NAC1 modulates autoimmunity by suppressing regulatory T cell-mediated tolerance

FOXP3 (in)stability and cancer immunotherapy

Dysregulation of regulatory T cells (Tregs) is described in the context of inflammatory and autoimmune diseases, and cancer. Forkhead box P3 (FOXP3) is a transcription factor that its activity is an indicator of Treg identity. FOXP3 induces metabolic versatility in intra-tumoral Tregs, so that its deficiency mediates Treg instability or even gives rise to the acquisition of effector T cell phenotype. FOXP3 dysregulation and defectiveness occurs upon ubiquitination, methylation and presumably acetylation. Stimulators of PTEN, mammalian target of rapamycin complex 2 (mTORC2), and nucleus accumbens-associated protein-1 (NAC1), and inhibitors of B lymphocyte-induced maturation protein-1 (Blimp-1), Deltex1 (DTX1) and ubiquitin-specific peptidase 22 (USP22) are suggested to hamper FOXP3 stability, and to promote its downregulation and further Treg depletion. A point is that Treg subsets reveal different reliance on FOXP3, which indicates that not all Tregs are strictly dependent on FOXP3, and presumably Tregs with different origin rely on diverse regulators of FOXP3 stability. The focus of this review is over the current understanding toward FOXP3, its activity in Tregs and influence from different regulators within tumor microenvironment (TME). Implication of FOXP3 targeting in cancer immunotherapy is another focus of this paper.

Emerging strategies for nanomedicine in autoimmunity

Autoimmune disorders have risen to be among the most prevalent chronic diseases across the globe, affecting approximately 5-7% of the population. As autoimmune diseases steadily rise in prevalence, so do the number of potential therapeutic strategies to combat them. In recent years, fundamental research investigating autoimmune pathologies has led to the emergence of several cellular targets that provide new therapeutic opportunities. However, key challenges persist in terms of accessing and specifically combating the dysregulated, self-reactive cells while avoiding systemic immune suppression and other off-target effects. Fortunately, the continued advancement of nanomedicines may provide strategies to address these challenges and bring innovative autoimmunity therapies to the clinic. Through precise engineering and rational design, nanomedicines can possess a variety of physicochemical properties, surface modifications, and cargoes, allowing for specific targeting of therapeutics to pathological cell and organ types. These advances in nanomedicine have been demonstrated in cancer therapies and have the broad potential to advance applications in autoimmunity therapies as well. In this review, we focus on leveraging the power of nanomedicine for prevalent autoimmune disorders throughout the body. We expand on three key areas for the development of autoimmunity therapies - avoiding systemic immunosuppression, balancing interactions with the immune system, and elevating current platforms for delivering complex cargoes - and emphasize how nanomedicine-based strategies can overcome these barriers and enable the development of next-generation, clinically relevant autoimmunity therapies.

An overview of the co-transcription factor NACC1: Beyond its pro-tumor effects

Nucleus accumbens-associated protein 1 (NACC1) is a member of the broad complex, tramtrack, bric-a-brac/poxvirus and zinc finger (BTB/POZ) protein families, mainly exerting its biological functions as a transcription co-regulator. NACC1 forms homo- or hetero-dimers through the BTB/POZ or BANP, E5R, and NACC1 (BEN) domain with other transcriptional regulators to regulate downstream signals. Recently, the overexpression of NACC1 has been observed in various tumors and is positively associated with tumor progression, high recurrence rate, indicating poor prognosis. NACC1 also regulates biological processes such as embryonic development, stem cell pluripotency, innate immunity, and related diseases. Our review combines recent research to summarize advancements in the structure, biological functions, and relative molecular mechanisms of NACC1. The future development of NACC1 clinical appliances is also discussed.

