Abstract. The transcription factor neuron-restrictive silencer factor (NRSF), also termed repressor element 1-silencing transcription factor (REST), has been previously demonstrated to repress the expression of neuronal genes in non-neuronal cells, facilitating the controlled development and organization of nerve tissue. However, previous studies have reported NRSF/REST to be upregulated or downregulated in multiple types of carcinoma. Liver diseases are a major global health concern, with cirrhosis and liver carcinoma among the most common causes of mortality worldwide. A previous study demonstrated that there were >400 NRSF/REST target genes in mouse liver cells; however, the expression profile of NRSF/REST in human liver disease remains unclear. The present study examined NRSF/REST expression in human normal and liver carcinoma samples using tissue microarray immunohistochemistry. The results demonstrated that in normal liver tissues, NRSF/REST can be detected in the cytoplasm and nuclei of the cell; whereas in the liver carcinoma tissue, NRSF/REST is only detected in the cytoplasm. Furthermore, the number of samples with high levels of NRSF/REST was significantly lower in cholangiocellular carcinoma samples compared with normal tissues. Additionally, no detectable sex-or age-associated differences were identified in NRSF/REST expression among all the tissues examined. In conclusion, the results of the present study revealed nuclear loss of NRSF/REST in hepatic carcinomas and decreased expression of NRSF/REST in cholangiocellular carcinoma, indicating that the cytoplasmic translocation of NRSF/REST may be involved in liver tumorigenesis. A low expression level of NRSF/REST may be a novel biomarker for cholangiocellular carcinoma.
IntroductionNeuron-restrictive silencer factor (NRSF), also termed repressor element 1-silencing transcription factor (REST), is a zinc-finger transcription factor and an important regulator of neural genes (1). Chong et al (2) first reported that NRSF/REST is a silencer protein that reduces the expression of sodium channel genes in neurons. A previous study demonstrated that NRSF/REST is an important regulator of neurogenesis in vitro and in vivo. For example, downregulation of NRSF/REST in embryonic stem cells induces neuronal lineage differentiation (3), and knockdown of NRSF/REST in cultured neural stem cells induces the expression of pro-neuronal genes, including neuronal differentiation 1, neuron-specific class III β-tubulin and doublecortin (4). In Xenopus and chicken embryos, NRSF/REST inactivation induces abnormal neurogenesis and inhibits the repression of neuronal tubulin and several other neuronal target genes (5,6). Additionally, NRSF/REST overexpression represses the expression of neuronal genes, including N-tubulin and neuronal cell adhesion molecule (7).Numerous studies have investigated the expression and, to a lesser extent, the function of NRSF/REST in tumors of the nervous system (8-15). Certain tumors, including neuroblastoma, share a number of biological propert...