Estey EH
Acute myeloid leukemia: 2013 update on risk-stratification and management.
Am J Hematol. 2013; 88(4):318-27 [PubMed]

UNLABELLED: DISEASE OVERVIEW: Acute myeloid leukemia (AML) results from accumulation of abnormal blasts in the marrow. These cells interfere with normal hematopoiesis, can escape into the peripheral blood, and infiltrate CSF and lung. It is likely that many different mutations, epigenetic aberrations, or abnormalities in micro RNA expression can produce the same morphologic disease with these differences responsible for the very variable response to therapy, which is AMLs principal feature.
DIAGNOSIS: This rests on demonstration that the marrow or blood has > 20% blasts of myeloid lineage. Blast lineage is assessed by multiparameter flow cytometry, with CD33 and CD13 being surface markers typically expressed by myeloid blasts. It should be realized that clinical/prognostic considerations, not the blast % per se, should be the main factor determining how a patient is treated. RISK STRATIFICATION: Two features determine risk: the probability of treatment-related mortality (TRM) and, more important, even in patients aged >75 with Zubrod performance status 1, the probability of resistance to standard therapy despite not incurring TRM. The chief predictor of resistance is cytogenetics, with a monosomal karyotype (MK) denoting the disease is essentially incurable with standard therapy even if followed by a standard allogeneic transplant (HCT). The most common cytogentic finding is a normal karyotype(NK) and those of such patients with an NPM1 mutation but no FLT3 internal tandem duplication (ITD), or with a CEBPA mutation, have a prognosis similar to that of patients with the most favorable cytogenetics (inv 16 or t[8;21]) (60-70% cure rate). In contrast, NK patients with a FLT3 ITD have only a 30-40% chance of cure even after HCT. Accordingly analyses of NPM1, FLT3, and CEBPA should be part of routine evaluation, much as is cytogenetics. Risk is best assessed considering several variables simultaneously rather than, for example, only age. Increasing evidence indicates that other mutations and abnormalities in microRNA (miRNA) expression also affect resistance as do post treatment factors, in particular the presence of minimal residual disease. These newer mutations and MRD are discussed in this update. RISK-ADAPTED THERAPY: Patients with inv (16) or t(8;21) or who are NPM1+/FLT3ITD-can receive standard therapy (daunorubicin + cytarabine) and should not receive HCT in first CR. It seems likely that use of a daily daunorubicin dose of 90 mg/m(2) will further improve outcome in these patients. There appears no reason to use doses of cytarabine > 1 g/m(2) (for example bid X 6 days), as opposed to the more commonly used 3 g/m(2) . Patients with an unfavorable karyotype (particularly MK) are unlikely to benefit from standard therapy (even with dose escalation) and are thus prime candidates for clinical trials of new drugs or new approaches to HCT; the latter should be done in first CR. Patients with intermediate prognoses (for example NK and NPM and FLT3ITD negative) should also receive HCT in first CR and can plausibly receive either investigational or standard induction therapy, with the same prognostic information about standard therapy leading one patient to choose the standard and another an investigational option. This update discusses results with newer agents: quizartinib and crenolanib, gemtuzumab ozogamicin, clofarabine and cladribine, azacitidine and decitabine, volasertib, and means to prevent relapse after allogeneic transplant. The diagnosis of AML essentially is made as it was in 2012. Thus this review will emphasize new developments in risk stratification and treatment using as references many papers published in 2012.

Yatsenko Y, Kalennik O, Maschan M, et al.
NPM1, FLT3, and c-KIT mutations in pediatric acute myeloid leukemia in Russian population.
J Pediatr Hematol Oncol. 2013; 35(3):e100-8 [PubMed]

We evaluated frequencies of NPM1, FLT3, c-KIT mutations in childhood acute myeloid leukemia (AML) in Russia and assessed prognostic relevance of the mutations. RNA and DNA were extracted from bone marrow samples of 186 (106 male and 80 female) pediatric patients younger than 17 year with de novo AML. Mutations and chromosomal rearrangements were detected by sequencing of a corresponding gene. NPM1 mutations were found in 5.2%, FLT3 mutations in 12.1%, c-KIT mutations in 3.7% of the patients. NPM1 mutations were associated with the absence of chromosomal aberrations (P=0.007) and FLT3/ITD (P=0.018). New data on incidence of c-KIT mutations in various AML subtypes as well as new variations of c-KIT mutations in the exon 8 are presented. The results are compared to previously published studies on NPM1, FLT3, c-KIT mutations in various populations. No statistically significant differences in survival rates between groups with or without of FLT3, NPM1, c-KIT mutations were found (P>0.05). Meanwhile, 4-year overall survival rates were higher in patients having NPM1 mutations comparing with NPM1/WT patients (100% vs. 50%) and in patients having FLT3 mutations comparing with FLT3/WT patients (70% vs. 50%). The data presented contribute to knowledge on incidence and prognostic significance of the mutations in pediatric AML.

Powell BL
Acute promyelocytic leukemia: progress far and wide.
Blood. 2013; 121(11):1925-6 [PubMed]

In this issue of Blood, Rego and colleagues describe the exciting accomplishments of the International Consortium on Acute Promyelocytic Leukemia (IC-APL), an initiative of the International Members Committee of the American Society of Hematology (ASH).(1) The purpose of this initiative is to create a network of institutions in developing countries that will work in partnership with cooperative groups in the United States and Europe in order to close the gap in quality of care and outcomes in acute promyelocytic leukemia (APL) between developed and developing countries.

