A Preliminary Study On Inhibitory Effect Of Smac Combined With Cisplatin In Nude Mice Xenografts Of DDP-resistant Ovarian Carcinoma

ObjectiveTo investigate the antitumor effect of Smac combined with cisplatin on human ovarian carcinoma cells xenografts in nude mice, to analyze the expression of Smac and XIAP protein, apoptosis rate of the xenografts and MVD, and to preliminarily study the inhibitory effect and probable mechanism of decreasing the ovarian cancer’s chemoresistance with the combination of Smac and cisplatin.MethodsHuman ovarian cancer models transplanted subcutaneously in nude mice were established, and divided into5groups. N.S.(group Ⅰ), DDP (group Ⅱ), empty plasmids and DDP (group Ⅲ), recombinant Smac plasmids (group IV) as well as Smac plasmids and DDP (group Ⅴ) were injected into the tumor-bearing mice with Lipofect to interfere with the growth of transplanted tumor. All of these medicine were injected once every three days, for five times in total. The effect on the volume and inhibitory rate of the tumor were observed. The level of Smac, XIAP expression in tumor tissue was determined by western blot. The cell apoptosis in tumor tissues was detected by TUNEL. Immunohistochemistry was employed for calculating micro vascular density(MVD).ResultsThe xenografts of resistant ovarian cancer in each nude mice were established and grown successfully. The transplanted tumor volume in group Ⅱ Ⅲ Ⅳ Ⅴ were significantly smaller than that of the negative control group Ⅰ, and the transplanted tumor volume in group Ⅱ Ⅲ Ⅳ are lower than that of the group V(p＜0.05). The mean tumor inhibition rates of each group were16.42%,21.46%,42.72%,72.94%. In western blot, Smac alone or combined with DDP can up-regulate the expression of Smac and the difference compared with other three groups is significant(p＜0.05). Only Smac+DDP group down-regulated the expression of XIAP in transplanted tumor, and the difference has statistic meaning(p＜0.05). Each group’s apoptosis index detected by TUNEL was (19.90±3.18)%,(21.82±4.40)%,(22.64±3.81)%,(30.23±4.06)%,(48.59±4.47)%. MVD in each group was (24.8±5.36),(21.2±3.11),(19.8±3.70),(14.4±3.85),(11.6±2.70). The MVD of Smac+DDP group was the lower than other four groups, and has statistic significance compared with group Ⅰ,Ⅱ,Ⅲ.(p＜0.05).Conclusion1.The combination of Smac and cisplatin could significantly inhibit the growth of transplanted human resistant ovarian cancer in nude mice. And Smac and cisplatin have a synergistic effect on inducing the apoptosis of the resistant ovarian cancer cells.2. Smac could enhance the sensitivity of ovarian carcinoma xenograft to cisplatin chemotherapy.3.Smac can suppress tumor angiogenesis. That may be one of the mechanisms to explain why Smac could suppress the grow of ovarian cancer xenografts and strengthen the sensitivity of the resistant ovarian cancer to cisplatin.