Twist dependent magneto-optical response in twisted bilayer graphene.

By employing a linearised Boltzmann equation, we calculate the magneto-optical properties of twisted bilayer graphene using non-magnetic wave functions. Both transverse and longitudinal responses are calculated up to the second order in applied magnetic field with their twist angle and Fermi level dependence examined. We find that increasing the twist angle increases the transverse metallic response so long as the Fermi level remains below the upper conduction band. Interlayer transitions provide an appreciable enhancement when the Fermi level traverses the gap between the two conduction bands. Interlayer transitions are also responsible for a nonzero anomalous Hall conductivity in this model. As the Fermi level moves towards zero, the longitudinal response begins to dominate and a highly anisotropic negative magneto-resistance is observed.

Core-binding factor leukemia hijacks the T-cell-prone PU.1 antisense promoter.

The blood system serves as a key model for cell differentiation and cancer. It is orchestrated by precise spatiotemporal expression of crucial transcription factors. One of the key master regulators in the hematopoietic systems is PU.1. Reduced levels of PU.1 are characteristic for human acute myeloid leukemia (AML) and are known to induce AML in mouse models. Here, we show that transcriptional downregulation of PU.1 is an active process involving an alternative promoter in intron 3 that is induced by RUNX transcription factors driving noncoding antisense transcription. Core-binding factor (CBF) fusions RUNX1-ETO and CBFß-MYH11 in t(8;21) and inv(16) AML, respectively, activate the PU.1 antisense promoter that results in a shift from sense toward antisense transcription and myeloid differentiation blockade. In patients with CBF-AML, we found that an elevated antisense/sense transcript and promoter accessibility ratio represents a hallmark compared with normal karyotype AML or healthy CD34+ cells. Competitive interaction of an enhancer with the proximal or the antisense promoter forms a binary on/off switch for either myeloid or T-cell development. Leukemic CBF fusions thus use a physiological mechanism used by T cells to decrease sense transcription. Our study is the first example of a sense/antisense promoter competition as a crucial functional switch for gene expression perturbation by oncogenes. Hence, this disease mechanism reveals a previously unknown Achilles heel for future precise therapeutic targeting of oncogene-induced chromatin remodeling.

Parallel PRC2/cPRC1 and vPRC1 pathways silence lineage-specific genes and maintain self-renewal in mouse embryonic stem cells.

The transcriptional repressors Polycomb repressive complex 1 (PRC1) and PRC2 are required to maintain cell fate during embryonic development. PRC1 and PRC2 catalyze distinct histone modifications, establishing repressive chromatin at shared targets. How PRC1, which consists of canonical PRC1 (cPRC1) and variant PRC1 (vPRC1) complexes, and PRC2 cooperate to silence genes and support mouse embryonic stem cell (mESC) self-renewal is unclear. Using combinatorial genetic perturbations, we show that independent pathways of cPRC1 and vPRC1 are responsible for maintenance of H2A monoubiquitylation and silencing of shared target genes. Individual loss of PRC2-dependent cPRC1 or PRC2-independent vPRC1 disrupts only one pathway and does not impair mESC self-renewal capacity. However, loss of both pathways leads to mESC differentiation and activation of a subset of lineage-specific genes co-occupied by relatively high levels of PRC1/PRC2. Thus, parallel pathways explain the differential requirements for PRC1 and PRC2 and provide robust silencing of lineage-specific genes.

Drug-induced inhibition of phosphorylation of STAT5 overrides drug resistance in neoplastic mast cells.

