The Bone's Role in Myeloid Neoplasia

The interaction of hematopoietic stem and progenitor cells with their direct neighboring cells in the bone marrow (the so called hematopoietic niche) evolves as a key principle for understanding physiological and malignant hematopoiesis. Significant progress in this matter has recently been achieved making use of emerging high-throughput techniques that allow characterization of the bone marrow microenvironment at single cell resolution. This review aims to discuss these single cell findings in the light of other conventional niche studies that together define the current notion of the niche's implication in i) normal hematopoiesis, ii) myeloid neoplasms and iii) disease-driving pathways that can be exploited to establish novel therapeutic strategies in the future.

Mixture regression models for the gap time distributions and illness-death processes

The aim of this study is to provide an analysis of gap event times under the illness-death model, where some subjects experience "illness" before "death" and others experience only "death." Which event is more likely to occur first and how the duration of the "illness" influences the "death" event are of interest. Because the occurrence of the second event is subject to dependent censoring, it can lead to bias in the estimation of model parameters. In this work, we generalize the semiparametric mixture models for competing risks data to accommodate the subsequent event and use a copula function to model the dependent structure between the successive events. Under the proposed method, the survival function of the censoring time does not need to be estimated when developing the inference procedure. We incorporate the cause-specific hazard functions with the counting process approach and derive a consistent estimation using the nonparametric maximum likelihood method. Simulations are conducted to demonstrate the performance of the proposed analysis, and its application in a clinical study on chronic myeloid leukemia is reported to illustrate its utility.

Two myeloid leukemia cases with rare FLT3 fusions

Genetic rearrangements involving FLT3 are rare and only recently have been detected in myeloid/lymphoid neoplasms associated with eosinophilia (MLN-eos) and chronic myeloproliferative disorders. Here we report two cases with FLT3 fusions in patients demonstrating mixed features of myelodysplastic/myeloproliferative neoplasms. In the first case, FLT3 was fused with a new fusion partner MYO18A in a patient with marrow features most consistent with atypical chronic myeloid leukemia; the second case involving ETV6-FLT3 fusion was observed in a case with bone marrow features most consistent with chronic myelomonocytic leukemia. Notably, we observed that samples from both patients demonstrated FLT3 inhibitor (quizartinib and sorafenib) sensitivity in ex vivo drug screening assay.

Insulin Substrate Receptor (IRS) proteins in normal and malignant hematopoiesis

The insulin receptor substrate (IRS) proteins are a family of cytoplasmic proteins that integrate and coordinate the transmission of signals from the extracellular to the intracellular environment via transmembrane receptors, thus regulating cell growth, metabolism, survival and proliferation. The PI3K/AKT/mTOR and MAPK signaling pathways are the best-characterized downstream signaling pathways activated by IRS signaling (canonical pathways). However, novel signaling axes involving IRS proteins (noncanonical pathways) have recently been identified in solid tumor and hematologic neoplasm models. Insulin receptor substrate-1 (IRS1) and insulin receptor substrate-2 (IRS2) are the best-characterized IRS proteins in hematologic-related processes. IRS2 binds to important cellular receptors involved in normal hematopoiesis (EPOR, MPL and IGF1R). Moreover, the identification of IRS1/ABL1 and IRS2/JAK2V617F interactions and their functional consequences has opened a new frontier for investigating the roles of the IRS protein family in malignant hematopoiesis. Insulin receptor substrate-4 (IRS4) is absent in normal hematopoietic tissues but may be expressed under abnormal conditions. Moreover, insulin receptor substrate-5 (DOK4) and insulin receptor substrate-6 (DOK5) are linked to lymphocyte regulation. An improved understanding of the signaling pathways mediated by IRS proteins in hematopoiesis-related processes, along with the increased development of agonists and antagonists of these signaling axes, may generate new therapeutic approaches for hematological diseases. The scope of this review is to recapitulate and review the evidence for the functions of IRS proteins in normal and malignant hematopoiesis.

The BMP pathway: A unique tool to decode the origin and progression of leukemia

The microenvironment (niche) governs the fate of stem cells (SCs) by balancing self-renewal and differentiation. Increasing evidence indicates that the tumor niche plays an active role in cancer, but its important properties for tumor initiation progression and resistance remain to be identified. Clinical data show that leukemic stem cell (LSC) survival is responsible for disease persistence and drug resistance, probably due to their sustained interactions with the tumor niche. Bone morphogenetic protein (BMP) signaling is a key pathway controlling stem cells and their niche. BMP2 and BMP4 are important in both the normal and the cancer context. Several studies have revealed profound alterations of the BMP signaling in cancer SCs, with major deregulations of the BMP receptors and their downstream signaling elements. This was illustrated in the hematopoietic system by pioneer studies in chronic myelogenous leukemia that may now be expanded to acute myeloid leukemia and lymphoid leukemia, as reviewed here. At diagnosis, cells from the leukemic microenvironment are the major providers of soluble BMPs. Conversely, LSCs display altered receptors and downstream BMP signaling elements accompanied by altered functional responses to BMPs. These studies reveal the role of BMPs in tumor initiation, in addition to their known effects in later stages of transformation and progression. They also reveal the importance of BMPs in fueling cell transformation and expansion by overamplifying a natural SC response. This mechanism may explain the survival of LSCs independently of the initial oncogenic event and therefore may be involved in resistance processes.

Antiproliferative effect of H2O2 against human acute myelogenous leukemia KG1 cell line

It has clearly been established that oxidative stress leads to perturbation of various cellular processes resulting in either inhibition of cell proliferation or cell death. In addition, there is a growing body of evidence indicating that reactive oxygen species (ROS) are required as signal molecules that regulate different physiological processes including survival or death. Free radicals, particularly ROS, have been proposed as general mediators for apoptosis and recent studies have established that the mode of cell death depends on the severity of the oxidative damage. In this study, we determined the effect of oxidative stress on cell proliferation and characterization of cell death in human KG1 cells treated with H2O2. Our results indicated that oxidative stress leads to a significant decrease in cell proliferation and induction of apoptosis. Moreover, our study suggests that antiproliferative and apoptotic cell death effects of H2O2 took place via activation of caspase-3, affecting the expression of Bcl-2 and Bax (an antiapoptotic and a proapoptotic factor, respectively), and through deactivation of catalase enzyme, leading to accumulation of intracellular ROS and depletion of intracellular ATP level.

[Clinical and functional symptoms of funicular myelosis and chronic gastritis in patients with B12-deficiency anemia]

The aim of this work was to study clinical and functional symptoms of funicular myelosis (FM) and chronic gastritis (CG) in patients with B12-deficiency anemia. A total of 77 patients with diagnosis verified by finding megaloblasts in bone marrow biopsies were examined. Clinical symptoms of FM were found in 57% of the patients. The most characteristic subjective ones were paresthesia (83.3%) and limb weakness (60%) while objective symptoms included impaired limb sensitivity (100%). All patients suffered CG with lesions in both antrum and fundus.

