Bmi1 regulates memory CD4 T cell survival via repression of the Noxa gene

The BCL2 family: from apoptosis mechanisms to new advances in targeted therapy

The B cell lymphoma 2 (BCL2) protein family critically controls apoptosis by regulating the release of cytochrome c from mitochondria. In this cutting-edge review, we summarize the basic biology regulating the BCL2 family including canonical and non-canonical functions, and highlight milestones from basic research to clinical applications in cancer and other pathophysiological conditions. We review laboratory and clinical development of BH3-mimetics as well as more recent approaches including proteolysis targeting chimeras (PROTACs), antibody-drug conjugates (ADCs) and tools targeting the BH4 domain of BCL2. The first BCL2-selective BH3-mimetic, venetoclax, showed remarkable efficacy with manageable toxicities and has transformed the treatment of several hematologic malignancies. Following its success, several chemically similar BCL2 inhibitors such as sonrotoclax and lisaftoclax are currently under clinical evaluation, alone and in combination. Genetic analysis highlights the importance of BCL-XL and MCL1 across different cancer types and the possible utility of BH3-mimetics targeting these proteins. However, the development of BH3-mimetics targeting BCL-XL or MCL1 has been more challenging, with on-target toxicities including thrombocytopenia for BCL-XL and cardiac toxicities for MCL1 inhibitors precluding clinical development. Tumor-specific BCL-XL or MCL1 inhibition may be achieved by novel targeting approaches using PROTACs or selective drug delivery strategies and would be transformational in many subtypes of malignancy. Taken together, we envision that the targeting of BCL2 proteins, while already a success story of translational research, may in the foreseeable future have broader clinical applicability and improve the treatment of multiple diseases.

BMI1-induced CD127+KLRG1+ memory T cells enhance the efficacy of liver cancer immunotherapy

The efficacy of HCC (hepatocellular carcinoma) immunotherapy is hindered by the limited reactivity and short duration of tumor-infiltrating T cells. These deficiencies may be ascribed to the proliferative ability of T cells. The primary objective of this study was to identify the key factor regulating tumor-infiltrating lymphocytes (TIL) proliferation within the HCC microenvironment. Through the utilization of tissue-infiltrated T cell proteomics and fraction proteomics, we analyzed the differential proteins in T cells among HCC, liver fibrosis, and hemangioma (serving as controls) groups. Additionally, we examined the differential regulatory TFs of T cells between the HCC and VH (volunteer healthy, as a control) groups. Using cyTOF and flow cytometry technologies, as well as generating CD8+ T-specific BMI1 knockout mice, we confirmed that BMI1 controls CD127+KLRG1+ memory cell differentiation. Through RNA-seq and MeRIP-seq, we verified that BMI1 regulates TCF1 expression independently of its classical function. Furthermore, by conducting Tyramide signal amplification (TSA) IHC analysis, employing a hydrodynamic mouse HCC model, and utilizing liver-specific nanoparticle targeting therapy, we demonstrated that BMI1 in HCC influences the proliferation of infiltrating CD8+T. BMI1 inhibition promotes effector T cell differentiation while suppressing memory T cell differentiation. Moreover, liver-specific BMI1 knockdown proves beneficial in ameliorating T cell dysfunction and decelerating HCC progression. Our research group has pioneered the exploration of the proteomics of HCC-infiltrated T cells, shedding light on the pivotal role of BMI1 in controlling CD127+KLRG1+ memory CD8+ T cell differentiation, which serves as the cornerstone for achieving immunotherapy efficacy in HCC.

Pituitary adenomas evade apoptosis via noxa deregulation in Cushing's disease

Sporadic pituitary adenomas occur in over 10% of the population. Hormone-secreting adenomas, including those causing Cushing’s disease (CD), cause severe morbidity and early mortality. Mechanistic studies of CD are hindered by a lack of in vitro models and control normal human pituitary glands. Here, we surgically annotate adenomas and adjacent normal glands in 25 of 34 patients. Using single-cell RNA sequencing (RNA-seq) analysis of 27594 cells, we identify CD adenoma transcriptomic signatures compared with adjacent normal cells, with validation by bulk RNA-seq, DNA methylation, qRT-PCR, and immunohistochemistry. CD adenoma cells include a subpopulation of proliferating, terminally differentiated corticotrophs. In CD adenomas, we find recurrent promoter hypomethylation and transcriptional upregulation of PMAIP1 (encoding pro-apoptotic BH3-only bcl-2 protein noxa) but paradoxical noxa downregulation. Using primary CD adenoma cell cultures and a corticotroph-enriched mouse cell line, we find that selective proteasomal inhibition with bortezomib stabilizes noxa and induces apoptosis, indicating its utility as an anti-tumor agent.

Asuzu et al. perform single-cell transcriptomic profiling in Cushing’s disease (CD) adenomas and find overexpression and DNA hypomethylation of PMAIP1, which encodes the pro-apoptotic protein noxa. Noxa is degraded by the proteasome. Proteasomal inhibition rescues noxa and induces apoptosis in CD.

The Crucial Roles of Bmi-1 in Cancer: Implications in Pathogenesis, Metastasis, Drug Resistance, and Targeted Therapies

B-cell-specific Moloney murine leukemia virus integration region 1 (Bmi-1, also known as RNF51 or PCGF4) is one of the important members of the PcG gene family, and is involved in regulating cell proliferation, differentiation and senescence, and maintaining the self-renewal of stem cells. Many studies in recent years have emphasized the role of Bmi-1 in the occurrence and development of tumors. In fact, Bmi-1 has multiple functions in cancer biology and is closely related to many classical molecules, including Akt, c-MYC, Pten, etc. This review summarizes the regulatory mechanisms of Bmi-1 in multiple pathways, and the interaction of Bmi-1 with noncoding RNAs. In particular, we focus on the pathological processes of Bmi-1 in cancer, and explore the clinical relevance of Bmi-1 in cancer biomarkers and prognosis, as well as its implications for chemoresistance and radioresistance. In conclusion, we summarize the role of Bmi-1 in tumor progression, reveal the pathophysiological process and molecular mechanism of Bmi-1 in tumors, and provide useful information for tumor diagnosis, treatment, and prognosis.

Targeting BMI-1 in B cells restores effective humoral immune responses and controls chronic viral infection

Ineffective antibody-mediated responses are a key characteristic of chronic viral infection. However, our understanding of the intrinsic mechanisms that drive this dysregulation are unclear. Here, we identify that targeting the epigenetic modifier BMI-1 in mice improves humoral responses to chronic lymphocytic choriomeningitis virus. BMI-1 was upregulated by germinal center B cells in chronic viral infection, correlating with changes to the accessible chromatin landscape, compared to acute infection. B cell-intrinsic deletion of Bmi1 accelerated viral clearance, reduced splenomegaly and restored splenic architecture. Deletion of Bmi1 restored c-Myc expression in B cells, concomitant with improved quality of antibody and coupled with reduced antibody-secreting cell numbers. Specifically, BMI-1-deficiency induced antibody with increased neutralizing capacity and enhanced antibody-dependent effector function. Using a small molecule inhibitor to murine BMI-1, we could deplete antibody-secreting cells and prohibit detrimental immune complex formation in vivo. This study defines BMI-1 as a crucial immune modifier that controls antibody-mediated responses in chronic infection.

