RESUMEN
Super-enhancers (SEs), which are composed of large clusters of enhancers densely loaded with the Mediator complex, transcription factors and chromatin regulators, drive high expression of genes implicated in cell identity and disease, such as lineage-controlling transcription factors and oncogenes. BRD4 and CDK7 are positive regulators of SE-mediated transcription. By contrast, negative regulators of SE-associated genes have not been well described. Here we show that the Mediator-associated kinases cyclin-dependent kinase 8 (CDK8) and CDK19 restrain increased activation of key SE-associated genes in acute myeloid leukaemia (AML) cells. We report that the natural product cortistatin A (CA) selectively inhibits Mediator kinases, has anti-leukaemic activity in vitro and in vivo, and disproportionately induces upregulation of SE-associated genes in CA-sensitive AML cell lines but not in CA-insensitive cell lines. In AML cells, CA upregulated SE-associated genes with tumour suppressor and lineage-controlling functions, including the transcription factors CEBPA, IRF8, IRF1 and ETV6 (refs 6-8). The BRD4 inhibitor I-BET151 downregulated these SE-associated genes, yet also has anti-leukaemic activity. Individually increasing or decreasing the expression of these transcription factors suppressed AML cell growth, providing evidence that leukaemia cells are sensitive to the dosage of SE-associated genes. Our results demonstrate that Mediator kinases can negatively regulate SE-associated gene expression in specific cell types, and can be pharmacologically targeted as a therapeutic approach to AML.
Asunto(s)
Quinasa 8 Dependiente de Ciclina/antagonistas & inhibidores , Quinasas Ciclina-Dependientes/antagonistas & inhibidores , Elementos de Facilitación Genéticos/genética , Regulación Neoplásica de la Expresión Génica/genética , Genes Relacionados con las Neoplasias/genética , Leucemia Mieloide Aguda/enzimología , Leucemia Mieloide Aguda/genética , Animales , Proteínas de Ciclo Celular , División Celular/efectos de los fármacos , Línea Celular Tumoral , Linaje de la Célula/efectos de los fármacos , Linaje de la Célula/genética , Quinasa 8 Dependiente de Ciclina/metabolismo , Quinasas Ciclina-Dependientes/metabolismo , Progresión de la Enfermedad , Regulación hacia Abajo/efectos de los fármacos , Regulación hacia Abajo/genética , Femenino , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos , Genes Supresores de Tumor/efectos de los fármacos , Compuestos Heterocíclicos de 4 o más Anillos/farmacología , Humanos , Leucemia Mieloide Aguda/tratamiento farmacológico , Leucemia Mieloide Aguda/patología , Masculino , Ratones , Ratones Endogámicos , Ratones SCID , Proteínas Nucleares/antagonistas & inhibidores , Compuestos Policíclicos/farmacología , Factores de Transcripción/antagonistas & inhibidores , Factores de Transcripción/biosíntesis , Factores de Transcripción/genética , Regulación hacia Arriba/efectos de los fármacos , Regulación hacia Arriba/genéticaRESUMEN
A series of novel 2-phenylindole analogs were synthesized and evaluated for activity in subgenomic HCV replicon inhibition assays. Several compounds containing small alkyl sulfonamides on the phenyl ring exhibiting submicromolar EC50 values against the genotype 1b replicon were identified. Among these, compound 25d potently inhibited the 1b replicon (EC50=0.17 µM) with 147-fold selectivity with respect to cytotoxicity. Compound 25d was stable in the presence of human liver microsomes and had a good pharmacokinetic profile in rats with an IV half-life of 4.3h and oral bioavailability (F) of 58%.
Asunto(s)
Antivirales/farmacología , Descubrimiento de Drogas , Hepacivirus/efectos de los fármacos , Indoles/farmacología , Microsomas Hepáticos/efectos de los fármacos , Sulfonamidas/farmacología , Replicación Viral/efectos de los fármacos , Animales , Antivirales/administración & dosificación , Antivirales/química , Disponibilidad Biológica , Relación Dosis-Respuesta a Droga , Humanos , Indoles/síntesis química , Indoles/química , Pruebas de Sensibilidad Microbiana , Estructura Molecular , Ratas , Relación Estructura-Actividad , Sulfonamidas/síntesis química , Sulfonamidas/químicaRESUMEN
The natural product austocystin D was identified as a potent cytotoxic agent with in vivo antitumor activity and selectivity for cells expressing the multidrug resistance transporter MDR1. We sought to elucidate the mechanism of austocystin D's selective cytotoxic activity. Here we show that the selective cytotoxic action of austocystin D arises from its selective activation by cytochrome P450 (CYP) enzymes in specific cancer cell lines, leading to induction of DNA damage in cells and in vitro. The potency and selectivity of austocystin D is lost upon inhibition of CYP activation and does not require MDR1 expression or activity. Furthermore, the pattern of cytotoxicity of austocystin D was distinct from doxorubicin and etoposide and unlike aflatoxin B(1), a compound that resembles austocystin D and is also activated by CYP enzymes to induce DNA damage. Theses results suggest that austocystin D may be of clinical benefit for targeting or overcoming chemoresistance.
Asunto(s)
Aflatoxina B1/farmacología , Aflatoxinas/aislamiento & purificación , Aflatoxinas/farmacología , Antineoplásicos/aislamiento & purificación , Antineoplásicos/farmacología , Aspergillus/química , Sistema Enzimático del Citocromo P-450/efectos de los fármacos , Resistencia a Múltiples Medicamentos/efectos de los fármacos , Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/genética , Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/metabolismo , Transportadoras de Casetes de Unión a ATP/efectos de los fármacos , Aflatoxinas/química , Antineoplásicos/química , Sistema Enzimático del Citocromo P-450/metabolismo , Daño del ADN/efectos de los fármacos , Daño del ADN/fisiología , Ensayos de Selección de Medicamentos Antitumorales , Humanos , Estructura MolecularRESUMEN
An efficient, highly convergent stereocontrolled synthesis of (+)-discodermolide has been achieved with 2.1% overall yield (27 steps longest linear sequence). The absolute stereochemistry of the C1-C6 (12), C7-C14 (13), and C15-C24 (11) subunits was introduced using asymmetric crotylation methodology. Key elements of the synthesis include the use of hydrozirconation-cross-coupling methodology for the construction of C13-C14 (Z)-olefin, acetate aldol reaction to construct the C6-C7 bond and install the C7 stereocenter with high levels of 1,5-anti stereoinduction, and the use of palladium-mediated sp(2)-sp(3) cross-coupling reaction to join the advanced fragments, which assembled the carbon framework of discodermolide.
Asunto(s)
Alcanos/síntesis química , Carbamatos/síntesis química , Lactonas/síntesis química , Silanos/química , Animales , Antineoplásicos/síntesis química , Poríferos/química , Pironas , EstereoisomerismoRESUMEN
[structure: see text] A convergent and stereoselective assembly of the C1-C14 subunit of marine natural product (+)-discodermolide has been completed. The approach employs chiral allylsilane bond construction methodology to establish four of the eight stereogenic centers. Key fragment coupling is achieved via an efficient stereoselective acetate aldol reaction between C1-C6 and C7-C14 subunits.