Dexamethasone enhances CTLA-4 expression during T cell activation

Preclinical pediatric brain tumor models for immunotherapy: Hurdles and a way forward

Brain tumors are the most common solid tumor in children and the leading cause of cancer-related deaths. Over the last few years, improvements have been made in the diagnosis and treatment of children with Central Nervous System tumors. Unfortunately, for many patients with high-grade tumors, the overall prognosis remains poor. Lower survival rates are partly attributed to the lack of efficacious therapies. The advent and success of immune checkpoint inhibitors (ICIs) in adults have sparked interest in investigating the utility of these therapies alone or in combination with other drug treatments in pediatric patients. However, to achieve improved clinical outcomes, the establishment and selection of relevant and robust preclinical pediatric high-grade brain tumor models is imperative. Here, we review the information that influenced our model selection as we embarked on an international collaborative study to test ICIs in combination with epigenetic modifying agents to enhance adaptive immunity to treat pediatric brain tumors. We also share challenges that we faced and potential solutions.

Immune and ionic mechanisms mediating the effect of dexamethasone in severe COVID-19

Introduction

Severe COVID-19 is characterized by cytokine storm, an excessive production of proinflammatory cytokines that contributes to acute lung damage and death. Dexamethasone is routinely used to treat severe COVID-19 and has been shown to reduce patient mortality. However, the mechanisms underlying the beneficial effects of dexamethasone are poorly understood.

Methods

We conducted transcriptomic analysis of peripheral blood mononuclear cells (PBMCs) from COVID-19 patients with mild disease, and patients with severe COVID-19 with and without dexamethasone treatment. We then treated healthy donor PBMCs in vitro with dexamethasone and investigated the effects of dexamethasone treatment ion channel abundance (by RT-qPCR and flow cytometry) and function (by electrophysiology, Ca2+ influx measurements and cytokine release) in T cells.

Results

We observed that dexamethasone treatment in severe COVID-19 inhibited pro-inflammatory and immune exhaustion pathways, circulating cytotoxic and Th1 cells, interferon (IFN) signaling, genes involved in cytokine storm, and Ca²⁺ signaling. Ca²⁺ influx is regulated by Kv1.3 potassium channels, but their role in COVID-19 pathogenesis remains elusive. Kv1.3 mRNA was increased in PBMCs of severe COVID-19 patients, and was significantly reduced in the dexamethasone-treated group. In agreement with these findings, in vitro treatment of healthy donor PBMCs with dexamethasone reduced Kv1.3 abundance in T cells and CD56dimNK cells. Furthermore, functional studies showed that dexamethasone treatment significantly reduced Kv1.3 activity, Ca2+ influx and IFN-g production in T cells.

Conclusion

Our findings suggest that dexamethasone attenuates inflammatory cytokine release via Kv1.3 suppression, and this mechanism contributes to dexamethasone-mediated immunosuppression in severe COVID-19.

Stress-induced immunosuppression affecting immune response to Newcastle disease virus vaccine through "miR-155-CTLA-4" pathway in chickens

MiR-155 and CTLA-4 are important factors involved in the regulation of immune function. However, there is no report about their involvement in function regulation of stress-induced immunosuppression affecting immune response. In this study, the chicken model of stress-induced immunosuppression affecting immune response (simulation with dexamethasone and immunization with Newcastle disease virus (NDV) attenuated vaccine) was established, then the expression characteristics of miR-155 and CTLA-4 gene were analyzed at several key time points during the processes of stress-induced immunosuppression affecting NDV vaccine immune response at serum and tissue levels. The results showed that miR-155 and CTLA-4 were the key factors involved in stress-induced immunosuppression and NDV immune response, whose functions involved in the regulation of immune function were different in different tissues and time points, and 2 day post immunization (dpi), 5dpi and 21dpi were the possible key regulatory time points. CTLA-4, the target gene of miR-155, had significant game regulation relationships between them in various tissues, such as bursa of Fabricius, thymus and liver, indicating that miR-155-CTLA-4 pathway was one of the main mechanisms of their involvement in the regulations of stress-induced immunosuppression affecting NDV immune response. This study can lay the foundation for in-depth exploration of miR-155-CTLA-4 pathway involved in the regulation of immune function.

T cell-mediated autoimmunity in immune thrombocytopenia

Immune thrombocytopenia (ITP) is an autoimmune disorder characterized by a low platelet count and an increased risk of bleeding. In addition to anti-platelet autoantibodies, CD8⁺ T cells have been implicated as a mechanism of platelet destruction. The current evidence for the existence of platelet-specific CD8⁺ T cells in ITP is inconclusive. The purpose of this review is to summarize the studies that investigated CD8⁺ T cells in ITP and to review the methods that have been used to detect autoreactive CD8⁺ T cells in other autoimmune diseases.

