Abstract: Objective:To investigates the effects of RASAL 2 on invasion and migration of gastric cancer cells and the role of RASAL 2 in epithelial-mesenchymal transition (EMT). Methods:SNU-1, SNU- 16, and AGS gastric cancer cell lines were used as in vitro experimen -tal models. RNAi technology was used to establish stable RASAL2 knockdown cell lines, and RASAL2-expressing lentivirus was used to establish cells expressing upregulated RASAL2. To determine the impacts of RASAL 2 on migration and invasion, we performed Tran-swell migration and invasion assay, together with wound healing assay. Immunofluorescence and Western blot assays were performed to explore the role of RASAL 2 in EMT of gastric cancer cells. Furthermore, Western blot assay was performed to investigate the effects of RASAL 2 on activation of Ras-ERK pathway. Results:Both target sites could significantly downregulate RASAL2 expression in SNU- 16 and AGS cells. The number of migrating and invading cells decreased in cells expressing upregulated RASAL 2 compared with that in scrambled controls. Similar results were obtained in wound healing assay. The epithelial marker E-cadherin was downregulated after RASAL 2 knockdown, whereas the mesenchymal marker vimentin was upregulated. Snail, a transcriptional regulator of EMT, was also upregulated in RASAL 2 knockdown cells. Ras-ERK pathway was activated after RASAL2 inhibition. Moreover, RASAL 2 overexpression in SNU-1 inhibited cell migration. Conclusion: RASAL 2 negatively regulates invasion and migration of gastric cancer cells and plays a vital role in EMT of these cells. The biological function of RASAL 2 is at least partly dependent on Ras-ERK pathway.