The role of a Runt domain transcription factor AML1/RUNX1 in leukemogenesis and its clinical implications

Myelodysplastic syndrome with dual germline RUNX1 and DDX41 variants: a rare genetic predisposition case

Germline variants in RUNX1 and DDX41 are well-established contributors to hereditary myeloid neoplasms and are increasingly recognized as critical predisposing factors in the developing myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML). This case report details a 51-year-old male diagnosed with MDS with excess blasts-1 (MDS-EB1), who harbored a rare combination of pathogenic germline variants in RUNX1 and a novel potentially pathogenic variant in DDX41 variant, alongside a somatic DDX41 mutation. The coexistence of these germline variants highlights the genetic complexity underlying hereditary myeloid neoplasms and reinforces the necessity of comprehensive genomic testing to ensure accurate diagnosis and informed clinical management. The interplay between RUNX1 and DDX41 variants may drive leukemogenesis, with the germline RUNX1 variant potentially fostering a cellular environment that enables the acquisition of somatic DDX41 mutations, leading to hematological malignancies. Conversely, the germline DDX41 variant may disrupt hematopoiesis and, when combined with RUNX1 dysfunction, contribute to disease progression. This case underscores the importance of screening germline variants in patients with myeloid neoplasms. It emphasizes the need to confirm the origin of these variants in non-hematopoietic tissues, such as fibroblasts (gold standard), to avoid misinterpretation caused by clonal hematopoiesis. Further research is warranted to elucidate the molecular mechanisms driving the interaction between RUNX1 and DDX41 variants and their collective impact on disease progression, treatment outcomes, and familial risk.

ARMH1 is a novel marker associated with poor pediatric AML outcomes that affect the fatty acid synthesis and cell cycle pathways

Introduction

Despite remarkable progress in Pediatric Acute Myeloid Leukemia (pAML) treatments, the relapsed disease remains difficult to treat, making it pertinent to identify novel biomarkers of prognostic/therapeutic significance.

Material and methods

Bone marrow samples from 21 pAML patients were analyzed using single cell RNA sequencing, functional assays with ARMH1 knockdown and overexpression were performed in leukemia cell lines to evaluate impact on proliferation and migration, and chemotherapy sensitivity. Mitochondrial function was assessed via Seahorse assay, ARMH1 interacting proteins were studied using co-immunoprecipitation. Bulk RNA-seq was performed on ARMH1knockdown and over expressing cell lines to evaluate the pathways and networks impacted by ARMH1.

Results

Our data shows that ARMH1, a novel cancer-associated gene, is highly expressed in the malignant blast cells of multiple pediatric hematologic malignancies, including AML, T/B-ALL, and T/B-MPAL. Notably, ARMH1 expression is significantly elevated in blast cells of patients who relapsed or have a high-risk cytogenetic profile (MLL) compared to standard-risk (RUNX1, inv (16)). ARMH1 expression is also significantly correlated with the pediatric leukemia stem cell score of 6 genes (LSC6) associated with poor outcomes. Perturbation of ARMH1 (knockdown and overexpression) in leukemia cell lines significantly impacted cell proliferation and migration. The RNA-sequencing analysis on multiple ARMH1 knockdown and overexpressing cell lines established an association with mitochondrial fatty acid synthesis and cell cycle pathways.The investigation of the mitochondrial matrix shows that pharmacological inhibition of a key enzyme in fatty acid synthesis regulation, CPT1A, resulted in ARMH1 downregulation. ARMH1 knockdown also led to a significant reduction in CPT1A and ATP production as well as Oxygen Consumption Rate. Our data indicates that downregulating ARMH1 impacts cell proliferation by reducing key cell cycle regulators such as CDCA7 and EZH2. Further, we also established that ARMH1 is a key physical interactant of EZH2, associated with multiple cancers.

Conclusion

Our findings underscore further evaluation of ARMH1 as a potential candidate for targeted therapies and stratification of aggressive pAML to improve outcomes.

The Modulation of Septic Shock: A Proteomic Approach

Sepsis poses a significant challenge due its lethality, involving multiple organ dysfunction and impaired immune responses. Among several factors affecting sepsis, monocytes play a crucial role; however, their phenotype, proteomic profile, and function in septic shock remain unclear. Our aim was to fully characterize the subpopulations and proteomic profiles of monocytes seen in septic shock cases and discuss their possible impact on the disease. Peripheral blood monocyte subpopulations were phenotype based on CD14/CD16 expression by flow cytometry, and proteins were extracted from the monocytes of individuals with septic shock and healthy controls to identify changes in the global protein expression in these cells. Analysis using 2D-nanoUPLC-UDMSE identified 67 differentially expressed proteins in shock patients compared to controls, in which 44 were upregulated and 23 downregulated. These proteins are involved in monocyte reprogramming, immune dysfunction, severe hypotension, hypo-responsiveness to vasoconstrictors, vasodilation, endothelial dysfunction, vascular injury, and blood clotting, elucidating the disease severity and therapeutic challenges of septic shock. This study identified critical biological targets in monocytes that could serve as potential biomarkers for the diagnosis, prognosis, and treatment of septic shock, providing new insights into the pathophysiology of the disease.

Germline Variants and Characteristic Features of Hereditary Hematological Malignancy Syndrome

Due to the proliferation of genetic testing, pathogenic germline variants predisposing to hereditary hematological malignancy syndrome (HHMS) have been identified in an increasing number of genes. Consequently, the field of HHMS is gaining recognition among clinicians and scientists worldwide. Patients with germline genetic abnormalities often have poor outcomes and are candidates for allogeneic hematopoietic stem cell transplantation (HSCT). However, HSCT using blood from a related donor should be carefully considered because of the risk that the patient may inherit a pathogenic variant. At present, we now face the challenge of incorporating these advances into clinical practice for patients with myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML) and optimizing the management and surveillance of patients and asymptomatic carriers, with the limitation that evidence-based guidelines are often inadequate. The 2016 revision of the WHO classification added a new section on myeloid malignant neoplasms, including MDS and AML with germline predisposition. The main syndromes can be classified into three groups. Those without pre-existing disease or organ dysfunction; DDX41, TP53, CEBPA, those with pre-existing platelet disorders; ANKRD26, ETV6, RUNX1, and those with other organ dysfunctions; SAMD9/SAMD9L, GATA2, and inherited bone marrow failure syndromes. In this review, we will outline the role of the genes involved in HHMS in order to clarify our understanding of HHMS.

