RESUMEN
BRIT1, initially identified as an hTERT repressor, has additional functions at DNA damage checkpoints. Here, we demonstrate that BRIT1 formed nuclear foci minutes after irradiation. The foci of BRIT1 colocalized with 53BP1, MDC1, NBS1, ATM, RPA, and ATR. BRIT1 was required for activation of these elements, indicating that BRIT1 is a proximal factor in the DNA damage response pathway. Depletion of BRIT1 increased the accumulation of chromosomal aberrations. In addition, decreased levels of BRIT1 were detected in several types of human cancer, with BRIT1 expression being inversely correlated with genomic instability and metastasis. These results identify BRIT1 as a crucial DNA damage regulator in the ATM/ATR pathways and suggest that it functions as a tumor suppressor gene.
Asunto(s)
Transformación Celular Neoplásica/metabolismo , Aberraciones Cromosómicas , Daño del ADN , Proteínas del Tejido Nervioso/fisiología , Proteínas Supresoras de Tumor/fisiología , Secuencia de Bases , Neoplasias de la Mama/metabolismo , Proteínas de Ciclo Celular , Línea Celular Tumoral , Núcleo Celular/fisiología , Transformación Celular Neoplásica/genética , Transformación Celular Neoplásica/efectos de la radiación , Cromatina/metabolismo , Proteínas del Citoesqueleto , Femenino , Dosificación de Gen , Humanos , Datos de Secuencia Molecular , Mutación , Proteínas del Tejido Nervioso/genética , Proteínas Nucleares/metabolismo , Neoplasias Ováricas/metabolismo , Transactivadores/metabolismo , Proteínas Supresoras de Tumor/genéticaRESUMEN
High-density array comparative genomic hybridization (CGH) showed amplification of chromosome 1q22 centered on the RAB25 small GTPase, which is implicated in apical vesicle trafficking, in approximately half of ovarian and breast cancers. RAB25 mRNA levels were selectively increased in stage III and IV serous epithelial ovarian cancers compared to other genes within the amplified region, implicating RAB25 as a driving event in the development of the amplicon. Increased DNA copy number or RNA level of RAB25 was associated with markedly decreased disease-free survival or overall survival in ovarian and breast cancers, respectively. Forced expression of RAB25 markedly increased anchorage-dependent and anchorage-independent cell proliferation, prevented apoptosis and anoikis, including that induced by chemotherapy, and increased aggressiveness of cancer cells in vivo. The inhibition of apoptosis was associated with a decrease in expression of the proapoptotic molecules, BAK and BAX, and activation of the antiapoptotic phosphatidylinositol 3 kinase (PI3K) and AKT pathway, providing potential mechanisms for the effects of RAB25 on tumor aggressiveness. Overall, these studies implicate RAB25, and thus the RAB family of small G proteins, in aggressiveness of epithelial cancers.
Asunto(s)
Neoplasias de la Mama/genética , Regulación de la Expresión Génica , Neoplasias Ováricas/genética , ARN Mensajero/metabolismo , Proteínas de Unión al GTP rab/metabolismo , Animales , Apoptosis/genética , Proliferación Celular , Cromosomas Humanos Par 1/genética , Femenino , Humanos , Immunoblotting , Proteínas de la Membrana/metabolismo , Ratones , Ratones Endogámicos BALB C , Hibridación de Ácido Nucleico/métodos , Fosfatidilinositol 3-Quinasas/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Proteínas Proto-Oncogénicas/metabolismo , Proteínas Proto-Oncogénicas c-akt , Proteínas Proto-Oncogénicas c-bcl-2/metabolismo , Interferencia de ARN , ARN Mensajero/genética , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Transfección , Células Tumorales Cultivadas , Proteína Destructora del Antagonista Homólogo bcl-2 , Proteína X Asociada a bcl-2 , Proteínas de Unión al GTP rab/genéticaRESUMEN
Transcriptional profiling of patient tumors is a much-heralded advancement in cancer therapy, as it provides the opportunity to identify patients who would benefit from more or less aggressive therapy and thus allows the development of individualized treatment. However, translation of this promise into patient benefit has proven challenging. In this issue of the JCI, Glinsky and colleagues used human and murine models to identify a potential stem cell mRNA signature, based on the hypothesis that tumors with stem cell-like characteristics are likely to have a poor prognosis. Remarkably, an 11-gene "expression signature" associated with "stem cell-ness" separated patients with different cancers into good- and poor-prognosis groups. Such a "magic marker" would, if validated, have a major impact on patient care. However, there remain challenges incumbent with creating and validating such signatures.
