The non-small cell lung cancer (NSCLC) cells SK-LC6 and NCI-H23 were continuously exposed to vinorelbine (VNB), and the VNB-resistant clones, SK-LC6/VNB and H23/VNB were selected. Since SK-LS6/VNB and H23/VNB cells showed cross-resistance to certain anticancer drugs, such as paclitaxel and docetaxel, we examined the gene expression levels of drug efflux transporters of the ATP-binding cassette (ABC) family. We found that the gene expression of ABCB1/MDR1 and ABCC10/MRP7 in SK-LC6/VNB and H23/VNB cells was increased compared with that in SK-LS6 and NCI-H23 cells, whereas the expression of ABCC1/MRP1, ABCC2/MRP2, ABCC3/MRP3 and ABCG2/BCRP did not change among these cells. Treatment with ABCB1/MDR1 inhibitor verapamil and ABCC10/MRP7 inhibitor sulfin-pyrazone altered the sensitivity of SK-LC6/VNB cells to vinorelbine. To confirm the ABCC10/MRP7 activity, we transfected small interfering RNA against ABCC10/MRP7 to ABCC10/MRP7-expressing RERF-LC-AI cells resulting in the decrease of ABCC10/MRP7 expression concomitant with the alteration of VNB cytotoxicity. Moreover, we detected the expression of ABCC10/MRP7 in 12 of 17 NSCLC cells, whereas ABCB1/MDR1 was detected in only 3 of 17 NSCLC cells. These results indicate that ABCC10/MRP7 may confer VNB resistance in NSCLC.

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