Abstract: Objective To study the effects of MACC1 down- regulation on the growth of gastric adenocarcinoma cells. Methods siRNA (MACC1-siRNA1 and MACC1-siRNA2) that can transiently silenced MACC1 was designed, syn⁃ thesized and transfected into MGC-803 cells by lipofectamine 2000. Non-specific siRNA was transfected to be used as nega⁃ tive control. The efficiency of MACC1 depletion was determined by Real-time quantitative PCR. MTT, colony formation and flow cytometry assay were performed to examine cell proliferation. The expressions of MACC1, P21,CDK4, CCND1 and cmyc were determined by Western blot. Results Compared with cells in negative control group, transiently silencing MACC1 decreased the expression of MACC1 in MGC-803 cells shown by Real-time PCR. MACC1 downregulation drastical⁃ ly changed the proliferation, colony formation and cell cycle of gastric adenocarcinoma cells in vitro (P＜0.05). The expres⁃ sions of MACC1 , CDK4, CCND1 and c-myc proteins in cells of MACC1 silence group were much lower while P21 expres⁃ sion level was much higher than those in negative control. Conclusion Down-regulation of MACC1 result in blocking cell cycle, inhibiting proliferation of MGC-803 cells. So it may serve as a promising target in the treatment of gastric cancer.

Key words: stomach neoplasms, adenocarcinoma, cell proliferation, cell cycle, RNA interference, MACC1, MGC-803 cell