miR‐155‐regulated mTOR and Toll‐like receptor 5 in gastric diffuse large B‐cell lymphoma

BACKGROUND: Gastric diffuse large B‐cell lymphoma (DLBCL) is often associated with Helicobacter pylori (H. pylori) infection. Those in the early stage could be treated with H. pylori eradication therapy, and are classified into a sensitive group and a resistant group. METHODS: Genome‐wide miRNA and miRNA expression profiles were obtained from biopsy specimens of gastric DLBCL. MiRNAs and their targets as predictors of responses to H. pylori eradication therapy were identified through differential expression and pathway enrichment analysis, and further confirmed with transfection experiments in lymphoma cell lines of B‐cell origin. RESULTS: Genome‐wide miRNA and mRNA profiles showed miR‐200 was associated with the sensitive group, and that the resistant group had higher levels of miR‐155 and lower levels of DEPTOR (an inhibitor of mTOR) than the sensitive group. BJAB cells transfected with miR‐155 also had lower DEPTOR and higher mTOR levels. Therefore, miR‐155‐mediated inhibition of DEPTOR with secondary activation of mTOR was a potential marker for resistance to H. pylori eradication therapy. In contrast, pathway enrichment analysis showed that Toll‐like receptor 5 (TLR5), the receptor for bacterial flagellin, was a potential marker for sensitivity to H. pylori eradication therapy. In an independent series, stronger expression of pS6K1 (a direct target of mTOR) was associated with the resistant group and morphologic evidence of active gastritis was associated with the sensitive group. CONCLUSIONS: These findings showed that activation of the miR‐155‐DEPTOR pathway is a marker for resistance to H. pylori eradication therapy, and that histological evaluation of active gastritis might be used as a surrogate marker to predict responses to H. pylori eradication therapy in gastric DLBCL.