Identification of genomic aberrations associated with disease transformation by means of high-resolution SNP array analysis in patients with myeloproliferative neoplasm

Myeloproliferative neoplasms (MPN) include polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). These disorders may undergo phenotypic shifts, and may specifically evolve into secondary myelofibrosis (MF) or acute myeloid leukemia (AML). We studied genomic changes associated with these transformations in 29 patients who had serial samples collected in different phases of disease. Genomic DNA from granulocytes, i.e., the myeloproliferative genome, was processed and hybridized to genome-wide human SNP 6.0 arrays. Most patients in chronic phase had chromosomal regions with uniparental disomy (UPD) and/or copy number changes. Disease progression to secondary MF or AML was associated with the acquisition of additional chromosomal aberrations in granulocytes (P = 0.002). A close relationship was observed between aberrations of chromosome 9p (UPD and/or gain) and progression from PV to post-PV MF (P = 0.002). The acquisition of one or more aberrations involving chromosome 5, 7, or 17p was specifically associated with progression to AML (OR 5.9, 95% CI 1.2-27.7, P = 0.006), and significantly affected overall survival (HR 18, 95% CI 1.9-164, P = 0.01). These observations indicate that disease progression from chronic-phase MPN to secondary MF or AML is associated with specific chromosomal aberrations that can be detected by means of high-resolution SNP array analysis of granulocyte DNA.

Molecular mechanisms of leukemia-associated protein degradation

Chemical biology, using small molecules as probes to study the cellular signaling network, has developed rapidly in recent years. The interaction between chemistry and biology not only provides new insight into the understanding of cellular activities, but also generates new lead compounds for the treatment of diseases. Transcription factors and kinases such as retinoic acid receptor-alpha (RARα), acute myeloid leukemia 1 (AML1), CAAT/enhancer-binding protein α (C/EBPα), c-myc, and c-abl play important roles in the differentiation of hematopoietic stem/progenitor cells. Abnormalities in these proteins may cause the dysregulation of hematopoiesis and even the occurrence of leukemia. Ubiquitin-mediated protein degradation represents a critical mechanism in regulating the cellular levels and functions of these proteins. Thus, targeting protein degradation has been emerging as an important strategy to conquer malignant diseases. In this review, we will summarize the recent advances in the understanding of the roles of protein degradation in leukemia, with an emphasis on the mechanisms revealed by small molecules.

Sp1/NFkappaB/HDAC/miR-29b regulatory network in KIT-driven myeloid leukemia

The biologic and clinical significance of KIT overexpression that associates with KIT gain-of-function mutations occurring in subsets of acute myeloid leukemia (AML) (i.e., core binding factor AML) is unknown. Here, we show that KIT mutations lead to MYC-dependent miR-29b repression and increased levels of the miR-29b target Sp1 in KIT-driven leukemia. Sp1 enhances its own expression by participating in a NFkappaB/HDAC complex that further represses miR-29b transcription. Upregulated Sp1 then binds NFkappaB and transactivates KIT. Therefore, activated KIT ultimately induces its own transcription. Our results provide evidence that the mechanisms of Sp1/NFkappaB/HDAC/miR-29b-dependent KIT overexpression contribute to leukemia growth and can be successfully targeted by pharmacological disruption of the Sp1/NFkappaB/HDAC complex or synthetic miR-29b treatment in KIT-driven AML.

Increased cellular hypoxia and reduced proliferation of both normal and leukaemic cells during progression of acute myeloid leukaemia in rats

The microenvironmental changes in the bone marrow, spleen and liver during progression of the transplantable promyelocytic leukaemia in the Brown Norwegian rat (BNML) have been studied. We used flow cytometry to estimate cellular hypoxia and proliferation based on in vivo pulse-labelling with a mixture of 2-nitroimidazole linked to theophylline (NITP) and bromodeoxyuridine (BrdUrd). The leukaemic cells were identified with the RM124 antibody. In rats inoculated with leukaemic cells the fraction of RM124+ cells was significantly increased from day 20 onwards in the spleen and from day 27 in the bone marrow and liver, reaching a level of 65-87% in these organs at day 32. At day 32, the NITP+ fraction of RM124+ cells had increased significantly in the bone marrow and spleen to 88% and 90%, respectively. The corresponding fractions of NITP+ normal cells reached 63% and 65%, respectively. From day 13 to day 32, the DNA-synthesizing (BrdUrd+) fraction of RM124+ cells in the bone marrow decreased significantly from 52% to 25%, and of normal cells from about 20% to 6%. In the bone marrow and spleen at day 27 and 32, the S-phase and G2/M-phase fractions according to DNA content were higher for the NITP+ than for the NITP- cells. This could partly be explained by an impaired cell cycle progression due to hypoxia. Nevertheless, we found indications of leukaemic cells that were simultaneously labelled with NITP and BrdUrd, in the bone marrow and spleen. These latter findings suggest that in contrast to normal cells some of the leukaemic cells can proliferate even during hypoxia, and this subpopulation may consequently renew and expand the leukaemic cell load.

The impact of acute myeloid leukemia and its treatment on quality of life and functional status in older adults

Although intensive chemotherapy (IC) may modestly improve survival compared to supportive care in older people with acute myeloid leukemia (AML), treatment may worsen quality of life (QOL) and functional status. We assessed QOL and functional status at baseline, 1 month, 4 months, and 6 months in 65 consecutive, English-speaking, patients age 60 or older with newly diagnosed AML. At baseline, functional status was high but QOL was negatively affected in global health and most QOL domains. Over time, QOL remained stable or improved in most patients and was generally similar between IC and non-IC groups. Basic activities of daily living (ADL) scores did not change over time, whereas instrumental ADL scores declined slightly regardless of treatment. Receiving IC does not appear to lead to worse QOL or functional status than more palliative approaches. This information may aid treatment discussions in older patients with AML.

Time-course-dependent microvascular alterations in a model of myeloid leukemia in vivo

Functional and morphological properties of tumor microcirculation play a pivotal role in tumor progression, metastasis and inefficiency of tumor therapies. Despite enormous insights into tumor angiogenesis in solid tumors, little is known about the time-course-dependent properties of tumor vascularization in hematologic malignancies. The aim of this study was to establish a model of myeloid leukemia, which allows long-term monitoring of tumor progression and associated microcirculation. Red fluorescent protein-transduced human leukemic cell lines (M-07e) were implanted into cranial windows of severe combined immunodeficient mice. Intravital microscopy was performed over 55 days to measure functional (microvascular permeability, tissue perfusion rate and leukocyte-endothelium interactions) and morphological vascular parameters (vessel density, distribution and diameter). Tumor progression was associated with elevated microvascular permeability and an initial angiogenic wave followed by decreased vessel density combined with reduced tissue perfusion due to loss in small vessels and development of heterogenous tumor vascularization. Following altered geometric resistance of microcirculation, leukocyte-endothelium interactions were more frequent without increased leukocyte extravasation. It was concluded that time-dependent alterations of leukemic tumor vascularization exhibit strong similarities to those found in solid tumors. The potential contribution to the development of barriers to drug delivery in leukemic tumors is discussed.

