ABSTRACT: RNA binding proteins (RBPs) are increasingly recognized as potential factors influencing the advancement, prognostication, and immune response in various solid tumors. Nevertheless, the comprehensive understanding of RBM34's biological mechanisms within the tumor microenvironment remains incomplete, necessitating further systematic pan-cancer investigations to ascertain its diagnostic, prognostic, and immunological significance. In this study, the TCGA, CCLE, HPA, GTEX, and TARGET databases were employed to analyze the expression abundance and subcellular localization of RBM34 in diverse tumor types. Kaplan-Meier survival analyses were used to investigate the impact of RBM34 on clinical prognosis. We implemented the TISIDB portal, CIBERSORT, and ESTIMATE algorithms to assess the correlation between RBM34 expression and immunomodulators, chemokines, and tumor-infiltrating lymphocytes (TILs) in both pan-cancer and osteosarcoma. The CGP database was applied to evaluate the half-maximal inhibitory concentrations of targeted drugs, while TMB, MSI, and MMR were utilized to predict the efficacy of tumor immunotherapy. Furthermore, an RBM34-derived prognostic index (RDPI) was constructed for osteosarcoma patients and linked to outcomes and immune status. Finally, we examined the modulation of RBM34 knockdown on osteosarcoma proliferation and migration capacity. Our results indicate that RBM34 was predominantly localized in the nucleus and differentially expressed in most human cancer types. Kaplan-Meier curve analysis and Cox regression demonstrated that RBM34 expression affected four survival metrics including overall survival (OS) in multiple tumors and was an independent prognostic factor for osteosarcoma. In immunological characterization, RBM34 expression was significantly associated with pan-cancer immunomodulator-related molecules, lymphocyte subpopulation infiltration, and biomarkers of immunotherapy response. Subsequent in vitro experiments provided additional evidence that the suppression of RBM34 impeded the migratory and invasive capabilities of osteosarcoma. Moreover, the utilization of RDPI demonstrated its reliability in prognosticating patient outcomes and estimating the individual immune landscape. Marked differences in multiple TILs (including naive B cells, CD8+ T cells, resting dendritic cells, and activated CD4+ memory T cells) and cancer-associated fibroblast proportion were observed in diverse RDPI score subgroups. Generally, RBM34 exhibited associations with clinical prognosis, immune infiltration, and immunotherapy across various cancer types, and may also serve as a viable therapeutic target for osteosarcoma.
