SHP-2 and PD-1-SHP-2 signaling regulate myeloid cell differentiation and antitumor responses.

The inhibitory receptor PD-1 suppresses T cell activation by recruiting the phosphatase SHP-2. However, mice with a T-cell-specific deletion of SHP-2 do not have improved antitumor immunity. Here we showed that mice with conditional targeting of SHP-2 in myeloid cells, but not in T cells, had diminished tumor growth. RNA sequencing (RNA-seq) followed by gene set enrichment analysis indicated the presence of polymorphonuclear myeloid-derived suppressor cells and tumor-associated macrophages (TAMs) with enriched gene expression profiles of enhanced differentiation, activation and expression of immunostimulatory molecules. In mice with conditional targeting of PD-1 in myeloid cells, which also displayed diminished tumor growth, TAMs had gene expression profiles enriched for myeloid differentiation, activation and leukocyte-mediated immunity displaying >50% overlap with enriched profiles of SHP-2-deficient TAMs. In bone marrow, GM-CSF induced the phosphorylation of PD-1 and recruitment of PD-1-SHP-2 to the GM-CSF receptor. Deletion of SHP-2 or PD-1 enhanced GM-CSF-mediated phosphorylation of the transcription factors HOXA10 and IRF8, which regulate myeloid differentiation and monocytic-moDC lineage commitment, respectively. Thus, SHP-2 and PD-1-SHP-2 signaling restrained myelocyte differentiation resulting in a myeloid landscape that suppressed antitumor immunity.

Toward Optimal High Continuous Positive Airway Pressure as Postextubation Support in Preterm Neonates: A Retrospective Cohort Study.

OBJECTIVE: This study aimed to evaluate whether the initial pressure level on high continuous positive airway pressure (CPAP; ≥9 cm H2O), in relation to preextubation mean airway pressure (Paw), influences short-term clinical outcomes in preterm neonates. STUDY DESIGN: In this retrospective cohort study, preterm neonates <29 weeks' gestational age (GA) extubated from mean Paw ≥9 cm H2O and to high CPAP (≥9 cm H2O) were classified into "higher level CPAP" (2-3 cm H2O higher than preextubation Paw) and "equivalent CPAP" (-1 to +1 cm H2O in relation to preextubation Paw). Only the first eligible extubation per infant was analyzed. The primary outcome was failure within ≤7 days of extubation, defined as any one or more of (1) need for reintubation, (2) escalation to an alternate noninvasive respiratory support mode, or (3) use of CPAP >preextubation Paw + 3 cm H2O. Secondary outcomes included individual components of the primary outcome, along with other clinical and safety outcomes. RESULTS: Over a 10-year period (Jan 2011-Dec 2020), 175 infants were extubated from mean Paw >9 cm H2O to high CPAP pressures. Twenty-seven patients (median GA = 24.7, [interquartile range (IQR)]: (24.0-26.4) weeks and chronological age = 31, IQR: [21-40] days) were classified into the "higher level CPAP" group while 148 infants (median GA = 25.4, IQR: [24.6-26.6] weeks and chronological age = 26, IQR: [10-39] days) comprised the "equivalent CPAP" group. There was no difference in the primary outcome (44 vs. 51%; p = 0.51), including postadjustment for confounders (adjusted OR [aOR] = 0.47 [95% confidence interval (CI): 0.17-1.29; p = 0.14]). However, reintubation risk within 7 days was lower with higher level CPAP (7 vs. 37%; p < 0.01), including postadjustment (aOR = 0.07; 95% CI: 0.02-0.35; p < 0.01). CONCLUSION: In this cohort, use of initial distending CPAP pressures 2 to 3 cm H2O higher than preextubation Paw did not alter the primary outcome of failure but did lower the risk of reintubation. The latter is an interesting hypothesis-generating finding that requires further confirmation. KEY POINTS: · Use of high CPAP pressures (≥9 cm H2O) is gradually increasing in the care of preterm neonates.. · This study compares higher level versus equivalent CPAP in relation to preextubation Paw.. · The findings demonstrate no difference in failure as defined with use of higher level CPAP pressures..