Styczynski J, Piatkowska M, Czyzewski K, et al.
Individual tumor response testing in multiple relapsed acute myeloid leukemia in children.
Anticancer Res. 2013; 33(3):1189-93 [PubMed]

AIM: The analysis of the individualized tumor response testing (ITRT) at first and subsequent relapse in children with acute myeloid leukemia (AML).
PATIENTS AND METHODS: A total of 76 pediatric AML samples underwent ITRT for up to 21 drugs.
RESULTS: No significant differences between ITRT at first and subsequent relapse were found, and no drug was found, for which significantly higher resistance of myeloblasts was observed at subsequent relapse, when compared to first relapse of AML. For most tested drugs, patients with relapse had higher IRTR than those with de novo AML. The median relative resistance value between patients with relapse and those with de novo diagnosis for all 21 drugs tested was 1.6. Samples of relapsed AML samples were significantly more resistant to: Idarubicin (1.8-fold), etoposide (5.9-fold), cytarabine (1.7-fold), fludarabine (3.7-fold) and busulfan (4.3-fold).
CONCLUSION: ITRT in relapsed AML is higher in comparison to that at initial diagnosis, while no differences in ITRT between first and subsequent relapse of AML were found.

Cribe AS, Steenhof M, Marcher CW, et al.
Extramedullary disease in patients with acute myeloid leukemia assessed by 18F-FDG PET.
Eur J Haematol. 2013; 90(4):273-8 [PubMed]

BACKGROUND: Prevalence of extramedullary disease (EMD) in acute myeloid leukemia (AML) at the time of diagnosis is unknown. Previous estimates range from 2.5% to 30.5% and are usually based on clinical examination. This may cause an under diagnosis of EMD as not all extramedullary manifestations are easily detectable. Few recent studies have used positron emission tomography (PET) scans for diagnosing EMD in patients AML.
METHOD: During a 9-month period, newly diagnosed patients with AML who were candidates for intensive chemotherapy were 18F-Fluoro-deoxy-glucose (FDG) PET-scanned prior to induction treatment. We compared the prevalence of EMD diagnosed by PET scans and by clinical examination. Subsequent PET scans following induction chemotherapy were performed for response evaluation of EMD.
RESULTS: Twenty-six patients were included in the study. 18-F-FDG PET scans revealed more than twice as many patients with EMD than found by clinical examination (65% vs. 31%). PET demonstrated 55 EMD lesions compared with 15 diagnosed by clinical examination. In general, the responses of EMD detected by PET scans were concordant with the bone marrow responses assessed by pathology examination.
CONCLUSION: 18-F-FDG PET is a useful tool for diagnosing EMD in AML and for assessing treatment responses of EMD in AML.

Chen L, Han F, Qu H, et al.
Combination therapy with 5-amino-4-imidazolecarboxamide riboside and arsenic trioxide in acute myeloid leukemia cells involving AMPK/TSC2/mTOR pathway.
Pharmazie. 2013; 68(2):117-23 [PubMed]

The aim of this study was to demonstrate the effects of the AMP-activated protein kinase (AMPK) activator 5-amino-4-imidazolecarboxamide riboside (AICAR) in combination with arsenic trioxide (ATO) in acute myeloid leukemia cells and determine its mechanism of action. Cell lines were either exposed to each drug alone or both the drugs simultaneously. Cell proliferation, cell cycle and apoptosis were assessed. Combination index (CI) method was used to calculate the synergistic, additive, or antagonistic effects of these drugs. Western blot technique was used to study the signaling molecules in the AMPK/TSC2/mTOR pathway. Simultaneous exposure of HL-60 cells to AICAR and ATO indicated a synergism (CI < 1), whereas CI on NB4 cells was greater than 1. In HL-60, the change in expression level of each protein was quite significant in the presence of the combination as compared to that induced through any single agent. On the contrary, ATO weakened the effect of AICAR-mediated AMPK activation in NB4 cells. ATO caused a profound decrease in the protein level of PML/RARalpha in NB4 cells after 48 h, but there was no change with AICAR and the combination. The combination of AICAR and ATO produced a synergistic effect in the treatment of HL-60 cells involving AMPK/TSC2/mTOR pathway, and AICAR reduced ATO-mediated apoptotic death on acute promyelocytic leukemia NB4 cells.

Boudry-Labis E, Roche-Lestienne C, Nibourel O, et al.
Neurofibromatosis-1 gene deletions and mutations in de novo adult acute myeloid leukemia.
Am J Hematol. 2013; 88(4):306-11 [PubMed]

Germline heterozygous alterations of the tumor-suppressor gene neurofibromatosis-1 (NF1) lead to neurofibromatosis type 1, a genetic disorder characterized by a higher risk to develop juvenile myelomonocytic leukemia and/or acute myeloid leukemia (AML). More recently, somatic 17q11 deletions encompassing NF1 have been described in many adult myeloid malignancies. In this context, we aimed to define NF1 involvement in AML. We screened a total of 488 previously untreated de novo AML patients for the NF1 deletion using either array comparative genomic hybridization (aCGH) or real-time quantitative PCR/fluorescence in situ hybridization approaches. We also applied massively parallel sequencing for in depth mutation analysis of NF1 in 20 patients including five NF1-deleted patients. We defined a small ∼0.3 Mb minimal deleted region involving NF1 by aCGH and an overall frequency of NF1 deletion of 3.5% (17/485). NF1 deletion is significantly associated with unfavorable cytogenetics and with monosomal karyotype notably. We discovered six NF1 variants of unknown significance in 7/20 patients of which only one out of four disappeared in corresponding complete remission sample. In addition, only one out of five NF1-deleted patients has an acquired coding mutation in the remaining allele. In conclusion, direct NF1 inactivation is infrequent in de novo AML and may be a secondary event probably involved in leukemic progression.

