Haploinsufficiency of RPS14 and RPS24 in 5q-Syndrome

Abstract Abstract 4964 The 5q-syndrome is a subtype of myelodysplastic syndrome, a rare disorder caused by the loss of a part of the long arm of chromosome 5, being firstly described in 1974 by Van Den Berghe; the cytogenetic characterization reports 4 types of deletion of chromosome 5 (q13-q31), (q13-q33), (q22-q25), (q32-q33) in a critical deletion region (CDR 1 and 2), that shows a reduction in gene expression of 50–60%, the aploinsufficiency includes the tumor suppressor genes, the regulation of gene splicing and apoptosis, the growth inhibitory protein, and the PDGF and p53 pathway. The CDR1 deletion involves genes encoding the 40S ribosomal subunit (D55479-CDC23, EGR1, CDC25C), while the CDR2 deletion includes several genes (SPARC, WIG-1, BMI-1, MEGF-1, RPS14, RPS24) encoding the transcription factor Egr-1/K20×20, the cytoskeletal remodeling protein, and the alphacatenin. The mechanism of the aploinsufficiency remains unresolved, but we have observed the characteristic changes Cys224-with Arg234, and the down-regulation of micro RNA-genes RPL28, EF1D, and up-regulation of several pro-apoptotic genes BAX and CAPS3, that is caused by a defect in ribosomal protein function, which is characterized by macrocytic anemia, thrombocytosis, megakaryocyte hyperplasia with nuclear hypolobation, erythroblastopenia associated with displastic abnormalities of hematopoietic stem cells/progenitor cells (HSCs/HPCs), hypogranular neutrophils or pseudo Chediak-Higashi large granules, ringed sideroblasts, excess of blasts, and increased malignancy (acute myeloid leukemia). In accordance of what recent data are currently suggesting we have also observed the mutation of the JaK2 gene and FLT3; this means that many other candidate genes may play a role in this disease and in the risk for clonal evolution and in the progression of acute myeloid leukemia. Disclosures: No relevant conflicts of interest to declare.

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Combination of Mitoxantrone,Ara-C and Homoharringtonine In Treatment of Refractory and Relapsed Acute Myeloid Leukemia

Blood ◽

10.1182/blood.v118.21.4294.4294 ◽

2011 ◽

Vol 118 (21) ◽

pp. 4294-4294

Author(s):

Jianda Hu ◽

Tingbo Liu ◽

Chunxia Cai ◽

Xinji Chen ◽

Buyuan Chen

Keyword(s):

Drug Resistance ◽

Acute Myeloid Leukemia ◽

Stem Cell ◽

Stem Cell Transplantation ◽

Cell Transplantation ◽

Median Time ◽

Myeloid Leukemia ◽

Conflicts Of Interest ◽

Hematopoietic Stem ◽

Acute Myeloid

Abstract Abstract 4294 Advances in effective chemotherapy have improved clinical outcomes in acute leukemia in recent years. 5-year survival rate approaches 50–60% for acute myeloid leukemia (AML). However, the prognosis remains poor for patients who are relapsed or refractory to first-line therapy. Drug resistance and early disease recurrence are major contributing factors in the limited survival of patients with AML. The strategy for treating these patients is through reinduction chemotherapy followed by allogeneic stem cell transplantation. New combinations of different agents were employed in refractory patients to overcome drug resistance. The current study is to evaluate the efficacy of a MAH regimen comprising Mitoxantrone,Ara-C and Homoharringtonine in refractory or relapsed AML. 37 patients aged 14–65 years with refractory or relapsed AML (15 refractory AML patients, 22 relapsed AML patients) were treated with the MAH regimen(Mitoxantrone 10mg qd, iv.gtt, for 2□‘3 days;Ara-C 100mg bid, iv.gtt, for 5□‘7 days; Homoharringtonine 4mg qd iv.gtt, for 5□‘7 days). Chemotherapy duration lasted for 5 or 7days depended on bone marrow cellurarity. 15 (40.5%)and 1 (2.7%) patients achieved complete remission (CR) and partial remission (PR) respectively. The overall response rate was 43.2%. There was no relation between remission duration and previous chemotherapy. All patients who achieved CR received a consolidation and intensification therapy. The median overall survival (OS) for all patients was 97 days (range 18–487 d). For the patients who were in CR or PR,the median relapse-free survival(RFS) was 147 days(range 4 to 341 d). All patients experienced profound myelosuppression. The most common observed side effect of the regimen was infection because of grade ‡W neutropenia, which could be observed in 33 patients(89.1%). 4 patients died in aplasia due to severe infection and brain hemorrhage. In patients achieving remission, the median time to reach absolute neutrophil count (ANC) more than 0.5×109/l was (16.0±6.4)d. Platelet levels of more than 20×109/l were achieved in a median time of (12.7±6.2)d. Nonhematological side effects, consisting mainly of gastrointestinal toxicity(21/37,56.8%) and transient liver ALT and AST increase (4/37), were generally mild to moderate and tolerated. To a conclusion, MAH regimen can be employed in treatment of the refractory or relapsed AML patients who were not responded to other regimen. It is effective and is good tolerant.It could provide some refractory patients the chance to receive hematopoietic stem cell transplantation. Disclosures: No relevant conflicts of interest to declare.

