A complex interplay of intra- and extracellular factors regulates the outcome of fetal- and adult-derived MLL-rearranged leukemia

Infant and adult MLL1/KMT2A-rearranged (MLLr) leukemia represents a disease with a dismal prognosis. Here, we present a functional and proteomic characterization of in utero-initiated and adult-onset MLLr leukemia. We reveal that fetal MLL::ENL-expressing lymphomyeloid multipotent progenitors (LMPPs) are intrinsically programmed towards a lymphoid fate but give rise to myeloid leukemia in vivo, highlighting a complex interplay of intra- and extracellular factors in determining disease subtype. We characterize early proteomic events of MLL::ENL-mediated transformation in fetal and adult blood progenitors and reveal that whereas adult pre-leukemic cells are mainly characterized by retained myeloid features and downregulation of ribosomal and metabolic proteins, expression of MLL::ENL in fetal LMPPs leads to enrichment of translation-associated and histone deacetylases signaling proteins, and decreased expression of inflammation and myeloid differentiation proteins. Integrating the proteome of pre-leukemic cells with their secretome and the proteomic composition of the extracellular environment of normal progenitors highlights differential regulation of Igf2 bioavailability, as well as of VLA-4 dimer and its ligandome, upon initiation of fetal- and adult-origin leukemia, with implications for human MLLr leukemia cells' ability to communicate with their environment through granule proteins. Our study has uncovered opportunities for targeting ontogeny-specific proteomic vulnerabilities in in utero-initiated and adult-onset MLLr leukemia.

Epigenetic dissection of human blood group genes reveals regulatory elements and detailed characteristics of KEL and four other loci

BACKGROUND

Blood typing is essential for safe transfusions and is performed serologically or genetically. Genotyping predominantly focuses on coding regions, but non-coding variants may affect gene regulation, as demonstrated in the ABO, FY and XG systems. To uncover regulatory loci, we expanded a recently developed bioinformatics pipeline for discovery of non-coding variants by including additional epigenetic datasets.

METHODS

Multiple datasets including ChIP-seq with erythroid transcription factors (TFs), histone modifications (H3K27ac, H3K4me1), and chromatin accessibility (ATAC-seq) were analyzed. Candidate regulatory regions were investigated for activity (luciferase assays) and TF binding (electrophoretic mobility shift assay, EMSA, and mass spectrometry, MS).

RESULTS

In total, 814 potential regulatory sites in 47 blood-group-related genes were identified where one or more erythroid TFs bound. Enhancer candidates in CR1, EMP3, ABCB6, and ABCC4 indicated by ATAC-seq, histone markers, and co-occupancy of 4 TFs (GATA1/KLF1/RUNX1/NFE2) were investigated but only CR1 and ABCC4 showed increased transcription. Co-occupancy of GATA1 and KLF1 was observed in the KEL promoter, previously reported to contain GATA1 and Sp1 sites. TF binding energy scores decreased when three naturally occurring variants were introduced into GATA1 and KLF1 motifs. Two of three GATA1 sites and the KLF1 site were confirmed functionally. EMSA and MS demonstrated increased GATA1 and KLF1 binding to the wild-type compared to variant motifs.

DISCUSSION

This combined bioinformatics and experimental approach revealed multiple candidate regulatory regions and predicted TF co-occupancy sites. The KEL promoter was characterized in detail, indicating that two adjacent GATA1 and KLF1 motifs are most crucial for transcription.

The stem cell-supporting small molecule UM171 triggers Cul3-KBTBD4-mediated degradation of ELM2 domain-harboring proteins

To chemically modulate the ubiquitin-proteasome system for degradation of specific target proteins is currently emerging as an alternative therapeutic modality. Earlier we discovered such properties of the stem cell-supporting small molecule UM171 and identified that members of the CoREST complex (RCOR1 and LSD1) are targeted for degradation. UM171 supports the in vitro propagation of hematopoietic stem cells by transiently perturbing the differentiation-promoting effects of CoREST. Here, we employed global proteomics to map the UM171-targeted proteome and identified the additional target proteins, namely RCOR3, RREB1, ZNF217, and MIER2. Further, we discovered that critical elements recognized by Cul3^KBTBD4 ligase in the presence of UM171 are located within the EGL-27 and MTA1 homology 2 (ELM2) domain of the substrate proteins. Subsequent experiments identified conserved amino acid sites in the N-terminus of the ELM2 domain that are essential for UM171-mediated degradation. Overall, our findings provide a detailed account on the ELM2 degrome targeted by UM171 and identify critical sites required for UM171-mediated degradation of specific substrates. Given the target profile, our results are highly relevant in a clinical context and point towards new therapeutic applications for UM171.

