Molecular Taxonomy of Myelodysplastic Syndromes and its Clinical Implications.

Myelodysplastic syndromes/neoplasms (MDS) are clonal hematologic disorders characterized by morphologic abnormalities of myeloid cells and peripheral cytopenias. While genetic abnormalities underlie the pathogenesis of these disorders and their heterogeneity, current classifications of MDS rely predominantly on morphology. We performed genomic profiling of 3,233 patients with MDS or related disorders to delineate molecular subtypes and define their clinical implications. Gene mutations, copy-number alterations (CNAs), and copy-neutral loss of heterozygosity (cnLOH) were derived from targeted sequencing of a 152-gene panel, with abnormalities identified in 91, 43, and 11% of patients, respectively. We characterized 16 molecular groups, encompassing 86% of patients, using information from 21 genes, 6 cytogenetic events, and LOH at the TP53 and TET2 loci. Two residual groups defined by negative findings (molecularly not-otherwise specified, absence of recurrent drivers) comprised 14% of patients. The groups varied in size from 0.5% to 14% of patients and were associated with distinct clinical phenotypes and outcomes. The median bone marrow blast percentage across groups ranged from 1.5 to 10%, and the median overall survival from 0.9 to 8.2 years. We validated 5 well-characterized entities, added further evidence to support 3 previously reported subsets, and described 8 novel groups. The prognostic influence of bone marrow blasts depended on the genetic subtypes. Within genetic subgroups, therapy-related MDS and myelodysplastic/myeloproliferative neoplasms (MDS/MPN) had comparable clinical and outcome profiles to primary MDS. In conclusion, genetically-derived subgroups of MDS are clinically relevant and may inform future classification schemas and translational therapeutic research.

Molecular and clinical presentation of UBA1-mutated myelodysplastic syndromes.

Mutations in UBA1, which are disease-defining for VEXAS syndrome, have been reported in patients diagnosed with myelodysplastic syndromes (MDS). Here, we define the prevalence and clinical associations of UBA1 mutations in a representative cohort of patients with MDS. Digital droplet PCR profiling of a selected cohort of 375 male patients lacking MDS disease-defining mutations or established WHO disease classification identified 28 patients (7%) with UBA1 p.M41T/V/L mutations. Using targeted sequencing of UBA1 in a representative MDS cohort (n=2,027), we identified an additional 27 variants in 26 patients (1%), which we classified as likely/pathogenic (n=12) and unknown significance (n=15). Among the total 40 patients with likely/pathogenic variants (2%), all were male and 63% were classified by WHO2016 as MDS-MLD/SLD. Patients had a median of one additional myeloid gene mutation, often in TET2 (n=12), DNMT3A (n=10), ASXL1 (n=3), or SF3B1 (n=3). Retrospective clinical review where possible showed that 83% (28/34) UBA1-mutant cases had VEXAS-associated diagnoses or inflammatory clinical presentation. The prevalence of UBA1-mutations in MDS patients argues for systematic screening for UBA1 in the management of MDS.

Recent advances in the application of induced pluripotent stem cell technology to the study of myeloid malignancies.

Acquired myeloid malignancies are a spectrum of clonal disorders known to be caused by sequential acquisition of genetic lesions in hematopoietic stem and progenitor cells, leading to their aberrant self-renewal and differentiation. The increasing use of induced pluripotent stem cell (iPSC) technology to study myeloid malignancies has helped usher a paradigm shift in approaches to disease modeling and drug discovery, especially when combined with gene-editing technology. The process of reprogramming allows for the capture of the diversity of genetic lesions and mutational burden found in primary patient samples into individual stable iPSC lines. Patient-derived iPSC lines, owing to their self-renewal and differentiation capacity, can thus be a homogenous source of disease relevant material that allow for the study of disease pathogenesis using various functional read-outs. Furthermore, genome editing technologies like CRISPR/Cas9 enable the study of the stepwise progression from normal to malignant hematopoiesis through the introduction of specific driver mutations, individually or in combination, to create isogenic lines for comparison. In this review, we survey the current use of iPSCs to model acquired myeloid malignancies including myelodysplastic syndromes (MDS), myeloproliferative neoplasms (MPN), acute myeloid leukemia and MDS/MPN overlap syndromes. The use of iPSCs has enabled the interrogation of the underlying mechanism of initiation and progression driving these diseases. It has also made drug testing, repurposing, and the discovery of novel therapies for these diseases possible in a high throughput setting.

