Integrin α5β1‐mediated multicellular crosstalk in the tumor microenvironment drives bladder cancer progression and reveals targetable vulnerabilities

Abstract

Bladder cancer (BCa) progression is driven by complex interactions within the tumor microenvironment, yet the underlying multicellular communication networks remain poorly defined. Here, we integrated bulk, single‐cell, and spatial transcriptomic data with multiplexed immunofluorescence to construct a comprehensive cellular atlas across normal urothelium, precancerous lesions, and progressive BCa. We identified a stemness‐associated malignant epithelial population (Cluster 1_SDC1), a prognostically unfavorable subset of POSTN+ myofibroblastic cancer‐associated fibroblasts (mCAFs), and immunosuppressive monocytic myeloid‐derived suppressor cells (M‐MDSCs), all enriched in high‐grade tumors. Spatial mapping revealed a coordinated signaling cascade wherein POSTN+ mCAFs and M‐MDSCs co‐localize and engage integrin α5β1 on tip endothelial cells through FN1 and NAMPT, collectively driving angiogenesis. In turn, tip endothelial cells reinforce tumor stemness through downstream COL4A1/2–SDC1 signaling. Therapeutically, targeting integrin α5β1 with RGD peptide suppressed tumor growth and vascularization, while its combination with hydrogel‐based delivery and immune checkpoint blockade elicited broad‐spectrum antitumor responses. These findings uncover a spatially coordinated immune–stroma–tumor signaling cascade and establish integrin α5β1 as a central therapeutic target, providing a rationale for stroma‐directed combination strategies in progressive BCa.