RESUMO
The reintegration of excised signal joints resulting from human V(D)J recombination was described as a potent source of genomic instability in human lymphoid cancers. However, such molecular events have not been recurrently reported in clinical patient lymphoma/leukemia samples. Using a specifically designed NGS-capture pipeline, we here demonstrated the reintegration of T-cell receptor excision circles (TRECs) in 20/1533 (1.3%) patients with T-cell acute lymphoblastic leukemia (T-ALL) and T-cell lymphoblastic lymphoma (T-LBL). Remarkably, the reintegration of TREC recurrently targeted the tumor suppressor gene, ZFP36L2, in 17/20 samples. Thus, our data identified a new and hardly detectable mechanism of gene deregulation in lymphoid cancers providing new insights in human oncogenesis.
Assuntos
Carcinogênese , Leucemia-Linfoma Linfoblástico de Células T Precursoras , Humanos , Carcinogênese/genética , Transformação Celular Neoplásica/genética , Instabilidade Genômica , Células-Tronco Hematopoéticas , Leucemia-Linfoma Linfoblástico de Células T Precursoras/genética , Fatores de TranscriçãoRESUMO
BACKGROUND: Germline mutations in the ETV6 transcription factor gene are responsible for familial thrombocytopenia and leukemia predisposition syndrome. Although previous studies have shown that ETV6 plays an important role in megakaryocyte (MK) maturation and platelet formation, the mechanisms by which ETV6 dysfunction promotes thrombocytopenia remain unclear. OBJECTIVES: To decipher the transcriptional mechanisms and gene regulatory network linking ETV6 germline mutations and thrombocytopenia. METHODS: Presuming that ETV6 mutations result in selective effects at a particular cell stage, we applied single-cell RNA sequencing to understand gene expression changes during megakaryopoiesis in peripheral CD34+ cells from healthy controls and patients with ETV6-related thrombocytopenia. RESULTS: Analysis of gene expression and regulon activity revealed distinct clusters partitioned into 7 major cell stages: hematopoietic stem/progenitor cells, common-myeloid progenitors (CMPs), MK-primed CMPs, granulocyte-monocyte progenitors, MK-erythroid progenitors (MEPs), progenitor MKs/mature MKs, and platelet-like particles. We observed a differentiation trajectory in which MEPs developed directly from hematopoietic stem/progenitor cells and bypassed the CMP stage. ETV6 deficiency led to the development of aberrant cells as early as the MEP stage, which intensified at the progenitor MK/mature MK stage, with a highly deregulated core "ribosome biogenesis" pathway. Indeed, increased translation levels have been documented in patient CD34+-derived MKs with overexpression of ribosomal protein S6 and phosphorylated ribosomal protein S6 in both CD34+-derived MKs and platelets. Treatment of patient MKs with the ribosomal biogenesis inhibitor CX-5461 resulted in an increase in platelet-like particles. CONCLUSION: These findings provide novel insight into both megakaryopoiesis and the link among ETV6, translation, and platelet production.
