Clinical relevance of Nectin-4 downregulation and biological changes caused by cytotoxic chemotherapy in bladder cancer.

Introduction: Mechanism underlying resistance to enfortumab vedotin (EV) and prognostication of Nectin-4 expression in muscle-invasive bladder cancer (MIBC) remains unclear.

Methods: We generated gemcitabine-resistant HT-1376 and cisplatin-resistant HT-1376 cells generated from parental HT1376 cells (derived from MIBC). Transcriptome analysis was conducted to explore the biological function of differentially expressed genes detected in chemoresistant HT-1376 cells compared to parental HT-1376. In 70 patients with MIBC undergoing radical cystectomy, unsupervised hierarchical clustering was performed using immunohistochemical staining pattern with GATA3, KRT20, KRT5/6, KRT14, and Nectin-4 expression derived from the gene expression-based Nectin-4-modified NanoString molecular classification: Luminal-Nec4-High, Luminal-Nec4-Low, Basal-Nec4-High, and Basal-Nec4-Low subgroups.

Results: We found significant downregulation of Nectin-4 expression along with epithelial-to-mesenchymal transition in chemoresistant HT-1376 cells. Exogenous expression of NECTIN4 in chemoresistant HT-1376 cells partially restored sensitivity to EV. RNA seq identified differentially expressed genes, including Nectin-4 and small proline-rich proteins, downregulated in chemoresistant HT-1376 cells. Over-representation analysis using GO and KEGG revealed upregulation of gene sets enriched for ribosome biogenesis-related pathways in chemoresistant HT-1376 cells. Nectin-4-modified molecular subtype resulted in better stratification of survival-the Luminal-Nec4-High subgroup had the best and the Basal-Nec4-Low subgroup had the worst prognosis. Comparing molecular subtypes of MIBC cells between transurethral resection specimens and matched radical cystectomy specimens revealed that 43% of neoadjuvant chemotherapy-treated patients with luminal subtype tumors showed a marked shift to the basal subtype in the cystectomy specimens.

Conclusion: The clinical utility of Nection-4, associated molecules, and Nectin-4-modified molecular subtype need to be studied for better management strategies for MIBC.