PIM kinases regulate early human Th17 cell differentiation

The serine/threonine-specific Moloney murine leukemia virus (PIM) kinase family (i.e., PIM1, PIM2, and PIM3) has been extensively studied in tumorigenesis. PIM kinases are downstream of several cytokine signaling pathways that drive immune-mediated diseases. Uncontrolled T helper 17 (Th17) cell activation has been associated with the pathogenesis of autoimmunity. However, the detailed molecular function of PIMs in human Th17 cell regulation has yet to be studied. In the present study, we comprehensively investigated how the three PIMs simultaneously alter transcriptional gene regulation during early human Th17 cell differentiation. By combining PIM triple knockdown with bulk and scRNA-seq approaches, we found that PIM deficiency promotes the early expression of key Th17-related genes while suppressing Th1-lineage genes. Further, PIMs modulate Th cell signaling, potentially via STAT1 and STAT3. Overall, our study highlights the inhibitory role of PIMs in human Th17 cell differentiation, thereby suggesting their association with autoimmune phenotypes.

Control of CD4+ T cells to restrain inflammatory diseases via eukaryotic elongation factor 2 kinase

CD4+ T cells, particularly IL-17-secreting helper CD4+ T cells, play a central role in the inflammatory processes underlying autoimmune disorders. Eukaryotic Elongation Factor 2 Kinase (eEF2K) is pivotal in CD8+ T cells and has important implications in vascular dysfunction and inflammation-related diseases such as hypertension. However, its specific immunological role in CD4+ T cell activities and related inflammatory diseases remains elusive. Our investigation has uncovered that the deficiency of eEF2K disrupts the survival and proliferation of CD4+ T cells, impairs their ability to secrete cytokines. Notably, this dysregulation leads to heightened production of pro-inflammatory cytokine IL-17, fosters a pro-inflammatory microenvironment in the absence of eEF2K in CD4+ T cells. Furthermore, the absence of eEF2K in CD4+ T cells is linked to increased metabolic activity and mitochondrial bioenergetics. We have shown that eEF2K regulates mitochondrial function and CD4+ T cell activity through the upregulation of the transcription factor, signal transducer and activator of transcription 3 (STAT3). Crucially, the deficiency of eEF2K exacerbates the severity of inflammation-related diseases, including rheumatoid arthritis, multiple sclerosis, and ulcerative colitis. Strikingly, the use of C188-9, a small molecule targeting STAT3, mitigates colitis in a murine immunodeficiency model receiving eEF2K knockout (KO) CD4+ T cells. These findings emphasize the pivotal role of eEF2K in controlling the function and metabolism of CD4+ T cells and its indispensable involvement in inflammation-related diseases. Manipulating eEF2K represents a promising avenue for novel therapeutic approaches in the treatment of inflammation-related disorders.

Targeting post-translational modifications of Foxp3: a new paradigm for regulatory T cell-specific therapy

A healthy immune system is pivotal for the hosts to resist external pathogens and maintain homeostasis; however, the immunosuppressive tumor microenvironment (TME) damages the anti-tumor immunity and promotes tumor progression, invasion, and metastasis. Recently, many studies have found that Foxp3+ regulatory T (Treg) cells are the major immunosuppressive cells that facilitate the formation of TME by promoting the development of various tumor-associated cells and suppressing the activity of effector immune cells. Considering the role of Tregs in tumor progression, it is pivotal to identify new therapeutic drugs to target and deplete Tregs in tumors. Although several studies have developed strategies for targeted deletion of Treg to reduce the TME and support the accumulation of effector T cells in tumors, Treg-targeted therapy systematically affects the Treg population and may lead to the progression of autoimmune diseases. It has been understood that, nevertheless, in disease conditions, Foxp3 undergoes several definite post-translational modifications (PTMs), including acetylation, glycosylation, phosphorylation, ubiquitylation, and methylation. These PTMs not only elevate or mitigate the transcriptional activity of Foxp3 but also affect the stability and immunosuppressive function of Tregs. Various studies have shown that pharmacological targeting of enzymes involved in PTMs can significantly influence the PTMs of Foxp3; thus, it may influence the progression of cancers and/or autoimmune diseases. Overall, this review will help researchers to understand the advances in the immune-suppressive mechanisms of Tregs, the post-translational regulations of Foxp3, and the potential therapeutic targets and strategies to target the Tregs in TME to improve anti-tumor immunity.