Systemic mastocytosis (SM) is a mast cell (MC) neoplasm with complex pathology and a variable clinical course. In aggressive SM (ASM) and MC leukemia (MCL), responses to conventional drugs are poor and the prognosis is dismal. R763 is a multi-kinase inhibitor that blocks the activity of Aurora-kinase-A/B, ABL1, AKT and FLT3. We examined the effects of R763 on proliferation and survival of neoplastic MC. R763 produced dose-dependent inhibition of proliferation in the human MC lines HMC-1.1 (IC50 5-50 nM), HMC-1.2 (IC50 1-10 nM), ROSAKIT WT (IC50 1-10 nM), ROSAKIT D816V (IC50 50-500 nM) and MCPV-1.1 (IC50 100-1000 nM). Moreover, R763 induced growth inhibition in primary neoplastic MC in patients with ASM and MCL. Growth-inhibitory effects of R763 were accompanied by signs of apoptosis and a G2/M cell cycle arrest. R763 also inhibited phosphorylation of KIT, BTK, AKT and STAT5 in neoplastic MC. The most sensitive target appeared to be STAT5. In fact, tyrosine phosphorylation of STAT5 was inhibited by R763 at 10 nM. At this low concentration, R763 produced synergistic growth-inhibitory effects on neoplastic MC when combined with midostaurin or dasatinib. Together, R763 is a novel promising multi-kinase inhibitor that blocks STAT5 activation and thereby overrides drug-resistance in neoplastic MC.

The role of complement inhibition in kidney transplantation.

INTRODUCTION AND BACKGROUND: The complement system which belongs to the innate immune system acts both as a first line of defence against various pathogens and as a guardian of host homeostasis. The role of complement has been recently highlighted in several aspects of kidney transplantation: ischaemia-reperfusion, antibody-mediated rejection and native kidney disease recurrence. SOURCES OF DATA: Experimental data, availability of complement-blocking molecules (mainly the anti-C5 monoclonal antibody, eculizumab) and several trials in human kidney transplant recipients has led to some areas of agreement and some disappointment. AREAS OF AGREEMENT AND CONTROVERSIES: So far, eculizumab has shown great efficacy in treatment and prevention of atypical haemolytic and uraemic syndrome, some efficacy in the prevention of antibody-mediated and so far no efficacy in the prevention of delayed graft function. GROWING POINTS: Among the numerous potentially available drugs potentially interfering with complement, recent focus has been made on C1 blockers in the setting of antibody-mediated rejection with promising results. AREAS TIMELY FOR DEVELOPING RESEARCH: Complement is now recognized as a major player in transplant immunology, several targets are going to be tested to define precisely which ones may be potentially useful in clinical practice.

[Hemolytic and uremic syndrome and related thrombotic microangiopathies: Treatment and prognosis]. / Syndromes hémolytiques et urémiques (SHU) et syndromes de microangiopathie thrombotique apparentés : traitement et pronostic.

Major achievements in the understanding of thrombotic microangiopathies (TMA) have not only resulted in a reclassification of TMA but most of all they have culminated in the design of new treatments and have enabled clinicians to better delineate their prognosis. Recent multicenter studies have improved our understanding of the prognosis of atypical hemolytic and uremic syndromes (aHUS). More specifically, they have highlighted the role of genetic testing on predicting the recurrence of aHUS, the risk of chronic kidney disease and the recurrence following kidney transplantation. A major advance consisted of the identification of the alternative complement pathway in the pathogenesis of aHUS, thus paving the way for the use of the C5a inhibitor eculizumab in this indication. Eculizumab has thereafter dramatically improved the management of patients affected with aHUS. During spring 2011, a great epidemic of entero-hemorrhagic Escherichia coli (EHEC) associated HUS occurred in Germany, providing clinicians the opportunity to examine the relevance of antibiotic prophylaxis, plasma exchange and eculizumab in EHEC-associated HUS. In this work, we herein present advances achieved in the setting of therapeutic management and prognosis in HUS and other related TMA syndromes.

[Hemolytic and uremic syndrome and related thrombotic microangiopathies: Epidemiology, pathophysiology and clinics]. / SHU et syndromes de microangiopathie thrombotique apparentés : épidémiologie, physiopathologie et tableaux cliniques.

