RESUMO
B cell acute lymphoblastic leukemia (B-ALL) is a multistep disease characterized by the hierarchical acquisition of genetic alterations. However, the question of how a primary oncogene reprograms stem cell-like properties in committed B cells and leads to a preneoplastic population remains unclear. Here, we used the PAX5::ELN oncogenic model to demonstrate a causal link between the differentiation blockade, the self-renewal, and the emergence of preleukemic stem cells (pre-LSCs). We show that PAX5::ELN disrupts the differentiation of preleukemic cells by enforcing the IL7r/JAK-STAT pathway. This disruption is associated with the induction of rare and quiescent pre-LSCs that sustain the leukemia-initiating activity, as assessed using the H2B-GFP model. Integration of transcriptomic and chromatin accessibility data reveals that those quiescent pre-LSCs lose B cell identity and reactivate an immature molecular program, reminiscent of human B-ALL chemo-resistant cells. Finally, our transcriptional regulatory network reveals the transcription factor EGR1 as a strong candidate to control quiescence/resistance of PAX5::ELN pre-LSCs as well as of blasts from human B-ALL.
Assuntos
Linfoma de Burkitt , Leucemia , Humanos , Janus Quinases , Fatores de Transcrição STAT , Transdução de Sinais , Células-TroncoRESUMO
Early T-cell development is precisely controlled by E proteins, that indistinguishably include HEB/TCF12 and E2A/TCF3 transcription factors, together with NOTCH1 and pre-T cell receptor (TCR) signalling. Importantly, perturbations of early T-cell regulatory networks are implicated in leukemogenesis. NOTCH1 gain of function mutations invariably lead to T-cell acute lymphoblastic leukemia (T-ALL), whereas inhibition of E proteins accelerates leukemogenesis. Thus, NOTCH1, pre-TCR, E2A and HEB functions are intertwined, but how these pathways contribute individually or synergistically to leukemogenesis remain to be documented. To directly address these questions, we leveraged Cd3e-deficient mice in which pre-TCR signaling and progression through ß-selection is abrogated to dissect and decouple the roles of pre-TCR, NOTCH1, E2A and HEB in SCL/TAL1-induced T-ALL, via the use of Notch1 gain of function transgenic (Notch1ICtg) and Tcf12+/- or Tcf3+/- heterozygote mice. As a result, we now provide evidence that both HEB and E2A restrain cell proliferation at the ß-selection checkpoint while the clonal expansion of SCL-LMO1-induced pre-leukemic stem cells in T-ALL is uniquely dependent on Tcf12 gene dosage. At the molecular level, HEB protein levels are decreased via proteasomal degradation at the leukemic stage, pointing to a reversible loss of function mechanism. Moreover, in SCL-LMO1-induced T-ALL, loss of one Tcf12 allele is sufficient to bypass pre-TCR signaling which is required for Notch1 gain of function mutations and for progression to T-ALL. In contrast, Tcf12 monoallelic deletion does not accelerate Notch1IC-induced T-ALL, indicating that Tcf12 and Notch1 operate in the same pathway. Finally, we identify a tumor suppressor gene set downstream of HEB, exhibiting significantly lower expression levels in pediatric T-ALL compared to B-ALL and brain cancer samples, the three most frequent pediatric cancers. In summary, our results indicate a tumor suppressor function of HEB/TCF12 in T-ALL to mitigate cell proliferation controlled by NOTCH1 in pre-leukemic stem cells and prevent NOTCH1-driven progression to T-ALL.
