Zhang et al. Journal of Experimental & Clinical Cancer Research 2010, 29:88 http://www.jeccr.com/content/29/1/88 R E S E A R C H Open Access The E-cadherin repressor slug and progression of human extrahepatic hilar cholangiocarcinoma Ke-jun Zhang1*†, Dong-sheng Wang1†, Shao-yan Zhang2†, Xue-long Jiao1, Chun-wei Li1, Xin-sheng Wang3, Qin-chao Yu3, Hai-ning Cui4 Abstract Objectives: This study explored the expression and function of Slug in human extrahepatic hilar cholangiocarcinoma (EHC) to identify its role in tumor progression. Methods: The expression of Snail and Slug mRNA in 52 human tissue samples of EHC was investigated. The mRNA of Snail and Slug were quantified using reverse transcriptase-PCR, and correlations with E-cadherin expression and clinicopathological factors were investigated. We then investigated transfection of Slug cDNA in endogenous E-cadherin-positive human EHC FRH0201 cells, selectively induced the loss of E-cadherin protein expression, and then small interfering RNA (siRNA) for inhibition of Slug expression in endogenous Slug-positive human EHC QBC939 cells, selectively induced the loss of Slug protein expression. A Boyden chamber transwell assay was used for invasion. Results: Slug mRNA was overexpressed in 18 cases (34.6%) of EHC compared with adjacent noncancerous tissue. E-Cadherin protein expression determined in the same 52 cases by immunohistochemistry was significantly down- regulated in those cases with Slug mRNA overexpression (P = 0.0001). The tumor and nontumor ratio of Slug mRNA was correlated with nodal metastasis(p = 0.0102), distant metastasis (p = 0.0001)and Survival time(p = 0.0443). However, Snail mRNA correlated with neither E-cadherin expression nor tumor invasiveness. By inhibiting Slug expression by RNA interference, we found that reduced Slug levels upregulated E-cadherin and decreased invasion in QBC939 cell. When the QBC939 cells was infected with Slug cDNA, significant E-cadherin was downregulated and increased invasion in QBC939 cell. Conclusions: The results suggested that Slug expression plays an important role in both the regulation of E-cadherin expression and in the acquisition of invasive potential in human EHC. Slug is possibly a potential target for an antitumor therapy blocking the functions of invasion and metastasis in human EHCs. Introduction Cholangiocarcinoma is a cancer arising from bile duct epithelium. It is one of the most difficult diseases to treat. Three-year survival rates of 35 to 50% can be achieved in only a few numbers of patients when nega- tive histological margins are attained at the time of sur- gery [1]. The reason for this poor prognosis is that cholangiocarcinoma exhibits extensive local invasion and frequent regional lymph node metastasis[2]. but the mechanisms through which Cholangiocarcinoma * Correspondence: wlsdermyy@163.com † Contributed equally 1General Surgery, the Affiliated Hospital of medical College, Qingdao University, Qing dao, Shandong Province. 266003. China acquires such invasive potentials are not well understood. E-Cadherin-mediated cell-to-cell adhesion plays a critical role in the maintenance of cell polarity and environment [3]. E-Cadherin was reported to be down- regulated and closely related to tumor invasion and metastasis in many cancers[4-6] . Genetic and epige- netic alteration of E-cadherin was also reported [3] . Somatic mutation, loss of heterozygosity of the E-cad- herin gene, and CpG methylation around the promoter region of the E-cadherin gene were noted in human gastric cancer, breast cancer, and Hepatocarcinoma [7-11]. However, E-cadherin promoter hypermethyla- tion is not always associated with loss of expression [11], and evidence has been presented that E-cadherin © 2010 Zhang et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.