Assuntos
Megacariócitos , Trombocitopenia , Humanos , Diferenciação Celular , Megacariócitos/metabolismo , Proteína S6 Ribossômica/metabolismo , Análise de Célula Única , Trombocitopenia/genética , Trombocitopenia/metabolismo , Trombopoese/genética , Antígenos CD34 , Variante 6 da Proteína do Fator de Translocação ETSRESUMO
PTEN (Phosphatase and TENsin homolog) is a well-known tumor suppressor involved in numerous types of cancer, including T-cell acute lymphoblastic leukemia (T-ALL). In human, loss-of-function mutations of PTEN are correlated to mature T-ALL expressing a T-cell receptor (TCR) at their cell surface. In accordance with human T-ALL, inactivation of Pten gene in mouse thymocytes induces TCRαß+ T-ALL development. Herein, we explored the functional interaction between TCRαß signaling and PTEN. First, we performed single-cell RNA sequencing (scRNAseq) of PTEN-deficient and PTEN-proficient thymocytes. Bioinformatic analysis of our scRNAseq data showed that pathological Ptendel thymocytes express, as expected, Myc transcript, whereas inference of pathway activity revealed that these Ptendel thymocytes display a lower calcium pathway activity score compared to their physiological counterparts. We confirmed this result using ex vivo calcium flux assay and showed that upon TCR activation tumor Ptendel blasts were unable to release calcium ions (Ca2+) from the endoplasmic reticulum to the cytosol. In order to understand such phenomena, we constructed a mathematical model centered on the mechanisms controlling the calcium flux, integrating TCR signal strength and PTEN interactions. This qualitative model displays a dynamical behavior coherent with the dynamics reported in the literature, it also predicts that PTEN affects positively IP3 (inositol 1,4,5-trisphosphate) receptors (ITPR). Hence, we analyzed Itpr expression and unraveled that ITPR proteins levels are reduced in PTEN-deficient tumor cells compared to physiological and leukemic PTEN-proficient cells. However, calcium flux and ITPR proteins expression are not defective in non-leukemic PTEN-deficient T cells indicating that beyond PTEN loss an additional alteration is required. Altogether, our study shows that ITPR/Calcium flux is a part of the oncogenic landscape shaped by PTEN loss and pinpoints a putative role of PTEN in the regulation of ITPR proteins in thymocytes, which remains to be characterized.
Assuntos
Sinalização do Cálcio/genética , PTEN Fosfo-Hidrolase/deficiência , Leucemia-Linfoma Linfoblástico de Células T Precursoras/genética , Leucemia-Linfoma Linfoblástico de Células T Precursoras/metabolismo , Receptores de Antígenos de Linfócitos T alfa-beta/metabolismo , Timócitos/metabolismo , Animais , Proliferação de Células/genética , Camundongos , Camundongos Transgênicos , PTEN Fosfo-Hidrolase/genética , Leucemia-Linfoma Linfoblástico de Células T Precursoras/patologia , Timócitos/patologiaRESUMO
In the thymus, T cell progenitors differentiate in order to generate naive T lymphocytes which migrate in the periphery where they will fulfill their function in the adaptive immune response. During thymopoiesis, genomic alterations in thymocytes can promote leukemia development. Among recurrent alteration is PTEN inactivation, which is associated to MYC overexpression. Herein, we used conditional Pten and Myc knockout mouse models and single-cell RNA-sequencing approach, to investigate the impact of MYC loss on physio-pathological development of PTEN-proficient or PTEN-deficient T lymphocytes. First, our results confirm that MYC is mandatory for PTEN loss-mediated leukemogenesis, while it is not required for terminal steps of thymopoiesis. In contrast, we uncovered that Myc ablation in CD4+CD8+ thymocytes disrupts T lymphocytes homeostasis in the spleen, notably by drastically reducing the number of MYC-deficient effector/memory T cells. Collectively, our data show that besides naive T cells proliferation, MYC is essential for effector/memory differentiation.
RESUMO
BACKGROUND: GATA1 is an essential transcription factor for both polyploidization and megakaryocyte (MK) differentiation. The polyploidization defect observed in GATA1 variant carriers is not well understood. OBJECTIVE: To extensively phenotype two pedigrees displaying different variants in the GATA1 gene and determine if GATA1 controls MYH10 expression levels, a key modulator of MK polyploidization. METHOD: A total of 146 unrelated propositi with constitutional thrombocytopenia were screened on a multigene panel. We described the genotype-phenotype correlation in GATA1 variant carriers and investigated the effect of these novel variants on MYH10 transcription using luciferase constructs. RESULTS: The clinical profile associated with the p.L268M variant localized in the C terminal zinc finger was unusual in that the patient displayed bleeding and severe platelet aggregation defects without early-onset thrombocytopenia. p.N206I localized in the N terminal zinc finger was associated, on the other hand, with severe thrombocytopenia (15G/L) in early life. High MYH10 levels were evidenced in platelets of GATA1 variant carriers. Analysis of MKs anti-GATA1 chromatin immunoprecipitation-sequencing data revealed two GATA1 binding sites, located in the 3' untranslated region and in intron 8 of the MYH10 gene. Luciferase reporter assays showed their respective role in the regulation of MYH10 gene expression. Both GATA1 variants significantly alter intron 8 driven MYH10 transcription. CONCLUSION: The discovery of an association between MYH10 and GATA1 is a novel one. Overall, this study suggests that impaired MYH10 silencing via an intronic regulatory element is the most likely cause of GATA1-related polyploidization defect.