Assuntos
Leucemia-Linfoma Linfoblástico de Células T Precursoras , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Humanos , Camundongos , Leucemia-Linfoma Linfoblástico de Células T Precursoras/genética , Proteínas Proto-Oncogênicas/metabolismo , Receptor Notch1/genética , Receptor Notch1/metabolismo , Receptores de Antígenos de Linfócitos T , Proteína 1 de Leucemia Linfocítica Aguda de Células T , Linfócitos T/metabolismo , Fatores de Transcrição/metabolismoRESUMO
Myelodysplastic syndromes (MDS) represent a heterogeneous group of clonal hematopoietic stem cell disorders characterized by ineffective hematopoiesis leading to peripheral cytopenias and in a substantial proportion of cases to acute myeloid leukemia. The deletion of the long arm of chromosome 11, del(11q), is a rare but recurrent clonal event in MDS. Here, we detail the largest series of 113 cases of MDS and myelodysplastic syndromes/myeloproliferative neoplasms (MDS/MPN) harboring a del(11q) analyzed at clinical, cytological, cytogenetic, and molecular levels. Female predominance, a survival prognosis similar to other MDS, a low monocyte count, and dysmegakaryopoiesis were the specific clinical and cytological features of del(11q) MDS. In most cases, del(11q) was isolated, primary and interstitial encompassing the 11q22-23 region containing ATM, KMT2A, and CBL genes. The common deleted region at 11q23.2 is centered on an intergenic region between CADM1 (also known as Tumor Suppressor in Lung Cancer 1) and NXPE2. CADM1 was expressed in all myeloid cells analyzed in contrast to NXPE2. At the functional level, the deletion of Cadm1 in murine Lineage-Sca1+Kit+ cells modifies the lymphoid-to-myeloid ratio in bone marrow, although not altering their multilineage hematopoietic reconstitution potential after syngenic transplantation. Together with the frequent simultaneous deletions of KMT2A, ATM, and CBL and mutations of ASXL1, SF3B1, and CBL, we show that CADM1 may be important in the physiopathology of the del(11q) MDS, extending its role as tumor-suppressor gene from solid tumors to hematopoietic malignancies.
Assuntos
Molécula 1 de Adesão Celular/metabolismo , Leucemia Mieloide Aguda , Síndromes Mielodisplásicas , Animais , Molécula 1 de Adesão Celular/genética , Deleção Cromossômica , Cromossomos Humanos Par 11 , Feminino , Genes Supressores de Tumor , Humanos , Leucemia Mieloide Aguda/genética , Camundongos , Síndromes Mielodisplásicas/genética , Síndromes Mielodisplásicas/patologiaRESUMO
Our understanding of the hierarchical structure of acute leukemia has yet to be fully translated into therapeutic approaches. Indeed, chemotherapy still has to take into account the possibility that leukemia-initiating cells may have a distinct chemosensitivity profile compared to the bulk of the tumor, and therefore are spared by the current treatment, causing the relapse of the disease. Therefore, the identification of the cell-of-origin of leukemia remains a longstanding question and an exciting challenge in cancer research of the last few decades. With a particular focus on acute lymphoblastic leukemia, we present in this review the previous and current concepts exploring the phenotypic, genetic and functional heterogeneity in patients. We also discuss the benefits of using engineered mouse models to explore the early steps of leukemia development and to identify the biological mechanisms driving the emergence of leukemia-initiating cells. Finally, we describe the major prospects for the discovery of new therapeutic strategies that specifically target their aberrant stem cell-like functions.
Assuntos
Mutação em Linhagem Germinativa , Fator de Transcrição PAX5/genética , Leucemia-Linfoma Linfoblástico de Células Precursoras B/genética , Adulto , Criança , Feminino , Predisposição Genética para Doença , Humanos , Masculino , Linhagem , Leucemia-Linfoma Linfoblástico de Células Precursoras B/congênito , Leucemia-Linfoma Linfoblástico de Células Precursoras B/patologiaRESUMO
PAX5 is a well-known haploinsufficient tumor suppressor gene in human B-cell precursor acute lymphoblastic leukemia (B-ALL) and is involved in various chromosomal translocations that fuse a part of PAX5 with other partners. However, the role of PAX5 fusion proteins in B-ALL initiation and transformation is ill-known. We previously reported a new recurrent t(7;9)(q11;p13) chromosomal translocation in human B-ALL that juxtaposed PAX5 to the coding sequence of elastin (ELN). To study the function of the resulting PAX5-ELN fusion protein in B-ALL development, we generated a knockin mouse model in which the PAX5-ELN transgene is expressed specifically in B cells. PAX5-ELN-expressing mice efficiently developed B-ALL with an incidence of 80%. Leukemic transformation was associated with recurrent secondary mutations on Ptpn11, Kras, Pax5, and Jak3 genes affecting key signaling pathways required for cell proliferation. Our functional studies demonstrate that PAX5-ELN affected B-cell development in vitro and in vivo featuring an aberrant expansion of the pro-B cell compartment at the preleukemic stage. Finally, our molecular and computational approaches identified PAX5-ELN-regulated gene candidates that establish the molecular bases of the preleukemic state to drive B-ALL initiation. Hence, our study provides a new in vivo model of human B-ALL and strongly implicates PAX5 fusion proteins as potent oncoproteins in leukemia development.
