RESUMO
Nearly 60% of acute myeloid leukemia (AML) patients with the t(8;21)(q22;q22) translocation fail to achieve long-term disease-free survival. Our previous studies demonstrated that oridonin selectively induces apoptosis of t(8;21) leukemia cells and causes cleavage of AML1-ETO oncoprotein resulting from t(8;21), but the underlying mechanisms remain unclear. We show that oridonin interacted with glutathione and thioredoxin/thioredoxin reductase to increase intracellular reactive oxygen species, which in turn activated caspase-3 in t(8;21) cells. Moreover, oridonin bound AML1-ETO, directing the enzymatic cleavage at aspartic acid 188 via caspase-3 to generate a truncated AML1-ETO (ΔAML1-ETO) and preventing the protein from further proteolysis. ΔAML1-ETO interacted with AML1-ETO and interfered with the trans-regulatory functions of remaining AML1-ETO oncoprotein, thus acting as a tumor suppressor that mediates the anti-leukemia effect of oridonin. Furthermore, oridonin inhibited the activity of c-Kit(+) leukemia-initiating cells. Therefore, oridonin is a potential lead compound for molecular target-based therapy of leukemia.
Assuntos
Cromossomos Humanos Par 21/genética , Cromossomos Humanos Par 8/genética , Subunidade alfa 2 de Fator de Ligação ao Core/antagonistas & inibidores , Diterpenos do Tipo Caurano/farmacologia , Leucemia Mieloide Aguda/genética , Proteínas de Fusão Oncogênica/antagonistas & inibidores , Translocação Genética/efeitos dos fármacos , Proteínas Supressoras de Tumor/metabolismo , Animais , Caspase 3/metabolismo , Subunidade alfa 2 de Fator de Ligação ao Core/genética , Ativação Enzimática/efeitos dos fármacos , Humanos , Espaço Intracelular/efeitos dos fármacos , Espaço Intracelular/metabolismo , Leucemia Mieloide Aguda/enzimologia , Camundongos , Camundongos Endogâmicos C57BL , Modelos Biológicos , Terapia de Alvo Molecular , Células-Tronco Neoplásicas/efeitos dos fármacos , Células-Tronco Neoplásicas/patologia , Proteínas de Fusão Oncogênica/genética , Estabilidade Proteica/efeitos dos fármacos , Proteína 1 Parceira de Translocação de RUNX1 , Espécies Reativas de Oxigênio/metabolismoRESUMO
This study was purposed to characterize the genomic distribution of the binding sites for AML1-ETO fusion protein on chromosome 2, 9 and 19, and to further gain insights into the characteristics of transcriptional regulation by AML1-ETO in acute myeloid leukemia so as to provide theoretical basis for the development of targeted therapy and optimization for treatment. Chromatin immunoprecipitation (ChIP) coupled with high density tiling arrays (chip), also known as ChIP-chip, was utilized in this study. ChIP-DNA enriched by an anti-ETO antibody and total genomic DNA of Kasumi cells were hybridized to tiling arrays, tiled through chromosome 2, 9 and 19. The ChIP enriched regions were identified using a model based analytical tool (MAT). Genomic distribution of the ChIP regions was analyzed using publicly available CEAS web server. The Gene Ontology (GO) enrichment analysis was performed to excavated the biological significance. The results indicated that a total of 588 enriched regions were identified on chromosome 2, 9 and 19 by the anti-ETO antibody. A number of the identified regions were located within enhancers (48.86%) or introns (37.35%), much smaller fractions were within proximal promoters (5.96%) or exons (5.49%). Functional enrichment analysis showed that cell proliferation and signal transduction biological pathways were enriched in potential genes of AML-ETO. It is concluded that half of the AML1-ETO binding sites are located within known transcriptional regulatory regions (promoter, 5' UTR and enhancer), while almost another half were within the sequences which were not previously reported as regulatory regions. The potential target molecular network of AML1-ETO is involved in several essential biological processes.