Decitabine induces regulatory T cells, inhibits the production of IFN-gamma and IL-17 and exerts preventive and therapeutic efficacy in rodent experimental autoimmune neuritis

The potential for treg-enhancing therapies in nervous system pathologies

While inflammation may not be the cause of disease, it is well known that it contributes to disease pathogenesis across a multitude of peripheral and central nervous system disorders. Chronic and overactive inflammation due to an effector T-cell-mediated aberrant immune response ultimately leads to tissue damage and neuronal cell death. To counteract peripheral and neuroinflammatory responses, research is being focused on regulatory T cell enhancement as a therapeutic target. Regulatory T cells are an immunosuppressive subpopulation of CD4+ T helper cells essential for maintaining immune homeostasis. The cells play pivotal roles in suppressing immune responses to maintain immune tolerance. In so doing, they control T cell proliferation and pro-inflammatory cytokine production curtailing autoimmunity and inflammation. For nervous system pathologies, Treg are known to affect the onset and tempo of neural injuries. To this end, we review recent findings supporting Treg's role in disease, as well as serving as a therapeutic agent in multiple sclerosis, myasthenia gravis, Guillain-Barre syndrome, Parkinson's and Alzheimer's diseases, and amyotrophic lateral sclerosis. An ever-broader role for Treg in the control of neurologic disease has been shown for traumatic brain injury, stroke, neurotrophic pain, epilepsy, and psychiatric disorders. To such ends, this review serves to examine the role played by Tregs in nervous system diseases with a focus on harnessing their functional therapeutic role(s).

Augmenting chemotherapy with low-dose decitabine through an immune-independent mechanism

The DNA methyltransferase inhibitor decitabine has classically been used to reactivate silenced genes and as a pretreatment for anticancer therapies. In a variation of this idea, this study explores the concept of adding low-dose decitabine (DAC) following administration of chemotherapy to bolster therapeutic efficacy. We find that addition of DAC following treatment with the chemotherapy agent gemcitabine improves survival and slows tumor growth in a mouse model of high-grade sarcoma. Unlike prior studies in epithelial tumor models, DAC did not induce a robust antitumor T cell response in sarcoma. Furthermore, DAC synergizes with gemcitabine independently of the immune system. Mechanistic analyses demonstrate that the combination therapy induces biphasic cell cycle arrest and apoptosis. Therapeutic efficacy was sequence dependent, with gemcitabine priming cells for treatment with DAC through inhibition of ribonucleotide reductase. This study identifies an apparently unique application of DAC to augment the cytotoxic effects of conventional chemotherapy in an immune-independent manner. The concepts explored in this study represent a promising paradigm for cancer treatment by augmenting chemotherapy through addition of DAC to increase tolerability and improve patient response. These findings have widespread implications for the treatment of sarcomas and other aggressive malignancies.

Low-dose decitabine modulates T-cell homeostasis and restores immune tolerance in immune thrombocytopenia

Our previous clinical study showed that low-dose decitabine exhibited sustained responses in nearly half of patients with refractory immune thrombocytopenia (ITP). The long-term efficacy of decitabine in ITP is not likely due to its simple role in increasing platelet production. Whether decitabine has the potential to restore immune tolerance in ITP is unknown. In this study, we analyzed the effect of decitabine on T-cell subpopulations in ITP in vitro and in vivo. We found that low-dose decitabine promoted the generation and differentiation of regulatory T (Treg) cells and augmented their immunosuppressive function. Splenocytes from CD61 knockout mice immunized with CD61+ platelets were transferred into severe combined immunodeficient mouse recipients to induce a murine model of ITP. Low-dose decitabine alleviated thrombocytopenia and restored the balance between Treg and helper T (Th) cells in active ITP mice. Treg deletion and depletion offset the effect of decitabine in restoring CD4+ T-cell subpopulations in ITP mice. For patients who received low-dose decitabine, the quantity and function of Treg cells were substantially improved, whereas Th1 and Th17 cells were suppressed compared with the pretreatment levels. Next-generation RNA-sequencing and cytokine analysis showed that low-dose decitabine rebalanced T-cell homeostasis, decreased proinflammatory cytokines, and downregulated phosphorylated STAT3 in patients with ITP. STAT3 inhibition analysis suggested that low-dose decitabine might restore Treg cells by inhibiting STAT3 activation. In conclusion, our data indicate that the immunomodulatory effect of decitabine provides one possible mechanistic explanation for the sustained response achieved by low-dose decitabine in ITP.

Hypomethylating agents (HMA) for the treatment of acute myeloid leukemia and myelodysplastic syndromes: mechanisms of resistance and novel HMA-based therapies

Aberrant DNA methylation plays a pivotal role in tumor development and progression. DNA hypomethylating agents (HMA) constitute a class of drugs which are able to reverse DNA methylation, thereby triggering the re-programming of tumor cells. The first-generation HMA azacitidine and decitabine have now been in standard clinical use for some time, offering a valuable alternative to previous treatments in acute myeloid leukemia and myelodysplastic syndromes, so far particularly in older, medically non-fit patients. However, the longer we use these drugs, the more we are confronted with the (almost inevitable) development of resistance. This review provides insights into the mode of action of HMA, mechanisms of resistance to this treatment, and strategies to overcome HMA resistance including next-generation HMA and HMA-based combination therapies.

