Expression of MAC-1 (CD11b) in acute myeloid leukemia (AML) is associated with an unfavorable prognosis

Targeting integrins in drug-resistant acute myeloid leukaemia

Acute myeloid leukaemia (AML) continues to have a poor prognosis, warranting new therapeutic strategies. The bone marrow (BM) microenvironment consists of niches that interact with not only normal haematopoietic stem cells (HSC) but also leukaemia cells like AML. There are many adhesion molecules in the BM microenvironment; therein, integrins have been of central interest. AML cells express integrins that bind to ligands in the microenvironment, enabling adhesion of leukaemia cells in the microenvironment, thereby initiating intracellular signalling pathways that are associated with cell migration, cell proliferation, survival, and drug resistance that has been described to mediate cell adhesion-mediated drug resistance (CAM-DR). Identifying and targeting integrins in AML to interrupt interactions with the microenvironment have been pursued as a strategy to overcome CAM-DR. Here, we focus on the BM microenvironment and review the role of integrins in CAM-DR of AML and discuss integrin-targeting strategies. LINKED ARTICLES: This article is part of a themed issue on Cancer Microenvironment and Pharmacological Interventions. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.2/issuetoc.

Microenvironment in acute myeloid leukemia: focus on senescence mechanisms, therapeutic interactions, and future directions

Acute myeloid leukemia (AML) is a disease with a dismal prognosis, mainly affecting the elderly. In recent years, new drugs have improved life expectancy and quality of life, and a better understanding of the genetic-molecular nature of the disease has shed light on previously unknown aspects of leukemogenesis. In parallel, increasing attention has been attracted to the complex interactions between cells and soluble factors in the bone marrow (BM) environment, collectively known as the microenvironment. In this review, we discuss the central role of the microenvironment in physiologic and pathologic hematopoiesis and the mechanisms of senescence, considered a fundamental protective mechanism against the proliferation of damaged and pretumoral cells. The microenvironment also represents a fertile ground for the development of myeloid malignancies, and the leukemic niche significantly interacts with drugs commonly used in AML treatment. Finally, we focus on the role of the microenvironment in the engraftment and complications of allogeneic hematopoietic stem cell transplantation, the only curative option in a conspicuous proportion of patients.

HSP90 Inhibitor PU-H71 in Combination with BH3-Mimetics in the Treatment of Acute Myeloid Leukemia

Targeting the molecular chaperone HSP90 and the anti-apoptotic proteins MCL1 and BCL2 may be a promising novel approach in the treatment of acute myeloid leukemia (AML). The HSP90 inhibitor PU-H71, MCL1 inhibitor S63845, and BCL2 inhibitor venetoclax were assessed as single agents and in combination for their ability to induce apoptosis and cell death in leukemic cells. AML cells represented all major morphologic and molecular subtypes including FLT3-ITD and TP53 mutant AML cell lines and a variety of patient-derived AML cells. Results: PU-H71 and combination treatments with MCL1 inhibitor S63845 or BCL2 inhibitor venetoclax induced cell cycle arrest and apoptosis in susceptible AML cell lines and primary AML. The majority of the primary AML samples were responsive to PU-H71 in combination with BH3 mimetics. Elevated susceptibility to PU-H71 and S63845 was associated with FLT3 mutated AML with CD34 < 20%. Elevated susceptibility to PU-H71 and venetoclax was associated with primary AML with CD117 > 80% and CD11b < 45%. The combination of HSP90 inhibitor PU-H71 and MCL1 inhibitor S63845 may be a candidate treatment for FLT3-mutated AML with moderate CD34 positivity while the combination of HSP90 inhibitor PU-H71 and BCL2 inhibitor venetoclax may be more effective in the treatment of primitive AML with high CD117 and low CD11b positivity.

