RESUMEN
Venetoclax combination therapies are becoming the standard of care in acute myeloid leukemia (AML). However, the therapeutic benefit of these drugs in older/unfit patients is limited to only a few months, highlighting the need for more effective therapies. Protein phosphatase 2A (PP2A) is a tumor suppressor phosphatase with pleiotropic functions that becomes inactivated in â¼70% of AML cases. PP2A promotes cancer cell death by modulating the phosphorylation state in a variety of proteins along the mitochondrial apoptotic pathway. We therefore hypothesized that pharmacological PP2A reactivation could increase BCL2 dependency in AML cells and, thus, potentiate venetoclax-induced cell death. Here, by using 3 structurally distinct PP2A-activating drugs, we show that PP2A reactivation synergistically enhances venetoclax activity in AML cell lines, primary cells, and xenograft models. Through the use of gene editing tools and pharmacological approaches, we demonstrate that the observed therapeutic synergy relies on PP2A complexes containing the B56α regulatory subunit, of which expression dictates response to the combination therapy. Mechanistically, PP2A reactivation enhances venetoclax-driven apoptosis through simultaneous inhibition of antiapoptotic BCL2 and extracellular signal-regulated kinase signaling, with the latter decreasing MCL1 protein stability. Finally, PP2A targeting increases the efficacy of the clinically approved venetoclax and azacitidine combination in vitro, in primary cells, and in an AML patient-derived xenograft model. These preclinical results provide a scientific rationale for testing PP2A-activating drugs with venetoclax combinations in AML.
Asunto(s)
Leucemia Mieloide Aguda , Proteína Fosfatasa 2 , Humanos , Anciano , Proteína 1 de la Secuencia de Leucemia de Células Mieloides , Línea Celular Tumoral , Proteínas Proto-Oncogénicas c-bcl-2 , Leucemia Mieloide Aguda/genética , Compuestos Bicíclicos Heterocíclicos con Puentes/farmacología , Compuestos Bicíclicos Heterocíclicos con Puentes/uso terapéutico , ApoptosisRESUMEN
Although light-chain amyloidosis (AL) and multiple myeloma (MM) are characterized by tumor plasma cell (PC) expansion in bone marrow (BM), their clinical presentation differs. Previous attempts to identify unique pathogenic mechanisms behind such differences were unsuccessful, and no studies have investigated the differentiation stage of tumor PCs in patients with AL and MM. We sought to define a transcriptional atlas of normal PC development in secondary lymphoid organs (SLOs), peripheral blood (PB), and BM for comparison with the transcriptional programs (TPs) of tumor PCs in AL, MM, and monoclonal gammopathy of undetermined significance (MGUS). Based on bulk and single-cell RNA sequencing, we observed 13 TPs during transition of normal PCs throughout SLOs, PB, and BM. We further noted the following: CD39 outperforms CD19 to discriminate newborn from long-lived BM-PCs; tumor PCs expressed the most advantageous TPs of normal PC differentiation; AL shares greater similarity to SLO-PCs whereas MM is transcriptionally closer to PB-PCs and newborn BM-PCs; patients with AL and MM enriched in immature TPs had inferior survival; and protein N-linked glycosylation-related TPs are upregulated in AL. Collectively, we provide a novel resource to understand normal PC development and the transcriptional reorganization of AL and other monoclonal gammopathies.
Asunto(s)
Amiloidosis de Cadenas Ligeras de las Inmunoglobulinas/patología , Mieloma Múltiple/patología , Células Plasmáticas/patología , Transcriptoma , Adulto , Humanos , Amiloidosis de Cadenas Ligeras de las Inmunoglobulinas/genética , Mieloma Múltiple/genética , Células Plasmáticas/metabolismo , Células Tumorales CultivadasRESUMEN
Mesothelioma is an aggressive tumor that affects thousands of people every year. The therapeutic options for patients are limited; hence, a better understanding of mesothelioma biology is crucial to improve patient survival. To find new molecular targets and therapeutic strategies related to the protein phosphatase 2A (PP2A) network, we analyzed the gene expression of known PP2A inhibitors in mesothelioma patient samples. Our analysis disclosed a general overexpression of all PP2A-negative regulators in mesothelioma patients. Moreover, the expression of ANP32E and CIP2A genes, increased in 16% and 11% of cases, positively correlates with the ones of all the other PP2A regulators and the ones of the main cyclins and CDKs, suggesting the existence of a feed-forward loop that might contribute to the mesothelioma progression via PP2A inactivation. Overall, our study indicates the existence of a strategic and targetable axis between PP2A inhibitors (ANP32E and CIP2A) and cell cycle regulators (cyclin B2/CDK1) and provides a valuable rationale for using a personalized combinational therapy approach to improve mesothelioma patient survival.