Asunto(s)
Biomarcadores de Tumor/genética , Perfilación de la Expresión Génica , Neoplasias/genética , Células Madre Neoplásicas/metabolismo , Análisis de Secuencia por Matrices de Oligonucleótidos , ARN Neoplásico/genética , Animales , Biomarcadores de Tumor/metabolismo , Modelos Animales de Enfermedad , Regulación Neoplásica de la Expresión Génica , Humanos , Ratones , Neoplasias/metabolismo , Neoplasias/terapia , Pronóstico , ARN Neoplásico/metabolismoRESUMEN
Emerging evidence implicates alterations in the RAB small GTPases and their associated regulatory proteins and effectors in multiple human diseases including cancer. We have recently shown that RAB25, located at chromosome 1q22, is amplified at the DNA level and overexpressed at the RNA level in ovarian and breast cancer. These changes correlated with a worsened outcome in both diseases. In addition, enforced expression of RAB25 in both breast and ovarian cancer cells decreased apoptosis and increased proliferation and aggressiveness in vivo, potentially explaining the worsened prognosis. A better understanding of genetic alterations as well as the physiologic and pathophysiologic roles of RAB GTPases may open new opportunities for therapeutic intervention and better outcomes.
Asunto(s)
Neoplasias de la Mama/enzimología , Neoplasias Ováricas/enzimología , Proteínas de Unión al GTP rab/fisiología , Neoplasias de la Mama/patología , Femenino , Humanos , Neoplasias Ováricas/patologíaRESUMEN
The completion of the Human Genome Project and recent advances in functional genomic, proteomic, and high-throughput screening methodologies have provided powerful tools for determining the mechanisms of human diseases, including complex polygenic diseases such as ovarian cancer. These developments may eventually lead to individualized molecular medicine, which is the treatment of patients based on the underlying genetic defects in their tumours and their own genetic makeup. A plethora of novel therapeutic agents that act on specific molecular targets defined by cancer genetics are under development. There is thus a great deal of interest in determining how specific genes and proteins function in cancers, in order to further the understanding of cancer initiation and progression; to aid in identifying biomarkers, therapeutic targets, and determinants of drug responsiveness; and to progress the development of novel antitumour agents.
Asunto(s)
Mutación , Neoplasias Ováricas/genética , Antineoplásicos , Análisis Mutacional de ADN , Diseño de Fármacos , Femenino , Expresión Génica , Humanos , Hibridación Fluorescente in Situ , Hibridación de Ácido Nucleico , Análisis de Secuencia por Matrices de Oligonucleótidos , Neoplasias Ováricas/tratamiento farmacológico , Neoplasias Ováricas/epidemiología , Polimorfismo Conformacional Retorcido-Simple , ProteómicaRESUMEN
We show that atypical PKCiota, which plays a critical role in the establishment and maintenance of epithelial cell polarity, is genomically amplified and overexpressed in serous epithelial ovarian cancers. Furthermore, PKCiota protein is markedly increased or mislocalized in all serous ovarian cancers. An increased PKCiota DNA copy number is associated with decreased progression-free survival in serous epithelial ovarian cancers. In a Drosophila in vivo epithelial tissue model, overexpression of persistently active atypical PKC results in defects in apical-basal polarity, increased Cyclin E protein expression, and increased proliferation. Similar to the Drosophila model, increased PKCiota proteins levels are associated with increased Cyclin E protein expression and proliferation in ovarian cancers. In nonserous ovarian cancers, increased PKCiota protein levels, particularly in the presence of Cyclin E, are associated with markedly decreased overall survival. These results implicate PKCiota as a potential oncogene in ovarian cancer regulating epithelial cell polarity and proliferation and suggest that PKCiota is a novel target for therapy.