Proposals for revised IWG 2018 hematological response criteria in patients with MDS included in clinical trials.

The heterogeneity of myelodysplastic syndromes (MDSs) has made evaluating patient response to treatment challenging. In 2006, the International Working Group (IWG) proposed a revision to previously published standardized response criteria (IWG 2000) for uniformly evaluating clinical responses in MDSs. These IWG 2006 criteria have been used prospectively in many clinical trials in MDSs, but proved challenging in several of them, especially for the evaluation of erythroid response. In this report, we provide rationale for modifications (IWG 2018) of these recommendations, mainly for "hematological improvement" criteria used for lower-risk MDSs, based on recent practical and reported experience in clinical trials. Most suggestions relate to erythroid response assessment, which are refined in an overall more stringent manner. Two major proposed changes are the differentiation between "procedures" and "criteria" for hematologic improvement-erythroid assessment and a new categorization of transfusion-burden subgroups.

Utility of next-generation sequencing technologies for the efficient genetic resolution of haematological disorders.

Next-generation sequencing (NGS) has now evolved to be a relatively affordable and efficient means of detecting genetic mutations. Whole genome sequencing (WGS) or whole exome sequencing (WES) offers the opportunity for rapid diagnosis in many paediatric haematological conditions, where phenotypes are variable and either a large number of genes are involved, or the genes are large making sanger sequencing expensive and labour-intensive. NGS offers the potential for gene discovery in patients who do not have mutations in currently known genes. This report shows how WES was used in the diagnosis of six paediatric haematology cases. In four cases (Diamond-Blackfan anaemia, congenital neutropenia (n = 2), and Fanconi anaemia), the diagnosis was suspected based on classical phenotype, and NGS confirmed those suspicions. Mutations in RPS19, ELANE and FANCD2 were found. The final two cases (MYH9 associated macrothrombocytopenia associated with multiple congenital anomalies; atypical juvenile myelomonocytic leukaemia associated with a KRAS mutation) highlight the utility of NGS where the diagnosis is less certain, or where there is an unusual phenotype. We discuss the advantages and limitations of NGS in the setting of these cases, and in haematological conditions more broadly, and discuss where NGS is most efficiently used.

Skin ulcers related to chronic graft-versus-host disease: clinical findings and associated morbidity.

BACKGROUND: According to the National Institutes of Health classification of chronic graft-versus-host disease (cGVHD), skin ulcers after allogeneic haematopoietic stem-cell transplantation (HSCT) are recorded as having the maximal severity score but published data are scarce. OBJECTIVES: To describe skin ulcers related to cGVHD with an emphasis on clinical findings, associated morbidity, management and evolution. PATIENTS AND METHODS: A multicentre retrospective analysis was carried out of patients with a diagnosis of cGVHD skin ulcers. RESULTS: All 25 patients included in the study had sclerotic skin cGVHD and 21 had lichenoid skin lesions associated with the sclerotic skin lesions. Thirteen patients had severe cGVHD without considering the skin, because of the involvement of an extracutaneous organ by cGVHD. The median time from HSCT to the onset of ulcers was 44 months. In addition to scleroderma, initial skin lesions at the site of ulcers were bullous erosive lichen in 21 patients and bullous erosive morphoea in four patients. Fifteen patients had an inaugural oedema. Ulcers were mostly bilateral with a predilection for the lower limbs. They were frequently colonized but few infections occurred. Four patients died during a median follow-up period of 55 months. CONCLUSIONS: Chronic graft-versus-host disease skin ulcers occur in patients with sclerodermatous skin cGVHD, are associated with severe cGVHD, often start with bullous lichenoid lesions or bullous morphoea and seem to cause more morbidity than mortality, given the low rate of mortality observed in our series of patients.

Genotype and clinical care correlations in craniosynostosis: findings from a cohort of 630 Australian and New Zealand patients.