Asunto(s)
Proteína Quinasa CDC2/genética , Mesotelioma/genética , Terapia Molecular Dirigida , Proteína Fosfatasa 2/genética , Autoantígenos/genética , Ciclo Celular/genética , Proteínas de Ciclo Celular/genética , División Celular/genética , Línea Celular Tumoral , Ciclina B2/genética , Minería de Datos , Femenino , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos , Humanos , Péptidos y Proteínas de Señalización Intracelular/genética , Masculino , Proteínas de la Membrana/genética , Mesotelioma/tratamiento farmacológico , Mesotelioma/inmunología , Mesotelioma/patología , Chaperonas Moleculares/genética , Fosforilación/efectos de los fármacos , Proteína Fosfatasa 2/antagonistas & inhibidores , Transducción de Señal/efectos de los fármacosRESUMEN
Germline GATA2 mutations have been identified as the cause of familial syndromes with immunodeficiency and predisposition to myeloid malignancies. GATA2 mutations appear to cause loss of function of the mutated allele leading to haploinsufficiency; however, this postulate has not been experimentally validated as the basis of these syndromes. We hypothesized that mutations that are translated into abnormal proteins could affect the transcription of GATA2, triggering GATA2 deficiency. Chromatin immunoprecipitation and luciferase assays showed that the human GATA2 protein activates its own transcription through a specific region located at -2.4 kb, whereas the p.Thr354Met, p.Thr355del, and p.Arg396Gln germline mutations impair GATA2 promoter activation. Accordingly, GATA2 expression was decreased to â¼58% in a patient with p.Arg396Gln, compared with controls. p.Arg396Gln is the second most common mutation in these syndromes, and no previous functional analyses have been performed. We therefore analyzed p.Arg396Gln. Our data show that p.Arg396Gln is a loss-of-function mutation affecting DNA-binding ability and, as a consequence, it fails to maintain the immature characteristics of hematopoietic stem and progenitor cells, which could result in defects in this cell compartment. In conclusion, we show that human GATA2 binds to its own promoter, activating its transcription, and that the aforementioned mutations impair the transcription of GATA2. Our results indicate that they can affect other GATA2 target genes, which could partially explain the variability of symptoms in these diseases. Moreover, we show that p.Arg396Gln is a loss-of-function mutation, which is unable to retain the progenitor phenotype in cells where it is expressed.
Asunto(s)
Factor de Transcripción GATA2/genética , Mutación de Línea Germinal , Síndromes de Inmunodeficiencia/inmunología , Infección por Mycobacterium avium-intracellulare/inmunología , Transcripción Genética , Alelos , Sitios de Unión , Línea Celular Tumoral , Femenino , Factor de Transcripción GATA2/inmunología , Regulación de la Expresión Génica , Predisposición Genética a la Enfermedad , Haploinsuficiencia , Humanos , Síndromes de Inmunodeficiencia/complicaciones , Síndromes de Inmunodeficiencia/genética , Síndromes de Inmunodeficiencia/patología , Persona de Mediana Edad , Modelos Moleculares , Complejo Mycobacterium avium/inmunología , Infección por Mycobacterium avium-intracellulare/complicaciones , Infección por Mycobacterium avium-intracellulare/genética , Infección por Mycobacterium avium-intracellulare/patología , Fenotipo , Regiones Promotoras Genéticas , Unión Proteica , Transducción de SeñalRESUMEN
We identified a duplication of the MYB oncogene in 8.4% of individuals with T cell acute lymphoblastic leukemia (T-ALL) and in five T-ALL cell lines. The duplication is associated with a threefold increase in MYB expression, and knockdown of MYB expression initiates T cell differentiation. Our results identify duplication of MYB as an oncogenic event and suggest that MYB could be a therapeutic target in human T-ALL.