The complex role of tumor-infiltrating macrophages.

Long recognized as an evolutionarily ancient cell type involved in tissue homeostasis and immune defense against pathogens, macrophages are being re-discovered as regulators of several diseases, including cancer. Tumor-associated macrophages (TAMs) represent the most abundant innate immune population in the tumor microenvironment (TME). Macrophages are professional phagocytic cells of the hematopoietic system specializing in the detection, phagocytosis and destruction of bacteria and other harmful micro-organisms, apoptotic cells and metabolic byproducts. In contrast to these healthy macrophage functions, TAMs support cancer cell growth and metastasis and mediate immunosuppressive effects on the adaptive immune cells of the TME. Cancer is one of the most potent insults on macrophage physiology, inducing changes that are intimately linked with disease progression. In this Review, we outline hallmarks of TAMs and discuss the emerging mechanisms that contribute to their pathophysiological adaptations and the vulnerabilities that provide attractive targets for therapeutic exploitation in cancer.

Single-cell RNA sequencing reveals evolution of immune landscape during glioblastoma progression.

Glioblastoma (GBM) is an incurable primary malignant brain cancer hallmarked with a substantial protumorigenic immune component. Knowledge of the GBM immune microenvironment during tumor evolution and standard of care treatments is limited. Using single-cell transcriptomics and flow cytometry, we unveiled large-scale comprehensive longitudinal changes in immune cell composition throughout tumor progression in an epidermal growth factor receptor-driven genetic mouse GBM model. We identified subsets of proinflammatory microglia in developing GBMs and anti-inflammatory macrophages and protumorigenic myeloid-derived suppressors cells in end-stage tumors, an evolution that parallels breakdown of the blood-brain barrier and extensive growth of epidermal growth factor receptor+ GBM cells. A similar relationship was found between microglia and macrophages in patient biopsies of low-grade glioma and GBM. Temozolomide decreased the accumulation of myeloid-derived suppressor cells, whereas concomitant temozolomide irradiation increased intratumoral GranzymeB+ CD8+T cells but also increased CD4+ regulatory T cells. These results provide a comprehensive and unbiased immune cellular landscape and its evolutionary changes during GBM progression.

Implications of metabolism-driven myeloid dysfunctions in cancer therapy.

Immune homeostasis is maintained by an adequate balance of myeloid and lymphoid responses. In chronic inflammatory states, including cancer, this balance is lost due to dramatic expansion of myeloid progenitors that fail to mature to functional inflammatory neutrophils, macrophages, and dendritic cells (DCs), thus giving rise to a decline in the antitumor effector lymphoid response. Cancer-related inflammation orchestrates the production of hematopoietic growth factors and cytokines that perpetuate recruitment and activation of myeloid precursors, resulting in unresolved and chronic inflammation. This pathologic inflammation creates profound alterations in the intrinsic cellular metabolism of the myeloid progenitor pool, which is amplified by competition for essential nutrients and by hypoxia-induced metabolic rewiring at the tumor site. Therefore, persistent myelopoiesis and metabolic dysfunctions contribute to the development of cancer, as well as to the severity of a broad range of diseases, including metabolic syndrome and autoimmune and infectious diseases. The aims of this review are to (1) define the metabolic networks implicated in aberrant myelopoiesis observed in cancer patients, (2) discuss the mechanisms underlying these clinical manifestations and the impact of metabolic perturbations on clinical outcomes, and (3) explore new biomarkers and therapeutic strategies to restore immunometabolism and differentiation of myeloid cells towards an effector phenotype to increase host antitumor immunity. We propose that the profound metabolic alterations and associated transcriptional changes triggered by chronic and overactivated immune responses in myeloid cells represent critical factors influencing the balance between therapeutic efficacy and immune-related adverse effects (irAEs) for current therapeutic strategies, including immune checkpoint inhibitor (ICI) therapy.