Ribosomal protein control of hematopoietic stem cell transformation through direct, non-canonical regulation of metabolism.

We report here that expression of the ribosomal protein, RPL22, is frequently reduced in human myelodysplastic syndrome (MDS) and acute myelogenous leukemia (AML); reduced RPL22 expression is associated with worse outcomes. Mice null for Rpl22 display characteristics of an MDS-like syndrome and develop leukemia at an accelerated rate. Rpl22-deficient mice also display enhanced hematopoietic stem cell (HSC) self-renewal and obstructed differentiation potential, which arises not from reduced protein synthesis but from increased expression of the Rpl22 target, ALOX12, an upstream regulator of fatty acid oxidation (FAO). The increased FAO mediated by Rpl22-deficiency also persists in leukemia cells and promotes their survival. Altogether, these findings reveal that Rpl22 insufficiency enhances the leukemia potential of HSC via non-canonical de-repression of its target, ALOX12, which enhances FAO, a process that may serve as a therapeutic vulnerability of Rpl22 low MDS and AML leukemia cells. Highlights: RPL22 insufficiency is observed in MDS/AML and is associated with reduced survivalRpl22-deficiency produces an MDS-like syndrome and facilitates leukemogenesisRpl22-deficiency does not impair global protein synthesis by HSCRpl22 controls leukemia cell survival by non-canonical regulation of lipid oxidation eTOC: Rpl22 controls the function and transformation potential of hematopoietic stem cells through effects on ALOX12 expression, a regulator of fatty acid oxidation.

A miRNA screening identifies miR-192-5p as associated with response to azacitidine and lenalidomide therapy in myelodysplastic syndromes.

BACKGROUND: miRNAs are small non-coding RNAs that regulate gene expression and are linked to cancer development and progression. miRNA profiles are currently studied as new prognostic factors or therapeutic perspectives. Among hematological cancers, myelodysplastic syndromes at higher risk of evolution into acute myeloid leukemia are treated with hypomethylating agents, like azacitidine, alone or in combination with other drugs, such as lenalidomide. Recent data showed that, during azacitidine and lenalidomide therapy, the concurrent acquisition of specific point mutations affecting inositide signalling pathways is associated with lack or loss of response to therapy. As these molecules are implicated in epigenetic processes, possibly involving miRNA regulation, and in leukemic progression, through the regulation of proliferation, differentiation and apoptosis, here we performed a new miRNA expression analysis of 26 high-risk patients with myelodysplastic syndromes treated with azacitidine and lenalidomide at baseline and during therapy. miRNA array data were processed, and bioinformatic results were correlated with clinical outcome to investigate the translational relevance of selected miRNAs, while the relationship between selected miRNAs and specific molecules was experimentally tested and proven. RESULTS: Patients' overall response rate was 76.9% (20/26 cases): complete remission (5/26, 19.2%), partial remission (1/26, 3.8%), marrow complete remission (2/26, 7.7%), hematologic improvement (6/26, 23.1%), hematologic improvement with marrow complete remission (6/26, 23.1%), whereas 6/26 patients (23.1%) had a stable disease. miRNA paired analysis showed a statistically significant up-regulation of miR-192-5p after 4 cycles of therapy (vs baseline), that was confirmed by real-time PCR analyses, along with an involvement of BCL2, that was proven to be a miR-192-5p target in hematopoietic cells by luciferase assays. Furthermore, Kaplan-Meier analyses showed a significant correlation between high levels of miR-192-5p after 4 cycles of therapy and overall survival or leukemia-free survival, that was stronger in responders, as compared with patients early losing response and non-responders. CONCLUSIONS: This study shows that high levels of miR-192-5p are associated with higher overall survival and leukemia-free survival in myelodysplastic syndromes responding to azacitidine and lenalidomide. Moreover, miR-192-5p specifically targets and inhibits BCL2, possibly regulating proliferation and apoptosis and leading to the identification of new therapeutic targets.

Splicing factor mutations in the myelodysplastic syndromes: Role of key aberrantly spliced genes in disease pathophysiology and treatment.