Barreto JN, Beach CL, Wolf RC, et al.
The incidence of invasive fungal infections in neutropenic patients with acute leukemia and myelodysplastic syndromes receiving primary antifungal prophylaxis with voriconazole.
Am J Hematol. 2013; 88(4):283-8 [PubMed]

The objective of this study is to characterize the outcomes of primary antifungal prophylaxis with voriconazole in patients receiving intensive chemotherapy for acute myelogenous leukemia (AML) or myelodysplastic syndromes (MDS). We conducted a single center, retrospective, cohort study of consecutive adult patients with AML or MDS at Mayo Clinic between January 1, 2006 and July 1, 2010. The study included patients undergoing induction or first relapse combination chemotherapy who received voriconazole 200 mg orally twice daily as prophylaxis during the neutropenic phase. Patient records were evaluated until 30 days after neutrophil recovery for development of invasive fungal infection (IFI) as defined per EORTC/MSG 2008 criteria with computed tomography scans independently reviewed by a radiologist. Therapeutic drug monitoring and reasons for voriconazole discontinuation were documented. Twenty four episodes of IFI were detected among 165 consecutive patients for an overall incidence of 145 per 1000 patients. The incidence of IFI was 24, 42, and 78 per 1000 patients for proven, probable, and possible infection, respectively. Four patients developed proven IFI (n = 2 Aspergillus spp., n = 2 Rhizopus spp.). Serum voriconazole trough concentrations were available in 39 patients, and no statistically significant difference in voriconazole trough level was observed between those with versus without an IFI. Voriconazole prophylaxis was discontinued in 81 patients due to suspected IFI (n = 24), fever of unknown origin (n = 19), adverse events (n = 23), and other causes (n = 17). Voriconazole as primary IFI prophylaxis is safe and may be beneficial in AML/MDS patients receiving intensive chemotherapy.

Suarez L, Gore SD
Demethylation demystification.
Blood. 2013; 121(9):1488-9 [PubMed]

The ability of the DNA methyltransferase inhibitors (DNMTi) to induce terminal differentiation in fibroblasts was first noted by Taylor and Jones in 1979; Silverman and Holland reported hematologic improvement in patients with myelodysplastic syndrome (MDS) in 1993. That azacitidine improves survival in patients with high-risk MDS and acute myeloid leukemia with MDS features compared with a combined comparator group of supportive care, low-dose cytarabine, and intensive cytarabine plus anthracycline, while inducing trilineage normalization in approximately 15% of patients makes the development of more potent, more specific drugs that behave like azacitidine imperative. The question is, how do the azanucleosides behave?

Wang SA, Hutchinson L, Tang G, et al.
Systemic mastocytosis with associated clonal hematological non-mast cell lineage disease: clinical significance and comparison of chomosomal abnormalities in SM and AHNMD components.
Am J Hematol. 2013; 88(3):219-24 [PubMed]

Some patients with systemic mastocytosis have concurrent hematological neoplasms, designated in the World Health Organization (WHO) classification as systemic mastocytosis with associated clonal hematological non-mast cell lineage disease (SM-AHNMD). In this study, we analyzed 29 patients with SM-AHNMD and compared them to 40 patients with pure SM. The AHNMDs were classified as chronic myelomonocytic leukemia (CMML) (n = 10), myelodysplastic syndrome (MDS) (n = 7), myeloproliferative neoplasms (n = 4), B-cell lymphoma/leukemia/plasma cell neoplasms (n = 7), and acute myeloid leukemia (n = 1). Patients with SM-AHNMD were older, more frequently had constitutional symptoms and hematological abnormalities, less often had skin lesions, and had an inferior overall survival compared with pure SM patients (48 months vs. not-reached, P < 0.001). Karyotypic abnormalities were detected in 9/28 (32%) patients with SM-AHNMD but not in pure SM patients (P < 0.001). Combined imaging/ fluorescence-in-situ hybridization performed in four SM-AHNMD cases revealed shared abnormal signals in mast cells and myeloid cells in two patients with SM-CMML and one patient with SM-MDS, but not in the mast cells of a case SM-associated with chronic lymphocytic leukemia with ATM-deletion. Quantitative mutation analysis showed higher levels of mutant KIT D816V in SM-CMML and SM-MDS than in pure SM (P < 0.001). Our data indicate that the SM-AHNMD category in the WHO classification is heterogeneous, including clonally related and unrelated forms of AHNMD. The presentation, treatment, and outcome of patients with SM-AHNMD is often dictated by the type of AHNMD.

Rokudai S, Laptenko O, Arnal SM, et al.
MOZ increases p53 acetylation and premature senescence through its complex formation with PML.
Proc Natl Acad Sci U S A. 2013; 110(10):3895-900 [PubMed] Article available free on PMC after 05/09/2013

Monocytic leukemia zinc finger (MOZ)/KAT6A is a MOZ, Ybf2/Sas3, Sas2, Tip60 (MYST)-type histone acetyltransferase that functions as a coactivator for acute myeloid leukemia 1 protein (AML1)- and Ets family transcription factor PU.1-dependent transcription. We previously reported that MOZ directly interacts with p53 and is essential for p53-dependent selective regulation of p21 expression. We show here that MOZ is an acetyltransferase of p53 at K120 and K382 and colocalizes with p53 in promyelocytic leukemia (PML) nuclear bodies following cellular stress. The MOZ-PML-p53 interaction enhances MOZ-mediated acetylation of p53, and this ternary complex enhances p53-dependent p21 expression. Moreover, we identified an Akt/protein kinase B recognition sequence in the PML-binding domain of MOZ protein. Akt-mediated phosphorylation of MOZ at T369 has a negative effect on complex formation between PML and MOZ. As a result of PML-mediated suppression of Akt, the increased PML-MOZ interaction enhances p21 expression and induces p53-dependent premature senescence upon forced PML expression. Our research demonstrates that MOZ controls p53 acetylation and transcriptional activity via association with PML.

