It is worth noting that several studies have used nude mice to establish tumor metastasis models, such as the liver metastasis model by injecting gastric cancer cells into the spleen [52] and lung metastasis model by tail vein injection of breast cancer cells [22,24] to observe the effect of CLDN6 on tumor metastasis, and obtained results consistent with the in vitro experiments, which profoundly demonstrated the effect of CLDN6 on tumor metastasis. The gene discussed is CLDN6; the disease is breast carcinoma.