EWS/FLI-1 induces rapid onset of myeloid/erythroid leukemia in mice

EWS/FLI-1 is a chimeric oncogene generated by chromosomal translocation in Ewing tumors, a family of poorly differentiated pediatric tumors arising predominantly in bone but also in soft tissue. The fusion gene combines sequences encoding a strong transactivating domain from the EWS protein with the DNA binding domain of FLI-1, an ETS transcription factor. A related fusion, TLS/ERG, has been found in myeloid leukemia. To determine EWS/FLI-1 function in vivo, we engineered mice with Cre-inducible expression of EWS/FLI-1 from the ubiquitous Rosa26 locus. When crossed with Mx1-cre mice, Cre-mediated activation of EWS/FLI-1 resulted in the rapid development of myeloid/erythroid leukemia characterized by expansion of primitive mononuclear cells causing hepatomegaly, splenomegaly, severe anemia, and death. The disease could be transplanted serially into naïve recipients. Gene expression profiles of primary and transplanted animals were highly similar, suggesting that activation of EWS/FLI-1 was the primary event leading to disease in this model. The Cre-inducible EWS/FLI-1 mouse provides a novel model system to study the contribution of this oncogene to malignant disease in vivo.

Adding low-dose gemtuzumab ozogamicin to fludarabine, Ara-C and idarubicin (MY-FLAI) may improve disease-free and overall survival in elderly patients with non-M3 acute myeloid leukaemia: results of a prospective, pilot, multi-centre trial and comparison with a historical cohort of patients

We report the final results of a prospective multi-centre trial testing the combination of chemotherapy (fludarabine, cytosine arabinoside and idarubicin; FLAI) followed by low-dose gemtuzumab ozogamicin (GO), for induction treatment of patients with CD33+ acute myeloid leukaemia (AML). Forty-six consecutive patients were treated: the median age was 66 (range: 60-80) years; the karyotype was unfavourable in 12 patients (26%), intermediate in 33 (71%) and favourable in one (3%). Eleven major infectious complications were recorded. There was one early death. Of the 45 evaluable patients, 24 achieved a complete response (CR; 52%), 66% and 33% in good-intermediate/poor karyotype patients. Median duration of CR was 7 (3-24) months. The cumulative incidence of relapse was 37% with an actuarial 2-year survival of 54%. These results were compared with 47 patients matched for age and karyotype who received FLAI, without GO. The proportion of patients achieving CR was comparable. However, patients with de novo AML receiving GO (n = 26) had a significantly lower risk of relapse at 2 years when compared with patients not receiving GO (n = 35) (40% vs. 80%, P = 0.01) and significantly better overall 2-year survival (40% vs. 14%P = 0.02). Patients with secondary AML had comparable outcome whether or not they received GO. This GO-based induction chemotherapy has a good toxicity profile. In keeping with a recent prospective randomised trial, the addition of GO seems to prolong disease-free survival.

Transformation of cytogenetically normal chronic myelomonocytic leukaemia to an acute myeloid leukaemia and the emergence of a novel +13, +15 double trisomy resulting in an adverse outcome

A 58-year-old man was admitted with symptoms of lethargy and easy bruising for four months duration. Peripheral blood (PB) analysis revealed a white blood cell count (WBC) of 15.9 x 10(9)/l with monocytes 5.4 x 10(9)/l. Bone marrow (BM) was hypercellular with 15% blasts, monocytosis and trilineage dysplasia. Conventional cytogenetic analysis (G-banding) detected an apparently normal male karyotype (46,XY). A diagnosis of chronic myelomonocytic leukaemia (CMML) was made. After 3 years, PB analysis revealed a WBC count of 22 x 10(9)/l and a predominance of blasts. BM aspirate analysis also revealed 89% myeloid blasts and G-banding detected the emergence of an abnormal clone harbouring an extra copy of chromosomes 13 and 15. A diagnosis of disease transformation to acute myeloid leukaemia (AML) was made. Post chemotherapy BM aspirate was very hypocellular and the abnormal +13, +15 clone was still present suggesting primary refractory disease. A second course of chemotherapy was only administered for 24 hours due to complications. The abnormal +13, +15 clone was still present and it was decided that no further treatment apart from palliative care could be offered. The patient died 11 weeks later, five months after AML transformation. This is the first description of a cytogenetically normal CMML patient transforming to AML with the emergence of a unique +13, +15 double trisomy resulting in an adverse outcome.

The criteria for bone marrow recovery post-myelosuppressive therapy for acute myelogenous leukemia: a quantitative study

CONTEXT

Although the early post-myelosuppressive chemotherapy pathologic changes of the marrow have been described, the rate and the histologic definition of recovery are not defined.

OBJECTIVE

To study the rate of recovery of bone marrow in patients given myelosuppressive therapy for acute myelogenous leukemia, establish the histologic criteria of recovered marrow, and correlate the recovery pattern with those patients who received a bone marrow transplant by using histology, peripheral blood, immunophenotyping, and computerized morphometry and mathematical slope equation.

DESIGN

We studied the post-myelosuppression recovery of the bone marrow to determine patterns and rate of recovery in 135 serial bone marrow biopsies of 51 patients. These patients were divided into 2 groups: 1 group of 28 cases diagnosed with acute myeloid leukemia, the majority treated with cytarabine (Ara-C) infusion for 7 days and daunorubicin intravenously daily for 3 days (7+3 regimen), and the other control group of 23 cases treated with chemotherapy or allogeneic bone marrow transplantation for a variety of hematologic malignancies. All biopsies during the recovery period were obtained before consolidation regimen. We used morphometry to calculate the cellularity and myeloid to erythroid ratio and quantified megakaryocytes CD10 versus time from day 14 onward. The absolute neutrophil and platelet counts for 28 cases were related to histologic recovery.

RESULTS

From day 14, we noted a differential slope of recovery of these patients with no difference in male and female patients, P = .45, but a difference between younger and older patients (>58.5 years), P = .03. After regenerative hyperplasia, the cellularity plateaus, the myeloid to erythroid ratio, and the megakaryocytes even out with platelet normalization, and the early CD10+ B cells rise from day 40 onward, P = .01. The patterns of recovery after day 60 of postchemotherapy and posttransplantation patients are similar. Complete histologic and peripheral blood recovery is noted at day 38 and thereafter.

CONCLUSIONS

By linear equation using at least 2 trephine biopsy specimens, the projected rate of cellular recovery may be determined, and 5 histologic features are associated with complete histologic recovery.