Assuntos
Fator de Transcrição GATA1 , Megacariócitos , Cadeias Pesadas de Miosina/genética , Miosina não Muscular Tipo IIB/genética , Trombocitopenia , Plaquetas , Fator de Transcrição GATA1/genética , Inativação Gênica , Humanos , Trombocitopenia/genética , Trombopoese/genética , Fatores de TranscriçãoRESUMO
Chimeric antigen receptor T cell (CAR-T) targeting the CD19 antigen represents an innovative therapeutic approach to improve the outcome of relapsed or refractory B-cell acute lymphoblastic leukemia (B-ALL). Yet, despite a high initial remission rate, CAR-T therapy ultimately fails for some patients. Notably, around half of relapsing patients develop CD19 negative (CD19neg) B-ALL allowing leukemic cells to evade CD19-targeted therapy. Herein, we investigate leukemic cells of a relapsing B-ALL patient, at two-time points: before (T1) and after (T2) anti-CD19 CAR-T treatment. We show that at T2, the B-ALL relapse is CD19 negative due to the expression of a non-functional CD19 transcript retaining intron 2. Then, using single-cell RNA sequencing (scRNAseq) approach, we demonstrate that CD19neg leukemic cells were present before CAR-T cell therapy and thus that the relapse results from the selection of these rare CD19neg B-ALL clones. In conclusion, our study shows that scRNAseq profiling can reveal pre-existing CD19neg subclones, raising the possibility to assess the risk of targeted therapy failure.
Assuntos
Antígenos CD19/metabolismo , Imunoterapia Adotiva , Leucemia-Linfoma Linfoblástico de Células Precursoras B/imunologia , Leucemia-Linfoma Linfoblástico de Células Precursoras B/terapia , Análise de Célula Única , Criança , Células Clonais , Humanos , RecidivaRESUMO
Signaling through the αßT cell receptor (TCR) is a crucial determinant of T-cell fate and can induce two opposite outcomes during thymocyte development: cell death or survival and differentiation. To date, the role played by T-cell receptor in the oncogenic transformation of developing T cells remains unclear. Here we show that human primary T-cell acute lymphoblastic leukemias expressing an αßT cell receptor are frequently deficient for phosphatase and tensin homolog protein (PTEN), and fail to respond strongly to T-cell receptor activation. Using Pten-deficient T-cell acute lymphoblastic leukemia mouse models, we confirm that T-cell receptor signaling is involved in leukemogenesis. We show that abrogation of T-cell receptor expression accelerated tumor onset, while enforced expression of a fit transgenic T-cell receptor led to the development of T-cell receptor-negative lymphoma and delayed tumorigenesis. We further demonstrate that pre-tumoral Pten-deficient thymocytes harboring fit T-cell receptors undergo early clonal deletion, thus preventing their malignant transformation, while cells with unfit T-cell receptors that should normally be deleted during positive selection, pass selection and develop T-cell acute lymphoblastic leukemias. Altogether, our data show that fit T-cell receptor signaling suppresses tumor development mediated by Pten loss-of-function and point towards a role of Pten in positive selection.
