Transformation Of Myelodysplastic Syndrome Research Articles

SETD2 deficiency accelerates MDS-associated leukemogenesis via S100a9 in NHD13 mice and predicts poor prognosis in MDS

AbstractSETD2, the histone H3 lysine 36 methyltransferase, previously identified by us, plays an important role in the pathogenesis of hematologic malignancies, but its role in myelodysplastic syndromes (MDSs) has been unclear. In this study, low expression of SETD2 correlated with shortened survival in patients with MDS, and the SETD2 levels in CD34+ bone marrow cells of those patients were increased by decitabine. We knocked out Setd2 in NUP98-HOXD13 (NHD13) transgenic mice, which phenocopies human MDS, and found that loss of Setd2 accelerated the transformation of MDS into acute myeloid leukemia (AML). Loss of Setd2 enhanced the ability of NHD13+ hematopoietic stem and progenitor cells (HSPCs) to self-renew, with increased symmetric self-renewal division and decreased differentiation and cell death. The growth of MDS-associated leukemia cells was inhibited though increasing the H3K36me3 level by using epigenetic modifying drugs. Furthermore, Setd2 deficiency upregulated hematopoietic stem cell signaling and downregulated myeloid differentiation pathways in the NHD13+ HSPCs. Our RNA-seq and chromatin immunoprecipitation–seq analysis indicated that S100a9, the S100 calcium-binding protein, is a target gene of Setd2 and that the addition of recombinant S100a9 weakens the effect of Setd2 deficiency in the NHD13+ HSPCs. In contrast, downregulation of S100a9 leads to decreases of its downstream targets, including Ikba and Jnk, which influence the self-renewal and differentiation of HSPCs. Therefore, our results demonstrated that SETD2 deficiency predicts poor prognosis in MDS and promotes the transformation of MDS into AML, which provides a potential therapeutic target for MDS-associated acute leukemia.

Overexpression of RUNX3 Represses RUNX1 to Drive Transformation of Myelodysplastic Syndrome

RUNX3, a RUNX family transcription factor, regulates normal hematopoiesis and functions as a tumor suppressor in various tumors in humans and mice. However, emerging studies have documented increased expression of RUNX3 in hematopoietic stem/progenitor cells (HSPC) of a subset of patients with myelodysplastic syndrome (MDS) showing a worse outcome, suggesting an oncogenic function for RUNX3 in the pathogenesis of hematologic malignancies. To elucidate the oncogenic function of RUNX3 in the pathogenesis of MDS in vivo, we generated a RUNX3-expressing, Tet2-deficient mouse model with the pancytopenia and dysplastic blood cells characteristic of MDS in patients. RUNX3-expressing cells markedly suppressed the expression levels of Runx1, a critical regulator of hemaotpoiesis in normal and malignant cells, as well as its target genes, which included crucial tumor suppressors such as Cebpa and Csf1r. RUNX3 bound these genes and remodeled their Runx1-binding regions in Tet2-deficient cells. Overexpression of RUNX3 inhibited the transcriptional function of Runx1 and compromised hematopoiesis to facilitate the development of MDS in the absence of Tet2, indicating that RUNX3 is an oncogene. Furthermore, overexpression of RUNX3 activated the transcription of Myc target genes and rendered cells sensitive to inhibition of Myc-Max heterodimerization. Collectively, these results reveal the mechanism by which RUNX3 overexpression exerts oncogenic effects on the cellular function of and transcriptional program in Tet2-deficient stem cells to drive the transformation of MDS. SIGNIFICANCE: This study defines the oncogenic effects of transcription factor RUNX3 in driving the transformation of myelodysplastic syndrome, highlighting RUNX3 as a potential target for therapeutic intervention.

Identification and validation of prognosis-related DLX5 methylation as an epigenetic driver in myeloid neoplasms.

The deregulated DLX gene family members DLX1/2/3/4/5/6 (DLXs) caused by DNA methylation has been demonstrated in various cancers with therapeutic target value. However, the potential role of DLXs methylation in myeloid neoplasms such as acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) remains to be elucidated. Clinical significance of DLXs methylation/expression was analyzed in patient with AML and MDS. The functional roles of DLXs were determined in vitro. In the identification stage, we found that lower DLX5 expression was correlated with prognosis in AML among all DLXs analyzed by The Cancer Genome Atlas datasets. In the validation stage, we revealed that reduced DLX5 expression was frequently occurred, and was also correlated with promoter hypermethylation in AML evaluated by targeted bisulfite sequencing. Epigenetic studies also showed that DLX5 promoter DNA methylation was associated with its expression. By quantitative polymerase chain reaction, we also validated that DLX5 hypermethylation was frequent event in both AML and MDS, and also correlated with MDS transformation to leukemia. Moreover, DLX5 hypermethylation was associated with lower rate of complete remission and shorter time of leukemia‐free/overall survival, and was also confirmed by Logistic/Cox regression analysis. Functional studies revealed the antiproliferative and pro‐apoptotic effects of DLX5 in MDS‐derived AML cell‐line SKM‐1. Finally, bioinformatics analysis demonstrated that DLX5 functioned in leukemogenesis may be through the association with PI3K/Akt signaling pathway. Collectively, our findings demonstrated that DLX5 methylation, negatively correlated DLX5 expression, was a potential prognostic and predictive indicator in patients with AML and MDS, which could also act as an epigenetic driver in myeloid neoplasms.

