Regulatory T cells sense effector T-cell activation through synchronized JunB expression

Serine enrichment in tumors promotes regulatory T cell accumulation through sphinganine-mediated regulation of c-Fos

CD4+ regulatory T (Treg) cells accumulate in the tumor microenvironment (TME) and suppress the immune system. Whether and how metabolite availability in the TME influences Treg cell differentiation is not understood. Here, we measured 630 metabolites in the TME and found that serine and palmitic acid, substrates required for the synthesis of sphingolipids, were enriched. A serine-free diet or a deficiency in Sptlc2, the rate-limiting enzyme catalyzing sphingolipid synthesis, suppressed Treg cell accumulation and inhibited tumor growth. Sphinganine, an intermediate metabolite in sphingolipid synthesis, physically interacted with the transcription factor c-Fos. Sphinganine c-Fos interactions enhanced the genome-wide recruitment of c-Fos to regions near the transcription start sites of target genes including Pdcd1 (encoding PD-1), which promoted Pdcd1 transcription and increased inducible Treg cell differentiation in vitro in a PD-1-dependent manner. Thus, Sptlc2-mediated sphingolipid synthesis translates the extracellular information of metabolite availability into nuclear signals for Treg cell differentiation and limits antitumor immunity.

LPS and type I and II interferons have opposing effects on epigenetic regulation of LAIR1 expression in mouse and human macrophages

Inhibitory immune receptors are important for maintaining immune homeostasis. We identified epigenetic alterations in 2 members of this group, LAIR1 and LAIR2, in lymphoma patients with inflammatory tissue damage and susceptibility to infection. We predicted that the expression of LAIR genes is controlled by immune mediators acting on transcriptional regulatory elements. Using flow cytometry, quantitative reverse-transcription polymerase chain reaction, and RNA sequencing, we measured LAIR1 and LAIR2 in human and murine immune cell subsets at baseline and posttreatment with immune mediators, including type I and II interferons, tumor necrosis factor α, and lipopolysaccharide (LPS). We identified candidate regulatory elements using epigenome profiling and measured their regulatory activity using luciferase reporters. LAIR1 expression substantially increases during monocyte differentiation to macrophages in both species. In contrast, murine and human macrophages exhibited opposite changes in LAIR1 in response to immune stimuli: human LAIR1 increased with LPS while mouse LAIR1 increased with interferon γ. LAIR genes had distinct patterns of enhancer activity with variable responses to immune stimuli. To identify relevant transcription factors (TFs), we developed integrative bioinformatic techniques applied to TF chromatin immunoprecipitation sequencing, RNA sequencing, and luciferase activity, revealing distinct sets of TFs for each LAIR gene. Most strikingly, LAIR1 TFs include nuclear factor kappa B factors RELA and RELB, while Lair1 and LAIR2 instead include STAT3 and/or STAT5. Regulation by nuclear factor kappa B factors may therefore explain the LPS-induced increase in LAIR1 expression, in contrast to Lair1 decrease. Our findings reveal new insights into transcriptional mechanisms that control distinct expression patterns of LAIR genes in response to inflammatory stimuli in human and murine myeloid and lymphoid cells.

Single-cell histone chaperones patterns guide intercellular communication of tumor microenvironment that contribute to breast cancer metastases

BACKGROUND

Histone chaperones (HCs) are crucial for governing genome stability and gene expression in multiple cancers. However, the functioning of HCs in the tumor microenvironment (TME) is still not clearly understood.

METHODS

Self-tested single-cell RNA-seq data derived from 6 breast cancer (BC) patients with brain and liver metastases were reanalyzed by nonnegative matrix factorization (NMF) algorithm for 36 HCs. TME subclusters were observed with BC and immunotherapy public cohorts to assess their prognosis and immune response. The biological effect of HSPA8, one of the HCs, was verified by transwell assay and wound-healing assays.

RESULTS

Cells including fibroblasts, macrophages, B cells, and T cells, were classified into various subclusters based on marker genes. Additionally, it showed that HCs might be strongly associated with biological and clinical features of BC metastases, along with the pseudotime trajectory of each TME cell type. Besides, the results of bulk-seq analysis revealed that TME cell subclusters mediated by HCs distinguished significant prognostic value for BC patients and were relevant to patients' immunotherapy responses, especially for B cells and macrophages. In particular, CellChat analysis exhibited that HCs-related TME cell subclusters revealed extensive and diverse interactions with malignant cells. Finally, transwell and wound-healing assays exhibited that HSPA8 deficiency inhibited BC cell migration and invasion.

CONCLUSIONS

Collectively, our study first dissected HCs-guided intercellular communication of TME that contribute to BC metastases.