Concise review: Telomere biology in normal and leukemic hematopoietic stem cells

The measurement of telomere length can give an insight into the replicative history of the cells in question. Much of the observed telomere loss occurs at the stem and progenitor cell level, even though these populations express the enzyme telomerase. Telomerase-transfected hematopoietic stem cells (HSC), although able to maintain telomere length, are still limited in terms of ability to undergo sequential transplantation, and other factors require to be addressed to achieve optimal levels of stem cell expansion. Unchecked telomere loss by HSC, meanwhile, would appear to play a significant role in the pathogenesis of bone marrow failure, as observed in the condition dyskeratosis congenita. This heterogeneous inherited condition appears to exhibit telomerase dysfunction as a common final pathogenic mechanism. Although less well-established for acquired marrow failure syndromes, mutations in key telomerase components have been described. The identification of the leukemic stem cell (LSC), along with the desire to target this population with anti-leukemia therapy, demands that telomerase biology be fully understood in this cell compartment. Future studies using primary selected LSC-rich samples are required. A better understanding of telomerase regulation in this population may allow effective targeting of the telomerase enzyme complex using small molecule inhibitors or additional novel approaches. Disclosure of potential conflicts of interest is found at the end of this article.

Modeling the initiation and progression of human acute leukemia in mice

Our understanding of leukemia development and progression has been hampered by the lack of in vivo models in which disease is initiated from primary human hematopoietic cells. We showed that upon transplantation into immunodeficient mice, primitive human hematopoietic cells expressing a mixed-lineage leukemia (MLL) fusion gene generated myeloid or lymphoid acute leukemias, with features that recapitulated human diseases. Analysis of serially transplanted mice revealed that the disease is sustained by leukemia-initiating cells (L-ICs) that have evolved over time from a primitive cell type with a germline immunoglobulin heavy chain (IgH) gene configuration to a cell type containing rearranged IgH genes. The L-ICs retained both myeloid and lymphoid lineage potential and remained responsive to microenvironmental cues. The properties of these cells provide a biological basis for several clinical hallmarks of MLL leukemias.

The potential effect of gender in combination with common genetic polymorphisms of drug-metabolizing enzymes on the risk of developing acute leukemia

BACKGROUND AND OBJECTIVES

We examined common polymorphisms in the genes for glutathione S-transferase (GST), cytochrome P450 (CYP), quinone oxoreductase (NQO1), methylene tetrahydrofolate reductase (MTHFR), and thymidylate synthetase (TYMS) and the role of gender associated with the susceptibility to de novo acute leukemia (AL).

DESIGN AND METHODS

We conducted a case-control study analyzing the prevalence of the polymorphisms CYP1A1*2A, CYP2E1*5B, CYP3A4*1B, del{GSTT1}, del{GSTM1}, NQO1*2, MTHFR C6777, and TYMS 2R/3R in 443 patients with AL [302 with acute myeloblastic leukemia (AML) and 141 with acute lymphoblastic leukemia (ALL)] and 454 control volunteers, using polymerase chain reaction (PCR)-based methods.

RESULTS

We found a higher incidence of del{GSTT1} in patients with AML than among controls (25.6% vs. 13.7%, OR=2.2, p<0.001) and a higher incidence of NQO1*2 homozygosity (NQO1*2hom.) in males with the M3 FAB subtype than in control males (8.6% vs. 2.2%, OR=4.9, p=0.02). The del{GSTT1} and NQO1*2hom. polymorphisms increased the risk of ALL (OR=2.2 and 3.0, p=0.001 and 0.003, respectively). The higher risk conferred by NQO1*2hom. and del{GSTT1} mainly affected males (OR=6.1 and 2.4; p=0.002 and 0.005, respectively).

INTERPRETATION AND CONCLUSIONS

Males harboring NQO1*2hom. and del{GSTT1} polymorphisms showed a higher risk than females of developing AL. Thus, gender might influence the risk of AL associated with these genetic polymorphisms.

Overexpression of the local bone marrow renin-angiotensin system in acute myeloid leukemia

OBJECTIVES

Local bone marrow renin-angiotensin system (RAS) is an autocrine-paracrine system affecting hematopoiesis. Angiotensin II stimulates the proliferation of bone marrow and umbilical cord blood hematopoietic progenitors. Angiotensin-converting enzyme (ACE) hyperfunction may lead to the acceleration of negative hematopoietic regulator peptide, AcSDKP, metabolism, which in turn lowers its level in the bone marrow microenvironment, finally removing the antiproliferative effect of AcSDKP on the hematopoietic cells and blasts. The aim of this study is therefore to search those major RAS components simultaneously in the leukemic blast cells taken from the bone marrow of patients with acute myeloid leukemia (AML).

METHODS

Bone marrow aspiration materials were obtained from 10 patients with AML (8 males, 2 females; median age 48.5 years) and 8 patients with nonmalignant hematological disorders (6 males, 2 females; median age 45 years). EDTA-treated bone marrow samples were stored at -70 degrees C until analysis. Total RNA was extracted from 200-microl bone marrow samples by High Pure RNA Isolation Kit.

RESULTS

The medians of expression ratios of AML patient samples have been found 0.736 (IQR 1.359), 0.540 (IQR 0.725), and 0.075 (IQR 0.002) for ACE, ANG and REN genes, respectively. All three gene expressions were found to be significantly higher in the bone marrow samples of AML patients.

CONCLUSION

In this study, the expression of the mRNAs of the major RAS components-namely ACE, renin and angiotensinogen-in human bone marrow samples were quantified by reverse transcription-polymerase chain reaction (RT-PCR) to confirm the presence of the local bone marrow RAS. Elucidation of the pathological activity of the local RAS-mediated regulation of the leukemogenesis is both pathobiologically and clinically important, since the angiotensin peptides represent a molecular target in the disease management.

Acute myeloid leukaemia

Acute myeloid leukaemia (AML) is a heterogeneous clonal disorder of haemopoietic progenitor cells and the most common malignant myeloid disorder in adults. The median age at presentation for patients with AML is 70 years. In the past few years, research in molecular biology has been instrumental in deciphering the pathogenesis of the disease. Genetic defects are thought to be the most important factors in determining the response to chemotherapy and outcome. Whereas significant progress has been made in the treatment of younger adults, the prospects for elderly patients have remained dismal, with median survival times of only a few months. This difference is related to comorbidities associated with ageing and to disease biology. Current efforts in clinical research focus on the assessment of targeted therapies. Such new approaches will probably lead to an increase in the cure rate.

Exisulind induces apoptosis in advanced myelodysplastic syndrome (MDS) and acute myeloid leukaemia/MDS

The influence of Exisulind on the viability and apoptosis of CD34(+) stem cells from patients with advanced myelodysplastic syndrome (MDS) and acute myeloid leukaemia (AML)/MDS was investigated. In eight out of 10 patient samples Exisulind reduced the fraction of viable cells by inducing apoptosis. We found evidence that Exisulind-mediated apoptosis depends on c-Jun NH(2)-terminal kinase (JNK) activation. Addition of a specific JNK-inhibitor to Exisulind-treated advanced MDS and AML/MDS cells partly abrogated apoptosis. We propose that Exisulind is tested in clinical phase I/II trials for the treatment of advanced MDS and AML/MDS.