Craniosynostosis is one of the most common craniofacial disorders encountered in clinical genetics practice, with an overall incidence of 1 in 2,500. Between 30% and 70% of syndromic craniosynostoses are caused by mutations in hotspots in the fibroblast growth factor receptor (FGFR) genes or in the TWIST1 gene with the difference in detection rates likely to be related to different study populations within craniofacial centers. Here we present results from molecular testing of an Australia and New Zealand cohort of 630 individuals with a diagnosis of craniosynostosis. Data were obtained by Sanger sequencing of FGFR1, FGFR2, and FGFR3 hotspot exons and the TWIST1 gene, as well as copy number detection of TWIST1. Of the 630 probands, there were 231 who had one of 80 distinct mutations (36%). Among the 80 mutations, 17 novel sequence variants were detected in three of the four genes screened. In addition to the proband cohort there were 96 individuals who underwent predictive or prenatal testing as part of family studies. Dysmorphic features consistent with the known FGFR1-3/TWIST1-associated syndromes were predictive for mutation detection. We also show a statistically significant association between splice site mutations in FGFR2 and a clinical diagnosis of Pfeiffer syndrome, more severe clinical phenotypes associated with FGFR2 exon 10 versus exon 8 mutations, and more frequent surgical procedures in the presence of a pathogenic mutation. Targeting gene hot spot areas for mutation analysis is a useful strategy to maximize the success of molecular diagnosis for individuals with craniosynostosis.

High response rate and improved exercise capacity and quality of life with a new regimen of darbepoetin alfa with or without filgrastim in lower-risk myelodysplastic syndromes: a phase II study by the GFM.

Darbepoetin (DAR), with or without granulocyte colony-stimulating factor (G-CSF), has proved effective in treating anemia in patients with lower-risk myelodysplastic syndrome (MDS), but its effects on quality of life (QoL) and exercise functioning are less well established. In this phase II study (no. NCT00443339), lower-risk MDS patients with anemia and endogenous erythropoietin (EPO) level <500 IU/L received DAR 500 µg once every 2 weeks for 12 weeks, with G-CSF added at week 12 in non-responders. Physical performance was assessed with the 6-min walking test and, for fit patients, maximal oxygen consumption (VO2max). QoL was evaluated using SF-36 and FACT-An tests. In 99 patients, erythroid response rate according to IWG 2006 criteria was 48 and 56 % at 12 and 24 weeks, respectively. Addition of G-CSF rescued 22 % of non-responders. In 48 % of the responders, interval between darbepoetin injections could be increased for maintenance treatment. Serum EPO level was the only independent predictive factor of response at 12 weeks, and its most discriminant cutoff value was 100 IU/L. QoL and VO2max showed improvement over time in responders, compared with non-responders. With a median follow-up of 52 months, median response duration was not reached, and 3-year cumulative incidence of acute myeloid leukemia and overall survival (OS) was 14.5 and 70 %, respectively. Baseline transfusion dependence, International Prognostic Score System (IPSS), and Revised IPSS accurately predicted OS from treatment onset. Tolerance of darbepoetin was good. In conclusion, this regimen of darbepoetin every 2 weeks yielded high response rates and prolonged response duration. Objective improvement in exercise testing and in patient-reported QoL confirms the clinical relevance of anemia correction with erythropoiesis-stimulating agents.

Mutations in TGIF cause holoprosencephaly and link NODAL signalling to human neural axis determination.

Holoprosencephaly (HPE) is the most common structural defect of the developing forebrain in humans (1 in 250 conceptuses, 1 in 16,000 live-born infants). HPE is aetiologically heterogeneous, with both environmental and genetic causes. So far, three human HPE genes are known: SHH at chromosome region 7q36 (ref. 6); ZIC2 at 13q32 (ref. 7); and SIX3 at 2p21 (ref. 8). In animal models, genes in the Nodal signalling pathway, such as those mutated in the zebrafish mutants cyclops (refs 9,10), squint (ref. 11) and one-eyed pinhead (oep; ref. 12), cause HPE. Mice heterozygous for null alleles of both Nodal and Smad2 have cyclopia. Here we describe the involvement of the TG-interacting factor (TGIF), a homeodomain protein, in human HPE. We mapped TGIF to the HPE minimal critical region in 18p11.3. Heterozygous mutations in individuals with HPE affect the transcriptional repression domain of TGIF, the DNA-binding domain or the domain that interacts with SMAD2. (The latter is an effector in the signalling pathway of the neural axis developmental factor NODAL, a member of the transforming growth factor-beta (TGF-beta) family.) Several of these mutations cause a loss of TGIF function. Thus, TGIF links the NODAL signalling pathway to the bifurcation of the human forebrain and the establishment of ventral midline structures.

The new Ghent criteria for Marfan syndrome: what do they change?