Quantitative analysis of redox proteome reveals oxidation-sensitive protein thiols acting in fundamental processes of developmental hematopoiesis

Fetal and adult hematopoietic stem and progenitor cells (HSPCs) are characterized by distinct redox homeostasis that may influence their differential cellular behavior in normal and malignant hematopoiesis. In this work, we have applied a quantitative mass spectrometry-based redox proteomic approach to comprehensively describe reversible cysteine modifications in primary mouse fetal and adult HSPCs. We defined the redox state of 4,438 cysteines in fetal and adult HSPCs and demonstrated a higher susceptibility to oxidation of protein thiols in fetal HSPCs. Our data identified ontogenic changes to oxidation state of thiols in proteins with a pronounced role in metabolism and protein homeostasis. Additional redox proteomic analysis identified oxidation changes to thiols acting in mitochondrial respiration as well as protein homeostasis to be triggered during onset of MLL-ENL leukemogenesis in fetal HSPCs. Our data has demonstrated that redox signaling contributes to the regulation of fundamental processes of developmental hematopoiesis and has pinpointed potential targetable redox-sensitive proteins in in utero-initiated MLL-rearranged leukemia.

Probing CP symmetry and weak phases with entangled double-strange baryons

Though immensely successful, the standard model of particle physics does not offer any explanation as to why our Universe contains so much more matter than antimatter. A key to a dynamically generated matter-antimatter asymmetry is the existence of processes that violate the combined charge conjugation and parity (CP) symmetry1. As such, precision tests of CP symmetry may be used to search for physics beyond the standard model. However, hadrons decay through an interplay of strong and weak processes, quantified in terms of relative phases between the amplitudes. Although previous experiments constructed CP observables that depend on both strong and weak phases, we present an approach where sequential two-body decays of entangled multi-strange baryon-antibaryon pairs provide a separation between these phases. Our method, exploiting spin entanglement between the double-strange Ξ- baryon and its antiparticle2 [Formula: see text], has enabled a direct determination of the weak-phase difference, (ξP - ξS) = (1.2 ± 3.4 ± 0.8) × 10-2 rad. Furthermore, three independent CP observables can be constructed from our measured parameters. The precision in the estimated parameters for a given data sample size is several orders of magnitude greater than achieved with previous methods3. Finally, we provide an independent measurement of the recently debated Λ decay parameter αΛ (refs. 4,5). The [Formula: see text] asymmetry is in agreement with and compatible in precision to the most precise previous measurement4.

A somatic mutation in moesin drives progression into acute myeloid leukemia

Acute myeloid leukemia (AML) arises when leukemia-initiating cells, defined by a primary genetic lesion, acquire subsequent molecular changes whose cumulative effects bypass tumor suppression. The changes that underlie AML pathogenesis not only provide insights into the biology of transformation but also reveal novel therapeutic opportunities. However, backtracking these events in transformed human AML samples is challenging, if at all possible. Here, we approached this question using a murine in vivo model with an MLL-ENL fusion protein as a primary molecular event. Upon clonal transformation, we identified and extensively verified a recurrent codon-changing mutation (Arg²⁹⁵Cys) in the ERM protein moesin that markedly accelerated leukemogenesis. Human cancer-associated moesin mutations at the conserved arginine-295 residue similarly enhanced MLL-ENL-driven leukemogenesis. Mechanistically, the mutation interrupted the stability of moesin and conferred a neomorphic activity to the protein, which converged on enhanced extracellular signal-regulated kinase activity. Thereby, our studies demonstrate a critical role of ERM proteins in AML, with implications also for human cancer.

The Opportunity of Proteomics to Advance the Understanding of Intra- and Extracellular Regulation of Malignant Hematopoiesis

Fetal and adult hematopoiesis are regulated by largely distinct sets of cell-intrinsic gene regulatory networks as well as extracellular cues in their respective microenvironment. These ontogeny-specific programs drive hematopoietic stem and progenitor cells (HSPCs) in fetus and adult to divergent susceptibility to initiation and progression of hematological malignancies, such as leukemia. Elucidating how leukemogenic hits disturb the intra- and extracellular programs in HSPCs along ontogeny will provide a better understanding of the causes for age-associated differences in malignant hematopoiesis and facilitate the improvement of strategies for prevention and treatment of pediatric and adult acute leukemia. Here, we review current knowledge of the intrinsic and extrinsic programs regulating normal and malignant hematopoiesis, with a particular focus on the differences between infant and adult acute leukemia. We discuss the recent advances in mass spectrometry-based proteomics and its opportunity for resolving the interplay of cell-intrinsic and niche-associated factors in regulating malignant hematopoiesis.

Ontogenic shifts in cellular fate are linked to proteotype changes in lineage-biased hematopoietic progenitor cells

The process of hematopoiesis is subject to substantial ontogenic remodeling that is accompanied by alterations in cellular fate during both development and disease. We combine state-of-the-art mass spectrometry with extensive functional assays to gain insight into ontogeny-specific proteomic mechanisms regulating hematopoiesis. Through deep coverage of the cellular proteome of fetal and adult lympho-myeloid multipotent progenitors (LMPPs), common lymphoid progenitors (CLPs), and granulocyte-monocyte progenitors (GMPs), we establish that features traditionally attributed to adult hematopoiesis are conserved across lymphoid and myeloid lineages, whereas generic fetal features are suppressed in GMPs. We reveal molecular and functional evidence for a diminished granulocyte differentiation capacity in fetal LMPPs and GMPs relative to their adult counterparts. Our data indicate an ontogeny-specific requirement of myosin activity for myelopoiesis in LMPPs. Finally, we uncover an ontogenic shift in the monocytic differentiation capacity of GMPs, partially driven by a differential expression of Irf8 during fetal and adult life.