Assuntos
Transformação Celular Neoplásica/genética , Transformação Celular Neoplásica/metabolismo , Leucemia/genética , Leucemia/metabolismo , PTEN Fosfo-Hidrolase/deficiência , Receptores de Antígenos de Linfócitos T alfa-beta/metabolismo , Timócitos/metabolismo , Animais , Apoptose , Biomarcadores Tumorais , Diferenciação Celular/genética , Modelos Animais de Doenças , Humanos , Leucemia/diagnóstico , Camundongos , Camundongos Transgênicos , PTEN Fosfo-Hidrolase/genética , Receptores de Antígenos de Linfócitos T alfa-beta/genética , Transdução de Sinais , Timócitos/patologiaRESUMO
T-cell acute lymphoblastic leukaemias (T-ALL) are aggressive malignant proliferations characterized by high relapse rates and great genetic heterogeneity. TAL1 is amongst the most frequently deregulated oncogenes. Yet, over half of the TAL1(+) cases lack TAL1 lesions, suggesting unrecognized (epi)genetic deregulation mechanisms. Here we show that TAL1 is normally silenced in the T-cell lineage, and that the polycomb H3K27me3-repressive mark is focally diminished in TAL1(+) T-ALLs. Sequencing reveals that >20% of monoallelic TAL1(+) patients without previously known alterations display microinsertions or RAG1/2-mediated episomal reintegration in a single site 5' to TAL1. Using 'allelic-ChIP' and CrispR assays, we demonstrate that such insertions induce a selective switch from H3K27me3 to H3K27ac at the inserted but not the germline allele. We also show that, despite a considerable mechanistic diversity, the mode of oncogenic TAL1 activation, rather than expression levels, impact on clinical outcome. Altogether, these studies establish site-specific epigenetic desilencing as a mechanism of oncogenic activation.
Assuntos
Alelos , Regulação Leucêmica da Expressão Gênica , Proteínas do Grupo Polycomb/genética , Leucemia-Linfoma Linfoblástico de Células T Precursoras/genética , Acetilação , Adulto , Sequência de Bases , Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Imunoprecipitação da Cromatina , Proteínas de Ligação a DNA/metabolismo , Epigênese Genética , Loci Gênicos , Histonas/metabolismo , Proteínas de Homeodomínio/metabolismo , Humanos , Células Jurkat , Metilação , Dados de Sequência Molecular , Mutagênese Insercional , Proteínas Nucleares/metabolismo , Plasmídeos/genética , Proteínas do Grupo Polycomb/metabolismo , Proteínas Proto-Oncogênicas/metabolismo , Análise de Sobrevida , Proteína 1 de Leucemia Linfocítica Aguda de Células T , Resultado do TratamentoRESUMO
V(D)J recombination of TCR loci is regulated by chromatin accessibility to RAG1/2 proteins, rendering RAG1/2 targeting a potentially important regulator of lymphoid differentiation. We show that within the human TCR-α/δ locus, Dδ2-Dδ3 rearrangements occur at a very immature thymic, CD34(+)/CD1a(-)/CD7(+dim) stage, before Dδ2(Dδ3)-Jδ1 rearrangements. These strictly ordered rearrangements are regulated by mechanisms acting beyond chromatin accessibility. Importantly, direct Dδ2-Jδ1 rearrangements are prohibited by a B12/23 restriction and ordered human TCR-δ gene assembly requires RUNX1 protein, which binds to the Dδ2-23RSS, interacts with RAG1, and enhances RAG1 deposition at this site. This RUNX1-mediated V(D)J recombinase targeting imposes the use of two Dδ gene segments in human TCR-δ chains. Absence of this RUNX1 binding site in the homologous mouse Dδ1-23RSS provides a molecular explanation for the lack of ordered TCR-δ gene assembly in mice and may underlie differences in early lymphoid differentiation between these species.