The diagnosis of Marfan syndrome (MFS) is challenging and international criteria have been proposed. The 1996 Ghent criteria were adopted worldwide, but new diagnostic criteria for MFS were released in 2010, giving more weight to aortic root aneurysm and ectopia lentis. We aimed to compare the diagnosis reached by applying this new nosology vs the Ghent nosology in a well-known series of 1009 probands defined by the presence of an FBN1 mutation. A total of 842 patients could be classified as MFS according to the new nosology (83%) as compared to 894 (89%) according to the 1996 Ghent criteria. The remaining 17% would be classified as ectopia lentis syndrome (ELS), mitral valve prolapse syndrome or mitral valve, aorta, skeleton and skin (MASS) syndrome, or potential MFS in patients aged less than 20 years. Taking into account the median age at last follow-up (29 years), the possibility has to be considered that these patients would go on to develop classic MFS with time. Although the number of patients for a given diagnosis differed only slightly, the new nosology led to a different diagnosis in 15% of cases. Indeed, 10% of MFS patients were reclassified as ELS or MASS in the absence of aortic dilatation; conversely, 5% were reclassified as MFS in the presence of aortic dilatation. The nosology is easier to apply because the systemic score is helpful to reach the diagnosis of MFS only in a minority of patients. Diagnostic criteria should be a flexible and dynamic tool so that reclassification of patients with alternative diagnosis is possible, requiring regular clinical and aortic follow-up.

[Behçet's-like syndrome and other dysimmunitary manifestations related to myelodysplastic syndromes with trisomy 8]. / Syndrome de pseudo-Behçet et autres manifestations dysimmunitaires associées aux syndromes myélodysplasiques avec trisomie 8.

Myelodysplastic syndromes (MDS) are clonal hematopoietic malignancies which are also characterised by immune dysregulation. The impaired immune response is mainly due to T lymphocytes (CD8 and T regulatory cells) with increased cell apoptosis. MDS could be associated in some cases with various clinical dysimmune features; however, only MDS with trisomy 8 is correlated with particular clinical phenotype. The latter is mainly Behçet's-like disease which includes orogenital aphtosis, skin features and severe ulcerative digestive disease of ileocaecal distribution. Other clinical manifestations, such as arthritis or neutrophilic dermatosis, have been also described in MDS patients with trisomy 8. The dysimmune manifestations, and among them the Behçet's-like disease, do not impact the overall survival or the risk of progression to acute myeloid leukemia. Immunosuppressive and immunomodulatory therapies, and among them TNF-α inhibitors, are usually ineffective to control the dysimmune manifestations. Targeting the underlying clonal disease with specific therapies, such as azacitidine, seems to be the best strategy to control these disorders, even in MDS patients with low-risk disease.

Effects of azacitidine in 93 patients with IDH1/2 mutated acute myeloid leukemia/myelodysplastic syndromes: a French retrospective multicenter study.

Isocitrate dehydrogenase 1 (IDH1) and 2 (IDH2) mutations in Myeloid Neoplams (MNs) exhibit DNA hypermethylation via 2-hydroxyglutarate (2HG) over-production. Clinical impact of azacitidine (AZA) remains inconsistent in IDH1/2-mutated MNs and the potential of serum 2HG as a suitable marker of response to AZA is unknown. To address these questions, we retrospectively analyzed 93 MNs patients (78 AML, 11 MDS, 4 CMML) with IDH1/2 mutations treated with AZA. After a median of 5 cycles of AZA, overall response rate was 28% (including 15% complete remission) and median OS was 12.3 months (significantly shorter in AML compared to MDS/CMML patients). In multivariate analysis of AML patients, DNMT3A mutation was associated with shorter OS while IDH1/2 mutation subtypes had no independent impact. No difference was observed in serum 2HG levels upon AZA treatment between responding and refractory patients suggesting that serum 2HG cannot be used as a surrogate marker of AZA response.

Pathogenic FBN1 mutations in 146 adults not meeting clinical diagnostic criteria for Marfan syndrome: further delineation of type 1 fibrillinopathies and focus on patients with an isolated major criterion.