Melanoma-intrinsic NR2F6 activity regulates antitumor immunity

Nuclear receptors (NRs) are implicated in the regulation of tumors and immune cells. We identify a tumor-intrinsic function of the orphan NR, NR2F6, regulating antitumor immunity. NR2F6 was selected from 48 candidate NRs based on an expression pattern in melanoma patient specimens (i.e., IFN-γ signature) associated with positive responses to immunotherapy and favorable patient outcomes. Correspondingly, genetic ablation of NR2F6 in a mouse melanoma model conferred a more effective response to PD-1 therapy. NR2F6 loss in B16F10 and YUMM1.7 melanoma cells attenuated tumor development in immune-competent but not -incompetent mice via the increased abundance of effector and progenitor-exhausted CD8⁺ T cells. Inhibition of NACC1 and FKBP10, identified as NR2F6 effectors, phenocopied NR2F6 loss. Inoculation of NR2F6 KO mice with NR2F6 KD melanoma cells further decreased tumor growth compared with NR2F6 WT mice. Tumor-intrinsic NR2F6 function complements its tumor-extrinsic role and justifies the development of effective anticancer therapies.

NAC1 confines virus-specific memory formation of CD4+ T cells through the ROCK1-mediated pathway

Nucleus accumbens-associated protein 1 (NAC1), a transcriptional cofactor, has been found to play important roles in regulating regulatory T cells, CD8+ T cells, and antitumor immunity, but little is known about its effects on T-cell memory. In this study, we found that NAC1 expression restricts memory formation of CD4+ T cells during viral infection. Analysis of CD4+ T cells from wild-type (WT) and NAC1-deficient (-/- ) mice showed that NAC1 is essential for T-cell metabolism, including glycolysis and oxidative phosphorylation, and supports CD4+ T-cell survival in vitro. We further demonstrated that a deficiency of NAC1 downregulates glycolysis and correlates with the AMPK-mTOR pathway and causes autophagy defective in CD4+ T cells. Loss of NAC1 reduced the expression of ROCK1 and the phosphorylation and stabilization of BECLIN1. However, a forced expression of ROCK1 in NAC1-/- CD4+ T cells restored autophagy and the activity of the AMPK-mTOR pathway. In animal experiments, adoptively transferred NAC1-/- CD4+ T cells or NAC1-/- mice challenged with VACV showed enhanced formation of VACV-specific CD4+ memory T cells compared to adoptively transferred WT CD4+ T cells or WT mice. This memory T-cell formation enhancement was abrogated by forcing expression of ROCK1. Our study reveals a novel role for NAC1 as a suppressor of CD4+ T-cell memory formation and suggests that targeting NAC1 could be a new approach to promoting memory CD4+ T-cell development, which is critical for an effective immune response against pathogens.

Identification of a NACC1-Regulated Gene Signature Implicated in the Features of Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC), characterized by a deficiency in estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor2 (HER2), is among the most lethal subtypes of breast cancer (BC). Nevertheless, the molecular determinants that contribute to its malignant phenotypes such as tumor heterogeneity and therapy resistance, remain elusive. In this study, we sought to identify the stemness-associated genes involved in TNBC progression. Using bioinformatics approaches, we found 55 up- and 9 downregulated genes in TNBC. Out of the 55 upregulated genes, a 5 gene-signature (CDK1, EZH2, CCNB1, CCNA2, and AURKA) involved in cell regeneration was positively correlated with the status of tumor hypoxia and clustered with stemness-associated genes, as recognized by Parametric Gene Set Enrichment Analysis (PGSEA). Enhanced infiltration of immunosuppressive cells was also positively correlated with the expression of these five genes. Moreover, our experiments showed that depletion of the transcriptional co-factor nucleus accumbens-associated protein 1 (NAC1), which is highly expressed in TNBC, reduced the expression of these genes. Thus, the five genes signature identified by this study warrants further exploration as a potential new biomarker of TNBC heterogeneity/stemness characterized by high hypoxia, stemness enrichment, and immune-suppressive tumor microenvironment.

