Studies have shown that miR‐21 is associated with prognosis of colorectal cancer, esophageal cancer, and hepatocellular carcinoma.15, 16, 17 Recent study has also shown that miR‐21 participates in the development and progression of bladder cancer through transforming growth factor‐beta variants or PPP2R2A/ERK.18 In recent years, study has found that GAS5 can inhibit metastasis of liver cancer cells by inhibiting miR21 in hepatocellular carcinoma.19 The gene discussed is GAS5; the disease is urinary bladder cancer.