The Effects of Human BDH2 on the Cell Cycle, Differentiation, and Apoptosis and Associations with Leukemia Transformation in Myelodysplastic Syndrome

Iron overload is related to leukemia transformation in myelodysplastic syndrome (MDS) patients. Siderophores help to transport iron. Type 2-hydroxybutyrate dehydrogenase (BDH2) is a rate-limiting factor in the biogenesis of siderophores. Using qRT-PCR, we analyze BDH2mRNA expression in the bone marrow (BM) of 187 MDS patients, 119 de novo acute myeloid leukemia (AML) patients, and 43 lymphoma patients with normal BM. Elevated BDH2mRNA expression in BM is observed in MDS patients (n = 187 vs. 43, normal BM; P = 0.009), and this is related to ferritin levels. Patients with higher BDH2 expression show a greater risk of leukemia progression (15.25% vs. 3.77%, lower expression; P = 0.017) and shorter leukemia-free-survival (medium LFS, 9 years vs. 7 years; P = 0.024), as do patients with a ferritin level ≥350 ng/mL. Additionally, we investigate the mechanisms related to the prognostic ability of BDH2 by using BDH2-KD THP1. The cell cycle analysis, surface markers, and special stain studies indicate that BDH2-KD induces differentiation and decreases the growth rate of THP1 cells, which is associated with the retardation of the cell cycle. Moreover, many genes, including genes related to mitochondrial catabolism, oncogenes, tumor suppressor genes, and genes related to cell differentiation and proliferation influence BDH2-KD THP1 cells. Herein, we demonstrate that BDH2 is involved in cell cycle arrest and the inhibition of differentiation in malignant cells. Furthermore, the high BDH2 expression in MDS patients could be suggestive of a poor prognostic factor. This study provides a foundation for further research on the roles of BDH2 and iron metabolism in the pathogenesis of MDS.

A Case of Myeloid Sarcoma in the Nasal Cavity Occurred in the Patient with Leukemic Transformation in Myelodysplastic Syndrome

Myeloid sarcoma is characterized by the presence of myeloid blasts at an extramedullar site that disrupts the normal architecture of the organ. Many of these cases are associated with acute myeloid leukemia, chronic myeloid leukemia, myelodysplastic syndrome, or occur in de novo. It occurs most commonly in skin, lymph node, gastrointestinal tract, bone, soft tissue but, rarely in head and neck; especially in nasal cavity. Therefore, it is often misdiagnosed as a different disease: most commonly as lymphoma. Here we report a rare case of myeloid sarcoma in the nasal cavity that occurred in a patient with leukemic transformation with myelodysplastic syndrome, provided with literature review.

Clonal evolution of myeloid malignancies

Through intensive efforts of genome sequencing of myeloid malignancies, a comprehensive registry of driver mutations has been revealed, virtually providing us with a complete spectrum of driver mutations in these diseases. Importantly, there have been significant correlations between driver mutations, which suggests that some combinations of genetic events confer strong selective advantage on mutated stem cells. Next-generation sequencing technology have also revealed that clonal hematopoiesis is a common, age-related process in which a somatically mutated hematopoietic precursor gives rise to a genetically distinct subpopulation in the blood. Furthermore, novel germline mutations were identified, indicating that mutated stem cells appear long before myelodysplastic syndrome (MDS) presentation. Such founding mutations are thought to be acquired and positively selected in a well-organized manner to allow for expansion of the initiating clone to compromise normal hematopoiesis, ultimately giving rise to MDS and subsequent transformation to acute myeloid leukemia (AML) in many patients.

Clonal evolution of myelodysplastic syndromes

By intensive efforts of sequencing a large number of genomes from patients with myelodysplastic syndromes (MDS), a comprehensive registry of driver mutations repeatedly found in MDS patients has been identified, providing us with a virtually complete spectrum of driver mutations in this disease. Importantly, significant correlations between driver mutations have been revealed, suggesting that some combinations of genetic events confer strong selective advantages on mutated stem cells. Next-generation sequencing technology has also revealed that clonal hematopoiesis is a common, age-related process, in which a somatically mutated hematopoietic precursor gives rise to a genetically distinct subpopulation in the blood. Furthermore, novel germline mutations have been identified, indicating that mutated stem cells appear long before MDS presentation. Such founding mutations are thought to be acquired and positively selected for in a well-organized manner to allow expansion of the initiating clone to compromise normal hematopoiesis, ultimately resulting in MDS and subsequent transformation into acute myeloid leukemia in many patients.