Publisher Correction: Phosphorylation of PD-1-Y248 is a marker of PD-1-mediated inhibitory function in human T cells.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Revisiting the PD-1 pathway.

Programmed Death-1 (PD-1; CD279) is an inhibitory receptor induced in activated T cells. PD-1 engagement by its ligands, PD-L1 and PD-L2, maintains peripheral tolerance but also compromises anti-tumor immunity. Blocking antibodies against PD-1 or its ligands have revolutionized cancer immunotherapy. However, only a fraction of patients develop durable antitumor responses. Clinical outcomes have reached a plateau without substantial advances by combinatorial approaches. Thus, great interest has recently emerged to investigate, in depth, the mechanisms by which the PD-1 pathway transmits inhibitory signals with the goal to identify molecular targets for improvement of the therapeutic success. These efforts have revealed unpredictable dimensions of the pathway and uncovered novel mechanisms involved in PD-1 and PD-L1 regulation and function. Here, we provide an overview of the recent advances on the mechanistic aspects of the PD-1 pathway and discuss the implications of these new discoveries and the gaps that remain to be filled.

Tumor-Derived Prostaglandin E2 Promotes p50 NF-κB-Dependent Differentiation of Monocytic MDSCs.

Myeloid-derived suppressor cells (MDSC) include immature monocytic (M-MDSC) and granulocytic (PMN-MDSC) cells that share the ability to suppress adaptive immunity and to hinder the effectiveness of anticancer treatments. Of note, in response to IFNγ, M-MDSCs release the tumor-promoting and immunosuppressive molecule nitric oxide (NO), whereas macrophages largely express antitumor properties. Investigating these opposing activities, we found that tumor-derived prostaglandin E2 (PGE2) induces nuclear accumulation of p50 NF-κB in M-MDSCs, diverting their response to IFNγ toward NO-mediated immunosuppression and reducing TNFα expression. At the genome level, p50 NF-κB promoted binding of STAT1 to regulatory regions of selected IFNγ-dependent genes, including inducible nitric oxide synthase (Nos2). In agreement, ablation of p50 as well as pharmacologic inhibition of either the PGE2 receptor EP2 or NO production reprogrammed M-MDSCs toward a NOS2low/TNFαhigh phenotype, restoring the in vivo antitumor activity of IFNγ. Our results indicate that inhibition of the PGE2/p50/NO axis prevents MDSC-suppressive functions and restores the efficacy of anticancer immunotherapy. SIGNIFICANCE: Tumor-derived PGE2-mediated induction of nuclear p50 NF-κB epigenetically reprograms the response of monocytic cells to IFNγ toward an immunosuppressive phenotype, thus retrieving the anticancer properties of IFNγ. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/80/13/2874/F1.large.jpg.

Targeted deletion of PD-1 in myeloid cells induces antitumor immunity.

PD-1, a T cell checkpoint receptor and target of cancer immunotherapy, is also expressed on myeloid cells. The role of myeloid-specific versus T cell-specific PD-1 ablation on antitumor immunity has remained unclear because most studies have used either PD-1-blocking antibodies or complete PD-1 KO mice. We generated a conditional allele, which allowed myeloid-specific (PD-1f/fLysMcre) or T cell-specific (PD-1f/fCD4cre) targeting of Pdcd1 gene. Compared with T cell-specific PD-1 ablation, myeloid cell-specific PD-1 ablation more effectively decreased tumor growth. We found that granulocyte/macrophage progenitors (GMPs), which accumulate during cancer-driven emergency myelopoiesis and give rise to myeloid-derived suppressor cells (MDSCs), express PD-1. In tumor-bearing PD-1f/fLysMcre but not PD-1f/fCD4cre mice, accumulation of GMP and MDSC was prevented, whereas systemic output of effector myeloid cells was increased. Myeloid cell-specific PD-1 ablation induced an increase of T effector memory cells with improved functionality and mediated antitumor protection despite preserved PD-1 expression in T cells. In PD-1-deficient myeloid progenitors, growth factors driving emergency myelopoiesis induced increased metabolic intermediates of glycolysis, pentose phosphate pathway, and TCA cycle but, most prominently, elevated cholesterol. Because cholesterol is required for differentiation of inflammatory macrophages and DC and promotes antigen-presenting function, our findings indicate that metabolic reprogramming of emergency myelopoiesis and differentiation of effector myeloid cells might be a key mechanism of antitumor immunity mediated by PD-1 blockade.