Mutations of splicing factor genes (including SF3B1, SRSF2, U2AF1 and ZRSR2) occur in more than half of all patients with myelodysplastic syndromes (MDS), a heterogeneous group of myeloid neoplasms. Splicing factor mutations lead to aberrant pre-mRNA splicing of many genes, some of which have been shown in functional studies to impact on hematopoiesis and to contribute to the MDS phenotype. This clearly demonstrates that impaired spliceosome function plays an important role in MDS pathophysiology. Recent studies that harnessed the power of induced pluripotent stem cell (iPSC) and CRISPR/Cas9 gene editing technologies to generate new iPSC-based models of splicing factor mutant MDS, have further illuminated the role of key downstream target genes. The aberrantly spliced genes and the dysregulated pathways associated with splicing factor mutations in MDS represent potential new therapeutic targets. Emerging data has shown that IRAK4 is aberrantly spliced in SF3B1 and U2AF1 mutant MDS, leading to hyperactivation of NF-κB signaling. Pharmacological inhibition of IRAK4 has shown efficacy in pre-clinical studies and in MDS clinical trials, with higher response rates in patients with splicing factor mutations. Our increasing knowledge of the effects of splicing factor mutations in MDS is leading to the development of new treatments that may benefit patients harboring these mutations.

Activation of targetable inflammatory immune signaling is seen in myelodysplastic syndromes with SF3B1 mutations.

Background: Mutations in the SF3B1 splicing factor are commonly seen in myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML), yet the specific oncogenic pathways activated by mis-splicing have not been fully elucidated. Inflammatory immune pathways have been shown to play roles in the pathogenesis of MDS, though the exact mechanisms of their activation in splicing mutant cases are not well understood. Methods: RNA-seq data from SF3B1 mutant samples was analyzed and functional roles of interleukin-1 receptor-associated kinase 4 (IRAK4) isoforms were determined. Efficacy of IRAK4 inhibition was evaluated in preclinical models of MDS/AML. Results: RNA-seq splicing analysis of SF3B1 mutant MDS samples revealed retention of full-length exon 6 of IRAK4, a critical downstream mediator that links the Myddosome to inflammatory NF-kB activation. Exon 6 retention leads to a longer isoform, encoding a protein (IRAK4-long) that contains the entire death domain and kinase domain, leading to maximal activation of NF-kB. Cells with wild-type SF3B1 contain smaller IRAK4 isoforms that are targeted for proteasomal degradation. Expression of IRAK4-long in SF3B1 mutant cells induces TRAF6 activation leading to K63-linked ubiquitination of CDK2, associated with a block in hematopoietic differentiation. Inhibition of IRAK4 with CA-4948, leads to reduction in NF-kB activation, inflammatory cytokine production, enhanced myeloid differentiation in vitro and reduced leukemic growth in xenograft models. Conclusions: SF3B1 mutation leads to expression of a therapeutically targetable, longer, oncogenic IRAK4 isoform in AML/MDS models. Funding: This work was supported by Cincinnati Children's Hospital Research Foundation, Leukemia Lymphoma Society, and National Institute of Health (R35HL135787, RO1HL111103, RO1DK102759, RO1HL114582), Gabrielle's Angel Foundation for Cancer Research, and Edward P. Evans Foundation grants to DTS. AV is supported by Edward P. Evans Foundation, National Institute of Health (R01HL150832, R01HL139487, R01CA275007), Leukemia and Lymphoma Society, Curis and a gift from the Jane and Myles P. Dempsey family. AP and JB are supported by Blood Cancer UK (grants 13042 and 19004). GC is supported by a training grant from NYSTEM. We acknowledge support of this research from The Einstein Training Program in Stem Cell Research from the Empire State Stem Cell Fund through New York State Department of Health Contract C34874GG. MS is supported by a National Institute of Health Research Training and Career Development Grant (F31HL132420).

