大黄素通过上调Smad4蛋白表达抑制胰腺癌细胞

Emodin inhibits pancreatic cancer cells by upregulating expression of Smad4

目的以Jab1为作用靶点探讨大黄素抗胰腺癌作用及可能的机制。方法 293T细胞随机分为对照组(不处理)、大黄素组(20μmol/L大黄素处理)、Jab1组(转染HA-Jab1质粒),用免疫印迹实验(Western blot)法测定胰腺癌PANC-1和As PC-1细胞系中Jab1与Smad4的蛋白表达。用免疫共沉淀(IP)测定大黄素组及Jab1对β-Tr CP1与Smad4结合的影响。采用Western blot法检测对照组及大黄素干预组PANC-1和As PC-1细胞系中Smad4蛋白表达。结果胰腺癌PANC-1细胞和As PC-1细胞中Jab1呈高表达,Smad4呈低表达,Jab1与Smad4呈负相关关系(P<0.01)。293T细胞中Jab1能促使β-Tr CP1与Smad4结合,促进Smad4蛋白降解;而大黄素通过抑制β-Tr CP1与Smad4结合,增加Smad4的表达水平(均P<0.05)。结论与Jab1的作用相反,大黄素可能通过抑制泛素化酶途径,抑制Smad4的降解,从而起到抗肿瘤作用。

Objective Using Jabl as targets to investigate the effects and possible mechanisms that the emodin ex- erts effects on the pancreatic cancer cells. Methods Determine the protein expression of Jabl 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 （20 μmol / L emodin） and Jab1 group （transfected with HA-Jabl plasmid） ;Deter- mine the binding between the β-TrCP1 and Smad4 with the IP method in the 293T cells. Determine the level of Smadg protein expression in control and emodin group using Western blot method. Results Jabl was highly ex- pressed and Smad4 protein expression was low in pancreatic cancer cell lines, both of which were negatively corre- lated（P 〈0. 05 ）. Jabl can induce the binding of Smadg 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）. Conclusions Contract to Jabl, emodin play an anti-tumor role by inhibiting the degradation of Smad4, which is probably by inhibiting ubiquitin pathway enzymes.