Recent literatures reported that Claudin 1 is up-regulated in several cancers, such as cervical cancer, colorectal cancer, gastric cancer and melanoma, and has a close relationship with cancer progression 26, while it is down-regulated in breast carcinoma, liver cancer, prostate cancer and glioblastoma and shows a tumor suppressive role26, 27. The gene discussed is CLDN1; the disease is prostate cancer.