We found that gastric cancer lesions overexpressed miR-21 in 25/63 cases (39.7%) and lower-expressed Mel-18 in 38/63 cases (60.3%) compared to corresponding non-tumor gastric mucosal tissues, and Spearman coefficient correlation analysis showed a negative correlation between Mel-18 and miR-21 expression at RNA level (r=−0.321, P=0.009), supporting the finding of Mel-18 negatively regulating the expression of miR-21. Here, PCGF2 is linked to gastric cancer.