IL-4 mediated TAP2 downregulation is a dominant and reversible mechanism of immune evasion and immunotherapy resistance in non-small cell lung cancer

Resistance to both naturally occurring anti-cancer immunity and to immunotherapy is common in patients with aggressive non-small cell lung cancer (NSCLC). Recent studies indicate a role of loss of the HLA class-I antigen presentation machinery (APM) protein β-2-microglobulin in acquired resistance to immune checkpoint blockers. However, the mechanisms, functional consequences and therapeutic potential of APM defects in NSCLC remain poorly understood. Using multiplexed immunofluorescence, we spatially mapped CD8+ effector Tumor-Infiltrating Lymphocytes (TILs) and the APM components TAP1 and TAP2 in 819 baseline/pre-treatment NSCLCs from patients treated with and without PD-1 axis blockers in 4 independent cohorts. The impact of TAP1/2 silencing in lung cancer cells using siRNAs and CRISPR/Cas9 was studied using transcriptomic analysis, phosphoprotein arrays, ATAC-sequencing, measurement of surface HLA-peptide complexes and in vitro tumor-antigen specific T-cell killing. We established autologous co-cultures of tumor and immune cells from primary human NSCLCs to study the functional impact of IL4Rα and/or PD-1 blockade using monoclonal antibodies. A high-throughput drug screen supported the identification of compounds able to increase TAP2 expression in NSCLC cells. We identified cancer cell selective TAP2 protein downregulation in 42.4% of treatment naïve NSCLCs associated with reduced sensitivity to immune checkpoint blockers. TAP1 downregulation occurred in 24.4% of lung tumors without survival impact. Silencing of TAP2 in lung cancer cells altered key intracellular immunomodulatory pathways, limited sensitivity to proinflammatory cytokines, reduced the levels of surface peptide-HLA complexes and protected malignant cells from tumor antigen-specific T-cell killing via SOCS1 upregulation. TAP2 loss in human NSCLCs was associated with reduced TAP2 promoter chromatin accessibility and elevated IL-4 IL-4 expression. Treatment with IL-4 reduced TAP2 levels and the chromatin accessibility of the TAP2 gene promoter in NSCLC cells and reproduced all the functional consequences of TAP2 loss. In intact human NSCLC, IL-4 IL-4 transcripts were detected in intratumoral myeloid cells and IL-4Rα blockade increased human NSCLC cell killing by autologous TILs. Epigenetic modulators and other drugs with known anti-cancer activity increased TAP2 expression and its function in lung cancer cells. Our study reveals previously unrecognized functions of TAP2 beyond antigen presentation and establishes a reversible multi-cellular axis mediating adaptive immune evasion and immunotherapy resistance with clinical potential.