Clinical significance and functional characterization of RRN3 in gastric cancer: insights from pan-cancer analysis and experimental validation.

Introduction: RRN3 is a nucleolar protein required for ribosome biogenesis, but its role in cancer remains insufficiently defined. This study aimed to systematically evaluate the clinical relevance, molecular characteristics, immune-related features, and biological function of RRN3 across cancers, with a particular focus on gastric cancer (GC). Methods: Public databases were used to analyze RRN3 expression, clinicopathological associations, survival outcomes, ROC curves, genomic alterations, epigenetic and epitranscriptomic features, immune-related characteristics, drug-response profiles, and co-expression networks. Functional enrichment analysis and a putative ceRNA regulatory network were further explored. Clinical tissue validation, in vitro rescue experiments, and in vivo xenograft assays were used to evaluate the involvement of RRN3 in GC progression. Results: Pan-cancer analysis showed that RRN3 was upregulated in multiple tumor types, including GC, and that high RRN3 expression was associated with unfavorable overall survival in several cancers. In GC, RRN3 expression was associated with RNA methylation regulators, immune checkpoint genes, tumor mutation burden, microsatellite instability, immune cell infiltration, and drug-response-related signatures. Enrichment analyses suggested that RRN3-associated genes were mainly involved in nucleocytoplasmic transport, spliceosome function, mRNA surveillance, and ribosome biogenesis. Clinical validation showed that RRN3 was upregulated in GC tissues and associated with several clinicopathological features related to tumor progression. Functional experiments showed that RRN3 knockdown inhibited GC cell proliferation, colony formation, migration, and invasion, whereas RRN3 re-expression partly reversed these effects. In vivo xenograft experiments further supported the role of RRN3 in promoting tumor growth. Discussion: These findings suggest that RRN3 is associated with GC progression and may represent a candidate molecule for further investigation in GC.