Expression Of Inhibitory Receptors Research Articles

BET inhibition sensitizes innate checkpoint inhibitor resistant melanoma to anti-CTLA-4 treatment.

Approximately 50% of melanoma patients fail to respond to immune checkpoint blockade (ICB), and acquired resistance hampers long-term survival in about half of initially responding patients. Whether targeting BET reader proteins, implicated in epigenetic dysregulation, can enhance ICB response rates and durability, remains to be determined. Here we show elevated BET proteins correlate with poor survival and ICB responses in melanoma patients. The BET inhibitor IBET151, combined with anti-CTLA-4, overcame innate ICB resistance however, sequential BET inhibition failed against acquired resistance in mouse models. Combination treatment response in the innate resistance model induced changes in tumor-infiltrating immune cells, reducing myeloid-derived suppressor cells (MDSCs). CD4+ and CD8+ T cells showed decreased expression of inhibitory receptors, with reduced TIM3, LAG3, and BTLA checkpoint expression. In human PBMCs invitro, BET inhibition reduced expression of immune checkpoints in CD4+ and CD8+ T cells, restoring effector cytokines and downregulating the transcriptional driver TOX. BET proteins in melanoma may play an oncogenic role by inducing immune suppression and driving T cell dysfunction. The study demonstrates an effective combination for innately unresponsive melanoma patients to checkpoint inhibitor immunotherapy, yet highlights BET inhibitors' limitations in an acquired resistance context.

Natural killer cells display unique, non-cytotoxic profiles in human endometrial cancer

Abstract Endometrial cancer (EC) responds variably to immune checkpoint blockade, warranting study of the tumor microenvironment (TME). Natural killer (NK) cells are cytotoxic innate lymphocytes that can directly kill tumor cells, yet their diversity, locations, and functions in the EC TME are unknown. CITE-seq analysis of fresh EC tumor samples revealed multiple NK cell populations in the TME, with distinct patterns of surface activating and inhibitory receptor expression and less cytolytic granule expression by tumor-derived conventional NK (cNK) and tissue-resident NK (trNK) cells compared to autologous blood cNK. Ex vivo flow cytometry revealed significantly lower expression of cytolytic granules by TME-derived NK cell subsets (granzyme B MFI: blood cNK 1.5e5 +/- 5.4e4, tumor cNK 7.9e4 +/- 2.9e4 p<0.05, tumor trNK 3.7e4 +/- 1.4e4 p<0.05, n=10; perforin MFI: blood cNK 1.3e4 +/- 3.1e3, tumor cNK 1.0e4 +/- 3.2e3 p=0.19, tumor trNK 3.5e3 +/-1.3e3 p<0.01, n=8). To identify NK cell subsets within the TME, we performed immunohistochemistry using CD3, CD56, granzyme B, and CD103 to demarcate cNK and trNK, respectively. We observed granzyme B+ cells primarily in the stroma (78.6 +/- 3.7% Stroma, 21.4 +/- 3.7% Glands, n=10, p<0.05) and CD103+ cells primarily among tumor cells (15.6 +/- 4.5% Stroma, 84.3 +/- 0.64% Glands, n=10, p=0.07). These data suggest that both cNK and trNK cell cytotoxicity is suppressed in the EC TME and ongoing work seeks to elucidate the mechanisms.

Crispr-Cas9 screen identifies potential novel regulators of CD8+ T cell dysfunction.