Asunto(s)
Diferenciación Celular/genética , Duplicación de Gen , Genes myb/genética , Leucemia-Linfoma de Células T del Adulto/genética , Linfocitos T/patología , Diferenciación Celular/inmunología , Línea Celular Tumoral , Cromosomas Artificiales/genética , Citometría de Flujo , Dosificación de Gen , Regulación Neoplásica de la Expresión Génica/genética , Pruebas Genéticas , Humanos , Hibridación Fluorescente in Situ , Cariotipificación , Mutación/genética , Hibridación de Ácido Nucleico/genética , ARN Interferente Pequeño/genética , Estadísticas no ParamétricasRESUMEN
Protein phosphatase 2A (PP2A) inactivation is common in cancer, leading to sustained activation of pro-survival and growth-promoting pathways. PP2A consists of a scaffolding A-subunit, a catalytic C-subunit, and a regulatory B-subunit. The functional complexity of PP2A holoenzymes arises mainly through the vast repertoire of regulatory B-subunits, which determine both their substrate specificity and their subcellular localization. Therefore, a major challenge for developing more effective therapeutic strategies for cancer is to identify the specific PP2A complexes to be targeted. Of note, the development of small molecules specifically directed at PP2A-B56α has opened new therapeutic avenues in both solid and hematological tumors. Here, we focus on the B56/PR61 family of PP2A regulatory subunits, which have a central role in directing PP2A tumor suppressor activity. We provide an overview of the mechanisms controlling the formation and regulation of these complexes, the pathways they control, and the mechanisms underlying their deregulation in cancer.
Asunto(s)
Neoplasias , Proteína Fosfatasa 2 , Humanos , Proteína Fosfatasa 2/genética , Procesamiento Proteico-Postraduccional , Dominio Catalítico , Holoenzimas/química , Holoenzimas/metabolismoRESUMEN
The in-frame internal tandem duplication (ITD) of the FLT3 gene is an important negative prognostic factor in acute myeloid leukemia (AML). FLT3-ITD is constitutive active and partially retained in the endoplasmic reticulum (ER). Recent reports show that 3'UTRs function as scaffolds that can regulate the localization of plasma membrane proteins by recruiting the HuR-interacting protein SET to the site of translation. Therefore, we hypothesized that SET could mediate the FLT3 membrane location and that the FLT3-ITD mutation could somehow disrupt the model, impairing its membrane translocation. Immunofluorescence and immunoprecipitation assays demonstrated that SET and FLT3 co-localize and interact in FLT3-WT cells but hardly in FLT3-ITD. SET/FLT3 interaction occurs before FLT3 glycosylation. Furthermore, RNA immunoprecipitation in FLT3-WT cells confirmed that this interaction occurs through the binding of HuR to the 3'UTR of FLT3. HuR inhibition and SET nuclear retention reduced FLT3 in the membrane of FLT3-WT cells, indicating that both proteins are involved in FLT3 membrane trafficking. Interestingly, the FLT3 inhibitor midostaurin increases FLT3 in the membrane and SET/FLT3 binding. Therefore, our results show that SET is involved in the transport of FLT3-WT to the membrane; however, SET barely binds FLT3 in FLT3-ITD cells, contributing to its retention in the ER.