Risk Stratification and Transfusion Dependence Are Independent Risk Factors for Cardiovascular Disease (CVD) in Myelodysplastic Syndrome (MDS)

Background: MDS has been largely excluded from epidemiological studies that demonstrate an increased risk of CVD in older adults with cancer. Nevertheless, somatic mutations leading to clonally restricted hematopoiesis are associated with increased risk of CVD and CVD constitutes the most common non-disease-related cause of death among patients with MDS. Using the SEER Medicare tumor registry, we previously demonstrated that MDS was independently associated with increased risk of CVD and cardiovascular mortality in older adults, thus constituting an important but underestimated cardiovascular hazard. In this study, we sought to determine the influence of MDS-specific factors on the risk of CVD among MDS patients. Methods: We used the SEER Medicare database to identify individuals 66 years or older with an incident diagnosis of MDS between 2004 and 2014. Incident CVD was defined as new myocardial infraction and/or ischemic stroke occurring after diagnosis of MDS. Events were identified with ICD9 and HCPCS codes in Medicare claims from the date of MDS diagnosis to death or study end. Subjects with CVD prior to MDS diagnosis were excluded. Comorbidity burden was estimated with the Charlson comorbidity index (CCI), calculated using claims from the year before MDS diagnosis. MDS was classified into low, intermediate and high risk using ICD-O morphology codes. Subjects requiring 2 or more blood product transfusions within 60 days from MDS diagnosis were considered transfusion dependent. Cumulative incidence functions were used to assess the risk of new events. Cox proportional hazards models, extended for time dependent covariates and coefficients, were used to evaluate clinical variables associated with CVD. Results: The cohort included 13,972 subjects with MDS, most were male (55.2%), non-hispanic white (82.1%), and from metropolitan areas (82.5%). Median age at MDS diagnosis was 82 years (IQR, 78 - 87). MDS was of low, intermediate and high risk in 18.1%, 68.8% and 13.1% respectively. The median CCI score was 0 (IQR, 0 - 2). Red blood cells (RBC) and platelet transfusion dependence occurred in 29% and 6.1% of subjects. The 10-year cumulative incidence of CVD was 47%, 54% and 65% in subjects with low, intermediate and high-risk MDS, respectively (p<0.016; Fig. 1). Similarly, the 10-year cumulative incidence of CVD was 57.5% in RBC transfusion-dependent subjects vs. 49% in non-dependent individuals (p<0.001; Fig 2A). Other factors that significantly influenced the hazard of CVD were male sex, older age and higher CCI. The effect of higher MDS risk (HR 1.1, 95%CI, 1.02 - 1.2) and RBC transfusion dependence (HR 1.3, 95%CI, 1.2 - 1.5) on increased incidence of CVD persisted after accounting for these factors in a multivariate Cox model adjusted for age, gender and CCI. Platelet transfusion dependence did not significantly influence the cumulative incidence of CVD (p=0.252; Fig 2B) or the hazard for CVD in multivariate analysis (HR 0.8, 95%CI, 0.6 - 1.2). Both higher risk MDS (HR 1.6, 95%CI, 1.5 - 1.7) and blood product transfusion dependence (HR 1.9, 95%CI 1.8 - 2) were associated with increased mortality in subjects with MDS. Conclusion: In a large cohort of elderly Medicare beneficiaries with incident diagnosis of MDS, the cumulative incidence of CVD was greater in subjects with higher-risk MDS as determined by bone marrow morphology and in those who were RBC transfusion dependent. Both MDS risk and RBC transfusion dependence were independent risk factors for CVD in multivariate analysis accounting for demographic factors and comorbidity burden. These factors have been previously associated with increased mortality and risk of leukemia transformation in MDS but their role in risk of CVD has not been previously reported. CVD is an important cause of mortality among older adults with MDS and these results can help identify high risk patients for whom strict cardiovascular screening and preventive strategies could impact mortality. Though we used validated methods, study limitations include relying on administrative claims, absence of genetic information and unmeasured confounding factors. Prospective studies and further preclinical research is needed to clarify the mechanisms of CVD in patients with MDS. Figure 1 Disclosures Verma: Janssen: Research Funding; Stelexis: Equity Ownership, Honoraria; Acceleron: Honoraria; Celgene: Honoraria; BMS: Research Funding.

FBXO11 Is a Candidate Tumor Suppressor in the Transformation of MDS to Secondary AML

Myelodysplastic syndrome (MDS) is a heterogenous myeloid lineage malignancy characterized by blood cell morphological dysplasia, ineffective clonal hematopoiesis, and risk of secondary transformation to acute myeloid leukemia (sAML). Genomic sequencing of large MDS cohorts has led to the identification of recurrent genetic abnormalities that carry independent prognostic significance and overlap with mutational changes in sAML. However, no set of mutations is sufficient to predict the transformation of MDS raising the question of how an identical genotype produces MDS in one patient and sAML in another? We hypothesize there are therapeutically targetable cellular processes altered by the initiating genetic changes in MDS that predict transformation to sAML. To uncover novel cellular pathways involved in MDS transformation, we performed an unbiased genome-wide CRISPR/Cas9 in the human MDS-L cell line. MDS-L was established from bone marrow mononuclear cells in a 52-year-old male patient and requires IL3-containing media for growth in vitro (Figure 1A). GFP expressing MDS-L cells were transduced with Cas9 and a sgRNA against GFP to confirm functional Cas9 expression in MDS-L (Figures 1B and C). In Cas9 expressing MDS-L cells, we then transduced the Brunello sgRNA CRISPR library and subjected the cells to IL-3 starvation for 4 weeks. Cells surviving IL-3 starvation were then expanded and harvested for genomic DNA. High throughput sequencing of the barcoded DNA produced raw reads that were analyzed using the PinAPL-Py web-based software. sgRNAs appearing in duplicate with absolute read counts over 1000 or in triplicate over 100 were considered significant. We identified 5 genes that conferred resistance to IL-3 starvation, which included FBXO11 (Figure 1D). The Fbox protein FBXO11 is a component of the SCF ubiquitin ligase complex and regulates its substrates via ubiquitination and proteasomal degradation. FBXO11 is mutated in up to 20% of diffuse large B-cell lymphomas and its loss in breast cancer models leads to increased metastases. Therefore, we hypothesized FBXO11 may also function as a tumor suppressor in the transformation of MDS to AML. We confirmed in the Bloodspot gene expression database that there are decreased levels of FBXO11 in a variety of AML samples, including complex karyotype, compared to normal HSCs. To validate the results of the screen, we synthesized two sgRNAs targeting FBXO11, transduced these into MDS-L cells, and detected reduced FBXO11 expression (Figure 1E). Loss of FBXO11 expression promoted survival in IL-3 free media, confirming the selection readout of the screen (Figure 1F). We then designed a silent mutation in the shorter isoform of FBXO11 (FBXO11v1sm1) that rendered resistance to CRISPR/Cas9 (Figure 1G) and observed that overexpression of FBXO11v1sm1 re-sensitized cells to cytokine starvation (Figure 1H). Whether there are different functions between FBXO11 variant 1 and 4 are currently being explored. We are actively performing RNA sequencing and ubiquitin proteomics in FBXO11 knockout cells to identify its downstream targets and assaying for reduced expression of FBXO11 in primary patient MDS and AML samples. Based on our studies, we predict that SCF ubiquitin ligase component FBXO11 is a tumor suppressor regulating the transformation of MDS to secondary AML. Figure 1 Disclosures Crispino: Sierra Oncology: Consultancy; MPN Research Foundation: Membership on an entity's Board of Directors or advisory committees; Forma Therapeutics: Research Funding; Scholar Rock: Research Funding.