Dendritic Cell-Triggered Immune Activation Goes along with Provision of (Leukemia-Specific) Integrin Beta 7-Expressing Immune Cells and Improved Antileukemic Processes

Integrin beta 7 (β7), a subunit of the integrin receptor, is expressed on the surface of immune cells and mediates cell-cell adhesions and interactions, e.g., antitumor or autoimmune reactions. Here, we analyzed, whether the stimulation of immune cells by dendritic cells (of leukemic derivation in AML patients or of monocyte derivation in healthy donors) leads to increased/leukemia-specific β7 expression in immune cells after T-cell-enriched mixed lymphocyte culture-finally leading to improved antileukemic cytotoxicity. Healthy, as well as AML and MDS patients' whole blood (WB) was treated with Kit-M (granulocyte-macrophage colony-stimulating factor (GM-CSF) + prostaglandin E1 (PGE1)) or Kit-I (GM-CSF + Picibanil) in order to generate DCs (DC_leu or monocyte-derived DC), which were then used as stimulator cells in MLC. To quantify antigen/leukemia-specific/antileukemic functionality, a degranulation assay (DEG), an intracellular cytokine assay (INTCYT) and a cytotoxicity fluorolysis assay (CTX) were used. (Leukemia-specific) cell subtypes were quantified via flow cytometry. The Kit treatment of WB (compared to the control) resulted in the generation of DC/DC_leu, which induced increased activation of innate and adaptive cells after MLC. Kit-pretreated WB (vs. the control) led to significantly increased frequencies of β7-expressing T-cells, degranulating and intracellular cytokine-producing β7-expressing immune cells and, in patients' samples, increased blast lysis. Positive correlations were found between the Kit-M-mediated improvement of blast lysis (vs. the control) and frequencies of β7-expressing T-cells. Our findings indicate that DC-based immune therapies might be able to specifically activate the immune system against blasts going along with increased frequencies of (leukemia-specific) β7-expressing immune cells. Furthermore, β7 might qualify as a predictor for the efficiency and the success of AML and/or MDS therapies.

Extramedullary Myeloid Leukemia in the Setting of a Myeloproliferative Neoplasm

Extramedullary acute myeloid leukemia (EML), also known as myeloid sarcoma (MS), is an extramedullary solid mass derived from the proliferation of myeloblasts outside of the bone marrow. EML can present independently or concurrently with intramedullary acute myeloid leukemia (iAML). It can happen de novo or secondary to iAML, myeloproliferative neoplasm (MPN), chronic myelomonocytic leukemia (CMML), or myelodysplastic syndrome (MDS). We present a 57-year-old female with a history of Janus kinase 2 (JAK-2)-positive essential thrombocythemia (ET) evolving into EML in the setting of a persistent TP53 mutation. We discuss the essential diagnostic studies including tissue biopsy and fluorodeoxyglucose positron emission tomography/computed tomography (F-FDG PET/CT) imaging. We also investigate the significance of cytogenetics and next-generation sequencing (NGS) along with the unique pathogenesis, treatment and prognostic implications.

Target Therapy for Extramedullary Relapse of FLT3-ITD Acute Myeloid Leukemia: Emerging Data from the Field

FMS-like tyrosine kinase 3 (FLT3) is a receptor tyrosine kinase family member. Mutations in FLT3, as well known, represent the most common genomic alteration in acute myeloid leukemia (AML), identified in approximately one-third of newly diagnosed adult patients. In recent years, this has represented an important therapeutic target. Drugs such as midostaurin, gilteritinib, and sorafenib, either alone in association with conventional chemotherapy, play a pivotal role in AML therapy with the mutated FLT3 gene. A current challenge lies in treating forms of AML with extramedullary localization. Here, we describe the general features of myeloid sarcoma and the ability of a targeted drug, i.e., gilteritinib, approved for relapsed or refractory disease, to induce remission of these extramedullary leukemic localizations in AML patients with FLT3 mutation, analyzing how in the literature, there is an important development of cases describing this promising potential for care.

Adhesion Molecules Involved in Stem Cell Niche Retention During Normal Haematopoiesis and in Acute Myeloid Leukaemia

In the bone marrow (BM) of adult mammals, haematopoietic stem cells (HSCs) are retained in micro-anatomical structures by adhesion molecules that regulate HSC quiescence, proliferation and commitment. During decades, researchers have used engraftment to study the function of adhesion molecules in HSC's homeostasis regulation. Since the 90's, progress in genetically engineered mouse models has allowed a better understanding of adhesion molecules involved in HSCs regulation by BM niches and raised questions about the role of adhesion mechanisms in conferring drug resistance to cancer cells nested in the BM. This has been especially studied in acute myeloid leukaemia (AML) which was the first disease in which the concept of cancer stem cell (CSC) or leukemic stem cells (LSCs) was demonstrated. In AML, it has been proposed that LSCs propagate the disease and are able to replenish the leukemic bulk after complete remission suggesting that LSC may be endowed with drug resistance properties. However, whether such properties are due to extrinsic or intrinsic molecular mechanisms, fully or partially supported by molecular crosstalk between LSCs and surrounding BM micro-environment is still matter of debate. In this review, we focus on adhesion molecules that have been involved in HSCs or LSCs anchoring to BM niches and discuss if inhibition of such mechanism may represent new therapeutic avenues to eradicate LSCs.