RESUMEN
Acute myeloid leukemias (AMLs) result from multiple genetic alterations in hematopoietic stem cells. We describe a novel t(12;18)(p13;q12) involving ETV6 in a patient with AML. The translocation resulted in overexpression of SETBP1 (18q12), located close to the breakpoint. Overexpression of SETBP1 through retroviral insertion has been reported to confer growth advantage in hematopoietic progenitor cells. We show that SETBP1 overexpression protects SET from protease cleavage, increasing the amount of full-length SET protein and leading to the formation of a SETBP1-SET-PP2A complex that results in PP2A inhibition, promoting proliferation of the leukemic cells. The prevalence of SETBP1 overexpression in AML at diagnosis (n = 192) was 27.6% and was associated with unfavorable cytogenetic prognostic group, monosomy 7, and EVI1 overexpression (P < .01). Patients with SETBP1 overexpression had a significantly shorter overall survival, and the prognosis impact was remarkably poor in patients older than 60 years in both overall survival (P = .015) and event-free survival (P = .015). In summary, our data show a novel leukemogenic mechanism through SETBP1 overexpression; moreover, multivariate analysis confirms the negative prognostic impact of SETBP1 overexpression in AML, especially in elderly patients, where it could be used as a predictive factor in any future clinical trials with PP2A activators.
Asunto(s)
Proteínas Portadoras/genética , Transformación Celular Neoplásica/genética , Leucemia Mieloide Aguda/diagnóstico , Leucemia Mieloide Aguda/genética , Proteínas Nucleares/genética , Anciano , Secuencia de Aminoácidos , Secuencia de Bases , Células Cultivadas , Regulación Leucémica de la Expresión Génica , Humanos , Células K562 , Masculino , Datos de Secuencia Molecular , Pronóstico , Regulación hacia ArribaRESUMEN
BACKGROUND: Protein phosphatase 2A is a novel potential therapeutic target in several types of chronic and acute leukemia, and its inhibition is a common event in acute myeloid leukemia. Upregulation of SET is essential to inhibit protein phosphatase 2A in chronic myeloid leukemia, but its importance in acute myeloid leukemia has not yet been explored. DESIGN AND METHODS: We quantified SET expression by real time reverse transcriptase polymerase chain reaction in 214 acute myeloid leukemia patients at diagnosis. Western blot was performed in acute myeloid leukemia cell lines and in 16 patients' samples. We studied the effect of SET using cell viability assays. Bioinformatics analysis of the SET promoter, chromatin immunoprecipitation, and luciferase assays were performed to evaluate the transcriptional regulation of SET. RESULTS: SET overexpression was found in 60/214 patients, for a prevalence of 28%. Patients with SET overexpression had worse overall survival (P<0.01) and event-free survival (P<0.01). Deregulation of SET was confirmed by western blot in both cell lines and patients' samples. Functional analysis showed that SET promotes proliferation, and restores cell viability after protein phosphatase 2A overexpression. We identified EVI1 overexpression as a mechanism involved in SET deregulation in acute myeloid leukemia cells. CONCLUSIONS: These findings suggest that SET overexpression is a key mechanism in the inhibition of PP2A in acute myeloid leukemia, and that EVI1 overexpression contributes to the deregulation of SET. Furthermore, SET overexpression is associated with a poor outcome in acute myeloid leukemia, and it can be used to identify a subgroup of patients who could benefit from future treatments based on PP2A activators.
Asunto(s)
Expresión Génica , Chaperonas de Histonas/genética , Leucemia Mieloide Aguda/diagnóstico , Leucemia Mieloide Aguda/genética , Factores de Transcripción/genética , Adulto , Anciano , Anciano de 80 o más Años , Línea Celular Tumoral , Proliferación Celular , Supervivencia Celular/genética , Proteínas de Unión al ADN , Femenino , Regulación Leucémica de la Expresión Génica , Humanos , Leucemia Mieloide Aguda/mortalidad , Masculino , Persona de Mediana Edad , Pronóstico , Proteína Fosfatasa 2/antagonistas & inhibidores , Recurrencia , Adulto JovenRESUMEN
Chromosomal rearrangements involving the MECOM (MDS1 and EVI1 complex) locus are recurrent genetic events in myeloid leukaemia and are associated with poor prognosis. In this study, we assessed the role of MECOM locus protein EVI1 in the transcriptional regulation of microRNAs (miRNAs) involved in the leukaemic phenotype. For this, we profiled expression of 366 miRNAs in 38 MECOM-rearranged patient samples, normal bone marrow controls and MECOM (EVI1) knock down/re-expression models. Cross-comparison of these miRNA expression profiling data showed that MECOM rearranged leukaemias are characterized by down regulation of MIR449A. Reconstitution of MIR449A expression in MECOM-rearranged cell line models induced apoptosis resulting in a strong decrease in cell viability. These effects might be mediated in part by MIR449A regulation of NOTCH1 and BCL2, which are shown here to be bona fide MIR449A targets. Finally, we confirmed that MIR449A repression is mediated through direct promoter occupation of the EVI1 transcriptional repressor. In conclusion, this study reveals MIR449A as a crucial direct target of the MECOM locus protein EVI1 involved in the pathogenesis of MECOM-rearranged leukaemias and unravels NOTCH1 and BCL2 as important novel targets of MIR449A. This EVI1-MIR449A-NOTCH1/BCL2 regulatory axis might open new possibilities for the development of therapeutic strategies in this poor prognostic leukaemia subgroup.