Genes contain blocks of code that tell cells how to make each part of a protein. Between these blocks are sections of linking DNA, which cells remove when they are preparing to use their genes. Scientists call this process 'splicing'. Cells can splice some genes in more than one way, allowing them to make different proteins from the same genetic code. Mutations that affect the splicing process can change the way cells make their proteins, leading to disease. For example, the myelodysplastic syndromes are a group of blood cancers often caused by mutations in splicing proteins, such as SF3B1. The disorder stops blood cells from maturing and causes abnormal inflammation. So far, the link between splicing, blood cell immaturity, inflammation and cancer is not clear. To find out more, Choudhary, Pellagatti et al. looked at the spliced genetic code from people with myelodysplastic syndromes. Mutations in the splicing protein SF3B1 changed the way cells spliced an important signalling molecule known as IRAK4. Affected cells cut out less genetic code and made a longer version of this signalling protein, named IRAK4-Long. This altered protein activated inflammation and stopped blood cells from maturing. Blocking IRAK4-Long reversed the effects. It also reduced tumour formation in mice carrying affected human cells. The molecule used to block IRAK4, CA-4948 ­ also known as Emavusertib ­ is currently being evaluated in clinical trials for myelodysplastic syndromes and other types of blood cancer. The work of Choudhary, Pellagatti et al. could help scientists to design genetic tests to predict which patients might benefit from this treatment.

Pathophysiologic and clinical implications of molecular profiles resultant from deletion 5q.

BACKGROUND: Haploinsufficiency (HI) resulting from deletion of the long arm of chromosome 5 [del(5q)] and the accompanied loss of heterozygosity are likely key pathogenic factors in del(5q) myeloid neoplasia (MN) although the consequences of del(5q) have not been yet clarified. METHODS: Here, we explored mutations, gene expression and clinical phenotypes of 388 del(5q) vs. 841 diploid cases with MN [82% myelodysplastic syndromes (MDS)]. FINDINGS: Del(5q) resulted as founder (better prognosis) or secondary hit (preceded by TP53 mutations). Using Bayesian prediction analyses on 57 HI marker genes we established the minimal del(5q) gene signature that distinguishes del(5q) from diploid cases. Clusters of diploid cases mimicking the del(5q) signature support the overall importance of del(5q) genes in the pathogenesis of MDS in general. Sub-clusters within del(5q) patients pointed towards the inherent intrapatient heterogeneity of HI genes. INTERPRETATION: The underlying clonal expansion drive results from a balance between the "HI-driver" genes (e.g., CSNK1A1, CTNNA1, TCERG1) and the proapoptotic "HI-anti-drivers" (e.g., RPS14, PURA, SIL1). The residual essential clonal expansion drive allows for selection of accelerator mutations such as TP53 (denominating poor) and CSNK1A1 mutations (with a better prognosis) which overcome pro-apoptotic genes (e.g., p21, BAD, BAX), resulting in a clonal expansion. In summary, we describe the complete picture of del(5q) MN identifying the crucial genes, gene clusters and clonal hierarchy dictating the clinical course of del(5q) patients. FUNDING: Torsten Haferlach Leukemia Diagnostics Foundation. US National Institute of Health (NIH) grants R35 HL135795, R01HL123904, R01 HL118281, R01 HL128425, R01 HL132071, and a grant from Edward P. Evans Foundation.

Molecular International Prognostic Scoring System for Myelodysplastic Syndromes.

BACKGROUND: Risk stratification and therapeutic decision-making for myelodysplastic syndromes (MDS) are based on the International Prognostic Scoring System­Revised (IPSS-R), which considers hematologic parameters and cytogenetic abnormalities. Somatic gene mutations are not yet used in the risk stratification of patients with MDS. METHODS: To develop a clinical-molecular prognostic model (IPSS-Molecular [IPSS-M]), pretreatment diagnostic or peridiagnostic samples from 2957 patients with MDS were profiled for mutations in 152 genes. Clinical and molecular variables were evaluated for associations with leukemia-free survival, leukemic transformation, and overall survival. Feature selection was applied to determine the set of independent IPSS-M prognostic variables. The relative weights of the selected variables were estimated using a robust Cox multivariable model adjusted for confounders. The IPSS-M was validated in an external cohort of 754 Japanese patients with MDS. RESULTS: We mapped at least one oncogenic genomic alteration in 94% of patients with MDS. Multivariable analysis identified TP53multihit, FLT3 mutations, and MLLPTD as top genetic predictors of adverse outcomes. Conversely, SF3B1 mutations were associated with favorable outcomes, but this was modulated by patterns of comutation. Using hematologic parameters, cytogenetic abnormalities, and somatic mutations of 31 genes, the IPSS-M resulted in a unique risk score for individual patients. We further derived six IPSS-M risk categories with prognostic differences. Compared with the IPSS-R, the IPSS-M improved prognostic discrimination across all clinical end points and restratified 46% of patients. The IPSS-M was applicable in primary and secondary/therapy-related MDS. To simplify clinical use of the IPSS-M, we developed an open-access Web calculator that accounts for missing values. CONCLUSIONS: Combining genomic profiling with hematologic and cytogenetic parameters, the IPSS-M improves the risk stratification of patients with MDS and represents a valuable tool for clinical decision-making. (Funded by Celgene Corporation through the MDS Foundation, the Josie Robertson Investigators Program, the Edward P. Evans Foundation, the Projects of National Relevance of the Italian Ministry of University and Research, Associazione Italiana per la Ricerca sul Cancro, the Japan Agency for Medical Research and Development, Cancer Research UK, the Austrian Science Fund, the MEXT [Japanese Ministry of Education, Culture, Sports, Science and Technology] Program for Promoting Research on the Supercomputer Fugaku, the Japan Society for the Promotion of Science, the Taiwan Department of Health, and Celgene Corporation through the MDS Foundation.)

