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PubMed1993

Clinical aspects of acute myeloid leukemias of the FAB types M3 and M4Eo. The AML Cooperative Group.

Acute promyelocytic leukemia (AML FAB M3, APL) and acute myelomonocytic leukemia with abnormal eosinophils (AML M4Eo) are considered distinct entities with characteristic clinical, morphological, cytogenetic, and prognostic features. Promyelocytic leukemia is characterized by abnormal promyelocytes replacing normal hematopoiesis associated with a translocation between the long arms of chromosomes 15 and 17 t (15; 17), severe coagulopathy, and responsiveness to all-trans retinoic acid (tretinoin). Characteristic features of AML M4Eo are a myelomonocytic marrow infiltration, eosinophils with abnormal immature granules positive for chloroacetate esterase, an inversion or translocation of chromosome 16, and an increased risk of meningeal relapses. Prognosis of both types of AML has been reported to be better than prognosis of the other entities combined. Since most of the published data were collected from heterogeneous patient populations treated with various chemotherapeutic regimens, we have analyzed treatment outcome of AML M3 and M4Eo in the AMLCG-85 study for patients younger than 60 years. For the total population of 594 patients of this study, CR rate was 68.89%, early death rate 11.60%, and no or partial remission was achieved in 19.51% of the cases. Of 40 patients with AML M3 or M3 v complete remission was attained in 62.5%. Nine patients died within 42 days after the start of antileukemic therapy (22.5%). Of these nine, four died because of infection, five because of bleeding. Relapse-free survival rate was 59% after 3 years, significantly better than the respective curve of the other FAB types combined (35% after 3 years). In AML M4Eo, 91.7% of the 24 patients reached complete remission. The early death rate was 8.3%. No case of nonresponse was seen. Relapse-free survival rate was 49% after 3 years compared with 35% for the other types combined.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1994

The phenotype of L-CFU and its correlation with the immunological characteristics of the blast cell population in AML.

The membrane phenotype of AML clonogenic cells (L-CFU) was analyzed in 19 AML patients using an in vitro culture technique after a complement-mediated lysis assay employing a panel of six monoclonal antibodies (McAb) -HLA-DR, FMC56 (CD9), FMC27 (CD9), CD14, CD15, CD41a-. Our results show that L-CFU has a heterogeneous but immature phenotype lacking on the expression of differentiation antigens (CD14, CD15, CD41a). In addition, we observed that the L-CFU phenotype is different from that of the whole blast cell population. Interestingly, L-CFU showed a higher expression of HLA-DR antigens with respect to their progeny. Upon analyzing whether the L-CFU phenotype was related to both the morphological and immunological features of AML blast cells, it was observed that, while there is no correlation with the FAB classification, there was a partial relationship between the immunological phenotype of AML blast cells and that of L-CFU. Accordingly, the more immature AML cases showed a more differentiated L-CFU phenotype (HLA-DR+, CD9+, FMC27+) when compared with cases with a more mature blast cell phenotype. These results suggest that those AML cases with a relatively immature myeloblastic phenotype may arise from a progenitor cell that has undergone partial differentiation and that is unable to acquire myeloid differentiation antigens, while those AML cases with mature blast cells might emerge from a very early L-CFU that has the capacity to undergo a greater degree of differentiation.

Antigens, CD↗

PubMed2005

AML bearing the translocation t(11;17)(q23;q21): involvement of MLL and a region close to RARA, with no differentiation response to retinoic acid.

