Acute Myeloid Leukemia Export Mitochondria in Extracellular Vesicles Which Induces Pro-Tumoral Changes in Bone Marrow Macrophages

It is envisioned that improved understanding of the dependency of acute myeloid leukemia (AML) on its tumour microenvironment within the bone marrow could be exploited to offer new treatment strategies and better patient outcomes. Previously we have shown that the bone marrow (BM) microenvironment supports AML growth and survival, specifically via functional mitochondrial transfer from stromal cells to AML blasts (Marlein 2017 Blood and Abdul Aziz 2019 Blood). The increase in mitochondria in AML theoretically presents a cell intrinsic problem; accumulation of excess and dysfunctional mitochondria can induce cell death via increased reactive oxygen species and apoptotic caspases (Kroemer 2007 Physiol Rev). As such, we examine the mechanisms by which AML blasts manage excess and dysfunctional mitochondria and the impact of this process on the supporting bone marrow microenvironment. Primary AML blasts and primary AML bone marrow stromal cells (BMSC) were isolated from the bone marrow of patients. Co-culture experiments show that primary AML blasts (cultured with BMSC) maintain constant levels of mitochondria despite continuous uptake of mitochondria from BMSC. Furthermore, a combination of proteomics, confocal microscopy, image cytometry and dynamic light scattering shows that AML actively export mitochondria in large extracellular vesicles (EVs), approximately 0.6micron-1.5micron in diameter, a process which maintains a steady state of mitochondrial content in the blasts. To track the recipient cell for large EV packaged AML derived mitochondria, patient derived AML were transduced with rLV.EF.mCherry-mito-9 lentivirus which fluorescently tags the mitochondria, and then transplanted into NSG mice. BM was extracted from engrafted mice and various cell populations were analysed for increases in mCherry fluorescence as evidence of AML derived mitochondria uptake. Murine F4/80+/GR1-/CD115intBM macrophages had increased mCherry fluorescence but not mouse CD45-/CD31-/Ter119-/CD105+/CD140a+BMSC, CD45-/Ter119-/CD31+endothelial cells or CD45+leukocytes. To determine the impact of AML derived mitochondria containing EVs on the function of the BM macrophages we first isolated the AML derived mitochondrial containing EVs using cell sorting for mCherry fluorescence and then BM derived macrophages (BMDM) were incubated with EVs containing mitochondria or EV with no mitochondria and assessed for changes in pro-inflammatory genes. IL-6, IL-1B, CXLC9 and CXCL10 were all induced in BMDM by EV containing mitochondria at 24 hours post incubation. However, repeated exposure of BMDM with EV containing mitochondria resulted in significantly lower levels of IL-6, IL-1B, CXLC9 and CXCL10 upregulation. Moreover, repeated exposure of BMDM to EV containing mitochondria resulted in reduced phagocytic potential compared to control BMDM, suggesting exhaustion or senescence. To determine if AML induced BM macrophage senescence we used a syngeneic model of AML, HOXA9/Meis1 or MN1 and lineage negative cells as control. Animals were sacrificed 35 days post AML injection and BM macrophages were isolated and senescent markers were analysed by real-time PCR. p16ink4a and p21 were both upregulated in BM macrophages from HOXA9/Meis1 or MN1 engrafted animals. Data indicates that mitochondrial mass in AML blasts is maintained in equipoise through export of mitochondria in large EVs. In addition, we show that AML derived EVs containing mitochondria function as a signal which changes the function of BM macrophages, towards a senescent phenotype which promotes AML blast survival and proliferation. Disclosures Bowles: Abbvie: Research Funding; Janssen: Research Funding. Rushworth:Abbvie: Research Funding; Janssen: Research Funding.

Download Full-text

Alterations in multipotent mesenchymal stromal cells from the bone marrow of acute myeloid leukemia patients at diagnosis and during treatment

Leukemia & Lymphoma ◽

10.1080/10428194.2018.1554861 ◽

2019 ◽

Vol 60 (8) ◽

pp. 2042-2049

Author(s):

Irina N. Shipounova ◽

Nataliya A. Petinati ◽

Alexey E. Bigildeev ◽

Tamara V. Sorokina ◽

Larisa A. Kuzmina ◽

...