Tonic-signaling chimeric antigen receptors drive human regulatory T cell exhaustion

Regulatory T cell (Treg) therapy is a promising approach to improve outcomes in transplantation and autoimmunity. In conventional T cell therapy, chronic stimulation can result in poor in vivo function, a phenomenon termed exhaustion. Whether or not Tregs are also susceptible to exhaustion, and if so, if this would limit their therapeutic effect, was unknown. To "benchmark" exhaustion in human Tregs, we used a method known to induce exhaustion in conventional T cells: expression of a tonic-signaling chimeric antigen receptor (TS-CAR). We found that TS-CAR-expressing Tregs rapidly acquired a phenotype that resembled exhaustion and had major changes in their transcriptome, metabolism, and epigenome. Similar to conventional T cells, TS-CAR Tregs upregulated expression of inhibitory receptors and transcription factors such as PD-1, TIM3, TOX and BLIMP1, and displayed a global increase in chromatin accessibility-enriched AP-1 family transcription factor binding sites. However, they also displayed Treg-specific changes such as high expression of 4-1BB, LAP, and GARP. DNA methylation analysis and comparison to a CD8+ T cell-based multipotency index showed that Tregs naturally exist in a relatively differentiated state, with further TS-CAR-induced changes. Functionally, TS-CAR Tregs remained stable and suppressive in vitro but were nonfunctional in vivo, as tested in a model of xenogeneic graft-versus-host disease. These data are the first comprehensive investigation of exhaustion in Tregs and reveal key similarities and differences with exhausted conventional T cells. The finding that human Tregs are susceptible to chronic stimulation-driven dysfunction has important implications for the design of CAR Treg adoptive immunotherapy strategies.

Expression of nucleus accumbens-1 in colon cancer negatively modulates antitumor immunity

BACKGROUND

Nucleus accumbens-1 (NAC-1) is highly expressed in a variety of tumors, including colon cancer, and is closely associated with tumor recurrence, metastasis, and invasion.

AIM

To determine whether and how NAC-1 affects antitumor immunity in colon cancer.

METHODS

NAC-1-siRNA was transfected into RKO colon cancer cells to knock down NAC expression; tumor cells with or without knockdown of NAC-1 were treated with CD8⁺ T cells to test their cytocidal effect. The level of the immune checkpoint programmed death receptor-1 ligand (PD-L1) in colon cancer cells with or without knockdown of NAC-1 was analyzed using Quantitative real-time polymerase chain reaction and Western blotting. A double luciferase reporter assay was used to examine the effects of NAC-1 on the transcription of PD-L1. Mice bearing MC-38-OVA colon cancer cells expressing NAC-shRNA or control-shRNA were treated with OT-I mouse CD8⁺ T cells to determine the tumor response to immunotherapy. Immune cells in the tumor tissues were analyzed using flow cytometry. NAC-1, PD-L1 and CD8⁺ T cells in colon cancer specimens from patients were examined using immunohistochemistry staining.

RESULTS

Knockdown of NAC-1 expression in colon cancer cells significantly enhanced the cytocidal effect of CD8⁺ T cells in cell culture experiments. The sensitizing effect of NAC-1 knockdown on the antitumor action of cytotoxic CD8⁺ T cells was recapitulated in a colon cancer xenograft animal model. Furthermore, knockdown of NAC-1 in colon cancer cells decreased the expression of PD-L1 at both the mRNA and protein levels, and this effect could be rescued by transfection of an RNAi-resistant NAC-1 expression plasmid. In a reporter gene assay, transient expression of NAC-1 in colon cancer cells increased the promoter activity of PD-L1, indicating that NAC-1 regulates PD-L1 expression at the transcriptional level. In addition, depletion of tumoral NAC-1 increased the number of CD8⁺ T cells but decreased the number of suppressive myeloid-derived suppressor cells and regulatory T cells.

CONCLUSION

Tumor expression of NAC-1 is a negative determinant of immunotherapy.

Tumorous expression of NAC1 restrains antitumor immunity through the LDHA-mediated immune evasion

BACKGROUND

T cell-mediated antitumor immunity has a vital role in cancer prevention and treatment; however, the immune-suppressive tumor microenvironment (TME) constitutes a significant contributor to immune evasion that weakens antitumor immunity. Here, we explore the relationship between nucleus accumbens-associated protein-1 (NAC1), a nuclear factor of the BTB (broad-complex, Tramtrack, bric a brac)/POZ (Poxvirus, and Zinc finger) gene family, and the TME.

