Effects Of Ursolic Acid On The Proliferation, Apoptosis And Cisplatin Sensitivity Of Human Ovarian Cancer Cells

Background:Clinical drug resistance to platinum-based chemotherapy is considered a major impediment in the treatment of human ovarian cancer.Multiple pathways associated with drug resistance have been suggested by many previous studies. Deregulation of proapoptotic and antiapoptotic pathways are key players in the onset and maintenance of chemoresistance in advanced ovarian cancers.Eventually resistant tumor cells manifest as inhibition of the activation of Caspase-3,and reduction of apoptosis.Ursolic acid has been shown to inhibit the proliferation and induce apoptosis in many tumors in vitro and in vivo,but not have been proved in ovarian cancer,especially in cisplatin-resistant phenotype.Moreover the effect of combination therapy with cisplatin on reversing chemo-resistance has not been identified.Objective:The goal of this study was to investigate the effects of ursolic acid on the proliferation,apoptosis and cisplatin sensitivity in human ovarian cancer cell line COC1 and its cisplatin-resistant subline COC1/DDP,and to explore its possible mechanism preliminarily.Methods:We used MTT assay to assess the proliferation inhibiting rates,flow cytometry(FCM) to measure the apoptotic rates,fluorescence staining technique of living cells to observe the morphologic changes of cell apoptosis,colorimetric assay to detect the activation of Caspase-3 and the immunochemistry method to test the expression of apoptosis-related protein Caspase-3.Results:5～40μmol/L ursolic acid could evidently inhibit the proliferation of both cells in a dose and time-dependent manner.1.25～10μg/mL DDP combined with 20μmol/L ursolic acid could decrease the survival rates of COC1/DDP cells (P＜0.05).20μmol/L ursolic acid could increase the apoptotic rates(P＜0.05) and Caspase-3 activation(P＜0.05) in both cells,and could make cells show the typical morphological characteristics of apoptosis.The apoptotic rates and the Caspase-3 activation of COC1/DDP cells treated with DDP combined with ursolic acid were significantly higher than those with DDP alone(P＜0.05).Conclusion:The evidences provided by this study lend strong support for our hypothesis that ursolic acid had the anti-tumor activity and to some extent could overcome cisplatin-resistance in ovarian cancer cells as documented by inhibiting cell proliferation and promoting induction of apoptotic cell death.The mechanism may be related to increase the activation of Caspase-3.Our results warrant further pre-clinical animal model and clinical studies for assessing the value of ursolic acid in treating ovarian cancer alone or combined with cisplatin and reversing the chemotherapy resistance.