Altered Expression of TSPAN32 during B Cell Activation and Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a chronic inflammatory disease with various clinical features. Autoreactive B cells play a role in disease pathogenesis, through the production of multiple autoantibodies, which form immune complexes and induce the inflammatory response and tissue damage associated with SLE. Recently, tetraspanins, and in particular, TSPAN32, have been recognized to play a central role in immunity, as they are involved in various biological processes, such as the antigen presentation and the activation of lymphocytes. Evidence suggests that tetraspanins could represent in the future a target for therapeutic purposes in patients suffering from autoimmune/immunoinflammatory disorders. In the present study, by performing in silico analyses of high-throughput data, we evaluated the expression levels of TSPAN32 in B cell activation and investigated its modulation in circulating B cells from SLE patients. Our data show that B cell activation is associated with a significant downregulation of TSPAN32. Additionally, significantly lower levels of TSPAN32 were observed in circulating plasmablasts from SLE patients as compared to healthy donor plasmablasts. In addition, type I interferons (IFNs)-related genes were enriched among the genes negatively correlated to TSPAN32, in SLE plasmablasts. Accordingly, IFN-α is able to induce a dose-dependent downregulation of TSPAN32 in B cells. Overall, the data here presented suggest the potential use of TSPAN32 as a diagnostic marker and therapeutic target for the evaluation and management of humoral immune responses in chronic diseases, such as SLE.

Epigenetic DNA Methylation of EBI3 Modulates Human Interleukin-35 Formation via NFkB Signaling: A Promising Therapeutic Option in Ulcerative Colitis

Ulcerative colitis (UC), a severe chronic disease with unclear etiology that is associated with increased risk for colorectal cancer, is accompanied by dysregulation of cytokines. Epstein–Barr virus-induced gene 3 (EBI3) encodes a subunit in the unique heterodimeric IL-12 cytokine family of either pro- or anti-inflammatory function. After having recently demonstrated that upregulation of EBI3 by histone acetylation alleviates disease symptoms in a dextran sulfate sodium (DSS)-treated mouse model of chronic colitis, we now aimed to examine a possible further epigenetic regulation of EBI3 by DNA methylation under inflammatory conditions. Treatment with the DNA methyltransferase inhibitor (DNMTi) decitabine (DAC) and TNFα led to synergistic upregulation of EBI3 in human colon epithelial cells (HCEC). Use of different signaling pathway inhibitors indicated NFκB signaling was necessary and proportional to the synergistic EBI3 induction. MALDI-TOF/MS and HPLC-ESI-MS/MS analysis of DAC/TNFα-treated HCEC identified IL-12p35 as the most probable binding partner to form a functional protein. EBI3/IL-12p35 heterodimers (IL-35) induce their own gene upregulation, something that was indeed observed in HCEC cultured with media from previously DAC/TNFα-treated HCEC. These results suggest that under inflammatory and demethylating conditions the upregulation of EBI3 results in the formation of anti-inflammatory IL-35, which might be considered as a therapeutic target in colitis.

Decitabine Promotes Modulation in Phenotype and Function of Monocytes and Macrophages That Drive Immune Response Regulation

Decitabine is an approved hypomethylating agent used for treating hematological malignancies. Although decitabine targets altered cells, epidrugs can trigger immunomodulatory effects, reinforcing the hypothesis of immunoregulation in treated patients. We therefore aimed to evaluate the impact of decitabine treatment on the phenotype and functions of monocytes and macrophages, which are pivotal cells of the innate immunity system. In vitro decitabine administration increased bacterial phagocytosis and IL-8 release, but impaired microbicidal activity of monocytes. In addition, during monocyte-to-macrophage differentiation, treatment promoted the M2-like profile, with increased expression of CD206 and ALOX15. Macrophages also demonstrated reduced infection control when exposed to Mycobacterium tuberculosis in vitro. However, cytokine production remained unchanged, indicating an atypical M2 macrophage. Furthermore, when macrophages were cocultured with lymphocytes, decitabine induced a reduction in the release of inflammatory cytokines such as IL-1β, TNF-α, and IFN-γ, maintaining IL-10 production, suggesting that decitabine could potentialize M2 polarization and might be considered as a therapeutic against the exacerbated immune response.