In vitro induction of apoptosis in U937 cells by perillyl alcohol with sensitization by pentoxifylline: increased BCL-2 and BAX protein expression

BACKGROUND

Chemotherapy is effective against a wide variety of tumor cells, although its use is limited by side effects. In vitro experiments and phase I and II trials have shown that phytochemicals such as perillyl alcohol (P-OH) have antitumor effects. Pentoxifylline (PTX), a synthetic methylxanthine used mainly to treat pathologies associated with hematological diseases, sensitizes tumor cells to chemotherapy. The aim of this study was to determine whether PTX amplifies the antitumor effects of P-OH in U937 human myelomonocytic leukemia cells.

METHODS

Apoptosis was measured by the loss of mitochondrial membrane potential determined by flow cytometry using dihexyloxacarbocyanine iodide (DiOC6) and propidium iodide. Bcl-2 and Bax protein expression was also assessed by Western blot analysis.

RESULTS

P-OH and PTX induced loss of the mitochondrial membrane potential in U937 cells in vitro. Culturing the cells in the presence of both compounds caused a significant increase (p < 0.001) in apoptosis and expression of anti-apoptotic Bcl-2 and pro-apoptotic Bax proteins. However, despite their coexistence, Bax expression prevailed in our experiments. These data suggest that the effects of PTX might be attributable to changes in the mitochondrial membrane potential.

CONCLUSION

PTX sensitizes tumor cells to the anti-neoplastic action of P-OH. These observations may have clinical relevance in the treatment of cancer patients.

Downregulation of topoisomerase IIbeta in myeloid leukemia cell lines leads to activation of apoptosis following all-trans retinoic acid-induced differentiation/growth arrest

Among the topoisomerase (topo) II isozymes (alpha and beta), topo IIbeta has been suggested to regulate differentiation. In this study, we examined the role of topo IIbeta in all-trans retinoic acid (ATRA)-induced differentiation of myeloid leukemia cell lines. Inhibition of topo IIbeta activity or downregulation of protein expression enhanced ATRA-induced differentiation/growth arrest and apoptosis. ATRA-induced apoptosis in topo IIbeta-deficient cells involved activation of the caspase cascade and was rescued by ectopic expression of topo IIbeta. Gene expression profiling led to the identification of peroxiredoxin 2 (PRDX2) as a candidate gene that was downregulated in topo IIbeta-deficient cells. Reduced expression of PRDX2 validated at the mRNA and protein level, in topo IIbeta-deficient cells correlated with increased accumulation of reactive oxygen species (ROS) following ATRA-induced differentiation. Overexpression of PRDX2 in topo IIbeta-deficient cells led to reduced accumulation of ROS and partially reversed ATRA-induced apoptosis. These results support a role for topo IIbeta in survival of ATRA-differentiated myeloid leukemia cells. Reduced expression of topo IIbeta induces apoptosis in part by impairing the anti-oxidant capacity of the cell owing to downregulation of PRDX2. Thus, suppression of topo IIbeta and/or PRDX2 levels in myeloid leukemia cells provides a novel approach for improving ATRA-based differentiation therapy.

T lymphocyte chemotactic chemokines in acute myelogenous leukemia (AML): local release by native human AML blasts and systemic levels of CXCL10 (IP-10), CCL5 (RANTES) and CCL17 (TARC)

T cell targeting immunotherapy is now considered in acute myelogenous leukemia (AML), and local recruitment of antileukemic T cells to the AML microcompartment will then be essential. This process is probably influenced by both intravascular as well as extravascular levels of T cell chemotactic chemokines. We observed that native human AML cells usually showed constitutive secretion of the chemotactic chemokines CXCL10 and CCL5, whereas CCL17 was only released for a subset of patients and at relatively low levels. Coculture of AML cells with nonleukemic stromal cells (i.e., fibroblasts, osteoblasts) increased CXCL10 and CCL17 levels whereas CCL5 levels were not altered. However, a wide variation between patients in both CXCL10 and CCL5 levels persisted even in the presence of the stromal cells. Neutralization of CXCL10 and CCL5 inhibited T cell migration in the presence of native human AML cells. Furthermore, serum CCL17 and CXCL10 levels varied between AML patients and were determined by disease status (both chemokines) as well as patient age, chemotherapy and complicating infections (only CCL17). Thus, extravascular as well as intravascular levels of T cell chemotactic chemokines show a considerable variation between patients that may be important for T cell recruitment and the effects of antileukemic T cell reactivity in local AML compartments.

Ral is both necessary and sufficient for the inhibition of myeloid differentiation mediated by Ras

Hyperactivation of Ras is one of the most common abnormalities in acute myeloid leukemia. In experimental models, Ras inhibits myeloid differentiation, which is characteristic of leukemia; however, the mechanism through which it disrupts hematopoiesis is poorly understood. In multipotent FDCP-mix cells, Ras inhibits terminal neutrophil differentiation, thereby indefinitely extending their proliferative potential. Ras also strongly promotes the sensitivity of these cells to granulocyte-macrophage colony-stimulating factor (GM-CSF). Using this model, we have dissected the signaling elements downstream of Ras to determine their relative contribution to the dysregulation of hematopoiesis. Cells expressing Ras mutants selectively activating Raf (Ras*T35S) or phosphatidylinositol 3-kinase (Ras*Y40C) did not significantly affect differentiation or proliferative capacity, whereas Ras*E37G (which selectively activates RalGEFs) perpetuated proliferation and blocked neutrophil development in a manner similar to that of Ras. Correspondingly, expression of constitutively active versions of these effectors confirmed the overriding importance of Ral guanine nucleotide exchange factors. Cells expressing Ras demonstrated hyperactivation of Ral, which itself was able to exactly mimic the phenotype of Ras, including hypersensitivity to GM-CSF. Conversely, dominant negative Ral promoted spontaneous neutrophil development. Ral, in turn, appears to influence differentiation through multiple effectors. These data show, for the first time, the importance of Ral in regulating differentiation and self-renewal in hematopoietic cells.

Inducer-and cell type-specific regulation of antiapoptotic MCL1 in myeloid leukemia and multiple myeloma cells exposed to differentiation-inducing or microtubule-disrupting agents

The antiapoptotic BCL2 family member MCL1 is rapidly upregulated upon exposure of ML-1 myeloid leukemia cells to either differentiation-inducing phorbol 12'-myristate 13'-acetate (PMA) or chemotherapeutic microtubule disrupting agents (MTDAs). This report examined how signaling for MCL1 upregulation is coupled to these two different phenotypic changes, and tested for upregulation in other hematopoietic cancers. With PMA, ERK stimulated MCL1 mRNA expression and ML-1 cell differentiation, and ERK additionally stabilized expression of the MCL1 protein. However, with MTDAs, transient ERK and ensuing JNK activation contributed to initial MCL1 upregulation and viability-retention, but sustained JNK activation eventually resulted in cell death. MCL1 was upregulated by PMA in THP-1 and U937 myeloid leukemia cells, but by MTDAs only in THP-1 cells. MCL1 expression was constitutively elevated in multiple myeloma cell lines, and was not affected by PMA/ERK or MTDAs. Thus, MCL1 expression level and sensitivity to regulation are important considerations in selecting approaches for targeting this antiapoptotic gene product to kill cancer cells.