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Expression of CD56 Is an Independent Prognostic Factor to Predict Relapse in Acute Myeloid Leukemia with t(8;21): Results of Japan Adult Leukemia Study Group (JALSG) AML97 Protocol.

Blood ◽

10.1182/blood.v120.21.2511.2511 ◽

2012 ◽

Vol 120 (21) ◽

pp. 2511-2511

Author(s):

Noriyoshi Iriyama ◽

Yoshihiro Hatta ◽

Jin Takeuchi ◽

Yoshiaki Ogawa ◽

Shigeki Ohtake ◽

...

Keyword(s):

Acute Myeloid Leukemia ◽

Myeloid Leukemia ◽

Conflicts Of Interest ◽

Performance Status ◽

Univariate Analysis ◽

Rank Test ◽

Hematopoietic Stem ◽

Wbc Count ◽

Adverse Factor ◽

Acute Myeloid

Abstract Abstract 2511 Background: Although prognosis of acute myeloid leukemia (AML) with t(8;21) is better than other types of AML, outcome of the patients has not been satisfied. Previously, aberrant antigen expression has been reported as risk factor for AML with t(8;21). However, in the reported series, number of cases was not large enough and chemotherapy regimens were variable. We investigated the association of prognosis and several biomarkers including immunophenotype, WBC count, age, and performance status for large number of AML patients with t(8;21) uniformly treated in JALSG AML97 regimen. Patients and Methods: Seven hundred eighty-nine eligible AML patients were evaluated for the multicenter JALSG AML97 study. Adult patients with de novo AML except for APL, ages 15–64 years, were registered consecutively from 103 institutions that participated in JALSG from December 1997 to July 2001. One hundred forty-four patients with AML with t(8;21) were analyzed in this study with a median 1205 days of observation term from diagnosis. Complete remission (CR), relapse-free survival (RFS), and overall survival (OS) rates were analyzed by Fisher's exact test and log-rank test. Factors that would affect clinical outcome were analyzed by multivariate Cox proportional hazard regression model. Results: AML with t(8;21) frequently expressed CD19, CD34, and CD56 compared to other subtypes of AML. CD11b was rarely expressed. Expression of CD19 favorably affected on CR rate (96% in CD19 positive and 87% in negative patients, p<0.05). Univariate analysis showed WBC>20×109/L, CD19 negativity, and CD56 positivity were adverse factors for RFS. CD56 expression was the only independent adverse factor for RFS by multivariate analysis (73.7% in CD56 negative and 48.2% in CD56 positive patients at 3 yrs) although its expression did not affect on OS. There was no difference of age, sex, WBC count, presence or absence of Auer rod, performance status, or CD15 expression between CD56 positive and negative cases. Expression of CD19 was more common in CD56 negative patients (50% in CD56 negative and 30.6% in CD56 positive patients, p<0.05). Conclusions: We demonstrated that the expression of CD56 was a distinctive adverse factor in a large number of AML patients with t(8;21) treated with JALSG AML97 regimen. CD56 positive AML patients with t(8;21) are possible candidates for hematopoietic stem cell transplantation. Disclosures: No relevant conflicts of interest to declare.

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CXCR4 Invalidation Limits the MLL-ENL Induced Leucemogenesis in Vivo

Blood ◽

10.1182/blood.v120.21.4089.4089 ◽

2012 ◽

Vol 120 (21) ◽

pp. 4089-4089

Author(s):

Yanyan Zhang ◽

Hadjer Abdelouahab ◽

Aline Betems ◽

Monika Wittner ◽

William Vainchenker ◽

...