Assuntos
Elastina/genética , Proteínas de Fusão Oncogênica/genética , Fator de Transcrição PAX5/genética , Leucemia-Linfoma Linfoblástico de Células Precursoras/genética , Leucemia-Linfoma Linfoblástico de Células Precursoras/patologia , Animais , Linfócitos B/patologia , Linfócitos B/fisiologia , Elastina/metabolismo , Regulação Leucêmica da Expressão Gênica , Técnicas de Introdução de Genes , Janus Quinase 3/genética , Camundongos Transgênicos , Mutação , Neoplasias Experimentais , Proteínas de Fusão Oncogênica/metabolismo , Fator de Transcrição PAX5/metabolismo , Proteína Tirosina Fosfatase não Receptora Tipo 11/genética , Proteínas Proto-Oncogênicas p21(ras)/genéticaRESUMO
Pax5 is the guardian of the B cell identity since it primes or enhances the expression of B cell specific genes and concomitantly represses the expression of B cell inappropriate genes. The tight regulation of Pax5 is therefore required for an efficient B cell differentiation. A defect in its dosage can translate into immunodeficiency or malignant disorders such as leukemia or lymphoma. Pax5 is expressed from two different promoters encoding two isoforms that only differ in the sequence of their first alternative exon. Very little is known regarding the role of the two isoforms during B cell differentiation and the regulation of their expression. Our work aims to characterize the mechanisms of regulation of the expression balance of these two isoforms and their implication in the B cell differentiation process using murine ex vivo analyses. We show that these two isoforms are differentially regulated but have equivalent function during early B cell differentiation and may have functional differences after B cell activation. The tight control of their expression may thus reflect a way to finely tune Pax5 dosage during B cell differentiation process.
RESUMO
Current chemotherapies for T cell acute lymphoblastic leukemia (T-ALL) efficiently reduce tumor mass. Nonetheless, disease relapse attributed to survival of preleukemic stem cells (pre-LSCs) is associated with poor prognosis. Herein, we provide direct evidence that pre-LSCs are much less chemosensitive to existing chemotherapy drugs than leukemic blasts because of a distinctive lower proliferative state. Improving therapies for T-ALL requires the development of strategies to target pre-LSCs that are absolutely dependent on their microenvironment. Therefore, we designed a robust protocol for high-throughput screening of compounds that target primary pre-LSCs maintained in a niche-like environment, on stromal cells that were engineered for optimal NOTCH1 activation. The multiparametric readout takes into account the intrinsic complexity of primary cells in order to specifically monitor pre-LSCs, which were induced here by the SCL/TAL1 and LMO1 oncogenes. We screened a targeted library of compounds and determined that the estrogen derivative 2-methoxyestradiol (2-ME2) disrupted both cell-autonomous and non-cell-autonomous pathways. Specifically, 2-ME2 abrogated pre-LSC viability and self-renewal activity in vivo by inhibiting translation of MYC, a downstream effector of NOTCH1, and preventing SCL/TAL1 activity. In contrast, normal hematopoietic stem/progenitor cells remained functional. These results illustrate how recapitulating tissue-like properties of primary cells in high-throughput screening is a promising avenue for innovation in cancer chemotherapy.