Transcriptional Regulation of Hematopoietic Stem Cells in Aging and Myelodysplastic Syndrome Reveals DDIT3 As a Potential Driver of Transformation

Myelodysplastic syndromes (MDS) are clonal hematopoietic stem cell (HSC) malignancies characterized by ineffective hematopoiesis. Genetic alterations do not fully explain the molecular pathogenesis of the disease, indicating that other types of lesions, such as transcriptional aberrations, may play a role in its development. Moreover, MDS prevalence is almost exclusive to older patients, suggesting that elderly-related alterations may predispose to the development of this clinical entity. Thus, study of the transcriptional lesions occurring in the aging-MDS axis could shed some light of the molecular bases of the disease. To characterize the transcriptional profile of HSCs in aging and MDS, we isolated CD34+, CD38-, CD90+, CD45RA- cells from 11 untreated MDS patients with unilineage and multilineage dysplasia (median of 75 y/o), as well as from 16 young and 8 elderly healthy donors (median of 21 and 70 y/o, respectively), and their expression profile was analyzed using MARS-seq. Unsupervised principal component analysis demonstrated that the three groups of HSCs clustered separately, indicating that different expression profiles characterize healthy young and elderly, and MDS-associated HSCs. To better understand the gene expression deregulation of HSCs, we analyzed the transcriptional dynamisms along the aging-MDS axis, detecting groups of genes following different patterns of expression. Some gene clusters showed exclusive alteration either in aging or in the progression from elderly HSCs to MDS-HSCs, other groups of genes presented a continuous alteration along the axis, and some displayed opposite regulation in aging and in the transition to MDS (Figure 1). Genes showing specific downregulation in aging were involved in DNA damage sensing and repair, and in cell cycle regulation, whereas genes overexpressed in this process were enriched in apoptosis regulators and in cancer-associated genes, including AML-related factors. These findings indicate that transcriptional changes in aging may predispose for MDS and AML, and potentially other malignancies. Interestingly, we detected a group of genes in which the age-mediated upregulation of gene expression was reversed to that of young HSCs in MDS, indicating a "rejuvenation" profile of malignant HSCs. These genes were involved in response to inflammation, to different types of stress conditions such as hypoxia or radiation, and to cytokines. Elderly HSCs may upregulate such genes in response to the known inflammatory microenvironment of elderly bone marrow. Intriguingly, the decrease in expression detected in MDS suggests that malignant HSCs lose the ability of reacting to such stimuli, possibly favoring their survival in a hostile microenvironment. Finally, the analyses performed allowed for the identification of genes showing MDS-specific deregulation. Genes specifically overexpressed in MDS compared to normal (both young and elderly) HSCs, we enriched in transcriptional and epigenetic regulators, and among them, we detected the presence of DDIT3/CHOP, a member of the CCAAT/enhancer-binding protein (C/EBP) family of transcription factors. To determine its potential effects on hematopoietic deregulation, DDIT3 was exogenously overexpressed in healthy HSCs. Notably, its upregulation produced an erythroid bias in an ex-vivo differentiation system, with an increase in the percentage of erythroblasts and a decrease in granulocytes and monocytes compared to HSCs transduced with the empty vector. Transcriptomic analysis of transduced HSCs not subjected to differentiation demonstrated how DDIT3 overexpression produced an erythroid-prone state of HSCs, suggesting it may act as a pioneer factor in MDS-HSCs. Furthermore, gene set enrichment analysis showed that DDIT3 overexpression produced an MDS-like transcriptional profile, suggesting this factor may be key in the acquisition of the disease. Altogether, our results demonstrate that HSCs undergo transcriptional changes in the aging-MDS axis that may alter their intrinsic functions as well as their response to the microenvironment, ultimately contributing to the acquisition of the disease. In particular, our data show that DDIT3 may be a potential driver of MDS transformation. Disclosures Paiva: Amgen, Bristol-Myers Squibb, Celgene, Janssen, Merck, Novartis, Roche, and Sanofi; unrestricted grants from Celgene, EngMab, Sanofi, and Takeda; and consultancy for Celgene, Janssen, and Sanofi: Consultancy, Honoraria, Research Funding, Speakers Bureau. Díez-Campelo:Celgene Corporation: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding.