Identification and validation of inferior prognostic genes associated with immune signatures and chemotherapy outcome in acute myeloid leukemia

Acute myeloid leukemia (AML) is a group of heterogeneous hematological malignancies. We identified key genes as ITGAM and lncRNA ITGB2-AS1 through different bioinformatics tools. Furthermore, qPCR was performed to verify the expression level of essential genes in clinical samples. Retrospective research on 179 AML cases was used to investigate the relationship between the expression of ITGAM and the characteristics of AML. The critical gene relationship with immune infiltration in AML was estimated. The clinical validation and prognostic investigation showed that ITGAM, PPBP, and ITGB2-AS1 are highly expressed in AML (P < 0.001) and significantly associated with the overall survival in AML. Moreover, the retrospective research on 179 clinical cases showed that positive expression of ITGAM is substantially related to AML classification (P < 0.001), higher count of white blood cells (P < 0.01), and poor chemotherapy outcome (P < 0.05). Furthermore, based on grouping ITGAM as the high and low expression in TCGA-LAML profile, we found that genes in the highly expressed ITGAM group are mainly involved in immune infiltration and inflammation-related signaling pathways. Finally, we discovered that the expression level of ITGAM and lncRNA ITGB2-AS1 are not just closely related to the immune score and stromal score (P < 0.001) but also significantly positively correlated with various Immune signatures in AML (P < 0.001), indicating the association of these genes with immunosuppression in AML. The prediction of candidate drugs indicated that certain immunosuppressive drugs have potential therapeutic effects for AML. The critical genes could be used as potential biomarkers to evaluate the survival and prognosis of AML.

The Promiscuous Profile of Complement Receptor 3 in Ligand Binding, Immune Modulation, and Pathophysiology

The β2-integrin receptor family has a broad spectrum of physiological functions ranging from leukocyte adhesion, cell migration, activation, and communication to the phagocytic uptake of cells and particles. Among the members of this family, complement receptor 3 (CR3; CD11b/CD18, Mac-1, αMβ2) is particularly promiscuous in its functional profile and ligand selectivity. There are close to 100 reported structurally unrelated ligands for CR3, and while many ligands appear to cluster at the αMI domain, molecular details about binding modes remain largely elusive. The versatility of CR3 is reflected in its functional portfolio, which includes prominent roles in the removal of invaders and cell debris, induction of tolerance and synaptic pruning, and involvement in the pathogenesis of numerous autoimmune and chronic inflammatory pathologies. While CR3 is an interesting therapeutic target for immune modulation due to these known pathophysiological associations, drug development efforts are limited by concerns of potential interference with host defense functions and, most importantly, an insufficient molecular understanding of the interplay between ligand binding and functional impact. Here, we provide a systematic summary of the various interaction partners of CR3 with a focus on binding mechanisms and functional implications. We also discuss the roles of CR3 as an immune receptor in health and disease, as an activation marker in research and diagnostics, and as a therapeutic target.

