Effect Of HDAC Inhibitor On Histone Acetylation And The Expression Of ASC In LS174T Cells

Objective: The normal expression of gene is necessary for cell growth and development. An increasing number of experiments show that the structure changes of chromatin and nucleosome play an important role in the regulation of gene transcription. Core histone acetylation and deacetylation is closely related to gene expression.The histone acetyl trans- ferase (HAT) and histone deacetylase (HDAC) have function in histone acetylation and deacetylation. They are two mutual antagonism functional enzymes. For HAT, it can acetylate N-terminal of histone, loose the stru- cture of the nucleasome and active gene transcription, while the latter cata- lyze the removal of an acetyl group from theε-amino group of lysing side chains of histones. The dynamic equilibrium of HAT and HDAC impacts the expression of special genes. As the key protease to gene expression, HDAC had been proved to have direct effect on tumorigenesis and tumor development. By suppress HDAC, the tumor can be treated. HDAC inhibitor (HDACi) was developed recently, which represent a new class of anticancer drugs. Some had been applied in clinical. HDAC inhibitor has been found causing cell growth arrest, differentiation and apoptosis.At present, the colon cancer is a high hazard type of the digestive mali- gnnant tumors, its incidence has ranked the fourth place in the common tumors following lung cancer, gastric carcinoma and hepatoma. In 2008, the incidence of colon cancer is ranked the second in malignant tumor in Shanghai. Moreover, the growth trend of its incidence in recent years has become very obvious. According to statistics, the colon cancer incidence rised in China (5%) is much faster than the international normal level (2%). There was 400,000 new cases of colon cancer been diagnosed each year, mainly was middle-aged person, and its high incidence age is at about 50 years old. Therefore, the pathogenesis research and clinical treatment was paid more attention by many scholars.Apoptosis-associated speck-like protein (ASC) was first found as a detergent insoluble protein. It participates in retinoic acid-induced apo- ptosis and forms tungsten filament structure in cells. ASC can be considered as a tumor suppressor gene, which involved in the regulation of apoptosis, caspase-inflammation, NF-κB activation and so on. ASC is fully expressed in many epithelial cells, white blood cells, hair follicles and peripheral blood lymphocytes. The expression of ASC can be regulated by modification of DNA methylation and histone acetylation. It had been reported that ASC was abnormally methylated and silenced in human breast cancer cells. In addition, the ASC expression is abnormal in leukemia, bile duct cancer, colon cancer and prostate cancer tumors, which has made widespread concern by researchers. In order to assess sodium butyrate (NaBu) on the role of apoptosis and the feasibility of its application in tumor treatment, we investigate the effect of NaBu on histone H3 acetylation and the expression of ASC in LS174T cells.Methods: Total proteins and mRNA were extracted from LS174T cells treated with or without NaBu in different concentrations (1, 5, 10 mmol/L) or at various time (12, 24, 48, 72hours). By using Western blot,the states of acetylated histone H3 and ASC expression were assayed. RT-PCR was used to detect the expression of ASC mRNA. The proliferation rate of the cell was detected by MTT assay, and the apoptosis rate was measured by using flow cytometry (FCM).Results: Histone H3 acetylation was obviously increased by NaBu at a time-and dose-dependent manner. The expression of ASC mRNA and pro- tein was regulated by NaBu. While the up-regulate of ASC causes more apoptosis of LS174T cells.Conclusion: The acetylation of histone H3 as well as the expression of ASC was up-regulated by NaBu. The resumption expression of ASC moder- ately induces LS174T cells apoptosis.