Assuntos
Subunidade alfa 2 de Fator de Ligação ao Core/metabolismo , Rearranjo Gênico da Cadeia delta dos Receptores de Antígenos dos Linfócitos T , Proteínas de Homeodomínio/metabolismo , Subpopulações de Linfócitos T/imunologia , Subpopulações de Linfócitos T/metabolismo , Animais , Sequência de Bases , Sítios de Ligação/genética , Diferenciação Celular , Linhagem Celular , DNA/genética , DNA/metabolismo , Células HEK293 , Humanos , Cinética , Linfopoese , Camundongos , Dados de Sequência Molecular , Especificidade da Espécie , Subpopulações de Linfócitos T/citologia , VDJ Recombinases/metabolismoRESUMO
T-ALL patients treated with intensive chemotherapy achieve high rates of remission. However, frequent long-term toxicities and relapses into chemotherapy-refractory tumors constitute major clinical challenges which could be met by targeted therapies. c-MYC is a central oncogene in T-ALL, prompting the exploration of the efficacy of MYC inhibitors such as JQ1 (BET-bromodomain inhibitor), and SAHA (HDAC inhibitor). Using a standardized ex vivo drug screening assay, we show here that JQ1 and SAHA show competitive efficiency compared to inhibitors of proteasome, PI3K/AKT/mTOR and NOTCH pathways, and synergize in combination with Vincristine. We also compared for the first time the in vivo relevance of such associations in mice xenografted with human primary T-ALLs. Our data indicate that although treatments combining JQ1 or SAHA with chemotherapeutic regimens might represent promising developments in T-ALL, combinations will need to be tailored to specific subgroups of responsive patients, the profiles of which still remain to be precisely defined.
Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/farmacologia , Leucemia-Linfoma Linfoblástico de Células T Precursoras/metabolismo , Proteínas Proto-Oncogênicas c-myc/antagonistas & inibidores , Animais , Azepinas/administração & dosagem , Ensaios de Seleção de Medicamentos Antitumorais , Sinergismo Farmacológico , Inibidores de Histona Desacetilases/administração & dosagem , Humanos , Camundongos , Nylons , Pirróis/administração & dosagem , Triazóis/administração & dosagem , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
MYC is a potent oncogene involved in â¼70% of human cancers, inducing tumorigenesis with high penetrance and short latency in experimental transgenic models. Accordingly, MYC is recognized as a major driver of T-cell acute lymphoblastic leukemia (T-ALL) in human and zebrafish/mouse models, and uncovering the context by which MYC-mediated malignant transformation initiates and develops remains a considerable challenge. Because MYC is a very complex oncogene, highly dependent on the microenvironment and cell-intrinsic context, we generated transgenic mice (tgMyc(spo)) in which ectopic Myc activation occurs sporadically (<10(-6) thymocytes) within otherwise normal thymic environment, thereby mimicking the unicellular context in which oncogenic alterations initiate human tumors. We show that while Myc(+) clones in tgMyc(spo) mice develop and initially proliferate in thymus and the periphery, no tumor or clonal expansion progress in aging mice (n = 130), suggesting an unexpectedly low ability of Myc to initiate efficient tumorigenesis. Furthermore, to determine the relevance of this observation in human pathogenesis we analyzed a human T-ALL case at diagnosis and relapse using the molecular stigmata of V(D)J recombination as markers of malignant progression; we similarly demonstrate that despite the occurrence of TAL1 and MYC translocations in early thymocyte ontogeny, subsequent oncogenic alterations were required to drive oncogenesis. Altogether, our data suggest that although central to T-ALL, MYC overexpression per se is inefficient in triggering the cascade of events leading to malignant transformation.
