Dietary Lactobacillus-Derived Exopolysaccharide Enhances Immune-Checkpoint Blockade Therapy.

Microbes and their byproducts have been reported to regulate host health and immune functions. Here we demonstrated that microbial exopolysaccharide produced by Lactobacillus delbrueckii subsp. bulgaricus OLL1073R-1 (EPS-R1) induced CCR6+ CD8+ T cells of mice and humans. In mice, ingestion of EPS-R1 augmented antitumor effects of anti-CTLA-4 or anti-PD-1 monoclonal antibody against CCL20-expressing tumors, in which infiltrating CCR6+ CD8+ T cells were increased and produced IFNγ accompanied by a substantial immune response gene expression signature maintaining T-cell functions. Of note, the antitumor adjuvant effect of EPS-R1 was also observed in germ-free mice. Furthermore, the induction of CCR6 expression was mediated through the phosphorylated structure in EPS-R1 and a lysophosphatidic acid receptor on CD8+ T cells. Overall, we find that dietary EPS-R1 consumption induces CCR6+ CD8+ T cells in Peyer's patches, favoring a tumor microenvironment that augments the therapeutic effect of immune-checkpoint blockade depending on CCL20 production by tumors. SIGNIFICANCE: Gut microbiota- and probiotic-derived metabolites are attractive agents to augment the efficacy of immunotherapies. Here we demonstrated that dietary consumption of Lactobacillus-derived exopolysaccharide induced CCR6+ CD8+ T cells in Peyer's patches and improved the tumor microenvironment to augment the therapeutic effects of immune-checkpoint blockade against CCL20-producing tumors. See related commentary by Di Luccia and Colonna, p. 1189. This article is highlighted in the In This Issue feature, p. 1171.

NKG7 Is Required for Optimal Antitumor T-cell Immunity.

Tumor antigen-specific CD8+ T cells play a critical role in antitumor immunity. Clinical trials reinvigorating the immune system via immune checkpoint blockade (ICB) have shown remarkable clinical promise. Numerous studies have identified an association between NKG7 expression and patient outcome across different malignancies. However, aside from these correlative observations, very little is known about NKG7 and its role in antitumor immunity. Herein, we utilized single-cell RNA sequencing (scRNA-seq) datasets, NKG7-deficient mice, NKG7-reporter mice, and mouse tumor models to investigate the role of NKG7 in neoantigen-mediated tumor rejection and ICB immunotherapy. scRNA-seq of tumors from patients with metastatic melanoma or head and neck squamous cell carcinoma revealed that NKG7 expression is highly associated with cytotoxicity and specifically expressed by CD8+ T cells and natural killer (NK) cells. Furthermore, we identified a key role for NKG7 in controlling intratumor T-cell accumulation and activation. NKG7 was upregulated on intratumor antigen-specific CD8+ T cells and NK cells and required for the accumulation of T cells in the tumor microenvironment. Accordingly, neoantigen-expressing mouse tumors grew faster in Nkg7-deficient mice. Strikingly, efficacy of single or combination ICB was significantly reduced in Nkg7-deficient mice.See related article by Wen et al., p. 162.

ATP and cancer immunosurveillance.

While intracellular adenosine triphosphate (ATP) occupies a key position in the bioenergetic metabolism of all the cellular compartments that form the tumor microenvironment (TME), extracellular ATP operates as a potent signal transducer. The net effects of purinergic signaling on the biology of the TME depend not only on the specific receptors and cell types involved, but also on the activation status of cis- and trans-regulatory circuitries. As an additional layer of complexity, extracellular ATP is rapidly catabolized by ectonucleotidases, culminating in the accumulation of metabolites that mediate distinct biological effects. Here, we discuss the molecular and cellular mechanisms through which ATP and its degradation products influence cancer immunosurveillance, with a focus on therapeutically targetable circuitries.

BET inhibition blocks inflammation-induced cardiac dysfunction and SARS-CoV-2 infection.

Cardiac injury and dysfunction occur in COVID-19 patients and increase the risk of mortality. Causes are ill defined but could be through direct cardiac infection and/or inflammation-induced dysfunction. To identify mechanisms and cardio-protective drugs, we use a state-of-the-art pipeline combining human cardiac organoids with phosphoproteomics and single nuclei RNA sequencing. We identify an inflammatory "cytokine-storm", a cocktail of interferon gamma, interleukin 1ß, and poly(I:C), induced diastolic dysfunction. Bromodomain-containing protein 4 is activated along with a viral response that is consistent in both human cardiac organoids (hCOs) and hearts of SARS-CoV-2-infected K18-hACE2 mice. Bromodomain and extraterminal family inhibitors (BETi) recover dysfunction in hCOs and completely prevent cardiac dysfunction and death in a mouse cytokine-storm model. Additionally, BETi decreases transcription of genes in the viral response, decreases ACE2 expression, and reduces SARS-CoV-2 infection of cardiomyocytes. Together, BETi, including the Food and Drug Administration (FDA) breakthrough designated drug, apabetalone, are promising candidates to prevent COVID-19 mediated cardiac damage.