Keyword(s):

Bone Marrow ◽

Acute Myeloid Leukemia ◽

Mesenchymal Stromal Cells ◽

Stromal Cells ◽

Myeloid Leukemia ◽

Multipotent Mesenchymal Stromal Cells ◽

Acute Myeloid

Download Full-text

c-Myc plays part in drug resistance mediated by bone marrow stromal cells in acute myeloid leukemia

Leukemia Research ◽

10.1016/j.leukres.2014.11.004 ◽

2015 ◽

Vol 39 (1) ◽

pp. 92-99 ◽

Cited By ~ 41

Author(s):

Bing Xia ◽

Chen Tian ◽

Shanqi Guo ◽

Le Zhang ◽

Dandan Zhao ◽

...

Keyword(s):

Bone Marrow ◽

Drug Resistance ◽

Acute Myeloid Leukemia ◽

Stromal Cells ◽

Bone Marrow Stromal Cells ◽

Myeloid Leukemia ◽

Marrow Stromal Cells ◽

Acute Myeloid

Download Full-text

Acute myeloid leukemia induces protumoral p16INK4a-driven senescence in the bone marrow microenvironment

Blood ◽

10.1182/blood-2018-04-845420 ◽

2019 ◽

Vol 133 (5) ◽

pp. 446-456 ◽

Cited By ~ 17

Author(s):

Amina M. Abdul-Aziz ◽

Yu Sun ◽

Charlotte Hellmich ◽

Christopher R. Marlein ◽

Jayna Mistry ◽

...

Keyword(s):

Bone Marrow ◽

Acute Myeloid Leukemia ◽

Stromal Cells ◽

Myeloid Leukemia ◽

Stromal Cell ◽

Cell Senescence ◽

Senescent Phenotype ◽

Age Related ◽

Acute Myeloid

Abstract Acute myeloid leukemia (AML) is an age-related disease that is highly dependent on the bone marrow (BM) microenvironment. With increasing age, tissues accumulate senescent cells, characterized by an irreversible arrest of cell proliferation and the secretion of a set of proinflammatory cytokines, chemokines, and growth factors, collectively known as the senescence-associated secretory phenotype (SASP). Here, we report that AML blasts induce a senescent phenotype in the stromal cells within the BM microenvironment and that the BM stromal cell senescence is driven by p16INK4a expression. The p16INK4a-expressing senescent stromal cells then feed back to promote AML blast survival and proliferation via the SASP. Importantly, selective elimination of p16INK4a+ senescent BM stromal cells in vivo improved the survival of mice with leukemia. Next, we find that the leukemia-driven senescent tumor microenvironment is caused by AML-induced NOX2-derived superoxide. Finally, using the p16-3MR mouse model, we show that by targeting NOX2 we reduced BM stromal cell senescence and consequently reduced AML proliferation. Together, these data identify leukemia-generated NOX2-derived superoxide as a driver of protumoral p16INK4a-dependent senescence in BM stromal cells. Our findings reveal the importance of a senescent microenvironment for the pathophysiology of leukemia. These data now open the door to investigate drugs that specifically target the “benign” senescent cells that surround and support AML.

Download Full-text

EZH2 Mutations and Impact on Clinical Outcome Analyzed in 1604 Patients with Acute Myeloid Leukemia

Blood ◽

10.1182/blood-2018-99-114421 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 1528-1528

Author(s):

Sebastian Stasik ◽

Jan Moritz Middeke ◽

Michael Kramer ◽

Christoph Rollig ◽

Alwin Krämer ◽

...

Keyword(s):

