Use of decoy receptor 3 to block gemcitabine-induced apoptosis via binding with TRAIL in pancreatic cancer.

238 Background: Most of human pancreatic cancer cell lines are resistant to chemotherapeutics-induced apoptosis including gemcitabine. This study is to address the role of decoy receptor3 (DcR3) in pancreatic cancer resistant to chemotherapeutics. Methods: siRNA targeted for DcR3 was used to down-regulate DcR3 expression in pancreatic cancer cells. On exploring for the pathway of DcR3 blocking Gemcitabine-induced apoptosis, up or down-regulated DcR3 level of pancreatic cancer cells were treated with Gemcitabine and apoptosis susceptibility was evaluated with apoptosis analysis. To investigate whether DcR3 is involved in TRAIL, FasL or LIGHT-mediated apoptosis, PARP and apoptotic cells staining were determined under different DcR3 level. Through ELISA-like binding analysis, immunoprecipitation and FACS, TRAIL binding with DcR3 was tested. In vivo experiment, it is to investigate whether down-regulation of DcR3 affects gemcitabine-induced apoptosis and tumor growth delay. Results: It demonstrates that DcR3 down-regulation sensitizes cells to gemcitabine-induced apoptosis and additional DcR3 level can impair gemcitabine-induced apoptosis in both of cells. It is proved that DcR3 blocks gemcitabine-induced apoptosis via binding with TRAIL which was thought not to bind with DcR3 previously. Furthermore, Regulation of DcR3 changes the amount of membrane-bound TRAIL which is correlated with gemcitabine-stimulation. In vivo experiment of AsPC-1 xenografts, stable down-regulation of DcR3 significantly enhances gemcitabine-induced apoptosis and tumor growth delay. Conclusions: DcR3 may play important role resistant to gemcitabine-induced apoptosis via binding with TRAIL in some of pancreatic cancer cells lines. Targeting DcR3 represents a promising strategy to enhance the anti-tumor activity of chemo-agent in pancreatic cancer, which has important clinical implications.