RESUMEN
Centrosome amplification and chromosome abnormality are frequently identified in neoplasia and tumorigenesis. However, the mechanisms underlying these defects remain unclear. We here identify that MCT-1 is a centrosomal oncoprotein involved in mitosis. Knockdown of MCT-1 protein results in intercellular bridging, chromosome mis-congregation, cytokinesis delay, and mitotic death. Introduction of MCT-1 oncogene into the p53 deficient cells (MCT-1-p53), the mitotic checkpoint kinases and proteins are deregulated synergistically. These biochemical alterations are accompanied with increased frequencies of cytokinesis failure, multi-nucleation, and centrosome amplification in subsequent cell cycle. As a result, the incidences of polyploidy and aneuploidy are progressively induced by prolonged cell cultivation or further promoted by sustained spindle damage on MCT-1-p53 background. These data show that the oncoprotein perturbs centrosome structure and mitotic progression, which provide the molecular aspect of chromsomal abnormality in vitro and the information for understanding the stepwise progression of tumors under oncogenic stress.
Asunto(s)
Proteínas de Ciclo Celular/metabolismo , Núcleo Celular/metabolismo , Mitosis , Proteínas Oncogénicas/metabolismo , Aneuploidia , Proteínas de Ciclo Celular/antagonistas & inhibidores , Proteínas de Ciclo Celular/genética , Línea Celular , Centrosoma/metabolismo , Citocinesis , Humanos , Proteínas Oncogénicas/antagonistas & inhibidores , Proteínas Oncogénicas/genética , Poliploidía , Interferencia de ARN , ARN Interferente Pequeño/metabolismo , Proteína p53 Supresora de Tumor/deficiencia , Proteína p53 Supresora de Tumor/genética , Proteína p53 Supresora de Tumor/metabolismoRESUMEN
MCT-1 oncoprotein accelerates p53 degradation by means of the ubiquitin-dependent proteolysis. Our present data show that induction of MCT-1 increases chromosomal translocations and deregulated G(2)-M checkpoint in response to chemotherapeutic genotoxin. Remarkably, increases in chromosome copy number, multinucleation, and cytokinesis failure are also promoted while MCT-1 is induced in p53-deficient cells. In such a circumstance, the Ras-mitogen-activated protein kinase/extracellular signal-regulated kinase kinase-mitogen-activated protein kinase signaling activity and the expression of metastatic molecules are amplified. Given a p53-silencing background, MCT-1 malignantly transforms normal breast epithelial cells that are satisfactory for stimulating cell migration/adhesion and tumorigenesis. Detailed analyses of MCT-1 oncogenicity in H1299 p53-null lung cancer cells have shown that ectopically expressed MCT-1 advances xenograft tumorigenicity and angiogenesis, which cannot be completely suppressed by induction of p53. MCT-1 counteracts mutually with p53 at transcriptional levels. Clinical validations confirm that MCT-1 mRNA levels are differentially enriched in comparison between human lung cancer and nontumorigenic tissues. The levels of p53 mRNA are comparatively reduced in a subset of cancer specimens, which highly present MCT-1 mRNA. Our results indicate that synergistic promotions of chromosomal imbalances and oncogenic potency as a result of MCT-1 expression and p53 loss play important roles in tumor development.
Asunto(s)
Carcinoma de Pulmón de Células no Pequeñas/genética , Proteínas de Ciclo Celular/genética , Inestabilidad Cromosómica , Neoplasias Pulmonares/genética , Proteínas Oncogénicas/genética , Proteína p53 Supresora de Tumor/genética , Aneuploidia , Animales , Antineoplásicos Fitogénicos/farmacología , Carcinoma de Pulmón de Células no Pequeñas/metabolismo , Carcinoma de Pulmón de Células no Pequeñas/patología , Adhesión Celular/fisiología , Proteínas de Ciclo Celular/metabolismo , Movimiento Celular/fisiología , Proliferación Celular , Análisis Citogenético , Sinergismo Farmacológico , Etopósido/farmacología , Femenino , Citometría de Flujo , Humanos , Immunoblotting , Técnicas para Inmunoenzimas , Neoplasias Pulmonares/metabolismo , Neoplasias Pulmonares/patología , Ratones , Ratones Endogámicos BALB C , Microscopía Fluorescente , Mutágenos/farmacología , Proteínas Oncogénicas/metabolismo , Proteínas Proto-Oncogénicas c-raf/genética , Proteínas Proto-Oncogénicas c-raf/metabolismo , Proteínas Proto-Oncogénicas p21(ras)/genética , Proteínas Proto-Oncogénicas p21(ras)/metabolismo , Translocación Genética , Células Tumorales Cultivadas , Proteína p53 Supresora de Tumor/metabolismoRESUMEN
Tumor suppressor p53 protein mediates checkpoint controls and the apoptotic program that are critical for maintaining genomic integrity and preventing tumorigenesis. Forced-induction of MCT-1 decreased p53 expression before and after genomic insults. While inhibiting protein synthesis, the levels of ubiquinated-p53 and the phospho-MDMA2 were significantly increased in ectopic MCT-1 cells. Abrogation of the proteosome degradation process attenuated p53 destabilization and p21 down-regulation by MCT-1. Concomitantly, MCT-1 overexpression enhanced the phosphorylation status of MAPK (ERK1/ERK2). While MCT-1 gene knockdown or MEK/ERK pathway inhibition dramatically reduced MAPK phosphorylation, the genotoxin-induced p53 and p21 production were noticeably elevated. Upon Etoposide treatment, ectopic MCT-1 cells relaxed S-phase and G2/M checkpoints followed by G1 phase progressing. Moreover, cells inducing with MCT-1 abridged accumulations of G2/M populations in the response to gamma-irradiation. The polyploidy (DNA content>4N) populations were increased in association with p53 loss in MCT-1 oncogenic cells. Alkaline comet assay validated that ectopic MCT-1 cells were less susceptibility to the genotoxicity. Furthermore, the allocation of nuclear MCT-1 induced by the genotoxic stress was moderately coincided with gamma-H2AX appearances. Throughout damage-repairing process, ectopic MCT-1 cells displayed many larger chromosomes and multiple chromosomal fusions compared to the controls that showed increase in chromosomal breaks/gaps and minute chromosomal fragments. Spectral karyotyping analysis precisely identified the acquisition of a single extra copy of chromosome 14 together with a complex genome organizations in ectopic MCT-1 cells, including extra copies of chromosome segments that had been translocated to derivative chromosomes 6 [der(6)] and 9 [der(9)]. In conclusion, MCT-1 deregulates p53-p21 network and impairs the damage checkpoints those are robustly connected to oncogenic chromosomal abnormalities.