Bone Marrow ◽

Acute Myeloid Leukemia ◽

Board Of Directors ◽

Myeloid Leukemia ◽

Research Funding ◽

Employment Equity ◽

Advisory Committees ◽

Mutational Status ◽

Equity Ownership ◽

Acute Myeloid

Abstract Purpose: The enhancer of zeste homolog 2 (EZH2) is a histone methyltransferase and key epigenetic regulator involved in transcriptional repression and embryonic development. Loss of EZH2 activity by inactivating mutations is associated with poor prognosis in myeloid malignancies such as MDS. More recently, EZH2 inactivation was shown to induce chemoresistance in acute myeloid leukemia (AML) (Göllner et al., 2017). Data on the frequency and prognostic role of EZH2-mutations in AML are rare and mostly confined to smaller cohorts. To investigate the prevalence and prognostic impact of this alteration in more detail, we analyzed a large cohort of AML patients (n = 1604) for EZH2 mutations. Patients and Methods: All patients analyzed had newly diagnosed AML, were registered in clinical protocols of the Study Alliance Leukemia (SAL) (AML96, AML2003 or AML60+, SORAML) and had available material at diagnosis. Screening for EZH2 mutations and associated alterations was done using Next-Generation Sequencing (NGS) (TruSight Myeloid Sequencing Panel, Illumina) on an Illumina MiSeq-system using bone marrow or peripheral blood. Detection was conducted with a defined cut-off of 5% variant allele frequency (VAF). All samples below the predefined threshold were classified as EZH2 wild type (wt). Patient clinical characteristics and co-mutations were analyzed according to the mutational status. Furthermore, multivariate analysis was used to identify the impact of EZH2 mutations on outcome. Results: EZH2-mutations were found in 63 of 1604 (4%) patients, with a median VAF of 44% (range 6-97%; median coverage 3077x). Mutations were detected within several exons (2-6; 8-12; 14-20) with highest frequencies in exons 17 and 18 (29%). The majority of detected mutations (71% missense and 29% nonsense/frameshift) were single nucleotide variants (SNVs) (87%), followed by small indel mutations. Descriptive statistics of clinical parameters and associated co-mutations revealed significant differences between EZH2-mut and -wt patients. At diagnosis, patients with EZH2 mutations were significantly older (median age 59 yrs) than EZH2-wt patients (median 56 yrs; p=0.044). In addition, significantly fewer EZH2-mut patients (71%) were diagnosed with de novo AML compared to EZH2-wt patients (84%; p=0.036). Accordingly, EZH2-mut patients had a higher rate of secondary acute myeloid leukemia (sAML) (21%), evolving from prior MDS or after prior chemotherapy (tAML) (8%; p=0.036). Also, bone marrow (and blood) blast counts differed between the two groups (EZH2-mut patients had significantly lower BM and PB blast counts; p=0.013). In contrast, no differences were observed for WBC counts, karyotype, ECOG performance status and ELN-2017 risk category compared to EZH2-wt patients. Based on cytogenetics according to the 2017 ELN criteria, 35% of EZH2-mut patients were categorized with favorable risk, 28% had intermediate and 37% adverse risk. No association was seen with -7/7q-. In the group of EZH2-mut AML patients, significantly higher rates of co-mutations were detected in RUNX1 (25%), ASXL1 (22%) and NRAS (25%) compared to EZH2-wt patients (with 10%; 8% and 15%, respectively). Vice versa, concomitant mutations in NPM1 were (non-significantly) more common in EZH2-wt patients (33%) vs EZH2-mut patients (21%). For other frequently mutated genes in AML there was no major difference between EZH2-mut and -wt patients, e.g. FLT3ITD (13%), FLT3TKD (10%) and CEBPA (24%), as well as genes encoding epigenetic modifiers, namely, DNMT3A (21%), IDH1/2 (11/14%), and TET2 (21%). The correlation of EZH2 mutational status with clinical outcomes showed no effect of EZH2 mutations on the rate of complete remission (CR), relapse free survival (RFS) and overall survival (OS) (with a median OS of 18.4 and 17.1 months for EZH2-mut and -wt patients, respectively) in the univariate analyses. Likewise, the multivariate analysis with clinical variable such as age, cytogenetics and WBC using Cox proportional hazard regression, revealed that EZH2 mutations were not an independent risk factor for OS or RFS. Conclusion EZH mutations are recurrent alterations in patients with AML. The association with certain clinical factors and typical mutations such as RUNX1 and ASXL1 points to the fact that these mutations are associated with secondary AML. Our data do not indicate that EZH2 mutations represent an independent prognostic factor. Disclosures Middeke: Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Abbvie: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees. Rollig:Bayer: Research Funding; Janssen: Research Funding. Scholl:Jazz Pharma: Membership on an entity's Board of Directors or advisory committees; Abbivie: Other: Travel support; Alexion: Other: Travel support; MDS: Other: Travel support; Novartis: Other: Travel support; Deutsche Krebshilfe: Research Funding; Carreras Foundation: Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees. Hochhaus:Pfizer: Research Funding; Incyte: Research Funding; Novartis: Research Funding; Bristol-Myers Squibb: Research Funding; Takeda: Research Funding. Brümmendorf:Janssen: Consultancy; Takeda: Consultancy; Novartis: Consultancy, Research Funding; Merck: Consultancy; Pfizer: Consultancy, Research Funding. Burchert:AOP Orphan: Honoraria, Research Funding; Bayer: Research Funding; Pfizer: Honoraria; Bristol Myers Squibb: Honoraria, Research Funding; Novartis: Research Funding. Krause:Novartis: Research Funding. Hänel:Amgen: Honoraria; Roche: Honoraria; Takeda: Honoraria; Novartis: Honoraria. Platzbecker:Celgene: Research Funding. Mayer:Eisai: Research Funding; Novartis: Research Funding; Roche: Research Funding; Johnson & Johnson: Research Funding; Affimed: Research Funding. Serve:Bayer: Research Funding. Ehninger:Cellex Gesellschaft fuer Zellgewinnung mbH: Employment, Equity Ownership; Bayer: Research Funding; GEMoaB Monoclonals GmbH: Employment, Equity Ownership. Thiede:AgenDix: Other: Ownership; Novartis: Honoraria, Research Funding.