Signaling Pathways That Control Apoptosis in Prostate Cancer

Prostate cancer is the second most common malignancy and the fifth leading cancer-caused death in men worldwide. Therapies that target the androgen receptor axis induce apoptosis in normal prostates and provide temporary relief for advanced disease, yet prostate cancer that acquired androgen independence (so called castration-resistant prostate cancer, CRPC) invariably progresses to lethal disease. There is accumulating evidence that androgen receptor signaling do not regulate apoptosis and proliferation in prostate epithelial cells in a cell-autonomous fashion. Instead, androgen receptor activation in stroma compartments induces expression of unknown paracrine factors that maintain homeostasis of the prostate epithelium. This paradigm calls for new studies to identify paracrine factors and signaling pathways that control the survival of normal epithelial cells and to determine which apoptosis regulatory molecules are targeted by these pathways. This review summarizes the recent progress in understanding the mechanism of apoptosis induced by androgen ablation in prostate epithelial cells with emphasis on the roles of BCL-2 family proteins and "druggable" signaling pathways that control these proteins. A summary of the clinical trials of inhibitors of anti-apoptotic signaling pathways is also provided. Evidently, better knowledge of the apoptosis regulation in prostate epithelial cells is needed to understand mechanisms of androgen-independence and implement life-extending therapies for CRPC.

Structural heterogeneity of the mammalian polycomb repressor complex in immune regulation

Epigenetic regulation is mainly mediated by enzymes that can modify the structure of chromatin by altering the structure of DNA or histones. Proteins involved in epigenetic processes have been identified to study the detailed molecular mechanisms involved in the regulation of specific mRNA expression. Evolutionarily well-conserved polycomb group (PcG) proteins can function as transcriptional repressors by the trimethylation of histone H3 at the lysine 27 residue (H3K27me3) and the monoubiquitination of histone H2A at the lysine 119 residue (H2AK119ub). PcG proteins form two functionally distinct protein complexes: polycomb repressor complex 1 (PRC1) and PRC2. In mammals, the structural heterogeneity of each PRC complex is dramatically increased by several paralogs of its subunit proteins. Genetic studies with transgenic mice along with RNA-seq and chromatin immunoprecipitation (ChIP)-seq analyses might be helpful for defining the cell-specific functions of paralogs of PcG proteins. Here, we summarize current knowledge about the immune regulatory role of PcG proteins related to the compositional diversity of each PRC complex and introduce therapeutic drugs that target PcG proteins in hematopoietic malignancy.

Protein complexes that suppress gene activity by remodeling chromatin, the substance that contains most of a cell’s DNA, play a critical role in regulating the immune system and provide a therapeutic target for treating blood cancers. Seok-Jin Kang and Taehoon Chun from Korea University in Seoul, South Korea, review how polycomb group proteins, best known for their function in embryonic development, also contribute to the formation of immune cells from blood stem cell precursors. Studies with stem cells and cancer cells have begun to reveal many targets of these proteins, and drug companies are evaluating candidate agents directed against some polycomb group proteins in patients with lymphoma and other cancers. More comprehensive profiling of protein function across a broad range of immune cell types could reveal new targets for additional diseases associated with immune dysfunction.

Resveratrol modulates epigenetic regulators of promoter histone methylation and acetylation that restores BRCA1, p53, p21CIP1 in human breast cancer cell lines

The epigenetic enzymes catalyze posttranslational modifications (PTMs) of histones, which functionally determine gene expression at the chromatin level. Resveratrol (RVT) a much studied anti-cancer natural molecule is known for restoration of BRCA1, p53, and p21 in cancer cells. We aimed to investigate the role of histone methylation and acetylation on upregulation of these tumor suppressor genes. Our results suggest RVT significantly increase expression of BRCA1, p53, and p21, while decreased expression of protein arginine methyltransferase 5 (PRMT5) and enhancer of Zeste homolog 2 (EZH2) at a 20 μM concentration by 48 hr in both MCF-7 and MDA-MB-231 breast cancer cells. Also, there was an overall loss of H4R3me2s (catalytic product of PRMT5) and H3K27me3 (catalytic product of PRMT5). In contrast, RVT exposure caused a significant decrease in lysine deacetylase (KDAC) activity and expression of KDAC1-3, whereas the expression of lysine acetyltransferase KAT2A/3B was increased compared to the unexposed cells. As an outcome, RVT increased global level of H3K9ac and H3K27ac marks. The chromatin immunoprecipitation showed 20 μM RVT exposure significantly reduced the enrichment of repressive histone marks (H4R3me2s and H3K27me3) while the abundance of activating histone marks (H3K9/27ac) within the proximal promoter region of BRCA1, p53, and p21 was increased. We hypothesize RVT by affecting the expression and function of methylation and acetylation enzymes altered the epigenetic modifications on promoter histones that restored expression of these critically important tumor suppressor genes.

Epigenetic perspectives on systemic autoimmune disease

Autoimmune diseases are characterized by increased reactivity of the immune system towards self-antigens, causing tissue damage. Although their etiology remains largely unknown, genetic, microbial, environmental and psychological factors are recognized as contributing elements. Epigenetic changes, including covalent modifications of the DNA and histones, are critical signaling mediators between the genome and the environment, and thus potent regulators of cellular functions. The most extensively studied epigenetic modifications are Cytosine DNA methylation and histone acetylation and methylation on various residues. These are thought to affect chromatin structure and binding of specific effectors that regulate transcription, replication, and other processes. Recent studies have uncovered significant epigenetic alterations in cells or tissues derived from autoimmune disease patients compared to samples from healthy individuals and have linked them with disease phenotypes. Epigenetic changes in specific genes correlate with upregulated or downregulated transcription. For instance, in many systems, reduced DNA methylation and increased histone acetylation of interferon-inducible genes correlate with their increased expression in autoimmune disease patients. Also, reduced DNA methylation of retroelements has been proposed as an activating mechanism and has been linked with increased immune reactivity, while epigenetic differences on the X chromosome could indicate incomplete dosage compensation and explain to some extent the increased susceptibility of females over males towards the development of most autoimmune diseases. Besides changes in epigenetic modifications, differences in the levels of many enzymes catalyzing the addition or removal of these marks as well as proteins that recognize them and function as effector molecules have also been detected in autoimmune patients. Although the existing knowledge cannot fully explain whether epigenetic alterations cause or follow the increased immune activation, their characterization is very useful for understanding the pathogenetic mechanisms and complements genetic and clinical studies. Furthermore, specific epigenetic marks have the potential to serve as biomarkers for disease status, prognosis, and response to treatment. Finally, epigenetic factors are currently being examined as candidate therapeutic targets.

