RESUMO
ZBTB transcription factors orchestrate gene transcription during tissue development. However, their roles in glioblastoma (GBM) remain unexplored. Here, through a functional screening of ZBTB genes, we identify that BCL6 is required for GBM cell viability and that BCL6 overexpression is associated with worse prognosis. In a somatic transgenic mouse model, depletion of Bcl6 inhibits the progression of KrasG12V-driven high-grade glioma. Transcriptome analysis demonstrates the involvement of BCL6 in tumor protein p53 (TP53), erythroblastic leukemia viral oncogene homolog (ErbB), and MAPK signaling pathways. Indeed, BCL6 represses the expression of wild-type p53 and its target genes in GBM cells. Knockdown of BCL6 augments the activation of TP53 pathway in response to radiation. Importantly, we discover that receptor tyrosine kinase AXL is a transcriptional target of BCL6 in GBM and mediates partially the regulatory effects of BCL6 on both MEK-ERK (mitogen-activated protein/extracellular signal-regulated kinase kinase-extracellular signal-regulated kinase) and S6K-RPS6 (ribosomal protein S6 kinase-ribosomal protein S6) axes. Similar to BCL6 silencing, depletion of AXL profoundly attenuates GBM proliferation both in vitro and in vivo. Moreover, targeted inhibition of BCL6/nuclear receptor corepressor 1 (NCoR) complex by peptidomimetic inhibitor not only significantly decreases AXL expression and the activity of MEK-ERK and S6K-RPS6 cascades but also displays a potent antiproliferative effect against GBM cells. Together, these findings uncover a glioma-promoting role of BCL6 and provide the rationale of targeting BCL6 as a potential therapeutic approach.
Assuntos
Glioblastoma/tratamento farmacológico , Glioblastoma/patologia , Proteínas Proto-Oncogênicas c-bcl-6/metabolismo , Animais , Neoplasias Encefálicas/genética , Neoplasias Encefálicas/metabolismo , Neoplasias Encefálicas/patologia , Linhagem Celular Tumoral , Gefitinibe , Regulação Neoplásica da Expressão Gênica , Glioblastoma/genética , Glioblastoma/metabolismo , Glioma/genética , Glioma/metabolismo , Glioma/patologia , Humanos , MAP Quinase Quinase Quinases/metabolismo , Camundongos Mutantes , Terapia de Alvo Molecular , Proteínas Proto-Oncogênicas/metabolismo , Proteínas Proto-Oncogênicas c-bcl-6/antagonistas & inibidores , Proteínas Proto-Oncogênicas c-bcl-6/genética , Quinazolinas/farmacologia , Receptores Proteína Tirosina Quinases/metabolismo , Transdução de Sinais , Proteína Supressora de Tumor p53/metabolismo , Ensaios Antitumorais Modelo de Xenoenxerto , Receptor Tirosina Quinase AxlRESUMO
Trophic factor delivery to the brain using stem cell-derived neural progenitors is a powerful way to bypass the blood-brain barrier. Protection of diseased neurons using this technology is a promising therapy for neurodegenerative diseases. Glial cell line-derived neurotrophic factor (GDNF) has provided benefits to Parkinsonian patients and is being used in a clinical trial for amyotrophic lateral sclerosis. However, chronic trophic factor delivery prohibits dose adjustment or cessation if side effects develop. To address this, we engineered a doxycycline-regulated vector, allowing inducible and reversible expression of a therapeutic molecule. Human induced pluripotent stem cell (iPSC)-derived neural progenitors were stably transfected with the vector and transplanted into the adult mouse brain. Doxycycline can penetrate the graft, with addition and withdrawal providing inducible and reversible GDNF expression in vivo, over multiple cycles. Our findings provide proof of concept for combining gene and stem cell therapy for effective modulation of ectopic protein expression in transplanted cells.