RESUMEN
We developed inducible and constitutive expression systems of Ha-RasV12 in HEK 293 cells to examine early oncogenic RasV12 signaling. Inducible expression of oncogenic Ras-triggered growth arrest, early senescence, and later apoptosis. Gene expression profile analysis revealed early Ras proliferation and cell cycle genes like c-fos, cyclin E, cdk2, cell-cell contact, and signaling like integrin a6, MEK5, and free radical signaling genes, like proline oxidase. Therefore, Ras-mediated signaling is a fine regulated process both positively and negatively influencing cell cycle, senescence, and apoptosis pathways. Novel early RAS-target genes could be potentially exploited in cancer diagnostics and therapeutics.
Asunto(s)
Apoptosis/genética , Transformación Celular Neoplásica/genética , Senescencia Celular/genética , Perfilación de la Expresión Génica , Regulación Neoplásica de la Expresión Génica , Genes ras , Proteínas ras/genética , Ciclo Celular/genética , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Línea Celular , Transformación Celular Neoplásica/metabolismo , Transformación Celular Neoplásica/patología , Activación Enzimática , Perfilación de la Expresión Génica/métodos , Humanos , Proteínas Quinasas Activadas por Mitógenos/genética , Proteínas Quinasas Activadas por Mitógenos/metabolismo , Mutación , Análisis de Secuencia por Matrices de Oligonucleótidos , Fosforilación , Reproducibilidad de los Resultados , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Transducción de Señal/genética , Factores de Tiempo , Transfección , Proteínas ras/metabolismoRESUMEN
Several food polyphenols act as chemopreventers by reducing the incidence of many types of cancer, especially in colon epithelia. In this study, we have investigated whether the flavonoid quercetin can modulate cell proliferation and survival by targeting key molecules and/or biological processes responsible for tumor cell properties. The effect of quercetin on the expression of Ras oncoproteins was specifically studied using systems of either constitutive or conditional expression of oncogenic RAS in human epithelial cells. Our findings suggest that quercetin inhibits cell viability as well as cancer cell properties like anchorage-independent growth. These findings were further supported at the molecular level, since quercetin treatment resulted in a preferential reduction of Ras protein levels in cell lines expressing oncogenic Ras proteins. Notably, in cells that only express wild-type Ras or in those where the oncogenic Ras allele was knocked out, quercetin had no evident effects upon Ras levels. We have shown that quercetin drastically reduces half-life of oncogenic Ras but has no effect when the cells are treated with a proteasome inhibitor. Moreover, in Ha-RAS-transformed cells, quercetin induces autophagic processes. Since quercetin downregulates the levels of oncogenic Ras in cancer cells, we propose that this flavonoid could act as a chemopreventive agent for cancers with frequent mutations of RAS genes.