A narrative review of central nervous system involvement in acute leukemias

Acute leukemias (both myeloid and lymphoblastic) are a group of diseases for which each year more successful therapies are implemented. However, in a subset of cases the overall survival (OS) is still exceptionally low due to the infiltration of leukemic cells in the central nervous system (CNS) and the subsequent formation of brain tumors. The CNS involvement is more common in acute lymphocytic leukemia (ALL), than in adult acute myeloid leukemia (AML), although the rates for the second case might be underestimated. The main reasons for CNS invasion are related to the expression of specific adhesion molecules (VLA-4, ICAM-1, VCAM, L-selectin, PECAM-1, CD18, LFA-1, CD58, CD44, CXCL12) by a subpopulation of leukemic cells, called “sticky cells” which have the ability to interact and adhere to endothelial cells. Moreover, the microenvironment becomes hypoxic and together with secretion of VEGF-A by ALL or AML cells the permeability of vasculature in the bone marrow increases, coupled with the disruption of blood brain barrier. There is a single subpopulation of leukemia cells, called leukemia stem cells (LSCs) that is able to resist in the new microenvironment due to its high adaptability. The LCSs enter into the arachnoid, migrate, and intensively proliferate in cerebrospinal fluid (CSF) and consequently infiltrate perivascular spaces and brain parenchyma. Moreover, the CNS is an immune privileged site that also protects leukemic cells from chemotherapy. CD56/NCAM is the most important surface molecule often overexpressed by leukemic stem cells that offers them the ability to infiltrate in the CNS. Although asymptomatic or with unspecific symptoms, CNS leukemia should be assessed in both AML/ALL patients, through a combination of flow cytometry and cytological analysis of CSF. Intrathecal therapy (ITT) is a preventive measure for CNS involvement in AML and ALL, still much research is needed in finding the appropriate target that would dramatically lower CNS involvement in acute leukemia.

Cadherins, Selectins, and Integrins in CAM-DR in Leukemia

The interaction between leukemia cells and the bone microenvironment is known to provide drug resistance in leukemia cells. This phenomenon, called cell adhesion-mediated drug resistance (CAM-DR), has been demonstrated in many subsets of leukemia including B- and T-acute lymphoblastic leukemia (B- and T-ALL) and acute myeloid leukemia (AML). Cell adhesion molecules (CAMs) are surface molecules that allow cell-cell or cell-extracellular matrix (ECM) adhesion. CAMs not only recognize ligands for binding but also initiate the intracellular signaling pathways that are associated with cell proliferation, survival, and drug resistance upon binding to their ligands. Cadherins, selectins, and integrins are well-known cell adhesion molecules that allow binding to neighboring cells, ECM proteins, and soluble factors. The expression of cadherin, selectin, and integrin correlates with the increased drug resistance of leukemia cells. This paper will review the role of cadherins, selectins, and integrins in CAM-DR and the results of clinical trials targeting these molecules.

Myeloid sarcoma, chloroma, or extramedullary acute myeloid leukemia tumor: A tale of misnomers, controversy and the unresolved

The World Health Organization classification and definition of "myeloid sarcoma" is imprecise and misleading. A more accurate term is "extramedullary acute myeloid leukemia tumor (eAML)." The pathogenesis of eAML has been associated with aberrancy of cellular adhesion molecules, chemokine receptors/ligands and RAS-MAPK/ERK signaling. eAML can present with or without synchronous or metachronous intramedullary acute myeloid leukemia (AML) so a bone marrow evaluation is always recommended. Accurate diagnosis of eAML requires tissue biopsy. eAML confined to one or a few sites is frequently treated with local therapy such as radiotherapy. About 75-90% of patients with isolated eAML will develop metachronous intramedullary AML with a median latency period ranging from 4 to 12 months; thus, patients with isolated eAML may also be treated with systemic anti-leukemia therapy. eAML does not appear to have an independent prognostic impact; selection of post-remission therapy including allogeneic hematopoietic cell transplant (alloHCT) is typically guided by intramedullary disease risk. Management of isolated eAML should be individualized based on patient characteristics as well as eAML location and cytogenetic/molecular features. The role of PET/CT in eAML is also currently being elucidated. Improving outcomes of patients with eAML requires further knowledge of its etiology and mechanism(s) as well as therapeutic approaches beyond conventional chemotherapy, ideally in the context of controlled trials.

Potential of immunotherapies in the mediation of antileukemic responses for patients with acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) - With a focus on Dendritic cells of leukemic origin (DCleu)