The Sledgehammer in Precision Medicine: Dexamethasone and Immunotherapeutic Treatment of Glioma

Understanding dexamethasone's effect on the immune microenvironment in glioma patients is of key importance. We performed a comprehensive literature review using the NCBI PubMed database for all articles meeting the following search criteria. ((dexamethasone[All Fields]) AND (glioma or glioblastoma)[Title/Abstract]) AND (immune or T cell or B cell or monocyte or neutrophil or macrophage). Forty-three manuscripts were deemed relevant to the topic at hand. Multiple clinical studies have linked dexamethasone use to decreased overall survival while preclinical studies in murine glioma models have demonstrated decreased tumor-infiltrating lymphocytes after dexamethasone administration.

Expression Profiling of Primary and Recurrent Glioblastomas Reveals a Reduced Level of Pentraxin 3 in Recurrent Glioblastomas

Glioblastomas (GBM) are highly infiltrative tumors and despite intensive treatment tumor recurrence is inevitable. The immune microenvironment in recurrent GBM is poorly characterized, but it is potentially influenced by therapeutic interventions with surgery, radiotherapy, and chemotherapy. The aim of this study was to obtain a deeper insight in the immune microenvironment in primary and recurrent GBM. Primary and recurrent glioblastoma samples from 18 patients were identified and expression profiling of 770 myeloid innate immune-related markers was performed. Leukemia inhibitory factor and pentraxin 3 were expressed at lower levels in recurrent tumors. Using in silico data and immunohistochemical staining, this was validated for pentraxin 3. Both high leukemia inhibitory factor and pentraxin 3 expression appeared to be associated with shorter survival in primary and recurrent GBM using in silico data. In primary GBM, gene set analysis also showed higher expression of genes involved in metabolism, extracellular matrix remodeling and complement activation, whereas genes involved in T cell activation and checkpoint signaling were expressed at higher levels in recurrent GBM. The reduced level of pentraxin 3 in recurrent glioblastomas and the gene set analysis results suggest an altered microenvironment in recurrent GBM that might be more active.

Systemic Immunomodulatory Effects of Combinatorial Treatment of Thalidomide and Dexamethasone on T Cells and Other Immune Cells

PURPOSE

In organ transplantation, the need for immune modulation rather than immune suppression has been emphasized. In this study, we investigated whether combinatorial treatments of with thalidomide (TM) and dexamethasone (DX) might be new approaches to induce systemic immunomodulation on T cells and other immune cells that regulate the expression of co-inhibitory molecules.

MATERIALS AND METHODS

Naïve splenic T cells from C57BL/6 mice were sort-purified and cultured in vitro for CD4+ T cell proliferation and regulatory T cell (Treg) conversion in the presence of TM or/and DX. Expression of cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) and programmed death-1 (PD-1) in proliferated and converted T cells was quantified by flow cytometry. We also quantified in vivo expression of CTLA-4 and PD-1 on splenic CD4+ T cells and other immune cells isolated from TM- or/and DX-treated mice. Mixed lymphocytes reactions (MLR) were performed to evaluate the capacity of immune cells in carrying out immune responses.

RESULTS

CTLA-4 expressions in effector T cells in vivo and in Tregs in vivo/vitro significantly increased upon TM/DX combinatorial treatment. Corresponding to increased CTLA-4 expression in T cells, the expression of ligand molecules for CTLA-4 significantly increased in splenic dendritic cells in TM/DX-treated groups. In addition, MLR results demonstrated that splenocytes isolated from TM/DX-treated mice significantly suppressed the proliferation of T cells isolated from other strains.

CONCLUSION

Based on these results, we suggest that TM/DX combinatorial treatments might be efficient immunomodulatory methods for regulating T cell immunity.

CRISPR-Cas9-Edited Tacrolimus-Resistant Antiviral T Cells for Advanced Adoptive Immunotherapy in Transplant Recipients

Viral infections, such as with cytomegalovirus (CMV), remain a major risk factor for mortality and morbidity of transplant recipients because of their requirement for lifelong immunosuppression (IS). Antiviral drugs often cause toxicity and sometimes fail to control disease. Thus, regeneration of the antiviral immune response by adoptive antiviral T cell therapy is an attractive alternative. Our recent data, however, show only short-term efficacy in some solid organ recipients, possibly because of malfunction in transferred T cells caused by ongoing IS. We developed a vector-free clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9-based good manufacturing practice (GMP)-compliant protocol that efficiently targets and knocks out the gene for the adaptor protein FK506-binding protein 12 (FKBP12), required for the immunosuppressive function of tacrolimus. This was achieved by transient delivery of ribonucleoprotein complexes into CMV-specific T cells by electroporation. We confirmed the tacrolimus resistance of our gene-edited T cell products in vitro and demonstrated performance comparable with non-tacrolimus-treated unmodified T cells. The alternative calcineurin inhibitor cyclosporine A can be administered as a safety switch to shut down tacrolimus-resistant T cell activity in case of adverse effects. Furthermore, we performed safety assessments as a prerequisite for translation to first-in-human applications.