Treatment With Bupropion and Varenicline for Smoking Cessation and the Risk of Acute Cardiovascular Events and Injuries: a Swedish Case-Crossover Study

Introduction

Bupropion and varenicline are non-nicotine medications used for smoking cessation that mitigate craving and withdrawal symptoms. We aim to investigate whether these drugs increase the risk of selected acute adverse outcomes when used in medical practice.

Methods

Population-based case-crossover design using data from Swedish health and administrative registers. Adult individuals diagnosed with acute myocardial infarction, stroke, suicide, suicide attempt, fall injury, or that suffered a road traffic crash from 01.10.2006 for bupropion, or from 01.03.2008 for varenicline, until 31.12.2013 were included. Different lengths of exposure periods were analyzed within the 12-week hazard period prior to the adverse outcome (1-14, 15-28, and 29-84 days). The control period was matched using the interval preceding the hazard period (85-168 days), and breaking it up into equivalent periods (85-98, 99-112, and 113-168 days). Conditional logistic regression with each case considered as one stratum was used to estimate adjusted odds ratios (OR) and confidence intervals (CI).

Results

Neither medication was associated with consistent higher risks for any of the adverse outcomes. For bupropion and varenicline, respectively, in the 1-14 days hazard period, OR (95% CI) were: myocardial infarction 1.14 (0.55 to 2.34) and 1.06 (0.70 to 1.62); stroke 1.16 (0.39 to 3.47) and 1.26 (0.72 to 2.17), and traffic crashes 0.85 (0.39 to 1.85) and 1.48 (0.90 to 2.41). In the other periods, ORs were similar or even lower. For falls and suicidal events ORs were generally below one for both drugs.

Conclusion

The available evidence suggests that if prescription guidelines are properly followed regarding potential contraindications both of these medications could be considered relatively safe.

Implications

The reliable exposure and diagnosis assessment used in this nationwide register-based study, along with the number of cases gathered makes this sample one of the largest of its type to assess potential side effects associated with the use of these drugs. Neither medication was associated with consistent higher risks for any of the adverse outcomes studied.

Radiographers' perspectives' on Visual Grading Analysis as a scientific method to evaluate image quality

INTRODUCTION

Radiographers routinely undertake many initiatives to balance image quality with radiation dose (optimisation). For optimisation studies to be successful image quality needs to be carefully evaluated. Purpose was to 1) discuss the strengths and limitations of a Visual Grading Analysis (VGA) method for image quality evaluation and 2) to outline the method from a radiographer's perspective.

METHODS

A possible method for investigating and discussing the relationship between radiographic image quality parameters and the interpretation and perception of X-ray images is the VGA method. VGA has a number of advantages such as being low cost and a detailed image quality assessment, although it is limited to ensure the images convey the relevant clinical information and relate the task based radiography.

RESULTS

Comparing the experience of using VGA and Receiver Operating Characteristic (ROC) it is obviously that less papers are published on VGA (Pubmed n=1.384) compared to ROC (Pubmed n=122.686). Hereby the scientific experience of the VGA method is limited compared to the use of ROC. VGA is, however, a much newer method and it is slowly gaining more and more attention.

CONCLUSION

The success of VGA requires a number of steps to be completed, such as defining the VGA criteria, choosing the VGA method (absolute or relative), including observers, finding the best image display platforms, training observers and selecting the best statistical method for the study purpose should be thoroughly considered.

IMPLICATION FOR PRACTICE

Detailed evaluation of image quality for optimisation studies related to technical definition of image quality.

Early growth response 1 regulates hematopoietic support and proliferation in human primary bone marrow stromal cells

Human bone marrow stromal cells (BMSC) are key elements of the hematopoietic environment and they play a central role in bone and bone marrow physiology. However, how key stromal cell functions are regulated is largely unknown. We analyzed the role of the immediate early response transcription factor EGR1 as key stromal cell regulator and found that EGR1 was highly expressed in prospectively-isolated primary BMSC, down-regulated upon culture, and low in non-colony-forming CD45^neg stromal cells. Furthermore, EGR1 expression was lower in proliferative regenerating adult and fetal primary cells compared to adult steady-state BMSC. Overexpression of EGR1 in stromal cells induced potent hematopoietic stroma support as indicated by an increased production of transplantable CD34⁺CD90⁺ hematopoietic stem cells in expansion co-cultures. The improvement in bone marrow stroma support function was mediated by increased expression of hematopoietic supporting genes, such as VCAM1 and CCL28. Furthermore, EGR1 overexpression markedly decreased stromal cell proliferation whereas EGR1 knockdown caused the opposite effects. These findings thus show that EGR1 is a key stromal transcription factor with a dual role in regulating proliferation and hematopoietic stroma support function that is controlling a genetic program to co-ordinate the specific functions of BMSC in their different biological contexts.

