The results of this study indicate that overexpression of mir-21 has a negative effect on the expression of CCL28, NR3C2, and SYNPO2 and plays a significant role in the progression of gastric cancer, whereas suppression of mir-21 with anti-mir-21 has an effect on the expression of CCL28, NR3C2, and SYNPO2. This evidence concerns the gene SYNPO2 and gastric cancer.