Abstract: Objective:To discuss the role for down-regulation of JNK enzymatic activity in the tumor treatments by interrupting JNK gene expression with JNKinhibitor SP600125 and JNK-siRNA encapsulated by lipid nanoparticles in vivo and in vitro. Methods:In vitro experiments, the experiment was divided into siRNA group and inhibitor SP600125 group. In siRNA group,JNK-siRNA and NC-siRNA were transfected into the human prostate cancer cells (PC cells), human hepatocellular carcinoma cells(SMMC-7721 cells) and human breast cancer cells(MCF cells), respectively. In inhibitor SP600125 group, SP600125 was delivered to human hepatocellular carcinoma cells. The expression levels of JNK or p-JNK proteins in human prostate cancer cells,human hepatocellular carcinoma cells,and human breast cancer cells after transfected with JNK-siRNA and inhibitor SP600125 were detected by Western blotting method. The cell viabilities of tumor cells in various groups were examined by WST-1 proliferation assay. In vivo experiments,the human hepatocellular carcinoma SMMC-7721 cells were used to establish the subcutaneous hepatocellular carcinoma xenograft tumor models by subcutaneous injection. The eight mice were fed until the tumors were generated to 3 mm×3 mm. They were randomly divided into inhibitor SP600125 group and negative control group,JNK-siRNA group and NC-siRNA control group. Each mouse in various groups was injected intratumorally with 5 nmol SP600125,negative control solution, lipid nanoparticles-mediated JNK-siRNA and NC-siRNA negative control. The volumes of tumors of the mice in various groups were observed. The expressions of JNK or p-JNK proteins in tumor tissue were examined by immunohistochemical staining. Results: In vitro experiments, compared with NC-siRNA control group, the expression level of JNK protein in human prostate cancer cells, human hepatocellular carcinoma cells and human breast cancer cells in JNK-siRNA group were decreased(P<0.01); the expression level of p-JNK protein in human hepatocellular carcinoma cells in inhibitor SP600125 group was significantly increased compared with its negative control group(P<0.01).In vivo experiment, the human hepatocellular carcinoma cells were taken as an example, the volume of tumor of the mice in inhibitor SP600125 group was significantly reduced compared with negative control group, whereas the change of tumor volume in JNK-siRNAs group was not significant compared with NC-siRNA control group. The immunohistochemical staining results showed that compared with their negative control groups, the expression amount of p-JNK protein in tumor tissue of the mice in SP600125 group and the expression amount of JNK protein in tumor tissue of the mice in JNK-siRNA group were decreased (P<0.01). Conclusion:Down-regulation of enzymatic activity of JNK can decrease the expression level of JNK gene and then inhibit the tumor growth both in vivo and in vitro.

Key words: prostate neoplasms, hepatocellular carcinoma, breast neoplasms, lipid nanoparticle, c-Jun N-terminal kinase, RNA interference, enzymatic activity