| OBJECTIVE:Multidrug resistance (MDR) is a formidable roadblock to the effective treatment of ovarian cancer by conventional chemotherapy and affecte the five-year survial rate of ovarian cancer. The multidrug resistance phenotype in nature (inherited) or acquired form expresses resistance to a variety of drugs,not only to the drug used in the therapy,but also to a broad spectrum of unrelated cytotoxic drugs. Current evidence suggests that this resistance is due to the changes in genes,proteins,lipids,apoptosis,signal transduction and the ability of cancer cells to reduce the absorpt of drug,lower intracellular drug concentration,relieve the toxin of drug. Recently,some scientists have payed attention to the neutral glycosphingolipids in MDR. In this study,the author investigated the expressing of CMH (Monohexosylceramide),Bcl-2 and Bax in ovarian cisplatin-resistant cell line COC1/DDP and its parent cisplatin-sensitive cell line COC1. The author also attempt to reverse the resistance by a MDR modulator mifepristone,explore the changes in apoptosis and the expressing of CMH,Bcl-2,Bax. The aim of the study is to elucidate the importance and affection of CMH,Bcl-2,Bax in MDR of ovarian cancer,and to provide new ideals and clues to seek new effective methods for therapy and reversing the MDR in ovarian cancer as well.METHODS:COC1/DDP cells were treated with mifepristone in different concentration.The expresses of Bcl-2 and Bax in cell linesCOC1 and COC1/DDP (before and after the treatment of mifepristone) were detemined by flow cytometry (FCM). COC1 and COC1/DDP (before and after the treatment of mifepristone) were colleted and N-GSLs (neutra glycosphingolipids) of the cells was isolated and purifide with the modifide Hakomori's method,changes of CMH content were analyzed by HPTLC (high performance thin layer chromatography). The alterations of chemosensitivity to cisplatin (DDP) were evaluated by MTT (the tetrazolium dye) assay. The forms of COC1/DDP cells treated by mifepristoe,cisplatin,or mifepristone and cisplatin were observed by transmission electron microscope (TEM). DNA ladders in COC1/DDP treated by mifepristone,cisplatin,or mifepristone and cisplatin were presented by DNA gel electrophoresis.RESULTS:The positive rate of Bcl-2 in COC1/DDP cells was 23.81% +0.44%,which was higher than that in COC1 cells expressing 0.88% + 0.07% ( P< 0.001). The positive rate of Bax in COC1/DDP cells was 12.75% +0.60%,which was lower than that in COC1 cells expressing 15.42%+ 0.25% ( P<0.05). Treated by 1.25 w mol/L,5 u mol/L mifepristone,the positive rate of Bcl-2 in COC1/DDP was reduced to 19.40% + 0.69%,14.23% + 0.44% respectively ( P<0.001),while the positive rate of bax in COC1/DDP was increased to 25.60%+0.88%,33.89%+ 0.28% respectively ( P< 0.001). The levels of CMH were 37.14%+ 3.34% in COCl/DDP,higher than that in COC1 14.05% + 1.44% ( P< 0.001). After treating by 1.25 u mol/L,5 u mol/L mifepristone,the CMH were 26.62%+ 2.63% (P<0.05) and 17.50% + 0.67% ( P< 0.001) respectively. Mifepristone had no effect on the viability of COC1/DDP at the consentration between 1.25u mol/L and 5.0 u mol/L,but inhibited the cell proliferation at the consentration above 5.0 u mol/L. The combinated treatment of 1.25u mol/L mifepristone and cisplatin could reduce the cell viability in COC1/DDP ( P < 0.05),increasing the sensitivity of the cell to cisplatin,thecombination of 5.0 u mol/L mifepristone and cisplatin had more obvious effect ( P<0.001). After the combined treatment,the COCI/DDP cells turned round,lack of microvillus,consentration of cytoplasm,endoplast enlarging like bubbles,chromatin condensing like crescent moon and so on. The combinated treatment elicited DNA fragmentation,however,cisplatin nor mifepristone alone could potentiate DNA fragmentation.CONCLUSION:1. The expression of Bcl-2 and Bax in COCI/DDP were different signifecently cells from that in COCI cells. 2. The levels of CMH in COCI/DDP cells were much higher than that in COCI cells. 3. Mefipristone increased the sensitivity of COCI/DDP cells...
|
PDF Full Text Request