Increased ETV4 expression correlates with estrogen-enhanced proliferation and invasiveness of cholangiocarcinoma cells

Background: Cholangiocarcinoma (CCA) is one of the worst prognosis cancer. The survival time of CCA patients is related to serum estrogen levels and estrogen has been found to enhance the proliferation and invasiveness of CCA cells in vitro. This has led to the suggestion that estrogen may play an important role in the progression of CCA. This study tests the relevance of the previous in vitro findings in vivo using a mouse xenograft model of CCA, and investigates possible signaling mechanisms involved. Methods: KKU-213 and KKU-139 CCA cell lines were used in the experiments, xenografted to nude mice and treated with a potent estrogenic agent, 17 beta-estradiol (E2), and/or with tamoxifen (TAM), an estrogen antagonist. Results: The results demonstrated that E2 could accelerate growth of the xenograft-tumor and the effect was inhibited by TAM. PCR array screening of E2 responsive genes suggested ETV4 as a promising candidate intracellular mediator. ETV4-knockdown CCA cells were generated and these showed a diminished responsiveness to E2 in both cell and spheroid proliferation assays, and in invasion tests. These results point to ETV4 as a possible mediator of E2-activated CCA progression and as a potential target of TAM-mediated inhibition. Conclusions: Finally, TAM may be suggested as an adjunctive treatment of CCA to improve the conventional cytotoxic method with more patient toleration.