Keyword(s):

Bone Marrow ◽

Acute Myeloid Leukemia ◽

Survival Time ◽

Median Survival ◽

Median Survival Time ◽

Myeloid Leukemia ◽

Conflicts Of Interest ◽

Hematopoietic Stem ◽

Acute Myeloid

Abstract Abstract 4089 The receptor CXCR4 and its ligand SDF-1 play major physiological roles especially on hematopoietic stem cells homing and retention. Many studies have implicated CXCR4 in the invasion by tumor cells of organs that produce SDF-1. In acute myeloid leukemia, the physiological role of CXCR4 is not fully understood. We used retrovirus to express MLL-ENL oncogene in CXCR4+/+ and CXCR4−/− hematopoietic primitive cells (Lin- isolated from fetal liver) and showed that CXCR4 is dispensable for generation of immortalized colonies in vitro. To determine CXCR4 function in vivo, CXCR4+/+ and CXCR4−/− transformed cells were transplanted into lethally irradiated mice. Whatever their phenotype, the recipient developed a myelo-monocytique leukemia characterized by their expression of Gr-1 and Mac-1. As expected, all recipients of MLL-ENL transduced CXCR4+/+ cells were moribund within 35 to 80 days post transplant (median survival time: 50 days). Strikingly, recipients of MLL-ENL transduced CXCR4−/− cells showed significantly increased lifespan, with a median survival time of 90 days. The cellularity of the peripheral blood of recipients of MLL-ENL transduced cells displayed considerable increases over time although this increase was much lower in CXCR4−/− than in CXCR4+/+ chimera. Bone marrow of MLL-ENL transduced CXCR4−/− chimera had moderately decreased numbers of mononuclear cells. There were important numbers of leukemic CD45.2+/Gr1+/Mac1+/c-kit+ cells in spleen from MLL-ENL CXCR4+/+ chimera which suggested that CXCR4 is important for leukemic progenitors cells retention in the bone marrow and especially in the spleen. The homing capacity of transduced CXCR4+/+ cells is comparable to the CXCR4−/− cells. Finally, more DNA damages were found in the BM cells of MLL-ENL CXCR4−/− chimera. All these results were confirmed by treating of MLL-ENL CXCR4+/+ chimera with CXCR4 inhibitor (TN140). These results demonstrated that in absence of CXCR4, the cells transduced by oncogene MLL-ENL are capable of generating leukemia in the recipients. However, mice transplanted with MLL-ENL transduced CXCR4−/− FL cells developed acute myeloid leukemia with reduced aggressiveness and organ infiltration, which is associated with induced differentiation and DNA instability. These results indicated that the MLL-ENL progenitors are dependent on CXCR4 for their maintenance in the BM and spleen suggesting that CXCR4 inhibitors might have potential therapeutic applications. Disclosures: No relevant conflicts of interest to declare.

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Inhibition of HDAC8 Reactivates p53 and Abrogates Leukemia Stem Cell Activity in CBFβ-SMMHC Associated Acute Myeloid Leukemia

Blood ◽

10.1182/blood.v124.21.363.363 ◽

2014 ◽

Vol 124 (21) ◽

pp. 363-363

Author(s):

Jing Qi ◽

Qi Cai ◽

Sandeep Singh ◽

Ling Li ◽

Hongjun Liu ◽

...

Keyword(s):