Metformin inhibits cell proliferation in SKM-1 cells via AMPK-mediated cell cycle arrest

Metformin, a widely used antidiabetic drug, has previously been demonstrated to exert anti-cancer effects in certain hematological malignancies, but its effects on the transformation of myelodysplastic syndromes to acute myeloid leukemia (AML-MDS) remain unclear. The present study aimed to investigate the effects of metformin on SKM-1 cells (an AML-MDS cell line) and its underlying mechanisms. SKM-1 cells were treated with different concentrations of metformin. Cell proliferation was assayed by CCK-8. Apoptosis and cell cycle phases were detected by flow cytometry, while cell cycle related proteins and AMPK were tested by Western blot. SKM-1 cells were transfected with LV-AMPKα1-RNAi to reduce the expression of AMPK. Metformin inhibited cell proliferation in a dose and time dependent manner by inducing G0/G1 phase arrest rather than apoptosis induction. Metformin promoted the expression of p-AMPK, P53, P21CIP1 and P27KIP1, while inhibited the expression of CDK4 and CyclinD1. AMPK knockdown attenuated the effects of metformin on SKM-1 cells. These findings suggested that metformin inhibited proliferation of SKM-1 cells, potentially through an AMPK-mediated cell cycle arrest.

1935 An Unusual Cause of Post-Polypectomy Bleeding

INTRODUCTION: Myeloid sarcoma is a rare tumor characterized by a tissue mass of myeloid progenitor cells occurring outside of the bone marrow. Myeloid sarcoma can occur de novo or overlap with acute myeloid leukemia (AML). As with AML, myeloid sarcoma may also present as a blast transformation of myelodysplastic syndrome or neoplasm. CASE DESCRIPTION/METHODS: A 65-year-old male was transferred to our hospital for hematochezia after a cecal polypectomy. Two days prior to transfer, the patient underwent screening colonoscopy for colorectal cancer at an outside hospital. During the procedure, a large carpeted, sessile polyp was seen overlying the cecal fold. Endoscopic removal was attempted but was unsuccessful given the polyp’s location and size. Pathology from the partially removed polyp revealed a tubulovillous adenoma. His hemoglobin was 6.5 g/dL (13.0–17.0 g/dL) and white blood cell count was 70 M/μL (4.20–5.60 M/μL). Following blood transfusions and hemodynamic stabilization, repeat colonoscopy and bone marrow biopsy were performed. The polypectomy site revealed flat, polypoid ulcerated and friable tissue with multiple areas of bleeding and clot (Figure 1). Despite hemostatic clip placement and thermal therapy to treat areas of active oozing, the lesion continued to bleed. The surgical team was activated given known residual adenomatous tissue and the patient underwent a successful right hemicolectomy. Pathology of the surgical specimen showed a tubulovillous adenoma with focal high-grade dysplasia and central ulceration with fibrinous exudate and submucosal hemorrhage. In addition, there were immature myeloid cells infiltrating the submucosa underneath this polyp. Furthermore, sheets of myeloblasts, positive for CD34 and CD117, within the submucosa also formed a separate ulcerated, plaque-like, 1.0 cm mass distal to the polyp (Figure 2). Bone marrow biopsy showed a 70% cellular marrow with nearly 20% myeloblasts. The patient had both a tubulovillous adenoma with an infiltrating adjacent myeloid sarcoma. DISCUSSION: While myeloid sarcoma can affect any organ, they most commonly infiltrate the skin or gums. Colonic involvement is extremely rare. Treatment for myeloid sarcomas is identical to that of AML, even if there no evidence of bone marrow involvement.

Patterns of leukemic transformation in patients with TP53-mutant myelodysplastic syndromes.

7054 Background: TP53 is the most frequently mutated gene in human cancers, including 7-13% of acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) patients. Although it is associated with transformation to AML in patients with MDS, the additional genomic events leading to transformation are poorly understood. Methods: We retrospectively evaluated 312 patients with TP53-mutated AML or MDS diagnosed between 2013-2016. Patient characteristics and bone marrow data, including cytogenetic and next generation sequencing information, were assessed at the time of diagnosis and progression to AML. Results: There were 151 TP53-mutated MDS patients and 161 TP53-mutated de novo AML patients with a median follow-up time of 34.1 months. Forty-one patients with TP53-mutated MDS transformed to AML. Sequencing data at transformation was available in 17 patients (41%). At diagnosis, median age was 67 with 2 patients with intermediate-risk, 7 patients with high-risk, and 32 patients with very high-risk MDS by IPSS-R. Complex karyotype was seen in 40 patients, and 12 patients had 1, 25 patients had 2, and 4 patients had 3 TP53 abnormalities. Predictors of transformation to AML include TP53 loss of heterozygosity (p = 0.008), 3 TP53 abnormalities (p = 0.049), complex cytogenetics (p = 0.023), and female gender (p = 0.002). Median time to transformation was 10.4 months. At transformation, an increase in TP53 variant allelic frequency was observed in 7 patients (41%), and new mutations, particularly NRAS, IDH1, TP53, MLL, KDM6A, TET2, and NOTCH1, were acquired by 10 patients (59%). Cytogenetic evaluation revealed identical clones in 5 patients, linear acquisition of cytogenetic abnormalities in 12 patients, and new clones in 8 patients. Patients with TP53-mutated AML from MDS also had worse median overall survival than patients with TP53-mutated de novo AML at 2.5 months vs. 5.7 months respectively (p < 0.001). Conclusions: TP53 mutations confer a worse prognosis, especially in the setting of AML transformed from MDS. This may be due to the acquisition of new mutations and cytogenetic abnormalities. Further exploration of the biological mechanisms leading to transformation in TP53-mutant MDS is warranted.