Hao L, Zhao J, Wang X, et al.
Hepatotoxicity from arsenic trioxide for pediatric acute promyelocytic leukemia.
J Pediatr Hematol Oncol. 2013; 35(2):e67-70 [PubMed]

The aim of this study was to investigate the hepatotoxicity induced by arsenic trioxide (As2O3) at a therapeutic dose for pediatric acute promyelocytic leukemia (APL). A total of APL patients received As2O3 treatment by IV drip. Hepatotoxicity was monitored based on the observations of the dynamic changes in liver function and treatment responses. The influencing factors of hepatotoxicity were further analyzed. Liver impairment occurred in 24.4% of the patients, most of which was mild and moderate in severity. Liver impairment was primarily manifested by increases in alanine aminotransferase, aspertate aminotransferase, and γ-glutamyl transferase, and these increases mostly occurred within 1 to 3 weeks and then returned to normal levels after 4 weeks. Patients' ages, sex, disease time, hepatomegaly and liver dysfunction, and disseminated intravascular coagulation did not show correlations with hepatotoxicity. Their hemogram and lactate dehydrogenase numerical values obtained from preliminary diagnosis did not show significant correlations with hepatotoxicity. Aggravated hepatotoxicity was not observed in patients receiving marcellomycin for the sake of complete remission. Changes in short-term cumulative dose of As2O3 did not exhibit a correlation with hepatotoxicity. However, patients suffering from differentiation syndrome were more likely at the risk of hepatotoxicity. Liver impairment improved after the suspension of As2O3 and liver protection treatment. No patient died of liver failure. Hepatotoxicity induced by As2O3 at a therapeutic dose for pediatric APL is mild and temporary. The first to the third week of the remission induction is the important period for monitoring. Great attention should be given to differentiation syndrome as it may worsen hepatotoxicity.

Molina B, Lassaletta A, Gonzalez-Vicent M, et al.
Very late isolated CNS relapse of acute myeloid leukemia.
J Pediatr Hematol Oncol. 2013; 35(2):e57-9 [PubMed]

Isolated central nervous system (CNS) relapse in acute myeloid leukemia (AML) rarely occurs later than 2 years after remission. We present a child diagnosed with AML (FAB M5) without CNS involvement at diagnosis who was treated with chemotherapy and consolidated with autologous hematopoietic stem cell transplantation. He was in complete remission for >6 years until he had an isolated CNS relapse. He was treated with only intrathecal chemotherapy and achieved a second complete remission, but relapsed in the bone marrow 5 months after the CNS relapse. Treatment of late isolated CNS relapse of AML is discussed.

Wang E, Kawaoka S, Yu M, et al.
Histone H2B ubiquitin ligase RNF20 is required for MLL-rearranged leukemia.
Proc Natl Acad Sci U S A. 2013; 110(10):3901-6 [PubMed] Article available free on PMC after 05/09/2013

Mixed-lineage leukemia (MLL) fusions are potent oncogenes that initiate aggressive forms of acute leukemia. As aberrant transcriptional regulators, MLL-fusion proteins alter gene expression in hematopoietic cells through interactions with the histone H3 lysine 79 (H3K79) methyltransferase DOT1L. Notably, interference with MLL-fusion cofactors like DOT1L is an emerging therapeutic strategy in this disease. Here, we identify the histone H2B E3 ubiquitin ligase ring finger protein 20 (RNF20) as an additional chromatin regulator that is necessary for MLL-fusion-mediated leukemogenesis. Suppressing the expression of Rnf20 in diverse models of MLL-rearranged leukemia leads to inhibition of cell proliferation, under tissue culture conditions as well as in vivo. Rnf20 knockdown leads to reduced expression of MLL-fusion target genes, effects resembling Dot1l inhibition. Using ChIP-seq, we found that H2B ubiquitination is enriched in the body of MLL-fusion target genes, correlating with sites of H3K79 methylation and transcription elongation. Furthermore, Rnf20 is required to maintain local levels of H3K79 methylation by Dot1l at Hoxa9 and Meis1. These findings support a model whereby cotranscriptional recruitment of Rnf20 at MLL-fusion target genes leads to amplification of Dot1l-mediated H3K79 methylation, thereby rendering leukemia cells dependent on Rnf20 to maintain their oncogenic transcriptional program.

Ferrara F, Schiffer CA
Acute myeloid leukaemia in adults.
Lancet. 2013; 381(9865):484-95 [PubMed]

The outlook for patients with acute myeloid leukaemia has improved in the past 30 years. Unlike other cancers, much of this progress is attributable to refinement of supportive treatment, rather than the introduction of new drugs. New antibacterial and antifungal agents, antiemetics, and improved transfusion support have decreased the rate of early death, and morbidity and mortality from allogeneic stem cell transplantation has been substantially reduced. However, more than half of young adult patients and about 90% of older patients still die from their disease. Refractoriness to initial induction treatment and, more frequently, relapse after complete remission, are still the main obstacles to cure. Accordingly, new treatment approaches with mechanisms of action different from those of conventional chemotherapy are needed. Our knowledge of the various chromosomal and molecular abnormalities implicated in the pathogenesis of the many subtypes of the disease has greatly expanded; as a result, clinical research is moving towards the investigation of new non-cytotoxic agents in combination with chemotherapy. The goal is to target the molecular abnormalities identified at diagnosis; however, several aberrations can coexist in subclones of acute myeloid leukaemia, making the disease less likely to be inhibited by a single agent.