Download Full-text

Expression of Angiopoietins and Their Receptor Tie2 in the Bone Marrow of Patients with Acute Myeloid Leukemia.

Blood ◽

10.1182/blood.v108.11.1894.1894 ◽

2006 ◽

Vol 108 (11) ◽

pp. 1894-1894

Author(s):

Christoph Schliemann ◽

Ralf Bieker ◽

Teresa Padro ◽

Torsten Kessler ◽

Heike Hintelmann ◽

...

Keyword(s):

Bone Marrow ◽

Acute Myeloid Leukemia ◽

Myeloid Leukemia ◽

Critical Role ◽

Angiogenic Factor ◽

Term Survival ◽

Bone Marrow Biopsies ◽

Cox Regression Analysis ◽

The Impact ◽

Acute Myeloid

Abstract Angiopoietin-1 (Ang-1) and its natural antagonist Angiopoietin-2 (Ang-2), both ligands for the receptor tyrosine kinase Tie2, are known to play an essential role in normal and pathological angiogenesis. However, the importance of angiopoietin signaling in the pathophysiology of hematologic neoplasias such as acute myeloid leukemia (AML) remains to be elucidated. We investigated the expression of Ang-1, Ang-2 and Tie2 by immunohistochemical analyses in bone marrow biopsies of 64 adult patients with newly diagnosed AML and correlated angiogenic factor expression with clinicopathological variables and long-term survival. Expression of Ang-2 was significantly increased in the bone marrow of AML patients (median [interquartile ranges]: 4.7 [3.3 – 5.7] AU [arbitrary units]) as compared with 16 control patients (1.5 [1.5 – 1.8] AU; P < 0.0001). In contrast, Ang-1 expression levels in AML patients did not differ from those found in controls. Thus, we observed a reversal of the Ang-1 and Ang-2 expression balance in the neoplastic bone marrow (Ang-2:Ang-1 ratio: 1.73) as compared with normal bone marrow (0.51; P < 0.0001). Furthermore, the angiopoietin receptor Tie2 was significantly overexpressed in leukemic blasts (3.8 [2.8 – 4.9] AU vs. 1.8 [1.6 – 2.3] AU; P < 0.0001). Patients expressing high levels of Ang-2 showed significantly longer overall survival (OS) than those with low Ang-2 levels (52.7 vs. 14.7 months; P = 0.039). The impact of Ang-2 expression on OS was especially evident in AML patients simultaneously expressing low levels of Ang-1 (P = 0.0298). Multivariate Cox regression analysis revealed karyotype and Ang-2 expression as independent prognostic factors for OS (hazard ratio [CI]: 3.06 [1.39 – 6.70] and 0.31 [0.14 – 0.69], respectively; P < 0.01). In conclusion, these data provide evidence that the alteration of angiopoietin balance in favor of Ang-2 may play a critical role in the pathophysiology of AML. Furthermore, high pre-therapeutic bone marrow Ang-2 levels indicate a favorable prognosis in polychemotherapy treated AML by a yet unknown mechanism.

Download Full-text

Targeted Intravenous Busulfan and Fludarabine Allogeneic Transplantation Conditioning in Acute Myeloid Leukemia.

Blood ◽

10.1182/blood.v114.22.2290.2290 ◽

2009 ◽

Vol 114 (22) ◽

pp. 2290-2290

Author(s):

Joseph A. Pidala ◽

Jongphil Kim ◽

Claudio Anasetti ◽

Melissa Alsina ◽

Ernesto Ayala ◽

...