Bone Marrow ◽

Acute Myeloid Leukemia ◽

Myeloid Leukemia ◽

Bone Marrow Cells ◽

Conflicts Of Interest ◽

Cell Activity ◽

Disease Free Survival ◽

Hematopoietic Stem ◽

The Impact ◽

Acute Myeloid

Abstract The inv(16)-created CBFβ-SMMHC fusion protein inhibits differentiation of hematopoietic stem and progenitor cells (HSPCs) and creates pre-leukemic populations predisposed to acute myeloid leukemia (AML) transformation. However, the molecular mechanism underlying the leukemogenic function of CBFβ-SMMHC has been elusive. Given the low TP53 mutation rate in AML, alternative mechanisms disrupting p53 function are expected. We showed thatCBFβ-SMMHC impairs p53 acetylation and p53 target gene activation through formation of an aberrant protein complex with p53 and HDAC8 (Blood, 120: A772; 122(21): 224). We now show that CBFβ-SMMHC binds to p53 and HDAC8 independently through distinct regions and that HDAC8 mediates the deacetylation of p53 associated with CBFβ-SMMHC. In addition, we generated mice carrying a floxed Hdac8 (Hdac8f) allele and crossed with Cbfb56M/+/Mx1-Cre (Kuo YH et al, Cancer Cell 2006). Deletion of Hdac8 signifiacntly (p<0.0001) reduced the incidence of AML and prolonged disease-free survival. Pharmacologic inhibition of HDAC8 activity with HDAC8-selective inhibitors (HDAC8i) reactivates p53 and selectively induces apoptosis of inv(16)+ AML CD34+ cells while sparing normal HSPCs. To test the effect of HDAC8i on LSC engraftment and leukemia-initiating capacity, we generated Cbfb56M/+/Mx1-Cre mice with a Cre-reporter line expressing tdTomato fluorescence protein following Cre-mediated recombination. AML cells (dTomato+/cKit+) treated with HDAC8i (22d) ex vivo showed reduced engraftment (p=0.025) and enhanced survival (p=0.025) in transplanted mice. To examine whether HDAC8i 22d treatment affects the engraftment capacity on surviving cells, we transplanted equal number (2 x 106) of AML cells treated with either 22d or vehicle in another cohort of mice (n=4). We show that HDAC8i 22d treatment reduced the engraftment of dTomato+/cKit+ AML cells and enhanced survival, suggesting that the engraftment capacity is altered in addition to reducing AML cell survival. We next performed preclinical studies to determine the efficacy of in vivo administration of HDAC8i 22d. AML transplanted mice were randomized into two groups, one group treated with vehicle and the other treated with HDAC8i 22d for 2 weeks. Flow cytometry analysis revealed significantly reduced frequency (p=0.0097) and number (p=0.0101) of dTomato+/cKit+ AML cells in the bone marrow and spleen of 22d treated mice compared to vehicle treated group. To further assess the impact on LSC activity, we transplanted bone marrow cells from these treated mice into secondary recipients and analyzed for AML engraftment. Significant reduction in the frequency (p<0.0001) and the number (p=0.0006) of dTomato+/cKit+ AML cells was observed in the bone marrow and spleen. Furthermore, HDAC8i 22d treated transplants showed no signs of leukemia while vehicle treated transplants are moribund with aggressive AML. These results indicate that HDAC8 inhibition by 22d treatment effectively eliminates engraftment and leukemia-initiating capacity of AML LSCs. In conclusion, our studies identify a novel post-translational p53-inactivating mechanism and demonstrate selective HDAC8 inhibition as a promising approach to target inv(16)+ AML LSCs. Disclosures No relevant conflicts of interest to declare.

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Clonal Evolution of Pre-Leukemic Hematopoietic Stem Cells in Human Acute Myeloid Leukemia

Blood ◽

10.1182/blood.v126.23.sci-11.sci-11 ◽

2015 ◽

Vol 126 (23) ◽

pp. SCI-11-SCI-11

Author(s):

Ravi Majeti

Keyword(s):

