DHX15 as a novel immune-related prognostic biomarker in breast cancer: An integrated bioinformatics analysis with in vitro functional validation

Abstract

Breast cancer (BC) is a disease that occurs relatively frequently, and its prognosis and treatment outcomes are not optimal at present. Identifying novel BC biomarkers and therapeutic targets is key. DEAH-box helicase 15 (DHX15) is an RNA helicase that exhibits enhanced activity and is closely associated with tumorigenic potential. Alternative splicing is widely dysregulated in BC. However, the biological function of DHX15 in BC, in addition to its underlying molecular mechanisms, remain unclear. DHX15, a key RNA helicase involved in splicing regulation, was therefore selected to explore whether it modulates the malignant progression of BC. The present study therefore analyzed the DHX15 expression profile in BC using the Tumor Immune Estimation Resource database. Kaplan-Meier plotter database was utilized to investigate the prognostic value of DHX15 in BC. The Cancer Genome Atlas-BRCA database was utilized to investigate the association between DHX15 and immune infiltration, as well as the expression of immune biomarkers, within the tumor microenvironment. The potential biological functions of DHX15 in BC were also investigated using Gene Ontology (GO) enrichment analysis, Kyoto encyclopedia of genes and genomes pathway analysis (KEGG) and single-cell functional analysis. GO and KEGG enrichment analyses were performed via the GSEA module embedded in the LinkedOmics database. Single-cell functional analysis was performed using the Human Proteome Atlas database and the CancerSEA database. Concurrently, the expression and function of DHX15 in BC was validated. MDA-MB-231 cells were transfected with a DHX15 knockdown plasmid and MCF-7 cells with an overexpression plasmid, and Transwell assays, plate cloning and scratch assays were performed on the established cell lines. The present findings revealed that the DHX15 expression levels in BC were notably higher compared with those in normal tissues. Furthermore, the expression of DHX15 was associated with immune checkpoints (such as PDCD1, LAG3 and GZMB) and immune cell infiltration (such as T helper cells and central memory T cells) in BC, as determined by single-sample Gene Set Enrichment Analysis and CIBERSORT analyses. In vitro experiments suggested that inhibiting DHX15 notably suppressed the migration, invasion and proliferation of MDA-MB-231 cells. Collectively, these findings suggest that the high expression of DHX15 in BC is associated with worse prognosis and immune cell infiltration, potentially by functionally promoting tumor cell proliferation, migration and invasion.