Keyword(s):

Bone Marrow ◽

Overall Survival ◽

Acute Myeloid Leukemia ◽

Myeloid Leukemia ◽

Research Funding ◽

Large Series ◽

Myelogenous Leukemia ◽

Secondary Aml ◽

Relapsed Disease ◽

Acute Myeloid

Abstract Abstract 2290 Poster Board II-267 Reduced and intermediate intensity conditioning with allogeneic hematopoietic cell transplantation (HCT) offers promise to effectively control hematologic malignancies, while limiting treatment related toxicity and mortality (TRM). We aimed to examine the efficacy of IV targeted Busulfan and Fludarabine (IV-Bu/Flu) in a large series of adults with exclusively acute myelogenous leukemia (AML). One hundred adults (median age 48) with AML (CR1 49, CR2 25, REL1 8, REL2 1, PIF 16, untreated 1) were treated with Busulfan 130-145 mg/m2/day for four days with pharmacokinetic targeting on the final two days to achieve an area under the curve (AUC) of 5300 (+/-10%) μmol*min/L/day and Fludarabine 40mg/m2/day for 4 days, followed by transplantation of G-CSF mobilized peripheral blood stem cells (PBSC) (N=98) or unstimulated bone marrow (BM) (N=2) from allogeneic donors (MRD 38, MUD 38, MMUD 24). Acute GVHD prophylaxis consisted of tacrolimus/methotrexate (N = 77), tacrolimus/mycophenolate mofetil (N = 22), or tacrolimus/sirolimus (N = 1). Median time to neutrophil and platelet engraftment was 16 and 12 days, respectively. Non-relapse mortality was 3% at 100 days, and 15% by 1 year. The cumulative incidence of relapse was 41%. Overall survival (OS) was 59% (95% CI: 48.1 – 67.5) at 1 year, and 42% (95% CI: 30.8-53.3) at 4 years. OS at 4 years for primary AML in CR1, secondary AML in CR1, CR2, and PIF were 52.9%, 40.1%, 41.2%, and 57.5% respectively; none with relapsed disease survived to 4 years (log-rank p = 0.0014). Progression-free survival (PFS) was 53% (95% CI: 42.8 – 62.2) at 1 year, and 32.3% (95% CI: 21.8 – 43.2) at 4 years. PFS at 4 years for primary AML in CR1, secondary AML in CR1, CR2, and PIF were 44.1%, 33.4%, 33.9%, and 33.1%, respectively, while none with relapsed disease at transplant reached this endpoint (p = 0.0264). On multivariable modeling, remission status at HCT (relapsed disease HR 14.85 (95% CI: 2.12 - 104.2), p = 0.007), moderate/severe cGVHD (HR 0.281, 95% CI: 0.10 - 0.76; p = 0.013), and day 90 bone marrow (BM) chimerism ≥ 90% (HR 0.245, 95% CI: 0.08 - 0.79; p = 0.018) predicted overall survival, and day 90 BM chimerism ≥ 90% (HR of 0.18 (95% CI: 0.08 - 0.45), p = 0.0002) predicted PFS. The following were not significantly related with OS or PFS: age, cytogenetics, donor relation, number of induction cycles, aGVHD prophylaxis regimen, maximum aGVHD grade, WBC at diagnosis, time in first CR, or % BM blasts prior to transplant. Day 90 BM chimerism and cGVHD were significantly related with relapse. Maximum grade of aGVHD predicted non-relapse mortality. These data support the low TRM and efficacy of IV-Bu/Flu in a large series of exclusively AML patients, and demonstrate the impact of day 90 bone marrow chimerism as an important prognostic factor. Further efforts to mitigate relapse risk after HCT are warranted, particularly in those with advanced disease at time of transplant. Disclosures: Off Label Use: IV busulfan and fludarabine for the treatment of acute myeloid leukemia. Alsina:Ortho Biotech: Research Funding, Speakers Bureau; Millenium: Research Funding, Speakers Bureau. Field:PDL BioPharma: Research Funding. Fernandez:Otsuka: Honoraria.

Download Full-text

Characterization of Extramedullary Acute Myeloid Leukemia – Results of the AML96 Trial

Blood ◽

10.1182/blood.v116.21.2154.2154 ◽

2010 ◽

Vol 116 (21) ◽

pp. 2154-2154

Author(s):

Friedrich Stölzel ◽

Christoph Röllig ◽

Michael Kramer ◽

Brigitte Mohr ◽

Uta Oelschlägel ◽

...