Glucocorticoids in T cell development, differentiation and function

Glucocorticoids (GCs) are small lipid hormones produced by the adrenals that maintain organismal homeostasis. Circadian and stress-induced changes in systemic GC levels regulate metabolism, cardiovascular and neural function, reproduction and immune activity. Our understanding of GC effects on immunity comes largely from administration of exogenous GCs to treat immune or inflammatory disorders. However, it is increasingly clear that endogenous GCs both promote and suppress T cell immunity. Examples include selecting an appropriate repertoire of T cell receptor (TCR) self-affinities in the thymus, regulating T cell trafficking between anatomical compartments, suppressing type 1 T helper (T_H1) cell responses while permitting T_H2 cell and, especially, IL-17-producing T helper cell responses, and promoting memory T cell differentiation and maintenance. Furthermore, in addition to functioning at a distance, extra-adrenal (local) production allows GCs to act as paracrine signals, specifically targeting activated T cells in various contexts in the thymus, mucosa and tumours. These pleiotropic effects on different T cell populations during development and immune responses provide a nuanced understanding of how GCs shape immunity.

The glucocorticoids prednisone and dexamethasone differentially modulate T cell function in response to anti-PD-1 and anti-CTLA-4 immune checkpoint blockade

On-treatment steroids for countering immune checkpoint inhibitor-induced inflammatory responses (irAEs) are a hallmark of cancer immunotherapy. However, the suppressive nature of steroids has raised questions regarding their ability to compromise the function of the 'proliferative burst' of effector T cells induced by immune checkpoint antibodies. We investigated the effector functions and the co-inhibitory receptor profile of stimulated peripheral blood mononuclear cells (PBMCs) pre-treated with prednisone and dexamethasone alone or in the presence of anti-PD-1/CTLA-4 antibodies. Also, clinical analysis of a patient who exhibited irAEs following combination (anti-PD-1/CTLA-4) in the presence of glucocorticoids was done. We found that prednisone in contrast to dexamethasone did not compromise T cell cytokine production (IL-2, IFN-γ and TNF-α) and proliferation in the absence or presence of anti-PD-1/CTLA-4 antibodies, when a physiological concentration was used. Neither single prednisone treatment nor co-treatment with checkpoint inhibitors impacted the expression of co-inhibitory receptors PD-1, CTLA-4, TIM-3 and LAG-3. In contrast, dexamethasone treatment promoted downregulation of LAG-3 expression by T cells. In addition, co-treatment of PD-1 + Jurkat cells with prednisone and/or dexamethasone with anti-PD-1 before stimulation significantly reduced SHP-2 phosphorylation, indicative of increased T cell function. Our findings hereby demonstrate a differential steroid effect on T cell function, which should be taken into consideration for patients undergoing immunotherapy. Also, the clinical analysis of a patient who exhibited irAEs following combination (anti-PD-1/CTLA-4) therapy indicated complete metabolic response in the presence of glucocorticoids. Therefore, concomitant use of prednisone does not appear to interfere with the function of immune checkpoint blockade.

The Role of Checkpoint Inhibitors in Glioblastoma

Given its poor prognosis, glioblastoma represents an area of high unmet clinical need. Standard of care for the treatment of glioblastoma in the frontline setting is limited to surgical resection, radiation, and temozolomide, with the more recent addition of Tumor Treating Fields. Several agents, including bevacizumab, lomustine, and carmustine have been approved in the recurrent setting. To date, no therapies have demonstrated substantial survival benefit beyond standard of care. An expanding understanding of the role of the immune system in fighting cancer has led to the development and approval of various immunotherapeutic approaches across solid tumors. In glioblastoma, the notion of a highly immune-restricted central nervous system has also evolved, further providing the rationale for testing therapies that promote immune trafficking to the CNS and infiltration into the tumor to counteract the immunosuppressive mechanisms that support tumor progression. There are five broad categories of immunotherapies currently being tested in GBM: vaccines, cytokine therapy, oncolytic viral therapy, chimeric antigen receptor T cell therapy, and checkpoint inhibitors. This review focuses on checkpoint inhibitors in GBM, the rationale for its use, preclinical data, and early clinical experience. Efficacy data are limited, and while a number of late-stage trials are ongoing, early trials showed no benefit in survival. There is a dizzying array of combinations being tested in clinical studies with an urgent need for a rational approach to determine the role of checkpoint inhibitors in glioblastoma, including the optimal combinations, and identification of biomarkers or predictive models to determine which patients may benefit from immunotherapy.

Glucocorticoids and immune checkpoint inhibitors in glioblastoma

PURPOSE

Immunotherapy, activation of the immune system to target tumor cells, represents a paradigm shift in the treatment of cancer. Immune checkpoint therapies, which target immunomodulatory molecules expressed on T-lymphocytes, have demonstrated improved survival in a variety of malignancies. However, benefit in glioblastoma, the most common and devastating malignant brain tumor, remains to be seen. With several recent clinical trials failing to show efficacy of immunotherapy, concerns have been raised regarding the impact of glucocorticoid use in this patient population that may impair the ability for immune checkpoint inhibitors to affect a response.

METHODS

For this article we examined the mechanism by which immune checkpoint inhibitors activate, and glucocorticoids impair, T-lymphocyte function.

RESULTS

In this context, we review the clinical data of immune checkpoint inhibitors in glioblastoma as well as the impact glucocorticoids have on immune checkpoint inhibitor efficacy. Finally, we highlight key questions that remain in the field, and the potential benefit of further research for central nervous system tumors.

