InVivoMAb recombinant Flt-3L-Ig (hum/hum)

Diffuse midline glioma (DMG) is a devastating pediatric brain tumor. The oncolytic adenovirus Delta-24-RGD has shown promising efficacy and safety in DMG patients but is not yet curative. Thus, we hypothesized that activating dendritic cells (DCs) through the CD40 costimulatory receptor could increase antigen presentation and enhance the anti-tumor effect of the virus, resulting in long-term responses. This study shows that the intratumoral co-administration of Delta-24-RGD and a CD40 agonistic antibody is well tolerated and induces long-term anti-tumor immunity, including complete responses (up to 40%) in DMG preclinical models. Mechanistic studies revealed that this therapy increased tumor-proliferating T lymphocytes and proinflammatory myeloid cells, including mature DCs with superior tumor antigen uptake capacity. Moreover, the lack of cross-presenting DCs and the prevention of DC recruitment into the tumor abolish the Delta-24-RGD+anti-CD40 anti-DMG effect. This approach shows potential for combining virotherapy with activating antigen-presenting cells in these challenging tumors.

Proliferating tumor cells take up glutamine for anabolic processes, engendering glutamine deficiency in the tumor microenvironment. How this might impact immune cells is not well understood. Using multiple mouse models of soft tissue sarcomas, glutamine antagonists, as well as genetic and pharmacological inhibition of glutamine utilization, we found that the number and frequency of conventional dendritic cells (cDCs) is dependent on microenvironmental glutamine levels. cDCs comprise two distinct subsets-cDC1s and cDC2s, with the former subset playing a critical role in antigen cross-presentation and tumor immunity. While both subsets show dependence on glutamine, cDC1s are particularly sensitive. Notably, glutamine antagonism did not reduce the frequency of DC precursors but decreased the proliferation and survival of cDC1s. Further studies suggest a role of the nutrient sensing mechanistic target of rapamycin (mTOR) signaling pathway in this process. Taken together, these findings uncover glutamine dependence of cDC1s that is coopted by tumors to escape immune responses.

Pancreatic adenocarcinoma (PDAC) is one the most intractable cancers, in part due to its highly inflammatory microenvironment and paucity of infiltrating dendritic cells (DCs). Here, we find that genetic ablation or antibody blockade of tumor necrosis factor receptor 1 (TNFR1) enhanced intratumor T cell activation and slowed PDAC growth. While anti-PD-1 checkpoint inhibition alone had little effect, it further enhanced intratumor T cell activation in combination with anti-TNFR1. The major cellular alteration in the tumor microenvironment in the absence of TNFR1 signaling was a large increase in DC number and immunostimulatory phenotype. This may reflect a direct effect on DCs, because TNF induced TNFR1-dependent apoptosis of bone-marrow-derived DCs. The therapeutic response to anti-TNFR1 alone was superior to the combination of DC-activating agonistic anti-CD40 and Flt3 ligand (Flt3L). These observations suggest that targeting TNFR1, perhaps in concert with other strategies that promote DC generation and mobilization, may have therapeutic benefits.

Immunosurveillance of cancer requires the presentation of peptide antigens on major histocompatibility complex class I (MHC-I) molecules1-5. Current approaches to profiling of MHC-I-associated peptides, collectively known as the immunopeptidome, are limited to in vitro investigation or bulk tumour lysates, which limits our understanding of cancer-specific patterns of antigen presentation in vivo6. To overcome these limitations, we engineered an inducible affinity tag into the mouse MHC-I gene (H2-K1) and targeted this allele to the KrasLSL-G12D/+Trp53fl/fl mouse model (KP/KbStrep)7. This approach enabled us to precisely isolate MHC-I peptides from autochthonous pancreatic ductal adenocarcinoma and from lung adenocarcinoma (LUAD) in vivo. In addition, we profiled the LUAD immunopeptidome from the alveolar type 2 cell of origin up to late-stage disease. Differential peptide presentation in LUAD was not predictable by mRNA expression or translation efficiency and is probably driven by post-translational mechanisms. Vaccination with peptides presented by LUAD in vivo induced CD8+ T cell responses in naive mice and tumour-bearing mice. Many peptides specific to LUAD, including immunogenic peptides, exhibited minimal expression of the cognate mRNA, which prompts the reconsideration of antigen prediction pipelines that triage peptides according to transcript abundance8. Beyond cancer, the KbStrep allele is compatible with other Cre-driver lines to explore antigen presentation in vivo in the pursuit of understanding basic immunology, infectious disease and autoimmunity.