Innate myeloid cells in the tumor microenvironment.

Cancer immunotherapies are receiving increasing approval in the clinic, but still only a fraction of patients benefit long-term. Understanding the most important mechanisms of immunotherapeutic resistance is critical for broader utility and benefit of cancer immunotherapy. While the tumor microenvironment (TME) is made up of many cell types, immunosuppressive monocytes/macrophages, granulocytes and myeloid derived suppressor cells interact with, and play a critical role in regulating the anti-tumor lymphocyte effector cells that mediate effective immunotherapies. Herein, we discuss the latest research that has identified and compared the importance of pro-tumor and immunosuppressive mechanisms that tumor infiltrating myeloid cells employ. Exploiting this new information may help to develop totally novel therapies to boost contemporary cancer immunotherapy.

Systemic administration of IL-33 induces a population of circulating KLRG1hi type 2 innate lymphoid cells and inhibits type 1 innate immunity against multiple myeloma.

Type 2 innate lymphoid cells (ILC2s) are important producers of type 2 cytokines whose role in hematological cancers remains unclear. ILC2s are a heterogeneous population encompassing distinct subsets with different tissue localization and cytokine responsiveness. In this study, we investigated the role of bone marrow (BM) ILC2s and interleukin (IL)-33-stimulated ILC2s in multiple myeloma, a plasma cell malignancy that develops in the BM. We found that myeloma growth was associated with phenotypic and functional alterations of BM ILC2s, characterized by an increased expression of maturation markers and reduced cytokine response to IL-2/IL-33. We identified a population of KLRG1hi ILC2s that preferentially accumulated in the liver and spleen of Il2rg-/- Rag2-/- mice reconstituted with BM ILC2s. A similar population of KLRG1hi ILC2s was observed in the blood, liver and spleen of IL-33-treated wild-type mice. The presence of KLRG1hi ILC2s in ILC2-reconstituted Il2rg-/- Rag2-/- mice or in IL-33-treated wild-type mice was associated with increased eosinophil numbers but had no effect on myeloma progression. Interestingly, while decreased myeloma growth was observed following treatment of Rag-deficient mice with the type 1 cytokines IL-12 and IL-18, this protection was reversed when mice received a combined treatment of IL-33 together with IL-12 and IL-18. In summary, our data indicate that IL-33 treatment induces a population of circulating inflammatory KLRG1hi ILC2s and inhibits type 1 immunity against multiple myeloma. These results argue against therapeutic administration of IL-33 to myeloma patients.

Concomitant or delayed anti-TNF differentially impact on immune-related adverse events and antitumor efficacy after anti-CD40 therapy.

BACKGROUND: Concomitant tumor necrosis factor (TNF) neutralization in combination with immune checkpoint inhibitors (ICIs) reduces clinical immune-related adverse events (irAEs) and appears to improve antitumor efficacy in preclinical tumor models. Agonistic antibodies targeting costimulatory receptors such as CD40 represent an additional strategy to boost antitumor immune response and potentiate the activity of ICIs. However, the dose-limiting toxicities observed in anti-CD40-treated cancer patients have hindered its clinical development. METHODS: We previously described a mouse model to assess both antitumor activity and irAEs induced by various effective combination immunotherapies. Using the BALB/c and C57BL/6 strains of FoxP3-GFP-DTR (FoxP3DTR) mice, transient depletion of T regulatory cells (Tregs) prior to immunotherapy with additional immunomodulatory antibodies, lowered immune self-tolerance, resulting in the development of a spectrum of physical and biochemical irAEs similar to that reported clinically. In MC38 and 4T1.2 tumor models, following transient Treg depletion, we evaluated the impact of anti-CD40 on antitumor efficacy and the development of irAEs and the impact of concomitant or delayed TNF blockade on both these parameters. Physical irAEs were scored and biochemical irAEs were measured in the serum (ALT and cytokine levels). Histopathological liver and colon tissue analysis were performed to assess immune cell infiltration and tissue damage. RESULTS: Similar to early clinical trials of CD40 agonists, in our tumor models we observed liver toxicities and rapid release of proinflammatory cytokines (TNF, interleukin 6, interferon-γ). In the BALB/c strain, anti-CD40 induced severe physical and biochemical irAEs. Concomitant anti-TNF treatment abrogated weight loss, liver damage and colitis, which consequently resulted in an improved clinical score. However, concomitant anti-TNF impaired antitumor response in a proportion of anti-CD40-treated C57BL/6 FoxP3DTR mice. Delaying TNF blockade in these mice reduced biochemical but not physical irAEs while preserving antitumor efficacy. CONCLUSIONS: Our results suggest concomitant rather than delayed anti-TNF is most effective in reducing biochemical and physical irAEs induced by anti-CD40, although it had the potential to negatively impact antitumor efficacy. Furthermore, our findings highlight the utility of our mouse model to assess the severity of irAEs induced by novel immunotherapeutic agents and evaluate whether their toxicity and antitumor efficacy can be uncoupled.

