RESUMO
In diffuse large B-cell lymphoma (DLBCL), activation of the B-cell receptor (BCR) promotes multiple oncogenic signals, which are essential for tumor proliferation. Inhibition of the Bruton's tyrosine kinase (BTK), a BCR downstream target, is therapeutically effective only in a subgroup of patients with DLBCL. Here, we used lymphoma cells isolated from patients with DLBCL to measure the effects of targeted therapies on BCR signaling and to anticipate response. In lymphomas resistant to BTK inhibition, we show that blocking BTK activity enhanced tumor dependencies from alternative oncogenic signals downstream of the BCR, converging on MYC upregulation. To completely ablate the activity of the BCR, we genetically and pharmacologically repressed the activity of the SRC kinases LYN, FYN, and BLK, which are responsible for the propagation of the BCR signal. Inhibition of these kinases strongly reduced tumor growth in xenografts and cell lines derived from patients with DLBCL independent of their molecular subtype, advancing the possibility to be relevant therapeutic targets in broad and diverse groups of DLBCL patients.
Assuntos
Linfoma não Hodgkin/etiologia , Linfoma não Hodgkin/metabolismo , Inibidores de Proteínas Quinases/farmacologia , Receptores de Antígenos de Linfócitos B/metabolismo , Transdução de Sinais/efeitos dos fármacos , Quinases da Família src/antagonistas & inibidores , Adenina/análogos & derivados , Animais , Linhagem Celular Tumoral , Transformação Celular Neoplásica/metabolismo , Modelos Animais de Doenças , Resistencia a Medicamentos Antineoplásicos/genética , Expressão Gênica , Genes myc , Humanos , Linfoma não Hodgkin/tratamento farmacológico , Linfoma não Hodgkin/patologia , Camundongos , Camundongos Knockout , Piperidinas , Pirazóis/farmacologia , Pirimidinas/farmacologia , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
Mucosa-associated lymphoid tissue 1 (MALT1) controls antigen receptor-mediated signalling to nuclear factor κB (NF-κB) through both its adaptor and protease function. Upon antigen stimulation, MALT1 forms a complex with BCL10 and CARMA1, which is essential for initial IκBα phosphorylation and NF-κB nuclear translocation. Parallel induction of MALT1 protease activity serves to inactivate negative regulators of NF-κB signalling, such as A20 and RELB. Here we demonstrate a key role for auto-proteolytic MALT1 cleavage in B- and T-cell receptor signalling. MALT1 cleavage occurred after Arginine 149, between the N-terminal death domain and the first immunoglobulin-like region, and did not affect its proteolytic activity. Jurkat T cells expressing an un-cleavable MALT1-R149A mutant showed unaltered initial IκBα phosphorylation and normal nuclear accumulation of NF-κB subunits. Nevertheless, MALT1 cleavage was required for optimal activation of NF-κB reporter genes and expression of the NF-κB targets IL-2 and CSF2. Transcriptome analysis confirmed that MALT1 cleavage after R149 was required to induce NF-κB transcriptional activity in Jurkat T cells. Collectively, these data demonstrate that auto-proteolytic MALT1 cleavage controls antigen receptor-induced expression of NF-κB target genes downstream of nuclear NF-κB accumulation.
Assuntos
Caspases/fisiologia , Linfócitos/metabolismo , NF-kappa B/metabolismo , Proteínas de Neoplasias/fisiologia , Transdução de Sinais/fisiologia , Transcrição Gênica/genética , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Proteína 10 de Linfoma CCL de Células B , Sequência de Bases , Western Blotting , Caspases/genética , Caspases/metabolismo , Membrana Celular/metabolismo , Transferência Ressonante de Energia de Fluorescência , Perfilação da Expressão Gênica , Células HEK293 , Humanos , Células Jurkat , Dados de Sequência Molecular , Proteína de Translocação 1 do Linfoma de Tecido Linfoide Associado à Mucosa , Mutação de Sentido Incorreto/genética , Proteínas de Neoplasias/genética , Proteínas de Neoplasias/metabolismo , Proteólise , Reação em Cadeia da Polimerase em Tempo Real , Receptores de Antígenos/metabolismo , Análise de Sequência de RNA , Transdução de Sinais/genética , Transcrição Gênica/fisiologiaRESUMO
A chronic inflammatory microenvironment favors tumor progression through molecular mechanisms that are still incompletely defined. In inflammation-induced skin cancers, IL-1 receptor- or caspase-1-deficient mice, or mice specifically deficient for the inflammasome adaptor protein ASC (apoptosis-associated speck-like protein containing a CARD) in myeloid cells, had reduced tumor incidence, pointing to a role for IL-1 signaling and inflammasome activation in tumor development. However, mice fully deficient for ASC were not protected, and mice specifically deficient for ASC in keratinocytes developed more tumors than controls, suggesting that, in contrast to its proinflammatory role in myeloid cells, ASC acts as a tumor-suppressor in keratinocytes. Accordingly, ASC protein expression was lost in human cutaneous squamous cell carcinoma, but not in psoriatic skin lesions. Stimulation of primary mouse keratinocytes or the human keratinocyte cell line HaCaT with UVB induced an ASC-dependent phosphorylation of p53 and expression of p53 target genes. In HaCaT cells, ASC interacted with p53 at the endogenous level upon UVB irradiation. Thus, ASC in different tissues may influence tumor growth in opposite directions: it has a proinflammatory role in infiltrating cells that favors tumor development, but it also limits keratinocyte proliferation in response to noxious stimuli, possibly through p53 activation, which helps suppressing tumors.