Activation of neuronal genes via LINE-1 elements upon global DNA demethylation in human neural progenitors

DNA methylation contributes to the maintenance of genomic integrity in somatic cells, in part through the silencing of transposable elements. In this study, we use CRISPR-Cas9 technology to delete DNMT1, the DNA methyltransferase key for DNA methylation maintenance, in human neural progenitor cells (hNPCs). We observe that inactivation of DNMT1 in hNPCs results in viable, proliferating cells despite a global loss of DNA CpG-methylation. DNA demethylation leads to specific transcriptional activation and chromatin remodeling of evolutionarily young, hominoid-specific LINE-1 elements (L1s), while older L1s and other classes of transposable elements remain silent. The activated L1s act as alternative promoters for many protein-coding genes involved in neuronal functions, revealing a hominoid-specific L1-based transcriptional network controlled by DNA methylation that influences neuronal protein-coding genes. Our results provide mechanistic insight into the role of DNA methylation in silencing transposable elements in somatic human cells, as well as further implicating L1s in human brain development and disease.

DNA methylation plays an important role in silencing transposable elements. Here the authors find that loss of DNMT1 and DNA methylation leads to transcriptional activation and chromatin remodelling of evolutionarily young—hominoid-specific —LINE-1 elements which then act as alternative promoters for neuronal genes.

Comparative Secretome Analyses of Primary Murine White and Brown Adipocytes Reveal Novel Adipokines

The adipose organ, including white and brown adipose tissues, is an important player in systemic energy homeostasis, storing excess energy in form of lipids while releasing energy upon various energy demands. Recent studies have demonstrated that white and brown adipocytes also function as endocrine cells and regulate systemic metabolism by secreting factors that act locally and systemically. However, a comparative proteomic analysis of secreted factors from white and brown adipocytes and their responsiveness to adrenergic stimulation has not been reported yet. Therefore, we studied and compared the secretome of white and brown adipocytes, with and without norepinephrine (NE) stimulation. Our results reveal that carbohydrate-metabolism-regulating proteins are preferably secreted from white adipocytes, while brown adipocytes predominantly secrete a large variety of proteins. Upon NE stimulation, an increased secretion of known adipokines is favored by white adipocytes while brown adipocytes secreted higher amounts of novel adipokines. Furthermore, the secretory response between NE-stimulated and basal state was multifaceted addressing lipid and glucose metabolism, adipogenesis, and antioxidative reactions. Intriguingly, NE stimulation drastically changed the secretome in brown adipocytes. In conclusion, our study provides a comprehensive catalogue of novel adipokine candidates secreted from white and brown adipocytes with many of them responsive to NE. Given the beneficial effects of brown adipose tissue activation on its endocrine function and systemic metabolism, this study provides an archive of novel batokine candidates and biomarkers for activated brown adipose tissue.

Author Correction: BCAT1 restricts αKG levels in AML stem cells leading to IDHmut-like DNA hypermethylation

In Extended Data Fig. 1a of this Letter, the flow cytometry plot depicting the surface phenotype of AML sample DD08 was a duplicate of the plot for AML sample DD06. Supplementary Data 4 has been added to the Supplementary Information of the original Letter to clarify the proteome data acquisition and presentation. The original Letter has been corrected online.

Comprehensive Proteomic Characterization of Ontogenic Changes in Hematopoietic Stem and Progenitor Cells

Hematopoietic stem and progenitor cells (HSPCs) in the fetus and adult possess distinct molecular landscapes that regulate cell fate and change their susceptibility to initiation and progression of hematopoietic malignancies. Here, we applied in-depth quantitative proteomics to comprehensively describe and compare the proteome of fetal and adult HSPCs. Our data uncover a striking difference in complexity of the cellular proteomes, with more diverse adult-specific HSPC proteomic signatures. The differential protein content in fetal and adult HSPCs indicate distinct metabolic profiles and protein complex stoichiometries. Additionally, adult characteristics include an arsenal of proteins linked to viral and bacterial defense, as well as protection against ROS-induced protein oxidation. Further analyses show that interferon α, as well as Neutrophil elastase, has distinct functional effects in fetal and adult HSPCs. This study provides a rich resource aimed toward an enhanced mechanistic understanding of normal and malignant hematopoiesis during fetal and adult life.

