Multi-omics dissection of tumor-related leukocytosis in urothelial carcinoma identifies IL13RA2 as a key driver

Background: Tumor-related leukocytosis (TRL), driven largely by neutrophil overproduction, is associated with aggressive disease, treatment resistance, and poor survival across solid tumors. In metastatic urothelial carcinoma (mUC), patients with TRL experience particularly poor outcomes under immune checkpoint inhibitor (ICI) therapy, suggesting an immune-suppressive tumor microenvironment. However, the molecular basis linking TRL to ICI resistance remains unclear. Methods: We retrospectively evaluated mUC patients receiving ICIs to assess the prognostic role of TRL. RNA from 35 tumors underwent NanoString profiling to identify leukocytosis-associated genes. IL13RA2 and related candidates were validated across UC cell lines by qPCR, western blotting, and functional assays including proliferation, migration, cytokine analysis, and neutrophil chemotaxis. Transcriptional programs regulated by IL13RA2 were defined using Clariom S microarray. Results: Patients with baseline leukocytosis (WBC >10,000/µL) showed significantly worse overall survival, confirming TRL as a negative prognostic factor during ICI therapy. High-WBC tumors displayed a distinct inflammatory signature, with IL13RA2 among the most upregulated genes. IL13RA2 expression strongly associated with neutrophil enrichment in TCGA BLCA (Pearson r = 0.41; TIMER ρ = 0.199) and was validated in the ICI-treated GSE176307 cohort, where IL13RA2-high tumors exhibited increased neutrophil and myeloid fractions. Functionally, IL13RA2 knockdown reduced proliferation, migration, and wound-healing capacity in UMUC3 and T24 cells. Microarray analysis identified reproducible IL13RA2-regulated gene sets enriched for cytokine, inflammatory, motility, and chemotaxis pathways. Conditioned media from IL13RA2-expressing cells robustly induced migration of purified neutrophils, whereas IL13RA2 depletion markedly impaired neutrophil chemotaxis. IL13RA2 silencing suppressed JAK1/2-STAT3 activity and reduced multiple pro-inflammatory cytokines and chemokines, including CXCL5, CXCL6, CXCL8, CCL3, and CCL4. Conclusions: TRL is a potent negative prognostic factor in ICI-treated mUC. IL13RA2 emerges as a central driver linking leukocytosis to immune resistance by promoting inflammatory signaling, cytokine production, and myeloid recruitment. These findings identify IL13RA2 as a key mediator of TRL and a potential therapeutic target to overcome myeloid-driven ICI resistance in urothelial carcinoma.