Early Detection and Molecular Characterization of Therapy-Related Leukemia in Children Reveals Patterns of Disease Transformation and Guides Future Surveillance Protocols

BackgroundTherapy-related myelodysplastic syndrome (MDS) and acute leukemias represent a major cause of non-relapse morbidity and mortality in childhood cancer survivors, and have been associated with exposure to cytotoxic therapies (e.g. radiation, alkylators, topoisomerase inhibitors). Neuroblastoma (NB) patients receive multimodality therapy with intensive chemotherapy, radiation, and immunotherapy, and have had high rates of treatment-related leukemias (Kushner, Cheung et al. 1998). Whilst specific therapeutic modalities have been associated with distinct cytogenetic and molecular abnormalities, our understanding of the relationships between timing of mutation acquisition, dynamics of clonal selection in relation to specific therapeutic modalities, and how these in unison result in overt leukemia, remains limited. Motivated to study these relationships and inform future screening guidelines, we characterized serial bone marrow (BM) samples obtained during surveillance for NB recurrence and therapy-related leukemias.MethodsWe studied a total of 219 serial samples from 55 NB patients treated at MSKCC over a 21-year period. These included 19 patients with MDS or leukemic transformation (median time following NB diagnosis 4.4 years), 15 with transient cytogenetic abnormalities (median time to abnormality 3.1 years), and 21 matched controls (median disease-free follow-up 8.1 years). On average, we analyzed 4 samples per transformation patient, representative of pre-treatment timepoints at NB diagnosis, during NB treatment, and throughout follow-up, with a lead time of 18 years - 1 month prior to transformation, and at time of leukemic transformation. Comprehensive genomic profiling with targeted gene sequencing (MSK-IMPACT Heme), RNA-seq, and Archer FusionPlex was performed to capture acquired gene mutations, chromosome-level copy number alterations (CNA), and fusion genes at the time of diagnosis. Backtracking studies were performed in longitudinal samples with complete molecular and clonal characterization.ResultsWe detected at least one disease-defining alteration in all cases with MDS or leukemic transformation at time of diagnosis, with a total of 61 putative oncogenic events across all patients (median 3 alterations per patient, range 1-12). As expected, the most frequent events were MLL fusions (n=6 patients), and mutations in TP53 (n=5 patients). The remaining cases harbored chromosomal aneuploidies or acquired gene mutations in NPM1, IDH1, PTPN11, NRAS, BCOR, CUX1, STAG2, WT1, amongst other genes, at a median variant allele frequency 24% (range 4-68%). Backtracking studies identified at least one of these mutations in 81% of patients at a sampling time point prior to diagnosis. In contrast, only two patients (2/15) from the cohort with transient cytogenetic abnormalities had acquired somatic mutations detected at a median VAF of 3%, with resolution of the molecular alterations in subsequent samples. One of the control cases also had an identified mutation, though this patient died of NB with limited hematologic follow-up.The median time of detection of a putative driver alteration was 6 months prior to leukemic transformation, with the earliest identified at 2.8 years prior to disease transformation. At least 3 cases of MLL fusions were detected 2.2, 14.5, and 20.9 months prior to diagnosis. Mutations in TP53 co-occurred with CNAs in all patients in our cohort, and has been shown to be predictive of chemoresistant disease. Mutations in TP53 were also identified in at least 2 pre-leukemic samples per patient in 4 of 5 cases, at a median VAF 5% (range 5-20%). In all of these cases, TP53 mutations preceded clinically detectable CNA. Genetic evolution led clonal dominance, which, intriguingly, often preceded disease presentation in the context of normal hematopoeisis. We also found evidence of clonal drifts, possibly as a consequence of treatment effects.ConclusionsOur preliminary data demonstrate that NB patients at risk of developing secondary leukemia can be identified by molecular profiling of BM aspirates obtained during routine disease surveillance for NB. These findings present an opportunity for the development of early detection studies for patients with pediatric malignancies undergoing intensive therapy and importantly inform studies into mechanisms of leukemic transformation and specific gene-treatment effects. DisclosuresCheung:Ymabs: Patents & Royalties.