De Braekeleer E, Douet-Guilbert N, Le Bris MJ, et al.
Double Inv(3)(q21q26), a rare but recurrent chromosomal abnormality in myeloid hemopathies.
Anticancer Res. 2013; 33(2):639-42 [PubMed]

Inv(3)(q21q26)/t(3;3)(q21;q26) is a feature of a distinctive entity of acute myeloid leukemia (AML) associated with normal or elevated platelet count, atypical megakaryocytes and multilineage dysplasia in the bone marrow, as well as minimal to no response to chemotherapy and poor clinical outcome. The presence of an inversion on both chromosome 3s is a rare event, as only eight cases have been reported in the literature. Recently, we identified two patients with AML carrying a double inv(3)(q21q26). Using librairies of bacterial artificial chromosome clones mapping to bands 3q21 and 3q26, we found that the regions in which the breakpoints occurred were different in both patients, but located in the same restricted areas in each patient. Although it cannot be excluded that inversion occurred independently on both chromosome 3s, it is more likely that the presence of a double inv(3) is the result of loss of the normal chromosome 3 followed by a duplication of the inverted chromosome, or segmental loss of heterozygosity followed by a somatic repair mechanism.

Li Z, Herold T, He C, et al.
Identification of a 24-gene prognostic signature that improves the European LeukemiaNet risk classification of acute myeloid leukemia: an international collaborative study.
J Clin Oncol. 2013; 31(9):1172-81 [PubMed] Article available free on PMC after 20/03/2014

PURPOSE: To identify a robust prognostic gene expression signature as an independent predictor of survival of patients with acute myeloid leukemia (AML) and use it to improve established risk classification.
PATIENTS AND METHODS: Four independent sets totaling 499 patients with AML carrying various cytogenetic and molecular abnormalities were used as training sets. Two independent patient sets composed of 825 patients were used as validation sets. Notably, patients from different sets were treated with different protocols, and their gene expression profiles were derived using different microarray platforms. Cox regression and Kaplan-Meier methods were used for survival analyses.
RESULTS: A prognostic signature composed of 24 genes was derived from a meta-analysis of Cox regression values of each gene across the four training sets. In multivariable models, a higher sum value of the 24-gene signature was an independent predictor of shorter overall (OS) and event-free survival (EFS) in both training and validation sets (P < .01). Moreover, this signature could substantially improve the European LeukemiaNet (ELN) risk classification of AML, and patients in three new risk groups classified by the integrated risk classification showed significantly (P < .001) distinct OS and EFS.
CONCLUSION: Despite different treatment protocols applied to patients and use of different microarray platforms for expression profiling, a common prognostic gene signature was identified as an independent predictor of survival of patients with AML. The integrated risk classification incorporating this gene signature provides a better framework for risk stratification and outcome prediction than the ELN classification.

Jiao B, Ren ZH, Liu P, et al.
8-CPT-cAMP/all-trans retinoic acid targets t(11;17) acute promyelocytic leukemia through enhanced cell differentiation and PLZF/RARα degradation.
Proc Natl Acad Sci U S A. 2013; 110(9):3495-500 [PubMed] Article available free on PMC after 26/08/2013

The refractoriness of acute promyelocytic leukemia (APL) with t(11;17)(q23;q21) to all-trans retinoic acid (ATRA)-based therapy concerns clinicians and intrigues basic researchers. By using a murine leukemic model carrying both promyelocytic leukemia zinc finger/retinoic acid receptor-α (PLZF/RARα) and RARα/PLZF fusion genes, we discovered that 8-chlorophenylthio adenosine-3', 5'-cyclic monophosphate (8-CPT-cAMP) enhances cellular differentiation and improves gene trans-activation by ATRA in leukemic blasts. Mechanistically, in combination with ATRA, 8-CPT-cAMP activates PKA, causing phosphorylation of PLZF/RARα at Ser765 and resulting in increased dissociation of the silencing mediator for retinoic acid and thyroid hormone receptors/nuclear receptor corepressor from PLZF/RARα. This process results in changes of local chromatin and transcriptional reactivation of the retinoic acid pathway in leukemic cells. Meanwhile, 8-CPT-cAMP also potentiated ATRA-induced degradation of PLZF/RARα through its Ser765 phosphorylation. In vivo treatment of the t(11;17) APL mouse model demonstrated that 8-CPT-cAMP could significantly improve the therapeutic effect of ATRA by targeting a leukemia-initiating cell activity. This combined therapy, which induces enhanced differentiation and oncoprotein degradation, may benefit t(11;17) APL patients.

Lobry C, Ntziachristos P, Ndiaye-Lobry D, et al.
Notch pathway activation targets AML-initiating cell homeostasis and differentiation.
J Exp Med. 2013; 210(2):301-19 [PubMed] Article available free on PMC after 11/08/2013

Notch signaling pathway activation is known to contribute to the pathogenesis of a spectrum of human malignancies, including T cell leukemia. However, recent studies have implicated the Notch pathway as a tumor suppressor in myeloproliferative neoplasms and several solid tumors. Here we report a novel tumor suppressor role for Notch signaling in acute myeloid leukemia (AML) and demonstrate that Notch pathway activation could represent a therapeutic strategy in this disease. We show that Notch signaling is silenced in human AML samples, as well as in AML-initiating cells in an animal model of the disease. In vivo activation of Notch signaling using genetic Notch gain of function models or in vitro using synthetic Notch ligand induces rapid cell cycle arrest, differentiation, and apoptosis of AML-initiating cells. Moreover, we demonstrate that Notch inactivation cooperates in vivo with loss of the myeloid tumor suppressor Tet2 to induce AML-like disease. These data demonstrate a novel tumor suppressor role for Notch signaling in AML and elucidate the potential therapeutic use of Notch receptor agonists in the treatment of this devastating leukemia.