METHODS

Adoptive cell transfer (ACT) of mouse or human tumor antigen (Ag)-specific CD8+ cytotoxic T lymphocytes (CTLs) was tested in an immunocompetent or immunodeficient mouse model of melanoma with or without expression of NAC1. The effects of NAC1 expression on immune evasion in tumor cells were assessed in vitro and in vivo. CRISPR/Cas9, glycolysis analysis, retroviral transduction, quantitative real-time PCR, flow cytometric analysis, immunoblotting, database analyses were used to screen the downstream target and underlying mechanism of NAC1 in tumor cells.

RESULTS

Tumorous expression of NAC1 negatively impacts the CTL-mediated antitumor immunity via lactate dehydrogenase A (LDHA)-mediated suppressive TME. NAC1 positively regulated the expression of LDHA at the transcriptional level, which led to higher accumulation of lactic acid in the TME. This inhibited the cytokine production and induced exhaustion and apoptosis of CTLs, impairing their cell-killing ability. In the immunocompetent and immunodeficient mice, NAC1 depleted melanoma tumors grew significantly slower and had an elevated infiltration of tumor Ag-specific CTLs following ACT, compared with the control groups.

CONCLUSIONS

Tumor expression of NAC1 contributes substantially to immune evasion through its regulatory role in LDHA expression and lactic acid production. Thus, therapeutic targeting of NAC1 warrants further exploration as a potential strategy to reinforce cancer immunotherapy, such as the ACT of CTLs.

Expression of NAC1 Restrains the Memory Formation of CD8+ T Cells during Viral Infection

Nucleus accumbens-associated protein 1 (NAC1) is a transcription co-factor that has been shown to possess multiple roles in stem cell and cancer biology. However, little is known about its roles in regulation of the immune system. In the current study, we observed that expression of NAC1 impacted the survival of CD8+ T cells in vitro. NAC1-/- CD8+ T cells displayed lower metabolism, including reduced glycolysis and oxidative phosphorylation. In vivo, compared with wild-type (WT) mice, NAC1-/- mice produced a lower response to vaccinia virus (VACV) infection, and viral antigen (Ag)-specific CD8+ T cells decreased more slowly. Additionally, we observed that the NAC1-/- mice demonstrated a stronger memory formation of viral Ag-specific CD8+ T cells post-viral infection. Mechanically, we identified that compared with WT CD8+ T cells, the Interferon Regulatory Factor 4 (IRF4), a key transcription factor in T cell development, was highly expressed in NAC1-/- CD8+ T cells, insinuating that IRF4 could be a critical regulatory target of NAC1 in the memory formation of CD8+ T cells. Our results indicate that NAC1 restrains the memory formation of CD8+ T cells by modulating IRF4, and targeting NAC1 may be exploited as a new approach to boosting CD8+ T cell memory.

A metabolically engineered bacterium controls autoimmunity and inflammation by remodeling the pro-inflammatory microenvironment

Immunotherapy has led to impressive advances in the treatment of autoimmune and pro-inflammatory disorders; yet, its clinical outcomes remain limited by a variety of factors including the pro-inflammatory microenvironment (IME). Discovering effective immunomodulatory agents, and the mechanisms by which they control disease, will lead to innovative strategies for enhancing the effectiveness of current immunotherapeutic approaches. We have metabolically engineered an attenuated bacterial strain (i.e., Brucella melitensis 16M ∆vjbR, Bm∆vjbR::tnaA) to produce indole, a tryptophan metabolite that controls the fate and function of regulatory T (Treg) cells. We demonstrated that treatment with Bm∆vjbR::tnaA polarized macrophages (Mφ) which produced anti-inflammatory cytokines (e.g., IL-10) and promoted Treg function; moreover, when combined with adoptive cell transfer (ACT) of Treg cells, a single treatment with our engineered bacterial strain dramatically reduced the incidence and score of autoimmune arthritis and decreased joint damage. These findings show how a metabolically engineered bacterium can constitute a powerful vehicle for improving the efficacy of immunotherapy, defeating autoimmunity, and reducing inflammation by remodeling the IME and augmenting Treg cell function.