Asunto(s)
Proteínas de Unión al ADN/fisiología , Regulación hacia Abajo/fisiología , Leucemia/metabolismo , MicroARNs/biosíntesis , Proto-Oncogenes/fisiología , Factores de Transcripción/fisiología , Adulto , Anciano , Anciano de 80 o más Años , Apoptosis/genética , Supervivencia Celular , Proteínas de Unión al ADN/metabolismo , Perfilación de la Expresión Génica/métodos , Regulación Neoplásica de la Expresión Génica , Técnicas de Silenciamiento del Gen , Humanos , Lactante , Leucemia/genética , Leucemia/patología , Proteína del Locus del Complejo MDS1 y EV11 , MicroARNs/genética , Persona de Mediana Edad , Proteínas Proto-Oncogénicas c-bcl-2/biosíntesis , Proteínas Proto-Oncogénicas c-bcl-2/fisiología , ARN Neoplásico/genética , Receptor Notch1/biosíntesis , Receptor Notch1/fisiología , Elementos Reguladores de la Transcripción/fisiología , Factores de Transcripción/metabolismo , Células Tumorales CultivadasRESUMEN
BACKGROUND: The EVI1 gene (3q26) codes for a zinc finger transcription factor with important roles in both mammalian development and leukemogenesis. Over-expression of EVI1 through either 3q26 rearrangements, MLL fusions, or other unknown mechanisms confers a poor prognosis in acute myeloid leukemia. DESIGN AND METHODS: We analyzed the prevalence and prognostic impact of EVI1 over-expression in a series of 476 patients with acute myeloid leukemia, and investigated the epigenetic modifications of the EVI1 locus which could be involved in the transcriptional regulation of this gene. RESULTS: Our data provide further evidence that EVI1 over-expression is a poor prognostic marker in acute myeloid leukemia patients less than 65 years old. Moreover, we found that patients with no basal expression of EVI1 had a better prognosis than patients with expression/over-expression (P=0.036). We also showed that cell lines with over-expression of EVI1 had no DNA methylation in the promoter region of the EVI1 locus, and had marks of active histone modifications: H3 and H4 acetylation, and trimethylation of histone H3 lysine 4. Conversely, cell lines with no expression of EVI1 have DNA hypermethylation and are marked by repressive trimethylation of histone H3 lysine 27 at the EVI1 promoter. CONCLUSIONS: Our results identify EVI1 over-expression as a poor prognostic marker in a large, independent cohort of acute myeloid leukemia patients less than 65 years old, and show that the total absence of EVI1 expression has a prognostic impact on the outcome of such patients. Furthermore, we demonstrated for the first time that an aberrant epigenetic pattern involving DNA methylation, H3 and H4 acetylation, and trimethylation of histone H3 lysine 4 and histone H3 lysine 27 might play a role in the transcriptional regulation of EVI1 in acute myeloid leukemia. This study opens new avenues for a better understanding of the regulation of EVI1 expression at a transcriptional level.