BCL-2 Inhibitor ABT-737 Effectively Targets Leukemia-Initiating Cells with Differential Regulation of Relevant Genes Leading to Extended Survival in a NRAS/BCL-2 Mouse Model of High Risk-Myelodysplastic Syndrome.

During transformation, myelodysplastic syndromes (MDS) are characterized by reducing apoptosis of bone marrow (BM) precursors. Mouse models of high risk (HR)-MDS and acute myelogenous leukemia (AML) post-MDS using mutant NRAS and overexpression of human BCL-2, known to be poor prognostic indicators of the human diseases, were created. We have reported the efficacy of the BCL-2 inhibitor, ABT-737, on the AML post-MDS model; here, we report that this BCL-2 inhibitor also significantly extended survival of the HR-MDS mouse model, with reductions of BM blasts and lineage negative/Sca1+/KIT+ (LSK) cells. Secondary transplants showed increased survival in treated compared to untreated mice. Unlike the AML model, BCL-2 expression and RAS activity decreased following treatment and the RAS:BCL-2 complex remained in the plasma membrane. Exon-specific gene expression profiling (GEP) of HR-MDS mice showed 1952 differentially regulated genes upon treatment, including genes important for the regulation of stem cells, differentiation, proliferation, oxidative phosphorylation, mitochondrial function, and apoptosis; relevant in human disease. Spliceosome genes, found to be abnormal in MDS patients and downregulated in our HR-MDS model, such as Rsrc1 and Wbp4, were upregulated by the treatment, as were genes involved in epigenetic regulation, such as DNMT3A and B, upregulated upon disease progression and downregulated upon treatment.

ASXL1 mutations are associated with distinct epigenomic alterations that lead to sensitivity to venetoclax and azacytidine.

The BCL2-inhibitor, Venetoclax (VEN), has shown significant anti-leukemic efficacy in combination with the DNMT-inhibitor, Azacytidine (AZA). To explore the mechanisms underlying the selective sensitivity of mutant leukemia cells to VEN and AZA, we used cell-based isogenic models containing a common leukemia-associated mutation in the epigenetic regulator ASXL1. KBM5 cells with CRISPR/Cas9-mediated correction of the ASXL1G710X mutation showed reduced leukemic growth, increased myeloid differentiation, and decreased HOXA and BCL2 gene expression in vitro compared to uncorrected KBM5 cells. Increased expression of the anti-apoptotic gene, BCL2, was also observed in bone marrow CD34+ cells from ASXL1 mutant MDS patients compared to CD34+ cells from wild-type MDS cases. ATAC-sequencing demonstrated open chromatin at the BCL2 promoter in the ASXL1 mutant KBM5 cells. BH3 profiling demonstrated increased dependence of mutant cells on BCL2. Upon treatment with VEN, mutant cells demonstrated increased growth inhibition. In addition, genome-wide methylome analysis of primary MDS samples and isogenic cell lines demonstrated increased gene-body methylation in ASXL1 mutant cells, with consequently increased sensitivity to AZA. These data mechanistically link the common leukemia-associated mutation ASXL1 to enhanced sensitivity to VEN and AZA via epigenetic upregulation of BCL2 expression and widespread alterations in DNA methylation.

