Abstract
BACKGROUND AND OBJECTIVE: Claudin-7 is a component of tight junctions and plays important roles in maintaining cell polarity and tightly connecting the barriers between cells. Abnormal claudin-7 protein expression is closely related to tumor occurrence, development, and metastasis. This study aimed to investigate the correlation between claudin-7 expression and carcinogenesis or metastasis in colorectal cancer and the clinical significance of these relationships. MATERIALS AND METHODS: In this study, enzyme linked immunosorbent assays (ELISA) were used to measure the claudin-7 levels in serum from patients with colorectal cancer. Immunohistochemical staining and Western blotting were used to measure claudin-7 expression in colorectal cancer tissues, paracancerous tissues, and metastatic tissues. RESULTS: Serum claudin-7 levels were significantly lower in patients with colorectal cancer than in healthy controls. Immunohistochemistry indicated that claudin-7 expression was lower in colorectal cancer tissues than in normal colorectal tissues, and its expression level was positively correlated with the degree of colorectal cancer tissue differentiation. Claudin-7 expression levels were significantly reduced or undetectable in metastatic tissues compared to primary tumor tissues, but there were no significant differences in claudin-7 expression among different metastatic tissues. CONCLUSION: We confirmed that claudin-7 downregulation was associated with colorectal cancer and metastasis. Claudin-7 could be a tumor suppressor gene for colorectal cancer and may thus serve an early diagnostic marker and a novel therapeutic target.