lncRNA GAS5 and RUNX1 Genes in Children With Primary Immune Thrombocytopenia

We aimed to evaluate the expression levels and the prognostic value of growth arrest specific 5 (GAS5) and runt-related transcription factor 1 (RUNX1) genes in children with ITP. This prospective cohort study included 100 patients with newly diagnosed ITP (patient group) and 100 healthy children of matched age and sex (control group). We evaluated the expression levels of both GAS5 and RUNX1 genes at the time of diagnosis before the introduction of treatment. GAS5 was under-expressed, while RUNX1 was over-expressed among the newly diagnosed ITP children compared with the control group. Patients with GAS5 levels >0.50 had a significantly faster recovery compared with patients with levels≤0.50 while patients with levels of RUNX1≤2.6 had a significantly faster recovery compared with patients with levels >2.6. The best cut-off values of GAS5 and RUNX1 to predict complete recovery of ITP were ˃0.40 and ˂3.18, respectively, yielding a sensitivity of 76.47% and 79.41%, respectively. The best cut-off values of GAS5 and RUNX1 expression that predict chronic ITP were ˂0.17 and ˃4.1, respectively, yielding sensitivity of 88.89% and 77.78%, respectively. GAS5 and RUNX1 could be useful markers in children with primary ITP to predict disease course.

RUNX1 and RUNX3 Genes Expression Level in Adult Acute Lymphoblastic Leukemia-A Case Control Study

The genetic factors of adult acute lymphoblastic leukemia (ALL) development are only partially understood. The Runt-Related Transcription Factor (RUNX) gene family play a crucial role in hematological malignancies, serving both a tumor suppressor and promoter function. The aim of this study was the assessment of relative RUNX1 and RUNX3 genes expression level among adult ALL cases and a geographically and ethnically matched control group. The relative RUNX1 and RUNX3 genes expression level was assessed by qPCR. The investigated group comprised 60 adult patients newly diagnosed with ALL. The obtained results were compared with a group of 40 healthy individuals, as well as clinical and hematological parameters of patients, and submitted for statistical analysis. ALL patients tend to have significantly higher RUNX1 gene expression level compared with controls. This observation is also true for risk group stratification where high-risk (HR) patients presented higher levels of RUNX1. A higher RUNX1 transcript level correlates with greater leukocytosis while RUNX3 expression is reduced in Philadelphia chromosome bearers. The conducted study sustains the hypothesis that both a reduction and increase in the transcript level of RUNX family genes may be involved in leukemia pathogenesis, although their interaction is complex. In this context, overexpression of the RUNX1 gene in adult ALL cases in particular seems interesting. Obtained results should be interpreted with caution. Further analysis in this research field is needed.

Association of Immune Thrombocytopenia and T-Lymphoblastic Lymphoma in a Pediatric Patient

Immune thrombocytopenia (ITP) is characterized by isolated thrombocytopenia of unclear etiology. We present a unique case of an 8-year-old girl with chronic ITP who was subsequently diagnosed with T-lymphoblastic lymphoma at age 11. The clinical course was complicated by the occurrence of nonepileptiform events with bizarre behavior changes following the administration of nelarabine and intrathecal and high-dose systemic methotrexate. This case highlights an unusual co-occurrence of hematologic malignancy and chronic ITP in an otherwise healthy child. We speculate that underlying genetic or immunologic lesions may predispose a subset of pediatric ITP patients to the development of hematologic malignancies.

RUNX1 contributes to the mesenchymal subtype of glioblastoma in a TGFβ pathway-dependent manner

Runt-Related Transcription Factor 1 (RUNX1) is highly expressed in the Mesenchymal (Mes) subtype of glioblastoma (GBM). However, the specific molecular mechanism of RUNX1 in Mes GBM remains largely elusive. In this study, cell and tumor tissue typing were performed by RNA-sequencing. Co-immunoprecipitation (co-IP) and immunofluorescence (IF) were employed to identify members of the RUNX1 transcriptional protein complex. Bioinformatics analysis, chromatin immunoprecipitation (ChIP), and luciferase reporter experiments were utilized to verify target genes. Analyses of The Cancer Genome Atlas (TCGA) and Chinese Glioma Genome Atlas (CGGA) verified the expression levels and prognoses associated with RUNX1/p-SMAD3/SUV39H1 target genes. In vivo patient-derived xenograft (PDX) studies and in vitro functional studies verified the impact of RUNX1 on the occurrence and development of GBM. The results showed that RUNX1 was upregulated in Mes GBM cell lines, tissues and patients and promoted proliferation and invasion in GBM in a TGFβ pathway-dependent manner in vivo and in vitro. We found and verified that BCL3 and MGP are transcriptionally activated by p-SMAD3 /RUNX1, while MXI1 is transcriptionally suppressed by the RUNX1/SUV39H1-H3K9me3 axis. This finding offers a theoretical rationale for using molecular markers and choosing therapeutic targets for the Mes type of GBM.

Epigenetic Regulation in the Pathogenesis of Sjögren Syndrome and Rheumatoid Arthritis

Autoimmune rheumatic diseases, such as Sjögren syndrome (SS) and rheumatoid arthritis (RA), are characterized by chronic inflammation and autoimmunity, which cause joint tissue damage and destruction by triggering reduced mobility and debilitation in patients with these diseases. Initiation and maintenance of chronic inflammatory stages account for several mechanisms that involve immune cells as key players and the interaction of the immune cells with other tissues. Indeed, the overlapping of certain clinical and serologic manifestations between SS and RA may indicate that numerous immunologic-related mechanisms are involved in the physiopathology of both these diseases. It is widely accepted that epigenetic pathways play an essential role in the development and function of the immune system. Although many published studies have attempted to elucidate the relation between epigenetic modifications (e.g. DNA methylation, histone post-translational modifications, miRNAs) and autoimmune disorders, the contribution of epigenetic regulation to the pathogenesis of SS and RA is at present poorly understood. This review attempts to shed light from a critical point of view on the identification of the most relevant epigenetic mechanisms related to RA and SS by explaining intricate regulatory processes and phenotypic features of both autoimmune diseases. Moreover, we point out some epigenetic markers which can be used to monitor the inflammation status and the dysregulated immunity in SS and RA. Finally, we discuss the inconvenience of using epigenetic data obtained from bulk immune cell populations instead specific immune cell subpopulations.

Clinical, Cytogenetic, and Molecular Findings in Two Cases of Variant t(8;21) Acute Myeloid Leukemia (AML)

t(8;21)(q22;q22) is present in ~5–10% of patients with de novo acute myeloid leukemia (AML) and is associated with a better overall prognosis. Variants of the t(8;21) have been described in the literature, however, their clinical and prognostic significance has not been well-characterized. Molecular profiling of these cases has not previously been reported but may be useful in better defining the prognosis of this subset of patients. We present two cases of variant t(8;21) AML including clinical, cytogenetic, and molecular data.