New (non-immunotherapeutic) treatment-strategies for AML/MDS-patients are under development. Dendritic cells (DCs) and 'leukemia-derived DC' (DC_leu) connect the innate and the adaptive immunesystem and (re-)activate it, in their capacity as professional antigen-presenting cells (APCs). They can be generated ex vivo from peripheral blood mononuclear cells (PBMNCs) or whole blood (WB), containing the -physiological-cellular/soluble microenvironment of individual patients using various DC/DC_leu-generating methods or (for WB) minimalized 'Kits', containing granulocyte-macrophage-colony-stimulating-factor (GM-CSF) and a second response-modifier. Proof for DC/DC_leu-mediated activation of the immune-system after T-cell-enriched mixed lymphocyte culture (MLC) is done by flowcytometry, demonstrating increased fractions of certain activated, leukemia-specific or antileukemic cell-subsets of the innate and the adaptive immune-system. Generation of DC/DC_leu is possible independent of patients' age, MHC-, mutation- or transplantation-status. In vivo-treatment of AML-/MDS-patients with blast-modulating, DC/DC_leu- inducing 'Kits' could contribute to create migratory DCs, as well as antileukemically reactivated and memory-mediating immune-cells, which patrol tissue and blood and could contribute to stabilizing disease or remissions.

Myeloid maturation potentiates STAT3-mediated atypical IFN-γ signaling and upregulation of PD-1 ligands in AML and MDS

Interferon (IFN)-γ is the major mediator of anti-tumor immune responses; nevertheless, cancer cells use intrigue strategies to alter IFN-γ signaling and avoid elimination. Understanding the immune regulatory mechanisms employed by acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) cells upon exposure to IFN-γ is critical for development of immunotherapy and checkpoint blockade therapy approaches. This study aims to explore the influence of myeloid maturation on IFN-γ-induced PD-L1 and PD-L2 expression and on pro-leukemogenic transcription factor STAT3 signaling in AML and MDS. Stimulation of myeloid blasts’ maturation by all-trans retinoic acid (ATRA) or 1α,25-dihydroxyvitamin D3 (vitamin D) increased the CD11b⁺ fraction that expressed PD-1 ligands in response to IFN-γ. Intriguingly, STAT3 pathway was potently induced by IFN-γ and strengthened upon prolonged exposure. Nonetheless, STAT3-mediated atypical IFN-γ signaling appeared as a negligible factor for PD-L1 and PD-L2 expression. These negative influences of IFN-γ could be alleviated by a small-molecule inhibitor of STAT3, stattic, which also inhibited the upregulation of PD-L1. In conclusion, induction of myeloid maturation enhances the responsiveness of AML and MDS cells to IFN-γ. However, these malignant myeloid cells can exploit both STAT3 pathway and PD-1 ligands to survive IFN-γ-mediated immunity and maintain secondary immune resistance.

Adverse outcome of AML with aberrant CD16 and CD56 NK cell marker expression

Natural killer cells mediate antibody-dependent cell-mediated cytotoxicity, and CD16 exerts key functions to induce antibody-dependent cell-mediated cytotoxicity response. Because the prognostic relevance of aberrant CD16 expression in AML patients at diagnosis is unknown, we analyzed 325 AML patients undergoing intensive chemotherapy for aberrant CD16+ and CD56+ natural killer-cell marker expression. CD56+ AML patients had inferior median event-free (EFS; P = 0.0699) and overall survival (OS; 10.9 versus 20.6 months; P = 0.0132). Patients expressing CD16 had worse median EFS (P = 0.0622) and OS (13.0 versus 45.9 months; P = 0.0277). EFS for CD16+/CD56+ patients was 5.7 months compared with 7.1 months for CD16-/CD56- (P = 0.3690), and OS was 10.6 months for CD16+/CD56+ patients compared with 52.2 months for CD16-/CD56- patients (P = 0.0311). Patients with CD16+/CD56+ expression had a lower probability to achieve complete remission after 2 induction cycles (52% versus 72%). Our data suggest that AML patients with aberrant CD16 and CD56 expression have adverse survival outcomes.

Beclin-1 and hypoxia-inducible factor-1α genes expression: Potential biomarkers in acute leukemia patients

BACKGROUND

Beclin-1, an important autophagic gene, and hypoxia-inducible factor-1α (HIF-1α), the master regulator of the hypoxic response, are reported in several human cancers. However, their expressions in acute leukemia haven't yet been well investigated.

OBJECTIVE

This study was designed to investigate the gene expression of beclin-1, microtubule-associated protein-1 light chain-3B (MAB1LC3B), the anti-apoptotic marker Bcl-2, and HIF-1α, as well as to evaluate the relationship between their expressions profile and prognosis in acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL) adult patients.