Exploring the potential of a multi-level approach to improve capability for continuous organizational improvement and learning in a Swedish healthcare region

BACKGROUND

Eldercare and care of people with functional impairments is organized by the municipalities in Sweden. Improving care in these areas is complex, with multiple stakeholders and organizations. Appropriate strategies to develop capability for continuing organizational improvement and learning (COIL) are needed. The purpose of our study was to develop and pilot-test a flexible, multilevel approach for COIL capability building and to identify what it takes to achieve changes in key actors' approaches to COIL. The approach, named "Sustainable Improvement and Development through Strategic and Systematic Approaches" (SIDSSA), was applied through an action-research and action-learning intervention.

METHODS

The SIDSSA approach was tested in a regional research and development (R&D) unit, and in two municipalities handling care of the elderly and people with functional impairments. Our approach included a multilevel strategy, development loops of five flexible phases, and an action-learning loop. The approach was designed to support systems understanding, strategic focus, methodological practices, and change process knowledge - all of which required double-loop learning. Multiple qualitative methods, i.e., repeated interviews, process diaries, and documents, provided data for conventional content analyses.

RESULTS

The new approach was successfully tested on all cases and adopted and sustained by the R&D unit. Participants reported new insights and skills. The development loop facilitated a sense of coherence and control during uncertainty, improved planning and problem analysis, enhanced mapping of context and conditions, and supported problem-solving at both the individual and unit levels. The systems-level view and structured approach helped participants to explain, motivate, and implement change initiatives, especially after working more systematically with mapping, analyses, and goal setting.

CONCLUSIONS

An easily understood and generalizable model internalized by key organizational actors is an important step before more complex development models can be implemented. SIDSSA facilitated individual and group learning through action-learning and supported systems-level views and structured approaches across multiple organizational levels. Active involvement of diverse organizational functions and levels in the learning process was facilitated. However, the time frame was too short to fully test all aspects of the approach, specifically in reaching beyond the involved managers to front-line staff and patients.

De novo activating mutations drive clonal evolution and enhance clonal fitness in KMT2A-rearranged leukemia

Activating signaling mutations are common in acute leukemia with KMT2A (previously MLL) rearrangements (KMT2A-R). These mutations are often subclonal and their biological impact remains unclear. Using a retroviral acute myeloid mouse leukemia model, we demonstrate that FLT3^ITD, FLT3^N676K, and NRAS^G12D accelerate KMT2A-MLLT3 leukemia onset. Further, also subclonal FLT3^N676K mutations accelerate disease, possibly by providing stimulatory factors. Herein, we show that one such factor, MIF, promotes survival of mouse KMT2A-MLLT3 leukemia initiating cells. We identify acquired de novo mutations in Braf, Cbl, Kras, and Ptpn11 in KMT2A-MLLT3 leukemia cells that favored clonal expansion. During clonal evolution, we observe serial genetic changes at the Kras^G12D locus, consistent with a strong selective advantage of additional Kras^G12D. KMT2A-MLLT3 leukemias with signaling mutations enforce Myc and Myb transcriptional modules. Our results provide new insight into the biology of KMT2A-R leukemia with subclonal signaling mutations and highlight the importance of activated signaling as a contributing driver.

In acute leukemia with KMT2A rearrangements (KMT2A-R), activating signaling mutations are common. Here, the authors use a retroviral acute myeloid mouse leukemia model to show that subclonal de novo activating mutations drive clonal evolution in acute leukemia with KMT2A-R and enhance clonal fitness.

Pseudouridylation of tRNA-Derived Fragments Steers Translational Control in Stem Cells

Pseudouridylation (Ψ) is the most abundant and widespread type of RNA epigenetic modification in living organisms; however, the biological role of Ψ remains poorly understood. Here, we show that a Ψ-driven posttranscriptional program steers translation control to impact stem cell commitment during early embryogenesis. Mechanistically, the Ψ "writer" PUS7 modifies and activates a novel network of tRNA-derived small fragments (tRFs) targeting the translation initiation complex. PUS7 inactivation in embryonic stem cells impairs tRF-mediated translation regulation, leading to increased protein biosynthesis and defective germ layer specification. Remarkably, dysregulation of this posttranscriptional regulatory circuitry impairs hematopoietic stem cell commitment and is common to aggressive subtypes of human myelodysplastic syndromes. Our findings unveil a critical function of Ψ in directing translation control in stem cells with important implications for development and disease.

Dabrafenib plus trametinib versus dabrafenib monotherapy in patients with metastatic BRAF V600E/K-mutant melanoma: long-term survival and safety analysis of a phase 3 study

Background

Previous analysis of COMBI-d (NCT01584648) demonstrated improved progression-free survival (PFS) and overall survival (OS) with combination dabrafenib and trametinib versus dabrafenib monotherapy in BRAF V600E/K-mutant metastatic melanoma. This study was continued to assess 3-year landmark efficacy and safety after ≥36-month follow-up for all living patients.

Patients and methods

This double-blind, phase 3 study enrolled previously untreated patients with BRAF V600E/K-mutant unresectable stage IIIC or stage IV melanoma. Patients were randomized to receive dabrafenib (150 mg twice daily) plus trametinib (2 mg once daily) or dabrafenib plus placebo. The primary endpoint was PFS; secondary endpoints were OS, overall response, duration of response, safety, and pharmacokinetics.