Epigenetic mechanisms related to cognitive decline during aging

Cognitive decline is a hallmark of the aging nervous system, characterized by increasing memory loss and a deterioration of mental capacity, which in turn creates a favorable context for the development of neurodegenerative diseases. One of the most detrimental alterations that occur at the molecular level in the brain during aging is the modification of the epigenetic mechanisms that control gene expression. As a result of these epigenetic-driven changes in the transcriptome most of the functions of the brain including synaptic plasticity, learning, and memory decline with aging. The epigenetic mechanisms altered during aging include DNA methylation, histone modifications, nucleosome remodeling, and microRNA-mediated gene regulation. In this review, we examine the current evidence concerning the changes of epigenetic modifications together with the molecular mechanisms underlying impaired neuronal gene transcription during aging. Herein, we discuss the alterations of DNA methylation pattern that occur in old neurons. We will also describe the most prominent age-related histone posttranslational modifications in the brain since changes in acetylation and methylation of specific lysine residues on H3 and H4 are associated to functional decline in the old. In addition, we discuss the role that changes in the levels of certain miRNAs would play in cognitive decline with aging. Finally, we provide an overview about the mechanisms either extrinsic or intrinsic that would trigger epigenetic changes in the aging brain, and the consequences of these changes, i.e., altered transcriptional profile and reactivation of transposable elements in old brain.

The Role of Histone Methyltransferases and Long Non-coding RNAs in the Regulation of T Cell Fate Decisions

T cell lineage decisions are critical for the development of proper immune responses to pathogens as well as important for the resolution of inflammatory responses. This differentiation process relies on a combination of intrinsic and extrinsic factors converging upon epigenetic regulation of transcriptional networks relevant to specific T cell lineages. As these biochemical modifications represent therapeutic opportunities in cancer biology and autoimmunity, implications of writers and readers of epigenetic marks to immune cell differentiation and function are highly relevant. Given the ready adoption of histone methyltransferase inhibitors in the clinic, we focus this review on the role of three histone modifying complexes: PRC-1, PRC-2, and G9A in modulating T cell fate decisions. Furthermore, we explore the role of long non-coding RNAs in regulating these processes, and discuss recent advances and challenges of implementing epigenetic therapies into clinical practice.

Epigenetic and Transcriptional Regulation in the Induction, Maintenance, Heterogeneity, and Recall-Response of Effector and Memory Th2 Cells

Antigen-primed T cells respond to restimulation much faster than naïve T cells and form the cellular basis of immunological memory. The formation of memory Th2 cells starts when naïve CD4 T cells are transformed into effector Th2 cells and is completed after antigen clearance and a long-term resting phase accompanied by epigenetic changes in the Th2 signature genes. Memory Th2 cells maintain their functions and acquired heterogeneity through epigenetic machinery, on which the recall-response of memory Th2 cells is also dependent. We provide an overview of the epigenetics in the whole Th2 cell cycle, mainly focusing on two different histone lysine methyltransferase complexes: the Polycomb and Trithorax groups. We finally discuss the pathophysiology and potential therapeutic strategies for the treatment of Th2-mediated inflammatory diseases in mice and humans.

Repression of Noxa by Bmi1 contributes to deguelin-induced apoptosis in non-small cell lung cancer cells

Deguelin, a natural rotenoid isolated from several plants, has been reported to exert anti‐tumour effects in various cancers. However, the molecular mechanism of this regulation remains to be fully elucidated. Here, we found that deguelin inhibited the growth of non‐small cell lung cancer (NSCLC) cells both in vitro and in vivo by downregulation of Bmi1 expression. Our data showed that Bmi1 is highly expressed in human NSCLC tissues and cell lines. Knockdown of Bmi1 significantly suppressed NSCLC cell proliferation and colony formation. Deguelin treatment attenuated the binding activity of Bmi1 to the Noxa promoter, thus resulting in Noxa transcription and apoptosis activation. Knockdown of Bmi1 promoted Noxa expression and enhanced deguelin‐induced apoptosis, whereas overexpression of Bmi1 down‐regulated Noxa protein level and deguelin‐induced apoptosis. Overall, our study demonstrated a novel apoptotic mechanism for deguelin to exert its anti‐tumour activity in NSCLC cells.

The Transcription Factor Zfx Regulates Peripheral T Cell Self-Renewal and Proliferation

Peripheral T lymphocytes share many functional properties with hematopoietic stem cells (HSCs), including long-term maintenance, quiescence, and latent proliferative potential. In addition, peripheral T cells retain the capacity for further differentiation into a variety of subsets, much like HSCs. While the similarities between T cells and HSC have long been hypothesized, the potential common genetic regulation of HSCs and T cells has not been widely explored. We have studied the T cell-intrinsic role of Zfx, a transcription factor specifically required for HSC maintenance. We report that T cell-specific deletion of Zfx caused age-dependent depletion of naïve peripheral T cells. Zfx-deficient T cells also failed to undergo homeostatic proliferation in a lymphopenic environment, and showed impaired antigen-specific expansion and memory response. In addition, the invariant natural killer T cell compartment was severely reduced. RNA-Seq analysis revealed that the most dysregulated genes in Zfx-deficient T cells were similar to those observed in Zfx-deficient HSC and B cells. These studies identify Zfx as an important regulator of peripheral T cell maintenance and expansion and highlight the common molecular basis of HSC and lymphocyte homeostasis.

Epigenetic regulation of T-helper cell differentiation, memory, and plasticity in allergic asthma

An estimated 300 million people currently suffer from asthma, which causes approximately 250 000 deaths a year. Allergen-specific T-helper (Th) cells produce cytokines that induce many of the hallmark features of asthma including airways hyperreactivity, eosinophilic and neutrophilic inflammation, mucus hypersecretion, and airway remodeling. Cytokine-producing Th subsets including Th1 (IFN-γ), Th2 (IL-4, IL-5, IL-13), Th9 (IL-9), Th17 (IL-17), Th22 (IL-22), and T regulatory (IL-10) cells have all been suggested to play a role in the development of asthma. Th differentiation involves genetic regulation of gene expression through the concerted action of cytokines, transcription factors, and epigenetic regulators. We describe how Th differentiation and plasticity is regulated by epigenetic histone and DNA modifications, with a focus on the regulation of histone methylation by members of the polycomb and trithorax complexes. In addition, we outline environmental influences that could influence epigenetic regulation of Th cells and discuss the potential to regulate Th plasticity and function through drugs targeting the epigenetic machinery. It is also becoming apparent that epigenetic regulation of allergen-specific memory Th cells may be important in the development and persistence of chronic allergies. Finally, we describe how epigenetic modifiers regulate cytokine memory in Th cells and describe recently identified hybrid, plastic, and pathogenic memory Th subsets the context of allergic asthma.