MDMX acts as a pervasive preleukemic-to-acute myeloid leukemia transition mechanism.

MDMX is overexpressed in the vast majority of patients with acute myeloid leukemia (AML). We report that MDMX overexpression increases preleukemic stem cell (pre-LSC) number and competitive advantage. Utilizing five newly generated murine models, we found that MDMX overexpression triggers progression of multiple chronic/asymptomatic preleukemic conditions to overt AML. Transcriptomic and proteomic studies revealed that MDMX overexpression exerts this function, unexpectedly, through activation of Wnt/ß-Catenin signaling in pre-LSCs. Mechanistically, MDMX binds CK1α and leads to accumulation of ß-Catenin in a p53-independent manner. Wnt/ß-Catenin inhibitors reverse MDMX-induced pre-LSC properties, and synergize with MDMX-p53 inhibitors. Wnt/ß-Catenin signaling correlates with MDMX expression in patients with preleukemic myelodysplastic syndromes and is associated with increased risk of progression to AML. Our work identifies MDMX overexpression as a pervasive preleukemic-to-AML transition mechanism in different genetically driven disease subtypes, and reveals Wnt/ß-Catenin as a non-canonical MDMX-driven pathway with therapeutic potential for progression prevention and cancer interception.

The utilisation of glutamine and glucose by a 3-D tumour model trapped in quiescence.

Solid tumours modify their metabolic strategy to ensure sufficient biomass and energy to maintain a high rate of proliferation. However, solid tumours are characterised by a high proportion of quiescent cells and little is known about their metabolic profile. A tumour spheroid model with DLD1 cells was used to investigate the influence of a quiescent state on the cellular utilisation of glucose and glutamine. Quiescent DLD1 spheroids displayed increased depletion of both nutrients from the bathing medium compared to their proliferative counterparts and displayed highly active overall metabolism. A combination of biochemical and metabolomics approaches demonstrated that glucose utilisation resulted in an increased production of the 3-carbon intermediates lactate and alanine in quiescent spheroids. In addition, glutamine metabolism was directed to anabolic pathways; including the "reverse TCA cycle" to produce citrate for fatty-acid synthesis. These adaptations in DLD1 spheroids may propose a metabolic altruism of quiescent regions in solid tumours to provide biosynthetic intermediates required to sustain tumour growth, angiogenesis and metastasis.

SF3B1 mutant myelodysplastic syndrome: Recent advances.

The myelodysplastic syndromes (MDS) are common myeloid malignancies. Mutations in genes encoding different components of the spliceosome occur in more than half of all MDS patients. SF3B1 is the most frequently mutated splicing factor gene in MDS, and there is a strong association between SF3B1 mutations and the presence of ring sideroblasts in the bone marrow of MDS patients. It has been recently proposed that SF3B1 mutant MDS should be recognized as a distinct nosologic entity. Splicing factor mutations cause aberrant pre-mRNA splicing of many target genes, some of which have been shown to impact on hematopoiesis in functional studies. Emerging data show that some of the downstream effects of different mutated splicing factors converge on common cellular processes, such as hyperactivation of NF-κB signaling and increased R-loops. The aberrantly spliced target genes and the dysregulated pathways and cellular processes associated with splicing factor mutations provided the rationale for new potential therapeutic approaches to target MDS cells with mutations of SF3B1 and other splicing factors.

Phospholipase C beta1 (PI-PLCbeta1)/Cyclin D3/protein kinase C (PKC) alpha signaling modulation during iron-induced oxidative stress in myelodysplastic syndromes (MDS).

