Silencing β-catenin Influence The Biological Behaviors Of Gastric Cancer Cells

Background：Gastric cancer is a common tumor, majority of patients have been late stagewhen diagnose as gastric cancer and lose the opportunity of operation,leading to theshort lifetime and poor life. In recent years, β-catenin was discovered as a proteininvolved to cancer and high express in a wide variety of tumor cells. β-catenin wasassociated with the proliferation, apoptosis, invasion, metastasis and chemotherapysensitivity of tumor. But more study of β-catenin were conduct in colorectal, breast,liver, etc,while less in gastric carcinoma cells. In this study we used RNAi technologyto silence β-catenin’s expression in gastric cancer cells, to study whether this changecould influence the biological behavior of gastric cancer cells.Objective：To observe the impact of silencing the expression of β-catenin gene on theproliferation, invasive, apoptosis and the drug susceptibility of gastric carcinoma cells.We aim to acquire new treatment programs of gastric cancer. And preliminarilyexplore its molecular mechanism, which would provide a new way for the diagnosisand treatment of gastric cancer.Methods：1. Made β-catenin-RNAi Lentivirus and β-catenin-negative Lentivirus to infectAGS cells and MGC803cells, later we let two kinds of Lentivirus. Then tested themRNA and protein expression of intracellular β-catenin by quantitative real time-RTPCR and Western blot assay.2. Tested the sensitivity of5-Fu in each groups cells by MTT, includingexperimental group, negative control group,blank control group.3. Tested the ablity of migration and invasion in AGS cells and MGC803cellsby Transwell assay, including before and after down-regulating the expression ofβ-catenin. 4. Tested the cell cycle and apoptosis after gastric carcinoma cells were infectedwith β-catenin-RNAi-433-LV by flow cytometry.5. Detected the expression of β-catenin downstream target protein (C-Myc、cyclin D1、Bcl-2、Bax、MMP-7、DPD、TS) by western blot assay.Results：1. β-catenin silenced by transfecting β-catenin siRNA into AGS cells andMGC803cells, β-catenin mRNA level in those two experimental groups cells wasdecreased conspicuously, as well as the results of β-catenin expression tested bywestern blot. But the expression of β-catenin in negative control groups had nochanged.2. MTT showed that the sensitivity to5-Fu in AGS-RNAi-433cells andMGC803-RNAi-433cells were significantly increased after down-regulating theexpression of β-catenin.3. Transwell assay proved that the ability of migration and invasion inAGS-RNAi-433cells and MGC803-RNAi-433cells were all inhibited afterdown-regulateing the expression of β-catenin.4. Flow cytometry delected that cells in G1phase were increased while S phasewere decreased after silenced the expression of β-catenin in both AGS-RNAi-433cells and MGC803-RNAi-433cells.At the same time, the apoptosis of those twokinds cells after silenced β-catenin expression were increased.5. Western blot assay discovered the expression of cyclin D1, c-Myc, Bcl-2,MMP-7, TS were decreased after silencing β-catenin expression(P＜0.05). At thesame time, we found the expression of Bax was increased in cells which have lessβ-catenin expression(P＜0.05), while the expression of DPD had no change.Conclusion：1. In gastric carcinoma cells, silencing the expression of β-catenin could delaycell proliferation, promote its apoptosis, weaken the invasive power of cells andincrease the sensitivity of5-Fu.2. In gastric carcinoma cells, the expression of cyclin D1, c-Myc, Bcl-2, MMP-7,TS were decreased after silencing the expression of β-catenin, while the expression of Bax was increased and DPD had no change.3. Silencing β-catenin expression may depress the transition from G1phase to Sphase through reducing the expression of cyclin D1and c-Myc, inhibit the ability ofmigration and invasion of gastric carcinoma cells through reducing the expression ofMMP-7, and make cells become more sensitive to5-Fu through reducing theexpression of TS.