We describe a case of acute myeloid leukemia (AML) bearing the translocation t(11;17)(q23;q21). The morphological phenotype represented a monoblastic leukemia, AML French-American-British (FAB) M5a. Further analysis of the translocation revealed an involvement of the mixed-lineage leukemia (MLL) gene and a region closely proximal to the retinoic acid (RA) receptor alpha (RARA) gene. AMLs involving both a rearranged MLL and the 17q21 region, in which the RARA gene is located, have only been described in some individual cases. The functional role of this translocation is still unknown. Rearrangements of the MLL (11q23) gene in AML are usually related to the morphological phenotype FAB M5. In general, they are associated with an adverse prognosis. In acute promyelocytic leukemia, the translocation (15;17)(q22;q11-21) involving the RARA leads to a maturation arrest that can be overcome by RA, often inducing remission. In other forms of AML, however, the effects of RA are limited and diverse. To study whether RA might have a therapeutical potential in our case, we performed an in vitro analysis of RA effects on AML cells. We found that RA leads to enhanced cell death and up-regulation of CD38 and CD117. However, no hints of RA-induced in vitro differentiation were visible. Our data indicate that in AML cells bearing the t(11;17)(q23;q21), a differentiation arrest that is overcome by RA is not present. On the contrary, RA induces alterations in cellular regulation that are similar to the RA-induced changes observed in early hematogenic progenitors; thus, a possible therapeutical benefit of RA in such cases remains open.

ADP-ribosyl Cyclase 1↗

PubMed2005

Employing the immunological synapse in AML: development of leukemic dendritic cells for active specific immunization.

Cytotoxic T cells directed against leukemic blasts have been observed in patients with acute myeloid leukemia (AML). However, generation of efficient T-cell responses is hampered due to several factors that enable AML blasts to protect themselves from the patients immune system. Improved immune responses can be established by the differentiation of AML blasts into AML-derived dendritic cells (DC) thereby conserving their intrinsic leukemia specific antigens and obtaining full capacity to present these antigens to naive T cells. This review discusses increased immunogenicity of AML blasts by differentiation into AML-DC and describes ways to augment the AML-DC vaccination approach.

Animals↗

PubMed1999

Kinetic characteristics of de novo and secondary AML cells influence their response to haemopoietic growth factor (HGF) priming and correlate with clinical outcome.

This study has assessed the effect of in vitro haemopoietic growth factor (HGF) priming on the S phase activity of cells from patients with de novo AML and AML secondary to MDS. The occurrence of receptors for G-CSF, GM-CSF, IL-3 and SCF on marrow cells was assessed using immunofluorescent ligand binding assays. Additionally, patients responses to first phase induction chemotherapy was recorded to examine whether in vitro kinetic data might correlate with clinical outcome. All kinetic and receptor assays were performed in normal marrow cells to ascertain their response to priming. Incubation of AML cells in serum free medium (SFM) +/- G + GM-CSF, IL-3, SCF, G + GM-CSF + SCF or IL-3 + SCF prior to S phase assessment revealed that priming permutations inclusive of SCF were most effective but also that the baseline level of S phase activity with SFM alone influenced the subsequent response to priming. Regardless of AML group, samples with low baseline S phase activity (< 10%) were significantly more responsive than those with high (> 10%) SFM S phase levels. However there was no corresponding difference in the percentages of cells bearing receptors. In both AML groups, low baseline S phase activity was observed more frequently in samples from patients who achieved CR. Normal samples possessed receptors for all HGFs and were responsive to all priming permutations except SCF alone. This study raises four points: (a) it may be prudent to reserve the use of priming HGFs for those patients with low baseline S phase activity whose cells respond in vitro and to use SCF in these priming cocktails; (b) the presence of receptors capable of ligand binding in AML samples did not guarantee kinetic response; (c) normal progenitors were responsive to priming which may have implications for haemopoietic reconstitution post therapy; and (d) the kinetic characteristics of AML progenitors may influence clinical outcome regardless of whether treatment includes HGFs.

Acute Disease↗

PubMed2004

AML-1 is required for megakaryocytic maturation and lymphocytic differentiation, but not for maintenance of hematopoietic stem cells in adult hematopoiesis.