Thrombotic microangiopathies (TMA) represent an eclectic group of conditions, which share hemolytic anemia and thrombocytopenia as a common defining basis. Remarkable breakthroughs in the physiopathological setting have allowed for a thorough recomposition of the disparate syndromes, which form the constellation of TMA. In this view, clinicians now discriminate thrombocytopenic thrombotic purpura (TTP) defined by a severe deficiency in ADAMTS13, which is rarely associated with a severe renal involvement and the hemolytic and uremic syndrome (HUS) in which renal impairment is the most prominent clinical feature. HUS can result from toxins stemming from bacterial infections of the digestive tract, alternate complement pathway abnormalities, metabolic or coagulation disorders or, lastly, drug and various toxic compounds. The diverse forms of HUS reflect the insights gained in the understanding of the pathophysiological mechanisms underpinning TMA. In this first part, a broad overview of the epidemiological, physiopathological and clinical aspects of HUS and related TMA syndromes is presented.

Origin of Enriched Regulatory T Cells in Patients Receiving Combined Kidney-Bone Marrow Transplantation to Induce Transplantation Tolerance.

We examined tolerance mechanisms in patients receiving HLA-mismatched combined kidney-bone marrow transplantation (CKBMT) that led to transient chimerism under a previously published nonmyeloablative conditioning regimen (Immune Tolerance Network study 036). Polychromatic flow cytometry and high-throughput sequencing of T cell receptor-ß hypervariable regions of DNA from peripheral blood regulatory T cells (Tregs) and CD4 non-Tregs revealed marked early enrichment of Tregs (CD3+ CD4+ CD25high CD127low Foxp3+ ) in blood that resulted from peripheral proliferation (Ki67+ ), possibly new thymic emigration (CD31+ ), and, in one tolerant subject, conversion from non-Tregs. Among recovering conventional T cells, central memory CD4+ and CD8+ cells predominated. A large proportion of the T cell clones detected in posttransplantation biopsy specimens by T cell receptor sequencing were detected in the peripheral blood and were not donor-reactive. Our results suggest that enrichment of Tregs by new thymic emigration and lymphopenia-driven peripheral proliferation in the early posttransplantation period may contribute to tolerance after CKBMT. Further, most conventional T cell clones detected in immunologically quiescent posttransplantation biopsy specimens appear to be circulating cells in the microvasculature rather than infiltrating T cells.

Cutaneous involvement in the deep mycoses: A review. Part II -Systemic mycoses. / Afectación cutánea en las micosis profundas: una revisión de la literatura. Parte 2. Micosis sistémicas.

In the second part of this review on the deep mycoses, we describe the main systemic mycoses-paracoccidioidomycosis, coccidioidomycosis, histoplasmosis, mucormycosis, and cryptococcosis-and their cutaneous manifestations. Skin lesions are only occasionally seen in deep systemic mycoses either directly, when the skin is the route of entry for the fungus, or indirectly, when the infection has spread from a deeper focus. These cutaneous signs are often the only clue to the presence of a potentially fatal infection. As with the subcutaneous mycoses, early diagnosis and treatment is important, but in this case, even more so.

Data on step-by-step atomic force microscopy monitoring of changes occurring in single melanoma cells undergoing ToF SIMS specialized sample preparation protocol.

Data included in this article are associated with the research article entitled 'Protocol of single cells preparation for time-of-flight secondary ion mass spectrometry' (Bobrowska et al., 2016 in press) [1]. This data file contains topography images of single melanoma cells recorded using atomic force microscopy (AFM). Single cells cultured on glass surface were subjected to the proposed sample preparation protocol applied to prepare biological samples for time-of-flight secondary ion mass spectrometry (ToF SIMS) measurements. AFM images were collected step-by-step for the single cell, after each step of the proposed preparation protocol. It consists of four main parts: (i) paraformaldehyde fixation, (ii) salt removal, (iii) dehydrating, and (iv) sample drying. In total 13 steps are required, starting from imaging of a living cell in a culture medium and ending up at images of a dried cell in the air. The protocol was applied to melanoma cells from two cell lines, namely, WM115 melanoma cells originated from primary melanoma site and WM266-4 ones being the metastasis of WM115 cells to skin.