Asunto(s)
Proteínas de Unión al ADN/genética , Regulación hacia Abajo/genética , Epigénesis Genética , Leucemia Mieloide Aguda/diagnóstico , Leucemia Mieloide Aguda/genética , Proto-Oncogenes/genética , Factores de Transcripción/genética , Anciano , Anciano de 80 o más Años , Empalme Alternativo , Línea Celular Tumoral , Cromosomas Humanos Par 3 , Femenino , Perfilación de la Expresión Génica , Regulación Leucémica de la Expresión Génica , Reordenamiento Génico , Humanos , Estimación de Kaplan-Meier , Leucemia Mieloide Aguda/mortalidad , Proteína del Locus del Complejo MDS1 y EV11 , Masculino , Persona de Mediana Edad , PronósticoRESUMEN
For millions of years, endogenous retroelements have remained transcriptionally silent within mammalian genomes by epigenetic mechanisms. Modern anticancer therapies targeting the epigenetic machinery awaken retroelement expression, inducing antiviral responses that eliminate tumors through mechanisms not completely understood. Here, we find that massive binding of epigenetically activated retroelements by RIG-I and MDA5 viral sensors promotes ATP hydrolysis and depletes intracellular energy, driving tumor killing independently of immune signaling. Energy depletion boosts compensatory ATP production by switching glycolysis to mitochondrial oxidative phosphorylation, thereby reversing the Warburg effect. However, hyperfunctional succinate dehydrogenase in mitochondrial electron transport chain generates excessive oxidative stress that unleashes RIP1-mediated necroptosis. To maintain ATP generation, hyperactive mitochondrial membrane blocks intrinsic apoptosis by increasing BCL2 dependency. Accordingly, drugs targeting BCL2 family proteins and epigenetic inhibitors yield synergistic responses in multiple cancer types. Thus, epigenetic therapy kills cancer cells by rewiring mitochondrial metabolism upon retroelement activation, which primes mitochondria to apoptosis by BH3-mimetics. SIGNIFICANCE: The state of viral mimicry induced by epigenetic therapies in cancer cells remodels mitochondrial metabolism and drives caspase-independent tumor cell death, which sensitizes to BCL2 inhibitor drugs. This novel mechanism underlies clinical efficacy of hypomethylating agents and venetoclax in acute myeloid leukemia, suggesting similar combination therapies for other incurable cancers.This article is highlighted in the In This Issue feature, p. 995.
Asunto(s)
Antineoplásicos/farmacología , Epigénesis Genética/efectos de los fármacos , Mitocondrias/efectos de los fármacos , Neoplasias/tratamiento farmacológico , Apoptosis/efectos de los fármacos , Línea Celular Tumoral , HumanosRESUMEN
Transgenic expression of the abnormal products of acute myeloid leukemia-associated (AML-associated) primary chromosomal translocations in hematopoietic stem/progenitor cells initiates leukemogenesis in mice, yet additional mutations are needed for leukemia development. We report here aberrant expression of PR domain containing 16 (PRDM16) in AML cells with either translocations of 1p36 or normal karyotype. These carried, respectively, relatively high prevalence of mutations in the TP53 tumor suppressor gene and in the nucleophosmin (NPM) gene, which regulates p53. Two protein isoforms are expressed from PRDM16, which differ in the presence or absence of the PR domain. Overexpression of the short isoform, sPRDM16, in mouse bone marrow induced AML with full penetrance, but only in the absence of p53. The mouse leukemias were characterized by multilineage cellular abnormalities and megakaryocyte dysplasia, a common feature of human AMLs with 1p36 translocations or NPM mutations. Overexpression of sPRDM16 increased the pool of HSCs in vivo, and in vitro blocked myeloid differentiation and prolonged progenitor life span. Loss of p53 augmented the effects of sPRDM16 on stem cell number and induced immortalization of progenitors. Thus, overexpression of sPRDM16 induces abnormal growth of stem cells and progenitors and cooperates with disruption of the p53 pathway in the induction of myeloid leukemia.