Specific or not specific recruitment of DNMTs for DNA methylation, an epigenetic dilemma

Our current view of DNA methylation processes is strongly moving: First, even if it was generally admitted that DNMT3A and DNMT3B are associated with de novo methylation and DNMT1 is associated with inheritance DNA methylation, these distinctions are now not so clear. Secondly, since one decade, many partners of DNMTs have been involved in both the regulation of DNA methylation activity and DNMT recruitment on DNA. The high diversity of interactions and the combination of these interactions let us to subclass the different DNMT-including complexes. For example, the DNMT3L/DNMT3A complex is mainly related to de novo DNA methylation in embryonic states, whereas the DNMT1/PCNA/UHRF1 complex is required for maintaining global DNA methylation following DNA replication. On the opposite to these unspecific DNA methylation machineries (no preferential DNA sequence), some recently identified DNMT-including complexes are recruited on specific DNA sequences. The coexistence of both types of DNA methylation (un/specific) suggests a close cooperation and an orchestration between these systems to maintain genome and epigenome integrities. Deregulation of these systems can lead to pathologic disorders.

Abundant expression of BMI1 in follicular lymphoma is associated with reduced overall survival

Although generally indolent, follicular lymphoma (FL) sometimes pursues a more aggressive course leading to early death. B-cell-specific Mo-MLV insertion site-1 (BMI1) is a member of the polycomb group (PcG) proteins that confer stem cell properties through gene silencing. We used multi-channel immunofluorescence and automated image analysis to quantify BMI1 selectively in the nuclei of FL-derived B-cells in routine biopsy specimens. Applying this assay to 109 pretreatment FL biopsy samples demonstrates a significant association between abundant BMI1 and reduced overall survival (p = .001); the statistically significant association with mortality persists in a Cox proportional hazards model that includes Follicular Lymphoma International Prognostic Index (FLIPI) score, histological grade, and the presence of a component of diffuse large B-cell lymphoma in the biopsy sample. Ascertaining BMI1 over-expression may be useful in identifying patients who might benefit from novel therapies directed at reversing the chromatin-modifying functions of BMI1.

Expression of CD markers' in immune thrombocytopenic purpura: prognostic approaches

Immune Thrombocytopenic Purpura (ITP) is a common autoimmune bleeding disorder characterized by a reduction in peripheral blood platelet counts. In this disease, autoantibodies (Auto-Abs) are produced against platelet GPIIb/GPIIIa by B cells, which require interaction with T cells. In this review, the importance of B and T lymphocytes in ITP prognosis has been studied. Relevant literature was identified by a PubMed search (1990-2016) of English-language papers using the terms B and T lymphocyte, platelet, CD markers and immune thrombocytopenic purpura. T and B lymphocytes are the main immune cells in the body. Defective function causes disrupted balance of different subgroups of lymphocytes, and abnormal expression of surface markers of these cells results in self-tolerance dysfunction, as well as induction of Auto-Abs against platelet glycoproteins (PG). Given the role of B and T cells in production of autoantibodies against PG, it can be stated that the detection of changes in CD markers' expression in these cells can be a good approach for assessing prognosis in ITP patients.

Genome-wide DNA methylation and transcriptome analyses reveal genes involved in immune responses of pig peripheral blood mononuclear cells to poly I:C

DNA methylation changes play essential roles in regulating the activities of genes involved in immune responses. Understanding of variable DNA methylation linked to immune responses may contribute to identifying biologically promising epigenetic markers for pathogenesis of diseases. Here, we generated genome-wide DNA methylation and transcriptomic profiles of six pairs of polyinosinic-polycytidylic acid-treated pig peripheral blood mononuclear cell (PBMC) samples and corresponding controls using methylated DNA immunoprecipitation sequencing and RNA sequencing. Comparative methylome analyses identified 5,827 differentially methylated regions and 615 genes showing differential expression between the two groups. Integrative analyses revealed inverse associations between DNA methylation around transcriptional start site and gene expression levels. Furthermore, 70 differentially methylated and expressed genes were identified such as TNFRSF9, IDO1 and EBI3. Functional annotation revealed the enriched categories including positive regulation of immune system process and regulation of leukocyte activation. These findings demonstrated DNA methylation changes occurring in immune responses of PBMCs to poly I:C stimulation and a subset of genes potentially regulated by DNA methylation in the immune responses. The PBMC DNA methylome provides an epigenetic overview of this physiological system in response to viral infection, and we expect it to constitute a valuable resource for future epigenetic epidemiology studies in pigs.

Pathogenic Th cell subsets in chronic inflammatory diseases

CD4(+) T cells play central roles to appropriate protection against pathogens. While, they can also be pathogenic driving inflammatory diseases. Besides the classical model of differentiation of T helper 1 (Th1) and Th2 cells, various CD4(+) T cell subsets, including Th17, Th9, T follicular helper (Tfh) and T regulatory (Treg) cells, have been recognized recently. In this review, we will focus on how these various CD4(+) T cell subsets contribute to the pathogenesis of immune-mediated inflammatory diseases. We will also discuss various unique subpopulations of T helper cells that have been identified. Recent advancement of the basic immunological research revealed that T helper cells are plastic than we imagined. So, we will focus on the molecular mechanisms underlying the generation of the plasticity and heterogeneity of T helper cell subsets. These latest finding regarding T helper cell subsets has pushed us to reconsider the etiology of immune-mediated inflammatory diseases beyond the model based on the conventional Th1/Th2 balance. Toward this end, we put forward another model, "the pathogenic Th population disease induction model", as a possible mechanism for the induction and/or persistence of immune-mediated inflammatory diseases.

Deletion of the BH3-only protein Noxa alters electrographic seizures but does not protect against hippocampal damage after status epilepticus in mice

Several members of the Bcl-2 gene family are dysregulated in human temporal lobe epilepsy and animal studies show that genetic deletion of some of these proteins influence electrographic seizure responses to chemoconvulsants and associated brain damage. The BH3-only proteins form a subgroup comprising direct activators of Bax–Bak that are potently proapoptotic and a number of weaker proapoptotic BH3-only proteins that act as sensitizers by neutralization of antiapoptotic Bcl-2 family members. Noxa was originally characterized as a weaker proapoptotic, ‘sensitizer' BH3-only protein, although recent evidence suggests it too may be potently proapoptotic. Expression of Noxa is under p53 control, a known seizure-activated pathway, although Noxa has been linked to energetic stress and autophagy. Here we characterized the response of Noxa to prolonged seizures and the phenotype of mice lacking Noxa. Status epilepticus induced by intra-amygdala kainic acid caused a rapid increase in expression of noxa in the damaged CA3 subfield of the hippocampus but not undamaged CA1 region. In vivo upregulation of noxa was reduced by pifithrin-α, suggesting transcription may be partly p53-dependent. Mice lacking noxa developed less severe electrographic seizures during status epilepticus in the model but, surprisingly, displayed equivalent hippocampal damage to wild-type animals. The present findings indicate Noxa does not serve as a proapoptotic BH3-only protein during seizure-induced neuronal death in vivo. This study extends the comprehensive phenotyping of seizure and damage responses in mice lacking specific Bcl-2 gene family members and provides further evidence that these proteins may serve roles beyond control of cell death in the brain.