Abstract CD8+ T cells directly target and kill cancer cells and are required for effective antitumor immunity. However, CD8+ T cells may become dysfunctional when exposed to chronic antigen stimulation during cancer. Dysfunction is characterized by reduced proliferation, increased expression of inhibitory receptors, and impaired effector function, yet the genetic mechanisms controlling dysfunction remain poorly understood. To address this gap, we have developed an ex vivo restimulation model that recapitulates features of CD8+ T cell dysfunction seen within the tumor microenvironment. By coupling this system with genome-wide CRISPR-Cas9 loss of function screening, we have identified eIF4G2, a non-canonical protein translation factor, which may play a novel role in the progression of CD8+ T cells to a dysfunctional state. Deletion of eIF4G2 restored CD8+ T cell survival and proliferation during chronic restimulation conditions in vitro. Transcriptomic and flow cytometric analyses revealed that eIF4G2 controls expression of genes contributing to oxidative stress and a dysfunctional phenotype in vitro. Future studies will focus on characterizing the mechanistic and functional roles of this protein translation factor in vivo, as well as translating this model to primary human CD8+ T cells. In summary, we have uncovered eIF4G2 as a novel potential regulator of CD8+ T cell dysfunction and targeting eIF4G2 may improve antitumor immunity and immunotherapy efficacy.

Antigen-Specific Germinal Center Tfh cells are highly heterogenous in lymph nodes and Tfh1/Tfh17 cells are associated with viral load levels during chronic SHIV infection

Abstract HIV infection leads to alterations in HIV-specific CD4 T cells including increased expression of inhibitory receptors and skewing toward Tfh cell signature. Tfh cells have been shown to increase during chronic HIV infection. However, the heterogeneous nature of antigen-specific GC-Tfh cells and the relative contribution of specific GC-Tfh subset to viral persistence is not understood in HIV/SIV infection. Here, we characterized the phenotype and function of antigen-specific GC-Tfh cells based on the expression of chemokine receptors, Th1 (CXCR3), Th2 (CCR4), and Th17 (CCR6) along with activation-induced markers (AIM assay) CD25, OX40 and 41BB in the lymph nodes following chronic SHIV1157ipd3N4 infection in rhesus macaques. In SHIV naïve RM, only a small fraction of total GC-Tfh expressed CXCR3, CCR4, and CCR6. During chronic SHIV infection, there was an increase in GC-Tfh cells. Interestingly the majority of antigen-specific GC-Tfh cells expressed CXCR3 (Tfh1), while a significant proportion of them also expressed CCR4+ (Tfh2) and CCR6+ (Tfh17) cells. These cells expressed OX40, 41BB, and CD25 at higher levels than non-Tfh cells. Importantly, the expansion of GC-Tfh1 and GC-Tfh-17 cells is associated with high viremia. These data demonstrate that chronic SHIV infection promotes the expansion of antigen-specific GC-Tfh cells with heterogeneous populations, which are distinct from conventional GC-Tfh, and associated with higher viral RNA levels during chronic SHIV infection.

Deciphering the role of Klf2 in CD8 T cell differentiation and exhaustion during chronic infection

Abstract T cell exhaustion, a state of dysfunction occurring during chronic infections and cancer, is marked by a progressive loss of effector functions and increased expression of inhibitory receptors. In chronic infection, CD8 T cells differentiate into TCF1+ progenitor (TPRO), CX3CR1+ effector (TEFF), and terminally exhausted (TEXH) subsets. The differentiation pathways are governed by complex transcription factor (TF) networks. Employing regulon analysis enabled by single-cell RNA+ATAC multiome sequencing, we dissected the TF networks orchestrating the fate of exhausted CD8 T cell populations. Our integrative analysis, complemented by single-cell CRISPR screening, highlighted Krüppel-like factor 2 (KLF2) as a pivotal TF necessary for maintaining TPRO cells and generating TEFF cells. Our research also revealed that KLF2 regulates the distinct distribution patterns of CD8 T cell subsets across organs. More intriguingly, multiomic analysis uncovered a novel function of Klf2 in limiting T cell exhaustion. Klf2-deficient CD8 T cells exhibited a marked increase in exhaustion signature genes. ATAC-seq and CUT&TAG assays further revealed different chromatin accessibility and histone modifications within Klf2 and its enhancers across CD8 T cell subsets. These insights underscore the differential transcriptional and epigenetic regulation of Klf2, presenting a novel mechanism that influences the cell fate decision of CD8 T cells during chronic infections.

T-Cell Characteristics Impact Response and Resistance to T-Cell-Redirecting Bispecific Antibodies in Multiple Myeloma.