Kannan S, Sutphin RM, Hall MG, et al.
Notch activation inhibits AML growth and survival: a potential therapeutic approach.
J Exp Med. 2013; 210(2):321-37 [PubMed] Article available free on PMC after 11/08/2013

Although aberrant Notch activation contributes to leukemogenesis in T cells, its role in acute myelogenous leukemia (AML) remains unclear. Here, we report that human AML samples have robust expression of Notch receptors; however, Notch receptor activation and expression of downstream Notch targets are remarkably low, suggesting that Notch is present but not constitutively activated in human AML. The functional role of these Notch receptors in AML is not known. Induced activation through any of the Notch receptors (Notch1-4), or through the Notch target Hairy/Enhancer of Split 1 (HES1), consistently leads to AML growth arrest and caspase-dependent apoptosis, which are associated with B cell lymphoma 2 (BCL2) loss and enhanced p53/p21 expression. These effects were dependent on the HES1 repressor domain and were rescued through reexpression of BCL2. Importantly, activated Notch1, Notch2, and HES1 all led to inhibited AML growth in vivo, and Notch inhibition via dnMAML enhanced proliferation in vivo, thus revealing the physiological inhibition of AML growth in vivo in response to Notch signaling. As a novel therapeutic approach, we used a Notch agonist peptide that led to significant apoptosis in AML patient samples. In conclusion, we report consistent Notch-mediated growth arrest and apoptosis in human AML, and propose the development of Notch agonists as a potential therapeutic approach in AML.

Ghezali L, Leger DY, Limami Y, et al.
Cyclopamine and jervine induce COX-2 overexpression in human erythroleukemia cells but only cyclopamine has a pro-apoptotic effect.
Exp Cell Res. 2013; 319(7):1043-53 [PubMed]

Erythroleukemia is generally associated with a very poor response and survival to current available therapeutic agents. Cyclooxygenase-2 (COX-2) has been described to play a crucial role in the proliferation and differentiation of leukemia cells, this enzyme seems to play an important role in chemoresistance in different cancer types. Previously, we demonstrated that diosgenin, a plant steroid, induced apoptosis in HEL cells with concomitant COX-2 overexpression. In this study, we investigated the antiproliferative and apoptotic effects of cyclopamine and jervine, two steroidal alkaloids with similar structures, on HEL and TF1a human erythroleukemia cell lines and, for the first time, their effect on COX-2 expression. Cyclopamine, but not jervine, inhibited cell proliferation and induced apoptosis in these cells. Both compounds induced COX-2 overexpression which was responsible for apoptosis resistance. In jervine-treated cells, COX-2 overexpression was NF-κB dependent. Inhibition of NF-κB reduced COX-2 overexpression and induced apoptosis. In addition, cyclopamine induced apoptosis and COX-2 overexpression via PKC activation. Inhibition of the PKC pathway reduced both apoptosis and COX-2 overexpression in both cell lines. Furthermore, we demonstrated that the p38/COX-2 pathway was involved in resistance to cyclopamine-induced apoptosis since p38 inhibition reduced COX-2 overexpression and increased apoptosis in both cell lines.

Wunderlich M, Mizukawa B, Chou FS, et al.
AML cells are differentially sensitive to chemotherapy treatment in a human xenograft model.
Blood. 2013; 121(12):e90-7 [PubMed] Article available free on PMC after 21/03/2014

As acute myeloid leukemia (AML) xenograft models improve, the potential for using them to evaluate novel therapeutic strategies becomes more appealing. Currently, there is little information on using standard chemotherapy regimens in AML xenografts. Here we have characterized the immunodeficient mouse response to combined Ara-C (cytarabine) and doxorubicin treatment. We observed significant toxicity associated with doxorubicin that required optimization of the route of injection as well as the maximum-tolerated dose for immunodeficient strains. Mice treated with an optimized 5-day induction protocol showed transient weight loss, short-term reduction of peripheral blood cell and platelet counts, and slight anemia. Considerable cytotoxicity was observed in the bone marrow (BM), with primitive LSK cells having a significant survival advantage relative to more mature cells, consistent with the idea of chemotherapy targeting actively growing cells. Treated leukemic mice demonstrated reduced disease burden and increased survival, demonstrating efficacy. AML cells showed significantly increased sensitivity to doxorubicin-containing therapy compared with murine BM cells. Although early treatment could result in some cures, mice with significant leukemia grafts were not cured by using induction therapy alone. Overall, the data show that this model system is useful for the evaluation of novel chemotherapies in combination with standard induction therapy.

Merkel D, Filanovsky K, Gafter-Gvili A, et al.
Predicting infections in high-risk patients with myelodysplastic syndrome/acute myeloid leukemia treated with azacitidine: a retrospective multicenter study.
Am J Hematol. 2013; 88(2):130-4 [PubMed]