Mutations in the FBN1 gene cause Marfan syndrome (MFS) and have been associated with a wide range of milder overlapping phenotypes. A proportion of patients carrying a FBN1 mutation does not meet diagnostic criteria for MFS, and are diagnosed with "other type I fibrillinopathy." In order to better describe this entity, we analyzed a subgroup of 146 out of 689 adult propositi with incomplete "clinical" international criteria (Ghent nosology) from a large collaborative international study including 1,009 propositi with a pathogenic FBN1 mutation. We focused on patients with only one major clinical criterion, [including isolated ectopia lentis (EL; 12 patients), isolated ascending aortic dilatation (17 patients), and isolated major skeletal manifestations (1 patient)] or with no major criterion but only minor criteria in 1 or more organ systems (16 patients). At least one component of the Ghent nosology, insufficient alone to make a minor criterion, was found in the majority of patients with isolated ascending aortic dilatation and isolated EL. In patients with isolated EL, missense mutations involving a cysteine were predominant, mutations in exons 24-32 were underrepresented, and no mutations leading to a premature truncation were found. Studies of recurrent mutations and affected family members of propositi with only one major clinical criterion argue for a clinical continuum between such phenotypes and classical MFS. Using strict definitions, we conclude that patients with FBN1 mutation and only one major clinical criterion or with only minor clinical criteria of one or more organ system do exist but represent only 5% of the adult cohort.

Contribution of molecular analyses in diagnosing Marfan syndrome and type I fibrillinopathies: an international study of 1009 probands.

BACKGROUND: The diagnosis of Marfan syndrome (MFS) is usually initially based on clinical criteria according to the number of major and minor systems affected following international nosology. The number of FBN1 mutation carriers, at risk of aortic complications who would not be properly diagnosed based only on clinical grounds, is of growing importance owing to the increased availability of molecular screening. The aim of the study was to identify patients who should be considered for FBN1 mutation screening. METHODS: Our international series included 1009 probands with a known FBN1 mutation. Patients were classified as either fulfilling or not fulfilling "clinical" criteria. In patients with unfulfilled "clinical" criteria, we evaluated the percentage of additional patients who became positive for international criteria when the FBN1 mutation was considered. The aortic risk was evaluated and compared in patients fulfilling or not fulfilling the "clinical" international criteria. RESULTS: Diagnosis of MFS was possible on clinical grounds in 79% of the adults, whereas 90% fulfilled the international criteria when including the FBN1 mutation. Corresponding figures for children were 56% and 85%, respectively. Aortic dilatation occurred later in adults with unfulfilled "clinical criteria" when compared to the Marfan syndrome group (44% vs 73% at 40 years, p<0.001), but the lifelong risk for ascending aortic dissection or surgery was not significantly different in both groups. CONCLUSIONS: Because of its implications for aortic follow-up, FBN1 molecular analysis is recommended in newly suspected MFS when two systems are involved with at least one major system affected. This is of utmost importance in patients without aortic dilatation and in children.

Inhibition of NEMO, the regulatory subunit of the IKK complex, induces apoptosis in high-risk myelodysplastic syndrome and acute myeloid leukemia.

In high-risk myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML), blasts constitutively activate the antiapoptotic transcription factor nuclear factor-kappaB (NF-kappaB). Here, we show that this NF-kappaB activation relies on the constitutive activation of the IkappaB kinase (IKK) complex, which is formed by the IKKalpha, IKKbeta and IKKgamma/NF-kappaB essential modulator (NEMO) subunits. A cell-permeable peptide that mimics the leucine zipper subdomain of IKKgamma, thus preventing its oligomerization, inhibited the constitutive NF-kappaB activation and induced apoptotic cell death in a panel of human MDS and AML cell lines (P39, MOLM13, THP1 and MV4-11). Small interfering RNA-mediated knockdown of the p65 NF-kappaB subunit or the three IKK subunits including IKKgamma/NEMO also induced apoptotic cell death in P39 cells. Cell death induced by the IKKgamma/NEMO-antagonistic peptide involved the caspase-independent loss of the mitochondrial transmembrane potential as well as signs of outer mitochondrial membrane permeabilization with the consequent release of cytochrome c, apoptosis-inducing factor and endonuclease G. Primary bone marrow CD34(+) cells from high-risk MDS and AML patients also succumbed to the IKKgamma/NEMO-antagonistic peptide, but not to a mutated control peptide. Altogether, these data indicate that malignant cells in high-risk MDS and AML cells critically depend on IKKgamma/NEMO to survive. Moreover, our data delineate a novel procedure for their therapeutic removal, through inhibition of IKKgamma/NEMO oligomerization.

NF-kappaB inhibition sensitizes to starvation-induced cell death in high-risk myelodysplastic syndrome and acute myeloid leukemia.

