Abstract: ObjectiveTo determine the expression of tight junction protein CLDN1 in esophageal squamous carcinoma (ESCC) and to explore the effect of CLDN1 on the biological function of ESCC TE-11 cells. MethodsThis study collected 30 ESCC tissues, 30 adjacent normal tissues and 30 distal esophageal tissues to detected the expression of CLDN1 in tissue microaary by immunohistochemistry method. Western blot was employed to determine the expression of CLDN1 in 15 ESCC tissues and cell lines, and then the distribution of CLDN1 in tumor cells and normal esophageal epithelial cells was analyzed. Lentivirus containing the sequence of CLDN1 shRNA was constructed and transfected into TE-11 cells, the transfection efficiency and intracellular distribution was determined by Western blot and flow cytometry. Cell proliferation was detected by CCK-8, the invasion and migration ability of cells was determined with Transwell. Cytoskeleton changes was observed by laser scanning confocal microscope. ResultsImmunohistochemical results showed no significant difference between the cancer tissues and adjacent tissues in term of the positive rate of CLDN1 ( P>0.05). CLDN1 was highly expressed in highly and moderately differentiated ESCC tissues, but its expression was significantly decreased in poorly differentiated cancer tissues. Western blot revealed that CLDN1 was mainly distributed in the nucleus of TE-11 cells. The proliferation of TE-11 cells, as well as invasion and migration ability, were declined obviously when the expression of CLDN1 being down-regulated, while the cytoskeleton protein fluorescence intensity deceased.ConclusionThe expression of CLDN1 in ESCC tissue is associated with its differentiation and may promote carcinogenesis in TE-11 cells.