varied across disease categories (χ <ns7:sup>2</ns7:sup> (15)=66.433, p&lt;0.001), exhibiting heightened hypermethylation in gastritis (acute/chronic), peptic ulcer disease, gastric lymphoma, and gastric adenocarcinoma, whereas controls remained uniformly unmethylated. In the complete cohort <ns7:italic>, H. pylori</ns7:italic> positivity exhibited a significant correlation with hypermethylation (43/58 vs 10/62; χ <ns7:sup>2</ns7:sup> =40.892, p&lt;0.001; OR=14.91, 95% CI 6.09–36.60), while <ns7:italic>cagA</ns7:italic> positivity demonstrated an even more pronounced association (41/45 vs 12/75; χ <ns7:sup>2</ns7:sup> =64.345, p&lt;0.001; OR=53.81, 95% CI 16.24–178.31). There was a link between smoking and hypermethylation (χ <ns7:sup>2</ns7:sup> (2)=15.218, p&lt;0.001), but sex, residence, chronic disease, and therapy were not significant (all p&gt;0.10). Conclusions <ns7:italic>MGMT</ns7:italic> promoter hypermethylation is prevalent in gastroduodenal diseases in Iraqi cases, with <ns7:italic>H. pylori</ns7:italic> infection strongly correlated with <ns7:italic>MGMT</ns7:italic> hypermethylation, suggesting <ns7:italic>MGMT</ns7:italic> methylation as a biomarker for risk stratification. </ns7:p>