Abstract:

Objective: To investigate the expression pattern of Erb-B2 receptor tyrosine kinase 2 (ERBB2) in bladder urothelial carcinoma (BLCA) and its clinical relevance, prognostic value, and potential molecular mechanisms, thereby providing evidence for biomarker identification and targeted therapy research in BLCA. Methods: RNA sequencing expression data and clinical information were obtained from The Cancer Genome Atlas bladder urothelial carcinoma cohort (TCGA-BLCA). Differences in ERBB2 expression between tumor and normal tissues were analyzed, and associations with American Joint Committee on Cancer (AJCC) pathological stage and tumor grade were evaluated. Receiver operating characteristic (ROC) curve analysis was performed to assess the diagnostic performance of ERBB2. Patients were stratified into high- and low-expression groups based on both the median value and the optimal cutoff, followed by Kaplan-Meier survival analysis and Cox regression to evaluate prognostic significance. Differentially expressed genes associated with ERBB2 were identified, and Kyoto Encyclopedia of Genes and Genomes (KEGG), gene ontology (GO), and single-gene gene set enrichment analysis (GSEA) were conducted. Correlations between ERBB2 and immune checkpoint molecules were further analyzed. In addition, immunohistochemistry data from the Human Protein Atlas (HPA) database and reverse transcription quantitative PCR (RT-qPCR) experiments were used to validate ERBB2 expression. Results: HPA immunohistochemistry demonstrated stronger ERBB2 staining in BLCA neoplastic tissues, and RT-qPCR confirmed elevated ERBB2 mRNA expression in BLCA neoplastic tissues. TCGA analysis showed that ERBB2 expression was significantly higher in tumor tissues than in normal tissues (P=0.005), with overall differences observed across AJCC pathological stages (P=0.004), whereas no significant difference was found between tumor grades (P=0.238). Receiver operating characteristic curve analysis indicated a moderate discriminatory ability of ERBB2 [area under the curve (AUC) =0.689]. No significant difference in overall survival was observed between high- and low-expression groups based on either the median cutoff or the optimal cutoff (P=0.240 and P=0.148, respectively), and both univariate and multivariate Cox analyses suggested that ERBB2 was not an independent prognostic factor for OS. Functional enrichment analyses revealed that ERBB2-associated differentially expressed genes were mainly enriched in cytokine-cytokine receptor interaction, interleukin 17 (IL-17) signaling pathway, phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) signaling pathway, Janus kinase/signal transducer and activator of transcription (JAK-STAT) signaling pathway, chemokine signaling pathway, inflammatory response, immune response, extracellular matrix organization, and leukocyte migration. GSEA further demonstrated positive enrichment in IL-17 signaling, PI3K/AKT signaling, and cytokine-cytokine receptor interaction pathways. Immune checkpoint analysis showed that CD274, PDCD1, CTLA4, LAG3, TIGIT, and HAVCR2 were significantly upregulated in the ERBB2 high-expression group, and ERBB2 expression was positively correlated with CD274 and CTLA4 (Spearman ρ=0.45 and 0.36, both P < 0.001). Conclusion: ERBB2 is upregulated in BLCA and is associated with AJCC pathological stage and immune checkpoint expression, showing moderate diagnostic value but limited prognostic significance. ERBB2 may contribute to BLCA progression through regulation of immune-inflammatory responses, cytokine signaling, PI3K/AKT pathway, and tumor immune microenvironment.

Key words: Urinary bladder neoplasms, Urothelial carcinoma, Genes, erbB-2, Gene expression, Immune checkpoint inhibitors, Prognosis, The Cancer Genome Atlas