Acute myeloid leukemia with t(8;21)(q22;q22.1)/RUNX1-RUNX1T1 and KIT Exon 8 mutation is associated with characteristic mastocytosis and dismal outcomes

KIT mutations are observed in about 20-40% of acute myeloid leukemia with t(8;21)(q22;q22.1)/RUNX1-RUNX1T1 [abbreviated AML t(8;21) here] with mutations involving exon 17 being the most common. Despite high frequencies of KIT mutations in both AML t(8;21) and systemic mastocytosis (SM), AML t(8;21) associated with SM is uncommon, and restricted to KIT exon 17 mutated cases. In this study, we report two cases of AML t(8;21) associated SM that KIT mutation occurred in exon 8 (T417_D419delinsY). In both patients, the bone marrow displayed increased round/ovoid mast cells with bilobated nuclei and absence of CD2 and CD25 expression. RUNX1/RUNX1T1 fusion was shown in both myeloblasts and mast cells by FISH. Patient #1 was refractory to induction chemotherapy and died at day 50; patient #2 had residual AML, marked SM, and persistent RUNX1/RUNX1T1 fusion after induction therapy.

Epigenetic Modifications in Acute Myeloid Leukemia: Prognosis, Treatment, and Heterogeneity

Leukemia, specifically acute myeloid leukemia (AML), is a common malignancy that can be differentiated into multiple subtypes based on leukemogenic history and etiology. Although genetic aberrations, particularly cytogenetic abnormalities and mutations in known oncogenes, play an integral role in AML development, epigenetic processes have been shown as a significant and sometimes independent dynamic in AML pathophysiology. Here, we summarize how tumors evolve and describe AML through an epigenetic lens, including discussions on recent discoveries that include prognostics from epialleles, changes in RNA function for hematopoietic stem cells and the epitranscriptome, and novel epigenetic treatment options. We further describe the limitations of treatment in the context of the high degree of heterogeneity that characterizes acute myeloid leukemia.

Expression levels of the runt-related transcription factor 1 and 3 genes in the development of acute myeloid leukemia

The aim of the present study was to evaluate the mRNA expression level of the runt-related transcription factor 1 (RUNX1) and runt-related transcription factor 3 (RUNX3) genes in patients with acute myeloid leukemia (AML). The etiology of AML is not yet fully known, but certain genetic factors may contribute to its manifestation. The RUNX1 and RUNX3 genes have been demonstrated to serve a role in the transcription process. The group investigated in the present study included 43 patients diagnosed with AML, and the relative RUNX1 and RUNX3 expression levels were determined using reverse transcription-quantitative polymerase chain reaction. The results indicated that RUNX1 and RUNX3 expression was associated with clinicopathological features, including sex and mortality risk. Expression levels of the RUNX1 gene were higher and more variable among females (P=0.044), and mortality was more frequent among patients with a higher RUNX3 expression level (P=0.036). The data obtained from the present study suggested that RUNX3 expression may have potential value as a prognostic factor; furthermore, sex is potentially a factor that may affect the difference in RUNX1 gene expression level among females and males. Further analyses in this field will aid in the identification and elucidation of the molecular basis of leukemia.

Fast Global Phosphoproteome Profiling of Jurkat T Cells by HIFU-TiO2-SCX-LC-MS/MS

We propose a new workflow for fast phosphoproteome profiling. The workflow is based on the use of accelerated in-solution trypsin digestion under an ultrasonic field provided by high-intensity focused ultrasound (HIFU) combined with an inverse strategy based on TiO₂ selective phosphopeptide enrichment, fractionation by strong cation exchange chromatography (SCX) and analysis by liquid chromatography tandem mass spectrometry (LC-MS/MS) using a high-resolution mass spectrometer. The performance of the method was established for the global phosphoproteome analysis of unstimulated human Jurkat leukemia T cells (E6.1). Using this accelerated workflow, 15367 phosphorylation sites from 13029 different phosphopeptides belonging to 3163 different phosphoproteins were efficiently identified with high-throughput and reproducibility in less than 15 h. The functional analysis revealed significant phosphorylation-based networks that are implicated in immune function and tumor development pathways. The present strategy, HIFU-TiO₂-SCX-LC-MS/MS, is the fastest analytical method reported to date for generating large-scale phosphoproteomics data sets (<15 h).

Bleeding is not the main clinical issue in many patients with inherited thrombocytopaenias

Bleeding diathesis has been considered for a long time the main clinical issue impacting the lives of patients affected by inherited thrombocytopaenias. However, the number of known inherited thrombocytopaenias greatly increased in recent years, and careful evaluation of hundreds of patients affected by these 'new' disorders revealed that most of them are at risk of developing additional life-threatening disorders during childhood or adult life. These additional disorders are usually more serious and dangerous than low platelet count. For instance, it is known that mutations in RUNX1, ANKRD26 and ETV6 cause congenital thrombocytopaenia, but we now know that they also predispose to haematological malignancies. Similarly, MYH9 mutations result in congenital thrombocytopaenia and increase the risk of developing kidney failure, cataracts and hearing loss at a later stage, while MPL mutations cause a congenital thrombocytopaenia that almost always evolves into deadly bone marrow failure. Thus, identification of patients with these disorders is essential for evaluation of their prognosis, enabling effective genetic counselling, personalizing follow-up and giving appropriate treatments in case of development of additional diseases. Careful clinical evaluation and peripheral blood film examination are extremely useful tools in guiding the diagnostic process and identifying the candidate genes to be sequenced.

Clinical Relevance of RUNX1 and CBFB Alterations in Acute Myeloid Leukemia and Other Hematological Disorders

The translocation t(8;21), leading to a fusion between the RUNX1 gene and the RUNX1T1 locus, was the first chromosomal translocation identified in cancer. Since the first description of this balanced rearrangement in a patient with acute myeloid leukemia (AML) in 1973, RUNX1 translocations and point mutations have been found in various myeloid and lymphoid neoplasms. In this chapter, we summarize the currently available data on the clinical relevance of core binding factor gene alterations in hematological disorders. In the first section, we discuss the prognostic implications of the core binding factor translocations RUNX1-RUNX1T1 and CBFB-MYH11 in AML patients. We provide an overview of the cooperating genetic events in patients with CBF-rearranged AML and their clinical implications, and review current treatment approaches for CBF AML and the utility of minimal residual disease monitoring. In the next sections, we summarize the available data on rare RUNX1 rearrangements in various hematologic neoplasms and the role of RUNX1 translocations in therapy-related myeloid neoplasia. The final three sections of the chapter cover the spectrum and clinical significance of RUNX1 point mutations in AML and myelodysplastic syndromes, in familial platelet disorder with associated myeloid malignancy, and in acute lymphoblastic leukemia.