Embryonic development of multilineage hematopoiesis requires the precisely regulated expression of lineage-specific transcription factors, including AML-1 (encoded by Runx1; also known as CBFA-2 or PEBP-2alphaB). In vitro studies and findings in human diseases, including leukemias, myelodysplastic syndromes and familial platelet disorder with predisposition to acute myeloid leukemia (AML), suggest that AML-1 has a pivotal role in adult hematopoiesis. However, this role has not been fully uncovered in vivo because of the embryonic lethality of Runx1 knockout in mice. Here we assess the requirement of AML-1/Runx1 in adult hematopoiesis using an inducible gene-targeting method. In the absence of AML-1, hematopoietic progenitors were fully maintained with normal myeloid cell development. However, AML-1-deficient bone marrow showed inhibition of megakaryocytic maturation, increased hematopoietic progenitor cells and defective T- and B-lymphocyte development. AML-1 is thus required for maturation of megakaryocytes and differentiation of T and B cells, but not for maintenance of hematopoietic stem cells (HSCs) in adult hematopoiesis.

Adult↗

PubMed2002

Quantitative real-time RT-PCR detects elevated Wilms tumor gene (WT1) expression in autologous blood stem cell preparations (PBSCs) from acute myeloid leukemia (AML) patients indicating contamination with leukemic blasts.

High-dose chemotherapy with subsequent autologous stem cell transplantation is believed to be of therapeutic benefit in patients with acute myeloid leukemia (AML), especially when no allogeneic bone marrow donor is available. One of the main risks is contamination of the stem cell preparations with leukemic blasts, which may account for a higher relapse rate compared to allogeneic bone marrow transplantation. Since overexpression of WT1 is common in leukemic blasts, we investigated, whether PBSCs from AML patients express WT1 at a higher level as compared to patients with solid cancers. PBSCs of seven patients with AML and of five patients with solid cancers were investigated for WT1 expression. Total WT1 copy count was determined in a standardized quantitative real time RT-PCR. WT1 expression was found in all AML PBSCs with an average copy number of 49.99 +/- 61.09. In solid cancers WT1 expression was statistically significantly lower with a copy number of 3.51 +/- 1.92. In AML patients with sustained complete remission we found a nearly significantly lower WT1 expression than in patients who relapsed within the first year after stem cell transplantation. Our data show a higher WT1 expression in PBSCs of AML patients compared to patients with solid cancers. This finding might indicate a contamination with leukemic blasts. Quantification of WT1 in PBSCs might therefore be useful to estimate the risk of relapse after autologous stem cell transplantation in AML patients.

Acute Disease↗

PubMed2000

Increased frequency of dicentric chromosomes in therapy-related MDS and AML compared to de novo disease is significantly related to previous treatment with alkylating agents and suggests a specific susceptibility to chromosome breakage at the centromere.

Dicentric chromosomes are observed in many malignant diseases including myelodysplasia (MDS) and acute myeloid leukemia (AML) and have often been observed in a subset of these diseases, namely therapy-related MDS (t-MDS) and AML (t-AML). Using fluorescence in situ hybridization (FISH) with centromere-specific probes, we investigated the frequency and type of dicentric chromosomes in 180 consecutive patients with t-MDS and t-AML and in 231 consecutive patients with de novo MDS and AML, whose karyotypes had been studied previously by conventional G-banding. Twenty-seven out of 180 patients with t-MDS or t-AML presented dicentric chromosomes compared to only seven out of 231 patients with de novo disease (P = 0.00003). A dic(1q;7p) was observed in 10 cases, a dic(5p;17q) was observed in six cases, whereas various isodicentric chromosomes were observed in six cases. Excluding these six cases with isodicentrics, all 25 patients with dicentric chromosomes had involvement of at least one of the chromosome arms 1q, 5p, or 7p resulting in monosomy for 5q or 7q, and/or trisomy for 1q. Patients with dicentric chromosomes presented significantly more often as t-MDS compared to patients without dicentrics (P = 0.046), and the presence of a dicentric chromosome was significantly related to previous therapy with alkylating agents (P = 0.026). Thus, only one out of 27 patients with a dicentric chromosome had not previously received an alkylating agent. A specific susceptibility to breakage at the centromere after exposure to alkylating agents is suggested and may explain the frequent loss of whole chromosomes, in particular chromosomes 5 and 7 in t-MDS and t-AML, if the breaks are not followed by rejoining. Leukemia (2000) 14, 105-111.

