The molecular signature of oncofusion proteins in acute myeloid leukemia

Acute myeloid leukemia (AML) associated translocations often cause gene fusions that encode oncofusion proteins. Although many of the breakpoints involved in chromosomal translocations have been cloned, in most cases the role of the chimeric proteins in tumorigenesis is not elucidated. Here we will discuss the fusion proteins of the 4 most common translocations associated with AML as well as the common molecular mechanisms that these four and other fusion proteins utilize to transform progenitor cells. Intriguingly, although the individual partners within the fusion proteins represent a wide variety of cellular functions, at the molecular level many commodities can be found.     

RACK1 promotes the proliferation of THP1 acute myeloid leukemia cells

The receptor for activated C kinase 1 (RACK1), an adaptor protein implicated in the regulation of multiple signaling pathways, has been reported to contribute to the survival of leukemic progenitor cells by enhancing the activity of glycogen synthase kinase 3β (GSK3β). However, it remains unknown whether RACK1 also contributes to the oncogenic growth of acute myeloid leukemia (AML) cells. Here, we report that transient or stable silencing of endogenous RACK1 expression by RACK1 short hairpin RNAs (shRNAs) led to impaired proliferation of THP1 AML cells without inducing terminal differentiation. Further exploration revealed that RACK1 loss-of-function resulted in reduced GSK3β activity. GSK3β shRNA treatment showed similar effects to RACK1 loss-of-function. Our data collectively suggest that RACK1 contributes to THP1 cell proliferation through, at least partially, enhancing GSK3β activity. Thus, targeting RACK1 may have some important therapeutic implications in the treatment of AML.     

The frequency of NPM1 mutations in childhood acute myeloid leukemia

Leser-Trélat syndrome is characterized by the eruptive appearance of multiple seborrheic keratoses in association with underlying malignant disease. Usually, the sign of Leser-Trélat is associated with adenocarcinoma, most frequently of the colon, breast, or stomach, but also of the lung, kidney, liver, and pancreas. Herein, we present a case that we believe is the first report of the sign of Leser-Trélat in association with occult gastric adenocarcinoma and the anamnestic oncologic history of five other multiple primitive cancers. Epidermal growth factor receptor (EGFR) immunohistochemical expression analysis of multiple seborrheic keratoses revealed an intense membranous staining in the basal keratinocytes and in all the upper epidermal layers. Patients with the sign of Leser-Trélat should undergo a diagnostic screening programme for malignant disease along with patients with known Leser-Trélat syndrome who present with a recent acute and florid eruption of their seborrheic keratoses. We propose the importance of combining the molecular features of multiple seborrheic keratoses with EGFR immunohistochemistry analyses to determine the likelihood of Leser-Trélat syndrome and the consequent high risk of underlying multiple visceral malignancies.     

Annular promyelocytes in acute myeloid leukemia

Granulocytes with ring-shaped nuclei (annular granulocytes; ring granulocytes) are normal bone marrow constituents in rodents. Studies in man have shown a small number of these cells in cases of myeloproliferative diseases. Myelocytes and metamyelocytes have also been described. Similar to rodents and some other animal species, the annular promyelocyte also exists in humans. The significance of these very rare cells in human haemopoiesis becomes an interesting question.     

Interleukin-17 in acute myeloid leukemia

There are several reports that angiogenesis plays important roles in hematological malignancies including acute myeloid leukemia (AML). Human interleukin-17 (IL-17) is a proinflammatory cytokine produced by activated CD4 T cells. IL-17 plays a potential role in T cell mediated angiogenesis. The role of IL-17 in pathologic angiogenesis has not been evaluated yet. The aim of the study was to determine plasma level of IL-17 in patients with AML. IL-17 levels were measured by ELISA in plasma samples taken from 68 adult patients with AML before chemotherapy was administered. In addition 20 out of 68 patients were reanalysed after achieving complete remission (CR). Ten samples from healthy volunteers were evaluated as the control. In this study we have demonstrated that serum level of IL-17 is not elevated in AML patients. These results suggest that angiogenesis in AML is not mediated by CD4 T cells. To our knowledge this is the first report about IL-17 serum level in acute leukemias. We are currently evaluating IL-17 levels in others haematological malignancies.     

Modifying the biological response in acute myeloid leukemia

Summary Lymphocyte response to mitogens and to lymphocyte suppressor and monocyte helper activity was studied in 18 patients with acute myeloid leukemia in complete remission, and in 17 healthy controls. Ten patients were maintained with chemotherapy alone (CT), and eight received chemoimmunotherapy with BCG + leukemic cells (CIT).In late remission the mitogen responsiveness was increased in CT patients and decreased in CIT patients.No significant difference in lymphocyte suppressor activity could be demonstrated between patients and controls, or between CT and CIT.When autologous CIT monocytes were added to mitogen-stimulated lymphocytes they acted as helper cells. CT monocytes, in contrast, seemed to act as suppressor cells. Control monocytes also acted as helper cells, but to a significantly lesser degree than CIT monocytes.Fellow, Hospital Universitario de Caracas, Division of Hematology, Universidad Central de Venezuela, Caracas, VenezuelaCentral Microbiological Laboratory of Stockholm Country CouncilAnna Villa Rusconi fellow, Department of Internal Medicine, University of Ferrara, Italy     

Genetic profile of acute myeloid leukemia

Understanding genomic events and the cascade of their effects in cell function is crucial for identifying distinct subsets of acute myeloid leukemia and developing new therapeutic strategies. Conventional cytogenetics, fluorescence in situ hybridization investigations and molecular studies have provided much information over the past few years. This review will focus on major genomic mechanisms in acute myeloid luekemia and on the genes implicated in the pathogenesis of specific subtypes.     