Inherited predispositions and hyperactive Ras in myeloid leukemogenesis

Identifying the molecular basis for inherited cancer predispositions reveals genes that when mutated, play a critical role in the earliest stages of tumorigenesis. Although rare, inherited predispositions to myeloid leukemias have led to a greater understanding of pathways important for myeloid proliferation and maturation. In particular, elucidating why children with neurofibromatosis type 1 (NF1) and Noonan syndrome (NS) are predisposed to juvenile myelomonocytic leukemia (JMML) has uncovered a critical role of hyperactive Ras signaling in normal myeloid growth and leukemogenesis. Here, we review studies of human samples and experiments performed in genetically engineered strains of mice investigating the molecular and biochemical basis of aberrant growth in JMML. These strains model human disease features and provide an opportunity to investigate novel therapeutic strategies that may ultimately cure JMML and other myeloid malignancies characterized by hyperactive Ras.

Curing childhood acute myeloid leukemia (AML) at the half-way point: promises to keep and miles to go before we sleep

Childhood and adolescent acute myeloid leukemia (AML) is traditionally one of the hardest childhood cancers to successfully treat and had an overall survival well under 10% in the 1960s. Initial progress was made by three major events: (1) active chemotherapeutic agents were identified which led to remissions for the first time in this disease; (2) cooperative groups were instituted leading to important clinical trials; and (3) several single institutions began experimenting with the role of allogeneic matched sibling donor (MSD) BMT as effective intensification. Over the last 25 years, the cure rate has improved from <20% to 50% or higher. Most of the clinical research during this time of great advancement focused on two major themes: (1) the role of aggressive induction therapy in not only improving CR rates but in post-remission outcomes; and (2) the role of aggressive post-remission therapy in further improving survival, with an emphasis on high-dose Ara C-based chemotherapy, BMT, and supportive care. But we have "miles to go before we sleep." Some of the challenges that will lead to ongoing reduction of population-based mortality for AML through young adulthood include: (1) improving access of adolescents to pediatric AML therapy; (2) stratification by prognostic factors; (3) individualized therapy based on individual genetics and leukemia cell biology; (4) and the use of novel therapies including targeted immuno-conjugates and "small molecules" which disrupt abnormal signal transduction pathways. This brief review looks at both the advances over the last three decades as well as discusses the challenges moving forward for ultimately curing all children with this disease.

Diagnosis and monitoring of AML1-MTG8 (ETO)-positive acute myeloid leukemia by qualitative and real-time quantitative RT-PCR

Assessing the level of residual disease in leukemia is vital for evaluating patients' response to treatment and for identifying those at high risk of relapse. This should enable early preemptive intervention to prevent the onset of hematological relapse in those patients. One of the most common translocations in acute myeloid leukemia (AML) is the t(8;21). t(8;21) AML is characterized by a relatively good prognosis. This chapter discusses both qualitative and quantitative (real-time quantitative reverse-transcription polymerase chain reaction [RQ-PCR]) protocols for the diagnosis and minimal residual disease (MRD) monitoring in t(8;21) AML. It also discusses the importance of choosing appropriate controls for each assay. The chapter provides a simple equation for assessing the sensitivity/reliability of RQ-PCR assays, which enables scientists to assess the accuracy and reliability of their data.

Treatment of childhood acute myeloid leukemia

Childhood acute myeloid leukemia is rare, but accounts for a significant number of malignancy-related deaths in this age group. However, the prognosis has improved over past decades, and survival rates of 60% and above have been reported. Still, this implies that more than a third of children and adolescents die from this disease. Moreover, treatment is intensive, and quality of life and late effects are worrying issues. Therefore, there is a need for further improved treatment of pediatric acute myeloid leukemia. This review describes several important developments in this respect, such as improved diagnostics, prognostic factors, subgroup-directed and tailored treatment, and targeted therapy. In addition, background information is provided and current treatment strategies are described, as well as the late effects of treatment. Most groups now have risk-group adapted protocols, with allogeneic stem cell transplantation often being reserved for the higher risk group. Even in these cases, the benefit of stem cell transplantation has not been demonstrated beyond reasonable doubt with current high-intensive chemotherapy. Similarly, the use of cranial irradiation for CNS prophylaxis and maintenance treatment does not seem to be indicated in general. Subgroup-directed treatment has become a reality for acute myeloid leukemia in young children with Down's syndrome and in acute promyelocytic leukemia. In addition to tailoring therapy according to biologic features and especially monitoring treatment by measurements of minimal residual disease, targeted therapy for subgroups with activating mutations in receptor tyrosine kinases will further optimize the treatment of pediatric acute myeloid leukemia. Together with the development of many novel agents that have different mechanisms of action than the currently available anticancer agents, and improved supportive care, it is realistic that the prognosis of acute myeloid leukemia in children and adolescents will improve further in the next 5-10 years.

Nuclear phospholipase C beta1, regulation of the cell cycle and progression of acute myeloid leukemia

A large number of observations have hinted at the fact that location impinges on function of some of the main players of nuclear inositol lipid cycle. PLC beta1 is a well-known example, given that it has been shown that only the enzyme located in the nucleus targets the cyclin D3/cdk4 complex, playing, in turn, a key role in the control of normal progression through the G1 phase of the cell cycle. The PLC beta1 gene, which is constituted of 36 small exons and large introns, maps on the short arm of human chromosome 20 (20pl2, nearby markers D20S917 and D20S177) with the specific probe (PAC clone HS881E24) spanning from exon 19 to 32 of the gene itself. The chromosome band 20pl2 has been shown to be rearranged in human diseases such as solid tumors without a more accurate definition of the alteration, maybe because of the absence of candidate genes or specific probes. Moreover, non-specific alterations in chromosome 20 have been found in patients affected by MDS and acute myeloid leukemia AML. MDS is an adult hematological disease that evolves into AML in about 30% of the cases. The availability of a highly specific probe gave an opportunity to perform in patients affected with MDS/AML, associated with normal karyotype, painting and FISH analysis aimed to check the PLC beta1 gene, given that this signaling molecule is a key player in the control of some checkpoints of the normal progression through the cell cycle. FISH analysis disclosed in a small group of MDS/AML patients with normal karyotype the monoallelic deletion of the PLC beta1 gene. In contrast, PLC beta4, another gene coding for a signaling molecule, located on 20pl2.3 at a distance as far as less than 1 Mb from PLC beta1, is unaffected in MDS patients with the deletion of PLC beta1 gene, hinting at an interstitial deletion. The MDS patients, bearing the deletion, rapidly evolved to AML, whilst the normal karyotype MDS patients, showing non-deletion of PLC beta1 gene, are still alive at least 24 months after the diagnosis. The immunocytochemical analysis using an anti PLC beta1 monoclonal antibody showed that all the AML/MDS patients who were normal at FISH analysis also had normal staining of the nucleus, which is a preferential site for PLC beta1. In contrast, the monoallelic deletion gave rise to a dramatic decrease of the nuclear staining suggesting a decreased expression of the nuclear PLC beta1. The reported data strengthen the contention of a key role played by PLC beta1 in the nucleus, suggest a possible involvement of PLC beta1 in the progression of MDS to AML and pave the way for a larger investigation aimed at identifying a possible high risk group among MDS patients with a normal karyotype.

