Aberrant expression of KL-6/MUC1 mucin has been proven to be associated with poorer tumor behavior in many carcinomas. The aim of this study was to evaluate the expression of KL-6/MUC1 in pancreatic cancer tissues and its potential involvement in tumor metastasis. The expression of KL-6/MUC1 in 18 cases of pancreatic ductal carcinoma (PDC), 5 cases of intraductal papillary mucinous tumor (IPMT), and 3 cases of islet cell tumor was detected by immunohistochemical staining. To determine the impact of loss of KL-6/MUC1 expression on pancreatic tumor progression, an siRNA targeting MUC1 was synthesized and transfected into Panc-1 cells and Capan-1 cells to knock down KL-6/MUC1 expression. Down-regulation of KL-6/MUC1 expression was detected by reverse transcription-polymerase chain reaction (RT-PCR) and western blotting. E-cadherin and KL-6 mucin co-expression was detected by immunofluorescence. The expression of E-cadherin and E-cadherin/β-catenin comlex was determined by immunoprecipitation. Cell invasive abilities were detected by invasion assay. Positive KL-6/MUC1 staining was observed in all 18 PDC cases (18/18,100.0%) and 1 metastatic IPMT case (1/5, 20.0%). The results suggested that KL-6/MUC1 overexpression may be associated with more aggressive tumor behavior, although the cases of pancreatic cancer tissues in this study are limited. RT-PCR and western blotting showed that both KL-6/MUC1 mRNA and protein can be effectively silenced. Following KL-6/MUC1 knockdown, E-cadherin expression increased. Also, E-cadherin/β-catenin complex expression increased and the invasive ability of the cells decreased. This study indicated that overexpression of KL-6/MUC1 in pancreatic cancer tissues may be associated with metastasis of pancreatic cancer by regulating E-cadherin and E-cadherin/β-catenin complex expression.

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