RESUMEN
NDRG (N-Myc downstream-regulated gene)-2 is a member of the NDRG family. Although it has been suggested that NDRG2 is involved in cellular differentiation and tumor suppression, its intracellular signal and regulatory mechanism are not well known. Here, we show the differential expression of NDRG2 in human colon carcinoma cell lines and tissues by reverse transcription-polymerase chain reaction and immunohistochemical analyses with monoclonal antibody against NDRG2. NDRG2 was strongly expressed in normal colonic mucosa and colonic adenomatous tissues (25 of 25) but not in all invasive cancer tissues [44 of 99 (44%)]. Most distinctive results indicated that the high expression level of NDRG2 has a positive correlation with tumor differentiation and inverse correlation with tumor invasion depth and Dukes' stage of colon adenocarcinoma. To investigate the roles of NDRG2 in tumorigenesis, we used in vitro cell culture system. SW620 colon cancer cell line with a low level of intrinsic NDRG2 protein was transfected with NDRG2-expressing plasmid. TOPflash luciferase reporter assay showed that the transcriptional activity of T-cell factor (TCF)/lymphoid enhancer factor (LEF) was reduced by NDRG2 introduction, but not by the introduction of mutant NDRG2 generated by deletion or site-directed mutagenesis. Intracellular beta-catenin levels were slightly reduced in the NDRG2-transfected SW620 cells and this regulation of beta-catenin stability and TCF/LEF activity were mediated through the modulation of glycogen synthase kinase-3beta activity by NDRG2 function. Our results suggest that NDRG2 might play a pivotal role as a potent tumor suppressor by the attenuation of TCF/beta-catenin signaling for the maintenance of healthy colon tissues.
Asunto(s)
Adenocarcinoma/metabolismo , Neoplasias Colorrectales/metabolismo , Regulación Neoplásica de la Expresión Génica , Factores de Transcripción TCF/genética , Proteínas Supresoras de Tumor/metabolismo , beta Catenina/genética , Adenocarcinoma/genética , Adenocarcinoma/secundario , Western Blotting , Membrana Celular/metabolismo , Colon/metabolismo , Neoplasias Colorrectales/genética , Neoplasias Colorrectales/patología , Citosol/metabolismo , Femenino , Humanos , Técnicas para Inmunoenzimas , Inmunoprecipitación , Luciferasas/metabolismo , Masculino , Persona de Mediana Edad , Estadificación de Neoplasias , Fosforilación , Regiones Promotoras Genéticas , ARN Mensajero/genética , ARN Mensajero/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Transducción de Señal , Factores de Transcripción TCF/metabolismo , Transcripción Genética , Transfección , Células Tumorales Cultivadas , Proteínas Supresoras de Tumor/genética , beta Catenina/metabolismoRESUMEN
We explored whether adipocyte culture medium affects the secreted chemokine profile of tumor cells, because adipocytes stimulate progression or metastasis of breast cancer cells, and chemokines secreted from tumor cells are involved in these processes. CCL20 expression was dramatically increased, and an NF-kappaB blocker completely inhibited adipocyte culture medium-induced CCL20 expression in MDA-MB-231 cells. We showed that adipocyte culture medium increased the production of TNF-alpha in MDA-MB-231 cells, which stimulated CCL20 expression in an autocrine fashion. Our data also showed that CCL20 increased the migration and invasiveness of MDA-MB-231 cells, but did not affect the proliferation of these cells.