CONCLUSION

More information on the extent, character and duration of glucocorticoids on patients treated with PD-(L)1 will better inform both clinical management and novel therapeutic development of immunotherapy in patients with CNS malignancies.

Glucocorticoids potentiate the inhibitory capacity of programmed cell death 1 by up-regulating its expression on T cells

The inhibitory co-receptor programmed cell death 1 (PD-1, Pdcd1) plays critical roles in the regulation of autoimmunity, anticancer immunity, and immunity against infections. Immunotherapies targeting PD-1 have revolutionized cancer management and instigated various trials of improved cancer immunotherapies. Moreover, extensive trials are underway to potentiate PD-1 function to suppress harmful immune responses. Here we found that both natural and synthetic glucocorticoids (GCs) up-regulate PD-1 on T cells without altering the expression levels of other co-receptors and cell surface molecules. GC-induced up-regulation of PD-1 depended on transactivation of PD-1 transcription mediated through the glucocorticoid receptor. We further found that a GC response element 2525 bp upstream of the transcription start site of Pdcd1 is responsible for GC-mediated transactivation. We also observed that in vivo administration of GCs significantly up-regulates PD-1 expression on tumor-infiltrating T cells. By analyzing T cells differing in PD-1 expression, we directly demonstrated that the amount of PD-1 on the cell surface correlates with its inhibitory effect. Accordingly, GCs potentiated the capacity of PD-1 to inhibit T cell activation, suggesting that this PD-1-mediated inhibition contributes, at least in part, to the anti-inflammatory and immunosuppressive effects of GCs. In light of the critical roles of PD-1 in the regulation of autoimmunity, we expect that the potentiation of PD-1 activity may offer a promising therapeutic strategy for managing inflammatory and autoimmune diseases. Our current findings provide a rationale for strategies seeking to enhance the inhibitory effect of PD-1 by increasing its expression level.

Stress-elicited glucocorticoid receptor signaling upregulates TIGIT in innate-like invariant T lymphocytes

Stress is known to impede certain host defense mechanisms, including those governed by conventional T lymphocytes. However, whether innate-like T lymphocytes, such as invariant natural killer T (iNKT) and mucosa-associated invariant T (MAIT) cells, are impacted by stress is unclear. Herein, we report that prolonged psychological stress caused by physical confinement results in robust upregulation of T cell immunoreceptor with immunoglobulin and ITIM domains (TIGIT), an immune checkpoint receptor that controls antitumor and antiviral immune responses. Elevated TIGIT expression was found not only on NK and conventional T cells, but also on iNKT and MAIT cells. Stress-provoked TIGIT upregulation was reversed through treatment with the glucocorticoid receptor (GR) antagonist RU486, but not with 6-hydroxydopamine that induces chemical sympathectomy. A Cre/Lox gene targeting model in which GR was ablated in cells expressing Lck under its proximal promoter revealed that TIGIT upregulation in stressed animals stems from direct GR signaling in T and iNKT cells. In fact, long-term oral administration of exogenous corticosterone (CS) to wild-type C57BL/6 (B6) mice was sufficient to increase TIGIT expression levels on T and iNKT cells. In vitro treatment with CS also potently and selectively upregulated TIGIT, but not CTLA-4 or LAG-3, on mouse iNKT and MAIT hybridomas. These results were recapitulated using primary hepatic iNKT and MAIT cells from wild-type B6 and B6.MAIT^CAST mice, respectively. Subjecting B6.MAIT^CAST mice to physical restraint also raised the frequency of TIGIT⁺ cells among hepatic MAIT cells in a GR-dependent manner. Finally, we found that TIGIT is similarly upregulated in a chronic variable stress model in which animals are exposed to unpredictable heterotypic stressors without developing habituation. Taken together, our findings link, for the first time to our knowledge, GR signaling to TIGIT expression. We propose that glucocorticoid hormones dampen immune responses, in part, by enhancing TIGIT expression across multiple critical subsets of effector lymphocytes, including innate-like T cells. Therefore, TIGIT may constitute an attractive target in immune-enhancing interventions for sustained physiological stress.

Antigen-Drug Conjugates as a Novel Therapeutic Class for the Treatment of Antigen-Specific Autoimmune Disorders

Multiple sclerosis represents the world's most common cause of neurological disability in young people and is attributed to a loss of immune tolerance toward proteins of the myelin sheath. Typical treatment options for MS patients involve immunomodulatory drugs, which act nonspecifically, resulting in global immunosuppression. The study discussed herein aims to demonstrate the efficacy of antigen-specific immunotherapies involving the conjugation of disease causing autoantigen, PLP_139-151, and a potent immunosuppressant, dexamethasone. Antigen-drug conjugates (AgDCs) were formed using copper-catalyzed azide-alkyne cycloaddition chemistry with the inclusion of a hydrolyzable linker to maintain the activity of released dexamethasone. Subcutaneous administration of this antigen-drug conjugates to SJL mice induced with experimental autoimmune encephalomyelitis, protected the mice from a symptom onset throughout the 25 day study, demonstrating enhanced efficacy in comparison to dexamethasone treatment. These results highlight the benefits of co-delivery of autoantigens with immunosuppressant drugs as AgDCs for the treatment of autoimmune diseases.

