Multidrug Resistance Gene-1 Is a Useful Predictor of Paclitaxel-Based Chemotherapy for Patients with Ovarian Cancer

Abstract Objective. The objective of this study was to determine the relationship between multidrug resistance and sensitivity to paclitaxel (PTX) in ovarian cancer. Methods. We used human ovarian adenocarcinoma cell lines, KF, a PTX-resistant cell line (KFTx), SK-OV-3, and KOC7c. Additionally, 27 patients with ovarian cancer who had residual disease were examined. All patients underwent postoperative chemotherapy consisting of 175 mg/m 2 PTX and area under curve (AUC) 5 carboplatin. The sensitivity of the cells to PTX or cisplatin (CDDP) was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. mRNA expression of multidrug resistance gene-1 (MDR-1) and multidrug resistance-associated protein-1 (MRP-1) and MRP-2 was determined by reverse transcription–polymerase chain reaction. β-Tubulin polymerization and Bcl-2 phosphorylation were examined by Western blot analysis. Results. Compared with KF, the IC 50 to PTX was 5.5-fold higher for KFTx, 0.3-fold for SK-OV-3, and 52.1-fold for KOC7c. The IC 50 to CDDP was 0.7-, 4.2-, and 5.8-fold, respectively. Expression of the MDR-1 gene was clearly observed in KFTx and KOC7c. Expression of MRP-1 was observed in SK-OV-3 and KOC7c. Expression of MRP-2 was detected only in KOC7c. CDDP enhanced β-tubulin polymerization induced by PTX in CDDP-sensitive cells. Bcl-2 phosphorylation appeared after exposure to IC 50 PTX in all cells. Twenty-one patients responded to chemotherapy and six did not. Expression of the MDR-1 gene for nonresponders was significantly higher than that for responders (260.0 ± 191.6 vs 9.3 ± 21.8). With the cutoff value of MDR-1 expression at 100, the predictive value for chemoresponse was 96%. Expression of the MRP-1 and MRP-2 genes did not differ between nonresponders and responders. Conclusion. MDR-1 gene expression may be a useful predictor for PTX-based chemotherapy.