CD34(+) bone marrow blasts from high-risk myelodysplastic syndrome (MDS) patients as well as MDS patient-derived cell lines (P39 and MOLM13) constitutively activate the nuclear factor-kappaB (NF-kappaB) pathway and undergo apoptosis when NF-kappaB is inhibited. Here, we show that the combination of conventional chemotherapeutic agents (daunorubicin, mitoxantrone, 5-azacytidine or camptothecin) with the NF-kappaB inhibitor BAY11-7082 did not yield a synergistic cytotoxicity. In contrast, BAY11-7082 (which targets the NF-kappaB-activating I-kappaB kinase (IKK) complex) or knockdown of essential components of the NF-kappaB system (such as the IKK1 and IKK2 subunits of the IKK complex and the p65 subunit of NF-kappaB), by small interfering RNAs sensitized MDS cell lines to starvation-induced apoptosis. The combination of BAY11-7082 and nutrient depletion synergistically killed the acute myeloid leukemia (AML) cell line U937 as well as primary CD34(+) bone marrow blasts from AML and high-risk MDS patients. The synergistic killing by BAY11-7082, combined with nutrient depletion, led to cell death accompanied by all hallmarks of apoptosis, including an early loss of the mitochondrial transmembrane potential, the release of cytochrome c and apoptosis-inducing factor (AIF) from mitochondria, activation of caspase-3, phosphatidylserine exposure on the plasma membrane surface and nuclear chromatin condensation. Transmission electron microscopy revealed the presence of numerous autophagic vacuoles in the cytoplasm before cells underwent nuclear apoptosis. Nonetheless, cell death was neither inhibited by the pan-caspase inhibitor z-VAD-fmk nor by knockdown of AIF or of essential components of the autophagy pathway (ATG5, ATG6/Beclin-1, ATG10, ATG12). In contrast, external supply of glucose, insulin or insulin-like growth factor-I could retard the cell death induced by BAY11-7082 combined with starvation. These results suggest that in MDS cells, NF-kappaB inhibition can precipitate a bioenergetic crisis that leads to an autophagic stress response followed by apoptotic cell death.

Treatment of myelodysplastic syndromes with 5q deletion before the lenalidomide era; the GFM experience with EPO and thalidomide.

Anemia in MDS with 5q deletion was generally considered, until the advent of lenalidomide, unresponsive to available treatments. We analyzed erythroid response to erythropoetin (EPO) or darbepoetin (DAR) and thalidomide in MDS with 5q deletion treated by French centers (GFM) and in whom karyotype was successfully performed. Of 345 patients treated with EPO or DAR+/-G-CSF, 48 had 5q deletion. The response rate was 46% (31% major, 15% minor) according to International Working Group (IWG) 2000 criteria versus 64% in patients without 5q deletion (p=0.03). According to IWG 2006 criteria, the response rate in patients with 5q deletion was 39% versus 52% in patients without 5q deletion (p=0.10). Mean duration of response was 14 months versus 25 months (IWG 2000) and 13 months versus 27 months (IWG 2006) in 5q deletion and non-5q deletion patients (p=0.019 and 0.003, respectively). Of 120 MDS treated with thalidomide, all of whom had successful cytogenetic analysis, 37% of the 24 patients with 5q deletion responded (IWG 2000 criteria, 20% major, 17% minor) with a mean duration of 9.5 months, versus 32% (18% major, 14% minor) in MDS without 5q deletion and a mean response duration of 9 months (p=NS). Our results confirm that response rates to EPO or DAR and thalidomide are clearly inferior to those obtained with lenalidomide.

Outcomes and mutational analysis of patients with lower-risk non-del5q myelodysplastic syndrome treated with antithymocyte globulin with or without ciclosporine A.