Bispecific antibodies (BsAb) directed against B-cell maturation antigen (teclistamab) or the orphan G protein-coupled receptor GPRC5D (talquetamab) induce deep and durable responses in heavily pretreated patients with multiple myeloma. However, mechanisms underlying primary and acquired resistance remain poorly understood. The anti-multiple myeloma activity of teclistamab and talquetamab was evaluated in bone marrow (BM) samples from patients with multiple myeloma. T-cell phenotype and function were assessed in BM/peripheral blood samples obtained from patients with multiple myeloma who were treated with these BsAb. In ex vivo killing assays with 41 BM samples from BsAb-naive patients with multiple myeloma, teclistamab- and talquetamab-mediated multiple myeloma lysis was strongly correlated (r = 0.73, P < 0.0001). Both BsAb exhibited poor activity in samples with high regulatory T-cell (Treg) numbers and a low T-cell/multiple myeloma cell ratio. Furthermore, comprehensive phenotyping of BM samples derived from patients treated with teclistamab or talquetamab revealed that high frequencies of PD-1+ CD4+ T cells, CTLA4+ CD4+ T cells, and CD38+ CD4+ T cells were associated with primary resistance. Although this lack of response was linked to a modest increase in the expression of inhibitory receptors, increasing T-cell/multiple myeloma cell ratios by adding extra T cells enhanced sensitivity to BsAb. Further, treatment with BsAb resulted in an increased proportion of T cells expressing exhaustion markers (PD-1, TIGIT, and TIM-3), which was accompanied by reduced T-cell proliferative potential and cytokine secretion, as well as impaired antitumor efficacy in ex vivo experiments. Primary resistance is characterized by a low T-cell/multiple myeloma cell ratio and Treg-driven immunosuppression, whereas reduced T-cell fitness due to continuous BsAb-mediated T-cell activation may contribute to the development of acquired resistance.

PD1 blockade improves survival and CD8+ cytotoxic capacity, without increasing inflammation, during normal microbial experience in old mice.

By 2030, individuals 65 years of age or older will make up approximately 20% of the world's population1. Older individuals are at the highest risk for mortality from infections, largely due to the pro-inflammatory, dysfunctional immune response, which is collectively known as immunosenescence2. During aging, CD8+ T cells acquire an exhausted phenotype, including increased expression of inhibitory receptors, such as programmed cell death 1 (PD1), a decline in effector function and elevated expression of inflammatory factors3-7. PD1 reduces T cell receptor activity via SHP2-dependent dephosphorylation of multiple pathways; accordingly, inhibiting PD1 activity through monoclonal antibodies increases CD8+ T cell effector response in young mice8-11. Attempts to improve CD8+ T cell responses by blocking inhibitory receptors are attractive; however, they can lead to adverse immune events due to overamplification of T cell receptor signaling and T cell activation12,13. Here we investigated the effect of monoclonal anti-PD1 immunotherapy during normal microbial experience, otherwise known as exposure to dirty mice, to determine whether it either improves exhausted CD8+ T cell responses in old mice or leads to a heightened inflammatory response and increased mortality.

Peripheral-central network analysis of cancer cachexia status accompanied by the polarization of hypothalamic microglia with low expression of inhibitory immune checkpoint receptors

