Abstract: Objective Treat the Jab1 as targets to investigate the effects and possible mechanisms that the emodin effects on the pancreatic cancer cells. Methods Determine the protein expression of Jab1 and Smad4 in the PANC-1 and AsPC-1 cell lines with Western Blot method. The 293T cells were randomly divided into control group (no treatment), emodin group (20μmol / L emodin), Jab1 group (transfected with HA-Jab1 plasmid)；Determine the binding between the β-TrCP1 and Smad4 with the IP method in the 293T cells. Determine the level of Smad4 protein expression between control group and emodin group using Western Blot method .Results Jab1 was highly expressed and Smad4 protein expression was low in pancreatic cancer cell lines, both of which were negatively correlated（P＜0.05）. Jab1 can induce the binding of Smad4 and β-TrCP1 and promote Smad4 protein degradation in the 293T cells; emodin increase the level of Smad4 by inhibiting the binding betweenβ-TrCP1 and Smad4（P＜0.05）. Conclusion Contract to Jab1, emodin play an anti-tumor role by inhibiting the degradation of Smad4,which is probably by inhibiting ubiquitin pathway enzymes.

Key words: Emodin, Pancreatic cancer, Ubiquitin ligase, Smad4, Jab1