Immunosuppressive treatment is a disease-modifying therapy for lower-risk myelodysplastic syndromes (MDS). However, IST is relatively rarely used and long-term outcomes of patients are seldom reported. We retrospectively studied outcomes of 20 patients with lower-risk non del 5q MDS with transfusion dependency, with horse or rabbit antithymocyte globulin ±â€¯ciclosporine A, and frontline eltrombopag in two of them. IPSS-R was low, intermediate and high in 30%, 55% and 10% of the patients, respectively. Fifty-five percent of the patients had hypocellular bone marrow (BM). Baseline mutations were detected in 31.5% of the patients and were more frequent in patients with normo/hypercellular MDS than in patients with hypocellular MDS. Transfusion independence rate for both red blood cells (RBC) and platelets was achieved in 45% of patients. RBC transfusion duration ≤6 months, B-cell counts >0.2 G/L and, marginally, BM blasts ≤2% were associated with higher transfusion independence rate. Age and cellularity did not influence the response rate. Median transfusion independence duration was 53 months. Cumulative incidence of progression to a more aggressive myeloid disease was 0 in patients without baseline mutations and 33% in patients with baseline mutations (P = .008). Median progression-free and overall survival after treatment onset and median overall survival after loss of transfusion independence were 45.5 months, 68 months and not reached, respectively. In conclusion, antithymocyte globulin ±â€¯ciclosporine A results in durable responses in MDS, irrespective of age, in patients with lower-risk disease without B-cell lymphopenia and treated early in the course of the disease.

Combined inhaled steroids and bronchodilatators in obstructive airway disease after allogeneic stem cell transplantation.

Bronchiolitis obliterans (BO) is a potentially life-threatening complication following allogeneic stem cell transplantation (SCT) and usually carries a poor prognosis. Immunosuppressive medications are the main treatment, but are rarely effective, especially when the disease is severe. Thus, both early detection and alternative therapeutic approaches of post SCT BO are needed. We report our experience with Budesonide/Formoterol, an inhaled steroid and long-acting bronchodilatator combination, in a group of patients with mild to moderately severe BO after SCT whose systemic immunosuppressive treatment had not been modified. Thirteen patients were treated. The diagnosis of BO was based on the presence of respiratory symptoms and air-trapping on expiratory lung high-resolution computed tomography in all patients, associated with irreversible airflow obstruction in seven cases. The median follow-up was 12.8 months (range: 5-29 months). All patients improved clinically, and both forced expiratory volume in 1 (FEV(1)) and mean expiratory flow values increased significantly during follow-up (534+/-268 ml in absolute values and 36+/-27% compared to pretreatment values for FEV(1); P<0.02). These encouraging results provide new insights in the therapeutic approach of BO after SCT and require confirmation in a larger group of patients with a longer follow-up.

Extramedullary relapse in acute promyelocytic leukemia treated with all-trans retinoic acid and chemotherapy.

We analyzed the incidence, presenting features, risk factors of extramedullary (EM) relapse occurring in acute promyelocytic leukemia (APL) treated with all-trans retinoic acid (ATRA) and chemotherapy by using a competing-risk method. In total, 740/ 806 (92%) patients included in three multicenter trials (APL91, APL93 trials and PETHEMA 96) achieved CR, of whom 169 (23%) relapsed, including 10 EM relapses. Nine relapses involved the central nervous system (CNS) and one the skin, of which two were isolated EM relapse. In patients with EM disease, median WBC count was 26950/mm3 (7700-162000). The 3-year cumulative incidence of EM disease at first relapse was 5.0%. Univariate analysis identified age <45 years (P=0.05), bcr3 PML-RARalpha isoform (P= 0.0003) and high WBC counts (> or = 10,000/ mm3) (P<0.0001) as risk factors for EM relapse. In multivariate analysis, only high WBC count remained significant (P= 0.001). Patients with EM relapse had a poorer outcome since median survival from EM relapse was 6.7 months as compared to 26.3 months for isolated BM relapse (P=0.04). In conclusion, EM relapse in APL occurs more frequently in patients with increased WBC counts (> or = 10,000/mm3) and carries a poor prognosis. Whether CNS prophylaxis should be systematically performed in patients with WBC > or = 10,000/mm3 at diagnosis remains to be established.

Preclinical modeling of myelodysplastic syndromes.

Myelodysplastic syndromes (MDS) represent a heterogeneous group of hematological clonal disorders. Here, we have tested the bone marrow (BM) cells from 38 MDS patients covering all risk groups in two immunodeficient mouse models: NSG and NSG-S. Our data show comparable level of engraftment in both models. The level of engraftment was patient specific with no correlation to any specific MDS risk group. Furthermore, the co-injection of mesenchymal stromal cells (MSCs) did not improve the level of engraftment. Finally, we have developed an in vitro two-dimensional co-culture system as an alternative tool to in vivo. Using our in vitro system, we have been able to co-culture CD34+ cells from MDS patient BM on auto- and/or allogeneic MSCs over 4 weeks with a fold expansion of up to 600 times. More importantly, these expanded cells conserved their MDS clonal architecture as well as genomic integrity.