PDCD4 and gastric cancer: Notably, miR-21 and miR-25 have been identified as significantly upregulated in GAC tissues compared to their levels in healthy controls, suggesting a potential role in tumorigenesis.8,9 MiR-21 has been implicated in the promotion of gastric cancer cell growth and invasiveness through the suppression of tumor suppressor genes, such as phosphatase and tensin homolog (PTEN) and programmed cell death protein 4 (PDCD4).10 These proteins are known to exert inhibitory effects on tumor progression, and their downregulation by miR-21 may contribute to the malignant phenotype of gastric cancer cells.