Keyword(s):

Bone Marrow ◽

Acute Myeloid Leukemia ◽

Induction Chemotherapy ◽

Myeloid Leukemia ◽

The Body ◽

Hematopoietic Stem ◽

Npm1 Mutation ◽

Mutation Status ◽

The Impact ◽

Acute Myeloid

Abstract Abstract 2154 Background: Myeloid Sarcoma (MS) is defined as an extramedullary mass composed of myeloid blasts occurring at an anatomical site other than the bone marrow. Furthermore, the term extramedullary manifestation (EM) is applied if it accompanies overt acute myeloid leukemia (AML) and represents non-effacing tissue infiltration. EM is reported to correspond often to the skin but can affect almost every site of the body. The prognosis of MS or EM has been discussed controversially in the past. EM at diagnosis of AML is generally thought to be a rare event. However, data defining the prevalence of EM at diagnosis of AML and its prognostic value are missing. The aim of this analysis was to provide data for estimating the prevalence of EM at diagnosis of AML and to determine its relevance by including clinical and laboratory data from patients being treated in the prospective AML96 trial of the Study Alliance Leukemia (SAL) study group. Patients and Methods: A total of 326 patients with AML (age 17 – 83 years) and EM were treated within the AML96 trial with a median follow up of 8.8 years (95% CI, 8.4 to 9.3 years). All patients received double induction chemotherapy. Consolidation therapy contained high-dose cytosine arabinoside and for patients ≤ 60 years of age the option of autologous or allogeneic hematopoietic stem cell transplantation (HSCT). Logistic regression analyses were used to identify prognostic variables for CR rates. The method of Kaplan-Meier was used to estimate OS and EFS. Confidence interval (CI) estimation for the survival curves was based on the cumulative hazard function using the Greenwood's formula for the SE estimation. Survival distributions were compared using the log rank test. Results: 17% of the AML patients entered into the AML96 trial were diagnosed with EM. In 313 of the 326 patients (96%) EM was evident at diagnosis. The majority of patients with EM were diagnosed with de novo AML (84%, n=273), whereas gingival infiltration (51%, n=166) displayed the main EM of AML with CNS involvement being less common (4%, n=14). The majority of patients had a cytogenetic intermediate risk profile (71%, n=221) with a total of 172 patients (56%) harboring a normal karyotype. Patients with EM had a statistically significant lower median CD34-positivity of bone marrow blasts, higher percentage of FAB subtypes M4 and M5, higher WBC counts and LDH at diagnosis and higher percentage of NPM1 mutations compared to those patients without EM (all p<.001). When comparing achievement of CR between patients with EM to patients without EM, no statistical difference between these two groups was observed. Analysis according to the NPM1/FLT3-ITD mutation status revealed highest 5-year-OS (37%, 95% CI: .24 - .508) and 5-year-EFS (36%, 95% CI: .224 - .448) in the NPM1-mut/FLT3-wt group and lowest 5-year-OS (12%, 95% CI: 0 - .261) and 5-year-EFS (4%, 95% CI: 0 - .124) in the NPM1-wt/FLT3-ITD group, p=.007 and p=.001, respectively. Of the 49 relapsed patients with EM who had a NPM1-mutation at diagnosis 48 deceased despite of intensified relapse therapies. Conclusions: This analysis represents the largest study so far investigating the impact of EM AML. Patients with EM AML have distinct differences from AML patients without EM regarding their clinical and molecular characteristics at diagnosis. However these differences do not translate into differences in response to induction chemotherapy. Compared to patients without EM, survival analysis revealed differences according to the NPM1/FLT3-ITD mutation status which is also described for patients without EM AML. However, the prognosis for patients with EM who harbor a mutated NPM1 the prognosis at relapse seems to be dismal. Disclosures: No relevant conflicts of interest to declare.

Download Full-text

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.

Download Full-text

High Expression of Myocyte Enhancer Factor 2C (MEF2C) Is Associated with Adverse Risk Features and Poor Outcome in Pediatric Acute Myeloid Leukemia: A Report from the Children's Oncology Group

Blood ◽

10.1182/blood.v126.23.2570.2570 ◽

2015 ◽

Vol 126 (23) ◽

pp. 2570-2570

Author(s):

George S. Laszlo ◽

Todd A. Alonzo ◽

Chelsea J. Gudgeon ◽

Kimberly H. Harrington ◽

Alex Kentsis ◽

...

Keyword(s):

