Crosstalk Between CTSB+ Glioblastoma Cells and S100A10+ Macrophages: A Self-Reinforcing Circuit Promotes Immune Evasion and Limits Response to Immunotherapy.

BACKGROUND: Glioblastoma (GBM) establishes a highly immunosuppressive microenvironment through intricate molecular dialogues with tumor-associated macrophages (TAMs), contributing to immunotherapy resistance. METHODS: We integrated advanced biological network analyses with multimodal AI to identify CTSB as a key biomarker. Functional validation included GBM-macrophage co-culture systems, chromatin immunoprecipitation (ChIP), dual-luciferase reporter assays, molecular docking, and co-immunoprecipitation (Co-IP). In vivo experiments employed orthotopic (GL261 and CT-2A) and subcutaneous GBM models with lentivirus-mediated CTSB knockdown and anti-PD-1 therapy. Tumor microenvironment dynamics were assessed via in-house generated single-cell RNA sequencing and multiplex immunofluorescence. RESULTS: Cathepsin B (CTSB) was identified as a critical driver of aggressive GBM progression and poor outcomes. Mechanistically, macrophage-derived IL-6 activates STAT3 in tumor cells, upregulating CTSB expression. Structural and Co-IP analyses revealed CTSB, secreted by tumor cells, binds the C-terminus of macrophage S100A10, reinforcing IL-6 secretion, forming a feedforward loop between CTSB+ GBM cells and S100A10+ macrophages. This loop enhances tumor growth, invasion, and immune evasion via PD-L1 upregulation. In vivo, CTSB blockade reduced TAM activation, increased CD8+ T cell infiltration, and synergized with anti-PD-1 therapy. CONCLUSIONS: This study unveils a targetable GBM-macrophage signaling axis, proposing CTSB inhibition as a strategy to enhance immunotherapy efficacy in GBM patients.