CBFbeta-SMMHC slows proliferation of primary murine and human myeloid progenitors

CBFbeta-SMMHC is expressed in 8% of acute myeloid leukemias and inhibits AML1/RUNX1. In this study, murine marrow or human CD34(+) cells were transduced with retroviral or lentiviral vectors expressing CBFbeta-SMMHC or two mutant variants. CBFbeta-SMMHC reduced murine or human myeloid cell proliferation three- to four-fold in liquid culture relative to empty vector-transduced cells, during a period when vector-transduced cells accumulated five-fold and human cells 20-fold. CBFbeta-SMMHC decreased the formation of myeloid, but not erythroid, colonies two- to four-fold, and myeloid colonies expressing CBFbeta-SMMHC were markedly reduced in size. However, CBFbeta-SMMHC did not slow differentiation to granulocytes or monocytes. Neither CBFbeta-SMMHC(Delta2-11), which does not bind AML1, nor CBFbeta-SMMHC(DeltaACD), which does not multimerize or efficiently bind corepressors, slowed proliferation or reduced myeloid colonies. CBFbeta-SMMHC increased the G1/S ratio 1.4-fold. AML1 had an effect opposite to CBFbeta-SMMHC, stimulating proliferation of murine myeloid progenitors 2.0-fold in liquid culture. Thus, CBFbeta-SMMHC directly inhibits the proliferation of normal myeloid progenitors via inhibition of AML1 and dependent upon the integrity of its assembly competence domain. These findings support the development of therapeutics that target the ability of CBFbeta-SMMHC to interact with AML1 or to multimerize via its assembly competence domain.

The Runx1 transcription factor controls CSF-1-dependent and -independent growth and survival of macrophages

Gene translocations that repress the function of the Runx1 transcription factor play a critical role in the development of myeloid leukemia. In this report, we demonstrate that Runx1 precisely regulates c-fms (CSF-1 receptor) gene expression. Runx1 controlled expression by binding to multiple sites within the mouse c-fms gene, allowing interaction between promoter and downstream enhancer elements. The runx1 and c-fms genes showed an identical pattern of expression in mature macrophages. Runx1 expression was repressed in CSF-1 stimulated, proliferating bone marrow-derived macrophages (BMM) and significantly increased in quiescent, CSF-1 starved cells. The RAW264.7 and Mono-Mac-6, macrophage-like cell lines expressed low levels of Runx1 and both showed growth arrest and cell death with ectopic expression of Runx1. The EM-3 cell line, which represents an early myeloid progenitor cell line, showed growth arrest with Runx1 expression in the absence of any detectable changes in cell differentiation. These findings suggest that Runx1 regulates growth and survival of myeloid cells and provide a novel insight into the role of Runx family gene translocations in leukemogenesis.

A mutation in the Icsbp1 gene causes susceptibility to infection and a chronic myeloid leukemia-like syndrome in BXH-2 mice

BXH-2 mice develop a fatal myeloid leukemia by a two-step mutagenic process. First, a BXH-2-specific recessive mutation causes a myeloproliferative syndrome. Second, retroviral insertions alter oncogenes or tumor suppressors, resulting in clonal expansion of leukemic cells. We have identified a recessive locus on chromosome 8 (Myls) that is responsible for myeloproliferation in BXH-2. This Myls interval has been narrowed down to 2 Mb and found to contain several positional candidates, including the interferon consensus sequence-binding protein 1 gene (Icsbp, also known as interferon regulatory factor 8 [IRF8]). We show that BXH-2 mice carry a mutation (915 C to T) resulting in an arginine-to-cysteine substitution at position 294 within the predicted IRF association domain of the protein. Although expression of Icsbp1 mRNA transcripts is normal in BXH-2 splenocytes, these cells are unable to produce interleukin 12 and interferon-gamma in response to activating stimuli, confirming that R294C behaves as a loss-of-function mutation. Myeloproliferation in BXH-2 mice is concomitant to increased susceptibility to Mycobacterium bovis (BCG) despite the presence of resistance alleles at the Nramp1 locus. These results suggest a two-step model for chronic myeloid leukemia in BXH-2, in which inactivation of Icsbp1 predisposes to myeloproliferation and immunodeficiency. This event is required for retroviral replication, and subsequent insertional mutagenesis that causes leukemia in BXH-2 mice.

FLT-3: a new focus in the understanding of acute leukemia

The FMS-like tyrosine kinase-3 (FLT-3), which belongs to the class III receptor tyrosine kinase family, is primarily expressed by hematopoietic cells and plays an important role in hematopoiesis. FLT-3 is also expressed in the majority of acute leukemias, in which the presence of FLT-3 activating mutations is associated with poor prognosis. Consequently, there has been a recent surge in the development of FLT-3 inhibitors for the molecular targeting of leukemia, and many of these are now in clinical trials. An improved understanding of how FLT-3 interacts with its ligand, as well as how FLT-3 activating mutations are able to trigger downstream intracellular signaling pathways, will provide greater insight to how small molecule inhibitors may best be utilized and combined with established chemotherapeutic drugs for the management of patients with high-risk acute leukemia.

KIT exon 8 mutations associated with core-binding factor (CBF)–acute myeloid leukemia (AML) cause hyperactivation of the receptor in response to stem cell factor

KIT exon 8 mutations are located in the extracellular portion of the receptor and are strongly associated with core-binding factor (CBF)-acute myeloid leukemia (AML). To characterize the functional role of these mutants, we analyzed the proproliferative and antiapoptotic potential of 3 KIT exon 8 mutations in interleukin 3 (IL-3)-dependent Ba/F3 cells. All KIT exon 8 mutants induced receptor hyperactivation in response to stem cell factor (SCF) stimulation in terms of proliferation and resistance toward apoptotic cell death. A representative KIT exon 8 mutant showed spontaneous receptor dimerization, phosphorylation of mitogen-activated protein kinase (MAPK), and conferred IL-3-independent growth to Ba/F3 cells. MAPK and phosphatidylinositol 3-kinase (PI3-kinase) activation was essential for the phenotype of this mutant. Additionally, imatinib inhibited proliferation of KIT exon 8 mutant-expressing Ba/F3 cells. Our data show that KIT exon 8 mutations represent gain-of-function mutations and might represent a new molecular target for treatment of CBF leukemias. (Blood. 2005;105:3319-3321)

Advances in childhood leukaemia: successful clinical-trials research leads to individualised therapy

In most cases, childhood leukaemia has a fetal origin, but multiple molecular events are required after birth for pre-leukaemic cells to progress to leukaemia. Cure rates for acute lymphoblastic leukaemia (ALL) now approach 80%. A high level of minimal residual disease detected by polymerase chain reaction in patients with ALL in remission has profound prognostic importance and is the focus of a major Australian study attempting to prevent relapse in these children. Greater awareness of the late effects of chemotherapy has led to changes in the treatment protocols for ALL, with improvement in neurocognitive outcomes and reduced rates of second malignancies. Pharmacogenetics is a new field of research that aims to enhance treatment efficacy by assessing the individual's metabolism of and response to chemotherapeutic agents. Targeted therapies currently being developed show some promise of being able to further improve cure rates. Adolescents with ALL have a better prognosis if treated with paediatric rather than adult protocols.