Bone Marrow ◽

Overall Survival ◽

Acute Myeloid Leukemia ◽

Myeloid Leukemia ◽

Research Funding ◽

Event Free Survival ◽

Free Survival ◽

Expression Levels ◽

Acute Myeloid ◽

Enhancer Factor

Abstract Background: Myocyte enhancer factor 2C (MEF2C) was initially identified as essential transcription factor for cardiac muscle development. However, subsequent studies have indicated that MEF2C plays a much broader biological role, including in the normal hematopoietic system. Recent studies have now identified MEF2C as cooperating oncogene in acute myeloid leukemia (AML) and suggested a contribution to the aggressive nature of at least some subtypes of AML. These findings raised the possibility that MEF2C could serve as marker of poor-risk disease and, therefore, have prognostic significance in AML. To test this hypothesis, we retrospectively quantified MEF2C expression in participants of the AAML0531 trial and correlated expression levels with disease characteristics and clinical outcome. Patients and Methods: AAML0531 (NCT00372593) was a multicenter phase 3 study that determined the addition of gemtuzumab ozogamicin to intensive chemotherapy among 1,022 eligible patients aged <30 yearswith newly diagnosed de novo non-APL AML, excluding those with bone marrow failure syndromes, juvenile myelomonocytic leukemia, or Down syndrome (if ≤3 years of age) between 2006 and 2010. Cryopreserved pretreatment ("diagnostic") specimens from patients enrolled on AAML0531 who consented to the biology studies and had bone marrow samples were available were included in this study. Total RNA from unsorted specimens was extracted, quantified, and subjected to quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR) using TaqMan primers to determine expression of MEF2C and, for normalization, the housekeeping gene, β-glucuronidase (GUSB). Patient samples were run in duplicate, and the ΔΔCT method quantified as 2(-ΔΔCT) was used to determine the expression levels of MEF2C relative to GUSB. Results: In all 751 available patient specimens, MEF2C mRNA was detectable and varied >3,000-fold relative to GUSB (0.0091-29.1272 [median: 0.7978]). Patients with the highest relative MEF2C expression (4th quartile) less likely achieved a complete remission after one course of chemotherapy than the other patients (67% vs. 78%, P=0.005). They also had an inferior overall survival (P=0.014; at 5 years: 55±8% vs. 67±4%), inferior event-free survival (P<0.001; at 5 years: 38±7% vs. 54±4%), and higher relapse risk than patients within the lower 3 quartiles of MEF2C expression (P<0.001; at 5 years: 53±9% vs. 35±5%). Of note, exploratory multiple cutpoint analyses for overall and event-free survival indicated that the most statistically significant results were centered around the Q4 cutpoint region, supporting our approach of comparing patients with the highest quartile of relative MEF2C expression with those having lower relative MEF2C expression. Importantly, MEF2C expression was strongly associated with cytogenetic and molecular abnormalities. Specifically, patients with high MEF2C expression less likely had CBF translocations (inv(16): P=0.007, and t(8;21): P<0.001) or normal karyotype AML (P<0.001); conversely, they were more likely to have leukemia with monosomy 7 (P<0.001) and abnormalities involving 11q23 (P<0.001). Furthermore, patients with high MEF2C less likely had a FLT3/ITD (P =0.018) or a mutation in either NPM1 (P=0.010) or CEBPA (P =0.002). Consistently, patients with high MEF2C expression less likely had low-risk disease (16% vs. 46%, P<0.001) and more likely had standard-risk disease (68% vs. 42%, P <0.001) than those with lower MEF2C expression. Indeed, after adjustment for disease risk, age, FAB category, and treatment arm, high MEF2C expression was no longer statistically significantly associated with inferior overall survival (hazard ratio [HR]=0.99 [95% confidence interval: 0.72-1.36], P=0.929), inferior event-free survival (HR: 1.14 [0.86-1.49], P=0.365), or higher relapse risk (HR: 1.32 [0.91-1.92], P=0.137), suggesting that MEF2C cooperates with additional pathogenic abnormalities. Conclusion: High MEF2C expression identifies a subset of AML patients with adverse-risk disease features and poor outcome. These findings provide the rationale for therapeutic targeting of MEF2C transcriptional activation in AML. Disclosures Walter: AstraZeneca, Inc.: Consultancy; Covagen AG: Consultancy; Seattle Genetics, Inc.: Research Funding; Amgen, Inc.: Research Funding; Pfizer, Inc.: Consultancy; Amphivena Therapeutics, Inc.: Consultancy, Research Funding.

Download Full-text

Stromal CYR61 Confers Resistance to Mitoxantrone Via Spleen Tyrosine Kinase Activation in Human Acute Myeloid Leukemia

Blood ◽

10.1182/blood.v124.21.2228.2228 ◽

2014 ◽

Vol 124 (21) ◽

pp. 2228-2228

Author(s):

Xin Long ◽

Laszlo Perlaky ◽

Tsz-Kwong Chris Man ◽

Michele S. Redell

Keyword(s):