Association of the Single Nucleotide Polymorphisms in RUNX1, DYRK1A, and KCNJ15 with Blood Related Traits in Pigs

The aim of this study was to detect positional candidate genes located within the support interval (SI) regions based on the results of red blood cell, mean corpuscular volume (MCV), and mean corpuscular hemoglobin quantitative trait locus (QTL) in Sus scrofa chromosome 13, and to verify the correlation between specific single-nucleotide polymorphisms (SNPs) located in the exonic region of the positional candidate gene and the three genetic traits. The flanking markers of the three QTL SI regions are SW38 and S0215. Within the QTL SI regions, 44 genes were located, and runt-related transcription factor 1, dual-specificity tyrosine-(Y)-phosphorylation regulated kinase 1A (DYRK1A), and potassium inwardly-rectifying channel, subfamily J, member 15 KCNJ15-which are reported to be related to the hematological traits and clinical features of Down syndrome-were selected as positional candidate genes. The ten SNPs located in the exonic region of the three genes were detected by next generation sequencing. A total of 1,232 pigs of an F₂ resource population between Landrace and Korean native pigs were genotyped. To investigate the effects of the three genes on each genotype, a mixed-effect model which is the considering family structure model was used to evaluate the associations between the SNPs and three genetic traits in the F₂ intercross population. Among them, the MCV level was highly significant (nominal p = 9.8×10^-9) in association with the DYRK1A-SNP1 (c.2989 G<A), and explained 4.9% of the phenotypic variance. However, since linkage disequilibrium is quite extensive in an F₂ intercross, our approach has limited power to distinguish one particular positional candidate gene from a QTL region.

Nanomedicine approaches in acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is the malignancy with the highest incidence amongst children (26% of all cancer cases), being surpassed only by the cancers of the brain and of the nervous system. The most recent research on ALL is focusing on new molecular therapies, like targeting specific biological structures in key points in the cell cycle, or using selective inhibitors for transmembranary proteins involved in cell signalling, and even aiming cell surface receptors with specifically designed antibodies for active targeting. Nanomedicine approaches, especially by the use of nanoparticle-based compounds for the delivery of drugs, cancer diagnosis or therapeutics may represent new and modern ways in the near future anti-cancer therapies. This review offers an overview on the recent role of nanomedicine in the detection and treatment of acute lymphoblastic leukemia as resulting from a thorough literature survey. A short introduction on the basics of ALL is presented followed by the description of the conventional methods used in the ALL detection and treatment. We follow our discussion by introducing some of the general nano-strategies used for cancer detection and treatment. The detailed role of organic and inorganic nanoparticles in ALL applications is further presented, with a special focus on gold nanoparticle-based nanocarriers of antileukemic drugs.

Prognosis and monitoring of core-binding factor acute myeloid leukemia: current and emerging factors

Core-binding factor acute myeloid leukemia (CBF-AML) - including AML with t(8;21) and AML with inv(16) - accounts for about 15% of adult AML and is associated with a relatively favorable prognosis. Nonetheless, relapse incidence may reach 40% in these patients. In this context, identification of prognostic markers is considered of great interest. Due to similarities between their molecular and prognostic features, t(8;21) and inv(16)-AML are usually grouped and reported together in clinical studies. However, considerable experimental evidences have highlighted that they represent two distinct entities and should be considered separately for further studies. This review summarizes recent laboratory and clinical findings in this particular subset of AML and how they could be used to improve management of patients in routine practice.

3,3'-diindolylmethane ameliorates experimental autoimmune encephalomyelitis by promoting cell cycle arrest and apoptosis in activated T cells through microRNA signaling pathways

3,3'-Diindolylmethane (DIM) is a naturally derived indole found in cruciferous vegetables that has great potential as a novel and effective therapeutic agent. In the current study, we investigated the effects of DIM post-treatment on the regulation of activated T cells during the development of experimental autoimmune encephalomyelitis (EAE), a murine model of multiple sclerosis. We demonstrated that the administration of DIM 10 days after EAE induction was effective at ameliorating disease parameters, including inflammation and central nervous system cellular infiltration. MicroRNA (miRNA) microarray analysis revealed an altered miRNA profile in brain infiltrating CD4(+) T cells following DIM post-treatment of EAE mice. Additionally, bioinformatics analysis suggested the involvement of DIM-induced miRNAs in pathways and processes that halt cell cycle progression and promote apoptosis. Additional studies confirmed that DIM impacted these cellular processes in activated T cells. Further evidence indicated that DIM treatment significantly upregulated several miRNAs (miR-200c, miR-146a, miR-16, miR-93, and miR-22) in brain CD4(+) T cells during EAE while suppressing their associated target genes. Similarly, we found that overexpression of miR-16 in primary CD4(+) T cells led to significant downregulation of both mRNA and protein levels of cyclin E1 and B-cell lymphoma-2, which play important roles in regulating cell cycle progression and apoptosis. Collectively, these studies demonstrate that DIM post-treatment leads to the amelioration of EAE development by suppressing T-cell responses through the induction of select miRNAs that control cell cycle progression and mediate apoptosis.

Management recommendations for chronic myelomonocytic leukemia: consensus statements from the SIE, SIES, GITMO groups

With the aim of reviewing critical concepts and producing recommendations for the management of chronic myelomonocytic leukemia, key questions were selected according to the criterion of clinical relevance. Recommendations were produced using a Delphi process and four consensus conferences involving a panel of experts appointed by the Italian Society of Hematology and affiliated societies. This report presents the final statements and recommendations, covering patient evaluation at diagnosis, diagnostic criteria, risk classification, first-line therapy, monitoring, second-line therapy and allogeneic stem cell transplantation. For the first-line therapy, the panel recommended that patients with myelodysplastic-type chronic myelomonocytic leukemia and less than 10% blasts in bone marrow should be managed with supportive therapy aimed at correcting cytopenias. In patients with myelodysplastic-type chronic myelomonocytic leukemia with a high number of blasts in bone marrow (≥ 10%), supportive therapy should be integrated with the use of 5-azacytidine. Patients with myeloproliferative-type chronic myelomonocytic leukemia with a low number of blasts (<10%) should be treated with cytoreductive therapy. Hydroxyurea is the drug of choice to control cell proliferation and to reduce organomegaly. Patients with myeloproliferative-type chronic myelomonocytic leukemia, and a high number of blasts should receive polychemotherapy. Both in myelodysplastic-type and myeloproliferative-type chronic myelomonocytic leukemia, allogeneic stem cell transplantation should be offered within clinical trials in selected patients.