Hypomethylating agents have become the standard therapy for patients with high-risk myelodysplastic syndrome (MDS). In Israel, azacitidine (AZA) is routinely used. Yet, infectious complications are common during AZA therapy. The current study was aimed to evaluate the incidence and predisposing risk factors for infections in AZA-treated patients. This retrospective study included patients treated with AZA in 18 Israeli medical institutions between 2008 and 2011. Data on 184 patients [157 high-risk MDS and 27 acute myeloid leukemia (AML)], with a median age of 71.6 (range 29-92) were recorded. Overall, 153 infectious events were reported during 928 treatment cycles (16.5%) administered to 100 patients. One hundred fourteen, 114/153 (75%) events required hospitalization and 30 (19.6%) were fatal. In a univariate analysis, unfavorable cytogenetics, low neutrophil, hemoglobin (Hb) and platelet (PLT) counts were found to be associated with infections (24.4% vs. 12.9%, P < 0.0001; 27% vs. 13.5%, P < 0.0001; 20.4% vs. 11%, P < 0.0001 and 29.2% vs. 14.2%, P < 0.0001, respectively). In multivariate analysis, only low Hb level, low PLT count, and unfavorable cytogenetics remained significant. Prior to therapy, poor cytogenetics, PLT count below 20 × 10⁹/L and neutrophil count below 0.5 × 10⁹/L were predictive of the risk of infection during the first two cycles of therapy. In conclusion, patients with unfavorable cytogenetics, presenting with low neutrophil and PLT counts, are susceptible to infections. Evaluation of infection risk should be repeated prior to each cycle. Patients with poor cytogenetics in whom AZA is prescribed despite low PLT count are particularly at high risk for infections and infection prophylaxis may be considered.

Emerenciano M, Kowarz E, Karl K, et al.
Functional analysis of the two reciprocal fusion genes MLL-NEBL and NEBL-MLL reveal their oncogenic potential.
Cancer Lett. 2013; 332(1):30-4 [PubMed]

MLL gene aberrations are frequently diagnosed in infant acute myeloid leukemia (AML). We previously described the MLL-NEBL and NEBL-MLL genomic fusions in an infant AML patient with a chromosomal translocation t(10;11)(p12;q23). NEBL was the second Nebulin family member (LASP1, NEBL) which was found to be involved in MLL rearrangements. Here, we report on our attempts to unravel the oncogenic properties of both fusion genes. First, RT-PCR analyses revealed the presence of the MLL-NEBL and NEBL-MLL mRNAs in the diagnostic sample of the patient. Next, expression cassettes for MLL-NEBL and NEBL-MLL were cloned into a sleeping beauty vector backbone. After stable transfection, the biological effects of MLL-NEBL, NEBL-MLL or the combination of both fusion proteins were investigated in a conditional cell culture model. NEBL-MLL but also co-transfected cells displayed significantly higher growth rates according to the data obtained by cell proliferation assay. The focus formation experiments revealed differences in the shape and number of colonies when comparing MLL-NEBL, NEBL-MLL- and co-transfected cells. The results obtained in this study suggest that the reciprocal fusion genes of the Nebulin gene family might be of biological importance.

Diffner E, Beck D, Gudgin E, et al.
Activity of a heptad of transcription factors is associated with stem cell programs and clinical outcome in acute myeloid leukemia.
Blood. 2013; 121(12):2289-300 [PubMed]

Aberrant transcriptional programs in combination with abnormal proliferative signaling drive leukemic transformation. These programs operate in normal hematopoiesis where they are involved in hematopoietic stem cell (HSC) proliferation and maintenance. Ets Related Gene (ERG) is a component of normal and leukemic stem cell signatures and high ERG expression is a risk factor for poor prognosis in acute myeloid leukemia (AML). However, mechanisms that underlie ERG expression in AML and how its expression relates to leukemic stemness are unknown. We report that ERG expression in AML is associated with activity of the ERG promoters and +85 stem cell enhancer and a heptad of transcription factors that combinatorially regulate genes in HSCs. Gene expression signatures derived from ERG promoter-stem cell enhancer and heptad activity are associated with clinical outcome when ERG expression alone fails. We also show that the heptad signature is associated with AMLs that lack somatic mutations in NPM1 and confers an adverse prognosis when associated with FLT3 mutations. Taken together, these results suggest that transcriptional regulators cooperate to establish or maintain primitive stem cell-like signatures in leukemic cells and that the underlying pattern of somatic mutations contributes to the development of these signatures and modulate their influence on clinical outcome.

Jourdan E, Boissel N, Chevret S, et al.
Prospective evaluation of gene mutations and minimal residual disease in patients with core binding factor acute myeloid leukemia.
Blood. 2013; 121(12):2213-23 [PubMed]

Not all patients with core binding factor acute myeloid leukemia (CBF-AML) display a good outcome. Modern risk factors include KIT and/or FLT3 gene mutations and minimal residual disease (MRD) levels, but their respective values have never been prospectively assessed. A total of 198 CBF-AML patients were randomized between a reinforced and a standard induction course, followed by 3 high-dose cytarabine consolidation courses. MRD levels were monitored prospectively. Gene mutations were screened at diagnosis. Despite a more rapid MRD decrease after reinforced induction, induction arm did not influence relapse-free survival (RFS) (64% in both arms; P = .91). Higher WBC, KIT, and/or FLT3-ITD/TKD gene mutations, and a less than 3-log MRD reduction after first consolidation, were associated with a higher specific hazard of relapse, but MRD remained the sole prognostic factor in multivariate analysis. At 36 months, cumulative incidence of relapse and RFS were 22% vs 54% (P < .001) and 73% vs 44% (P < .001) in patients who achieved 3-log MRD reduction vs the others. These results suggest that MRD, rather than gene mutations, should be used for future treatment stratifications in CBF-AML patients. This trial was registered at EudraCT as #2006-005163-26 and at www.clinicaltrials.gov as #NCT 00428558.

