Nectin-4 Expression in Muscle-Invasive Bladder Cancer Is Associated with Growth-Related and Inflammatory Signaling Pathways

Nectin-4 has emerged as a clinically relevant target in muscle-invasive bladder cancer (MIBC), primarily because of its role in antibody–drug conjugate-based therapies. However, the broader biological context of Nectin-4 expression and its association with tumor-promoting signaling pathways in MIBC remain insufficiently characterized. In this single-institution study, Nectin-4 expression (H-score 0–300) was assessed by immunohistochemistry in two independent MIBC cohorts. Associations between Nectin-4 expression and key markers related to growth signaling, metabolic regulation, and inflammation were analyzed alongside clinicopathological characteristics. Nectin-4 expression was significantly higher in malignant tissue than in non-malignant tissue (p = 0.0016 and p = 0.0302, respectively). Nectin-4 expression was not associated with demographic or clinicopathological parameters; however, a trend toward lower expression in more advanced disease stages was observed. Significant positive correlations were identified between Nectin-4 expression and protein kinase B (p = 0.0004), cytoplasmic (p = 0.0115) and membranous somatostatin receptor 2 (p = 0.0125), insulin receptor substrate 1 (p = 0.03), and interleukin-1 receptor antagonist (IL-1RA; p = 0.0045). In contrast, a negative correlation was observed with the IL-1β/IL-1RA ratio (p = 0.0246). Although Nectin-4 expression was not significantly associated with cancer-specific or overall survival, a trend toward shorter relapse-free survival was observed in patients with lower Nectin-4 expression (p = 0.0531). In multivariate analysis, patient age, but not Nectin-4 expression, emerged as an independent prognostic factor. Although Nectin-4 expression does not appear to have independent prognostic value, its biological associations suggest that it reflects an integrated tumor-related signaling context. These findings support further investigation of Nectin-4 as part of rational, biology-driven therapeutic strategies in bladder cancer.