Antiapoptotic microenvironment of acute myeloid leukemia

We showed previously that tumor-derived supernatant (TSN) from acute myeloid leukemia (AML) myeloblasts inhibits peripheral blood T cell activation and proliferation, rendering the T cells functionally incompetent. We show here that the AML TSN also significantly delays apoptosis of both resting and stimulated T cells, as judged by reduction in annexin V/propidium iodide staining. In addition, we show that this is not unique to T cells and that AML TSN inhibits apoptosis of peripheral B cells, neutrophils, and monocytes. Furthermore, it also enhances the survival of other AML myeloblasts with lower viability. Investigations into the mechanism demonstrate a reduction in the cleavage of procaspase-3, -8, and -9 and the caspase substrate, poly(ADP-ribose)polymerase (PARP). This may be due to Bcl-2, which is normally down-regulated in CD3/CD28-stimulated T cells, but is maintained in the presence of AML TSN. We conclude that AML cells generate an antiapoptotic microenvironment that favors the survival of malignant cells, but also inhibits apoptosis of other normal hemopoietic cells. Reversal of these immunosuppressive effects and restoration of normal immune responses in patients with AML would improve the success of immunotherapy protocols.     

FLT3 inhibitors in acute myeloid leukemia

FLT3 mutations are one of the most common findings in acute myeloid leukemia (AML). FLT3 inhibitors have been in active clinical development. Midostaurin as the first-in-class FLT3 inhibitor has been approved for treatment of patients with FLT3-mutated AML. In this review, we summarized the preclinical and clinical studies on new FLT3 inhibitors, including sorafenib, lestaurtinib, sunitinib, tandutinib, quizartinib, midostaurin, gilteritinib, crenolanib, cabozantinib, Sel24-B489, G-749, AMG 925, TTT-3002, and FF-10101. New generation FLT3 inhibitors and combination therapies may overcome resistance to first-generation agents.     

Dendritic cell vaccination in acute myeloid leukemia

The prognosis of patients with acute myeloid leukemia (AML) remains dismal, with a 5-year overall survival rate of only 5.2% for the continuously growing subgroup of AML patients older than 65 years. These patients are generally not considered eligible for intensive chemotherapy and/or allogeneic hematopoietic stem cell transplantation because of high treatment-related morbidity and mortality, emphasizing the need for novel, less toxic, treatment alternatives. It is within this context that immunotherapy has gained attention in recent years. In this review, we focus on the use of dendritic cell (DC) vaccines for immunotherapy of AML. DC are central orchestrators of the immune system, bridging innate and adaptive immunity and critical to the induction of anti-leukemic immunity. We discuss the rationale and basic principles of DC-based therapy for AML and review the clinical experience that has been obtained so far with this form of immunotherapy for patients with AML.     

Type C mutation of nucleophosmin 1 acute myeloid leukemia: Consequences of intrinsic disorder

BackgroundNucleophosmin 1 (NPM1) protein is a multifunctional nucleolar chaperone and its gene is the most frequently mutated in Acute Myeloid Leukemia (AML). AML mutations cause the unfolding of the C-terminal domain (CTD) and the protein delocalizing in the cytosol (NPM1c+). Marked aggregation endowed with an amyloid character was assessed as consequences of mutations.ScopeHerein we analyzed the effects of type C mutation on two protein regions: i) a N-terminal extended version of the CTD, named Cterm_mutC and ii) a shorter polypeptide including the sequences of the second and third helices of the CTD, named H2_mutC.Major conclusionsBoth demonstrated able to self-assembly with different kinetics and conformational intermediates and to provide fibers presenting large flexible regions.General significanceThe present study adds a new piece of knowledge to the effects of AML-mutations on structural biology of Nucleophosmin 1, that could be exploited in therapeutic interventions targeting selectively NPMc+.     

Identification of Annexin A1 interacting proteins in chronic myeloid leukemia KCL22 cells

In the present study, we used a functional proteomic approach to identify Annexin A1 (Anxa1) interacting proteins in the Philadelphia‐positive KCL22 cell line. We focused on Anxa1 because it is one of the major proteins upregulated in imatinib‐sensitive KCL22S cells versus imatinib‐resistant KCL22R. Our proteomic strategy revealed 21 interactors. Bioinformatic analysis showed that most of these proteins are involved in cell death processes. Among the proteins identified, we studied the interaction of Anxa1 with two phosphatases, Shp1 and Shp2, which were recently identified as biomarkers of imatinib sensitivity in patients affected by chronic myeloid leukemia. Our data open new perspectives in the search for annexin‐mediated signaling pathways and may shed light on mechanisms of resistance to imatinib that are unrelated to Bcr‐Abl activity. All mass spectrometry data have been deposited in the ProteomeXchange with identifier PXD000030.     

The evolving landscape in the therapy of acute myeloid leukemia

Acute myeloid leukemia (AML) is a heterogeneous clonal disorder of myeloid precursors arrested in their maturation, creating a diverse disease entity with a wide range of responses to historically standard treatment approaches. While signifi cant progress has been made in characterizing and individualizing the disease at diagnosis to optimally inform those affected, progress in treatment to reduce relapse and induce remission has been limited thus far. In addition to a brief summary of the factors that shape prognostication at diagnosis, this review attempts to expand on the current therapies under investigation that have shown promise in treating AML, including hypomethylating agents, gemtuzumab ozogamicin, FLT3 tyrosine kinase inhibitors, antisense oligonucleotides, and other novel therapies, including aurora kinases, mTOR and PI3 kinase inhibitors, PIM kinase inhibitors, HDAC inhibitors, and IDH targeted therapies. With these, and undoubtedly many others in the future, it is the hope that by combining more accurate prognostication with more effective therapies, patients will begin to have a different, and more complete, outlook on their disease that allows for safer and more successful treatment strategies.