Dickkopf-1 is involved in invasive growth of esophageal cancer cells

Dickkopf-1 (DKK1) is an inhibitor of Wnt/beta-catenin signaling pathway. High levels of DKK1 protein were found in a series of cancers. However, the role of DKK1 in the progression of esophageal carcinoma is not fully understood. In the present study, RT-PCR and Western blot were used to detect the expression of DKK1 in esophageal carcinoma tissues, matched adjacent normal esophageal tissues, and esophageal carcinoma cell lines. Our results showed that the expression of DKK1 was upregulated on both mRNA and protein levels in esophageal carcinoma tissues compared with the adjacent normal esophageal tissues, meanwhile, in four esophageal carcinoma cell lines analyzed, expression of DKK1 was detected with different levels. Immunohistochemistry and immunofluoresence revealed that the distribution of DKK1 was mainly in the cytoplasm in both carcinoma tissues and cell lines. To further explore the biological effects of DKK1 on proliferation, cell cycle and invasion capability, we constructed the eukaryotic expression vector pCMV-Tab-2b-DKK1 which can effectively overexpress DKK1. Subsequently, we observed that exogenous expression of DKK1 in EC9706 cell line resulted in an increased rate of proliferation, and S stage and G2/M stage ratio whereas G0/G1 ratio was decreased. In order to evaluate the invasion capability Boyden chamber was analyzed which implied that overexpression of DKK1 resulted in an increase in the invasion ability in EC9706 cell line. Taken together, the study indicates that DKK1 might be a key regulator in the progression of esophageal carcinoma and a potential therapeutic target in esophageal carcinoma.