Genome-wide DNA methylation patterns in naive CD4+ T cells from patients with primary Sjögren's syndrome

OBJECTIVE

Primary Sjögren's syndrome (SS) is a systemic autoimmune disease with incompletely understood etiology. This study was undertaken to investigate the role of epigenetic dysregulation in the pathogenesis of primary SS.

METHODS

A genome-wide DNA methylation study was performed in naive CD4+ T cells from 11 patients with primary SS compared to age-, sex-, and ethnicity-matched healthy controls. Cytosine methylation was quantified using the Illumina Infinium HumanMethylation450 BeadChip array, and the data were validated using bisulfite sequencing.

RESULTS

Genome-wide analyses identified 553 hypomethylated CpG sites and 200 hypermethylated CpG sites in naive CD4+ T cells from patients with primary SS as compared to healthy controls, representing 311 hypomethylated and 115 hypermethylated gene regions. The hypomethylated genes in patients with primary SS included LTA (encoding lymphotoxin α). Other relevant genes, such as CD247, TNFRSF25, PTPRC, GSTM1, and PDCD1, were also hypomethylated. The interferon signature pathway was represented by hypomethylation of STAT1, IFI44L, USP18, and IFITM1. A group of genes encoding members of the solute carrier proteins were differentially methylated. In addition, the transcription factor gene RUNX1 was hypermethylated in patients with primary SS, suggesting a possible connection to lymphoma predisposition. Gene ontology (GO) analysis of hypomethylated genes demonstrated enrichment of genes involved in lymphocyte activation and immune response. GO terms for hypermethylated genes included antigen processing and presentation.

CONCLUSION

This is the first epigenome-wide DNA methylation study in patients with primary SS. These findings highlight a role for DNA methylation in primary SS and identify disease-associated DNA methylation changes in several genes and pathways in naive CD4+ T cells from patients with primary SS that may be involved in the pathogenesis of this disease.

Lessons in platelet production from inherited thrombocytopenias

Our knowledge of the cellular and molecular mechanisms of platelet production has greatly expanded in recent years due to the opportunity to culture in vitro megakaryocytes and to create transgenic animals with specific genetic defects that interfere with platelet biogenesis. However, in vitro models do not reproduce the complexity of the bone marrow microenvironment where megakaryopoiesis takes place, and experience shows that what is seen in animals does not always happen in humans. So, these experimental models tell us what might happen in humans, but does not assure us that these events really occur. In contrast, inherited thrombocytopenias offer the unique opportunity to verify in humans the actual effects of abnormalities in specific molecules on platelet production. There are currently 20 genes whose defects are known to result in thrombocytopenia and, on this basis, this review tries to outline a model of megakaryopoiesis based on firm evidence. Inherited thrombocytopenias have not yet yielded all the information they can provide, because nearly half of patients have forms that do not fit with any known disorder. So, further investigation of inherited thrombocytopenias will advance not only the knowledge of human illnesses, but also our understanding of human platelet production.

A systematic analysis of a mi-RNA inter-pathway regulatory motif

BACKGROUND

The continuing discovery of new types and functions of small non-coding RNAs is suggesting the presence of regulatory mechanisms far more complex than the ones currently used to study and design Gene Regulatory Networks. Just focusing on the roles of micro RNAs (miRNAs), they have been found to be part of several intra-pathway regulatory motifs. However, inter-pathway regulatory mechanisms have been often neglected and require further investigation.

RESULTS

In this paper we present the result of a systems biology study aimed at analyzing a high-level inter-pathway regulatory motif called Pathway Protection Loop, not previously described, in which miRNAs seem to play a crucial role in the successful behavior and activation of a pathway. Through the automatic analysis of a large set of public available databases, we found statistical evidence that this inter-pathway regulatory motif is very common in several classes of KEGG Homo Sapiens pathways and concurs in creating a complex regulatory network involving several pathways connected by this specific motif. The role of this motif seems also confirmed by a deeper review of other research activities on selected representative pathways.

CONCLUSIONS

Although previous studies suggested transcriptional regulation mechanism at the pathway level such as the Pathway Protection Loop, a high-level analysis like the one proposed in this paper is still missing. The understanding of higher-level regulatory motifs could, as instance, lead to new approaches in the identification of therapeutic targets because it could unveil new and "indirect" paths to activate or silence a target pathway. However, a lot of work still needs to be done to better uncover this high-level inter-pathway regulation including enlarging the analysis to other small non-coding RNA molecules.

Cell-autonomous function of Runx1 transcriptionally regulates mouse megakaryocytic maturation

RUNX1 transcription factor (TF) is a key regulator of megakaryocytic development and when mutated is associated with familial platelet disorder and predisposition to acute myeloid leukemia (FPD-AML). We used mice lacking Runx1 specifically in megakaryocytes (MK) to characterized Runx1-mediated transcriptional program during advanced stages of MK differentiation. Gene expression and chromatin-immunoprecipitation-sequencing (ChIP-seq) of Runx1 and p300 identified functional Runx1 bound MK enhancers. Runx1/p300 co-bound regions showed significant enrichment in genes important for MK and platelet homeostasis. Runx1 occupied genomic regions were highly enriched in RUNX and ETS motifs and to a lesser extent in GATA motif. Megakaryocytic specificity of Runx1/P300 bound enhancers was validated by transfection mutagenesis and Runx1/P300 co-bound regions of two key megakaryocytic genes Nfe2 and Selp were tested by in vivo transgenesis. The data provides the first example of genome wide Runx1/p300 occupancy in maturating primary FL-MK, unravel the Runx1-regulated program controlling MK maturation in vivo and identify a subset of its bona fide regulated genes. It advances our understanding of the molecular events that upon RUNX1mutations in human lead to the predisposition to familial platelet disorders and FPD-AML.

Spliceosome mutations involving SRSF2, SF3B1, and U2AF35 in chronic myelomonocytic leukemia: prevalence, clinical correlates, and prognostic relevance

SRSF2, SF3B1, and U2AF35 (U2AF1) are the three most frequent genes involved with spliceosome mutations in myeloid malignancies. SF3B1 mutations are most frequent (~80%) in myelodysplastic syndromes (MDS) with ring sideroblasts (RS) but lack prognostic relevance. SRSF2 mutations are associated with shortened overall (OS) and leukemia-free survival (LFS) in both MDS and myelofibrosis. In this study of 226 patients with chronic myelomonocytic leukemia (CMML), mutational frequencies were 40% for SRSF2 (all affecting P95), 6% for SF3B1 (primarily K700E) and 9% for U2AF35 (mostly S34F and Q157P/R). These mutations were mutually exclusive and 54% of the patients displayed at least one mutation. The three mutation groups were phenotypically similar, with the exception of higher RS% (P < 0.0001) in patients with SF3B1 mutations. At a median follow-up of 15 months, 176 (78%) deaths and 32 (14%) leukemic transformations were documented. OS (median survivals of 17, 16, 17, and 20 months; P = 0.48) and LFS (leukemic transformation rates of 17, 13, 15, and 5%; P = 0.63) were similar among patients with none of the three mutations, SRSF2, SF3B1, or U2AF35 mutations, respectively. We conclude that SRSF2 is the most frequently mutated spliceosome gene in CMML but neither it nor SF3B1 or U2AF35 mutations are prognostically relevant.

