Studies On Crossed Resistance To Chemotherapy And Radiotherapy Of Human Ovarian Cancer Paclitaxel-resistant Subline

The ovarian cancer is a kind of common malignant tumor which seriously threatens the women's life and health. Its incidence ranks the 3rd place carcinoma,while its mortality rate is the highest in the gynecologic malignant tumor.That ovarian cancer cells is resistant to radiotherapy and chemotherapy is the main reason for poor prognosis. So study about the mechanism why the resistance effect occurred will provide great importance to improve the curative effect and prolong the patients's life both in the theoretical and practical fields.Now related researches focused on the impact of the radiotheraphy on chemotherapy drug-resistant cells or on the effect of chemotherapy resistance on of the sensitivityy of radiotheraphy. But the cross-resistance of ovarian tumor about radiotherapy and chemotherapy in vitro experiment is fairly limited in quantity and lack comprehensive explorance.In our study, we chose A2780 human ovarian cancer cell line and its paclitaxel-resistant subline A2780/Taxol as subject. On the one hand, we compare and analysis the radio-sensitivity of A2780 cell line and its paclitaxel-resistant subline of A2780/Taxol of human ovarian cancer to accquire the information of the influence of multidrug resistant on radiation sensitivity to ovarian cancer cells;On the other hand, we also compare and analysis the changes in drug resistant protein levels both before and after radiotheraphy of A2780 cell and its parental A2780 cells to firstly investigate the mechanism of crossed resistance to chemotherapy and radiotherapy in human ovarian cancer.which is our study's purpose and main content.AIM:1. Study on the radiosensitivity of A2780/Taxol cells: Radiating multidrug resistant cell line A2780/Taxol and its parental cell line A2780 with 60Coγ-rays to find out whether there might be any cross-resistance between multidrug resistance and radioresistance in the multidrug resistant A2780/Taxol cells. Analysis the effect of multidrug resistant on radiation sensitivity to ovarian cancer cells.2. Compare and analysis the changes of the drug resistant protein expression of P-gp ,MRP1 ,PKC-α, P53 in A2780/Taxol cells and its parental A2780 cells investigate the effect of radiation on the multidrug resistant to ovarian cancer cells.3. To firstly investigate the mechanism of crossed resistance to chemotherapy and radiotherapy in human ovarian cancer.METHODS:1. MTT assay was used to determine the sensitivity of the cells to paclitaxel and radiation;The cell growth curves of multidrug resistant A2780/Taxol cells and its parental A2780 cells were detected by MTT assay ;The cell gowth curve was drawn with the cell growth time as horizontal axis and the OD as vertical axis,and then the cell population doubling time(TD)was calculated.2. Radiation sensibility of cells was calculated by colony formation test.3. Flow cytometry (FCM) was used to detect the cell apoptosis and cell cycle;4. The protein expressions of P-gp,MRP1,P53 and PKC-αin the cells before and after radiation.were studied by Western Blot.RESULTS:1. It has been found that the resistance index (RI) of A2780/Taxol cells was up to 43.96(P< 0. 01);Study on the biological character of A2780/Taxol cells :The cell growth curves of A2780/Taxol cell and A2780 cell were drawn by using MTT assay.The cell population doubling time(TD) of A2780/Taxol cell was 25.91 hours,while that of A2780 cell was 23.65 hours,which meant that the TD of A2780/Taxol cell was about 2 hours longer than that of A2780 cell;2. 60 Coγ-irradiation induced the apoptosis of A2780 cells significantly in a dose-dependent manner ,while A2780/Taxol cells exhibited higher radioresistance. The G1 phase cells arrested progressively and the ratio of S phas cell decreased in A2780 cells ,while the ratio of G1 phase cells and of S phase cells increased in A2780/Taxol cells after exposure to 4 Gy60Coγ-irradiation in a time-dependent manner.3. The protein expressions of P-gp,MRP1,P53 and PKC-αin the cells before and after radiation.were studied by Western Blot.(1). A2780 cells : the expression of P-gp protein,MRP1 protein,PKC-αprotein and P53 protein in A2780 cells increased after irradiation with 2Gy ,4Gy and 8Gy(P<0.05) ;(2) A2780/Taxol cells: the expression of P-gp protein ,PKC-αprotein in A2780/Taxol cells increased after irradiation with 2Gy(P<0.05);the expression of P53 protein in A2780/Taxol cells increased after irradiation with 2Gy and 8Gy(P<0.05);(3)A2780 cells and A2780/Taxol cells:the expression of P-gp protein in A2780/Taxol cells was significantly higher than A2780 cells before and after irradiation with2Gy ,4Gy and 8Gy (P<0.01) ;the expression of MRP1 protein in A2780/Taxol cells was significantly higher than A2780 cells before and after irradiation with 8Gy (P<0.01) ;the expression of PKC-αprotein in A2780/Taxol cells was higher than A2780 cells before and after irradiation with2Gy (P<0.05) ;the expression of P53 protein in A2780/Taxol cells was higher than A2780 cells before irradiation(P<0.05);CONCLUSIONS:1. PTX -resistant cell line A2780/Taxol is significantly radioresistant, There might be significantly cross-resistance between multidrug resistance and radioresistance in the multidrug resistant A2780/Taxol cells.2. Radiation can change the expression of drug resistant protein levels, induce and increase the multidrug resistant in human ovarian cancer.3. Drug and radiation can induce and increase the overexpression of P-gp protein and PKC-αprotein,that may be one of the main reasons of crossed resistance to chemotherapy and radiotherapy in human ovarian cancer.