CD155 on Tumor Cells Drives Resistance to Immunotherapy by Inducing the Degradation of the Activating Receptor CD226 in CD8+ T Cells.

The activating receptor CD226 is expressed on lymphocytes, monocytes, and platelets and promotes anti-tumor immunity in pre-clinical models. Here, we examined the role of CD226 in the function of tumor-infiltrating lymphocytes (TILs) and resistance to immunotherapy. In murine tumors, a large proportion of CD8+ TILs had decreased surface expression of CD226 and exhibited features of dysfunction, whereas CD226hi TILs were highly functional. This correlation was seen also in TILs isolated from HNSCC patients. Mutation of CD226 at tyrosine 319 (Y319) led to increased CD226 surface expression, enhanced anti-tumor immunity and improved efficacy of immune checkpoint blockade (ICB). Mechanistically, tumor-derived CD155, the ligand for CD226, initiated phosphorylation of Y319 by Src kinases, thereby enabling ubiquitination of CD226 by CBL-B, internalization, and proteasomal degradation. In pre-treatment samples from melanoma patients, CD226+CD8+ T cells correlated with improved progression-free survival following ICB. Our findings argue for the development of therapies aimed at maintaining the expression of CD226.

Eomes-Dependent Loss of the Co-activating Receptor CD226 Restrains CD8+ T Cell Anti-tumor Functions and Limits the Efficacy of Cancer Immunotherapy.

CD8+ T cells within the tumor microenvironment (TME) are exposed to various signals that ultimately determine functional outcomes. Here, we examined the role of the co-activating receptor CD226 (DNAM-1) in CD8+ T cell function. The absence of CD226 expression identified a subset of dysfunctional CD8+ T cells present in peripheral blood of healthy individuals. These cells exhibited reduced LFA-1 activation, altered TCR signaling, and a distinct transcriptomic program upon stimulation. CD226neg CD8+ T cells accumulated in human and mouse tumors of diverse origin through an antigen-specific mechanism involving the transcriptional regulator Eomesodermin (Eomes). Despite similar expression of co-inhibitory receptors, CD8+ tumor-infiltrating lymphocyte failed to respond to anti-PD-1 in the absence of CD226. Immune checkpoint blockade efficacy was hampered in Cd226-/- mice. Anti-CD137 (4-1BB) agonists also stimulated Eomes-dependent CD226 loss that limited the anti-tumor efficacy of this treatment. Thus, CD226 loss restrains CD8+ T cell function and limits the efficacy of cancer immunotherapy.

Correction to: YTHDF2 reduction fuels inflammation and vascular abnormalization in hepatocellular carcinoma.

An amendment to this paper has been published and can be accessed via the original article.

The NK cell granule protein NKG7 regulates cytotoxic granule exocytosis and inflammation.

Immune-modulating therapies have revolutionized the treatment of chronic diseases, particularly cancer. However, their success is restricted and there is a need to identify new therapeutic targets. Here, we show that natural killer cell granule protein 7 (NKG7) is a regulator of lymphocyte granule exocytosis and downstream inflammation in a broad range of diseases. NKG7 expressed by CD4+ and CD8+ T cells played key roles in promoting inflammation during visceral leishmaniasis and malaria-two important parasitic diseases. Additionally, NKG7 expressed by natural killer cells was critical for controlling cancer initiation, growth and metastasis. NKG7 function in natural killer and CD8+ T cells was linked with their ability to regulate the translocation of CD107a to the cell surface and kill cellular targets, while NKG7 also had a major impact on CD4+ T cell activation following infection. Thus, we report a novel therapeutic target expressed on a range of immune cells with functions in different immune responses.