While the excessive inflammation in cancer cachexia is well-known to be induced by the overproduction of inflammatory mediators in the periphery, microflora disruption and brain dysfunction are also considered to contribute to the induction of cancer cachexia. Hypothalamic microglia play a crucial role in brain inflammation and central-peripheral immune circuits via the production of inflammatory mediators. In the present study, we evaluated possible changes in excessive secretion of gut microbiota-derived endotoxin and the expression timeline of several inflammation-regulatory mediators and their inhibiting modulators in hypothalamic microglia of a mouse model of cancer cachexia following transplantation of pancreatic cancer cells. We demonstrated that the plasma level of lipopolysaccharide (LPS) was significantly increased with an increase in anaerobic bacteria, especially Firmicutes, in the gut at the late stage of tumor-bearing mice that exhibited dramatic appetite loss, sarcopenia and severe peripheral immune suppression. At the early stage, in which tumor-bearing mice had not yet displayed “cachexia symptoms”, the mRNA expression of pro-inflammatory cytokines, but not of the neurodegenerative and severe inflammatory modulator lipocalin-2 (LCN2), was significantly increased, whereas at the late “cachexia stage”, the level of LCN2 mRNA was significantly increased along with significant decreases in levels of inhibitory immune checkpoint receptors programmed death receptor-1 (PD-1) and CD112R in hypothalamic microglia. In addition, a high density of activated neurons in the paraventricular nucleus (PVN) of the hypothalamus region and a significant increase in corticosterone secretion were found in cachexia model mice. Related to the cachexia state, released corticosterone was clearly increased in normal mice with specific activation of PVN neurons. A marked decrease in the natural killer cell population was also observed in the spleen of mice with robust activation of PVN neurons as well as mice with cancer cachexia. On the other hand, in vivo administration of LPS in normal mice induced hypothalamic microglia with low expression of inhibitory immune checkpoint receptors. These findings suggest that the induction of cancer cachexia may parallel exacerbation of the hypothalamic inflammatory status with polarization to microglia expressed with low levels of inhibitory immune checkpoint receptors following LPS release from the gut microflora.

Abstract LB068: Repurposing chimeric antigen receptor regulatory T cells for treating cancer

Abstract Solid tumors are the deadliest form of cancer. Over the past decade, chimeric antigen receptor (CAR) T-cell therapy has led to remarkable regression rates in leukemia and lymphoma. However, solid tumors have remained refractory to CAR T-cell therapy, with CAR T cells either failing to penetrate the solid tumor microenvironment (TME) or becoming exhausted once in it. Mechanisms behind these properties of the TME include nutrient scarcity, aberrant vascularization, stromal cell deposition, expression of inhibitory immune receptors by cancer cells, and the presence of immunosuppressive cells. Interestingly, there is a subset of T cells found in the TME - regulatory T cells (Tregs). Dedicated to suppressing immune responses, Tregs constitute a barrier to anticancer immunity by migrating to and heavily accumulating in solid tumors, inhibiting local immunity. Tregs can be redirected towards any cell surface antigen using a CAR and have been shown to be cytotoxic towards target antigen presenting cells. Can Tregs be converted from tumor protectors to anti-tumor effector cells? To test the anti-tumor potential of CAR Tregs, we modified human Tregs with an anti-CD19 CD28-CD3z CAR. Tregs activated via the CAR or endogenous TCR/CD28 were evaluated at the functional and gene expression levels. CAR and endogenous TCR/CD28 activation resulted in similar cell expansion and Treg stability (FOXP3 and HELIOS expression). However, CAR-mediated activation markedly increased Treg proinflammatory cytokine production. Moreover, compared to their TCR/CD28-activated counterparts, CAR Tregs displayed increased cytotoxic activity towards tumor cells and a diminished capacity to modulate antigen-presenting cells and suppress T cell proliferation, suggesting a global shift from suppression to inflammation. Strikingly, CAR Tregs suppressed tumor growth in immunodeficient mice inoculated with antigen-expressing B-cell leukemia, myeloid leukemia, and lung epithelial carcinoma. Single-cell RNA sequencing identified a cell cluster enriched in CAR Tregs characterized by high expression of effector T cell genes, such as IFNG, GZMB, and CD40LG, revealing that CAR activation creates a highly active population of proinflammatory Tregs. Multiplex cytokine analysis, whole-transcriptome RNA-seq, and intracellular cytokine staining confirmed that IFNG production by FOXP3+ Tregs is induced specifically by CAR activation. Of note, murine CAR Tregs are also cytotoxic towards tumor cells. Current experiments are focused on pinpointing and validating transcription factors and surface markers characteristic of proinflammatory CAR Tregs and further assessing CAR Treg antitumor efficacy in vivo. In conclusion, CAR-mediated activation induces a novel proinflammatory Treg phenotype that can be exploited in the next generation of engineered immune cell therapies against solid tumors. Citation Format: Leonardo M. Ferreira, Russell W. Cochrane, Rob A. Robino, Bryan Granger, Eva Allen, Vishnu Gudivada, Aguirre A. de Cubas, Stefano Berto. Repurposing chimeric antigen receptor regulatory T cells for treating cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB068.

