RESUMO
UNLABELLED: Targeted molecular therapy has yielded remarkable outcomes in certain cancers, but specific therapeutic targets remain elusive for many others. As a result of two independent RNA interference (RNAi) screens, we identified pathway dependence on a member of the Janus-activated kinase (JAK) tyrosine kinase family, TYK2, and its downstream effector STAT1, in T-cell acute lymphoblastic leukemia (T-ALL). Gene knockdown experiments consistently showed TYK2 dependence in both T-ALL primary specimens and cell lines, and a small-molecule inhibitor of JAK activity induced T-ALL cell death. Activation of this TYK2-STAT1 pathway in T-ALL cell lines occurs by gain-of-function TYK2 mutations or activation of interleukin (IL)-10 receptor signaling, and this pathway mediates T-ALL cell survival through upregulation of the antiapoptotic protein BCL2. These findings indicate that in many T-ALL cases, the leukemic cells are dependent upon the TYK2-STAT1-BCL2 pathway for continued survival, supporting the development of molecular therapies targeting TYK2 and other components of this pathway. SIGNIFICANCE: In recent years, "pathway dependence" has been revealed in specific types of human cancer, which can be important because they pinpoint proteins that are particularly vulnerable to antitumor-targeted inhibition (so-called Achilles' heel proteins). Here, we use RNAi technology to identify a novel oncogenic pathway that involves aberrant activation of the TYK2 tyrosine kinase and its downstream substrate, STAT1, which ultimately promotes T-ALL cell survival through the upregulation of BCL2 expression
Assuntos
Leucemia-Linfoma Linfoblástico de Células T Precursoras/metabolismo , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , Fator de Transcrição STAT1/metabolismo , TYK2 Quinase/metabolismo , Animais , Antineoplásicos/farmacologia , Células da Medula Óssea , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Humanos , Interleucina-10/metabolismo , Janus Quinase 3/antagonistas & inibidores , Leucócitos Mononucleares/efeitos dos fármacos , Leucócitos Mononucleares/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Mutação , Piperidinas/farmacologia , Leucemia-Linfoma Linfoblástico de Células T Precursoras/genética , Inibidores de Proteínas Quinases/farmacologia , Pirimidinas/farmacologia , Pirróis/farmacologia , Interferência de RNA , Fator de Transcrição STAT1/genética , Transdução de Sinais , TYK2 Quinase/antagonistas & inibidores , TYK2 Quinase/genética , Tirfostinas/farmacologiaRESUMO
The oncogenic transcription factor TAL1/SCL is aberrantly expressed in over 40% of cases of human T cell acute lymphoblastic leukemia (T-ALL), emphasizing its importance in the molecular pathogenesis of T-ALL. Here we identify the core transcriptional regulatory circuit controlled by TAL1 and its regulatory partners HEB, E2A, LMO1/2, GATA3, and RUNX1. We show that TAL1 forms a positive interconnected autoregulatory loop with GATA3 and RUNX1 and that the TAL1 complex directly activates the MYB oncogene, forming a positive feed-forward regulatory loop that reinforces and stabilizes the TAL1-regulated oncogenic program. One of the critical downstream targets in this circuitry is the TRIB2 gene, which is oppositely regulated by TAL1 and E2A/HEB and is essential for the survival of T-ALL cells.
Assuntos
Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Redes Reguladoras de Genes/genética , Leucemia-Linfoma Linfoblástico de Células T Precursoras/genética , Proteínas Proto-Oncogênicas/metabolismo , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Linhagem Celular Tumoral , Sobrevivência Celular , Regulação Leucêmica da Expressão Gênica , Genes Neoplásicos/genética , Genoma Humano/genética , Homeostase/genética , Humanos , Proteínas de Neoplasias/genética , Proteínas de Neoplasias/metabolismo , Leucemia-Linfoma Linfoblástico de Células T Precursoras/classificação , Leucemia-Linfoma Linfoblástico de Células T Precursoras/patologia , Ligação Proteica/genética , Proteínas Proto-Oncogênicas/genética , Proteínas Proto-Oncogênicas c-myb/metabolismo , Proteína 1 de Leucemia Linfocítica Aguda de Células T , Linfócitos T/metabolismo , Linfócitos T/patologiaRESUMO
T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive malignancy largely caused by aberrant activation of the TAL1/SCL, LMO1/2, and NOTCH1 oncogenes. Approximately 30% of T-ALL patients relapse, and evidence is emerging that relapse may result from a failure to eliminate leukemia-initiating cells (LICs). Thymic expression of the Tal1 and Lmo2 oncogenes in mice results in rapid development of T-ALL; and similar to T-ALL patients, more than half the leukemic mice develop spontaneous mutations in Notch1. Using this mouse model, we demonstrate that mouse T-ALLs are immunophenotypically and functionally heterogeneous with approximately 1 of 10,000 leukemic cells capable of initiating disease on transplantation. Our preleukemic studies reveal expansion of Notch-active double-negative thymic progenitors, and we find the leukemic DN3 population enriched in disease potential. To examine the role of Notch1 in LIC function, we measured LIC activity in leukemic mice treated with vehicle or with a γ-secretase inhibitor. In 4 of 5 leukemias examined, Notch inhibition significantly reduced or eliminated LICs and extended survival. Remarkably, in 2 mice, γ-secretase inhibitor treatment reduced LIC frequency below the limits of detection of this assay, and all transplanted mice failed to develop disease. These data support the continued development of Notch1 therapeutics as antileukemia agents.