METHODS

The study involved 30 AML patients, 25 ALL patients, and 20 controls. Gene expression was analyzed using quantitative reverse transcriptase polymerase chain reaction (QRT-PCR).

RESULTS

In both AML and ALL groups, beclin-1 and MAB1LC3B expressions were significantly down-regulated (p < 0.001), while HIF-1α (p < 0.01) and Bcl-2 (p < 0.001) expressions were significantly up-regulated compared to the control group. HIF-1α fold expression was significantly negatively correlated with beclin-1 (p < 0.01). Moreover, decreased beclin-1 gene expression and increased HIF-1α gene expression were both associated with poor survival, supporting their pivotal role in the development and progression of acute leukemia.

CONCLUSIONS

Both Beclin-1 and HIF-1α could be considered as important biomarkers determinants of pathogenesis and survival in acute leukemia.

Correlation of CD11b and CD56 expression in adult acute myeloid leukemia with cytogenetic risk groups and prognosis

Among other phenotypic markers, CD11b expression has been considered as an unfavorable prognostic factor, both in terms of overall survival (OS), disease-free survival (DFS), and attainment and duration of complete remissions (CRs) in adult patients with acute myeloid leukemia (AML). Recently, some groups have restricted its prognostic impact to poor prognostic karyotypic risk groups. The aim of this study was to retrospectively analyze the prevalence of CD11b and of CD56 expression in blast cells of 158 AML patients [excluding those with t(15;17)] stratified according to their cytogenetic risk and to correlate these phenotypic characteristics with OS, DFS, and CR. CD11b was more frequently expressed in intermediate and unfavorable cytogenetic prognostic groups (38.9 and 35.5 %, respectively) than in the favorable group (9.5 %). No differences were observed in CD56 expression according to the cytogenetic risk groups. When OS, DFS, and CR were analyzed according to these two markers, no statistical differences were recorded in any cytogenetic risk group. In conclusion, although CD11b was more frequently expressed in blast cells of patients with intermediate and unfavorable cytogenetic risk groups, this feature did not translate into different clinical outcome. Similarly, CD56 positivity did not have any influence on the prognosis of these patients.

β2 integrin-derived signals induce cell survival and proliferation of AML blasts by activating a Syk/STAT signaling axis

Spleen tyrosine kinase (Syk) induces cell survival and proliferation in a high proportion of acute myeloid leukemia (AML) blasts, but the underlying molecular events of Syk signaling have not been investigated. Proteomic techniques have allowed us to identify the multiprotein complex that is nucleated by constitutively active Syk in AML cells. This complex differs from the B-lymphoid Syk interactome with respect to several proteins, especially the integrin receptor Mac-1, the Fc-γ receptor I (FcγRI), and the transcription factors STAT3 and STAT5. We show in several AML cell line models that tonic signals derived from the Fc-γ chain lead to Syk-dependent activation of STAT3 and STAT5, which in turn induces cell survival and proliferation. Moreover, stimulation of Mac-1 or FcγRI intensifies the constitutive Syk-mediated STAT3/5 activation in AML cells, a scenario likely to take place in the bone marrow niche. In accordance with these findings, we observed that β2 integrins, including Mac-1, trigger proliferation of AML cells in an AML cell/stroma coculture model. Taken together, we identified an oncogenic integrin/Syk/STAT3/5 signaling axis that might serve as a therapeutic target of AML in the future.

CD11b expression correlates with monosomal karyotype and predicts an extremely poor prognosis in cytogenetically unfavorable acute myeloid leukemia

Several cytogenetic features, including monosomal karyotype (MK), have been associated with unfavorable prognosis in acute myeloid leukemia (AML). However, little is known about the prognostic significance of immunophenotypes in AML patients with unfavorable-risk cytogenetics. We evaluated immunophenotypes, cytogenetics, clinical features and survival outcomes in 233 uniformly treated AML patients who harbored unfavorable cytogenetics. CD11b expression was observed in 145 (70%) of 208 patients and emerged as an independent prognostic factor for inferior overall survival in multivariate analysis (p=0.024). MK and age ≥ 60 years were predictors for lower complete remission rate (p=0.017, p<0.0001, respectively) and shorter overall survival (p=0.024, p<0.0001), while complex karyotype (CK) predicted a shorter overall survival (p=0.013). CD11b expression was strongly correlated with MK and identified a subset of patients with MK who had extremely poor overall survival. We proposed a prognostic scoring model using CD11b positivity, age ≥ 60 years, the presence of MK and the presence of CK to classify the patients into distinct risk groups. We identified the poor prognosis of CD11b expression and validated the adverse influence of MK, CK and age ≥ 60 years in cytogenetically unfavorable AML patients. Our proposed scoring model may be adapted in clinical practice to further the stratification of this high-risk population.