Dexamethasone-induced immunosuppression: mechanisms and implications for immunotherapy

Background

Corticosteroids are routinely utilized to alleviate edema in patients with intracranial lesions and are first-line agents to combat immune-related adverse events (irAEs) that arise with immune checkpoint blockade treatment. However, it is not known if or when corticosteroids can be administered without abrogating the efforts of immunotherapy. The purpose of this study was to evaluate the impact of dexamethasone on lymphocyte activation and proliferation during checkpoint blockade to provide guidance for corticosteroid use while immunotherapy is being implemented as a cancer treatment.

Methods

Lymphocyte proliferation, differentiation, and cytokine production were evaluated during dexamethasone exposure. Human T cells were stimulated through CD3 ligation and co-stimulated either directly by CD28 ligation or by providing CD80, a shared ligand for CD28 and CTLA-4. CTLA-4 signaling was inhibited by antibody blockade using ipilimumab which has been approved for the treatment of several solid tumors. The in vivo effects of dexamethasone during checkpoint blockade were evaluated using the GL261 syngeneic mouse intracranial model, and immune populations were profiled by flow cytometry.

Results

Dexamethasone upregulated CTLA-4 mRNA and protein in CD4 and CD8 T cells and blocked CD28-mediated cell cycle entry and differentiation. Naïve T cells were most sensitive, leading to a decrease of the development of more differentiated subsets. Resistance to dexamethasone was conferred by blocking CTLA-4 or providing strong CD28 co-stimulation prior to dexamethasone exposure. CTLA-4 blockade increased IFNγ expression, but not IL-2, in stimulated human peripheral blood T cells exposed to dexamethasone. Finally, we found that CTLA-4 blockade partially rescued T cell numbers in mice bearing intracranial gliomas. CTLA-4 blockade was associated with increased IFNγ-producing tumor-infiltrating T cells and extended survival of dexamethasone-treated mice.

Conclusions

Dexamethasone-mediated T cell suppression diminishes naïve T cell proliferation and differentiation by attenuating the CD28 co-stimulatory pathway. However, CTLA-4, but not PD-1 blockade can partially prevent some of the inhibitory effects of dexamethasone on the immune response.

Electronic supplementary material

The online version of this article (10.1186/s40425-018-0371-5) contains supplementary material, which is available to authorized users.

Immunotherapies for malignant glioma

Glioblastoma multiforme (GBM) is a highly malignant primary brain cancer with a dreadful overall survival and for which treatment options are limited. Recent breakthroughs in novel immune-related treatment strategies for cancer have spurred interests in usurping the power of the patient's immune system to recognize and eliminate GBM. Here, we discuss the unique properties of GBM's tumor microenvironment, the effects of GBM standard on care therapy on tumor-associated immune cells, and review several approaches aimed at therapeutically targeting the immune system for GBM treatment. We believe that a comprehensive understanding of the intricate micro-environmental landscape of GBM will abound into the development of novel immunotherapy strategies for GBM patients.

The Role of Immune Checkpoint Inhibition in the Treatment of Brain Tumors

The standard of care for malignant gliomas of the brain has changed very little over the last few decades, and does not offer a cure for these rare, but fatal, tumors. The field of immunotherapy has brought potent new drugs into the oncological armamentarium, and is becoming recognized as a potentially important arm in the treatment of glioblastoma for adults. Immune checkpoints are inhibitory receptors found on immune cells that, when stimulated, cause those immune cells to become quiescent. While this is a natural mechanism to prevent excessive inflammatory damage and autoimmunity in otherwise healthy tissues, cancer cells may utilize this process to grow in the absence of targeted immune destruction. Antibodies derived to block the stimulation of these negative checkpoints, allowing immune cells to remain activated and undergo effector function, are a growing area of immunotherapy. These therapies have seen much success in both the preclinical and clinical arenas for various tumors, particularly melanoma and nonsmall-cell lung cancer. Multiple clinical trials are underway to determine if these drugs have efficacy in glioblastoma. Here, we review the current evidence, from early preclinical data to lessons learned from clinical trials outside of glioblastoma, to assess the potential of immune checkpoint inhibition in the treatment of brain tumors and discuss how this therapy may be implemented with the present standard of care.

Overcoming Oncogenic Mediated Tumor Immunity in Prostate Cancer

Immunotherapy is being tested intensively in clinical trials for prostate cancer; it includes immune checkpoint inhibition, prostate specific antigen (PSA) vaccines and dendritic cell-based strategies. Despite increasing evidence for clinical responses, the consensus of multiple trials is that prostate cancers are poorly responsive to immunotherapy. Prostate cancer has a high degree of pathological and genetic heterogeneity compared to other cancer types, which may account for immunotherapeutic resistance. This hypothesis also implies that select types of prostate tumors may be differentially responsive to immune-based strategies and that the clinical stage, pathological grade and underlying genetic landscape may be important criteria in identifying tumors that respond to immune therapies. One strategy is to target oncogenic driver pathways in combination with immunotherapies with the goal of overcoming tumor immunity and broadening the number of patients achieving a clinical response. In this analysis, we address the hypothesis that driver oncogenic signaling pathways regulate cancer progression, tumor immunity and resistance to current immune therapeutics in prostate cancer. We propose that increased responsiveness may be achieved through the combined use of immunotherapies and inhibitors targeting tumor cell autonomous pathways that contribute towards anti-tumor immunity in patients with prostate cancer.