Assuntos
Transformação Celular Neoplásica/genética , Transformação Celular Neoplásica/patologia , Genes myc/fisiologia , Peptídeos e Proteínas de Sinalização Intracelular/genética , Leucemia-Linfoma Linfoblástico de Células T Precursoras/genética , Leucemia-Linfoma Linfoblástico de Células T Precursoras/patologia , Animais , Crise Blástica/genética , Crise Blástica/patologia , Células HeLa , Humanos , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Camundongos , Camundongos Transgênicos , Leucemia-Linfoma Linfoblástico de Células T Precursoras/metabolismo , Recidiva , Translocação Genética , Recombinação V(D)JRESUMO
PURPOSE: The Group for Research in Adult Acute Lymphoblastic Leukemia (GRAALL) recently reported a significantly better outcome in T-cell acute lymphoblastic leukemia (T-ALL) harboring NOTCH1 and/or FBXW7 (N/F) mutations compared with unmutated T-ALL. Despite this, one third of patients with N/F-mutated T-ALL experienced relapse. PATIENTS AND METHODS: In a series of 212 adult T-ALLs included in the multicenter randomized GRAALL-2003 and -2005 trials, we searched for additional N/K-RAS mutations and PTEN defects (mutations and gene deletion). RESULTS: N/F mutations were identified in 143 (67%) of 212 patients, and lack of N/F mutation was confirmed to be associated with a poor prognosis. K-RAS, N-RAS, and PTEN mutations/deletions were identified in three (1.6%) of 191, 17 (8.9%) of 191, and 21 (12%) of 175 patients, respectively. The favorable prognostic significance of N/F mutations was restricted to patients without RAS/PTEN abnormalities. These observations led us to propose a new T-ALL oncogenetic classifier defining low-risk patients as those with N/F mutation but no RAS/PTEN mutation (97 of 189 patients; 51%) and all other patients (49%; including 13% with N/F and RAS/PTEN mutations) as high-risk patients. In multivariable analysis, this oncogenetic classifier remained the only significant prognostic covariate (event-free survival: hazard ratio [HR], 3.2; 95% CI, 1.9 to 5.15; P < .001; and overall survival: HR, 3.2; 95% CI, 1.9 to 5.6; P < .001). CONCLUSION: These data demonstrate that the presence of N/F mutations in the absence of RAS or PTEN abnormalities predicts good outcome in almost 50% of adult T-ALL. Conversely, the absence of N/F or presence of RAS/PTEN alterations identifies the remaining cohort of patients with poor prognosis.
Assuntos
Proteínas de Ciclo Celular/genética , Análise Mutacional de DNA , Proteínas F-Box/genética , GTP Fosfo-Hidrolases/genética , Deleção de Genes , Proteínas de Membrana/genética , Mutação , PTEN Fosfo-Hidrolase/genética , Leucemia-Linfoma Linfoblástico de Células T Precursoras/genética , Proteínas Proto-Oncogênicas/genética , Receptor Notch1/genética , Ubiquitina-Proteína Ligases/genética , Proteínas ras/genética , Adulto , Intervalo Livre de Doença , Proteína 7 com Repetições F-Box-WD , Feminino , Predisposição Genética para Doença , Humanos , Estimativa de Kaplan-Meier , Masculino , Análise Multivariada , Fenótipo , Leucemia-Linfoma Linfoblástico de Células T Precursoras/classificação , Leucemia-Linfoma Linfoblástico de Células T Precursoras/mortalidade , Leucemia-Linfoma Linfoblástico de Células T Precursoras/terapia , Valor Preditivo dos Testes , Modelos de Riscos Proporcionais , Proteínas Proto-Oncogênicas p21(ras) , Fatores de Risco , Fatores de Tempo , Adulto JovemRESUMO
Chromosomal translocations involving the TCR loci represent one of the most recurrent oncogenic hallmarks of T-cell acute lymphoblastic leukemia (T-ALL) and are generally believed to result from illegitimate V(D)J recombination events. However, molecular characterization and evaluation of the extent of recombinase involvement at the TCR-oncogene junction has not been fully evaluated. In the present study, screening for TCRß and TCRα/δ translocations by FISH and ligation-mediated PCR in 280 T-ALLs allowed the identification of 4 previously unreported TCR-translocated oncogene partners: GNAG, LEF1, NKX2-4, and IL2RB. Molecular mapping of genomic junctions from TCR translocations showed that the majority of oncogenic partner breakpoints are not recombinase mediated and that the regulatory elements predominantly used to drive oncogene expression differ markedly in TCRß (which are exclusively enhancer driven) and TCRα/δ (which use an enhancer-independent cryptic internal promoter) translocations. Our data also imply that oncogene activation takes place at a very immature stage of thymic development, when Dδ2-Dδ3/Dδ3-Jδ1 and Dß-Jß rearrangements occur, whereas the bulk leukemic maturation arrest occurs at a much later (cortical) stage. These observations have implications for T-ALL therapy, because the preleukemic early thymic clonogenic population needs to be eradicated and its disappearance monitored.
