The Function Of REST In Breast Cancer

Background and Objective:Breast cancer is the most common cancer of women and the second leading cause of female cancer mortality in the world. The mortality rate of breast cancer could be lowered by identification of novel molecular markers of early breast cancer and understanding the molecular mechanisms of the early events of breast cancer. It has been reported that there are 10-30% breast cancer show the character of neuroendocrine differentiation(NED). But the mechanism is still unclear. RE1 silencing transcription factor (REST) is generally expressed in all of epithelial cell, who in charge of the expression of neuronal gene. Dysfunction of REST took part in the NED of prostate cancer. And recently, the tumor suppression role of REST is identified. REST expression was recently shown to be absent in many other cancers, such as small cell lung cancer (SCLC), colorectal cancer and prostate cancer. Blockade of REST function in the epithelial cells is found to cause a transformation phenotype, such as anchorage-independent growth. Neither REST take part in the development of breast cancer nor REST may have relationship with the NED of breast cancer has been reported.The aim of this study is to investigate the expression of REST in breast cancer and analysis the possible role of REST in breast cancer. The results could contribute to elucidate the mechanism of tumorigenesis. It could provide a new target for the treatment of breast cancer. And also provide a new prognosis factor for breast cancer.Methods:The samples were collected. And the expression of REST, Syn, ER, PR and Her-2 were detected by Immunohistochemistry. The expression of REST and the relationship of them in the breast cancer were analyzed byχ2 test and Spearman's rank correlation analysis. To further investigate the possible role of REST in breast cancer cell, the endogenous expression of REST was shut-down by RNAi. The cell line in which REST expression was stable silenced was identified by RT-PCR and Western Blot. Growth curve and colony formation were used to detect the cell proliferation. The apoptosis of cell was detected by Hochest 33258 stain and Flow Cytometry. Single cell gel electrophoresis and MTT chemotherapy sensitivity were used to analysis the sensitivity of cell to anticancer drug. Moreover, reconstitution of REST in breast cancer cells by transgene. Flow Cytometry and Transmission electron microscope were used to analysis the apoptosis and damage of cells. The capability of migration and metastasis were detected by Transwell analysis. Western Blot was used to detect the expression of genes that associated with proliferation, apoptosis and metastasis.Results:The positive expression of REST was only 69.1% in breast cancer. The difference was significant between the breast cancer and benign breast samples (p<0.05). Also the positive percent was also declined in breast cancer in which the metastasis was happened. There was 22.1% of breast cancer showed the character of neuroendocrine differentiation(NED). Furthermore, there was negative relationship between the expression of REST and NED (p<0.01, R=-0.412). There was no significant relation among the expression of REST and ER, PR, Her-2(p>0.05).The proliferation of MCF-7 cell, in which the endogenous expression of REST was relatively high, was enhanced when REST was shut down. The expression of PI3K and p-Akt were enhanced. Also the apoptosis of MCF-7cell was reduced when REST was shut down. And concomitance with activity of Caspase-7 and c-Jun were reduced. Loss of REST expression resulted in a reduction chemosensitivity to anticancer drug. And the increasing in Bcl-2 expression was detected.The apoptosis was increased when reconstitution of REST in breast cancer cell MDA-MB-231, in which the expression of REST was relatively low. The metastasis ability of MDA-MB-231 cell was restrained when the expression of REST was up-regulated, in concomitant with the suppression of MMP-9 expression.1. The expression of REST was down-regulated in breast cancer. There was some relationship between the reduced expression of REST and the metastasis of breast cancer. The reduced expressions of REST maybe take part in the development of NED in the breast cancer. And the NED of breast cancer may promote the metastasis of breast cancer.2. The PI3K/Akt pathway was activated when the expression of RSET was shut down. This maybe results in proliferation of cells. And the apoptosis was reduced concomitance with the activation of Caspase-7 and c-Jun was decreased. All of these indicated that the role of REST was suppression of proliferation and induction of apoptosis.3. REST mediated the drug resistance in the breast cancer through increasing the expression of Bcl-2. REST maybe take part in chemotherapy resistance of breast cancer.4. REST attenuated the capability of metastasis of breast cancer cell by suppressing the expression of MMP-9.