SRSF2 mutations in 275 cases with chronic myelomonocytic leukemia (CMML)

We analyzed the mutational hotspot region of SRSF2 (Pro95) in 275 cases with chronic myelomonocytic leukemia (CMML). In addition, ASXL1, CBL, EZH2, JAK2V617F, KRAS, NRAS, RUNX1, and TET2 mutations were investigated in subcohorts. Mutations in SRSF2 (SRSF2mut) were detected in 47% (129 of 275) of all cases. In detail, 120 cases had a missense mutation at Pro95, leading to a change to Pro95His, Pro95Leu, Pro95Arg, Pro95Ala, or Pro95Thr. In 9 cases, 3 new in/del mutations were observed: 7 cases with a 24-bp deletion, 1 case with a 3-bp duplication, and 1 case with a 24-bp duplication. In silico analyses predicted a damaging character for the protein structure of SRSF2 for all mutations. SRSF2mut was correlated with higher age, less pronounced anemia, and normal karyotype. SRSF2mut and EZH2mut were mutually exclusive, but SRSF2mut was associated with TET2mut. In the total cohort, no effect of SRSF2mut on survival was observed. However, in the RUNX1mut subcohort, SRSF2 Pro95His had a favorable effect on overall survival. This comprehensive mutation analysis found that 93% of all patients with CMML carried at least 1 somatic mutation in 9 recurrently mutated genes. In conclusion, these data show the importance of SRSF2mut as new diagnostic marker in CMML.

Familial myelodysplastic syndromes: a review of the literature

Familial cases of myelodysplastic syndromes are rare, but are immensely valuable for the investigation of the molecular pathogenesis of myelodysplasia in general. The best-characterized familial myelodysplastic syndrome is that of familial platelet disorder with propensity to myeloid malignancy, caused by heterozygous germline RUNX1 mutations. Recently, there has been an increase in the number of reported cases, allowing for better understanding of the incidence, clinical features, and pathogenesis of this disorder. These recent cases have highlighted the clinical variability of the disorder and confirmed that many patients lack a bleeding and/or thrombocytopenia history. Additionally, several cases of T-acute lymphoblastic leukemia have now been reported, confirming a risk of lymphoid leukemia in patients with inherited RUNX1 mutations. Furthermore, an increased awareness of clinicians has helped detect a number of additional families affected by inherited myelodysplastic syndromes, resulting in the identification of novel causative mechanisms of disease, such as RUNX1 deficiency resulting from constitutional microdeletions of 21q22 and myelodysplasia-associated with telomerase deficiency. Awareness of predisposition to myelodysplastic syndromes and acute myeloid leukemia in families may be of critical importance in the management of younger patients with myelodysplasia in whom allogeneic hematopoietic stem cell transplantation is considered. Such families should be investigated for inherited deficiencies of RUNX1 and/or telomerase to prevent the use of an affected sibling as a donor for transplantation. Here we provide an update on familial platelet disorder in addition to a review of other known familial myelodysplastic syndromes.

Down-regulation of microRNAs 222/221 in acute myelogenous leukemia with deranged core-binding factor subunits

Core-binding factor leukemia (CBFL) is a subgroup of acute myeloid leukemia (AML) characterized by genetic mutations involving the subunits of the core-binding factor (CBF). The leukemogenesis model for CBFL posits that one, or more, gene mutations inducing increased cell proliferation and/or inhibition of apoptosis cooperate with CBF mutations for leukemia development. One of the most common mutations associated with CBF mutations involves the KIT receptor. A high expression of KIT is a hallmark of a high proportion of CBFL. Previous studies indicate that microRNA (MIR) 222/221 targets the 3' untranslated region of the KIT messenger RNA and our observation that AML1 can bind the MIR-222/221 promoter, we hypothesized that MIR-222/221 represents the link between CBF and KIT. Here, we show that MIR-222/221 expression is upregulated after myeloid differentiation of normal bone marrow AC133(+) stem progenitor cells. CBFL blasts with either t(8;21) or inv(16) CBF rearrangements with high expression levels of KIT (CD117) display a significantly lower level of MIR-222/221 expression than non-CBFL blasts. Consistently, we found that the t(8;21) AML1-MTG8 fusion protein binds the MIR-222/221 promoter and induces transcriptional repression of a MIR-222/221-LUC reporter. Because of the highly conserved sequence homology, we demonstrated concomitant MIR-222/221 down-regulation and KIT up-regulation in the 32D/WT1 mouse cell model carrying the AML1-MTG16 fusion protein. This study provides the first hint that CBFL-associated fusion proteins may lead to up-regulation of the KIT receptor by down-regulating MIR-222/221, thus explaining the concomitant occurrence of CBF genetic rearrangements and overexpression of wild type or mutant KIT in AML.

Dynamic combinatorial interactions of RUNX1 and cooperating partners regulates megakaryocytic differentiation in cell line models

Specific interactions of transcription factors (TFs) with their targets are crucial for specifying gene expression programs during cell differentiation. How specificity is maintained despite limited selectivity of individual TF-DNA interactions is not fully understood. RUNX1 TF is among the most frequently mutated genes in human leukemia and an important regulator of megakaryopoiesis. We used megakaryocytic cell lines to characterize the network of RUNX1 targets and cooperating TFs in differentiating megakaryocytes and demonstrated how dynamic partnerships between RUNX1 and cooperating TFs facilitated regulatory plasticity and specificity during this process. After differentiation onset, RUNX1 directly activated a large number of genes through interaction with preexisting and de novo binding sites. Recruitment of RUNX1 to de novo occupied sites occurred at H3K4me1-marked preprogrammed enhancers. A significant number of these de novo bound sites lacked RUNX motif but were occupied by AP-1 TFs. Reciprocally, AP-1 TFs were up-regulated by RUNX1 after 12-O-tetradecanoylphorbol-13-acetate induction and recruited to RUNX1-occupied sites lacking AP-1 motifs. At other differentiation stages, additional combinatorial interactions occurred between RUNX1 and its coregulators, GATA1 and ETS. The findings suggest that in differentiating megakaryocytic cell lines, RUNX1 cooperates with GATA1, AP-1, and ETS to orchestrate cell-specific transcription programs through dynamic TF partnerships.