Park IK, Mishra A, Chandler J, et al.
Inhibition of the receptor tyrosine kinase Axl impedes activation of the FLT3 internal tandem duplication in human acute myeloid leukemia: implications for Axl as a potential therapeutic target.
Blood. 2013; 121(11):2064-73 [PubMed] Article available free on PMC after 14/03/2014

Approximately 20% to 25% of patients with acute myeloid leukemia (AML) have a constitutively activated FLT3-internal tandem duplication (FLT3-ITD), and these patients exhibit a poor prognosis. Here, we report that Axl, a receptor tyrosine kinase (RTK) overexpressed and constitutively active in human AML, targets the RTK FLT3 in FLT3-ITD(+) AML. Abrogation of Axl activation by soluble Axl chimeric protein (Axl-Fc) or small interfering RNA (siRNA) diminishes constitutive FLT3 phosphorylation in FLT3-ITD(+) AML. In addition, inhibition of Axl activation by Axl-Fc interferes with the physical interaction between Axl and FLT3. We found that Axl-Fc, a pharmacologic Axl inhibitor, or siRNA targeting Axl inhibits cell growth, induces cell-cycle arrest and apoptosis, and relieves a block in myeloid differentiation of FLT3-ITD(+) AML in vitro. Axl-Fc also suppresses the growth of human FLT3-ITD(+) AML in vivo. Collectively, our data suggest that Axl contributes to the pathogenesis of FLT3-ITD(+) AML through, at least in part, positive regulation of constitutive FLT3 activation. This also suggests that Axl should be pursued as a potential target for the treatment of FLT3-ITD(+) AML.

Kaspers GJ, Zimmermann M, Reinhardt D, et al.
Improved outcome in pediatric relapsed acute myeloid leukemia: results of a randomized trial on liposomal daunorubicin by the International BFM Study Group.
J Clin Oncol. 2013; 31(5):599-607 [PubMed]

PURPOSE: In pediatric relapsed acute myeloid leukemia (AML), optimal reinduction therapy is unknown. Studies suggest that liposomal daunorubicin (DNX; DaunoXome; Galen, Craigavon, United Kingdom) is effective and less cardiotoxic, which is important in this setting. These considerations led to a randomized phase III study by the International Berlin-Frankfurt-Münster Study Group.
PATIENTS AND METHODS: Patients with relapsed or primary refractory non-French-American-British type M3 AML who were younger than 21 years of age were eligible. Patients were randomly assigned to fludarabine, cytarabine, and granulocyte colony-stimulating factor (FLAG) or to FLAG plus DNX in the first reinduction course. The primary end point was status of the bone marrow (BM) sampled shortly before the second course of chemotherapy (the day 28 BM). Data are presented according to intention-to-treat for all 394 randomly assigned patients (median follow-up, 4.0 years).
RESULTS: The complete remission (CR) rate was 64%, and the 4-year probability of survival (pOS) was 38% (SE, 3%). The day 28 BM status (available in 359 patients) was good (≤ 20% leukemic blasts) in 80% of patients randomly assigned to FLAG/DNX and 70% for patients randomly assigned to FLAG (P = .04). Concerning secondary end points, the CR rate was 69% with FLAG/DNX and 59% with FLAG (P = .07), but overall survival was similar. However, core-binding factor (CBF) AML treated with FLAG/DNX resulted in pOS of 82% versus 58% with FLAG (P = .04). Grade 3 to 4 toxicity was essentially similar in both groups.
CONCLUSION: DNX added to FLAG improves early treatment response in pediatric relapsed AML. Overall long-term survival was similar, but CBF-AML showed an improved survival with FLAG/DNX. International collaboration proved feasible and resulted in the best outcome for pediatric relapsed AML reported thus far.

Rego EM, Kim HT, Ruiz-Argüelles GJ, et al.
Improving acute promyelocytic leukemia (APL) outcome in developing countries through networking, results of the International Consortium on APL.
Blood. 2013; 121(11):1935-43 [PubMed]

Thanks to modern treatment with all-trans retinoic acid and chemotherapy, acute promyelocytic leukemia (APL) is now the most curable type of leukemia. However, this progress has not yielded equivalent benefit in developing countries. The International Consortium on Acute Promyelocytic Leukemia (IC-APL) was established to create a network of institutions in developing countries that would exchange experience and data and receive support from well-established US and European cooperative groups. The IC-APL formulated expeditious diagnostic, treatment, and supportive guidelines that were adapted to local circumstances. APL was chosen as a model disease because of the potential impact on improved diagnosis and treatment. The project included 4 national coordinators and reference laboratories, common clinical record forms, 5 subcommittees, and laboratory and data management training programs. In addition, participating institutions held regular virtual and face-to-face meetings. Complete hematological remission was achieved in 153/180 (85%) patients and 27 (15%) died during induction. After a median follow-up of 28 months, the 2-year cumulative incidence of relapse, overall survival (OS), and disease-free survival (DFS) were 4.5%, 80%, and 91%, respectively. The establishment of the IC-APL network resulted in a decrease of almost 50% in early mortality and an improvement in OS of almost 30% compared with historical controls, resulting in OS and DFS similar to those reported in developed countries.

Blijdorp K, van Waas M, van der Lely AJ, et al.
Endocrine sequelae and metabolic syndrome in adult long-term survivors of childhood acute myeloid leukemia.
Leuk Res. 2013; 37(4):367-71 [PubMed]

This study focuses on the effect of chemotherapy on endocrinopathies and the metabolic syndrome in adult survivors of childhood acute myeloid leukemia (AML). Endocrine function and metabolic syndrome were evaluated in 12 AML survivors, treated with chemotherapy, and in 9 survivors of myeloid leukemias treated with stem cell transplantation (SCT), after a median follow-up time of 20 years (range 9-31). In survivors treated with chemotherapy, no endocrinopathies or metabolic syndrome were present, although AMH and Inhibin B levels tended to be lower than in controls. In SCT survivors, pituitary deficiencies and metabolic syndrome were more frequent.