Chronic viral infection impairs immune memory to a different pathogen.

Chronic viral infections cause T cell dysfunction in both animal models and human clinical settings, thereby affecting the ability of the host immune system to clear viral pathogens and develop proper virus-specific immune memory. However, the impact of chronic viral infections on the host's immune memory to other pathogens has not been well described. In this study, we immunized mice with recombinant Listeria monocytogenes expressing OVA (Lm-OVA) to generate immunity to Lm and allow analysis of OVA-specific memory T (Tm) cells. We then infected these mice with lymphocytic choriomeningitis virus (LCMV) strain Cl-13 which establishes a chronic infection. We found that chronically infected mice were unable to protect against Listeria re-challenge. OVA-specific Tm cells showed a progressive loss in total numbers and in their ability to produce effector cytokines in the context of chronic LCMV infection. Unlike virus-specific T cells, OVA-specific Tm cells from chronically infected mice did not up-regulate the expression of inhibitory receptors, a hallmark feature of exhaustion in virus-specific T cells. Finally, OVA-specific Tm cells failed to mount a robust recall response after bacteria re-challenge both in the chronically infected and adoptively transferred naïve hosts. These results show that previously established bacteria-specific Tm cells become functionally impaired in the setting of an unrelated bystander chronic viral infection, which may contribute to poor immunity against other pathogens in the host with chronic viral infection.

Chronic Viral Infection Compromises the Quality of Circulating Mucosal-Associated Invariant T Cells and Follicular T Helper Cells via Expression of Inhibitory Receptors.

Chronic viral infection results in impaired immune responses rendering viral persistence. Here, we compared the quality of T-cell responses among chronic hepatitis B virus (HBV), hepatitis C virus (HCV) and human immunodeficiency virus (HIV)-infected individuals by examining the levels of expression of selected immune activation and exhaustion molecules on circulating MAIT cells and Tfh cells. Cytokines were measured using a commercial Bio-plex Pro Human Cytokine Grp I Panel 17-plex kit (BioRad, Hercules, CA, USA). Inflammation was assessed by measuring an array of plasma cytokines, and phenotypic alterations in CD4+ T cells including circulating Tfh cells, CD8+ T cells, and TCR iVα7.2+ MAIT cells in chronic HBV, HCV, and HIV-infected patients and healthy controls. The cells were characterized based on markers pertaining to immune activation (CD69, ICOS, and CD27) proliferation (Ki67), cytokine production (TNF-α, IFN-γ) and exhaustion (PD-1). The cytokine levels and T cell phenotypes together with cell markers were correlated with surrogate markers of disease progression. The activation marker CD69 was significantly increased in CD4+hi T cells, while CD8+ MAIT cells producing IFN-γ were significantly increased in chronic HBV, HCV and HIV infections. Six cell phenotypes, viz., TNF-α+CD4+lo T cells, CD69+CD8+ T cells, CD69+CD4+ MAIT cells, PD-1+CD4+hi T cells, PD-1+CD8+ T cells, and Ki67+CD4+ MAIT cells, were independently associated with decelerating the plasma viral load (PVL). TNF-α levels showed a positive correlation with increase in cytokine levels and decrease in PVL. Chronic viral infection negatively impacts the quality of peripheral MAIT cells and Tfh cells via differential expression of both activating and inhibitory receptors.

Helicobacter pylori enhances HLA-C expression in the human gastric adenocarcinoma cells AGS and can protect them from the cytotoxicity of natural killer cells.

