RESUMO
Pediatric brainstem gliomas often harbor oncogenic K27M mutation of histone H3.3. Here we show that GSKJ4 pharmacologic inhibition of K27 demethylase JMJD3 increases cellular H3K27 methylation in K27M tumor cells and demonstrate potent antitumor activity both in vitro against K27M cells and in vivo against K27M xenografts. Our results demonstrate that increasing H3K27 methylation by inhibiting K27 demethylase is a valid therapeutic strategy for treating K27M-expressing brainstem glioma.
Assuntos
Apoptose/efeitos dos fármacos , Benzazepinas/farmacologia , Neoplasias do Tronco Encefálico/genética , Proliferação de Células/efeitos dos fármacos , Regulação Neoplásica da Expressão Gênica , Glioma/genética , Histonas/efeitos dos fármacos , Histona Desmetilases com o Domínio Jumonji/antagonistas & inibidores , Pirimidinas/farmacologia , Animais , Neoplasias do Tronco Encefálico/metabolismo , Linhagem Celular Tumoral , Criança , Glioma/metabolismo , Histonas/genética , Histonas/metabolismo , Humanos , Histona Desmetilases com o Domínio Jumonji/metabolismo , Metilação/efeitos dos fármacos , Camundongos , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
PURPOSE: Malignant astrocytomas (MA) are aggressive central nervous system tumors with poor prognosis. Activating mutation of BRAF (BRAF(V600E)) has been reported in a subset of these tumors, especially in children. We have investigated the incidence of BRAF(V600E) in additional pediatric patient cohorts and examined the effects of BRAF blockade in preclinical models of BRAF(V600E) and wild-type BRAF MA. EXPERIMENTAL DESIGN: BRAF(V600E) mutation status was examined in two pediatric MA patient cohorts. For functional studies, BRAF(V600E) MA cell lines were used to investigate the effects of BRAF shRNA knockdown in vitro, and to investigate BRAF pharmacologic inhibition in vitro and in vivo. RESULTS: BRAF(V600E) mutations were identified in 11 and 10% of MAs from two distinct series of tumors (six of 58 cases total). BRAF was expressed in all MA cell lines examined, among which BRAF(V600E) was identified in four instances. Using the BRAF(V600E)-specific inhibitor PLX4720, pharmacologic blockade of BRAF revealed preferential antiproliferative activity against BRAF(V600E) mutant cells in vitro, in contrast to the use of shRNA-mediated knockdown of BRAF, which inhibited cell growth of glioma cell lines regardless of BRAF mutation status. Using orthotopic MA xenografts, we show that PLX4720 treatment decreases tumor growth and increases overall survival in mice-bearing BRAF(V600E) mutant xenografts, while being ineffective, and possibly tumor promoting, against xenografts with wild-type BRAF. CONCLUSIONS: Our results indicate a 10% incidence of activating BRAF(V600E) among pediatric MAs. With regard to implications for therapy, our results support evaluation of BRAF(V600E)-specific inhibitors for treating BRAF(V600E) MA patients.
Assuntos
Astrocitoma/genética , Neoplasias Encefálicas/genética , Mutação , Proteínas Proto-Oncogênicas B-raf/genética , Adolescente , Substituição de Aminoácidos , Animais , Astrocitoma/metabolismo , Astrocitoma/patologia , Astrocitoma/prevenção & controle , Sequência de Bases , Western Blotting , Neoplasias Encefálicas/metabolismo , Neoplasias Encefálicas/patologia , Neoplasias Encefálicas/prevenção & controle , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Criança , Pré-Escolar , Análise Mutacional de DNA , Feminino , Humanos , Indóis/farmacologia , Lactente , Estimativa de Kaplan-Meier , Camundongos , Camundongos Nus , Proteínas Proto-Oncogênicas B-raf/antagonistas & inibidores , Proteínas Proto-Oncogênicas B-raf/metabolismo , Interferência de RNA , Sulfonamidas/farmacologia , Carga Tumoral/efeitos dos fármacos , Ensaios Antitumorais Modelo de Xenoenxerto , Adulto JovemRESUMO
The phosphoinositide 3-kinase (PI3K) signaling pathway is one of the most altered in cancer, leading to a range of cellular responses including enhanced proliferation, survival, and metabolism, and is thus an attractive target for anticancer drug development. Stimulation of the PI3K pathway can be initiated by alterations at different levels of the signaling cascade including growth factor receptor activation, as well as mutations in PIK3CA, PTEN, and AKT genes frequently found in a broad range of cancers. Given its role in glucose metabolism, we investigated the utility of [(18)F]fluorodeoxyglucose positron emission tomography ([(18)F]FDG PET) as a pharmacodynamic biomarker of PI3K pathway-induced glucose metabolism. PTEN deletion in human colon carcinoma cells led to constitutive AKT activation but did not confer a phenotype of increased cell proliferation or glucose metabolism advantage in vivo relative to isogenic tumors derived from cells with a wild-type allele. This was not due to the activation context, that is, phosphatase activity, per se because PIK3CA activation in xenografts derived from the same lineage failed to increase glucose metabolism. Acute inhibition of PI3K activity by LY294002, and hence decreased activated AKT expression, led to a significant reduction in tumor [(18)F]FDG uptake that could be explained at least in part by decreased membrane glucose transporter 1 expression. The pharmacodynamic effect was again independent of PTEN status. In conclusion, [(18)F]FDG PET is a promising pharmacodynamic biomarker of PI3K pathway inhibition; however, its utility to detect glucose metabolism is not directly linked to the magnitude of activated AKT protein expression.
