Functional regulation of lymphoid cells by IL-1R8 targeting in cancer

Interleukin-1 receptor 8 (IL-1R8) is an atypical Interleukin-1 receptor (ILR) family member that mitigates inflammatory responses by dampening ILR and Toll-like receptor (TLR) signaling. Studies conducted on IL-1R8-deficient NK cells established its key role as immune checkpoint and negative regulator of IL-18-dependent activation. In particular, IL-1R8-deficiency unleashes NK cell-mediated immune surveillance against hematogenous metastasis, liver cancer and viral dissemination. However, the function of IL-1R8 in T lymphocytes remains poorly characterized, and therapeutic strategies selectively targeting IL-1R8 in human lymphocytes are still lacking. Combining transcriptomic analysis, high dimension flow cytometry, genetic silencing, and in vivo models, we investigated IL-1R8 expression and function in CD8+ T cells and in T- and NK-cell based immunotherapies. RNA-seq analysis revealed that IL-1R8-deficient CD8+ T cells undergo profound transcriptional reprogramming upon cytokine stimulation, with induction of effector molecules, cytokine receptors and signaling mediators. Gene-set enrichment analysis indicated a metabolic switch from oxidative phosphorylation to glycolytic and mTORC1-driven effector programs. Mechanistically, IL-1R8 limited IL-18-mediated Type-1 polarization by affecting the transcription factor T-bet, thereby regulating Interferon-γ (IFNγ) and Granzyme B (GZMB) expression. Unexpectedly, IL-1R8 further controlled the IL-2/EOMES/IL-2R signaling axis, tuning cell-autonomous mechanisms sustained by IL-2 autocrine signaling, through still undefined molecular mechanisms. Functionally, IL-1R8 deficiency led to superior anti-tumor immune resistance against colon carcinoma and fibrosarcoma by enhancing CD8+ T cell fitness, accelerating maturation/proliferation kinetics and increasing tumoricidal potential independently of antigen presenting cells. Relevant to adoptive T cell therapy, IL-1R8-deficient OT-I cells displayed enhanced proliferation and tumoricidal capacity, improving adoptive T-cell therapy efficacy. Combination with PD-1 blockade further increased tumor control in colon carcinoma and fibrosarcoma models. To translate these findings to humans, we generated an anti-human IL-1R8 monoclonal antibody, which revealed that IL-1R8 is upregulated during NK and CD8+ T cell maturation in both healthy donors and cancer patients. Treatment with our anti-IL-1R8 monoclonal antibody boosted cytokine-driven cytokine secretion and cytotoxicity in human NK, CD8+ T cells and CAR-T cells. Finally, CRISPR/Cas9-mediated IL-1R8 silencing in CAR-T cells accelerated effector maturation while maintaining antitumor activity against B-cell lymphoma. Overall, our findings reveal a profound impact of IL-1R8 deficiency or blockade on CD8+ T cell biology, enhancing cytokine-driven activation and strengthening antitumor immunity. By acting as a negative regulator in both NK and CD8⁺ T cells, IL-1R8 emerges as a druggable checkpoint whose targeting may potentiate T cell–based therapies and complement PD-1 blockade in cancer immunotherapy.