Helicobacter pylori (H. pylori) seems to play causative roles in gastric cancers. H. pylori has also been detected in established gastric cancers. How the presence of H. pylori modulates immune response to the cancer is unclear. The cytotoxicity of natural killer (NK) cells, toward infected or malignant cells, is controlled by the repertoire of activating and inhibitory receptors expressed on their surface. Here, we studied H. pylori-induced changes in the expression of ligands, of activating and inhibitory receptors of NK cells, in the gastric adenocarcinoma AGS cells, and their impacts on NK cell responses. AGS cells lacked or had low surface expression of the class I major histocompatibility complex (MHC-I) molecules HLA-E and HLA-C-ligands of the major NK cell inhibitory receptors NKG2A and killer-cell Ig-like receptor (KIR), respectively. However, AGS cells had high surface expression of ligands of activating receptors DNAM-1 and CD2, and of the adhesion molecules LFA-1. Consistently, AGS cells were sensitive to killing by NK cells despite the expression of inhibitory KIR on NK cells. Furthermore, H. pylori enhanced HLA-C surface expression on AGS cells. H. pylori infection enhanced HLA-C protein synthesis, which could explain H. pylori-induced HLA-C surface expression. H. pylori infection enhanced HLA-C surface expression also in the hepatoma Huh7 and HepG2 cells. Furthermore, H. pylori-induced HLA-C surface expression on AGS cells promoted inhibition of NK cells by KIR, and thereby protected AGS cells from NK cell cytotoxicity. These results suggest that H. pylori enhances HLA-C expression in host cells and protects them from the cytotoxic attack of NK cells expressing HLA-C-specific inhibitory receptors.

A Systematic Review of the Advances in the Study of T Lymphocyte Suppressor Receptors in HBV Infection: Potential Therapeutic Targets.

Background: HBV-specific T lymphocytes are pivotal in eliminating the hepatitis B virus (HBV) and regulating intrahepatic inflammatory reactions. Effective T cell responses curtail HBV infection; however, compromised immunity can result in persistent infection. Beyond the acute phase, the continued presence of antigens and inflammation leads to the increased expression of various inhibitory receptors, such as PD-1, CTLA-4, Tim-3, LAG3, 2B4, CD160, BTLA, and TIGIT. This escalates the dysfunction of and diminishes the immune and proliferative abilities of T cells. Methods: In this study, we reviewed English-language literature from PubMed, Web of Science, and Scopus up to 9 July 2023. This paper aims to elucidate the inhibitory effects of these receptors on HBV-specific T lymphocytes and how immune function can be rejuvenated by obstructing the inhibitory receptor signaling pathway in chronic HBV patients. We also summarize the latest insights into related anti-HBV immunotherapy. Result: From 66 reviewed reports, we deduced that immunotherapy targeting inhibitory receptors on T cells is a reliable method to rejuvenate T cell immune responses in chronic HBV patients. However, comprehensive combination therapy strategies are essential for a functional cure. Conclusions: Targeting T cell suppressor receptors and combining immunotherapy with antiviral treatments may offer a promising approach towards achieving a functional cure, urging future research to prioritize effective combination therapeutic strategies for chronic HBV infection.

Tumor-immune metaphenotypes orchestrate an evolutionary bottleneck that promotes metabolic transformation.

