To identify the functional role of CLDN2 in colorectal cancer, CLDN2 was knocked out in CLDN2‐high HT29 cells through CRISPR‐Cas9 and was overexpressed in CLDN2‐low HCT116 cells using plenti‐CMV‐EGFP plasmid. The gene discussed is CLDN2; the disease is colorectal cancer.