Assuntos
Estradiol/análogos & derivados , Células-Tronco Neoplásicas/metabolismo , Leucemia-Linfoma Linfoblástico de Células Precursoras/tratamento farmacológico , Leucemia-Linfoma Linfoblástico de Células Precursoras/metabolismo , Microambiente Tumoral/efeitos dos fármacos , 2-Metoxiestradiol , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Estradiol/farmacologia , Humanos , Células Jurkat , Proteínas com Domínio LIM/genética , Proteínas com Domínio LIM/metabolismo , Camundongos , Células-Tronco Neoplásicas/patologia , Leucemia-Linfoma Linfoblástico de Células Precursoras/genética , Leucemia-Linfoma Linfoblástico de Células Precursoras/patologia , Proteínas Proto-Oncogênicas/genética , Proteínas Proto-Oncogênicas/metabolismo , Receptor Notch1/genética , Receptor Notch1/metabolismo , Proteína 1 de Leucemia Linfocítica Aguda de Células T , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Microambiente Tumoral/genética , Ensaio Tumoral de Célula-Tronco , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
The molecular determinants that render specific populations of normal cells susceptible to oncogenic reprogramming into self-renewing cancer stem cells are poorly understood. Here, we exploit T-cell acute lymphoblastic leukemia (T-ALL) as a model to define the critical initiating events in this disease. First, thymocytes that are reprogrammed by the SCL and LMO1 oncogenic transcription factors into self-renewing pre-leukemic stem cells (pre-LSCs) remain non-malignant, as evidenced by their capacities to generate functional T cells. Second, we provide strong genetic evidence that SCL directly interacts with LMO1 to activate the transcription of a self-renewal program coordinated by LYL1. Moreover, LYL1 can substitute for SCL to reprogram thymocytes in concert with LMO1. In contrast, inhibition of E2A was not sufficient to substitute for SCL, indicating that thymocyte reprogramming requires transcription activation by SCL-LMO1. Third, only a specific subset of normal thymic cells, known as DN3 thymocytes, is susceptible to reprogramming. This is because physiological NOTCH1 signals are highest in DN3 cells compared to other thymocyte subsets. Consistent with this, overexpression of a ligand-independent hyperactive NOTCH1 allele in all immature thymocytes is sufficient to sensitize them to SCL-LMO1, thereby increasing the pool of self-renewing cells. Surprisingly, hyperactive NOTCH1 cannot reprogram thymocytes on its own, despite the fact that NOTCH1 is activated by gain of function mutations in more than 55% of T-ALL cases. Rather, elevating NOTCH1 triggers a parallel pathway involving Hes1 and Myc that dramatically enhances the activity of SCL-LMO1 We conclude that the acquisition of self-renewal and the genesis of pre-LSCs from thymocytes with a finite lifespan represent a critical first event in T-ALL. Finally, LYL1 and LMO1 or LMO2 are co-expressed in most human T-ALL samples, except the cortical T subtype. We therefore anticipate that the self-renewal network described here may be relevant to a majority of human T-ALL.