Antineoplastic Agents, Alkylating↗

PubMed2002

Human AML cells in NOD/SCID mice: engraftment potential and gene expression.

Most cases of human acute myeloid leukemia (AML) engraft in irradiated non-obese diabetic/severe combined immunodeficient (NOD/SCID) mice. Intravenous transfer of as few as 10(5) human AML cells resulted in engraftment. Cases with poor prognosis clinical features, including FLT3 mutations, tended to engraft efficiently. Nevertheless, AML cells obtained from patients at relapse did not engraft more efficiently than cells obtained from the same patients at initial diagnosis. One passage of human AML cells in NOD/SCID mice did not appear to select for increased virulence, as measured by serial transplantation efficiency. Finally, cDNA microarray analyses indicated that approximately 95% of genes were expressed at similar levels in human AML cells immunopurified after growth in mice, as compared to cells assessed directly from patients. Thus, the growth of human AML cells in NOD/SCID mice could yield large numbers of human AML cells for direct experimental use and could also function as a renewable, potentially unlimited source of leukemia cells, via serial transplantation.

Acute Disease↗

PubMed2005

Gatekeeper pathways and cellular background in the pathogenesis and therapy of AML.

Acute myelogenous leukemia (AML) is characterized by the accumulation of immature cells due to disturbed differentiation and proliferation of the myeloid lineage. Genetic alterations affecting transcription factors and receptor tyrosine kinases have been identified in AML and causally linked to the disease. The goal of this review is to address the role of the different genetic alterations in self-renewal and proliferation and to discuss the cellular background in which these events occur during the pathogenesis of AML. Data from AML samples, clinical studies and mouse models for AML will be used to support the different theories regarding the leukemogenesis of AML. Finally, this review wants to highlight the implication of these findings for the therapy of AML.

Animals↗

PubMed2005

Treatment strategies and long-term results in paediatric patients treated in four consecutive AML-BFM trials.

A total of 1111 children with acute myeloblastic leukaemia (AML) were treated in four consecutive Berlin-Frankfurt-Münster (BFM) studies from 1978 to 1998. The first cooperative trial AML-BFM 78 established intensive chemotherapy with seven drugs, CNS irradiation and 2-year maintenance, achieving a long-term survival (overall survival (OS)) of 40%. Induction intensification in AML-BFM 83 resulted in significant improvement of disease-free survival (DFS). The risk of haemorrhage, especially in children with hyperleukocytosis, proved the high relevance of supportive care. In AML-BFM 87, the benefit of CNS irradiation in preventing CNS/systemic relapses was demonstrated. In AML-BFM 93, the introduction of idarubicin during first induction followed by intensification with HAM increased the 5-year EFS, DFS and OS to 50+/-2, 61+/-3 and 57+/-2%, respectively. Stem cell transplantation (SCT), as applied in high-risk patients with a matched related donor, did not significantly improve the outcome compared to chemotherapy alone. In spite of treatment intensification, the therapy-related death rate decreased from trial to trial, mainly during induction. The future aim is to reduce long-term sequelae, especially cardiotoxicity, by administration of less cardiotoxic drugs, and toxicity of SCT by risk-adapted indications. The AML-BFM studies performed in three European countries with >70 cooperating centres have significantly improved the outcome in AML children; nevertheless, increasing experience with these intensive treatment regimens is of fundamental importance to reduce fatal complications.

Adolescent↗

PubMed2004

Transcriptional regulation of human osteopontin promoter by C/EBPalpha and AML-1 in metastatic cancer cells.