Differential Effects of TLR1/2 and TLR2/6 Signaling on Normal and Premalignant Hematopoietic Stem and Progenitor Cells

Prior studies from our lab and others have demonstrated a role for Toll-like receptor 2 (TLR2) in regulating both normal and premalignant hematopoietic stem and progenitor cells (HSPCs), however the contributions of its binding partners, TLR1 and TLR6, remain unknown. In CD34+ bone marrow cells of patients with myelodysplastic syndrome (MDS), increased TLR2 was associated with lower-risk disease, elevated rates of apoptosis associated with improved prognosis, and enhanced survival. Conversely, increased levels of TLR6, but not TLR1, was associated with higher-risk disease and an increased percentage of bone marrow blasts (Zeng et al., Exp Cell Res 2016 and Wei et al., Leukemia 2013). These data suggest that there may be heterodimer-specific effects of TLR2 signaling on HSPCs influencing disease progression.To elucidate the unique contributions of the heterodimer pairs in MDS pathogenesis and leukemogenesis, we utilized a well-established mouse model of MDS that expresses the NUP98-HOXD13 fusion from the hematopoietic Vav-1 promoter. The “NHD13” mice recapitulate many of the salient features of human MDS and succumb to cytopenias or leukemia by 14 months of age (Lin et al., Blood 2005). Importantly, we observed significantly increased expression of TLRs 1, 2, and 6 on the c-Kit+, Sca-1+, Lineage- (“KSL”) HSPCs of the NHD13 mice, similar to the increased expression of these TLRs on CD34+ cells of MDS patients. To begin to delineate the heterodimeric differences, NHD13 mice were treated chronically with either PAM2CSK4 (PAM2), a TLR2/6-specific agonist, or PAM3CSK4 (PAM3), a TLR1/2-specific agonist, to assess the effects on cytopenias and survival. After five months of treatment, a significant increase was observed in the total number of white blood cells in NHD13 mice treated with PAM2 (p=0.007), but not PAM3 (vs. vehicle (water)-treated controls), a finding that was not recapitulated in wild-type (WT) controls. On the contrary, a significant decrease in the total number of platelets in both NHD13 and WT mice treated with PAM3 was observed as compared to vehicle-treated controls (p=0.024 and p=0.011, respectively). Further supporting the existence of heterodimer-specific differences, death was expedited in NHD13 mice treated with PAM2 as compared to those treated with PAM3 (p=0.019), with a median survival of 243 days vs. 338 for the PAM3-treated cohort. The cause of death, as determined by a hematopathologist based on cytology and blast percentage, was most often due to leukemia.To investigate the potential mechanism through which enhanced TLR2/6 signaling accelerates leukemogenesis and death in NHD13 mice, the HSPCs of premalignant NHD13 mice treated with PAM2 or PAM3 were characterized by flow cytometry and evaluated for cell cycling and cell death. Both the total number and frequency of KSL cells were significantly increased in NHD13 mice treated with PAM2 (p=0.007 and p<0.0001, respectively), but not PAM3, vs. water-treated controls. No significant changes were noted in either cell cycling or apoptosis following agonist treatment. A microarray of bone marrow KSL cells revealed that stimulation of the TLR2/6 pathway is associated with an activated c-Myc signature, suggesting that enhanced signaling through this pathway, but not TLR1/2, may enhance leukemogenesis via Myc activation. Further, the expression levels of six downstream targets of c-Myc, including BAX, APEX1, ODC1, FKBP4, NCL, and HSPD1, were significantly increased in both WT and NHD13 mice following PAM2 treatment. Evaluation of serum cytokines also revealed heterodimer-specific alterations, including increased IL-6 levels in NHD13 mice treated with PAM2, but not PAM3. These data corroborate numerous previous reports linking IL-6 to MDS pathogenesis and transformation to acute myeloid leukemia. Ongoing studies involving mass cytometry, IL-6knockout mice, and pharmacological inhibitors of both IL-6 and c-Myc aim to further elucidate the mechanism through which TLR2/6-specific activation accelerates leukemogenesis and death in the NHD13 mouse model of MDS. These studies hope to inform more targeted therapeutics that could potentially delay MDS progression and reduce off-target effects. DisclosuresNo relevant conflicts of interest to declare.

From cellular morphology to molecular and epigenetic anomalies of myelodysplastic syndromes.

Myelodysplastic syndromes (MDSs) are a myeloid neoplasm with a propensity for natural evolution or transformation to acute leukemias (AL) over time. Mechanisms for MDS transformation to AL remain poorly understood but are related to genomic instability, which affects the production of the different cell lineages. Genomic instability is also generated by dysfunctional telomeres. Indeed telomeres, the protective ends of chromosomes are the backbone of genome stability. Nuclear telomere remodeling is an early indicator of nuclear remodeling preceding the onset of genomic instability and MDS. This review aims to revisit the pathogenesis and pathophysiology of MDS from morphology and cytogenetics to molecular and epigenetic mechanisms. Furthermore, this review will highlight and discuss recent breakthroughs in dysfunctional telomeres and nuclear telomere architecture roles in the pathogenesis and physiopathology of MDS in the global context of genomic instability.

The outcome of patients with high-risk MDS achieving stable disease after treatment with 5-azacytidine: A retrospective analysis of the Hellenic (Greek) MDS Study Group.