Results

Between 4 May and 30 November 2012, a total of 423 of 947 screened patients were randomly assigned to receive dabrafenib plus trametinib (n = 211) or dabrafenib monotherapy (n = 212). At data cut-off (15 February 2016), outcomes remained superior with the combination: 3-year PFS was 22% with dabrafenib plus trametinib versus 12% with monotherapy, and 3-year OS was 44% versus 32%, respectively. Twenty-five patients receiving monotherapy crossed over to combination therapy, with continued follow-up under the monotherapy arm (per intent-to-treat principle). Of combination-arm patients alive at 3 years, 58% remained on dabrafenib plus trametinib. Three-year OS with the combination reached 62% in the most favourable subgroup (normal lactate dehydrogenase and <3 organ sites with metastasis) versus only 25% in the unfavourable subgroup (elevated lactate dehydrogenase). The dabrafenib plus trametinib safety profile was consistent with previous clinical trial observations, and no new safety signals were detected with long-term use.

Conclusions

These data demonstrate that durable (≥3 years) survival is achievable with dabrafenib plus trametinib in patients with BRAF V600-mutant metastatic melanoma and support long-term first-line use of the combination in this setting.

BCAT1 restricts αKG levels in AML stem cells leading to IDHmut-like DNA hypermethylation

The branched-chain amino acid (BCAA) pathway and high levels of BCAA transaminase 1 (BCAT1) have recently been associated with aggressiveness in several cancer entities. However, the mechanistic role of BCAT1 in this process remains largely uncertain. Here, by performing high-resolution proteomic analysis of human acute myeloid leukaemia (AML) stem-cell and non-stem-cell populations, we find the BCAA pathway enriched and BCAT1 protein and transcripts overexpressed in leukaemia stem cells. We show that BCAT1, which transfers α-amino groups from BCAAs to α-ketoglutarate (αKG), is a critical regulator of intracellular αKG homeostasis. Further to its role in the tricarboxylic acid cycle, αKG is an essential cofactor for αKG-dependent dioxygenases such as Egl-9 family hypoxia inducible factor 1 (EGLN1) and the ten-eleven translocation (TET) family of DNA demethylases. Knockdown of BCAT1 in leukaemia cells caused accumulation of αKG, leading to EGLN1-mediated HIF1α protein degradation. This resulted in a growth and survival defect and abrogated leukaemia-initiating potential. By contrast, overexpression of BCAT1 in leukaemia cells decreased intracellular αKG levels and caused DNA hypermethylation through altered TET activity. AML with high levels of BCAT1 (BCAT1^high) displayed a DNA hypermethylation phenotype similar to cases carrying a mutant isocitrate dehydrogenase (IDH^mut), in which TET2 is inhibited by the oncometabolite 2-hydroxyglutarate. High levels of BCAT1 strongly correlate with shorter overall survival in IDH^WTTET2^WT, but not IDH^mut or TET2^mut AML. Gene sets characteristic for IDH^mut AML were enriched in samples from patients with an IDH^WTTET2^WTBCAT1^high status. BCAT1^high AML showed robust enrichment for leukaemia stem-cell signatures, and paired sample analysis showed a significant increase in BCAT1 levels upon disease relapse. In summary, by limiting intracellular αKG, BCAT1 links BCAA catabolism to HIF1α stability and regulation of the epigenomic landscape, mimicking the effects of IDH mutations. Our results suggest the BCAA-BCAT1-αKG pathway as a therapeutic target to compromise leukaemia stem-cell function in patients with IDH^WTTET2^WT AML.

Vismodegib in patients with advanced basal cell carcinoma: Primary analysis of STEVIE, an international, open-label trial

BACKGROUND

The SafeTy Events in VIsmodEgib study (STEVIE, ClinicalTrials.gov, NCT01367665), assessed safety and efficacy of vismodegib-a first-in-class Hedgehog pathway inhibitor demonstrating clinical benefit in advanced basal cell carcinoma (BCC)-in a patient population representative of clinical practice. Primary analysis data are presented.

PATIENTS AND METHODS

Patients with locally advanced or metastatic BCC received oral vismodegib 150 mg/d until progressive disease, unacceptable toxicity, or withdrawal. Primary objective was safety. Efficacy variables were assessed as secondary end-points.

RESULTS

Evaluable adult patients (N = 1215, 1119 locally advanced; 96 metastatic BCC) from 36 countries were treated; 147 patients (12%) remained on study at time of reporting. Median (range) treatment duration was 8.6 (0-44) months. Most patients (98%) had ≥1 treatment-emergent adverse event (TEAE). The incidence of the most common TEAEs was consistent with reports in previous analyses. No association between creatine phosphokinase (CPK) abnormalities and muscle spasm was observed. Serious TEAEs occurred in 289 patients (23.8%). Exposure ≥12 months did not lead to increased incidence or severity of new TEAEs. The majority of the most common TEAEs ongoing at time of treatment discontinuation resolved by 12 months afterwards, regardless of Gorlin syndrome status. Response rates (investigator-assessed) in patients with histologically confirmed measurable baseline disease were 68.5% (95% confidence interval (CI) 65.7-71.3) in patients with locally advanced BCC and 36.9% (95% CI 26.6-48.1) in patients with metastatic BCC.