miR-155: A Novel Target in Allergic Asthma

MicroRNAs (miRNAs), a class of small non-coding RNAs of 18–24 nucleotides in length, function to posttranscriptionally regulate protein expression. miR-155 was one of the first identified and, to date, the most studied miRNA, and has been linked to various cellular processes such as modulation of immune responses and oncogenesis. Previous studies have identified miR-155 as a crucial positive regulator of Th1 immune response in autoimmune diseases, but as a suppressor of Th2 immunity in allergic disorders. However, recent studies have found new evidence that miR-155 plays an indispensible role in allergic asthma. This review summarizes the recent findings with respect to miR-155 in immune responses and the underlying mechanisms responsible for miR-155-related allergic diseases, as well as the similarities between miR-155 and glucocorticoids in immunity.

Dexamethasone enhances programmed cell death 1 (PD-1) expression during T cell activation: an insight into the optimum application of glucocorticoids in anti-cancer therapy

Background

Programmed cell death 1 (PD-1) is a key cell-surface receptor of CD28 superfamily that triggers inhibitory pathways to attenuate T-cell responses and promote T-cell tolerance. As a crucial role in tumor immunity, PD-1 has been a focus of studies in anti-cancer therapy. It has been approved that tumors could exploit PD-1-dependent immune suppression for immune evasion. Considering the wide use of glucocorticoids (GCs) in anti-cancer therapy and their immunosuppressive effects, we explored whether GCs could influence the expression of PD-1.

Results

In our study, we used dexamethasone (DEX) as a model glucocorticoid and demonstrated that DEX could enhance PD-1 expression in a dose-dependent manner. The effects were completely inhibited by the glucocorticoid receptor (GR) antagonist mifepristone (RU486), indicating that the effect of DEX on PD-1 is mediated through GR. We further found the sensitivity to DEX-induced upregulation of PD-1 expression had a significant difference between different T cell subsets, with memory T cells more susceptible to this effect. We also showed that DEX could suppress T cell functions via inhibition of cytokines production such as IL-2, IFN-γ, TNF-α and induction of apoptosis of T cells.

Conclusion

Our findings suggest a novel way by which DEX suppress the function of activated T lymphocytes by enhancing expression of PD-1 and provide an insight into the optimum clinical application of GCs.

Minimal change disease: a dysregulation of the podocyte CD80-CTLA-4 axis?

BACKGROUND

Minimal Change Disease (MCD) is associated with CD80 expression in podocytes and elevated urinary CD80 excretion during active renal disease. We have evaluated the urinary excretion of CTLA-4 and CD80 during different stages of the nephrotic syndrome in patients with MCD to test the hypothesis that persistent increased urinary CD80 excretion in patients with MCD in relapse is due to an ineffectual CTLA-4 response of the host to curtail the activation of CD80.

METHODS

Thirty-two children with biopsy-proven MCD were studied during relapse and/or remission. Eleven healthy subjects served as controls.

RESULTS

Urinary CD80 excretion was significantly increased in MCD patients in relapse relative to that in MCD patients in remission (p < 0.001) and controls (p < 0.001). Although urinary CTLA-4 excretion was higher in MCD patients in relapse than in MCD patients in remission (p = 0.01) and controls (p = 0.03), no significant correlation was observed between urinary CD80 excretion and urinary CTLA-4 level in MCD patients at the time of relapse (p = 0.06). At the time of remission, CD80 had decreased significantly in all patients, but CTLA-4 levels either decreased or remained unchanged in all but five patients, and no correlation was observed between urinary CD80 excretion and CTLA-4 level (p = 0.7).

CONCLUSIONS

Urinary CTLA-4 levels do not correlate with urinary CD80 excretion, suggesting the possibility that the CTLA4 response may be suboptimal in this disease during relapse.

Myeloma skews regulatory T and pro-inflammatory T helper 17 cell balance in favor of a suppressive state

Abstract Discrepancies in the literature between regulatory T cell (Treg) and pro-inflammatory T helper 17 (Th17) numbers in multiple myeloma (MM) can be largely explained by technical differences in methodology and patient selection. In this study, Treg cells were defined as CD3(+)CD4(+)CD25(++)CD127(lo) cells. Patients with MM (n = 20) had a significant imbalance in Treg/Th17 ratio when compared with either aged-matched controls (n = 28) or other monoclonal gammopathies, and this was associated with a significantly worse survival. The percent Treg in bone marrow of patients with MM was higher than that in matched peripheral blood samples (p = 0.02), although FOXP3 expression within bone marrow T cells was lower (p = 0.02). We observed increased Treg function, both in vivo and in vitro, due at least partially to an increase in CTLA-4 expression by concurrent treatment with dexamethasone and immune modulatory compounds (iMiDs). We suggest that immunoregulatory balance is important during active chemotherapy and that conclusions related to the immunostimulatory effect of iMiDs based on in vitro testing must be considered with caution.