A family harboring a germ-line N-terminal C/EBPalpha mutation and development of acute myeloid leukemia with an additional somatic C-terminal C/EBPalpha mutation

C/EBPalpha plays an essential role as a transcription factor in myeloid cell differentiation. Here, we describe a Japanese family in which two individuals with acute myeloid leukemia (AML) and one healthy individual had an identical 4-base pair insertion in the N-terminal region of CEBPA (350_351insCTAC), resulting in the termination at codon 107 (I68fsX107). The father and a son at diagnosis of AML had different in-frame insertion mutations in the C-terminal region of C/EBPalpha. These C-terminal mutations disappeared upon remission in both patients. Interestingly, the father showed different in-frame insertion mutations in the C-terminal CEBPA at the time of diagnosis and relapse. These data strongly suggest that the N-terminal C/EBPalpha mutation predisposes to the occurrence of a C-terminal C/EBPalpha mutation as a secondary genetic hit, causing AML.

Comparative analysis of protein-protein interactions in cancer-associated genes

Protein-protein interactions (PPIs) have been widely studied to understand the biological processes or molecular functions associated with different disease systems like cancer. While focused studies on individual cancers have generated valuable information, global and comparative analysis of datasets from different cancer types has not been done. In this work, we carried out bioinformatic analysis of PPIs corresponding to differentially expressed genes from microarrays of various tumor tissues (belonging to bladder, colon, kidney and thyroid cancers) and compared their associated biological processes and molecular functions (based on Gene Ontology terms). We identified a set of processes or functions that are common to all these cancers, as well as those that are specific to only one or partial cancer types. Similarly, protein interaction networks in nucleic acid metabolism were compared to identify the common/specific clusters of proteins across different cancer types. Our results provide a basis for further experimental investigations to study protein interaction networks associated with cancer. The methodology developed in this work can also be applied to study similar disease systems.

Stem cell exhaustion and leukemogenesis

Cancer is the result of a combination of genetic alterations, which aid transformation of cells. However, oncogenic alterations also simultaneously induce some detrimental effects on the cells such as apoptosis, senescence, and differentiation. Such negative effects caused by certain oncogenic events are overcome by other cooperating genetic hits. We propose stem cell exhaustion as a novel detrimental effect that is caused by a wide variety of oncogenic alterations. Interestingly, in most cases, the stem cell exhaustion due to oncogenic alterations is preceded by an abnormal expansion of stem/progenitor cells. This preceding stem/progenitor cell expansion may be a key feature that still promotes cancer development, along with cooperating hits that rescue stem cell exhaustion. This review summarizes current knowledge about hematopoietic stem cell exhaustion and the mechanisms to overcome stem cell exhaustion in cancer development.

Runx1 promotes B-cell survival and lymphoma development

Runx1 is essential for the homeostatic control of normal hematopoiesis and is required for lymphoid development. Translocations or point mutations that result in RUNX1 loss or disrupted function predispose to leukemia but data derived from model systems suggests that Runx genes can also be pro-oncogenic. Here we investigate the effects of enforced Runx1 expression in lymphoid lineages both in vivo and in vitro and show that transgene expression enhanced cell survival in the thymus and bone marrow but strongly inhibited the expansion of hematopoietic and B cell progenitors in vitro. Despite this, modestly enhanced levels of Runx1 accelerated Myc-induced lymphomagenesis in both the B cell and T cell lineages. Together these data provide formal proof that wild type Runx1 can promote oncogenesis in lymphoid tissues and that, in addition to loss of function, gain of function may have an aetiological role in leukemia.

Systemic mastocytosis associated with t(8;21)(q22;q22) acute myeloid leukemia

Although KIT mutations are present in 20–25% of cases of t(8;21)(q22;q22) acute myeloid leukemia (AML), concurrent development of systemic mastocytosis (SM) is exceedingly rare. We examined the clinicopathologic features of SM associated with t(8;21)(q22;q22) AML in ten patients (six from our institutions and four from published literature) with t(8;21) AML and SM. In the majority of these cases, a definitive diagnosis of SM was made after chemotherapy, when the mast cell infiltrates were prominent. Deletion 9q was an additional cytogenetic abnormality in four cases. Four of the ten patients failed to achieve remission after standard chemotherapy and seven of the ten patients have died of AML. In the two patients who achieved durable remission after allogeneic hematopoietic stem cell transplant, recipient-derived neoplastic bone marrow mast cells persisted despite leukemic remission. SM associated with t(8;21) AML carries a dismal prognosis; therefore, detection of concurrent SM at diagnosis of t(8;21) AML has important prognostic implications.

RUNX1 gene mutation in primary myelodysplastic syndrome--the mutation can be detected early at diagnosis or acquired during disease progression and is associated with poor outcome

Mutations of Runt-related transcription factor 1 (RUNX1) have been detected in patients with myelodysplastic syndrome (MDS). However, the prognostic implication of RUNX1 mutations in primary MDS is limited. The stage of the disease at which the mutations are acquired and whether they persist during the disease course also remain unclear. We analysed mutations of RUNX1 exons 3-8 in 132 patients with primary MDS and correlated the results with clinical features. Serial studies were performed during the follow-up period. Sixteen patients (12%) had RUNX1 mutations at the time of diagnosis. All RUNX1 mutations that were detected at diagnosis remained unchanged during the clinical course. Two other patients acquired RUNX1 mutations at leukaemic transformation 34 months and 35 months after the diagnosis of MDS. Patients with RUNX1 mutations at diagnosis had higher neutrophil counts and higher frequency of -7/7q deletion than those without. Furthermore, RUNX1 mutation was closely associated with a short overall survival (P = 0.039). This is the first report to demonstrate that RUNX1 mutation can not only be detected early at diagnosis but also acquired during disease progression and is associated with poor prognosis in patients with primary MDS. It may play a role in the development and progression of a subset of primary MDS.