Cutaneous Involvement in the Deep Mycoses: A Literature Review. Part I-Subcutaneous Mycoses. / Afectación cutánea en las micosis profundas: una revisión de la literatura. Parte 1: micosis subcutáneas.

The deep mycoses are uncommon in our setting. These fungal infections occur mainly in immunosuppressed patients or in tropical climates, and include subcutaneous infections and systemic infections. The skin is always involved in the former. In the first part of this review, we describe the main subcutaneous mycoses: sporotrichosis, chromoblastomycosis, mycetoma, phaeohyphomycosis, hyalohyphomycosis, and lacaziosis. Early recognition and treatment is important, as these infections are frequently associated with high morbidity.

Identification of bromodomain-containing protein-4 as a novel marker and epigenetic target in mast cell leukemia.

Advanced systemic mastocytosis (SM) is a life-threatening neoplasm characterized by uncontrolled growth and accumulation of neoplastic mast cells (MCs) in various organs and a poor survival. So far, no curative treatment concept has been developed for these patients. We identified the epigenetic reader bromodomain-containing protein-4 (BRD4) as novel drug target in aggressive SM (ASM) and MC leukemia (MCL). As assessed by immunohistochemistry and PCR, neoplastic MCs expressed substantial amounts of BRD4 in ASM and MCL. The human MCL lines HMC-1 and ROSA also expressed BRD4, and their proliferation was blocked by a BRD4-specific short hairpin RNA. Correspondingly, the BRD4-targeting drug JQ1 induced dose-dependent growth inhibition and apoptosis in HMC-1 and ROSA cells, regardless of the presence or absence of KIT D816V. In addition, JQ1 suppressed the proliferation of primary neoplastic MCs obtained from patients with ASM or MCL (IC50: 100-500 nm). In drug combination experiments, midostaurin (PKC412) and all-trans retinoic acid were found to cooperate with JQ1 in producing synergistic effects on survival in HMC-1 and ROSA cells. Taken together, we have identified BRD4 as a promising drug target in advanced SM. Whether JQ1 or other BET-bromodomain inhibitors are effective in vivo in patients with advanced SM remains to be elucidated.

Macrochimerism in Intestinal Transplantation: Association With Lower Rejection Rates and Multivisceral Transplants, Without GVHD.

Blood chimerism has been reported sporadically among visceral transplant recipients, mostly in association with graft-vs-host disease (GVHD). We hypothesized that a higher degree of mixed chimerism would be observed in multivisceral (MVTx) than in isolated intestinal (iITx) and isolated liver transplant (iLTx) recipients, regardless of GVHD. We performed a longitudinal prospective study investigating multilineage blood chimerism with flow cytometry in 5 iITx and 4 MVTx recipients up to one year posttransplant. Although only one iITx patient experienced GVHD, T cell mixed chimerism was detected in 8 out of 9 iITx/MVTx recipients. Chimerism was significantly lower in the four subjects who displayed early moderate to severe rejection. Pre-formed high-titer donor-specific antibodies, bound in vivo to the circulating donor cells, were associated with an accelerated decline in chimerism. Blood chimerism was also studied in 10 iLTx controls. Among nonsensitized patients, MVTx recipients exhibited greater T and B cell chimerism than either iITx or iLTx recipients. Myeloid lineage chimerism was present exclusively among iLTx and MVTx (6/13) recipients, suggesting that its presence required the hepatic allograft. Our study demonstrates, for the first time, frequent T cell chimerism without GVHD following visceral transplantation and a possible relationship with reduced rejection rate in MVTx recipients.

Hyperactivation of mTORC1 and mTORC2 by multiple oncogenic events causes addiction to eIF4E-dependent mRNA translation in T-cell leukemia.