Osteopontin (OPN) is a secreted glycoprotein produced by osteoclasts, macrophages, T cells, hematopoietic cells, and vascular smooth muscle cells. It contributes to macrophage homing and cellular immunity. It also mediates neovascularization, inhibits apoptosis, and plays important roles in extracellular matrix remodeling and angiogenesis. These properties are also characteristics of metastatic cancer cells. Consequently, the OPN gene was found to be upregulated among various metastatic cancer cells. This suggests that OPN is involved in tumor metastasis. How the OPN gene is upregulated in metastatic cancer cells remains to be illustrated. Thus, we investigated the transcriptional activation of the OPN promoter in the human metastatic cancer cell line A2058. We cloned the OPN promoter, and serial deletion analysis of the OPN promoter showed that the region between -170 and -127 may act as an enhancer to control the OPN gene in metastatic tumor cells. This region was found to contain overlapped AML-1 and C/EBP binding site motifs. Gel-mobility-shift assays using the A2058 nuclear extract and AML-1a or C/EBPalpha (CCAAT/enhancer binding protein alpha) recombinant protein indicated that these two transcription factors can bind to the overlapped AML-1 /C/EBP binding site motifs on the OPN regulatory sequence from -147 to -127. Surprisingly, the gel-shift experiments did not show supershift complex formation between AML-1 and C/EBPalpha. Functional analysis showed that the C/EBPalpha was more potent than the complex of AML-1 and its cofactor CBFbeta to upregulate the OPN promoter. In addition, AML-1 and C/EBPalpha did not exhibit transactivation additively or synergistically. Our results suggest that AML-1 and C/EBPalpha play an important role in the upregulation of the OPN gene in metastatic tumor cells.

Binding Sites↗

PubMed2004

Expression and prognostic value of hemopoietic cytokine receptors in acute myeloid leukemia (AML): implications for future therapeutical strategies.

OBJECTIVES: Hemopoietic cytokines regulate hemopoietic cell functions via specific cell surface receptors. There is evidence to suggest, that those receptors (R) could play a role in leukemia with respect to cell differentiations and its regulation, prognosis, and pathobiology. Knowledge of individual cytokine receptor (CKR) profiles could provide new discoveries about CKR-supported therapeutic considerations. METHODS: We have studied the expression of CKR on mononuclear bone marrow (BM) cells of 89 patients with acute myeloid leukemia (AML) at first diagnosis, three patients at relapse or with persisting AML and eight healthy probands by fluorescence-activated cell sorting (FACS) analysis using directly fluorescein-conjugated antibodies: CD114 (hG-CSF-R), CD116 (hGM-CSF-R), CD117 (hSCF-R), CD123 (hIL-3-R), CD130 (gp130subunit), CD135 (hFL-R). A case was defined as positive, if more than 20% of the cells expressed the regarding CKR. RESULTS: All investigated CKR were more frequently expressed in AML-samples than in healthy BM-samples, except CD130, which was only expressed on 5-6% of AML-blasts in all and with only one healthy BM-sample being CD130(+). Within the French-American-British (FAB) types we observed a maturation- and lineage (granulocytic/monocytic)-committed expression profile. Monocytic subtypes (FAB-type M4/M5) showed significantly more GM-CSF-R(+) (P = 0.001) and FL-R(+) (P = 0.001) and significantly less stem cell factor-R (SCF-R(+)) (P = 0.02) cases. Highest proportions of G-CSF-R(+) blasts were observed in FAB-type M3. In undifferentiated leukemias (FAB-type M1, M2) high amounts of SCF-R(+), IL-3-R(+), and FL-R(+) blasts could be detected. FL-R was the only CKR, which was positive in FAB-type M0 (n = 2). No differences in CKR-expression were detected between primary (p) and secondary (s). Separating our patient cohorts in cytogenetic risk groups we could detect a significant higher proportion of G-CSF-R(+) blasts in the cytogenetic good risk group than in the bad risk group (P = 0.027), but G-CSF-R-expression did not correlate with remission-rate or relapse-free survival probability of the patients. For clinical evaluation only patients treated by the AML-CG-protocol, were included (n = 53). There were no differences of CKR-expression in the responder and non-responder group, however, significant lower relapse-free survival probabilities for patients with more than 85.5% FL-R(+) (P = 0.001) and more than 45.5% SCF-R(+) blasts were found (P = 0.02). Patients with more than 32.5% IL-3-R(+) cells also showed a tendency to a lower relapse-free survival probability (P = 0.26), whereas patients with more than 33% GM-CSF-R(+) (P = 0.06) and patients with more than 52% G-CSF-R(+) (P = 0.175) blasts tended to have a higher relapse-free survival probability. CONCLUSION: We can conclude, that CKR-expression in AML is maturation- and lineage-committed and the proportions of especially early acting CKR have influence on relapse-free survival probability of AML-patients, independently of the karyotype. With respect to the individual CKR status the benefit of cytokines as priming agents, as agents to treat neutropenia or to influence the metabolism of chemotherapy can be discussed under new points of view.

