To evaluate whether abnormal expression of CLDN6 enhanced tumorigenicity of gastric cancer in vivo, gastric cancer cells transfected with sh-CLDN6 and empty vector constructs, were injected subcutaneously and into the spleen of nude mice, respectively, to generate xenograft subcutaneous tumor model and liver metastasis model (Fig. 4a, e). The gene discussed is CLDN6; the disease is gastric cancer.