Drug resistance is one of the major obstacles to chemotherapy of ovarian cancer. Studies with cell lines can serve as an initial screen for agents that might modulate drug resistance. To establish more appropriate models of drug resistance and explore whether the differences exist in the different drug resistant sublines selected by different treatments, we induced SKOV3 cell line using cisplatin (CDDP) and Taxol over a period of 16 months by the pulse (SKOV3/CDDP-P and SKOV3/Taxol-P) and intermittent incremental (SKOV3/CDDP-80 and SKOV3/Taxol-25) method, respectively. The resistant phenotype of the four resistant sublines, SKOV3/CDDP-P, SKOV3/CDDP-80, SKOV3/Taxol-P and SKOV3/Taxol-25, was very stable and the resistance index was 4.12, 11.50, 261.98 and 622.76, respectively. In cell morphology, the cells from pulse treatment had remarkable changes compared with the cells from intermittent incremental treatment. SKOV3/CDDP-80 and SKOV3/Taxol-P grew more slowly than SKOV3/CDDP-P and SKOV3/Taxol-25. Multidrug resistance gene 1, multidrug resistance protein 1, lung resistance protein and glutathione S-transferase pi mRNA expression of SKOV3/CDDP-P and SKOV3/Taxol-25 had greater changes than that of SKOV3/CDDP-80 and SKOV3/Taxol-P. The results suggest there are great differences between the resistant cell lines resulting from pulse and intermittent incremental method. The resistant cells selected by the intermittent method were more resistant than the cells selected by the pulse method. The two resistant sublines selected by the pulse method may serve as appropriate models for the study of mechanisms of drug resistance in ovarian cancer.

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