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Researchers may have discovered a key determinant of a rare complication of gastric lymphoma—a virulence sequence of Helicobacter pylori—in a comparative molecular study.
They looked for genetic markers in H pylori strains isolated from patients with gastric extranodal marginal zone B cell lymphoma (MZBL) of the mucosa-associated lymphoid tissue (MALT)-type and strains from age matched patients with gastritis only. They used subtractive hybridisation, which allows genes or sequences from isolated strains to be compared with a chosen control strain. The two strains used were a “tester” gastric MZBL strain and a “driver” gastritis strain chosen as the control, which had six known H pylori virulence genes in common.
Two open reading frames (ORFs) from the hybridisation were significantly linked with gastric MZBL over gastritis strains: JHP950 (74% v 49%) and JHP1462 (26% v 3%). JHP950 proved specific for gastric MZBL when tested against a group of strains from patients with duodenal ulcer and patients with adenocarcinoma, with significant prevalences (49% and 39%, respectively), and is therefore the candidate marker for gastric MZBL. Both ORFs coded for unknown products.
The researchers tested 43 strains from patients with gastric MZBL, 39 from patients with gastritis only, 41 from duodenal ulcer, and 28 from gastric adenocarcinoma. All patients were age matched.
H pylori causes gastric adenoma and MALT lymphoma and also 80% of gastric MZBL. Bacterial virulence factors may be responsible, but the researchers had previously ruled out all six H pylori virulence factors and instead investigated genetic variation specific to MZBL strains.