RESUMEN
Only a minority of breast cancer patients responds to chemotherapy and we lack predictive biomarkers that help to select a patient-tailored therapy that takes into consideration the molecular heterogeneity of the cancer type. Responsiveness to the clinically important nucleoside analogs gemcitabine and decitabine may be critically determined by Deoxycytidine kinase (DCK) expression as this enzyme is required to convert the inactive prodrugs into their pharmacologically active forms. Here, we examined whether DCK is differentially expressed in breast cancer and evaluated whether DCK expression levels control responsiveness to these nucleoside analogs in vitro by experimentally modulating DCK expression levels. We examined DCK expression in gene expression data sets of breast tumors including the series of 295 consecutive patients that have been classified into low or high risk for recurrence using the MammaPrint 70 gene profile. We found that DCK is expressed at higher levels in patients having poor clinical outcome as judged by the MammaPrint assay. As such, patients that have a poor prognosis may thus be susceptible to treatment with nucleoside analogs. In support of this, we found a causal relationship between DCK levels and sensitivity to these nucleoside analogs in breast cancer cell lines. The data indicate that breast cancers that are at high risk of recurrence express higher levels of DCK, which we find to be strongly correlated to a favorable response to nucleoside analogs. The data suggest that DCK expression in breast cancer could be exploited to select patients that are likely to respond to treatment with nucleoside analogs.
Asunto(s)
Antimetabolitos Antineoplásicos/uso terapéutico , Neoplasias de la Mama/tratamiento farmacológico , Neoplasias de la Mama/genética , Desoxicitidina Quinasa/genética , Desoxirribonucleósidos/uso terapéutico , Animales , Antimetabolitos Antineoplásicos/farmacología , Mama/metabolismo , Neoplasias de la Mama/enzimología , Línea Celular Tumoral , Desoxirribonucleósidos/farmacología , Resistencia a Antineoplásicos/genética , Células Epiteliales/efectos de los fármacos , Células Epiteliales/metabolismo , Femenino , Expresión Génica , Silenciador del Gen , Humanos , Neoplasias Pulmonares/genética , Neoplasias Pulmonares/metabolismo , Ratones , Pronóstico , Transducción Genética , Resultado del TratamientoRESUMEN
Senescence is a robust cell cycle arrest controlled by the p53 and Rb pathways that acts as an important barrier to tumorigenesis. Senescence is associated with profound alterations in gene expression, including stable suppression of E2f-target genes by heterochromatin formation. Some of these changes in chromatin composition are orchestrated by Rb. In complex with E2f, Rb recruits chromatin modifying enzymes to E2f target genes, leading to their transcriptional repression. To identify novel chromatin remodeling enzymes that specifically function in the Rb pathway, we used a functional genetic screening model for bypass of senescence in murine cells. We identified the H3K4-demethylase Jarid1b as novel component of the Rb pathway in this screening model. We find that depletion of Jarid1b phenocopies knockdown of Rb1 and that Jarid1b associates with E2f-target genes during cellular senescence. These results suggest a role for Jarid1b in Rb-mediated repression of cell cycle genes during senescence.
Asunto(s)
Senescencia Celular/fisiología , Factores de Transcripción E2F/metabolismo , Fibroblastos/metabolismo , Proteína de Retinoblastoma/metabolismo , Western Blotting , Proliferación Celular , Células Cultivadas , Senescencia Celular/genética , Inmunoprecipitación de Cromatina , Proteínas de Unión al ADN , Factores de Transcripción E2F/genética , Fibroblastos/citología , Inmunoprecipitación , Histona Demetilasas con Dominio de Jumonji , Unión Proteica , Proteína de Retinoblastoma/genética , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Transducción de Señal/genética , Transducción de Señal/fisiologíaRESUMEN
RNA silencing or interference (RNAi) is a gene regulation mechanism in eukaryotes that controls cell differentiation and developmental processes via expression of microRNAs. RNAi also serves as an innate antiviral defence response in plants, nematodes, and insects. This antiviral response is triggered by virus-specific double-stranded RNA molecules (dsRNAs) that are produced during infection. To overcome antiviral RNAi responses, many plant and insect viruses encode RNA silencing suppressors (RSSs) that enable them to replicate at higher titers. Recently, several human viruses were shown to encode RSSs, suggesting that RNAi also serves as an innate defence response in mammals. Here, we demonstrate that the Ebola virus VP35 protein is a suppressor of RNAi in mammalian cells and that its RSS activity is functionally equivalent to that of the HIV-1 Tat protein. We show that VP35 can replace HIV-1 Tat and thereby support the replication of a Tat-minus HIV-1 variant. The VP35 dsRNA-binding domain is required for this RSS activity. Vaccinia virus E3L protein and influenza A virus NS1 protein are also capable of replacing the HIV-1 Tat RSS function. These findings support the hypothesis that RNAi is part of the innate antiviral response in mammalian cells. Moreover, the results indicate that RSSs play a critical role in mammalian virus replication.