Metabolism plays a complex role in the evolution of cancerous tumors, including inducing a multifaceted effect on the immune system to aid immune escape. Immune escape is, by definition, a collective phenomenon by requiring the presence of two cell types interacting in close proximity: tumor and immune. The microenvironmental context of these interactions is influenced by the dynamic process of blood vessel growth and remodelling, creating heterogeneous patches of well-vascularized tumor or acidic niches. Here, we present a multiscale mathematical model that captures the phenotypic, vascular, microenvironmental, and spatial heterogeneity which shapes acid-mediated invasion and immune escape over a biologically-realistic time scale. The model explores several immune escape mechanisms such as i) acid inactivation of immune cells, ii) competition for glucose, and iii) inhibitory immune checkpoint receptor expression (PD-L1). We also explore the efficacy of anti-PD-L1 and sodium bicarbonate buffer agents for treatment. To aid in understanding immune escape as a collective cellular phenomenon, we define immune escape in the context of six collective phenotypes (termed "meta-phenotypes"): Self-Acidify, Mooch Acid, PD-L1 Attack, Mooch PD-L1, Proliferate Fast, and Starve Glucose. Fomenting a stronger immune response leads to initial benefits (additional cytotoxicity), but this advantage is offset by increased cell turnover that leads to accelerated evolution and the emergence of aggressive phenotypes. This creates a bimodal therapy landscape: either the immune system should be maximized for complete cure, or kept in check to avoid rapid evolution of invasive cells. These constraints are dependent on heterogeneity in vascular context, microenvironmental acidification, and the strength of immune response. This model helps to untangle the key constraints on evolutionary costs and benefits of three key phenotypic axes on tumor invasion and treatment: acid-resistance, glycolysis, and PD-L1 expression. The benefits of concomitant anti-PD-L1 and buffer treatments is a promising treatment strategy to limit the adverse effects of immune escape.

In vivo PSC differentiation as a platform to identify factors for improving the engraftability of cultured muscle stem cells.

Producing an adequate number of muscle stem cells (MuSCs) with robust regenerative potential is essential for the successful cell therapy of muscle-wasting disorders. We have recently developed a method to produce skeletal myogenic cells with exceptional engraftability and expandability through an in vivo pluripotent stem cell (PSC) differentiation approach. We have subsequently mapped engraftment and gene expression and found that leukemia inhibitory factor receptor (Lifr) expression is positively correlated with engraftability. We therefore investigated the effect of LIF, the endogenous ligand of LIFR, on cultured MuSCs and examined their engraftment potential. We found that LIF-treated MuSCs exhibited elevated expression of PAX7, formed larger colonies from single cells, and favored the retention of PAX7+ "reserve cells" upon myogenic differentiation. This suggested that LIF promoted the maintenance of cultured MuSCs at a stem cell stage. Moreover, LIF enhanced the engraftment capability of MuSCs that had been expanded in vitro for 12 days by 5-fold and increased the number of MuSCs that repopulated the stem cell pool post-transplantation. These results thereby demonstrated the effectiveness of our in vivo PSC differentiation platform to identify positive regulators of the engraftability of cultured MuSCs.

Expression of a Novel Chimeric Inhibitory Receptor Attenuates CD19 CAR T Cells: A Promising Strategy for Toxicity Mitigation

Expression of a Novel Chimeric Inhibitory Receptor Attenuates CD19 CAR T Cells: A Promising Strategy for Toxicity Mitigation

A paradoxical switch: the implications of excitatory GABAergic signaling in neurological disorders.

Gamma-aminobutyric acid (GABA) is the primary inhibitory neurotransmitter in the central nervous system. In the mature brain, inhibitory GABAergic signaling is critical in maintaining neuronal homeostasis and vital human behaviors such as cognition, emotion, and motivation. While classically known to inhibit neuronal function under physiological conditions, previous research indicates a paradoxical switch from inhibitory to excitatory GABAergic signaling that is implicated in several neurological disorders. Various mechanisms have been proposed to contribute to the excitatory switch such as chloride ion dyshomeostasis, alterations in inhibitory receptor expression, and modifications in GABAergic synaptic plasticity. Of note, the hypothesized mechanisms underlying excitatory GABAergic signaling are highlighted in a number of neurodevelopmental, substance use, stress, and neurodegenerative disorders. Herein, we present an updated review discussing the presence of excitatory GABAergic signaling in various neurological disorders, and their potential contributions towards disease pathology.

Sirpα on tumor-associated myeloid cells restrains antitumor immunity in colorectal cancer independent of its interaction with CD47.