Phosphorylation of PD-1-Y248 is a marker of PD-1-mediated inhibitory function in human T cells.

PD-1 is a target of cancer immunotherapy but responses are limited to a fraction of patients. Identifying patients with T cells subjected to PD-1-mediated inhibition will allow selection of suitable candidates for PD-1-blocking therapy and will improve the therapeutic success. We sought to develop an approach to detect PD-1-mediated inhibitory signaling. The cytoplasmic tail of PD-1 contains an immunoreceptor tyrosine-based inhibitory motif (ITIM) encompassing Y223 and an immunoreceptor tyrosine-based switch motif (ITSM) encompassing Y248, which is indispensable for interaction of SHP-2 and delivery of PD-1 inhibitory function. We generated an antibody specific for phosphorylated PD-1-Y248 and examined PD-1pY248+ (pPD-1) expression in human T cells. pPD-1 was upregulated by TCR/CD3 + CD28 stimulation and simultaneous PD-1 ligation. pPD-1+CD8+ T cells were identified in human peripheral blood and had impaired effector function. pPD-1+ T cells were also detected in tumor-draining lymph nodes of tumor bearing mice and in biopsies of patients with glioblastoma multiform. Detection of pPD-1+ T cells might serve as a biomarker for identification of T cells subjected to PD-1-mediated immunosuppression.

Targeting T Cell Metabolism for Improvement of Cancer Immunotherapy.

There has been significant progress in utilizing our immune system against cancer, mainly by checkpoint blockade and T cell-mediated therapies. The field of cancer immunotherapy is growing rapidly but durable clinical benefits occur only in a small subset of responding patients. It is currently recognized that cancer creates a suppressive metabolic microenvironment, which contributes to ineffective immune function. Metabolism is a common cellular feature, and although there has been significant progress in understanding the detrimental role of metabolic changes of the tumor microenvironment (TEM) in immune cells, there is still much to be learned regarding unique targetable pathways. Elucidation of cancer and immune cell metabolic profiles is critical for identifying mechanisms that regulate metabolic reprogramming within the TEM. Metabolic targets that mediate immunosuppression and are fundamental in sustaining tumor growth can be exploited therapeutically for the development of approaches to increase the efficacy of immunotherapies. Here, we will highlight the importance of metabolism on the function of tumor-associated immune cells and will address the role of key metabolic determinants that might be targets of therapeutic intervention for improvement of tumor immunotherapies.

Publisher Correction: Feeling stressed? It might be your T cells.

In the version of this article initially published, the author surname citing the linked article (Miyama) was incorrect in the seventh and eighth paragraphs. The correct name is Miyajima.

The adaptor molecule RIAM integrates signaling events critical for integrin-mediated control of immune function and cancer progression.