Adult↗

PubMed2006

Elevated reactive oxygen species but not glutathione regulate mercury resistance to AML-2/DX100 cells.

The multidrug resistance-associated protein (MRP1) mediates cellular efflux of various xenobiotics and cellular resistance to heavy metals. Previously we reported that MRP1 mediates resistance to mercury exposure and possible mechanism mediating MRP1 expression after mercury exposure. This study was designed to investigate the role of reactive oxygen species (ROS) and glutathione on the resistance of AML-2/DX100 cells to mercuric chloride. The MRP1 overexpressing cells (AML-2/DX100) cells showed less scavenging activity to ROS induced by mercury while no difference in the basal glutathione levels between AML-2/WT and AML-2/DX100 cells. Mercury induced the activation of p38 mitogen-activated protein kinase (MAPK) and extracellular signal-regulated kinase (ERK) but not c-jun-N-terminal kinase in AML-2/DX100 cells. The specific inhibitor for p38 MAPK and ERK, and antioxidant decreased the production of MRP1 and therefore resistance of AML-2/DX100 cells against mercury exposure. These results suggest that induction of ROS and downstream p38 MAPK and ERK were involved in the resistance of cells to mercury by expression MRP1 in AML-2/DX100 cells.

Acetylcysteine↗

PubMed2001

CD133 (AC133) expression on AML cells and progenitors.

BACKGROUND: AML blasts differ in their functional capability, creating a hierarchy of progenitors. CD133 (AC133) is a newly described transmembrane protein expressed on CD34(+) and CD34(-) normal progenitors. We characterized the prognostic significance of CD133 expression in AML and expression of CD133 on AML progenitors thought to be responsible for maintaining this disease. METHODS: AML cells from 102 patients were analyzed for CD133 and CD34 expression, and correlated with outcome in 92 treated patients. AML cells were also FACS sorted into CD34(+)/CD133(+), CD34(+)/CD133(-), CD34(-)/CD133(+) and CD34(-)/CD133(-) subfractions, and assayed in vitro in colony-forming assay (CFU) and in suspension culture (SC) assay for up to 8 weeks, and in vivo in non-obese diabetic (NOD)/SCID mice to determine the phenotype of progenitors detected in these assays. RESULTS: CD133 expression was not correlated with event-free or overall survival, FAB subtype, cytogenetic abnormality or WBCC, but was correlated with CD34 expression. Primary AML CFU were present in all four sorted fractions. After an increasing period of time in SC, a higher proportion of cells capable of forming leukemic CFU were found in the CD34(+)/CD133(+) subfraction. Cells capable of producing leukemic engraftment in NOD/SCID mice were found in all subfractions, including the CD34(-)/CD133(-) subfraction in many patients. DISCUSSION: CD133 is not useful as a prognostic marker in AML. CD133 is expressed with CD34 on most primitive leukemic progenitors detected in vitro, however, in vivo progenitors could not be purified using CD133 in these patients.

Acute Disease↗

PubMed1995

The effect of haemopoietic growth factors on the cell cycle of AML progenitors and their sensitivity to cytosine arabinoside in vitro.