High activation of the PI3K-AKT-mTOR pathway is characteristic for T-cell acute lymphoblastic leukemia (T-ALL). The activity of the master regulator of this pathway, PTEN, is often impaired in T-ALL. However, experimental evidence suggests that input from receptor tyrosine kinases (RTKs) is required for sustained mTOR activation, even in the absence of PTEN. We previously reported the expression of Neurotrophin receptor tyrosine kinases (TRKs) and their respective ligands in primary human leukemia samples. In the present study we aimed to dissect the downstream signaling cascades of TRK-induced T-ALL in a murine model and show that T-ALLs induced by deregulated receptor tyrosine kinase signaling acquire activating mutations in Notch1 and lose PTEN during clonal evolution. Some clones additionally lost one allele of the homeodomain transcription factor Cux1. All events independently led to a gradual hyperactivation of both mTORC1 and mTORC2 signaling. We dissected the role of the individual mTOR complexes by shRNA knockdown and found that the separate depletion of mTORC1 or mTORC2 reduced the growth of T-ALL blasts, but was not sufficient to induce apoptosis. In contrast, knockdown of the mTOR downstream effector eIF4E caused a striking cytotoxic effect, demonstrating a critical addiction to cap-dependent mRNA-translation. Although high mTORC2-AKT activation is commonly associated with drug-resistance, we demonstrate that T-ALL displaying a strong mTORC2-AKT activation were specifically susceptible to 4EGI-1, an inhibitor of the eIF4E-eIF4G interaction. To decipher the mechanism of 4EGI-1, we performed a genome-wide analysis of mRNAs that are translationally regulated by 4EGI-1 in T-ALL. 4EGI-1 effectively reduced the ribosomal occupancy of mRNAs that were strongly upregulated in T-ALL blasts compared with normal thymocytes including transcripts important for translation, mitochondria and cell cycle progression, such as cyclins and ribosomal proteins. These data suggest that disrupting the eIF4E-eIF4G interaction constitutes a promising therapy strategy in mTOR-deregulated T-cell leukemia.

ZRF1 controls the retinoic acid pathway and regulates leukemogenic potential in acute myeloid leukemia.

Acute myeloid leukemia (AML) is frequently linked to epigenetic abnormalities and deregulation of gene transcription, which lead to aberrant cell proliferation and accumulation of undifferentiated precursors. ZRF1, a recently characterized epigenetic factor involved in transcriptional regulation, is highly overexpressed in human AML, but it is not known whether it plays a role in leukemia progression. Here, we demonstrate that ZRF1 depletion decreases cell proliferation, induces apoptosis and enhances cell differentiation in human AML cells. Treatment with retinoic acid (RA), a differentiating agent currently used to treat certain AMLs, leads to a functional switch of ZRF1 from a negative regulator to an activator of differentiation. At the molecular level, ZRF1 controls the RA-regulated gene network through its interaction with the RA receptor α (RARα) and its binding to RA target genes. Our genome-wide expression study reveals that ZRF1 regulates the transcription of nearly half of RA target genes. Consistent with our in vitro observations that ZRF1 regulates proliferation, apoptosis, and differentiation, ZRF1 depletion strongly inhibits leukemia progression in a xenograft mouse model. Finally, ZRF1 knockdown cooperates with RA treatment in leukemia suppression in vivo. Taken together, our data reveal that ZRF1 is a key transcriptional regulator in leukemia progression and suggest that ZRF1 inhibition could be a novel strategy to be explored for AML treatment.

Eculizumab improves posttransplant thrombotic microangiopathy due to antiphospholipid syndrome recurrence but fails to prevent chronic vascular changes.