Assuntos
Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Reprogramação Celular , Proteínas com Domínio LIM/metabolismo , Proteínas Nucleares/metabolismo , Proteínas Proto-Oncogênicas/metabolismo , Receptor Notch1/metabolismo , Timócitos/citologia , Fatores de Transcrição/metabolismo , Sequência de Aminoácidos , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Proliferação de Células , Transformação Celular Neoplásica , Modelos Animais de Doenças , Regulação Neoplásica da Expressão Gênica , Loci Gênicos , Proteínas com Domínio LIM/genética , Camundongos , Camundongos Knockout , Dados de Sequência Molecular , Mutação , Proteínas de Neoplasias/genética , Proteínas de Neoplasias/metabolismo , Proteínas Nucleares/genética , Leucemia-Linfoma Linfoblástico de Células T Precursoras/genética , Regiões Promotoras Genéticas , Proteínas Proto-Oncogênicas/genética , Receptor Notch1/genética , Proteína 1 de Leucemia Linfocítica Aguda de Células T , Fatores de Transcrição/genética , Ativação TranscricionalRESUMO
Development of novel therapies is critical for T-cell acute leukaemia (T-ALL). Here, we investigated the effect of inhibiting the MAPK/MEK/ERK pathway on T-ALL cell growth. Unexpectedly, MEK inhibitors (MEKi) enhanced growth of 70% of human T-ALL cell samples cultured on stromal cells independently of NOTCH activation and maintained their ability to propagate in vivo. Similar results were obtained when T-ALL cells were cultured with ERK1/2-knockdown stromal cells or with conditioned medium from MEKi-treated stromal cells. Microarray analysis identified interleukin 18 (IL-18) as transcriptionally up-regulated in MEKi-treated MS5 cells. Recombinant IL-18 promoted T-ALL growth in vitro, whereas the loss of function of IL-18 receptor in T-ALL blast cells decreased blast proliferation in vitro and in NSG mice. The NFKB pathway that is downstream to IL-18R was activated by IL-18 in blast cells. IL-18 circulating levels were increased in T-ALL-xenografted mice and also in T-ALL patients in comparison with controls. This study uncovers a novel role of the pro-inflammatory cytokine IL-18 and outlines the microenvironment involvement in human T-ALL development.
Assuntos
Interleucina-18/imunologia , Leucemia-Linfoma Linfoblástico de Células T Precursoras/imunologia , Células Estromais/imunologia , Animais , Células da Medula Óssea/citologia , Células da Medula Óssea/metabolismo , Células da Medula Óssea/patologia , Linhagem Celular , Linhagem Celular Tumoral , Proliferação de Células , Regulação Leucêmica da Expressão Gênica , Inativação Gênica , Humanos , Interleucina-18/sangue , Interleucina-18/genética , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Camundongos , Camundongos Endogâmicos NOD , Leucemia-Linfoma Linfoblástico de Células T Precursoras/sangue , Leucemia-Linfoma Linfoblástico de Células T Precursoras/genética , Leucemia-Linfoma Linfoblástico de Células T Precursoras/patologia , Células Estromais/citologia , Células Estromais/metabolismo , Células Estromais/patologia , Linfócitos T/imunologia , Linfócitos T/metabolismo , Linfócitos T/patologiaRESUMO
SCL/TAL1, a tissue-specific transcription factor of the basic helix-loop-helix family, and c-Kit, a tyrosine kinase receptor, control hematopoietic stem cell survival and quiescence. Here we report that SCL levels are limiting for the clonal expansion of Kit⺠multipotent and erythroid progenitors. In addition, increased SCL expression specifically enhances the sensitivity of these progenitors to steel factor (KIT ligand) without affecting interleukin-3 response, whereas a DNA-binding mutant antagonizes KIT function and induces apoptosis in progenitors. Furthermore, a twofold increase in SCL levels in mice bearing a hypomorphic Kit allele (W41/41) corrects their hematocrits and deficiencies in erythroid progenitor numbers. At the molecular level, we found that SCL and c-Kit signaling control a common gene expression signature, of which 19 genes are associated with apoptosis. Half of those were decreased in purified megakaryocyte/erythroid progenitors (MEPs) from W41/41 mice and rescued by the SCL transgene. We conclude that Scl operates downstream of Kit to support the survival of MEPs. Finally, higher SCL expression upregulates Kit in normal bone marrow cells and increases chimerism after bone marrow transplantation, indicating that Scl is also upstream of Kit. We conclude that Scl and Kit establish a positive feedback loop in multipotent and MEPs.