Immunosuppressive myeloid cells hinder immunotherapeutic efficacy in tumors, but the precise mechanisms remain undefined. Here, by performing single-cell RNA sequencing in colorectal cancer tissues, we found tumor-associated macrophages and granulocytic myeloid-derived suppressor cells increased most compared to their counterparts in normal tissue and displayed the highest immune-inhibitory signatures among all immunocytes. These cells exhibited significantly increased expression of immunoreceptor tyrosine-based inhibitory motif-bearing receptors, including SIRPA. Notably, Sirpa-/- mice were more resistant to tumor progression than wild-type mice. Moreover, Sirpα deficiency reprogramed the tumor microenvironment through expansion of TAM_Ccl8hi and gMDSC_H2-Q10hi subsets showing strong antitumor activity. Sirpa-/- macrophages presented strong phagocytosis and antigen presentation to enhance T cell activation and proliferation. Furthermore, Sirpa-/- macrophages facilitated T cell recruitment via Syk/Btk-dependent Ccl8 secretion. Therefore, Sirpα deficiency enhances innate and adaptive immune activation independent of expression of CD47 and Sirpα blockade could be a promising strategy to improve cancer immunotherapy efficacy.

LAIR1-mediated resistance of hepatocellular carcinoma cells to T cells through a GSK-3β/β-catenin/MYC/PD-L1 pathway

BackgroundAn increasing number of studies have reported the involvement of oncogenes in the regulation of the immune system. LAIR1 is an immunosuppressive molecule and its role in immune-related diseases has been mainly reported. To date, it is unclear whether LAIR1 in tumor cells is involved in immune regulation. Therefore, the aim of this study was to investigate the role of LAIR1 in the immune microenvironment of hepatocellular carcinoma (HCC) to seek the novel therapeutic discoveries. MethodsTumor Immune Dysfunction and Exclusion database was used to predict the response of LAIR1 expression to immune checkpoint blockade. CD8+ T cells were co-cultured with HCC cells, and the killing efficiency of leukocytes on HCC cells was detected by flow cytometry. Flow cytometry was also used to detect the expression of inhibitory receptors. In addition, Western blot, immunofluorescence, and nucleus/cytoplasm fractionation experiments were performed to explore the molecular mechanisms by which LAIR1 created a suppressive tumor microenvironment. ResultsLAIR1 expression in HCC was associated with worse immune prognosis and T-cell dysfunction. HCC cells overexpressing LAIR1 co-cultured with CD8+ T cells induced exhaustion of latter. Mechanism studies indicated that LAIR1 in HCC cells up-regulated the phosphorylation of β-catenin by inducing the phosphorylation of GSK-3β, leading to the impairment of the expression and the nuclear localization signal of β-catenin. Low β-catenin expression and nuclear localization signal inhibited MYC-mediated PD-L1 expression. Therefore, PD-L1 up-regulated by LAIR1 caused the exhaustion of infiltrating CD8+ T cells in HCC, which aggravated the malignant progression of HCC. ConclusionLAIR1 increased PD-L1 expression through the GSK-3β/β-catenin/MYC/PD-L1 pathway and promoted immune evasion of HCC cells. Targeted inhibition of LAIR1 helped to enhance the immune killing effect of CD8+ T cells in HCC.

TCell Exhaustion.

Tcell responses must be balanced to ensure adequate protection against malignant transformation and an array of pathogens while also limiting damage to healthy cells and preventing autoimmunity. Tcell exhaustion serves as a regulatory mechanism to limit the activity and effector function of Tcells undergoing chronic antigen stimulation. Exhausted Tcells exhibit poor proliferative potential; high inhibitory receptor expression; altered transcriptome, epigenome, and metabolism; and, most importantly, reduced effector function. While exhaustion helps to restrain damage caused by aberrant Tcells in settings of autoimmune disease, it also limits the ability of cells to respond against persistent infection and cancer, leading to disease progression. Here we review the process of Tcell exhaustion, detailing the key characteristics and drivers as well as highlighting our current understanding of the underlying transcriptional and epigenetic programming. We also discuss how exhaustion can be targeted to enhance Tcell functionality in cancer. Expected final online publication date for the Annual Review of Immunology, Volume 42 is April 2024. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.