Thrombotic microangiopathy (TMA) is one of the hallmark vascular lesions of antiphospholipid syndrome nephropathy (APSN). These lesions are at high risk of recurrence after kidney transplantation. The complement pathway is thought to be active in this process. We used eculizumab to treat three consecutive kidney transplant recipients with posttransplant TMA due to APSN recurrence that was resistant to plasmapheresis and explored the complement deposition and apoptotic and vascular cell markers on the sequential transplant biopsies. Treatment with eculizumab resulted in a rapid and dramatic improvement of the graft function in all three patients and in improvement of the TMA lesions within the graft. None of these patients had TMA flares after eculizumab was withdrawn. At the time of TMA diagnosis, immunofluorescence studies revealed intense C5b-9 and C4d depositions at the endothelial cell surface of the injured vessels. Moreover, C5b-9 colocalized with vessels exhibiting a high rate of apoptotic cells. Examination of sequential biopsies during eculizumab therapy showed that TMA lesions, C4d and apoptotic markers were rapidly cleared but the C5b-9 deposits persisted for several months as a footprint of the TMA. Finally, we noticed that complement inhibition did not prevent the development of the chronic vascular changes associated with APSN. Eculizumab seems to be an efficient method for treating severe forms of posttransplant TMA due to APSN recurrence. Terminal complement inhibition does not prevent the development of chronic APSN.

Complement genes strongly predict recurrence and graft outcome in adult renal transplant recipients with atypical hemolytic and uremic syndrome.

Atypical hemolytic and uremic syndrome (aHUS) is a severe disease strongly associated with genetic abnormalities in the complement alternative pathway. In renal posttransplantation, few data are available on recurrence risk and graft outcome according to genetic background in aHUS patients. The aim of this study was to identify risk factors for recurrence and transplant outcome and, in particular, the role of complement gene abnormalities. We retrospectively studied 57 aHUS patients who had received 71 renal transplants. A mutation in complement gene was identified in 39 (68%), in factor H (CFH), factor I (CFI), membrane cofactor-protein (MCP), C3 and factor B (CFB). At 5 years, death-censored graft survival was 51%. Disease recurrence was associated with graft loss (p = 0.001). Mutations in complement genes were associated with higher risk of recurrence (p = 0.009). Patients with CFH or gain of function (C3, CFB) mutations had a highest risk of recurrence. M-TOR inhibitor was associated with significant risk of recurrence (p = 0.043) but not calcineurin inhibitor immunosuppressive treatment (p = 0.29). Preemptive plasmatherapy was associated with a trend to decrease recurrence (p = 0.07). Our study highlights that characterization of complement genetic abnormalities predicts the risk of recurrence-related graft loss and paves the way for future genetically based individualized prophylactic therapeutic strategies.

The Polycomb complex PRC2 supports aberrant self-renewal in a mouse model of MLL-AF9;Nras(G12D) acute myeloid leukemia.

The Trithorax and Polycomb groups of chromatin regulators are critical for cell-lineage specification during normal development; functions that often become deregulated during tumorigenesis. As an example, oncogenic fusions of the Trithorax-related protein mixed lineage leukemia (MLL) can initiate aggressive leukemias by altering the transcriptional circuitry governing hematopoietic cell differentiation, a process that requires multiple epigenetic pathways to implement. Here we used shRNA screening to identify chromatin regulators uniquely required in a mouse model of MLL-fusion acute myeloid leukemia, which revealed a role for the Polycomb repressive complex 2 (PRC2) in maintenance of this disease. shRNA-mediated suppression of PRC2 subunits Eed, Suz12 or Ezh1/Ezh2 led to proliferation arrest and differentiation of leukemia cells, with a minimal impact on growth of several non-transformed hematopoietic cell lines. The requirement for PRC2 in leukemia is partly because of its role in direct transcriptional repression of genes that limit the self-renewal potential of hematopoietic cells, including Cdkn2a. In addition to implicating a role for PRC2 in the pathogenesis of MLL-fusion leukemia, our results suggest, more generally, that Trithorax and Polycomb group proteins can cooperate with one another to maintain aberrant lineage programs in cancer.