Decoding hypoxia-driven microenvironment remodeling in bladder cancer reveals TPST1 as a key driver of metastasis

Hypoxia is a key feature of the bladder cancer tumor microenvironment, but its cellular organization, prognostic value, and functional effectors remain incompletely defined. Here, we integrated single-cell RNA sequencing, bulk transcriptomic cohorts, machine-learning modeling, immune deconvolution, spatial transcriptomics, and functional experiments to characterize hypoxia-driven tumor microenvironment remodeling in bladder cancer. Single-cell analysis showed that hypoxia-related activity was enriched in malignant epithelial and stromal compartments and was associated with altered tumor–stromal communication. In bulk cohorts, high hypoxia activity was linked to poor overall survival and activation of aggressive biological programs. By integrating hypoxia-associated differentially expressed genes, WGCNA-derived module genes, and survival-related genes, we developed a six-gene Bladder Cancer Hypoxia-Related Signature (BCHRS) using an optimized CoxBoost plus stepwise Cox model. BCHRS consistently stratified patient survival across TCGA-BLCA and two independent validation cohorts and provided prognostic information beyond conventional clinicopathological variables. High BCHRS scores were associated with epithelial–mesenchymal transition, extracellular matrix remodeling, metabolic reprogramming, and an immunosuppressive immune microenvironment. Spatial transcriptomics further prioritized TPST1 as a tumor-localized hypoxia-associated effector. Functional experiments confirmed that TPST1 promoted bladder cancer cell proliferation, migration, invasion, EMT-related changes, xenograft tumor growth, and experimental lung colonization. These findings define BCHRS as a hypoxia-related prognostic framework and identify TPST1 as a functional effector of aggressive bladder cancer progression.