Acute Myeloid Leukemia ◽

Progenitor Cells ◽

Clinical Outcomes ◽

Myeloid Leukemia ◽

De Novo ◽

Clonal Evolution ◽

Founder Mutations ◽

Hematopoietic Stem ◽

Relapsed Disease ◽

Acute Myeloid

Acute myeloid leukemia (AML) is an aggressive malignancy of hematopoietic progenitors with poor clinical outcomes. Recent genome-scale sequencing efforts have determined that on average, an individual AML case is associated with 5 somatic mutations in recurrently mutated genes. This finding raises the important question of how AML develops from normal hematopoietic stem and progenitor cells. Given that AML is characterized by the sequential acquisition of genetic lesions in a single lineage of cells, and that all cells in the myeloid lineage, apart from HSC, are short-lived, we proposed a model in which serial acquisition of mutations occurs in self-renewing HSC. We investigated this model and the nature of founder mutations through the genomic analysis of de novo AML and patient-matched residual HSC. Using exome sequencing, we defined mutations present in individual AML genomes from 19 cases, and screened for these mutations in the residual HSC. We identified multiple mutations present in residual HSC retaining normal multilineage differentiation in vivo, including mutations in IDH1/2, TET2, DNMT3A, and genes encoding the subunits of the cohesin complex. Through single cell analysis, we determined that as we hypothesized, a clonal progression of multiple mutations occurs in HSC. From these studies, we identified patterns of mutation acquisition in human AML. Our findings support a model in which mutations in "landscaping" genes, involved in global chromatin changes such as DNA methylation, histone modification, and chromatin looping, occur early in the evolution of AML, while mutations in "proliferative" genes such as FLT3 and KRAS occur late. Using this approach, we identified pre-leukemic HSC in a larger cohort of AML patients, and determined that their frequency within the stem cell compartment at the time of diagnosis varied widely from undetectable to nearly 100% of the cells. Stratifying these patients into two groups with either high or low frequencies of pre-leukemic HSC demonstrated that patients in the high group had much worse overall and relapse-free survival than those in the low group, indicating that the presence of pre-leukemic HSC may be critical for eventual clinical outcomes. To further investigate the response of pre-leukemic HSC to treatment, we analyzed the persistence of pre-leukemic mutations in patients in remission and found CD34+ progenitor cells and various mature cells that harbor pre-leukemic mutations. These findings indicate that pre-leukemic HSC can survive induction chemotherapy, identifying these cells as a potential reservoir for the re-evolution of relapsed disease. Finally, through the study of several cases of relapsed AML, we demonstrate various evolutionary patterns for the generation of relapsed disease, and show that some of these patterns are consistent with involvement of pre-leukemic HSC. Thus, our studies of pre-leukemic HSC reveal the clonal evolution of AML genomes from founder mutations, suggest a potential mechanism contributing to relapse, and constitute a cellular reservoir that may need to be targeted for more durable remissions. Disclosures Majeti: Forty Seven, Inc.: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees.

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Clonal Evolution of Preleukemic Hematopoietic Stem Cells Precedes Human Acute Myeloid Leukemia

Science Translational Medicine ◽

10.1126/scitranslmed.3004315 ◽

2012 ◽

Vol 4 (149) ◽

pp. 149ra118-149ra118 ◽

Cited By ~ 385

Author(s):

M. Jan ◽

T. M. Snyder ◽

M. R. Corces-Zimmerman ◽

P. Vyas ◽

I. L. Weissman ◽

...

Keyword(s):

Stem Cells ◽

Acute Myeloid Leukemia ◽

Hematopoietic Stem Cells ◽

Myeloid Leukemia ◽

Clonal Evolution ◽

Hematopoietic Stem ◽

Human Acute Myeloid Leukemia ◽

Acute Myeloid

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High IDH1 Expression Is Associated with a Poor Prognosis in Cytogenetically Normal Acute Myeloid Leukemia

Blood ◽

10.1182/blood.v124.21.5314.5314 ◽

2014 ◽

Vol 124 (21) ◽

pp. 5314-5314 ◽

Cited By ~ 1

Author(s):

Qiu-Ling Ma ◽

Jing-Han Wang ◽

Yun-gui Wang ◽

Chao Hu ◽

Qi-Tian Mu ◽

...

Keyword(s):

Acute Myeloid Leukemia ◽

Myeloid Leukemia ◽

Poor Prognosis ◽

Prognostic Value ◽

Conflicts Of Interest ◽

Remission Rate ◽

Strong Association ◽

Gene Mutations ◽

Micro Rna ◽

Acute Myeloid

Abstract ABSTRACT The prognostic value of IDH1 mutations has been systematically evaluated in acute myeloid leukemia (AML) patients recently. However, the role of IDH1 expression in AML is still under exploration. To investigate the clinical significance, we analyzed the IDH1 expression in 320 patients with cytogenetically normal AML (CN-AML) by quantitative real-time reverse-transcription polymerase chain reaction (qRT-PCR). High expression of IDH1 was predominant in patients with FLT3-ITD and DNMT3A mutations, and less prevalent in cases with CEBPA double allele mutations. Strong association was observed between high IDH1 expression and low expression of micro-RNA 181 family. Prognosis was adversely affected by high IDH1 expression with shorter overall survival (OS) and event free survival (EFS) in the context of clinical characteristics including age, WBC, and gene mutations of NPM1, FLT3-ITD, CEBPA, IDH1, IDH2, and DNMT3A in CN-AML. Moreover, the clinical outcome of IDH1 expression in terms of OS, EFS and complete remission rate still remained in multivariate models in CN-AML. Importantly, the prognostic value was validated using the published microarray data from 79 adult patients treated according to the German AMLCG-1999 protocol. Our results demonstrated that high IDH1expression is associated with a poor prognosis of CN-AML. Disclosures No relevant conflicts of interest to declare.