Lymphocyte activation requires adhesion to antigen-presenting cells. This is a critical event linking innate and adaptive immunity. Lymphocyte adhesion is accomplished through LFA-1, which must be activated by a process referred to as inside-out integrin signaling. Among the few signaling molecules that have been implicated in inside-out integrin activation in hematopoietic cells are the small guanosine triphosphatase (GTPase) Rap1 and its downstream effector Rap1-interacting molecule (RIAM), a multidomain protein that defined the Mig10-RIAM-lamellipodin (MRL) class of adaptor molecules. Through its various domains, RIAM is a critical node of signal integration for activation of T cells, recruits monomeric and polymerized actin to drive actin remodeling and cytoskeletal reorganization, and promotes inside-out integrin signaling in T cells. As a regulator of inside-out integrin activation, RIAM affects multiple functions of innate and adaptive immunity. The effects of RIAM on cytoskeletal reorganization and integrin activation have implications in cell migration and trafficking of cancer cells. We provide an overview of the structure and interactions of RIAM, and we discuss the implications of RIAM functions in innate and adaptive immunity and cancer.

Metabolic regulation of suppressive myeloid cells in cancer.

Cancer cells rewire their metabolism to promote growth, survival, proliferation and long-term maintenance. The common feature of this altered metabolism is the increased glucose uptake and fermentation of glucose to lactate, which is observed even in the presence of completely functioning mitochondria. This effect is known as the 'Warburg Effect' and its intensive investigation in the last decade has partially established either its causes or its functions. It is now emerging that a major side effect of the Warburg Effect is immunosuppression, which limits the immunogenicity of cancer cells and therefore restricts the therapeutic efficacy of anticancer immunotherapy. Here we discuss how the metabolic communication between cancer and infiltrating myeloid cells contributes to cancer immune evasion and how the understanding of these mechanisms may improve current immunotherapies.

Immunometabolic Regulations Mediated by Coinhibitory Receptors and Their Impact on T Cell Immune Responses.

Host immunity provides wide spectrum protection that serves to eradicate pathogens and cancer cells, while maintaining self-tolerance and immunological homeostasis. Ligation of the T cell receptor (TCR) by antigen activates signaling pathways that coordinately induce aerobic glycolysis, mitochondrial activity, anabolic metabolism, and T effector cell differentiation. Activation of PI3K, Akt, and mTOR triggers the switch to anabolic metabolism by inducing transcription factors such as Myc and HIF1, and the glucose transporter Glut1, which is pivotal for the increase of glucose uptake after T cell activation. Activation of MAPK signaling is required for glucose and glutamine utilization, whereas activation of AMPK is critical for energy balance and metabolic fitness of T effector and memory cells. Coinhibitory receptors target TCR-proximal signaling and generation of second messengers. Imbalanced activation of such signaling pathways leads to diminished rates of aerobic glycolysis and impaired mitochondrial function resulting in defective anabolic metabolism and altered T cell differentiation. The coinhibitory receptors mediate distinct and synergistic effects on the activation of signaling pathways thereby modifying metabolic programs of activated T cells and resulting in altered immune functions. Understanding and therapeutic targeting of metabolic programs impacted by coinhibitory receptors might have significant clinical implications for the treatment of chronic infections, cancer, and autoimmune diseases.

Energy metabolism drives myeloid-derived suppressor cell differentiation and functions in pathology.

Over the last decade, a heterogeneous population of immature myeloid cells with major regulatory functions has been described in cancer and other pathologic conditions and ultimately defined as MDSCs. Most of the early work on the origins and functions of MDSCs has been in murine and human tumor bearers in which MDSCs are known to be immunosuppressive and to result in both reduced immune surveillance and antitumor cytotoxicity. More recent studies, however, suggest that expansion of these immature myeloid cells may be linked to most, if not all, chronic and acute inflammatory processes. The universal expansion to inflammatory stimuli of MDSCs suggests that these cells may be more of a normal component of the inflammatory response (emergency myelopoiesis) than simply a pathologic response to a growing tumor. Instead of an adverse immunosuppressive response, expansion of these immature myeloid cell populations may result from a complex balance between increased immune surveillance and dampened adaptive immune responses that are common to many inflammatory responses. Within this scenario, new pathways of metabolic reprogramming are emerging as drivers of MDSC differentiation and functions in cancer and inflammatory disorders, crucially linking metabolic syndrome to inflammatory processes.