The role of CREB as a proto-oncogene in hematopoiesis and in acute myeloid leukemia

CREB is a transcription factor that functions in glucose homeostasis, growth factor-dependent cell survival, and memory. In this study, we describe a role of CREB in human cancer. CREB overexpression is associated with increased risk of relapse and decreased event-free survival. CREB levels are elevated in blast cells from patients with acute myeloid leukemia. To understand the role of CREB in leukemogenesis, we studied the biological consequences of CREB overexpression in primary human leukemia cells, leukemia cell lines, and transgenic mice. Our results demonstrate that CREB promotes abnormal proliferation and survival of myeloid cells in vitro and in vivo through upregulation of specific target genes. Thus, we report that CREB is implicated in myeloid cell transformation.

Plag1 and Plagl2 are oncogenes that induce acute myeloid leukemia in cooperation with Cbfb-MYH11

Recurrent chromosomal rearrangements are associated with the development of acute myeloid leukemia (AML). The frequent inversion of chromosome 16 creates the CBFB-MYH11 fusion gene that encodes the fusion protein CBFβ-SMMHC. This fusion protein inhibits the core-binding factor (CBF), resulting in a block of hematopoietic differentiation, and induces leukemia upon the acquisition of additional mutations. A recent genetic screen identified Plag1 and Plagl2 as CBFβ-SMMHC candidate cooperating proteins. In this study, we demonstrate that Plag1 and Plagl2 independently cooperate with CBFβ-SMMHC in vivo to efficiently trigger leukemia with short latency in the mouse. In addition, Plag1 and Plagl2 increased proliferation by inducing G1 to S transition that resulted in the expansion of hematopoietic progenitors and increased cell renewal in vitro. Finally, PLAG1 and PLAGL2 expression was increased in 20% of human AML samples. Interestingly, PLAGL2 was preferentially increased in samples with chromosome 16 inversion, suggesting that PLAG1 and PLAGL2 may also contribute to human AML. Overall, this study shows that Plag1 and Plagl2 are novel leukemia oncogenes that act by expanding hematopoietic progenitors expressing CbFβ-SMMHC.

Meis1 programs transcription of FLT3 and cancer stem cell character, using a mechanism that requires interaction with Pbx and a novel function of the Meis1 C-terminus

Meis1 is a homeodomain transcription factor coexpressed with Hoxa9 in most human acute myeloid leukemias (AMLs). In mouse models of leukemia produced by Hoxa9, Meis1 accelerates leukemogenesis. Because Hoxa9 immortalizes myeloid progenitors in the absence of Meis1 expression, the contribution of Meis1 toward leukemia remains unclear. Here, we describe a cultured progenitor model in which Meis1 programs leukemogenicity. Progenitors immortalized by Hoxa9 in culture are myeloid-lineage restricted and only infrequently caused leukemia after more than 250 days. Coexpressed Meis1 programmed rapid AML-initiating character, maintained multipotent progenitor potential, and induced expression of genes associated with short-term hematopoietic stem cells (HSCs), such as FLT3 and CD34, whose expression also characterizes the leukemia-initiating stem cells of human AML. Meis1 leukemogenesis functions required binding to Pbx, binding to DNA, and a conserved function of its C-terminal tail. We hypothesize that Meis1 is required for the homing and survival of leukemic progenitors within their hematopoietic niches, functions mediated by HSC-specific genes such as CD34 and Fms-like tyrosine kinase 3 (FLT3), respectively. This is the first example of a transcription factor oncoprotein (Meis1) that establishes expression of a tyrosine kinase oncoprotein (FLT3), and explains their coexpression in human leukemia. This cultured progenitor model will be useful to define the genetic basis of leukemogenesis involving Hoxa9 and Meis1.

Transplantable cell lines generated with NUP98–Hox fusion genes undergo leukemic progression by Meis1 independent of its binding to DNA

Hox genes have been identified in chromosomal translocations involving the nucleoporin gene NUP98. Though the resulting chimeric proteins directly participate in the development of leukemia, the long latency and monoclonal nature of the disease support the requirement for secondary mutation(s), such as those leading to overexpression of Meis1. Models to identify such events and to study leukemic progression are rare and labor intensive. Herein, we took advantage of the strong transforming potential of NUP98-HOXD13 or NUP98-HOXA10 to establish preleukemic myeloid lines from bone marrow cells that faithfully replicate the first step of Hox-induced leukemogenesis. These lines contain early granulomonocytic progenitors with extensive in vitro self-renewal capacity, short-term myeloid repopulating activity and low propensity for spontaneous leukemic conversion. We exploit such lines to show that Meis1 efficiently induces their leukemic progression and demonstrate a high frequency of preleukemic cells in the cultures. Furthermore, we document that the leukemogenic potential of Meis1 is independent of its direct binding to DNA and likely reflects its ability to increase the repopulating capacity of the preleukemic cells by increasing their self-renewal/proliferative capacity. The availability of lines with repopulating potential and capacity for leukemic conversion should open new avenues for understanding progression of Hox-mediated acute myeloid leukemia.

Using multiple anchor- and distribution-based estimates to evaluate clinically meaningful change on the Functional Assessment of Cancer Therapy-Biologic Response Modifiers (FACT-BRM) instrument

OBJECTIVE

The interpretation of health-related quality of life (HRQL) data from clinical trials can be enhanced by understanding the degree of change in HRQL scores that is considered meaningful. Our objectives were to combine distribution-based and two anchor-based approaches to identify minimally important differences (MIDs) for the 27-item Trial Outcome Index (TOI), the seven-item Social Well-Being (SWB) subscale, and the six-item Emotional Well-being (EWB) subscale from the Functional Assessment of Cancer Therapy-Biological Response Modifiers (FACT-BRM) instrument.

METHODS

Distribution-based MIDs were based on the standard error of measurement. Anchor-based approaches utilized patient-reported global rating of change (GRC) and change in physician-reported performance status rating (PSR). Correlations and weighted kappa statistics were used to assess association and agreement between the two anchors. FACT-BRM changes were evaluated for three time periods: baseline to month 1, month 2 to month 3, and month 5 to month 6.

RESULTS

Association between GRC and change in PSR was poor. Correlation between the anchors and HRQL change scores was largest at month 1 and decreased through month 6. Combining results from all approaches, the MIDs identified were 5-8 points for the TOI, 2 points for the SWB subscale, and 2-3 points for the EWB subscale.

CONCLUSIONS

We combined patient-reported estimates, physician-reported estimates, and distribution-based estimates to derive MIDs for HRQL outcomes from the FACT-BRM. These results will enable interpretation of treatment group effects in a clinical trial setting, and they can be used to estimate sample size or power when designing future studies.