Bone Marrow ◽

Flow Cytometry ◽

Acute Myeloid Leukemia ◽

Cell Lines ◽

Stromal Cells ◽

Myeloid Leukemia ◽

Stromal Cell ◽

Chemotherapy Resistance ◽

Induced Apoptosis ◽

Acute Myeloid

Abstract Acute myeloid leukemia (AML) is a life-threatening bone marrow malignancy with a relapse rate near 50% in children, despite aggressive chemotherapy. Accumulating evidence shows that the bone marrow stromal environment protects a subset of leukemia cells and allows them to survive chemotherapy, eventually leading to recurrence. The factors that contribute to stroma-induced chemotherapy resistance are largely undetermined in AML. Our goal is to delineate the mechanisms underlying stroma-mediated chemotherapy resistance in human AML cells. We used two human bone marrow stromal cell lines, HS-5 and HS-27A, to study stroma-induced chemotherapy resistance. Both stromal cell lines are equally effective in protecting AML cell lines and primary samples from apoptosis induced by chemotherapy agents, including mitoxantrone, etoposide, and cytarabine. By gene expression profiling using the Affymetrix U133Plus 2 platform, we previously found that CYR61 was among the genes that were commonly upregulated in AML cells by both stromal cell lines. CYR61 is a secreted matricellular protein that is expressed at relatively low levels by AML cells, and at higher levels by stromal cells. CYR61 binds and activates integrins and enhances growth factor signaling in AML cells, and it has been associated with chemoresistance in other malignancies. Our current data provide functional evidence for a role for this protein in stroma-mediated chemoresistance in AML. First, we added anti-CYR61 neutralizing immunoglobulin (Ig), or control IgG, to AML-stromal co-cultures, treated with chemotherapy for 24 hours, and measured apoptosis with Annexin V staining and flow cytometry. In THP-1+HS-27A co-cultures treated with 50 nM mitoxantrone, the apoptosis rate was 33.0 ± 3.7% with anti-CYR61 Ig v. 16.3 ± 4.2% with control IgG; p=0.0015). Next, we knocked down CYR61 in the HS-5 and HS-27A stromal cell lines by lentiviral transduction of two individual shRNA constructs, and confirmed knockdown (KD) at the gene and protein levels for both cell lines. These CYR61-KD stromal cells provided significantly less protection for co-cultured AML cells treated with mitoxantrone, compared to stromal cells transduced with the non-silencing control. For example, the apoptosis rate for THP-1 cells co-cultured with CYR61-KD HS-27A cells was 10.8 ± 0.8%, compared to 6.8 ± 1.1% for THP-1 cells co-cultured with control HS-27A cells (p=0.02). Similar results were obtained with NB-4 AML cells. These results demonstrate that CYR61 contributes to stroma-mediated chemoresistance. CYR61 binds to integrin αvβ3 (Kireeva, et al, J. Biol. Chem., 1998, 273:3090), and this integrin activates spleen tyrosine kinase (Syk) (Miller, et al, Cancer Cell, 2013, 24:45). Using intracellular flow cytometry, we found that activated Syk (pSyk) increased in THP-1 and NB-4 cell lines, and in primary AML patient samples, upon exposure to control HS-27A cells. In primary samples, the mean fluorescence intensity (MFI) for pSyk averaged 11.7 ± 1.3 in co-culture v. 6.6 ± 0.6 for cells cultured alone (p=0.004, n=10). In contrast, pSyk did not significantly increase in AML cells co-cultured with CYR61-KD HS-27A cells (MFI for primary patient samples: 8.6 ± 0.8). This result implicates Syk as a downstream signaling mediator of CYR61. To determine the role of CYR61-induced Syk signaling in chemotherapy resistance, we treated AML-stromal cell co-cultures with 3 uM R406, a potent Syk inhibitor, or DMSO, then added 300 nM mitoxantrone, and measured apoptosis after 24 hours. In AML cells co-cultured with control HS-27A cells, mitoxantrone-induced apoptosis was significantly increased by Syk inhibition (THP-1 cells: 13.7 ± 0.7% with R406 v. 10.0 ± 0.3% with DMSO, p<0.05), consistent with reduced chemoresistance. Notably, R406 did not further increase mitoxantrone-induced apoptosis in AML cells co-cultured with CYR61-KD HS-27A stromal cells (THP-1 cells: 15.7 ± 0.2% with R406 v. 16.9 ± 0.4% with DMSO). Similar results were seen with NB-4 cells, as well. These results support the notion that CYR61 signals through the integrin-Syk pathway to protect AML cells from chemotherapy. Therefore, the CYR61 - integrin - Syk pathway may be a potential therapeutic target for overcoming stroma-induced chemotherapy resistance in AML. Disclosures No relevant conflicts of interest to declare.

Download Full-text