Assuntos
Apoptose , Fatores de Transcrição Hélice-Alça-Hélice Básicos/fisiologia , Biomarcadores/metabolismo , Células Precursoras Eritroides/metabolismo , Células-Tronco Multipotentes/metabolismo , Proteínas Proto-Oncogênicas c-kit/metabolismo , Proteínas Proto-Oncogênicas/fisiologia , Animais , Western Blotting , Proliferação de Células , Células Cultivadas , Imunoprecipitação da Cromatina , Células Precursoras Eritroides/citologia , Citometria de Fluxo , Perfilação da Expressão Gênica , Humanos , Técnicas Imunoenzimáticas , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Células-Tronco Multipotentes/citologia , Análise de Sequência com Séries de Oligonucleotídeos , Proteínas Proto-Oncogênicas c-kit/genética , RNA Mensageiro/genética , Reação em Cadeia da Polimerase em Tempo Real , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Fator de Células-Tronco , Proteína 1 de Leucemia Linfocítica Aguda de Células TRESUMO
Acute megakaryoblastic leukemia (AMKL) is a heterogeneous disease generally associated with poor prognosis. Gene expression profiles indicate the existence of distinct molecular subgroups, and several genetic alterations have been characterized in the past years, including the t(1;22)(p13;q13) and the trisomy 21 associated with GATA1 mutations. However, the majority of patients do not present with known mutations, and the limited access to primary patient leukemic cells impedes the efficient development of novel therapeutic strategies. In this study, using a xenotransplantation approach, we have modeled human pediatric AMKL in immunodeficient mice. Analysis of high-throughput RNA sequencing identified recurrent fusion genes defining new molecular subgroups. One subgroup of patients presented with MLL or NUP98 fusion genes leading to up-regulation of the HOX A cluster genes. A novel CBFA2T3-GLIS2 fusion gene resulting from a cryptic inversion of chromosome 16 was identified in another subgroup of 31% of non-Down syndrome AMKL and strongly associated with a gene expression signature of Hedgehog pathway activation. These molecular data provide useful markers for the diagnosis and follow up of patients. Finally, we show that AMKL xenograft models constitute a relevant in vivo preclinical screening platform to validate the efficacy of novel therapies such as Aurora A kinase inhibitors.
Assuntos
Genômica/métodos , Leucemia Megacarioblástica Aguda/tratamento farmacológico , Leucemia Megacarioblástica Aguda/genética , Ensaios Antitumorais Modelo de Xenoenxerto , 1-(5-Isoquinolinasulfonil)-2-Metilpiperazina/análogos & derivados , 1-(5-Isoquinolinasulfonil)-2-Metilpiperazina/farmacologia , Idoso , Sequência de Aminoácidos , Animais , Aurora Quinase A , Aurora Quinases , Azepinas/farmacologia , Sequência de Bases , Feminino , Perfilação da Expressão Gênica , Sequenciamento de Nucleotídeos em Larga Escala/métodos , Humanos , Lactente , Estimativa de Kaplan-Meier , Fatores de Transcrição Kruppel-Like/genética , Leucemia Megacarioblástica Aguda/patologia , Masculino , Camundongos , Camundongos SCID , Pessoa de Meia-Idade , Dados de Sequência Molecular , Análise de Sequência com Séries de Oligonucleotídeos , Proteínas de Fusão Oncogênica/genética , Proteínas Serina-Treonina Quinases/antagonistas & inibidores , Pirimidinas/farmacologia , Proteínas Repressoras/genéticaRESUMO
The mechanism by which cells decide to skip mitosis to become polyploid is largely undefined. Here we used a high-content image-based screen to identify small-molecule probes that induce polyploidization of megakaryocytic leukemia cells and serve as perturbagens to help understand this process. Our study implicates five networks of kinases that regulate the switch to polyploidy. Moreover, we find that dimethylfasudil (diMF, H-1152P) selectively increased polyploidization, mature cell-surface marker expression, and apoptosis of malignant megakaryocytes. An integrated target identification approach employing proteomic and shRNA screening revealed that a major target of diMF is Aurora kinase A (AURKA). We further find that MLN8237 (Alisertib), a selective inhibitor of AURKA, induced polyploidization and expression of mature megakaryocyte markers in acute megakaryocytic leukemia (AMKL) blasts and displayed potent anti-AMKL activity in vivo. Our findings provide a rationale to support clinical trials of MLN8237 and other inducers of polyploidization and differentiation in AMKL.
