Knockdown of miR-21-5p significantly reduced the expression levels of PI3K, AKT, and p-FOXO1 and stimulated apoptosis of Cal27 and SCC9 cells, suggesting that inactivation of PI3K/AKT/FOXO1 signaling is an effective therapeutic strategy for tongue squamous cell carcinoma (TSCC). This evidence concerns the gene PIK3CA and tongue squamous cell carcinoma.