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Combination of Cladribine, Cytarabine and Topotecan (CLAT) for Relapsed or Refractory Acute Myeloid Leukemia

Blood ◽

10.1182/blood.v126.23.4897.4897 ◽

2015 ◽

Vol 126 (23) ◽

pp. 4897-4897

Author(s):

Xiaomei Chen ◽

Jianyu Weng ◽

Yulian Wang ◽

Chengxin Deng ◽

Chengwei Luo ◽

...

Keyword(s):

Acute Myeloid Leukemia ◽

Natural Science ◽

Myeloid Leukemia ◽

Conflicts Of Interest ◽

Science And Technology ◽

Technology Planning ◽

Hematopoietic Stem ◽

Planning Project ◽

Refractory Acute Myeloid Leukemia ◽

Acute Myeloid

Abstract Xiaomei Chen and Jianyu Weng contributed equally to this study. The outcomes ofrelapsed or refractory acute myeloid leukemia (RR-AML) are poor and effective salvage regimens are urgently needed. We present a study of 14 patients with RR-AML (median age 42years, range 18-65years; male n=12, female n= 2) treated with CLAT regimen, which consisted of cladribine 5mg/m² per day i.v. 2-3 hour on days 1-5, cytarabine 1.0g/m² per day i.v. 4 hours after cladribine on days 1-5, topotecan 1.25mg/m² per day i.v. 4 hours after cytarabine on days1-5 and G-CSF 300ug per day subcutaneous injection on days until neutrophile granulocyte recovery. Total of fourteen patients were included into the study from June 2013 to June 2015, Two (14.3%) patients were relapsed and twelve (85.7%) patients were refractory, 4 of 14 patients were relapsed or refractory after allogeneic-HSCT. Two patients died of invasive fungal infection before the assessment. Seven patients (58.3%) achieved complete remission (CR), and one patient (8.3%) achieved partial remission (PR), the rest patients (33.3%) did not respond (NR). The overall response rate was 66.7%. Following CLAT treatment, four patients with CR underwent allogeneic hematopoietic stem cell transplantation (HSCT) or microtransplantation. The median relapse-free survival (RFS) for RR-AML patients receiving CLAT regimen was 8.6 (range 2-16) months. Thirteen patients developed grade 4 granulocytopenia and thrombocytopenia, the median duration was 13(range 2 to 21) days and12 (range 2 to 21) days, respectively. The most common non-hematological side effects included nausea, vomiting, diarrhoea, and were grade 1/2. The CLAT regimen seems promising for the treatment of patients, and it was well tolerated. This regimen offers an alternative treatment for those patients with RR-AML who have received severe intensive treatment, especially with anthracycline-containing chemotherapy. The project was sponsored by grants from National Natural Science Foundation of China (No. 30972790; No.81270648; No.81370665; No.81300446) Provincial Natural Science Foundation of Guangdong (No. S2012010009560) Provincial Science and Technology Planning Project of Guangdong (No.2013B021800186; No.2013B021800201), and Science and Technology Planning Project of Guangzhou (No. 201400000003-4, 201400000003-1). Disclosures No relevant conflicts of interest to declare.

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C/EBPα-Induced MicroRNA 30c Inactivates Notch1 During Granulopoiesis and Is Downregulated In Acute Myeloid Leukemia

Blood ◽

10.1182/blood.v118.21.2368.2368 ◽

2011 ◽

Vol 118 (21) ◽

pp. 2368-2368

Author(s):

Christiane Katzerke ◽

Vikas Madan ◽

Dennis Gerloff ◽

Daniela Braeuer-Hartmann ◽

Jens-Uwe Hartmann ◽

...