Shock drives a STAT3 and JunB-mediated coordinated transcriptional and DNA methylation response in the endothelium

Endothelial dysfunction is a crucial factor in promoting organ failure during septic shock. However, the underlying mechanisms are unknown. Here, we show that kidney injury after lipopolysaccharide (LPS) insult leads to strong endothelial transcriptional and epigenetic responses. Furthermore, SOCS3 loss leads to an aggravation of the responses, demonstrating a causal role for the STAT3-SOCS3 signaling axis in the acute endothelial response to LPS. Experiments in cultured endothelial cells demonstrate that IL-6 mediates this response. Furthermore, bioinformatics analysis of in vivo and in vitro transcriptomics and epigenetics suggests a role for STAT, AP1 and interferon regulatory family (IRF) transcription factors. Knockdown of STAT3 or the AP1 member JunB partially prevents the changes in gene expression, demonstrating a role for these transcription factors. In conclusion, endothelial cells respond with a coordinated response that depends on overactivated IL-6 signaling via STAT3, JunB and possibly other transcription factors. Our findings provide evidence for a critical role of IL-6 signaling in regulating shock-induced epigenetic changes and sustained endothelial activation, offering a new therapeutic target to limit vascular dysfunction.

JunB: a paradigm for Jun family in immune response and cancer

Jun B proto-oncogene (JunB) is a crucial member of dimeric activator protein-1 (AP-1) complex, which plays a significant role in various physiological processes, such as placental formation, cardiovascular development, myelopoiesis, angiogenesis, endochondral ossification and epidermis tissue homeostasis. Additionally, it has been reported that JunB has great regulatory functions in innate and adaptive immune responses by regulating the differentiation and cytokine secretion of immune cells including T cells, dendritic cells and macrophages, while also facilitating the effector of neutrophils and natural killer cells. Furthermore, a growing body of studies have shown that JunB is involved in tumorigenesis through regulating cell proliferation, differentiation, senescence and metastasis, particularly affecting the tumor microenvironment through transcriptional promotion or suppression of oncogenes in tumor cells or immune cells. This review summarizes the physiological function of JunB, its immune regulatory function, and its contribution to tumorigenesis, especially focusing on its regulatory mechanisms within tumor-associated immune processes.

Co-expression of a PD-L1-specific chimeric switch receptor augments the efficacy and persistence of CAR T cells via the CD70-CD27 axis

Co-expression of chimeric switch receptors (CSRs) specific for PD-L1 improves the antitumor effects of chimeric antigen receptor (CAR) T cells. However, the effects of trans-recognition between CSRs and PD-L1 expressed by activated CAR T cells remain unclear. Here, we design a CSR specific for PD-L1 (CARP), containing the transmembrane and cytoplasmic signaling domains of CD28 but not the CD3 ζ chain. We show that CARP T cells enhance the antitumor activity of anti-mesothelin CAR (CARMz) T cells in vitro and in vivo. In addition, confocal microscopy indicates that PD-L1 molecules on CARMz T cells accumulate at cell-cell contacts with CARP T cells. Using single-cell RNA-sequencing analysis, we reveal that CARP T cells promote CARMz T cells differentiation into central memory-like T cells, upregulate genes related to Th1 cells, and downregulate Th2-associated cytokines through the CD70-CD27 axis. Moreover, these effects are not restricted to PD-L1, as CAR19 T cells expressing anti-CD19 CSR exhibit similar effects on anti-PSCA CAR T cells with truncated CD19 expression. These findings suggest that target trans-recognition by CSRs on CAR T cells may improve the efficacy and persistence of CAR T cells via the CD70-CD27 axis.

JUNB suppresses distant metastasis by influencing the initial metastatic stage

The complex interactions between cells of the tumor microenvironment and cancer cells are considered a major determinant of cancer progression and metastasis. Yet, our understanding of the mechanisms of metastatic disease is not sufficient to successfully treat patients with advanced-stage cancer. JUNB is a member of the AP-1 transcription factor family shown to be frequently deregulated in human cancer and associated with invasion and metastasis. A strikingly high stromal JUNB expression in human breast cancer samples prompted us to functionally investigate the consequences of JUNB loss in cells of the tumor microenvironment on cancer progression and metastasis in mice. To adequately mimic the clinical situation, we applied a syngeneic spontaneous breast cancer metastasis model followed by primary tumor resection and identified stromal JUNB as a potent suppressor of distant metastasis. Comprehensive characterization of the JUNB-deficient tumor microenvironment revealed a strong influx of myeloid cells into primary breast tumors and lungs at early metastatic stage. In these infiltrating neutrophils, BV8 and MMP9, proteins promoting angiogenesis and tissue remodeling, were specifically upregulated in a JUNB-dependent manner. Taken together, we established stromal JUNB as a strong suppressor of distant metastasis. Consequently, therapeutic strategies targeting AP-1 should be carefully designed not to interfere with stromal JUNB expression as this may be detrimental for cancer patients.