Th2 Cells in Health and Disease

Helper T (Th) cell subsets direct immune responses by producing signature cytokines. Th2 cells produce IL-4, IL-5, and IL-13, which are important in humoral immunity and protection from helminth infection and are central to the pathogenesis of many allergic inflammatory diseases. Molecular analysis of Th2 cell differentiation and maintenance of function has led to recent discoveries that have refined our understanding of Th2 cell biology. Epigenetic regulation of Gata3 expression by chromatin remodeling complexes such as Polycomb and Trithorax is crucial for maintaining Th2 cell identity. In the context of allergic diseases, memory-type pathogenic Th2 cells have been identified in both mice and humans. To better understand these disease-driving cell populations, we have developed a model called the pathogenic Th population disease induction model. The concept of defined subsets of pathogenic Th cells may spur new, effective strategies for treating intractable chronic inflammatory disorders.

Menin Plays a Critical Role in the Regulation of the Antigen-Specific CD8+ T Cell Response upon Listeria Infection

Menin, a tumor suppressor protein, is encoded by the MEN1 gene in humans. Certain germinal mutations of MEN1 induce an autosomal-dominant syndrome that is characterized by concurrent parathyroid adenomas and several other tumor types. Although menin is also expressed in hematopoietic lineages, its role in CD8⁺ T cells remains unclear. We generated Menin^flox/flox CD4-Cre (Menin-KO) mice by crossing Menin^flox/flox mice with CD4-Cre transgenic (Tg) mice to determine the role of menin in CD8⁺ T cells. Wild-type (WT) and Menin-KO mice were infected with Listeria monocytogenes expressing OVA to analyze the immune response of Ag-specific CD8⁺ T cells. Menin deficiency resulted in an impaired primary immune response by CD8⁺ T cells. On day 7, there were fewer Menin-KO OVA-specific CD8⁺ T cells compared with WT cells. Next, we adoptively transferred WT and Menin-KO OT-1 Tg CD8⁺ T cells into congenic recipient mice and infected them with L. monocytogenes expressing OVA to determine the CD8⁺ T cell-intrinsic effect. Menin-KO OT-1 Tg CD8⁺ T cells were outcompeted by the WT cells upon infection. Increased expression of Blimp-1 and T-bet, cell cycle inhibitors, and proapoptotic genes was observed in the Menin-KO OT-1 Tg CD8⁺ T cells upon infection. These data suggest that menin inhibits differentiation into terminal effectors and positively controls proliferation and survival of Ag-specific CD8⁺ T cells that are activated upon infection. Collectively, our study uncovered an important role for menin in the immune response of CD8⁺ T cells to infection.

Harnessing Noxa demethylation to overcome Bortezomib resistance in mantle cell lymphoma

Bortezomib (BZM) is the first proteasome inhibitor approved for relapsed Mantle Cell Lymphoma (MCL) with durable responses seen in 30%–50% of patients. Given that a large proportion of patients will not respond, BZM resistance is a significant barrier to use this agent in MCL. We hypothesized that a subset of aberrantly methylated genes may be modulating BZM response in MCL patients. Genome-wide DNA methylation analysis using a NimbleGen array platform revealed a striking promoter hypomethylation in MCL patient samples following BZM treatment. Pathway analysis of differentially methylated genes identified molecular mechanisms of cancer as a top canonical pathway enriched among hypomethylated genes in BZM treated samples. Noxa, a pro-apoptotic Bcl-2 family member essential for the cytotoxicity of BZM, was significantly hypomethylated and induced following BZM treatment. Therapeutically, we could demethylate Noxa and induce anti-lymphoma activity using BZM and the DNA methytransferase inhibitor Decitabine (DAC) and their combination in vitro and in vivo in BZM resistant MCL cells. These findings suggest a role for dynamic Noxa methylation for the therapeutic benefit of BZM. Potent and synergistic cytotoxicity between BZM and DAC in vitro and in vivo supports a strategy for using epigenetic priming to overcome BZM resistance in relapsed MCL patients.

Glycolysis inhibition as a cancer treatment and its role in an anti-tumour immune response

Increased glycolysis is the main source of energy supply in cancer cells that use this metabolic pathway for ATP generation. Altered energy metabolism is a biochemical fingerprint of cancer cells that represents one of the "hallmarks of cancer". The immune system can prevent tumour growth by eliminating cancer cells but this editing process ultimately results in poorly immunogenic cells remaining allowing for unchallenged tumour growth. In this review we look at the glycolysis pathway as a target for cancer treatments. We also examine the interplay between the glycolysis modulation and the immune response as an anti-cancer therapy.

CD4+ T-cell subsets in inflammatory diseases: beyond the Th1/Th2 paradigm

CD4(+)T cells are crucial for directing appropriate immune responses during host defense and for the pathogenesis of inflammatory diseases. In addition to the classical biphasic model of differentiation of T-helper 1 (Th1) and Th2 cells, unexpected increases in the numbers of CD4(+)T-cell subsets, including Th17, Th9, T follicular-helper (Tfh) and T-regulatory (Treg) cells, have been recognized. In the present review, we focus on how these various T-helper cell subsets contribute to the pathogenesis of immune-mediated inflammatory diseases. In particular, we focus on multiple sclerosis, psoriasis and asthma as typical model diseases in which multiple T-helper cell subsets have recently been suggested to play a role. We will also discuss various unique sub-populations of T-helper cells that have been identified. First, we will introduce the heterogeneous T-helper cell subsets, which are classified by their simultaneous expression of multiple key transcription factors. We will also introduce different kinds of memory-type Th2 cells, which are involved in the pathogenesis of chronic type-2 immune-related diseases. Finally, we will discuss the molecular mechanisms underlying the generation of the plasticity and heterogeneity of T-helper cell subsets. The latest progress in the study of T-helper cell subsets has forced us to reconsider the etiology of immune-mediated inflammatory diseases beyond the model based on the Th1/Th2 balance. To this end, we propose another model--the pathogenic T-helper population disease-induction model--as a possible mechanism for the induction and/or persistence of immune-mediated inflammatory diseases.

Targeting of BMI-1 with PTC-209 shows potent anti-myeloma activity and impairs the tumour microenvironment

Background

The polycomb complex protein BMI-1 (BMI-1) is a putative oncogene reported to be overexpressed in multiple myeloma (MM). Silencing of BMI-1 was shown to impair the growth and survival of MM cells. However, therapeutic agents specifically targeting BMI-1 were not available so far. Here, we investigated PTC-209, a novel small molecule inhibitor of BMI-1, for its activity in MM.