Segregation of megakaryocytic or erythroid cells from a megakaryocytic leukemia cell line (JAS-R) by adhesion during culture

Adhesion is one of the important biologic characteristics of leukemic cells. We previously reported a new megakaryocytic-erythroid cell line, JAS-R. In this study, JAS-R cells were segregated into two types by the differences of attachment to culture dishes. One type (designated as JAS-RAD cells) adhered to the substratum of the culture dishes, while the other (JAS-REN cells) grew as a single-cell suspension. Adhesion of JAS-RAD was inhibited by treatment with RGDS oligopeptide. Flow cytometric analysis revealed that JAS-RAD cells had high expression of CD41a and CD61 versus low CD235a expression, and JAS-REN showed low expression of CD41a, and CD61, and high CD235a. The two phenotypes were reciprocally exchangeable by selecting adherent or suspended cells from each type of culture. Microarray analysis and RT-PCR revealed that JAS-RAD cells expressed four major alpha-granule genes and JAS-REN cells expressed beta-globin. Interestingly, erythropoietin was only secreted by JAS-RAD cells. With regard to transcription factors, it was shown that GFI1, FLI1 and RUNX1 were strongly expressed in JAS-RAD cells while GATA1, FOG1 and NFE2 were equally expressed by both types. These findings indicate that adhesion via integrins is related to the phenotypic shift of JAS-R cells between megakaryocytic and erythroid lineages.

A highly conserved regulatory element controls hematopoietic expression of GATA-2 in zebrafish

Background

GATA-2 is a transcription factor required for hematopoietic stem cell survival as well as for neuronal development in vertebrates. It has been shown that specific expression of GATA-2 in blood progenitor cells requires distal cis-acting regulatory elements. Identification and characterization of these elements should help elucidating transcription regulatory mechanisms of GATA-2 expression in hematopoietic lineage.

Results

By pair-wise alignments of the zebrafish genomic sequences flanking GATA-2 to orthologous regions of fugu, mouse, rat and human genomes, we identified three highly conserved non-coding sequences in the genomic region flanking GATA-2, two upstream of GATA-2 and another downstream. Using both transposon and bacterial artificial chromosome mediated germline transgenic zebrafish analyses, one of the sequences was established as necessary and sufficient to direct hematopoietic GFP expression in a manner that recapitulates that of GATA-2. In addition, we demonstrated that this element has enhancer activity in mammalian myeloid leukemia cell lines, thus validating its functional conservation among vertebrate species. Further analysis of potential transcription factor binding sites suggested that integrity of the putative HOXA3 and LMO2 sites is required for regulating GATA-2/GFP hematopoietic expression.

Conclusion

Regulation of GATA-2 expression in hematopoietic cells is likely conserved among vertebrate animals. The integrated approach described here, drawing on embryological, transgenesis and computational methods, should be generally applicable to analyze tissue-specific gene regulation involving distal DNA cis-acting elements.

Expression of AML/Runx and ETO/MTG family members during hematopoietic differentiation of embryonic stem cells

Runx1/AML1 plays important roles in hematopoiesis, including the commitment of cells to hematopoiesis during embryonic development, and in the maintenance of hematopoietic cell populations. It is also one of the most common genes involved in chromosomal translocations related to leukemia. One such translocation is t(8;21), which fuses the Runx1 gene to the MTG8/ETO gene and generates the Runx1-MTG8 (AML1-ETO) fusion gene. Both Runx1 and MTG8 have two additional family members that are much less studied in hematopoiesis. Here we report the expression of every member of the Runx and MTG families as well as the Runx heterodimerization partner CBFbeta during hematopoietic differentiation of murine embryonic stem cells. We observed substantially increased expression of Runx1, Runx2, and MTG16 during hematopoietic differentiation. Furthermore, the increase in Runx2 expression is delayed relative to Runx1 expression, suggesting their possible sequential contribution to hematopoiesis.

Concurrent transcriptional deregulation of AML1/RUNX1 and GATA factors by the AML1-TRPS1 chimeric gene in t(8;21)(q24;q22) acute myeloid leukemia

The Runt domain transcription factor AML1/RUNX1 is essential for the generation of hematopoietic stem cells and is the most frequent target of chromosomal translocations associated with leukemia. Here, we present a new AML1 translocation found in a patient with acute myeloid leukemia M4 with t(8;21)(q24;q22) at the time of relapse. This translocation generated an in-frame chimeric gene consisting of the N-terminal portion of AML1, retaining the Runt domain, fused to the entire length of TRPS1 on the C-terminus. TRPS1 encodes a putative multitype zinc finger (ZF) protein containing 9 C2H2 type ZFs and 1 GATA type ZF. AML1-TRPS1 stimulated proliferation of hematopoietic colony-forming cells and repressed the transcriptional activity of AML1 and GATA-1 by 2 different mechanisms: competition at their cognate DNA-binding sites and physical sequestrations of AML1 and GATA-1, suggesting that simultaneous deregulation of AML1 and GATA factors constitutes a basis for leukemogenesis.

RUNX1 suppression induces megakaryocytic differentiation of UT-7/GM cells

The transcription factor RUNX1 plays a crucial role in hematopoiesis. RUNX1 regulates both differentiation and proliferation of hematopoietic cells. Several reports have shown that RUNX1 participates in megakaryopoiesis, which is a process that leads to formation of platelets. However, to date, the mechanisms by which this occurs have not been fully elucidated. In the present study, we investigated whether siRNA-mediated depletion of RUNX1 affected megakaryopoiesis of UT-7/GM cells. The depletion of RUNX1 in UT-7/GM cells resulted in up-regulation of the expression of megakaryocytic markers and polyploidization, while cell proliferation was down-regulated. Furthermore, the overexpression of RUNX1 decreased the activity of megakaryocytic gene promoters. These results suggest that RUNX1 down-regulates terminal differentiation of megakaryocytes and promotes proliferation of megakaryocytic progenitors.

Mutations in the receptor tyrosine kinase pathway are associated with clinical outcome in patients with acute myeloblastic leukemia harboring t(8;21)(q22;q22)

AML1-MTG8 generated by t(8;21) contributes to leukemic transformation, but additional events are required for full leukemogenesis. We examined whether mutations in the receptor tyrosine kinase (RTK) pathway could be the genetic events that cause acute myeloblastic leukemia (AML) harboring t(8;21). Mutations in the second tyrosine kinase domain, juxtamembrane (JM) domain and exon 8 of the C-KIT gene were observed in 10, one and three of 37 AML patients with t(8;21), respectively. Three patients showed an internal tandem duplication in the JM domain of the FLT3 gene. One patient had a mutation in the K-Ras gene at codon 12. As the occurrence of these mutations was mutually exclusive, a total of 18 (49%) patients showed mutations in the RTK pathway. These results suggest that activating mutations in the RTK pathway play a role in part as an additional event leading to the development of t(8;21) AML. The 6-year cumulative incidence of relapse in patients with RTK pathway mutations was 79.8%, compared with 13.5% in patients lacking such mutations (P=0.0029). Furthermore, the 6-year relapse-free survival in patients with mutations was 18% compared to 60% in those without mutations (P=0.0340), indicating that RTK mutations are associated with the clinical outcome in t(8;21) AML.