RESUMEN
Triple-negative breast cancer (TNBC) is a heterogeneous and clinically aggressive disease for which there is no targeted therapy. BET bromodomain inhibitors, which have shown efficacy in several models of cancer, have not been evaluated in TNBC. These inhibitors displace BET bromodomain proteins such as BRD4 from chromatin by competing with their acetyl-lysine recognition modules, leading to inhibition of oncogenic transcriptional programs. Here we report the preferential sensitivity of TNBCs to BET bromodomain inhibition in vitro and in vivo, establishing a rationale for clinical investigation and further motivation to understand mechanisms of resistance. In paired cell lines selected for acquired resistance to BET inhibition from previously sensitive TNBCs, we failed to identify gatekeeper mutations, new driver events or drug pump activation. BET-resistant TNBC cells remain dependent on wild-type BRD4, which supports transcription and cell proliferation in a bromodomain-independent manner. Proteomic studies of resistant TNBC identify strong association with MED1 and hyper-phosphorylation of BRD4 attributable to decreased activity of PP2A, identified here as a principal BRD4 serine phosphatase. Together, these studies provide a rationale for BET inhibition in TNBC and present mechanism-based combination strategies to anticipate clinical drug resistance.
Asunto(s)
Azepinas/farmacología , Azepinas/uso terapéutico , Resistencia a Antineoplásicos/efectos de los fármacos , Proteínas Nucleares/antagonistas & inhibidores , Estructura Terciaria de Proteína/efectos de los fármacos , Factores de Transcripción/antagonistas & inhibidores , Triazoles/farmacología , Triazoles/uso terapéutico , Neoplasias de la Mama Triple Negativas/tratamiento farmacológico , Animales , Unión Competitiva/efectos de los fármacos , Quinasa de la Caseína II/metabolismo , Proteínas de Ciclo Celular , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Proliferación Celular/genética , Cromatina/genética , Cromatina/metabolismo , Resistencia a Antineoplásicos/genética , Epigénesis Genética/efectos de los fármacos , Epigénesis Genética/genética , Femenino , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos , Genoma Humano/efectos de los fármacos , Genoma Humano/genética , Humanos , Subunidad 1 del Complejo Mediador/metabolismo , Ratones , Proteínas Nucleares/deficiencia , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Fosforilación/efectos de los fármacos , Fosfoserina/metabolismo , Unión Proteica/efectos de los fármacos , Proteína Fosfatasa 2/metabolismo , Proteómica , Factores de Transcripción/deficiencia , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Transcripción Genética/efectos de los fármacos , Neoplasias de la Mama Triple Negativas/genética , Neoplasias de la Mama Triple Negativas/metabolismo , Neoplasias de la Mama Triple Negativas/patología , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
Molecular and cellular mechanisms underlying the peripheral conditioning lesion remain unsolved. We show here that injection of a chemical demyelinating agent, ethidium bromide, into the sciatic nerve induces a similar set of regeneration-associated genes and promotes a 2.7-fold greater extent of sensory axon regeneration in the spinal cord than sciatic nerve crush. We found that more severe peripheral demyelination correlates with more severe functional and electrophysiological deficits, but more robust central regeneration. Ethidium bromide injection does not activate macrophages at the demyelinated sciatic nerve site, as observed after nerve crush, but briefly activates macrophages in the dorsal root ganglion. This study provides a new method for investigating the underlying mechanisms of the conditioning response and suggests that loss of the peripheral myelin may be a major signal to change the intrinsic growth state of adult sensory neurons and promote regeneration.