Methods

BMI-1 expression was analysed in human MM cell lines and primary MM cells by using publically available gene expression profiling (GEP) data. The anti-MM activity of PTC-209 was investigated by viability testing, cell cycle analysis, annexin V and 7-AAD staining, quantification of cleaved poly(ADP-ribose) polymerase (PARP), JC-1 as well as colony formation assays. Deregulation of central myeloma growth and survival genes was studied by quantitative PCR and flow cytometry, respectively. In addition, the impact of PTC-209 on in vitro osteoclast, osteoblast and tube formation was analysed.

Results

We confirmed overexpression of BMI-1 in MM patients by using publically available GEP datasets. Of note, BMI-1 expression was further increased at relapse which translated into significantly shorter overall survival in relapsed/refractory patients treated with bortezomib or dexamethasone.

Treatment with PTC-209 significantly decreased viable cell numbers in human MM cell lines, induced a G1 cell cycle arrest, promoted apoptosis and demonstrated synergistic activity with pomalidomide and carfilzomib. The anti-MM activity of PTC-209 was accompanied by a significant decrease of cyclin D1 (CCND1) and v-myc avian myelocytomatosis viral oncogene homolog (MYC) expression as well as upregulation of cyclin-dependent kinase inhibitor 1A (CDKN1A) and cyclin-dependent kinase inhibitor 1B (CDKN1B). We also observed upregulation of NOXA (up to 3.6 ± 1.2-fold induction, P = 0.009) and subsequent downregulation of myeloid cell leukemia 1 (MCL-1) protein levels, which likely mediates the apoptotic effects of PTC-209. Importantly, the anti-MM activity was upheld in the presence of stromal support or myeloma growth factors insulin-like growth factor 1 (IGF-1) and interleukin 6 (IL-6).

In the MM microenvironment, PTC-209 impaired tube formation, impaired osteoclast development and decreased osteoblast formation in a dose-dependent manner (P < 0.01 at 1 μM, respectively). The latter might be attributed to an induction of DKK1 and was reversed by concurrent anti-DKK1 antibody treatment.

Conclusions

We confirmed overexpression of BMI-1 in MM highlighting its role as an attractive drug target and reveal therapeutic targeting of BMI-1 by PTC-209 as a promising novel therapeutic intervention for MM.

Electronic supplementary material

The online version of this article (doi:10.1186/s13045-016-0247-4) contains supplementary material, which is available to authorized users.

Deciphering the epigenetic code of T lymphocytes

The multiple lineages and differentiation states that constitute the T-cell compartment all derive from a common thymic precursor. These distinct transcriptional states are maintained both in time and after multiple rounds of cell division by the concerted actions of a small set of lineage-defining transcription factors that act in conjunction with a suite of chromatin-modifying enzymes to activate, repress, and fine-tune gene expression. These chromatin modifications collectively provide an epigenetic code that allows the stable and heritable maintenance of the T-cell phenotype. Recently, it has become apparent that the epigenetic code represents a therapeutic target for a variety of immune cell disorders, including lymphoma and acute and chronic inflammatory diseases. Here, we review the recent advances in epigenetic regulation of gene expression, particularly as it relates to the T-cell differentiation and function.

The BMI1 polycomb protein represses cyclin G2-induced autophagy to support proliferation in chronic myeloid leukemia cells

The BMI1 polycomb protein regulates self-renewal, proliferation and survival of cancer-initiating cells essentially through epigenetic repression of the CDKN2A tumor suppressor locus. We demonstrate here for the first time that BMI1 also prevents autophagy in chronic myeloid leukemia (CML) cell lines, to support their proliferation and clonogenic activity. Using chromatin immunoprecipitation, we identified CCNG2/cyclin G2 (CCNG2) as a direct BMI1 target. BMI1 downregulation in CD34+ CML cells by PTC-209 pharmacological treatment or shBMI1 transduction triggered CCNG2 expression and decreased clonogenic activity. Also, ectopic expression of CCNG2 in CD34+ CML cells strongly decreased their clonogenicity. CCNG2 was shown to act by disrupting the phosphatase 2A complex, which activates a PKCζ-AMPK-JNK-ERK pathway that engages autophagy. We observed that BMI1 and CCNG2 levels evolved inversely during the progression of CML towards an acute deadly phase, and therefore hypothesized that BMI1 could support acute transformation of CML through the silencing of a CCNG2-mediated tumor-suppressive autophagy response.

Long Intergenic Non-Coding RNAs: Novel Drivers of Human Lymphocyte Differentiation

Upon recognition of a foreign antigen, CD4(+) naïve T lymphocytes proliferate and differentiate into subsets with distinct functions. This process is fundamental for the effective immune system function, as CD4(+) T cells orchestrate both the innate and adaptive immune response. Traditionally, this differentiation event has been regarded as the acquisition of an irreversible cell fate so that memory and effector CD4(+) T subsets were considered terminally differentiated cells or lineages. Consequently, these lineages are conventionally defined thanks to their prototypical set of cytokines and transcription factors. However, recent findings suggest that CD4(+) T lymphocytes possess a remarkable phenotypic plasticity, as they can often re-direct their functional program depending on the milieu they encounter. Therefore, new questions are now compelling such as which are the molecular determinants underlying plasticity and stability and how the balance between these two opposite forces drives the cell fate. As already mentioned, in some cases, the mere expression of cytokines and master regulators could not fully explain lymphocytes plasticity. We should consider other layers of regulation, including epigenetic factors such as the modulation of chromatin state or the transcription of non-coding RNAs, whose high cell-specificity give a hint on their involvement in cell fate determination. In this review, we will focus on the recent advances in understanding CD4(+) T lymphocytes subsets specification from an epigenetic point of view. In particular, we will emphasize the emerging importance of non-coding RNAs as key players in these differentiation events. We will also present here new data from our laboratory highlighting the contribution of long non-coding RNAs in driving human CD4(+) T lymphocytes differentiation.

