Multi-omics study on tumor-associated macrophages remodeling the tumor microenvironment via the CXCL5-CXCR2 axis to drive immune escape in bladder cancer

Background: PD-1/L1 inhibitors improve the prognosis of patients with advanced bladder cancer, but the clinical remission rate remains below 25%. Tumor-associated macrophages (TAMs) and chemokines are critical in the tumor microenvironment (TME), affecting tumor progression, immunotherapeutic efficacy, and patient prognosis; however, their underlying mechanisms remain unclear. This study exhibits innovation by adopting a tumor microenvironment perspective to investigate the interaction mechanism between bladder cancer cells and tumor-associated macrophages, as well as factors affecting the efficacy of immunotherapy. Methods: Single-cell sequencing, bulk sequencing, and in vivo experiments identified TAM infiltration characteristics, their impacts on prognosis and immunotherapy. In vitro, we established a co-culture model and performed targeted metabolomic sequencing on TAMs. Xenograft and tail vein metastasis models were used to investigate the function of CXCL5-CXCR2 axis in bladder TME. Results: M2 macrophages were positively correlated with the clinical staging of bladder cancer and resistance to immunotherapy. Single-cell sequencing data revealed that CXCL5⁺ tumor-associated macrophages (TAMs) were associated with poor overall survival but a favorable response to immunotherapy, whereas FOLR2⁺ TAMs were linked to both poor overall survival and immunotherapy resistance. The CXCL5-CXCR2-NF-κB axis was upregulated in the co-culture system, which promoted PD-L1 expression in both tumor cells and TAMs, the formation of an immunosuppressive tumor microenvironment (TME), as well as the migration, proliferation, and lung metastatic potential of bladder cancer cells. Additionally, this axis enhanced IDO1 expression in macrophages and improved the efficacy of immunotherapy for bladder cancer. Conclusion: The CXCL5-CXCR2 axis mediates bladder cancer cell-macrophage crosstalk: macrophages promote tumor growth, immune escape, and cisplatin tolerance; tumor cells induce macrophage polarization and reshape immunosuppressive TME. Additionally, this axis drives bladder cancer malignant progression and enhances immunotherapy efficacy.