Assuntos
Azepinas/farmacologia , Descoberta de Drogas , Leucemia Megacarioblástica Aguda/tratamento farmacológico , Megacariócitos/metabolismo , Poliploidia , Pirimidinas/farmacologia , Bibliotecas de Moléculas Pequenas , 1-(5-Isoquinolinasulfonil)-2-Metilpiperazina/análogos & derivados , 1-(5-Isoquinolinasulfonil)-2-Metilpiperazina/farmacologia , Animais , Aurora Quinase A , Aurora Quinases , Diferenciação Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Humanos , Leucemia Megacarioblástica Aguda/genética , Megacariócitos/citologia , Megacariócitos/patologia , Camundongos , Camundongos Endogâmicos C57BL , Mapas de Interação de Proteínas , Proteínas Serina-Treonina Quinases/antagonistas & inibidores , Proteínas Serina-Treonina Quinases/metabolismo , Quinases Associadas a rho/metabolismoRESUMO
Genomic studies in human acute lymphoblastic leukemia (ALL) have revealed clonal heterogeneity at diagnosis and clonal evolution at relapse. In this study, we used genome-wide profiling to compare human T cell ALL samples at the time of diagnosis and after engraftment (xenograft) into immunodeficient recipient mice. Compared with paired diagnosis samples, the xenograft leukemia often contained additional genomic lesions in established human oncogenes and/or tumor suppressor genes. Mimicking such genomic lesions by short hairpin RNA-mediated knockdown in diagnosis samples conferred a selective advantage in competitive engraftment experiments, demonstrating that additional lesions can be drivers of increased leukemia-initiating activity. In addition, the xenograft leukemias appeared to arise from minor subclones existing in the patient at diagnosis. Comparison of paired diagnosis and relapse samples showed that, with regard to genetic lesions, xenograft leukemias more frequently more closely resembled relapse samples than bulk diagnosis samples. Moreover, a cell cycle- and mitosis-associated gene expression signature was present in xenograft and relapse samples, and xenograft leukemia exhibited diminished sensitivity to drugs. Thus, the establishment of human leukemia in immunodeficient mice selects and expands a more aggressive malignancy, recapitulating the process of relapse in patients. These findings may contribute to the design of novel strategies to prevent or treat relapse.
Assuntos
Leucemia-Linfoma Linfoblástico de Células T Precursoras/genética , Animais , Ciclo Celular , Perfilação da Expressão Gênica , Humanos , Camundongos , Mitose , Transplante de Neoplasias , PTEN Fosfo-Hidrolase/fisiologia , Leucemia-Linfoma Linfoblástico de Células T Precursoras/patologia , Recidiva , Transplante HeterólogoAssuntos
Proliferação de Células , Genes Supressores de Tumor , Leucemia-Linfoma Linfoblástico de Células T Precursoras/genética , Leucemia-Linfoma Linfoblástico de Células T Precursoras/patologia , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Humanos , Camundongos , Proteínas Proto-Oncogênicas/genética , Proteína 1 de Leucemia Linfocítica Aguda de Células TRESUMO
TAL1 (also known as SCL) is expressed in >40% of human T cell acute lymphoblastic leukemias (T-ALLs). TAL1 encodes a basic helix-loop-helix transcription factor that can interfere with the transcriptional activity of E2A and HEB during T cell leukemogenesis; however, the oncogenic pathways directly activated by TAL1 are not characterized. In this study, we show that, in human TAL1-expressing T-ALL cell lines, TAL1 directly activates NKX3.1, a tumor suppressor gene required for prostate stem cell maintenance. In human T-ALL cell lines, NKX3.1 gene activation is mediated by a TAL1-LMO-Ldb1 complex that is recruited by GATA-3 bound to an NKX3.1 gene promoter regulatory sequence. TAL1-induced NKX3.1 activation is associated with suppression of HP1-α (heterochromatin protein 1 α) binding and opening of chromatin on the NKX3.1 gene promoter. NKX3.1 is necessary for T-ALL proliferation, can partially restore proliferation in TAL1 knockdown cells, and directly regulates miR-17-92. In primary human TAL1-expressing leukemic cells, the NKX3.1 gene is expressed independently of the Notch pathway, and its inactivation impairs proliferation. Finally, TAL1 or NKX3.1 knockdown abrogates the ability of human T-ALL cells to efficiently induce leukemia development in mice. These results suggest that tumor suppressor or oncogenic activity of NKX3.1 depends on tissue expression.