Peritoneal damage: the inflammatory response and clinical implications of the neuro-immuno-humoral axis

BACKGROUND

The peritoneum is a bilayer serous membrane that lines the abdominal cavity. We present a review of peritoneal structure and physiology, with a focus on the peritoneal inflammatory response to surgical injury and its clinical implications.

METHODS

We conducted a nonsystematic clinical review. A search of the Ovid MEDLINE database from 1950 through January 2009 was performed using the following search terms: peritoneum, adhesions, cytokine, inflammation, and surgery.

RESULTS

The peritoneum is a metabolically active organ, responding to insult through a complex array of immunologic and inflammatory cascades. This response increases with the duration and extent of injury and is central to the concept of surgical stress, manifesting via a combination of systemic effects, and local neural pathways via the neuro-immuno-humoral axis. There may be a decreased systemic inflammatory response after minimally invasive surgery; however, it is unclear whether this is due to a reduced local peritoneal reaction.

CONCLUSIONS

Interventions that dampen the peritoneal response and/or block the neuro-immuno-humoral pathway should be further investigated as possible avenues of enhancing recovery after surgery, and reducing postoperative complications.

Immune tolerance induction by integrating innate and adaptive immune regulators

A diversity of immune tolerance mechanisms have evolved to protect normal tissues from immune damage. Immune regulatory cells are critical contributors to peripheral tolerance. These regulatory cells, exemplified by the CD4(+)Foxp3(+) regulatory T (Treg) cells and a recently identified population named myeloid-derived suppressor cells (MDSCs), regulate immune responses and limiting immune-mediated pathology. In a chronic inflammatory setting, such as allograft-directed immunity, there may be a dynamic "cross-talk" between the innate and adaptive immunomodulatory mechanisms for an integrated control of immune damage. CTLA4-B7-based interaction between the two branches may function as a molecular "bridge" to facilitate such "cross-talk." Understanding the interplays among Treg cells, innate suppressors, and pathogenic effector T (Teff) cells will be critical in the future to assist in the development of therapeutic strategies to enhance and synergize physiological immunosuppressive elements in the innate and adaptive immune system. Successful development of localized strategies of regulatory cell therapies could circumvent the requirement for very high number of cells and decrease the risks associated with systemic immunosuppression. To realize the potential of innate and adaptive immune regulators for the still elusive goal of immune tolerance induction, adoptive cell therapies may also need to be coupled with agents enhancing endogenous tolerance mechanisms.

Effects of inhaled fluticasone propionate on CTLA-4-positive CD4+CD25+ cells in induced sputum in mild asthmatics

BACKGROUND AND OBJECTIVE

Cytotoxic T-lymphocyte antigen 4 (CTLA-4) signalling of regulatory T cells regulates mucosal lymphocyte tolerance and differentiation, and may therefore have a beneficial effect in allergic diseases such as asthma. The aim of this study was to evaluate the effects of fluticasone propionate (FP) on CD4+CD25+ T cell co-expression of CTLA-4 in the sputum of mild asthmatic subjects.

METHODS

Eleven mild, stable asthmatic subjects completed a double-blind, randomized, crossover, placebo-controlled study to compare the effects of 14 days 200 microg twice daily FP and placebo. Before and after treatment, airway hyperresponsiveness was measured, and sputum was induced for measurements of CTLA-4+CD4+CD25+ cells, eosinophils and levels of IL-10, IL-13 and transforming growth factor (TGF)-beta.

RESULTS

FP treatment increased co-expression of CTLA-4 on sputum CD4+CD25+ cells from a mean (SEM) of 7.9% (1.8) to 12.7% (3.3) after 14 days treatment (P < 0.05) compared with placebo. FP treatment also significantly increased IL-10 levels, reduced per cent sputum eosinophils, and reduced airway hyperresponsiveness (P < 0.05). There was a significant negative correlation between the change in airway hyperresponsiveness and per cent sputum eosinophils (P < 0.01), but no correlation with changes in CTLA-4+CD4+CD25+ cells (P > 0.05). There was no change in the levels of sputum IL-13 or TGF-beta.

CONCLUSIONS

The percentage of airway CTLA-4+CD4+CD25+ cells increased after FP treatment, coincident with improvements in airway inflammation and hyperresponsiveness.Whether improved asthma assessments are related to the increase in CTLA-4+CD4+CD25+ cells and thus improved regulation of T-cell tolerance and differentiation will require a larger sample size to determine. The normalization of CTLA-4+CD4+CD25+ cells in asthma may contribute to the management of this disease.