Expression of inhibitor of apoptosis protein (IAP) livin/BIRC7 in acute leukemia in adults: correlation with prognostic factors and outcome

The clinical relevance of livin/BIRC7 expression is still controversial in different types of malignancies, therefore this study was designed to evaluate the gene expression of livin in Egyptian adult AML and ALL. Livin expression level was higher in patients with unfavorable prognostic factors at diagnosis in both ALL (p=0.002) and AML (p=0.042) and its level was negatively correlated with event free survival (EFS) and overall survival (OS) in both ALL (p<0.001for both) and AML (p=0.001 and 0.023 respectively). This study suggests that livin expression is a novel prognostic marker in adult acute leukemia and thus needs to be incorporated into the patient stratification and treatment protocols.

Bone marrow aspirate and biopsy: a pathologist's perspective. II. interpretation of the bone marrow aspirate and biopsy

Bone marrow examination has become increasingly important for the diagnosis and treatment of hematologic and other illnesses. Morphologic evaluation of the bone marrow aspirate and biopsy has recently been supplemented by increasingly sophisticated ancillary assays, including immunocytochemistry, cytogenetic analysis, flow cytometry, and molecular assays. With our rapidly expanding knowledge of the clinical and biologic diversity of leukemia and other hematologic neoplasms, and an increasing variety of therapeutic options, the bone marrow examination has became more critical for therapeutic monitoring and planning optimal therapy. Sensitive molecular techniques, in vitro drug sensitivity testing, and a number of other special assays are available to provide valuable data to assist these endeavors. Fortunately, improvements in bone marrow aspirate and needle technology has made the procurement of adequate specimens more reliable and efficient, while the use of conscious sedation has improved patient comfort. The procurement of bone marrow specimens was reviewed in the first part of this series. This paper specifically addresses the diagnostic interpretation of bone marrow specimens and the use of ancillary techniques.

Environment-mediated drug resistance: a major contributor to minimal residual disease

Environment-mediated drug resistance is a form of de novo drug resistance that protects tumour cells from the initial effects of diverse therapies. Surviving foci of residual disease can then develop complex and permanent acquired resistance in response to the selective pressure of therapy. Recent evidence indicates that environment-mediated drug resistance arises from an adaptive, reciprocal signalling dialogue between tumour cells and the surrounding microenvironment. We propose that new therapeutic strategies targeting this interaction should be applied during initial treatment to prevent the emergence of acquired resistance.

MN1 affects expression of genes involved in hematopoiesis and can enhance as well as inhibit RAR/RXR-induced gene expression

The oncoprotein meningioma 1 (MN1) is overexpressed in several subtypes of acute myeloid leukemia (AML) and overexpression was associated with a poor response to chemotherapy. MN1 is a cofactor of retinoic acid receptor/retinoic x receptor (RAR/RXR)-mediated transcription and this study identified genes in the promonocytic cell line U937 that were regulated by MN1. We found that MN1 can both stimulate and inhibit transcription. Combining MN1 expression with all-trans retinoic acid (ATRA), the ligand of the RAR/RXR dimer, showed that MN1 could both enhance and repress ATRA effects. Many of the identified genes are key players in hematopoiesis and leukemogenesis (e.g. MEIS1 and BMI1). Another interesting target is DHRS9. DHRS9 is involved in the synthesis of ATRA from vitamin A. MN1 inhibited DHRS9 expression and completely abolished its induction by ATRA. MN1 is also the target of a rare AML-causing translocation encoding the MN1-TEL protein. MN1-TEL induces expression of only a few genes and its most pronounced effect is inhibition of a large group of ATRA-induced genes including DHRS9. In conclusion, both MN1 and MN1-TEL interfere with the ATRA pathway and this might explain the differentiation block in leukemias in which these genes are involved.