The demethylating factor 5-azacytidine (5-AZA) improves survival in intermediate-2 and high-risk myelodysplastic syndrome (MDS) patients [according to the International Prognostic Score System (IPSS)] responding to treatment. However, the outcome of patients achieving stable disease (SD) is unclear. This retrospective study of the Hellenic MDS Study Group included 353 intermediate-2 or high IPSS risk patients treated with 5-AZA. Forty-four out of 86 (51.6%) patients achieving SD and continuing treatment with 5-AZA showed a lower risk of transformation of MDS to acute myeloid leukemia (AML) and increased overall survival (OS), compared to SD patients who discontinued the treatment (estimated median AML-free survival=38months, 95% CI=10.7-65.3 vs 15months, 95% CI=10.4-19.6, P<.001; estimated median OS=20months, 95% CI=5.5-34.5 vs 11months, 95% CI=5.8-16.2, P<.001). Moreover, SD patients continuing treatment with 5-AZA had no differences in AML-free survival compared to patients showing response to 5-AZA (estimated median AML-free survival=38months, 95% CI=10.7-65.3 vs 31months, 95% CI=23.6-38.4, P=.45; estimated median OS 20months, 95% CI=5.5-34.5 vs 25months, 95% CI=21.3-28.7, P=.50). In conclusion, MDS patients achieving SD in the first 6months of treatment with 5-AZA as best response should continue receiving 5-AZA as they may benefit from prolonged treatment.

Hedgehog/GLI1 activation leads to leukemic transformation of myelodysplastic syndrome in vivo and GLI1 inhibition results in antitumor activity.

Myelodysplastic syndromes (MDSs) are stem cell disorders with risk of transformation to acute myeloid leukemia (AML). Gene expression profiling reveals transcriptional expression of GLI1, of Hedgehog (Hh) signaling, in poor-risk MDS/AML. Using a murine model of MDS we demonstrated that constitutive Hh/Gli1 activation accelerated leukemic transformation and decreased overall survival. Hh/Gli1 activation resulted in clonal expansion of phenotypically defined granulocyte macrophage progenitors (GMPs) and acquisition of self-renewal potential in a non-self-renewing progenitor compartment. Transcriptome analysis of GMPs revealed enrichment in gene signatures of self-renewal pathways, operating via direct Gli1 activation. Using human cell lines we demonstrated that in addition to canonical Hh signaling, GLI1 is activated in a Smoothened-independent manner. GLI1 knockdown or inhibition with GANT61 resulted in decreased proliferation and clonogenic potential. Our data suggest that GLI1 activation is frequent in MDS during disease progression and inhibition of GLI1 is an attractive therapeutic target for a subset of patients.

Clinical Study of Patients with Myelodysplastic Syndrome Transformed into Acute Myeloid Leukemia

To study the biological characteristics and treatment response of patients with myelodysplastic syndrome (MDS) transformed into acute leukemia(AL). Using WHO standard method, the clinical characteristics of patients with MDS into AML were retrospectively analyzed, the related factors influencing the MDS into AML and the treatment response of patients were analyzed. Twenty-six cases (17%) of MDS were transformed into AL among 153 cases of middle and high risk MDS, all of which were AML. The median time of transformation from MDS into AML was 4 months (1-29),and these cases transformed into AML-M2, M4, M5 and M6. In these 26 cases of AML patients, the varying degrees of anemia symptom appeared, 2 cases were with marrow infiltration, 18 cases (69.2%) were with abnormal chromosome karyotype. Compared with karyotype before transformation into AML, the abnormal karyotype in 9 cases had been conversed (new karyotype or disappear once of existing karyotype). Total efficiency of individualized treatment for MDS transformed into AML was 80%. This treatment could improve the patients quality of life. Middle and high risk MDS patients are prone to be tranformed into AML. Multiple factors are involved in the transformation of MDS into AML. These patients showed the special biological characteristics and poorer prognosis. Demethylation treatment is helpful to achieve a good near-term curative effect.

Increased separase activity and occurrence of centrosome aberrations concur with transformation of MDS.

ESPL1/separase, a cysteine endopeptidase, is a key player in centrosome duplication and mitotic sister chromatid separation. Aberrant expression and/or altered separase proteolytic activity are associated with centrosome amplification, aneuploidy, tumorigenesis and disease progression. Since centrosome alterations are a common and early detectable feature in patients with myelodysplastic syndrome (MDS) and cytogenetic aberrations play an important role in disease risk stratification, we examined separase activity on single cell level in 67 bone marrow samples obtained from patients with MDS, secondary acute myeloid leukemia (sAML), de novo acute myeloid leukemia (AML) and healthy controls by a flow cytometric separase activity assay. The separase activity distribution (SAD) value, a calculated measure for the occurrence of cells with prominent separase activity within the analyzed sample, was tested for correlation with the centrosome, karyotype and gene mutation status. We found higher SAD values in bone marrow cells of sAML patients than in corresponding cells of MDS patients. This concurred with an increased incidence of aberrant centrosome phenotypes in sAML vs. MDS samples. No correlation was found between SAD values and the karyotype/gene mutation status. During follow-up of four MDS patients we observed increasing SAD values after transformation to sAML, in two patients SAD values decreased during azacitidine therapy. Cell culture experiments employing MDS-L cells as an in vitro model of MDS revealed that treatment with rigosertib, a PLK1 inhibitor and therapeutic drug known to induce G2/M arrest, results in decreased SAD values. In conclusion, the appearance of cells with unusual high separase activity levels, as indicated by increased SAD values, concurs with the transformation of MDS to sAML and may reflect separase dysregulation potentially contributing to clonal evolution during MDS progression. Separase activity measurement may therefore be useful as a novel additional molecular marker for disease monitoring.