Differential response of murine CD4+CD25+and CD4+CD25-T cells to dexamethasone-induced cell death

To evaluate the in vivo effect of immunosuppressive glucocorticoids on CD4+CD25+ T regulatory cells, we injected dexamethasone (Dex) into BALB/c mice. Administration of Dex enhanced the proportion of CD4+CD25+ cells and the ratio of CD4+CD25+ cells to CD4+CD25- cells in the lymphoid organs, especially in the thymus. This correlates with our in vitro observation that CD4+CD25+ T cells express higher levels of glucocorticoid receptor and Bcl-2, and are therefore more resistant to Dex-mediated cell death than CD4+CD25- T cells. Furthermore, IL-2 selectively protected CD4+CD25+ T cells from Dex-induced cell death, while IL-7 and IL-15 did not exert preferential protective effects. Dex-treated CD4+CD25+ T cells expressed higher levels of intracellular CTLA-4 and surface glucocorticoid-induced TNF receptor than fresh CD4+CD25+ T cells, but still failed to respond to TCR stimulation and inhibited proliferation of CD4+CD25- T cells. These results suggest that, in addition to suppressing cytokine transcription, Dex treatment is permissive for the survival of functional CD4+CD25+ T regulatory cells, and this property may contribute to the anti-inflammatory and immunosuppressive efficacy of glucocorticoids. Our data also suggest that selective protection of CD4+CD25+ T cell from apoptosis may constitute a role in immune tolerance for IL-2.

On radiation hormesis expressed in the immune system

Radiation hormesis is reviewed with emphasis on its expression in the immune system. The shape of the dose-response relationship of the immune functions depends on a number of factors, chiefly the target cell under study, experimental design with emphasis on the dose range, dose spacing, dose rate and temporal changes, as well as the animal strain. For mouse and human T lymphocyte functions in the dose range of 0.01 to 10 Gy a J or inverted J-shaped curve is usually observed. For the more radioresistant macrophages, stimulation of many of their functions is often observed in the dose range up to a few grays. The cellular and molecular mechanisms of the enhancement of immunity induced by low-dose radiation were analyzed on the basis of literature published in the last decade of the past century. Intercellular reactions among the APCs and lymphocytes via distinct changes in expression of relevant surface molecules and secretion of regulatory cytokines in response to different doses of radiation were described. The major signal transduction pathways activated in response to these intercellular reactions were illustrated. The suppressive effect of low-dose radiation on cancer induction, growth, and metastasis and its immunologic mechanisms were analyzed. The present status of research in this field gives strong support to radiation hormesis in immunity with low-dose radiation as one of the mechanisms of cancer surveillance. Further research with new techniques using microarray with biochips to fully elucidate the molecular mechanisms is suggested.

Regulation of surface and intracellular expression of CTLA-4 on human peripheral T cells

Cytotoxic T-lymphocyte-associated antigen (CTLA-4) is an important downregulator of T-cell activation. In order to analyze the expression and regulation of CTLA-4 on human peripheral T cells, CTLA-4 mRNA and protein expression were determined using analysis by reverse transcription-polymerase chain reaction (RT-PCR) and FACs, respectively. Intracellular CTLA-4 was constitutively expressed in unstimulated CD4+ and CD8+ T cells. Interleukin (IL)-2 induced a dose-dependent increase of both intracellular and surface expression of CTLA-4 (CD152). Most of the CD4+ and CD8+ cells expressing CTLA-4 also expressed CD25. Interferon (IFN)-gamma induced the upregulation of CTLA-4 expression via antigen-presenting cells (APC) activation. The CTLA-4delTM mRNA (550 bp) had a shorter half-life than the full length CTLA-4 mRNA and the expression was downregulated upon activation of the cells by treatment with IL-2. Given an inhibitory role of CTLA-4 and CD4+ CD25+ T cells in immune responses, the present findings suggest that IL-2-induced immunosuppression may result from its stimulatory effect of the CTLA-4 expression.

Role of CD28/B7 costimulation and IL-12/IL-10 interaction in the radiation-induced immune changes

BACKGROUND

The present paper aims at studying the role of B7/CD28 interaction and related cytokine production in the immunological changes after exposure to different doses of ionizing radiation.

RESULTS

The stimulatory effect of low dose radiation (LDR) on the proliferative response of lymphocytes to Con A was found to require the presence of APCs. The addition of APCs obtained from both low- and high-dose-irradiated mice to splenic lymphocytes separated from low-dose-irradiated mice caused stimulation of lymphocyte proliferation. B7-1/2 expression on APCs was up-regulated after both low and high doses of radiation. There was up-regulation of CD28 expression on splenic and thymic lymphocytes after LDR and its suppression after high dose radiation (HDR), and cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) expression showed changes in the opposite direction. IL-12 secretion by macrophages was stimulated after both low and high doses of radiation, but IL-10 synthesis by splenocytes was suppressed by low dose radiation and up-regulated by high dose radiation.

CONCLUSION

The status of CD28/CTLA-4 expression on T lymphocytes in the presence of up-regulated B7 expression on APCs determined the outcome of the immune changes in response to radiation, i.e., up-regulation of CD28 after LDR resulted in immunoenhancement, and up-regulation of CTLA-4 associated with down-regulation of CD28 after HDR led to immunosuppression. Both low and high doses of radiation up-regulated B7-1/2 expression on APCs. After LDR, the stimulated proliferative effect of increased IL-12 secretion by APCs, reinforced by the suppressed secretion of IL-10, further strengthened the intracellular signaling induced by B7-CD28 interaction.