InVivoPlus anti-mouse PD-1 (CD279)

Therapies that harness the immune system to target and eliminate tumour cells have revolutionized cancer care. Immune checkpoint blockade (ICB), which boosts the anti-tumour immune response by inhibiting negative regulators of T cell activation1-3, is remarkably successful in a subset of cancer patients. Yet a significant proportion do not respond to treatment, emphasizing the need to understand factors influencing the therapeutic efficacy of ICB4-9. The gut microbiota, consisting of trillions of microorganisms residing in the gastrointestinal tract, has emerged as a critical determinant of immune function and response to cancer immunotherapy, with several studies demonstrating association of microbiota composition with clinical response10-16. However, a mechanistic understanding of how gut commensal bacteria influence the efficacy of ICB remains elusive. Here we use a gut commensal microorganism, segmented filamentous bacteria (SFB), which induces an antigen-specific T helper 17 (TH17) cell effector program in the small intestine lamina propria (SILP)17, to investigate how colonization with this microbe affects the efficacy of ICB in restraining distal growth of tumours sharing antigen with SFB. We find that anti-programmed cell death protein 1 (PD-1) treatment effectively inhibits the growth of implanted SFB antigen-expressing melanoma only if mice are colonized with SFB. Through T cell receptor (TCR) clonal lineage tracing, fate mapping and peptide-major histocompatability complex (MHC) tetramer staining, we identify tumour-associated SFB-specific T helper 1 (TH1)-like cells derived from the homeostatic TH17 cells induced by SFB colonization in the SILP. These gut-educated ex-TH17 cells produce high levels of the pro-inflammatory cytokines interferon (IFN)-γ and tumour necrosis factor (TNF) within the tumour microenvironment (TME), enhancing antigen presentation and promoting recruitment, expansion and effector functions of CD8+ tumour-infiltrating cytotoxic lymphocytes and thereby enabling anti-PD-1-mediated tumour control. Conditional ablation of SFB-induced IL-17A+CD4+ T cells, precursors of tumour-associated TH1-like cells, abolishes anti-PD-1-mediated tumour control and markedly impairs tumour-specific CD8+ T cell recruitment and effector function within the TME. Our data, as a proof of principle, define a cellular pathway by which a single, defined intestinal commensal imprints T cell plasticity that potentiates PD-1 blockade, and indicate targeted modulation of the microbiota as a strategy to broaden ICB efficacy.

Type 1 conventional dendritic cells (cDC1s) are unique in their efferocytosis1 and cross-presenting abilities2, resulting in antigen-specific T cell immunity3 or tolerance4-8. However, the mechanisms that underlie cDC1 tolerogenic function remain largely unknown. Here we show that the erythropoietin receptor (EPOR) acts as a critical switch that determines the tolerogenic function of cDC1s and the threshold of antigen-specific T cell responses. In total lymphoid irradiation-induced allograft tolerance9,10, cDC1s upregulate EPOR expression, and conditional knockout of EPOR in cDC1s diminishes antigen-specific induction and expansion of FOXP3+ regulatory T (Treg) cells, resulting in allograft rejection. Mechanistically, EPOR promotes efferocytosis-induced tolerogenic maturation7,11 of splenic cDC1s towards late-stage CCR7+ cDC1s characterized by increased expression of the integrin β8 gene12 (Itgb8), and conditional knockout of Itgb8 in cDC1s impairs tolerance induced by total lymphoid irradiation plus anti-thymocyte serum. Migratory cDC1s in peripheral lymph nodes preferentially express EPOR, and their FOXP3+ Treg cell-inducing capacity is enhanced by erythropoietin. Reciprocally, loss of EPOR enables immunogenic maturation of peripheral lymph node migratory and splenic CCR7+ cDC1s by upregulating genes involved in MHC class II- and class I-mediated antigen presentation, cross-presentation and costimulation. EPOR deficiency in cDC1s reduces tumour growth by enhancing anti-tumour T cell immunity, particularly increasing the generation of precursor exhausted tumour antigen-specific CD8+ T cells13 in tumour-draining lymph nodes and supporting their maintenance within tumours, while concurrently reducing intratumoural Treg cells. Targeting EPOR on cDC1s to induce or inhibit T cell immune tolerance could have potential for treating a variety of diseases.

Triple-negative breast cancer (TNBC) remains a lethal malignancy with limited targeted therapies and high metastatic rates. Cancer cells evade macrophage clearance by overexpressing anti-phagocytic cell surface proteins, termed "don't eat me" signals. Blocking antibodies (e.g., anti-CD47) against these signals show therapeutic promise in multiple cancers, yet variable responses and limited durability of efficacy to such agents imply additional unknown "don't eat me" signals exist. Here, we detected positive CD52 expression in tumors from TNBC patients and demonstrated that CD52 on TNBC cells facilitates immune evasion by engaging the inhibitory receptor sialic acid-binding Ig-like lectin G (Siglec-G) on tumor-associated macrophages. Genetic ablation of either CD52 or Siglec-G, as well as antibody-mediated blockade of their interaction restored macrophage phagocytic activity both in vitro and in vivo. This consequently suppressed tumor progression, improved survival, and promoted an immunologically active tumor microenvironment in TNBC mouse models. Additionally, cotreatment with anti-CD52 sensitized tumor cells to PD-1 blockade therapy in the spontaneous MMTV-PyMT TNBC model. Our findings identify CD52 as a prominently expressed anti-phagocytic checkpoint in TNBC and reveal the therapeutic potential of dual PD-1/CD52 blockade as a novel immunotherapeutic strategy.

Cancer immunotherapy is only effective in a subset of patients, highlighting the need for effective biomarkers and combination therapies. Here, we systematically identify genetic determinants of cancer cell sensitivity to anti-tumor immunity by performing whole-genome CRISPR-Cas9 knockout screens in autologous tumoroid-T cell co-cultures, isogenic cancer cell models deficient in interferon signaling, and in the context of four cytokines. We discover that loss of CHD1 and MAP3K7 (encoding TAK1) potentiates the transcriptional response to IFN-γ, thereby creating an acquired vulnerability by sensitizing cancer cells to tumor-reactive T cells. Immune checkpoint blockade is more effective in a syngeneic mouse model of melanoma deficient in Chd1 and Map3k7 and is associated with elevated intra-tumoral CD8+ T cell numbers and activation. CHD1 and MAP3K7 are recurrently mutated in cancer, and reduced expression in tumors correlates with response to immune checkpoint inhibitors in patients, nominating these genes as potential biomarkers of immunotherapy response.