CONCLUSIONS

The primary analysis of STEVIE demonstrates that vismodegib is tolerable in typical patients in clinical practice; safety profile is consistent with that in previous reports. Long-term exposure was not associated with worsening severity/frequency of TEAEs. Investigator-assessed response rates showed high rate of tumour control. CLINICALTRIALS.GOV: NCT01367665.

Species diversity regarding the presence of proximal tubular progenitor cells of the kidney

The cellular source for tubular regeneration following kidney injury is a matter of dispute, with reports suggesting a stem or progenitor cells as the regeneration source while linage tracing studies in mice seemingly favor the classical theory, where regeneration is performed by randomly surviving cells. We, and others have previously described a scattered cell population localized to the tubules of human kidney, which increases in number following injury. Here we have characterized the species distribution of these proximal tubular progenitor cells (PTPCs) in kidney tissue from chimpanzee, pig, rat and mouse using a set of human PTPC markers. We detected PTPCs in chimpanzee and pig kidneys, but not in mouse tissue. Also, subjecting mice to the unilateral urethral obstruction model, caused clear signs of tubular injury, but failed to induce the PTPC phenotype in renal tubules.

Inflammation-Induced Emergency Megakaryopoiesis Driven by Hematopoietic Stem Cell-like Megakaryocyte Progenitors

Infections are associated with extensive platelet consumption, representing a high risk for health. However, the mechanism coordinating the rapid regeneration of the platelet pool during such stress conditions remains unclear. Here, we report that the phenotypic hematopoietic stem cell (HSC) compartment contains stem-like megakaryocyte-committed progenitors (SL-MkPs), a cell population that shares many features with multipotent HSCs and serves as a lineage-restricted emergency pool for inflammatory insults. During homeostasis, SL-MkPs are maintained in a primed but quiescent state, thus contributing little to steady-state megakaryopoiesis. Even though lineage-specific megakaryocyte transcripts are expressed, protein synthesis is suppressed. In response to acute inflammation, SL-MkPs become activated, resulting in megakaryocyte protein production from pre-existing transcripts and a maturation of SL-MkPs and other megakaryocyte progenitors. This results in an efficient replenishment of platelets that are lost during inflammatory insult. Thus, our study reveals an emergency machinery that counteracts life-threatening platelet depletions during acute inflammation.

Trends in cutaneous malignant melanoma in Sweden 1997-2011: thinner tumours and improved survival among men

BACKGROUND

Both patient survival and the proportion of patients diagnosed with thin cutaneous malignant melanoma (CMM) have been steadily rising in Sweden as in most Western countries, although the rate of improvement in survival appears to have declined in Sweden at the end of the last millennium.

OBJECTIVES

To analyse the most recent trends in the distribution of tumour thickness (T category) as well as CMM-specific survival in Swedish patients diagnosed during 1997-2011.

METHODS

This nationwide population-based study included 30,590 patients registered in the Swedish Melanoma Register (SMR) and diagnosed with a first primary invasive CMM during 1997-2011. The patients were followed through 2012 in the national Cause of Death Register.

RESULTS

Logistic and Cox regression analyses adjusting for age at diagnosis, tumour site and healthcare region were carried out. The odds ratio for being diagnosed with thicker tumours was significantly reduced (P < 0·001) and the CMM-specific survival significantly improved in men diagnosed during 2007-2011 compared with men diagnosed during 1997-2001 (hazard ratio = 0·81; 95% confidence interval 0·72-0·91; P < 0·001), while the corresponding differences for women were not significant. Women were diagnosed with significantly thicker tumours during 2002-2006 and a tendency towards decreased survival was observed compared with those diagnosed earlier (during 1997-2001) and later (during 2007-2011).

CONCLUSIONS

In Sweden, the CMMs of men are detected earlier over time and this seems to be followed by an improved CMM-specific survival for men. Women are still diagnosed with considerably thinner tumours and they experience a better survival than men.

Prognostic factors in localized invasive primary cutaneous malignant melanoma: results of a large population-based study

BACKGROUND

The prognostic impact of several histopathological prognostic features in cutaneous malignant melanoma (CMM) remains controversial.

OBJECTIVES

To assess the independent prognostic value of mitotic rate, regression, tumour-infiltrating lymphocytes (TILs) and growth phase in primary stage I and II CMMs.

METHODS

Clinicohistopathological data were obtained from the Stockholm-Gotland registry for 4237 patients diagnosed with an incident primary stage I or II CMM followed up to December 2011. The risk of CMM-specific death was evaluated by a Cox regression model.