Asunto(s)
Transformación Celular Neoplásica/metabolismo , Proteínas de Unión al ADN/biosíntesis , Células Madre Hematopoyéticas/metabolismo , Leucemia Mieloide Aguda/metabolismo , Células Madre Neoplásicas/metabolismo , Factores de Transcripción/biosíntesis , Proteína p53 Supresora de Tumor , Animales , Médula Ósea/metabolismo , Médula Ósea/patología , Diferenciación Celular/genética , Transformación Celular Neoplásica/genética , Transformación Celular Neoplásica/patología , Senescencia Celular/genética , Proteínas de Unión al ADN/genética , Regulación Leucémica de la Expresión Génica , Células Madre Hematopoyéticas/patología , Humanos , Leucemia Mieloide Aguda/genética , Leucemia Mieloide Aguda/patología , Ratones , Ratones Noqueados , Células Madre Neoplásicas/patología , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Nucleofosmina , Isoformas de Proteínas/biosíntesis , Isoformas de Proteínas/genética , Estructura Terciaria de Proteína/genética , Factores de Transcripción/genética , Translocación Genética , Proteína p53 Supresora de Tumor/genéticaRESUMEN
The MYC transcription factor is one of the best characterized PP2A substrates. Deregulation of the MYC oncogene, along with inactivation of PP2A, are two frequent events in cancer. Both proteins are essential regulators of cell proliferation, apoptosis, and differentiation, and they, directly and indirectly, regulate each other's activity. Studies in cancer suggest that targeting the MYC/PP2A network is an achievable strategy for the clinic. Here, we focus on and discuss the role of MYC and PP2A in myeloid leukemias.
Asunto(s)
Progresión de la Enfermedad , Leucemia Mieloide/metabolismo , Leucemia Mieloide/patología , Proteína Fosfatasa 2/metabolismo , Proteínas Proto-Oncogénicas c-myc/metabolismo , Animales , Humanos , Terapia Molecular Dirigida , Transducción de SeñalRESUMEN
Acute myeloid leukemia (AML) is an aggressive disease associated with very poor prognosis. Most patients are older than 60 years, and in this group only 5-15% of cases survive over 5 years. Therefore, it is urgent to develop more effective targeted therapies. Inactivation of protein phosphatase 2â¯A (PP2A) is a recurrent event in AML, and overexpression of its endogenous inhibitor SET is detected in ~30% of patients. The PP2A activating drug FTY720 has potent anti-leukemic effects; nevertheless, FTY720 induces cardiotoxicity at the anti-neoplastic dose. Here, we have developed a series of non-phosphorylable FTY720 analogues as a new therapeutic strategy for AML. Our results show that the lead compound CM-1231 re-activates PP2A by targeting SET-PP2A interaction, inhibiting cell proliferation and promoting apoptosis in AML cell lines and primary patient samples. Notably, CM-1231 did not induce cardiac toxicity, unlike FTY720, in zebrafish models, and reduced the invasion and aggressiveness of AML cells more than FTY720 in zebrafish xenograft models. In conclusion, CM-1231 is safer and more effective than FTY720; therefore, this compound could represent a novel and promising approach for treating AML patients with SET overexpression.
Asunto(s)
Cardiotoxicidad/prevención & control , Proteínas de Unión al ADN/metabolismo , Clorhidrato de Fingolimod/administración & dosificación , Chaperonas de Histonas/metabolismo , Leucemia Mieloide Aguda/tratamiento farmacológico , Proteína Fosfatasa 2/metabolismo , Adulto , Anciano , Anciano de 80 o más Años , Animales , Apoptosis/efectos de los fármacos , Cardiotoxicidad/etiología , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Femenino , Clorhidrato de Fingolimod/análogos & derivados , Clorhidrato de Fingolimod/toxicidad , Frecuencia Cardíaca/efectos de los fármacos , Humanos , Leucemia Mieloide Aguda/patología , Masculino , Persona de Mediana Edad , Unión Proteica/efectos de los fármacos , Pruebas de Toxicidad Aguda , Ensayos Antitumor por Modelo de Xenoinjerto , Pez CebraRESUMEN
Acute myeloid leukemia (AML) is an aggressive hematologic malignancy. Although novel emerging drugs are available, the overall prognosis remains poor and new therapeutic approaches are required. PP2A phosphatase is a key regulator of cell homeostasis and is recurrently inactivated in AML. The anticancer activity of several PP2A-activating drugs (e.g., FTY720) depends on their interaction with the SET oncoprotein, an endogenous PP2A inhibitor that is overexpressed in 30% of AML cases. Elucidation of SET regulatory mechanisms may therefore provide novel targeted therapies for SET-overexpressing AMLs. Here, we show that upregulation of protein kinase p38ß is a common event in AML. We provide evidence that p38ß potentiates SET-mediated PP2A inactivation by two mechanisms: facilitating SET cytoplasmic translocation through CK2 phosphorylation, and directly binding to and stabilizing the SET protein. We demonstrate the importance of this new regulatory mechanism in primary AML cells from patients and in zebrafish xenograft models. Accordingly, combination of the CK2 inhibitor CX-4945, which retains SET in the nucleus, and FTY720, which disrupts the SET-PP2A binding in the cytoplasm, significantly reduces the viability and migration of AML cells. In conclusion, we show that the p38ß/CK2/SET axis represents a new potential therapeutic pathway in AML patients with SET-dependent PP2A inactivation.