Immune responses to azacytidine in animal models of inflammatory disorders: a systematic review

Inflammatory disorders like diabetes, systemic lupus erythematodes, inflammatory lung diseases, rheumatoid arthritis and multiple sclerosis, but also rejection of transplanted organs and GvHD, form a major burden of disease. Current classes of immune suppressive drugs to treat these disorders are never curative and side effects are common. Therefore there is a need for new drugs with improved and more targeted modes of action. Potential candidates are the DNA methyl transferase inhibitor 5-azacytidine (Aza) and its derivative 5-aza 2′deoxycitidine (DAC). Aza and DAC have been tested in several pre-clinical in vivo studies. In order to obtain an overview of disorders for which Aza and/or DAC can be a potential treatment, and to find out where information is lacking, we systematically reviewed pre-clinical animal studies assessing Aza or DAC as a potential therapy for distinct inflammatory disorders. Also, study quality and risk of bias was systematically assessed. In the 35 identified studies, we show that both Aza and DAC do not only seem to be able to alleviate a number of inflammatory disorders, but also prevent solid organ rejection and GvHD in in vivo pre-clinical animal models. Aza/DAC are known to upregulate FOXP3, a master transcription factor for Treg, in vitro. Seventeen studies described the effect on Treg, of which 16 studies showed an increase in Treg. Increasing Treg therefore seems to be a common mechanism in preventing inflammatory disorders by Aza/DAC. We also found, however, that many essential methodological details were poorly reported leading to an unclear risk of bias. Therefore, reported effects might be an overestimation of the true effect.

Epigenetic inhibitors eliminate senescent melanoma BRAFV600E cells that survive long‑term BRAF inhibition

It is estimated that ~50% of patients with melanoma harbour B‑Raf (BRAF)V600 driver mutations, with the most common of these being BRAFV600E, which leads to the activation of mitogen‑activated protein kinase proliferative and survival pathways. BRAF inhibitors are used extensively to treat BRAF‑mutated metastatic melanoma; however, acquired resistance occurs in the majority of patients. The effects of long‑term treatment with PLX4032 (BRAFV600 inhibitor) were studied in vitro on sensitive V600E BRAF‑mutated melanoma cell lines. After several weeks of treatment with PLX4032, the majority of the melanoma cells died; however, a proportion of cells remained viable and quiescent, presenting senescent cancer stem cell‑like characteristics. This surviving population was termed SUR cells, as discontinuing treatment allowed the population to regrow while retaining equal drug sensitivity to that of parental cells. RNA sequencing analysis revealed that SUR cells exhibit changes in the expression of 1,415 genes (P<0.05) compared with parental cells. Changes in the expression levels of a number of epigenetic regulators were also observed. These changes and the reversible nature of the senescence state were consistent with epigenetic regulation; thus, it was investigated as to whether the senescent state could be reversed by epigenetic inhibitors. It was found that both parental and SUR cells were sensitive to different histone deacetylase (HDAC) inhibitors, such as SAHA and MGCD0103, and to the cyclin‑dependent kinase (CDK)9 inhibitor, CDKI‑73, which induced apoptosis and reduced proliferation both in the parental and SUR populations. The results suggested that the combination of PLX4032 with HDAC and CDK9 inhibitors may achieve complete elimination of SUR cells that persist after BRAF inhibitor treatment, and reduce the development of resistance to BRAF inhibitors.

Effects of Treatment with the Hypomethylating Agent 5-aza-2'-deoxycytidine in Murine Type II Collagen-Induced Arthritis

The emerging role of epigenetics in the pathogenesis of autoimmune diseases has recently attracted much interest on the possible use of epigenetic modulators for the prevention and treatment of these diseases. In particular, we and others have shown that drugs that inhibit DNA methylation, such as azacitidine (AZA) and decitabine (DAC), already used for the treatment of acute myeloid leukemia, exert powerful beneficial effects in rodent models of type 1 diabetes, multiple sclerosis, and Guillain Barrè syndrome. Along this line of research, we have presently studied the effects of DAC in a murine model of rheumatoid arthritis induced by type II collagen and have demonstrated that DAC administration was associated with a significant amelioration of the clinical condition, along with in vivo and ex vivo modification of the immunological profile of the so-treated mice, that exhibited a diminished production of Th1 and Th17 pro-inflammatory cytokines and reduction of anti-type II collagen autoantibodies.

Overexpression of Macrophage Migration Inhibitory Factor and Its Homologue D-Dopachrome Tautomerase as Negative Prognostic Factor in Neuroblastoma

Neuroblastoma (NB) represents one of the most frequent pediatric solid tumors. Macrophage migration inhibitory factor (MIF) is a cytokine exerting multiple biological functions. More recently, a second member of the MIF family of cytokine has been identified, the D-dopachrome tautomerase (DDT), that exerts several overlapping functions with MIF. Growing evidence suggests a key role for MIF and DDT in the development of cancer. The aim of this study is to characterize the prognostic value of MIF and DDT in NB. We show that higher expression levels of MIF and DDT in Stage 4 NB samples are associated with a poorer prognosis, independently of the presence of MYCN amplification. Moreover, higher levels of MIF are mostly enriched by Th1 cells, while lower levels of MIF are associated with an increased proportion of B cells, Cytotoxic T cells, Dendritic cells and Natural Killer T cells. We also show that treatment with the histone deacetylase (HDAC) inhibitor, vorinostat, of the NB cell line, SH-SY5Y, determines a significant reduction in the expression of both MIF and DDT. Finally, MIF and DDT inhibition by short interfering RNA is able to revert vincristine sensitivity in vitro. Overall, our data suggest that MIF exert pro-tumorigenic properties in NB, likely by dampening antigen presentation and cytotoxic immune responses, and we propose the HDAC inhibitors as a potential therapeutic strategy for NB patients.