To further explore the roles of DKK4 in CRC, we established gain-of-function models of DKK4 in Caco-2 and HCT8 cells through lentivirus infection and established loss-of-function models of DKK4 in SW480 and HCT116 cells using a lentiviral vector carrying shRNA (Fig. 2, A and B). The gene discussed is DKK4; the disease is lentivirus infection.