Tumor-infiltrating M2 macrophages driven by specific genomic alterations are associated with prognosis in bladder cancer

The present study aimed to explore the mechanism by which the immune landscape of the tumor microenvironment influences bladder cancer. CIBERSORT and ssGSEA analyses revealed that M2 macrophages accounted for the highest proportion from 22 subsets of tumor-infiltrating immune cells and were enriched in higher histologic grade and higher pathologic stage bladder cancer and ‘basal’ subtype of muscle invasive bladder cancer (MIBC). Kaplan-Meier survival curve analysis indicated that patients with high numbers of infiltrating M2 macrophages had worse overall and disease-specific survival rates. RNA sequencing and immunohistochemistry results indicated that M2 macrophages were enriched in MIBC and promoted angiogenesis. M2 macrophage infiltration was higher in bladder cancer tissues with mutant TP53, RB transcriptional corepressor 1, phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit α, lysine methyltransferase 2A, lysine demethylase 6A and apolipoprotein B mRNA editing enzyme catalytic-polypeptide-like, but lower in tissues with mutant fibroblast growth factor receptor 3 (FGFR3), E74-like ETS transcription factor 3, PC4 and SFRS1 interacting protein 1 and transmembrane and coiled-coil domains 4. In addition, M2 macrophage infiltration was lower in the tissues with amplified FGFR3, erb-b2 receptor tyrosine kinase 2, BCL2-like 1, telomerase reverse transcriptase and tyrosine-3-monooxygenase/tryptophan-5-monooxygenase activation protein ζ, as well as in the tissues with deleted cyclin-dependent kinase inhibitor 2A, CREB binding protein, AT-rich interaction domain 1A, fragile histidine triad diadenosine triphosphatase, phosphodiesterase 4D, RAD51 paralog B, nuclear receptor corepressor 1 and protein tyrosine phosphatase receptor type D. Finally, seven micro (mi) RNAs (miR-214-5p, miR-223-3p, miR-155-5p, miR-199a-3p, miR-199b-3P, miR-146b-5p, miR-142-5p) which were expressed differentially in at least three mutant genes and were positively correlated with M2 macrophage infiltration as well as expressed highly in high grade bladder cancer were identified. Overall, the present study concluded that M2 macrophages are the predominant tumor-infiltrating immune cell in bladder cancer and differentially expressed miRNAs due to cancer-specific genomic alterations may be important drivers of M2 macrophage infiltration. These findings suggested that M2 macrophage infiltration may serve as a potential immunotherapy target in bladder cancer.