Global knowledge structure and thematic evolution in inflammation-associated gastric cancer epigenetics: a multidatabase science-mapping study with nested latent Dirichlet allocation and independent NMF validation.

Background: Inflammation-associated epigenetic regulation links microbial exposure and chronic mucosal injury to gastric carcinogenesis, immune remodeling, molecular heterogeneity, and treatment resistance. Previous science-mapping studies have commonly relied on a single bibliographic database, which may introduce platform-specific coverage bias. Methods: Web of Science Core Collection (WoSCC), PubMed, and Scopus were searched for English-language articles and reviews published from 2000 through July 2026 using harmonized concepts for gastric malignancy, inflammation, and epigenetic regulation. Database-specific screening yielded 1, 407 WoSCC, 1, 073 PubMed, and 1, 935 Scopus records. Records were harmonized and deduplicated by DOI, PMID, normalized title, publication year, and author information. The resulting multi-database corpus was analyzed with CiteSpace, VOSviewer, and R. A nested latent Dirichlet allocation (LDA) analysis was retained on the internally consistent WoSCC subset: 1, 406 records underwent relevance screening and 808 entered the final topic model. As an independent robustness analysis, non-negative matrix factorization (NMF) was applied to title-and-abstract text from all 2, 933 unique publications. Results: The three searches contributed 4, 415 records and 2, 933 unique publications after removal of 1, 482 duplicate occurrences. The corpus covered 885 sources, showed an annual growth rate of 14.7%, and peaked at 346 publications in 2021. Standardized country data identified China as the largest contributor (1, 549 documents), whereas the United States had the strongest international connectivity (total link strength [TLS], 405). Nanjing Medical University was the leading institution by output (70 documents), and Toshikazu Ushijima was the most prolific author (25 documents). Multi-database keyword mapping identified gastric cancer, microRNA, cell proliferation, signal transduction, apoptosis, inflammation, DNA methylation, tumor microenvironment, STAT3, and long non-coding RNA as central concepts. Burst detection showed an early emphasis on DNA methylation, Helicobacter pylori, and RNA interference, followed by recent cross-cancer and functional terms. The WoSCC-based six-topic LDA model remained balanced in prevalence (15.93%-18.26%) and showed significant declines in H. pylori-inflammation-precancer and DNA hypermethylation-silencing topics, with concurrent growth in immune-lncRNA, microbiota/virus-associated ncRNA, and exosomal ncRNA-cytokine themes. Independent NMF analysis of the full multi-database corpus recovered broadly concordant domains involving H. pylori-associated inflammation, ncRNA-related signaling, immune and exosomal microenvironmental processes, and DNA methylation-related epigenetic regulation. Conclusions: Multi-database integration substantially expanded the observable literature and indicated a broad shift in research attention from infection-associated methylation toward ncRNA-centered, immune, microenvironmental, and resistance-related regulatory systems. National collaboration was broader than institutional and author-level integration. The nested LDA analysis quantified the long-term reallocation of thematic attention, while independent NMF validation across the full multi-database corpus supported the robustness of the principal thematic domains.