Received: 27.10.2010 Accepted: 17.01.2011 J Gastrointestin Liver Dis March 2011 Vol. 20 No 1, 19-26 Address for correspondence: M. B. Irmak-Yazicioglu Department of Molecular Biology and Genetics, Faculty of Arts and Sciences, Halic University, Kaptanpasa Okmeydanı, Istanbul, Turkey Email: burcuyazicioglu@halic.edu.tr silencing of the MMP-3 Gene by siRNA transfection in Gastric Cancer AGs Cells Salih Gencer 1 , Anıl Cebeci 2 , Meliha Burcu Irmak-Yazicioglu 1*,2 1) Department of Genetics and Bioengineering, Faculty of Engineering, and Department of Biology, Faculty of Arts and Sciences, Fatih University, Buyukcekmece; 2) Department of Molecular Biology and Genetics, Faculty of Arts and Sciences, Halic University, Kaptanpasa, Okmeydani, Istanbul, Turkey. 1*) Previous Address: Department of Biology, Faculty of Arts and Science, Fatih University, Buyukcekmece, Istanbul, Turkey Abstract Background. The gastric epithelium is continuously exposed to toxic reactive oxygen species and matrix metalloproteinases (MMPs) are the enzymes known for their roles in the invasion of tumor cells. Here, we report the suppression of matrix metalloproteinase 3 (MMP-3) in gastric cancer cell line AGS by small interfering RNA (siRNA) transfection and its potential role in gastric cancers. Methods. Oxidative stress in the cell lines was assessed following H 2 O 2 exposure using an oxidative stress marker, 2,7-dichloroluorescein diacetate (DCFDA). Transfection of cells with small interfering RNA speciic to MMP-3, Transwell invasion assay, quantitative reverse transcriptase polymerase chain reaction analysis, and over-expression of MMP-3 were used to determine the potential role of MMP-3 gene in gastric cancers. Results. The silencing of the MMP-3 gene resulted in a decrease of invading AGS while the over-expression of it caused an increase in the invading cells compared to the untreated control cells. Moreover, it also caused a 4.1 fold increase in matrix metalloproteinase 10 (MMP-10) and a 7.4 fold decrease in matrix metalloproteinase 15 (MMP-15) mRNA expression levels. Conclusions. Our results show that the silencing of the MMP-3 gene decreases the number of invading AGS cells and additionally, affects the expressions of MMP-10 and MMP-15, suggesting that targeting the MMP-3 gene in gastric cancers might be a therapeutic approach due to its effects on the invasion of AGS cells and the expression of the MMP-15 gene. Key words Gastric cancer – AGS – invasion – MMP-3 – siRNA. Introduction Gastric cancer is the second most common cause of cancer-related deaths worldwide [1]. The gastric epithelium is exposed to toxic reactive oxygen species (ROS) within the gastric lumen due to ingested food, cigarette smoke, and inlammation due to the Helicobacter pylori infection. The dynamic balance between cell proliferation and apoptosis is essential for maintaining mucosal homeostasis. Decreased apoptosis with increased proliferation may favor the carcinogenic process. The prolonged survival of abnormal cells can support the accumulation of sequential genetic mutations, changes in gene expression proiles and protein structure and function which can result in tumor promotion [2-6]. The involvement of ROS signaling and the importance of matrix metalloproteinases (MMPs) in tumor metastasis are highlighted [7]. MMPs are enzymes that are involved in the digestion of the components of the extracellular matrix (ECM), cell surface receptors for soluble factors and junctional proteins and physiological processes such as tissue remodeling, but also in the stimulation of tumor growth, invasion, and metastasis [8]. Studies have shown that the expression of MMP-3 in the mammary glands of transgenic mice causes the production of invasive carcinomas by stimulating epithelial- mesenchymal transition [9], acting as a natural tumor promoter and enhancing cancer susceptibility in mammary glands of transgenic mice [10]. Moreover, the transformed rat embryo cell lines with high metastatic potential were found to produce high levels of the MMP-3 and MMP-10 [11]. Additionally, it has been documented that tumor necrosis factor (TNF) alpha enhances the invasiveness of T98G glioma cells through MMP-3 induction [12]. RNA interference (RNAi) is an endogenous process to regulate gene expression to maintain the homeostasis. The technology of RNAi that uses small interfering RNA (siRNA) is an effective method that is used to silence the genes [13-15]. The roles of certain MMPs have been revealed by siRNA transfection in gastric cancers. Among the membrane type MMP genes, MMP-14 and MMP-15 were