| Objective Ovarian cancer is one of the common cancers in women and is responsible for more deaths than any other gynecologic cancer. No means of early detection has been discovered. Consequently, more than half of the malignancies are unresectable when first diagnosed. At present, postoperative patients or those who cannot be operated often need chemotherapy to enhance the survival rate. So it is very important to choose chemotherapy drugs and their combination method. CDDP is almost the first line drug of ovarian cancer chemotherapy and the second line drugs are often needed to combine with it for better curative effect. It is found recently, the combination of VP-16 and CDDP has a synergistic effect on ovarian cancer, but its mechanism is not very clear. In present studies, the ability to induce cell apoptosis of drugs is the most objective marker for chemotherapy. Both VP-16 and CDDP work through inducing cell apoptosis. Caspase-3, the effective enzyme of caspase family, is the final way of apoptosis, it can degradate the substrate after being inactivated, then induce cell apoptosis. Bcl-2, bax are anti-apoptosis factor and apoptosis factor of bcl-2 family respectively. Bcl-2 restrains the activation of caspase-3 but bax stimulates it; and it can accelerate the development of the tumor but bax can restrain the progress. It is found that most chemotherapy drugs can induce cell apoptosis through regulating the expression of apoptosis-related factors. So, in this study, we combined VP-16 in peak serum concentration and various concentrations of CDDP to induce Skov3 cell apoptosis. And with this method, we expected to evaluate the combined effect of the two drugs from the aspects of morphology, cytology, especially the changes of apoptosis-related factors, and to explore the combined mechanism of them. Therefore, we could provide more theoretical basis for clinical chemotherapy. Methods 1 Skov3 cell line was maintained in RPMI-1640 supplemented with BS (10%). Cells were divided into three groups referring to PSC of drugs CDDP 3μg/ml, VP-16 5μg/ml: ①normal group ②CDDP group: Skov3 cells were exposed to CDDP in 0.3μg/ml, 1μg/ml, 2μg/ml, 3μg/ml, and 30μg/ml respectively. ③VP-16+CDDP group: Skov3 cells were exposed to VP-16 in PSC combined with CDDP in 0.3μg/ml, 1μg/ml, 2μg/ml, 3μg/ml, 30μg/ml respectively. 2 MTT method was applied to detect the inhibitory effect on cell growth of each experiment group. 3 FCM was applied to detect the Skov3 apoptosis ratio of each group. 4 The growth states and morphological changes of Skov3cells after treated with drugs were observed under inverted microscope; and morphological changes of apoptotic cells were observed through HE stain. 5 S-P ICC method was used to determine the expression of apoptosis-related factors bcl-2, bax, caspase-3 in Skov3 cells of each group, and to explore the mechanism of the two drugs. 6 Statistical analysis: two sample student's-t test and Wilcoxon test were performed. P<0.05 were considered statistically significant. Results 1 MTT results: it was showed that there was a synergistic effect on Skov3 cells when treated with VP-16 in PSC combined with various concentrations of CDDP, and in the low concentration scope of CDDP (less than PSC), the synergistic effect was more obvious with higher concentration of CDDP; and VP-16 in PSC combined with CDDP in PSC showed the highest synergistic effect, Q=1.16(++); but there was decreased synergistic effect with high concentration of CDDP (10PSC), Q=0.93(+). 2 Apoptosis ratios were detected by FCM: in the pictures of FCM histogram, apoptosis peaks were detected in both CDDP and VP-16+CDDP groups. The apoptosis ratio depended on concentration, and in low concentration scope of CDDP(less than PSC), the apoptosis ratios of VP-16+CDDP group were significantly higher than that of CDDP group (P<0.05), but not in high concentration(10PSC) (P>0.05).3 Morphological changes of Skov3 cells: ①under the inverted microscope, Skov3 cells growed well, stuck to the coverglass well, with clear contour, well-stacke...
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