Arrest in the Progression of Type 1 Diabetes at the Mid-Stage of Insulitic Autoimmunity Using an Autoantigen-Decorated All-trans Retinoic Acid and Transforming Growth Factor Beta-1 Single Microparticle Formulation

Type 1 diabetes (T1D) is a disorder of impaired glucoregulation due to lymphocyte-driven pancreatic autoimmunity. Mobilizing dendritic cells (DC) in vivo to acquire tolerogenic activity is an attractive therapeutic approach as it results in multiple and overlapping immunosuppressive mechanisms. Delivery of agents that can achieve this, in the form of micro/nanoparticles, has successfully prevented a number of autoimmune conditions in vivo. Most of these formulations, however, do not establish multiple layers of immunoregulation. all-trans retinoic acid (RA) together with transforming growth factor beta 1 (TGFβ1), in contrast, has been shown to promote such mechanisms. When delivered in separate nanoparticle vehicles, they successfully prevent the progression of early-onset T1D autoimmunity in vivo. Herein, we show that the approach can be simplified into a single microparticle formulation of RA + TGFβ1 with surface decoration with the T1D-relevant insulin autoantigen. We show that the onset of hyperglycemia is prevented when administered into non-obese diabetic mice that are at the mid-stage of active islet-selective autoimmunity. Unexpectedly, the preventive effects do not seem to be mediated by increased numbers of regulatory T-lymphocytes inside the pancreatic lymph nodes, at least following acute administration of microparticles. Instead, we observed a mild increase in the frequency of regulatory B-lymphocytes inside the mesenteric lymph nodes. These data suggest additional and potentially-novel mechanisms that RA and TGFβ1 could be modulating to prevent progression of mid-stage autoimmunity to overt T1D. Our data further strengthen the rationale to develop RA+TGFβ1-based micro/nanoparticle “vaccines” as possible treatments of pre-symptomatic and new-onset T1D autoimmunity.

Regulation of T cell differentiation by the AP-1 transcription factor JunB

JunB, a component of the activator protein-1 (AP-1) transcription factor, is known to exhibit an important role in bone formation and bone marrow cell proliferation. During T helper type 2 (Th2) cell differentiation, JunB contributes to the regulation of interleukin (IL)-4 expression, and AP-1 and nuclear factor of activated T cell (NFAT) constitute a heteromer and contribute to IL-2 production. However, the role of JunB in other T cells has not been investigated. In 2017, it was revealed that JunB, in collaboration with basic leucine zipper ATF-like transcription factor (BATF), regulates the expression of Th17-related genes. Furthermore, JunB was found to play an important role in regulatory T (Treg) cell differentiation, contributing to CD25 expression and IL-2 production. IL-2 is a T cell activator and has been shown as a necessary factor for Treg proliferation. Here, we review the role of JunB in T cells based on basic research data and discuss the potential for its clinical applications.

Tracking the important role of JUNB in hepatocellular carcinoma by single-cell sequencing analysis

Hepatocellular carcinoma (HCC) is the most commonly diagnosed liver cancer, accounting for ~90% of all primary malignancy of the liver. Although various medical treatments have been used as systemic therapies, patient survival time may be extended by only a few months. Moreover, the underlying mechanisms of HCC development and progression remain poorly understood. In the present study, the single-cell transcriptome of one in vivo HCC tumor sample, two in vitro HCC cell lines and normal peripheral blood mononuclear cells were analysed in order to identify the potential mechanism underlying the development and progression of HCC. Interestingly, JunB proto-oncogene was identified to serve a role in the immune response and in development and progression of HCC, potentially contributing to the development of novel therapeutics for HCC patients.

Transcriptional Regulation of Differentiation and Functions of Effector T Regulatory Cells

Foxp3-expressing regulatory T (Treg) cells can suppress the activity of various types of immune cells and play key roles in the maintenance of self-tolerance and in the regulation of immune responses against pathogens and tumor cells. Treg cells consist of heterogeneous subsets that have distinct phenotypes and functions. Upon antigen stimulation, naïve-like thymus-derived Treg cells, which circulate in secondary lymphoid organs, can differentiate into effector Treg (eTreg) cells and migrate to and control immune homeostasis of peripheral tissues. eTreg cells are heterogeneous in terms of their ability to localize to specific tissues and suppress particular types of immune responses. Differentiation and function of diverse eTreg subsets are regulated by a variety of transcription factors that are activated by antigens and cytokines. In this article, we review the current understanding of the transcriptional regulation of differentiation and function of eTreg cells.