Intestinal toxicity to CTLA-4 blockade driven by IL-6 and myeloid infiltration

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STAT3 INHIBITS TYPE I INTERFERON SIGNALING IN TYPE I CONVENTIONAL DENDRITIC CELLS

Conventional dendritic cells (cDCs) are an essential immune population, responsible for controlling adaptive immunity and tolerance. Recently, type I cDCs (cDC1s) have been delineated as a distinct cDC subset, uniquely responsible for coordinating T cell-mediated immunity against pathogens and tumors. Although the importance of cDC1s is now well established, the mechanisms that regulate cDC1 function remain largely unknown. Signal Transducer and Activator of Transcription 3 (STAT3) mediates the intracellular signaling of interleukin 10 (IL-10), an immunosuppressive cytokine. Therefore, we hypothesized that STAT3 and IL-10 inhibit cDC1 function and induction of T cell-mediated immunity. Herein, we show that IL-10 inhibits polyinosinic:polycytidylic acid (poly I:C)-induced cDC1 maturation in a STAT3-dependent manner. Transcriptome analyses further revealed that although poly I:C induces numerous inflammatory pathways in cDC1s, interferon (IFN) signaling was selectively inhibited by IL-10 and STAT3. Furthermore, assessment of the relative contribution of each IFN type indicated that type I IFN is the primary target of STAT3-mediated inhibition. To determine the impact of these signaling events on cDC1 induction of T cell-mediated immunity, we utilized a cell-based cDC1 anti-tumor vaccine strategy. STAT3 and IL-10 were found to impede the ability of cDC1 vaccination to restrain tumor growth. In addition, both CD8+ T cell and CD4+ T helper cell responses induced by cDC1 vaccination were inhibited by STAT3. Taken together, we conclude that STAT3 inhibits cDC1-induced anti-tumor immunity and cDC1 type I IFN signaling. As cDC1s are essential for the induction of T cell-mediated immunity, these findings could provide rationale for development of novel immunotherapies for cancer and other immune diseases

Vaccine efficacy against primary and metastatic cancer with in vitro-generated CD103+ conventional dendritic cells

BackgroundType 1 conventional dendritic cells (cDC1s) possess efficient antigen presentation and cross-presentation activity, as well as potent T cell priming ability. Tissue-resident cDC1s (CD103+ cDC1s in mice, CD141+ cDC1s in humans) are linked with improved tumor control, yet the efficacy of immunotherapy using this population is understudied.MethodsWe generated murine CD103+ cDC1s in vitro and examined their expression of cDC1-related factors, antigen cross-presentation activity, and accumulation in tumor-draining lymph nodes (TdLNs). The antitumor efficacy of the in vitro-generated CD103+ cDC1s was studied in murine melanoma and osteosarcoma models. We evaluated tumor responses on vaccination with CD103+ cDC1s, compared these to vaccination with monocyte-derived DCs (MoDCs), tested CD103+ cDC1 vaccination with checkpoint blockade, and examined the antimetastatic activity of CD103+ cDC1s.ResultsIn vitro-generated CD103+ cDC1s produced cDC1-associated factors such as interleukin-12p70 and CXCL10, and demonstrated antigen cross-presentation activity on stimulation with the toll-like receptor 3 agonist polyinosinic:polycytidylic acid (poly I:C). In vitro-generated CD103+ cDC1s also migrated to TdLNs following poly I:C treatment and intratumoral delivery. Vaccination with poly I:C-activated and tumor antigen-loaded CD103+ cDC1s enhanced tumor infiltration of tumor antigen-specific and interferon-γ+ CD8+ T cells, and suppressed melanoma and osteosarcoma growth. CD103+ cDC1s showed superior antitumor efficacy compared with MoDC vaccination, and led to complete regression of 100% of osteosarcoma tumors in combination with CTLA-4 antibody-mediated checkpoint blockade. In vitro-generated CD103+ cDC1s effectively protected mice from pulmonary melanoma and osteosarcoma metastases.ConclusionsOur data indicate an in vitro-generated CD103+ cDC1 vaccine elicits systemic and long-lasting tumor-specific T cell-mediated cytotoxicity, which restrains primary and metastatic tumor growth. The CD103+ cDC1 vaccine was superior to MoDCs and enhanced response to immune checkpoint blockade. These results indicate the potential for new immunotherapies based on use of cDC1s alone or in combination with checkpoint blockade

Humanization of JAA-F11, a Highly Specific Anti-Thomsen-Friedenreich Pancarcinoma Antibody and In Vitro Efficacy Analysis

JAA-F11 is a highly specific mouse monoclonal to the Thomsen-Friedenreich Antigen (TF-Ag) which is an alpha-O-linked disaccharide antigen on the surface of ~80% of human carcinomas, including breast, lung, colon, bladder, ovarian, and prostate cancers, and is cryptic on normal cells. JAA-F11 has potential, when humanized, for cancer immunotherapy for multiple cancer types. Humanization of JAA-F11, was performed utilizing complementarity determining regions grafting on a homology framework. The objective herein is to test the specificity, affinity and biology efficacy of the humanized JAA-F11 (hJAA-F11). Using a 609 target glycan array, 2 hJAA-F11 constructs were shown to have excellent chemical specificity, binding only to TF-Ag alpha-linked structures and not to TF-Ag beta-linked structures. The relative affinity of these hJAA-F11 constructs for TF-Ag was improved over the mouse antibody, while T20 scoring predicted low clinical immunogenicity. The hJAA-F11 constructs produced antibody-dependent cellular cytotoxicity in breast and lung tumor lines shown to express TF-Ag by flow cytometry. Internalization of hJAA-F11 into cancer cells was also shown using a surface binding ELISA and confirmed by immunofluorescence microscopy. Both the naked hJAA-F11 and a maytansine-conjugated antibody (hJAA-F11-DM1) suppressed in vivo tumor progression in a human breast cancer xenograft model in SCID mice. Together, our results support the conclusion that the humanized antibody to the TF-Ag has potential as an adjunct therapy, either directly or as part of an antibody drug conjugate, to treat breast cancer, including triple negative breast cancer which currently has no targeted therapy, as well as lung cancer