Asunto(s)
Proteínas de Unión al ADN/metabolismo , Chaperonas de Histonas/metabolismo , Leucemia Mieloide Aguda/metabolismo , Proteína Fosfatasa 2/metabolismo , Animales , Humanos , Leucemia Mieloide Aguda/enzimología , Leucemia Mieloide Aguda/genética , Persona de Mediana Edad , Transducción de Señal , Transfección , Pez CebraRESUMEN
LB100 does not sensitize CML stem cells to tyrosine kinase inhibitor-induced apoptosis.
Asunto(s)
Leucemia Mielógena Crónica BCR-ABL Positiva , Apoptosis/efectos de los fármacos , Resistencia a Antineoplásicos/efectos de los fármacos , Proteínas de Fusión bcr-abl , Humanos , Células Madre Neoplásicas/efectos de los fármacos , Inhibidores de Proteínas QuinasasRESUMEN
BACKGROUND: Activating NOTCH1 mutations are common in T-cell acute lymphoblastic leukemia. Inhibition of NOTCH1 signaling with gamma-secretase inhibitors causes cell cycle block, but only after treatment for several days. We further documented the effects of gamma-secretase inhibitor treatment on T-cell acute lymphoblastic leukemia cell lines and tested whether combining gamma-secretase inhibitors with other anti-cancer drugs offers a therapeutic advantage. DESIGN AND METHODS: The effect of gamma-secretase inhibitor treatment and combinations of gamma-secretase inhibitors with chemotherapy or glucocorticoids was assessed on T-cell acute lymphoblastic leukemia cell lines. We sequenced NOTCH1 in T-cell acute lymphoblastic leukemia cases with ABL1 fusions and tested combinations of gamma-secretase inhibitors and the ABL1 inhibitor imatinib in a T-cell acute lymphoblastic leukemia cell line. RESULTS: gamma-secretase inhibitor treatment for 5-7 days reversibly inhibited cell proliferation, caused cell cycle block in sensitive T-cell acute lymphoblastic leukemia cell lines, and caused differentiation of some T-cell acute lymphoblastic leukemia cell lines. Treatment for 14 days or longer was required to induce significant apoptosis. The cytotoxic effects of the chemotherapeutic agent vincristine were not significantly enhanced by addition of gamma-secretase inhibitors to T-cell acute lymphoblastic leukemia cell lines, but gamma-secretase inhibitor treatment sensitized cells to the effect of dexamethasone. NOTCH1 mutations were identified in all T-cell acute lymphoblastic leukemia patients with ABL1 fusions and in a T-cell acute lymphoblastic leukemia cell line expressing NUP214-ABL1. In this cell line, the anti-proliferative effect of imatinib was increased by pre-treatment with gamma-secretase inhibitors. CONCLUSIONS: Short-term treatment of T-cell acute lymphoblastic leukemia cell lines with gamma-secretase inhibitors had limited effects on cell proliferation and survival. Combinations of gamma-secretase inhibitors with other drugs may be required to obtain efficient therapeutic effects in T-cell acute lymphoblastic leukemia, and not all combinations may be useful.