Assuntos
Rearranjo Gênico da Cadeia alfa dos Receptores de Antígenos dos Linfócitos T/genética , Rearranjo Gênico da Cadeia beta dos Receptores de Antígenos dos Linfócitos T/genética , Rearranjo Gênico da Cadeia delta dos Receptores de Antígenos dos Linfócitos T/genética , Oncogenes/fisiologia , Leucemia-Linfoma Linfoblástico de Células T Precursoras/genética , Recombinação Genética/genética , Translocação Genética , Adolescente , Adulto , Sequência de Bases , Criança , Pré-Escolar , Mapeamento Cromossômico , DNA de Neoplasias/genética , Humanos , Hibridização in Situ Fluorescente , Lactente , Pessoa de Meia-Idade , Dados de Sequência Molecular , Reação em Cadeia da Polimerase em Tempo Real , Homologia de Sequência do Ácido Nucleico , Adulto JovemRESUMO
Acute lymphoblastic leukemias (ALLs) are characterized by multistep oncogenic processes leading to cell-differentiation arrest and proliferation. Specific abrogation of maturation blockage constitutes a promising therapeutic option in cancer, which requires precise understanding of the underlying molecular mechanisms. We show that the cortical thymic maturation arrest in T-lineage ALLs that overexpress TLX1 or TLX3 is due to binding of TLX1/TLX3 to ETS1, leading to repression of T cell receptor (TCR) α enhanceosome activity and blocked TCR-Jα rearrangement. TLX1/TLX3 abrogation or enforced TCRαß expression leads to TCRα rearrangement and apoptosis. Importantly, the autoextinction of clones carrying TCRα-driven TLX1 expression supports TLX "addiction" in TLX-positive leukemias and provides further rationale for targeted therapy based on disruption of TLX1/TLX3.
Assuntos
Regulação Neoplásica da Expressão Gênica , Genes Codificadores da Cadeia alfa de Receptores de Linfócitos T , Proteínas de Homeodomínio/fisiologia , Leucemia-Linfoma Linfoblástico de Células T Precursoras/genética , Proteína Proto-Oncogênica c-ets-1/metabolismo , Proteínas Proto-Oncogênicas/fisiologia , Apoptose , Sítios de Ligação , Rearranjo Gênico , Células HeLa , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Humanos , Leucemia-Linfoma Linfoblástico de Células T Precursoras/patologia , Estrutura Terciária de Proteína , Proteína Proto-Oncogênica c-ets-1/fisiologia , Proteínas Proto-Oncogênicas/genética , Proteínas Proto-Oncogênicas/metabolismoRESUMO
Cumulative evidence indicates that MYC, one of the major downstream effectors of NOTCH1, is a critical component of T-cell acute lymphoblastic leukemia (T-ALL) oncogenesis and a potential candidate for targeted therapy. However, MYC is a complex oncogene, involving both fine protein dosage and cell-context dependency, and detailed understanding of MYC-mediated oncogenesis in T-ALL is still lacking. To better understand how MYC is interspersed in the complex T-ALL oncogenic networks, we performed a thorough molecular and biochemical analysis of MYC activation in a comprehensive collection of primary adult and pediatric patient samples. We find that MYC expression is highly variable, and that high MYC expression levels can be generated in a large number of cases in absence of NOTCH1/FBXW7 mutations, suggesting the occurrence of multiple activation pathways in addition to NOTCH1. Furthermore, we show that posttranscriptional deregulation of MYC constitutes a major alternative pathway of MYC activation in T-ALL, operating partly via the PI3K/AKT axis through down-regulation of PTEN, and that NOTCH1(m) might play a dual transcriptional and posttranscriptional role in this process. Altogether, our data lend further support to the significance of therapeutic targeting of MYC and/or the PTEN/AKT pathways, both in GSI-resistant and identified NOTCH1-independent/MYC-mediated T-ALL patients.