This study examines the effect of pretreatment in liquid culture of acute myeloid leukaemic (AML) progenitors with recombinant human IL-3 or G and GM-CSF. Prior to and following cytokine priming, the sensitivity of cells to cytosine arabinoside (Ara-C) at concentrations ranging from 10(-12) to 10(-4) M was assessed in clonogenic culture. In addition, the initial percentage of AML cells in S phase was assessed and their subsequent kinetic response to cytokine treatment evaluated by FACScan analysis. Light-density marrow cells (LDMCs) from 19 AML patients were initially T-cell and monocyte depleted in order to remove potential sources of endogenous cytokine production prior to in vitro investigation. LDMCs were incubated in liquid phase for 7 d in a chemically defined complete medium with or without cytokines. Clonogenic data from fresh AML LDMCs not pretreated with growth factors demonstrated a heterogenous response to Ara-C. In only 4/15 marrows tested clonogenically was there any improvement in sensitivity to Ara-C following cytokine priming. S-phase data on all 19 marrows were similarly variable either before or after cytokine preincubation. There was no discernible correlation between clonogenic and kinetic data, nor could any relationship be established between in vitro findings and the FAB subtypes of patients or clinical outcomes. In summary, it would appear that the cell-cycle status of AML cells is likely to be only one of many contributory factors governing the sensitivity of AML progenitors to Ara-C. The clinical response of AML patients to cytokine therapy in association with cell-cycle-specific cytotoxic agents may therefore be variable and unpredictable.

Acute Disease↗

PubMed2002

Expression of transcription factor AML-2 (RUNX3, CBF(alpha)-3) is induced by Epstein-Barr virus EBNA-2 and correlates with the B-cell activation phenotype.

To identify cell proteins regulated by the Epstein-Barr virus (EBV) transcription factor EBNA-2, we analyzed a cell line with conditional EBNA-2 activity by using microarray expression profiling. This led to the identification of two novel target genes induced by EBNA-2. The first of these, interleukin-16, is an immunomodulatory cytokine involved in the regulation of CD4 T cells. The second, AML-2, is a member of the Runt domain family of transcription factors. Quiescent B cells initially expressed AML-1 but, 48 h after virus infection, the levels of AML-1 decreased dramatically, whereas the amount of AML-2 protein increased. Analysis of a panel of B-cell lines indicated that AML-2 expression is normally predominant in EBV latency III, whereas AML-1 is associated with EBV latency I or EBV-negative cells. The AML genes are the first example of cell transcription factors whose expression correlates with the latency I/III phenotype.

Adaptor Proteins, Signal Transducing↗

PubMed2004

Identification of a novel activating mutation (Y842C) within the activation loop of FLT3 in patients with acute myeloid leukemia (AML).

Fms-like tyrosine kinase 3 (FLT3) receptor mutations as internal tandem duplication (ITD) or within the kinase domain are detected in up to 35% of patients with acute myeloid leukemia (AML). N-benzoyl staurosporine (PKC412), a highly effective inhibitor of mutated FLT3 receptors, has significant antileukemic efficacy in patients with FLT3-mutated AML. Mutation screening of FLT3 exon 20 in AML patients (n = 110) revealed 2 patients with a novel mutation (Y842C) within the highly conserved activation loop of FLT3. FLT3-Y842C-transfected 32D cells showed constitutive FLT3 tyrosine phosphorylation and interleukin 3 (IL-3)-independent growth. Treatment with PKC412 led to inhibition of proliferation and apoptotic cell death. Primary AML blasts bearing FLT3-Y842C mutations showed constitutive FLT3 and signal transducer and activator of transcription 5 (STAT-5) tyrosine phosphorylation. Ex vivo PKC412 treatment of primary blasts resulted in suppression of constitutive FLT3 and STAT-5 activation and apoptotic cell death. Inspection of the FLT3 structure revealed that Y842 is the key residue in regulating the switch from the closed to the open (= active) conformation of the FLT3 activation loop. Overall, our data suggest that mutations at Y842 represent a significant new activating mutation in AML blasts. Since FLT3 tyrosine kinase inhibitors (TKIs) such as PKC412 are currently being investigated in clinical trials in AML, extended sequence analysis of FLT3 may be helpful in defining the spectrum of TKI-sensitive FLT3 mutations in AML.

Animals↗