Keyword(s):

Acute Myeloid Leukemia ◽

Myeloid Leukemia ◽

Bone Marrow Cells ◽

Conflicts Of Interest ◽

Mrna Level ◽

Granulocytic Differentiation ◽

Hematopoietic Stem ◽

Knock Out ◽

Human Cd34 ◽

Acute Myeloid

Abstract Abstract 2368 The transcription factor CCAAT Enhancer Binding Protein alpha (C/EBPα) is crucial for normal granulopoiesis and frequently disrupted in acute myeloid leukemia (AML). Loss of expression or function of C/EBPα leads to a block of myeloid differentiation. MicroRNAs inhibiting translation of mRNA into protein were identified as critical players in stem cell development. We and others have already shown that C/EBPα exerts its effects by regulating microRNAs such as miR-223 and miR-34a. In a global microRNA-array screen we found miR-30c as a novel target of C/EBPα during granulocytic differentiation. Wild-type C/EBPα-p42 upregulates miR-30c expression, whereas the C/EBPα-p30 mutant, found in AML, does not. Furthermore, G-CSF upregulates miR-30c expression during granulocytic differentiation of primary human CD34-positive progenitor cells. C/EBPα induces miR-30c and downregulates Notch1, a putative target of miR-30c, on protein, but not mRNA level. A block of miR-30c by LNAs prevents C/EBPα–induced downregulation of Notch1 protein expression. miR-30c is a tumor suppressor and downregulated in various subtypes of AML. In mice, miR-30c shows a high expression in LSK (including hematopoietic stem cells), GMP (granulocytic monocytic precursors) and granulocytes. An induced knock-out of C/EBPα in mice leads to a significantly downregulation of miR-30c expression in bone marrow cells. Our data indicates that C/EBPα-induced miR-30c inactivates Notch1 during granulopoiesis and is downregulated in AML. These data reveal the importance of deregulated microRNA expression in leukemia and may provide novel biomarkers and therapeutic targets in AML. Disclosures: No relevant conflicts of interest to declare.

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Preclinical Efficacy of MEK Inhibition in Nras Mutant Acute Myeloid Leukemia

Blood ◽

10.1182/blood.v124.21.3753.3753 ◽

2014 ◽

Vol 124 (21) ◽

pp. 3753-3753

Author(s):

Michael R. Burgess ◽

Eugene Hwang ◽

Ari J Firestone ◽

Tannie Huang ◽

Jin Xu ◽

...

Keyword(s):

Acute Myeloid Leukemia ◽

Myeloid Leukemia ◽

Conflicts Of Interest ◽

Ras Signaling ◽

Hematopoietic Stem ◽

Mek Inhibitors ◽

Mek Inhibition ◽

Primary Mouse ◽

Acute Myeloid

Abstract Oncogenic NRAS mutations are highly prevalent in hematologic malignancies. In acute myeloid leukemia (AML), genetic analysis supports the hypothesis that NRAS mutations cooperate with antecedent molecular lesions in leukemogenesis. Furthermore, NRAS mutations identified at diagnosis may disappear at relapse, raising questions regarding the potential clinical benefits of inhibiting oncogenic N-Ras in AML. To directly investigate the consequences of Nras inactivation in normal hematopoiesis, we used the Mx1-Cre transgene to inactivate a conditional mutant Nras allele and analyzed hematopoiesis and hematopoietic stem and progenitor cells (HSPC) under normal and stressed conditions. We show that HSPCs lacking Nras expression are functionally equivalent to normal HSPCs in the adult mouse. Importantly, shRNA-mediated knockdown in human AML cell lines and primary mouse leukemias with oncogenic NRAS/Nras mutations revealed dependence on continued oncogene expression in vitro and in vivo. Next, we interrogated the functional consequences of pharmacologic inhibition of the canonical Ras effector pathways, the mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K) pathways,alone and in combination. Recipient mice transplanted with five independent primary mouse AMLs generated by infecting NrasG12D “knock in” mice with the MOL4070LTR retrovirus (Li et al, Blood 2011; 117:2022) were treated with the allosteric MEK inhibitors PD0325901 (PD901) or trametinib or the PI3K inhibitor GDC-0941. Both MEK inhibitors significantly prolonged survival and reduced proliferation and blast colony formation, but did not induce apoptosis, differentiation, or promote clonal evolution. PI3K inhibition alone was ineffective in vivo and combinations of MEK and PI3K inhibitors were no better than MEK inhibition alone. All mice ultimately succumbed from progressive leukemia. These data, along with observations that Nras is dispensable for normal hematopoiesis, validate oncogenic N-Ras signaling as a therapeutic target in AML and support testing combination regimens that include MEK inhibitors in leukemias harboring NRAS mutations. Disclosures No relevant conflicts of interest to declare.

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