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Genomic features of Helicobacter pylori-na��ve diffuse-type gastric cancer.

Helicobacter pylori (HP) is a major etiologic driver of diffuse-type gastric cancer (DGC).However, improvements in hygiene have led to an increase in the prevalence of HP-na��ve DGC;that is, DGC that occurs independent of HP. Although multiple genomic cohort studies forgastric cancer have been conducted, including studies for DGC, distinctive genomic differencesbetween HP-exposed and HP-na��ve DGC remain largely unknown. Here, we employed exomeand RNA sequencing with immunohistochemical analyses to perform binary comparisonsbetween 36 HP-exposed and 27 HP-na��ve DGCs from sporadic, early-stage, and intramucosal orsubmucosal tumor samples. Among the samples, 33 HP-exposed and 17 HP-na��ve samples hadbeen preserved as fresh-frozen samples. HP infection status was determined using stringentcriteria. HP-exposed DGCs exhibited an increased single nucleotide variant burden (HP-exposed DGCs; 1.97 [0.48���7.19] and HP-na��ve DGCs; 1.09 [0.38���3.68] per megabase;p=0.0003) and a higher prevalence of chromosome arm-level aneuploidies (p<0.0001). CDH1was mutated at similar frequencies in both groups, whereas RHOA���ARHGAP pathwaymisregulation was exclusive to HP-exposed DGCs (p=0.0167). HP-exposed DGCs showedgains in chromosome arms 8p/8q (p<0.0001), 7p (p=0.0035) and 7q (p=0.0354), and losses in16q (p=0.0167). Immunohistochemical analyses revealed a higher expression of intestinalmarkers such as CD10 (p<0.0001) and CDX2 (p=0.0002) and a lower expression of the gastricmarker, MUC5AC (p=0.0305) among HP-exposed DGCs. HP-na��ve DGCs, on the other hand,had a purely gastric marker phenotype. This work reveals that HP-na��ve and HP-exposed DGCsdevelop along different molecular pathways, which provide a basis for early detection strategiesin high incidence settings.