RESULTS

A mitotic rate of 1-10 mitoses per mm(2) [hazard ratio (HR) 1·69, 95% confidence interval (CI) 1·16-2·45] and > 10 mitoses per mm(2) (HR 2·27, 95% CI 1·46-3·52) were significant; TILs and regression were not. A more detailed analysis of data assessed between 1989 and 1995 confirmed significantly increased HRs for the presence vs. absence of mitoses (HR1-5/mm² 2·25, 95% CI 1·36-3·76; HR6-10/mm² 2·34, 95% CI 1·23-4·44; HR> 10/mm² 2·64, 95% CI 1·39-4·99). Other prognosticators were increasing T-stage vs. T1, presence of ulceration and presence of vertical growth phase (VGP). In T1 CMMs, an increasing tumour thickness vs. < 0·7 mm (HR0·7-0·8 mm 2·24, 95% CI 1·24-4·04; HR>0·8 mm  2·92, 95% CI 1·57-5·43) and presence of ulceration were significantly associated with higher HRs; mitotic rate, TILs, regression and growth phase were not.

CONCLUSIONS

Determinants of increased risk of CMM death in stage I and II CMMs were increasing T-stage, presence of ulceration, presence of mitoses and VGP. This was not found for TILs or regression.

Transcriptome-wide profiling and posttranscriptional analysis of hematopoietic stem/progenitor cell differentiation toward myeloid commitment

Hematopoietic stem cells possess lifelong self-renewal activity and generate multipotent progenitors that differentiate into lineage-committed and subsequently mature cells. We present a comparative transcriptome analysis of ex vivo isolated mouse multipotent hematopoietic stem/progenitor cells (Lin(neg)SCA-1(+)c-KIT(+)) and myeloid committed precursors (Lin(neg)SCA-1(neg)c-KIT(+)). Our data display dynamic transcriptional networks and identify a stem/progenitor gene expression pattern that is characterized by cell adhesion and immune response components including kallikrein-related proteases. We identify 498 expressed lncRNAs, which are potential regulators of multipotency or lineage commitment. By integrating these transcriptome with our recently reported proteome data, we found evidence for posttranscriptional regulation of processes including metabolism and response to oxidative stress. Finally, our study identifies a high number of genes with transcript isoform regulation upon lineage commitment. This in-depth molecular analysis outlines the enormous complexity of expressed coding and noncoding RNAs and posttranscriptional regulation during the early differentiation steps of hematopoietic stem cells toward the myeloid lineage.

Identification of regulatory networks in HSCs and their immediate progeny via integrated proteome, transcriptome, and DNA methylome analysis

In this study, we present integrated quantitative proteome, transcriptome, and methylome analyses of hematopoietic stem cells (HSCs) and four multipotent progenitor (MPP) populations. From the characterization of more than 6,000 proteins, 27,000 transcripts, and 15,000 differentially methylated regions (DMRs), we identified coordinated changes associated with early differentiation steps. DMRs show continuous gain or loss of methylation during differentiation, and the overall change in DNA methylation correlates inversely with gene expression at key loci. Our data reveal the differential expression landscape of 493 transcription factors and 682 lncRNAs and highlight specific expression clusters operating in HSCs. We also found an unexpectedly dynamic pattern of transcript isoform regulation, suggesting a critical regulatory role during HSC differentiation, and a cell cycle/DNA repair signature associated with multipotency in MPP2 cells. This study provides a comprehensive genome-wide resource for the functional exploration of molecular, cellular, and epigenetic regulation at the top of the hematopoietic hierarchy.

Snus (Swedish smokeless tobacco) use and risk of stroke: pooled analyses of incidence and survival

BACKGROUND

Snus is a moist smokeless tobacco product with high nicotine content. Its use has a short-term effect on the cardiovascular system, but the relationship between snus use and stroke is unclear.

OBJECTIVE

The aim of this study was to assess the associations between use of snus and incidence of and survival after stroke, both overall and according to subtypes.

METHODS

Pooled analyses of eight Swedish prospective cohort studies were conducted, including 130 485 men who never smoked. We estimated hazard ratios (HRs) with 95% confidence intervals (CIs) of incidence and death after diagnosis using Cox proportional hazard regression models and case fatality and survival using logistic regression and Kaplan-Meier methods, respectively.

RESULTS

No associations were observed between the use of snus and the risk of overall stroke (HR 1.04, 95% CI 0.92-1.17) or of any of the stroke subtypes. The odds ratio (OR) of 28-day case fatality was 1.42 (95% CI 0.99-2.04) amongst users of snus who had experienced a stroke, and the HR of death during the follow-up period was 1.32 (95% CI 1.08-1.61).

CONCLUSION

Use of snus was not associated with the risk of stroke. Hence, nicotine is unlikely to contribute importantly to the pathophysiology of stroke. However, case fatality was increased in snus users, compared with nonusers, but further studies are needed to determine any possible causal mechanisms.