Bmi1 regulates auditory hair cell survival by maintaining redox balance

Reactive oxygen species (ROS) accumulation are involved in noise- and ototoxic drug-induced hair cell loss, which is the major cause of hearing loss. Bmi1 is a member of the Polycomb protein family and has been reported to regulate mitochondrial function and ROS level in thymocytes and neurons. In this study, we reported the expression of Bmi1 in mouse cochlea and investigated the role of Bmi1 in hair cell survival. Bmi1 expressed in hair cells and supporting cells in mouse cochlea. Bmi1^−/− mice displayed severe hearing loss and patched outer hair cell loss from postnatal day 22. Ototoxic drug-induced hair cells loss dramatically increased in Bmi1^−/− mice compared with that in wild-type controls both in vivo and in vitro, indicating Bmi1^−/− hair cells were significantly more sensitive to ototoxic drug-induced damage. Cleaved caspase-3 and TUNEL staining demonstrated that apoptosis was involved in the increased hair cell loss of Bmi1^−/− mice. Aminophenyl fluorescein and MitoSOX Red staining showed the level of free radicals and mitochondrial ROS increased in Bmi1^−/− hair cells due to the aggravated disequilibrium of antioxidant–prooxidant balance. Furthermore, the antioxidant N-acetylcysteine rescued Bmi1^−/− hair cells from neomycin injury both in vitro and in vivo, suggesting that ROS accumulation was mainly responsible for the increased aminoglycosides sensitivity in Bmi1^−/− hair cells. Our findings demonstrate that Bmi1 has an important role in hair cell survival by controlling redox balance and ROS level, thus suggesting that Bmi1 may work as a new therapeutic target for the prevention of hair cell death.

Polycomb genes, miRNA, and their deregulation in B-cell malignancies

Posttranslational modifications of histone proteins represent a fundamental means to define distinctive epigenetic states and regulate gene expression during development and differentiation. Aberrations in various chromatin-modulation pathways are commonly used by tumors to initiate and maintain oncogenesis, including lymphomagenesis. Recently, increasing evidence has demonstrated that polycomb group (PcG) proteins, a subset of histone-modifying enzymes known to be crucial for B-cell maturation and differentiation, play a central role in malignant transformation of B cells. PcG hyperactivity in B-cell lymphomas is caused by overexpression or recurrent mutations of PcG genes and deregulation of microRNAs (miRNAs) or transcription factors such as c-MYC, which regulate PcG expression. Interplays of PcG and miRNA deregulations often establish a vicious signal-amplification loop in lymphoma associated with adverse clinical outcomes. Importantly, aberrant enzymatic activities associated with polycomb deregulation, notably those caused by EZH2 gain-of-function mutations, have provided a rationale for developing small-molecule inhibitors as novel therapies. In this review, we summarize our current understanding of PcG-mediated gene silencing, interplays of PcG with other epigenetic regulators such as miRNAs during B-cell differentiation and lymphomagenesis, and recent advancements in targeted strategies against PcG as promising therapeutics for B-cell malignancies.

The polycomb repressive complex 2 governs life and death of peripheral T cells

Differentiation of naïve CD4(+) T cells into effector (Th1, Th2, and Th17) and induced regulatory (iTreg) T cells requires lineage-specifying transcription factors and epigenetic modifications that allow appropriate repression or activation of gene transcription. The epigenetic silencing of cytokine genes is associated with the repressive H3K27 trimethylation mark, mediated by the Ezh2 or Ezh1 methyltransferase components of the polycomb repressive complex 2 (PRC2). Here we show that silencing of the Ifng, Gata3, and Il10 loci in naïve CD4(+) T cells is dependent on Ezh2. Naïve CD4(+) T cells lacking Ezh2 were epigenetically primed for overproduction of IFN-γ in Th2 and iTreg and IL-10 in Th2 cells. In addition, deficiency of Ezh2 accelerated effector Th cell death via death receptor-mediated extrinsic and intrinsic apoptotic pathways, confirmed in vivo for Ezh2-null IFN-γ-producing CD4(+) and CD8(+) T cells responding to Listeria monocytogenes infection. These findings demonstrate the key role of PRC2/Ezh2 in differentiation and survival of peripheral T cells and reveal potential immunotherapeutic targets.

An intergenic regulatory region mediates Drosophila Myc-induced apoptosis and blocks tissue hyperplasia

Induction of cell-autonomous apoptosis following oncogene-induced overproliferation is a major tumor-suppressive mechanism in vertebrates. However, the detailed mechanism mediating this process remains enigmatic. In this study, we demonstrate that dMyc-induced cell-autonomous apoptosis in the fruit fly Drosophila melanogaster relies on an intergenic sequence termed the IRER (irradiation-responsive enhancer region). The IRER mediates the expression of surrounding proapoptotic genes, and we use an in vivo reporter of the IRER chromatin state to gather evidence that epigenetic control of DNA accessibility within the IRER is an important determinant of the strength of this response to excess dMyc. In a previous work, we showed that the IRER also mediates P53-dependent induction of proapoptotic genes following DNA damage, and the chromatin conformation within IRER is regulated by polycomb group-mediated histone modifications. dMyc-induced apoptosis and the P53-mediated DNA damage response thus overlap in a requirement for the IRER. The epigenetic mechanisms controlling IRER accessibility appear to set thresholds for the P53- and dMyc-induced expression of apoptotic genes in vivo and may have a profound impact on cellular sensitivity to oncogene-induced stress.

Zebrafish Noxa promotes mitosis in early embryonic development and regulates apoptosis in subsequent embryogenesis

Noxa functions in apoptosis and immune system of vertebrates, but its activities in embryo development remain unclear. In this study, we have studied the role of zebrafish Noxa (zNoxa) by using zNoxa-specifc morpholino knockdown and overexpression approaches in developing zebrafish embryos. Expression pattern analysis indicates that zNoxa transcript is of maternal origin, which displays a uniform distribution in early embryonic development until shield stage, and the zygote zNoxa transcription is initiated from this stage and mainly localized in YSL of the embryos. The zNoxa expression alterations result in strong embryonic development defects, demonstrating that zNoxa regulates apoptosis from 75% epiboly stage of development onward, in which zNoxa firstly induces the expression of zBik, and then cooperates with zBik to regulate apoptosis. Moreover, zNoxa knockdown also causes a reduction in number of mitotic cells before 8 h.p.f., suggesting that zNoxa also promotes mitosis before 75% epiboly stage. The effect of zNoxa on mitosis is mediated by zWnt4b in early embryos, whereas zMcl1a and zMcl1b suppress the ability of zNoxa to regulate mitosis and apoptosis at different developmental stages. In addition, mammalian mouse Noxa (mNoxa) mRNA was demonstrated to rescue the arrest of mitosis when zNoxa was knocked down, suggesting that mouse and zebrafish Noxa might have similar dual functions. Therefore, the current findings indicate that Noxa is a novel regulator of early mitosis before 75% epiboly stage when it translates into a key mediator of apoptosis in subsequent embryogenesis.

Transcriptional regulation of T helper type 2 differentiation

Considerable progress has been made in recent years towards our understanding of the molecular mechanisms of transcriptional regulation of T helper type 2 (Th2) cell differentiation. Additional transcription factors and chromatin-modifying factors were identified and shown to promote Th2 cell differentiation and inhibit differentiation into other subsets. Analyses of mice lacking several cis-regulatory elements have yielded more insight into the regulatory mechanism of Th2 cytokine genes. Gene deletion studies of several chromatin modifiers confirmed their impact on CD4 T-cell differentiation. In addition, recent genome-wide analyses of transcription factor binding and chromatin status revealed unexpected roles of these factors in Th2-cell differentiation. In this review, these recent findings and their implication are summarized.

