Background and Aims: Previous studies have demonstrated that microRNA-124 (miR-124) plays an important role in a variety of cancers, and is down-regulated in gastric cancer cells and tissues. This study was conducted to investigate the influences of miR-124 on proliferation and apoptosis of gastric cancer cells and its association with PI3K/Akt signaling pathway.  
Methods: The expressions of miR-124 in human gastric cancer cells MGC803, AGS, MNK-45 and SGC-7901 as well as in normal gastric mucosa epithelial GES-1 cells were determined by qRT-PCR. In MGC803 cells after transfected with miR-124 mimics (miR-124 mimics group) and negative control sequences (negative control group), the cell proliferation was detected by CCK-8 assay and cell clone assay, the apoptosis was measured by flow cytometry, the protein expressions of PI3K, Akt, p-PI3K and p-Akt were examined by Western blot, and mRNA expressions of PI3K and Akt were analyzed by qRT-PCR. 
Results: The expressions of miR-124 in all studied gastric cancer cell lines were all significantly lower than that in normal gastric mucosa epithelial GES-1 cells (all P<0.05). In miR-124 mimics group compared with negative control group after transfection, the OD450 values of and numbers of cell clone formation were all significantly reduced (all P<0.05); the apoptosis rates were all significantly increased (all P<0.05); the expression levels of PI3K, Akt, p-PI3K and p-Akt proteins from PI3K/Akt signaling pathway were significantly down-regulated (all P<0.05) and the gene expression levels of PI3K and Akt were also significantly down-regulated (all P<0.05). 
Conclusion: Down-regulation of miR-124 can promote proliferation and inhibit apoptosis of gastric cancer cells, and the mechanism may probably associated with the activation of PI3K/Akt signaling pathway.