Study On Synergistically Therapeutic Effect Of Valproic Acid And Cisplatin On Human Prostate Cancer PC3, DU145 Cells And Its Underlying Molecular Mechanism

Objective:To analyze the effects of valproic acid(VPA) alone or VPA in combination with cisplatin(DDP) on inhibition of proliferation and induction of apoptosis of human prostate cancer PC3 and DU145 cells in vitro, and to explore the possible molecular mechanism of synergistically therapeutic effect of VPA and DDP. To evaluate the therapeutic effect of VPA alone or VPA in combination with DDP via Xenograft mouse model established with prostate cancer cell DU145. Thus, the aim of current study is to offer preliminary data for further development of novel clinical strategy against prostate cancer.Method:1. In vitro cell experiments: The survival rates of PC3 and DU145 cells under the treatment of VPA, DDP or VPA in combination with DDP were analyzed by MTS assay,the survival curve were drawn and the differences were statistically analyzed. The degradation of apoptosis related proteins RARP and Caspase8, and the expression level of anti-apoptotic protein Survivin under the treatment of VPA,DDP or VPA in combination with DDP were analyzed by Western blot.2. Xenograft mouse model experiments: Xenograft mouse model were established by subcutaneously injection of prostatic cancer DU145 cell. Mice with Xenograft tumors were randomly divided into 4 groups, which received treatment of Saline as control, VPA alone, DDP alone, or VPA in combination with DDP. The growth of Xenograft tumors was dynamically monitored and growth histograms were drawn.3. In vivo imaging experiments: After treatment for 20 days, all mice were subjected to anaesthesia and growth of Fluc-labeled prostatic cancer DU145 cells in vivo, the light images and fluorescence intensity was followed through noninvasive bioluminescence imaging using the Xenogen IVIS system.Results:1. MTS results showed that the Survival rates of both PC3 and DU145 were gradually decreased upon treatment with increased concentration of VPA or DDP. VPA was shown to exhibit significantly synergistic effect on inhibition of the survival of PC3 and DU145 while in combination with DDP.2. Upon treatment with VPA or DDP alone, the cleavage of RARP and Caspase8, as well as the down-regulation of Survivin in PC3 and DU145, were shown to be increased with a time-dependent manner by Western blot. These effects were further enhanced in PC3 and DU145 upon treatment with VPA in combination with DDP. These results indicated that VPA and DDP may have synergetic effects on prostate cancer cells.3. Upon treatment with VPA alone, DDP alone, or VPA in combination with DDP, the mean tumor volume was significantly smaller than that of the control, with the tumor volume be the smallest in group receiving treatment with VPA in combination with DDP.4. The bioluminescence of Xenogragft tumor of each group were detected by the IVIS200 imaging instrument. The fluorescence signal intensity of VPA in combination with DDP group is the weakest. The fluorescence signal intensity of single drug group VPA or DDP was weaker than that of control group, and the difference between each groups was shown to be statistically significant(P<0.05).Conclusion:Our results indicate that VPA alone can significantly induce the inhibition of the proliferation, as well as apoptosis of human prostate cancer PC3 and DU145 cells.The synergistically therapeutic effect of VPA and DDP were demonstrated both in vitro and in vivo here. Our preliminary mechanism study suggests that VAP may potentiate the induction of apoptosis of prostate cancer PC3 and DU145 cells by DDP via down-regulation of anti-apoptotic protein Survivin.That of mechanism can reduce DDP resistance of prostate cancer cells and triggering apoptosis.