Protocol for a prospective, controlled, observational study to evaluate the influence of hypoxia on healthy volunteers and patients with inflammatory bowel disease: the Altitude IBD Study.

INTRODUCTION: Inflammatory bowel disease (IBD) is a chronic intestinal disorder, often leading to an impaired quality of life in affected patients. The importance of environmental factors in the pathogenesis of IBD, including their disease-modifying potential, is increasingly recognised. Hypoxia seems to be an important driver of inflammation, as has been reported by our group and others. The aim of the study is to evaluate if hypoxia can alter disease activity of IBD measured by Harvey-Bradshaw Activity Index in Crohn's disease (increase to ≥5 points) and the partial Mayo Score for ulcerative colitis (increase to ≥2 points). To test the effects of hypoxia under standardised conditions, we designed a prospective and controlled investigation in healthy controls and patients with IBD in stable remission. METHODS AND ANALYSIS: This is a prospective, controlled and observational study. Participants undergo a 3-hour exposure to hypoxic conditions simulating an altitude of 4000 metres above sea level (m.a.s.l.) in a hypobaric pressure chamber. Clinical parameters, as well as blood and stool samples and biopsies from the sigmoid colon are collected at subsequent time points. ETHICS AND DISSEMINATION: The study protocol was approved by the Ethics Committee of the Kanton Zurich (reference KEK-ZH-number 2013-0284). The results will be published in a peer-reviewed journal and shared with the worldwide medical community. TRIALS REGISTRATION NUMBER: NCT02849821; Pre-results.

RORC1 Regulates Tumor-Promoting "Emergency" Granulo-Monocytopoiesis.

Cancer-driven granulo-monocytopoiesis stimulates expansion of tumor promoting myeloid populations, mostly myeloid-derived suppressor cells (MDSCs) and tumor-associated macrophages (TAMs). We identified subsets of MDSCs and TAMs based on the expression of retinoic-acid-related orphan receptor (RORC1/RORγ) in human and mouse tumor bearers. RORC1 orchestrates myelopoiesis by suppressing negative (Socs3 and Bcl3) and promoting positive (C/EBPß) regulators of granulopoiesis, as well as the key transcriptional mediators of myeloid progenitor commitment and differentiation to the monocytic/macrophage lineage (IRF8 and PU.1). RORC1 supported tumor-promoting innate immunity by protecting MDSCs from apoptosis, mediating TAM differentiation and M2 polarization, and limiting tumor infiltration by mature neutrophils. Accordingly, ablation of RORC1 in the hematopoietic compartment prevented cancer-driven myelopoiesis, resulting in inhibition of tumor growth and metastasis.

Neutralization of colony-stimulating factor 1 receptor prevents sickness behavior syndrome by reprogramming inflammatory monocytes to produce IL-10.

Sickness behavior syndrome (SBS) as characterized by fatigue and depression impairs quality of life in patients with inflammatory diseases caused by infections and autoimmunity. Systemic engagement of CD40 in mice leads to an inflammatory syndrome with acute hepatitis, lymphadenopathy and development of SBS as evidenced by induction of sleep and weight loss. In the study presented here we show that the elimination of resident tissue macrophages in mice by antibody-mediated neutralization of colony-stimulating factor-1 receptor (CSF1R) did not prevent CD40 induced hepatitis, but conferred resistance to the development of SBS. The protective effect of CSF1R mAb on weight loss and behavior changes induced by CD40 activation coincided with the transformation of pro-inflammatory monocytes to IL-10 producing myeloid cells. In IL-10 knockout mice CSF1R neutralization failed to exert protection from the occurrence of SBS. This study establishes the unexpected key role of CSF1R in the polarization of inflammatory monocytes and thereby SBS in inflammatory liver diseases.