Work

942 cDC1-independent tumor rejection: CD45-targeted IL-12 reveals a cDC2–CD4 + T cell axis as a driver of lung tumor immunity

Year: 2026

Type: conference-paper

Abstract: Background Interleukin-12 (IL-12) is a potent immunostimulatory cytokine produced by dendritic cells (DCs) that primes anti-tumor T cell responses; however, its clinical translation is hindered by systemic toxicity and a short half-life. 1 Using antibody-cytokine conjugates to target IL-12 to CD45 improves immune cell targeting and extends cytokine half-life.2 While previous studies have demonstrated that CD45-targeted IL-12 (αCD45-IL12) is highly efficacious in flank tumor models when dosed intratumorally,2 lung tumors are frequently refractory to immunotherapy due to tissue-specific immune suppression and are not amenable to intratumoral delivery.3 We therefore investigated the efficacy and mechanism of systemically administered αCD45-IL12 in preclinical lung cancer models.Methods αCD45-IL-12 was recombinantly produced in HEK293 cells and purified by protein A and size exclusion chromatography. Syngeneic KP.SIY tumors (Kras G12D p53−/− expressing model antigen SIYRYYGL) were established by tail vein injection and treated intraperitoneally on days 7 and 11 post-inoculation. Immunophenotyping was performed by scRNA-Seq, flow cytometry, IFN-γ ELISpot. Mechanism was interrogated using bone marrow chimeras, immune cell KO mouse strains, and antibody-mediated immune cell depletions. A lung cancer GEMM was established by intratracheal lentiviral delivery of Cre recombinase and model antigen Rpl18 into KrasG12D/+ p53fl/fl mice, with tumor burden quantified histologically at week 12.Results KP.SIY lung tumors progressed rapidly and were refractory to immune checkpoint blockade. Intraperitoneal administration of low-dose αCD45-IL12 reduced tumor burden 4-fold and conferred a significant survival benefit over untreated mice ( figure 1). Treatment with an untargeted IgG-IL12 control was ineffective, demonstrating the necessity of CD45 targeting. αCD45-IL12 treatment similarly reduced tumor burden 2-fold in the KP GEMM. Mechanistic analysis revealed that αCD45-IL12 enhanced activation of SIY-tetramer+ CD8+ T cells. However, therapeutic efficacy was fully preserved in BATF3−/− mice lacking cDC1s even though these mice fail to prime SIY-reactive CD8+ T cells. IFN-γ ELISpot and flow cytometry analyses demonstrated robust priming of CD4+ T cells against KP tumor antigens. Critically, αCD45-IL12 failed to induce CD4+ T cell priming and lost efficacy in Δ1+2+3 mice lacking cDC2s, establishing the cDC2-CD4+ T cell axis as required for therapeutic efficacy (figure 2).Conclusions These findings demonstrate that systemic αCD45-IL12 is an effective single-agent immunotherapy in checkpoint-refractory lung cancer models. Contrary to the canonical cDC1–CD8 + T cell paradigm, efficacy is driven by a cDC2–CD4+ T cell axis. These results reveal an underappreciated role for cDC2s in IL-12-mediated anti-tumor immunity and identify the cDC2–CD4+ T cell axis as a novel therapeutic target for lung cancer immunotherapy.Acknowledgements We thank the Koch Institute’s Swanson Biotechnology Core Facility and MIT BioMicro Center for technical support, and Lauren Duhamel for providing immunocytokines. This work was supported by an NIH K00 fellowship.References Mirlekar B, Pylayeva-Gupta Y. IL-12 Family Cytokines in Cancer and Immunotherapy. Cancers 2021;13(2):2.Santollani L, Maiorino L, Zhang YJ, Palmeri JR, Stinson JA, Duhamel LR, et al. Local delivery of cell surface-targeted immunocytokines programs systemic antitumor immunity. Nat Immunol. 2024;25:1820–9.Horton BL, Morgan DM, Momin N, Zagorulya M, Torres-Mejia E, Bhandarkar V, et al. Lack of CD8+ T cell effector differentiation during priming mediates checkpoint blockade resistance in non–small cell lung cancer. Sci Immunol. 2021;6(64):eabi8800.Ethics Approval All mouse experiments were approved by MIT’s Committee on Animal Care (CAC) – PHS Animal Welfare Assurance # D16-00078 (A3125-01).Abstract 942 Figure 1CD45-targeted IL-12 enhances survivalAbstract 942 Figure 2cDC2 are required for efficacy and T cell priming. (A) IFNg ELISpot analysis reveales that immunocytokine treatment fails to induce T cell priming in mice lacking cDC2s; (B) Therapuetic efficacy of the immunocytokine is lost in a genetic mouse model lacking cDC2s

Source: Journal for ImmunoTherapy of Cancer

DOI: 10.1136/jitc-2026-sitc2026.0942