Assuntos
Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Proteínas de Homeodomínio/genética , Leucemia-Linfoma Linfoblástico de Células T Precursoras/genética , Proteínas Proto-Oncogênicas/genética , Fatores de Transcrição/genética , Proteínas Adaptadoras de Transdução de Sinal , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos/biossíntese , Linhagem Celular Tumoral , Proliferação de Células , Proteínas de Ligação a DNA/metabolismo , Fator de Transcrição GATA3/metabolismo , Técnicas de Silenciamento de Genes , Genes Supressores de Tumor , Proteínas de Homeodomínio/metabolismo , Humanos , Proteínas com Domínio LIM , Masculino , Metaloproteínas/metabolismo , Camundongos , Transplante de Neoplasias , Leucemia-Linfoma Linfoblástico de Células T Precursoras/metabolismo , Leucemia-Linfoma Linfoblástico de Células T Precursoras/patologia , Próstata/metabolismo , Próstata/patologia , Ligação Proteica , Proteínas Proto-Oncogênicas/biossíntese , Células-Tronco/fisiologia , Proteína 1 de Leucemia Linfocítica Aguda de Células T , Fatores de Transcrição/metabolismoRESUMO
Iodinated derivatives of verapamil were synthesized and tested as P-glycoprotein (Pgp)-mediated multidrug resistance (MDR) reversal agents. The ability of these compounds to revert MDR was evaluated on daunorubicin-resistant K562 cells, by measuring the intracellular accumulation of rhodamine 123, a fluorescent probe of Pgp transport activity. One of the investigated compounds (16c) was found to be a more potent MDR reversal agent than verapamil and cyclosporin A, used as reference molecules. Further in vitro studies showed that compound 16c restored daunorubicin activity and, when used alone, did not induce cell death, cell cycle perturbation and modification of calcium channel activity in comparison with verapamil.
Assuntos
Membro 1 da Subfamília B de Cassetes de Ligação de ATP/antagonistas & inibidores , Verapamil/análogos & derivados , Membro 1 da Subfamília B de Cassetes de Ligação de ATP/metabolismo , Animais , Bloqueadores dos Canais de Cálcio/farmacologia , Canais de Cálcio Tipo L/metabolismo , Ciclo Celular/efeitos dos fármacos , Ciclosporina/farmacologia , Daunorrubicina/farmacologia , Resistencia a Medicamentos Antineoplásicos , Sinergismo Farmacológico , Humanos , Células K562 , Masculino , Miócitos Cardíacos/efeitos dos fármacos , Miócitos Cardíacos/metabolismo , Ratos , Ratos Wistar , Rodamina 123/farmacocinética , Verapamil/farmacologiaRESUMO
Understanding the pathways that regulate the human T-cell acute lymphoblastic leukemia (T-ALL) initiating cells (T-LiC) activity has been hampered by the lack of biologic assays in which this human disease can be studied. Here we show that coculture of primary human T-ALL with a mouse stromal cell line expressing the NOTCH ligand delta-like-1 (DL1) reproducibly allowed maintenance of T-LiC and long-term growth of blast cells. Human T-ALL mutated or not on the NOTCH receptor required sustained activation of the NOTCH pathway via receptor/ligand interaction for growth and T-LiC activity. On the reverse, inhibition of the NOTCH pathway during primary cultures abolished in vitro cell growth and in vivo T-LiC activity. Altogether, these results demonstrate the major role of the NOTCH pathway activation in human T-ALL development and in the maintenance of leukemia-initiating cells.