Histone methyltransferase and histone methylation in inflammatory T-cell responses

During immune responses, T cells require tightly controlled expression of transcriptional programs to regulate the balance between beneficial and harmful immunity. These transcriptional programs are critical for the lineage specification of effector T cells, the production of effector cytokines and molecules, and the development and maintenance of memory T cells. An emerging theme is that post-translational modification of histones by methylation plays an important role in orchestrating the expression of transcriptional programs in T cells. In this article, we provide a broad overview of histone methylation signatures for effector molecules and transcription factors in T cells, and the functional importance of histone methyltransferases in regulating T-cell immune responses.

The polycomb protein Ezh2 regulates differentiation and plasticity of CD4(+) T helper type 1 and type 2 cells

After antigen encounter by CD4(+) T cells, polarizing cytokines induce the expression of master regulators that control differentiation. Inactivation of the histone methyltransferase Ezh2 was found to specifically enhance T helper 1 (Th1) and Th2 cell differentiation and plasticity. Ezh2 directly bound and facilitated correct expression of Tbx21 and Gata3 in differentiating Th1 and Th2 cells, accompanied by substantial trimethylation at lysine 27 of histone 3 (H3K27me3). In addition, Ezh2 deficiency resulted in spontaneous generation of discrete IFN-γ and Th2 cytokine-producing populations in nonpolarizing cultures, and under these conditions IFN-γ expression was largely dependent on enhanced expression of the transcription factor Eomesodermin. In vivo, loss of Ezh2 caused increased pathology in a model of allergic asthma and resulted in progressive accumulation of memory phenotype Th2 cells. This study establishes a functional link between Ezh2 and transcriptional regulation of lineage-specifying genes in terminally differentiated CD4(+) T cells.

Role of YY1 in long-range chromosomal interactions regulating Th2 cytokine expression

The molecular mechanism for chromatin remodeling and chromosomal interactions at the Th2 cytokine locus is not fully understood. Recently, we showed that transcription factor YY1 is critically involved in these events. This article discusses the possible roles of YY1 in these processes with particular emphasis on long-range chromosomal interactions.

Hoxb4 overexpression in CD4 memory phenotype T cells increases the central memory population upon homeostatic proliferation

Memory T cell populations allow a rapid immune response to pathogens that have been previously encountered and thus form the basis of success in vaccinations. However, the molecular pathways underlying the development and maintenance of these cells are only starting to be unveiled. Memory T cells have the capacity to self renew as do hematopoietic stem cells, and overlapping gene expression profiles suggested that these cells might use the same self-renewal pathways. The transcription factor Hoxb4 has been shown to promote self-renewal divisions of hematopoietic stem cells resulting in an expansion of these cells. In this study we investigated whether overexpression of Hoxb4 could provide an advantage to CD4 memory phenotype T cells in engrafting the niche of T cell deficient mice following adoptive transfer. Competitive transplantation experiments demonstrated that CD4 memory phenotype T cells derived from mice transgenic for Hoxb4 contributed overall less to the repopulation of the lymphoid organs than wild type CD4 memory phenotype T cells after two months. These proportions were relatively maintained following serial transplantation in secondary and tertiary mice. Interestingly, a significantly higher percentage of the Hoxb4 CD4 memory phenotype T cell population expressed the CD62L and Ly6C surface markers, characteristic for central memory T cells, after homeostatic proliferation. Thus Hoxb4 favours the maintenance and increase of the CD4 central memory phenotype T cell population. These cells are more stem cell like and might eventually lead to an advantage of Hoxb4 T cells after subjecting the cells to additional rounds of proliferation.

Stemness of T cells and the hematopoietic stem cells: fate, memory, niche, cytokines

Stem cells are able to generate both cells that differentiate and cells that remain undifferentiated but potentially have the same developmental program. The prolonged duration of the protective immune memory for infectious diseases such as polio, small pox, and measles, suggested that memory T cells may have stem cell properties. Understanding the molecular basis for the life-long persistence of memory T cells may be useful to project targeted therapies for immune deficiencies and infectious diseases and to formulate vaccines. In the last decade evidence from different laboratories shows that memory T cells may share self-renewal pathways with bone marrow hematopoietic stem cells. In stem cells the intrinsic self-renewal activity, which depends on gene expression, is known to be modulated by extrinsic signals from the environment that may be tissue specific. These extrinsic signals for stemness of memory T cells include cytokines such as IL-7 and IL-15 and there are other cytokine signals for maintaining the cytokine signature (TH1, TH2, etc.) of memory T cells. Intrinsic and extrinsic pathways that might be common to bone marrow hematopoietic stem cells and memory T lymphocytes are discussed and related to self-renewal functions.

T Cell Transcription Factors and Their Impact on HIV Expression

By targeting CD4⁺ effector T cells, HIV has a dramatic impact on the depletion, expansion and function of the different polarized T cell subsets. The maturation of T cell lineages is in part driven by intrinsic transcription factors that potentially influence how efficiently HIV replicates. In this review, we explore whether transcription factors that are required for polarizing T cells influence HIV replication. In particular, we examine provirus transcription as well as the establishment and maintenance of HIV latency. Furthermore, it is suggested these factors may provide novel cell-specific therapeutic strategies for targeting the HIV latent reservoir.

BMI1, the polycomb-group gene, is recurrently targeted by genomic rearrangements in progressive B-cell leukemia/lymphoma

BMI1, a Polycomb-group gene located at 10p12.2, is implicated in the pathogenesis of a variety of tumors. However, the genetic molecular mechanisms underlying its aberrant expression in cancer cells remain largely unknown. In this study, we show that BMI1 is recurrently targeted by chromosomal aberrations in B-cell leukemia/lymphoma. We identified a novel t(10;14)(p12;q32)/IGH-BMI1 rearrangement and its IGL variant in six cases of chronic lymphocytic leukemia (CLL) and found that these aberrations were consistently acquired at time of disease progression and high grade transformation of leukemia (Richter syndrome). The IG-BMI1 translocations were not associated with any particular molecular subtype of CLL and the leukemias were negative for common mutations of NOTCH1 and TP53, known to increase a risk of progression and transformation in CLL. In addition, using FISH and SNP array analysis, we identified a wide range of BMI1-involving 10p12 lesions in 17 cases of mantle cell lymphoma (MCL). These aberrations included various balanced and unbalanced structural abnormalities and very frequently but not exclusively, were associated with gain of the BMI1 locus and loss of the 10p terminal sequences. These findings point to genomic instability at the 10p region in MCL which likely promotes rearrangements and deregulation of BMI1. Our findings are in line with previously published observations correlating overexpression of BMI1 with tumor progression and chemoresistance. In summary, our study provides new insights into genetic molecular mechanisms underlying aberrant expression of BMI1 in lymphoma and documents its contribution in the pathogenesis of Richter syndrome and MCL.