MDS are characterized by anemia and transfusion requirements. Transfused patients frequently show iron overload that negatively affects hematopoiesis. Iron chelation therapy can be effective in these MDS cases, but the molecular consequences of this treatment need to be further investigated. That is why we studied the molecular features of iron effect and Deferasirox therapy on PI-PLCbeta1 inositide signaling, using hematopoietic cells and MDS samples. At baseline, MDS patients showing a positive response after iron chelation therapy displayed higher levels of PI-PLCbeta1/Cyclin D3/PKCalpha expression. During treatment, these responder patients, as well as hematopoietic cells treated with FeCl3 and Deferasirox, showed a specific reduction of PI-PLCbeta1/Cyclin D3/PKCalpha expression, indicating that this signaling pathway is targeted by Deferasirox. The treatment was also able to specifically decrease the production of ROS. This effect correlated with a reduction of IL-1A and IL-2, as well as Akt/mTOR phosphorylation. In contrast, cells exposed only to FeCl3 and cells from MDS patients refractory to Deferasirox showed a specific increase of ROS and PI-PLCbeta1/Cyclin D3/PKCalpha expression. All in all, our data show that PI-PLCbeta1 signaling is a target for iron-induced oxidative stress and suggest that baseline PI-PLCbeta1 quantification could predict iron chelation therapy response in MDS.

SF3B1-mutant MDS as a distinct disease subtype: a proposal from the International Working Group for the Prognosis of MDS.

The 2016 revision of the World Health Organization classification of tumors of hematopoietic and lymphoid tissues is characterized by a closer integration of morphology and molecular genetics. Notwithstanding, the myelodysplastic syndrome (MDS) with isolated del(5q) remains so far the only MDS subtype defined by a genetic abnormality. Approximately half of MDS patients carry somatic mutations in spliceosome genes, with SF3B1 being the most commonly mutated one. SF3B1 mutation identifies a condition characterized by ring sideroblasts (RS), ineffective erythropoiesis, and indolent clinical course. A large body of evidence supports recognition of SF3B1-mutant MDS as a distinct nosologic entity. To further validate this notion, we interrogated the data set of the International Working Group for the Prognosis of MDS (IWG-PM). Based on the findings of our analyses, we propose the following diagnostic criteria for SF3B1-mutant MDS: (1) cytopenia as defined by standard hematologic values, (2) somatic SF3B1 mutation, (3) morphologic dysplasia (with or without RS), and (4) bone marrow blasts <5% and peripheral blood blasts <1%. Selected concomitant genetic lesions represent exclusion criteria for the proposed entity. In patients with clonal cytopenia of undetermined significance, SF3B1 mutation is almost invariably associated with subsequent development of overt MDS with RS, suggesting that this genetic lesion might provide presumptive evidence of MDS in the setting of persistent unexplained cytopenia. Diagnosis of SF3B1-mutant MDS has considerable clinical implications in terms of risk stratification and therapeutic decision making. In fact, this condition has a relatively good prognosis and may respond to luspatercept with abolishment of the transfusion requirement.

Splicing factor mutant myelodysplastic syndromes: Recent advances.

The myelodysplastic syndromes (MDS) are common myeloid malignancies showing frequent progression to acute myeloid leukemia (AML). Pre-mRNA splicing is an essential cellular process carried out by the spliceosome. Mutations in splicing factor genes (including SF3B1, SRSF2, U2AF1 and ZRSR2) occur in over half of MDS patients and result in aberrant pre-mRNA splicing of many target genes, implicating aberrant spliceosome function in MDS disease pathogenesis. Recent functional studies have illuminated the impact on hematopoiesis of some aberrantly spliced target genes associated with splicing factor mutations. Emerging data show that the commonly mutated splicing factors have convergent effects on aberrant splicing of mRNAs that promote NF-κB signaling and on R-loop elevation leading to DNA damage, providing novel insights into MDS disease pathophysiology. It is recognized that the survival of splicing factor mutant cells is dependent on the presence of the wildtype allele, providing a rationale for the use of spliceosome inhibitors in splicing factor mutant MDS. Pre-clinical studies involving E7107 and H3B-8800 have shown the potential of these spliceosome inhibitors for the treatment of splicing factor mutant MDS and AML.

Recent advances in MDS mutation landscape: Splicing and signalling.

Recurrent cytogenetic aberrations, genetic mutations and variable gene expression have been consistently recognized in solid cancers and in leukaemia, including in Myelodysplastic Syndromes (MDS). Besides conventional cytogenetics, the growing accessibility of new techniques has led to a deeper analysis of the molecular significance of genetic variations. Indeed, gene mutations affecting splicing genes, as well as genes implicated in essential signalling pathways, play a pivotal role in MDS physiology and pathophysiology, representing potential new molecular targets for innovative therapeutic strategies.