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RLIP76 Transports Vinorelbine and Mediates Drug Resistance in Non–Small Cell Lung Cancer

¹ Department of Chemistry and Biochemistry, University of Texas at Arlington, Arlington, Texas and ² Department of Human Biological Chemistry and Genetics, University of Texas Medical Branch at Galveston, Galveston, Texas

Requests for reprints: Sanjay Awasthi, Department of Chemistry and Biochemistry, 502, Yates Street, Science Hall Room # 223, University of Texas at Arlington, Arlington, TX 76019-0065. Phone: 817-272-5444; Fax: 817-272-3808; E-mail: sawasthi{at}uta.edu.

Vinorelbine (Navelbine), an amphiphilic semisynthetic Vinca alkaloid, has displayed superior activity and decreased resistance in the treatment of advanced non–small cell lung cancer (NSCLC) compared with other members of its class. Recently, vinorelbine and cisplatin combination chemotherapy has been shown for the first time to confer a significant survival advantage in early-stage lung cancer after surgical therapy. The biological mechanisms underlying the differential response of NSCLC to cytocidal activity of vinorelbine have yet to be elucidated. Our recent findings indicate a role of RLIP76, a non–ATP binding cassette transport protein, in catalyzing the ATP-dependent efflux of structurally and functionally unrelated chemotherapeutic agents such as doxorubicin and vinblastine in NSCLC. Present studies were conducted to assess whether RLIP76 mediates vinorelbine transport and resistance. Here we show that RLIP76 catalyzes the transport of vinorelbine in a saturable manner with respect to vinorelbine (K_m 75 nmol/L) and ATP (K_m = 3.4 mmol/L). Three-fold overexpression of RLIP76 in NSCLC and SCLC confers increased resistance to cytotoxicity. RLIP76 overexpression causes a sustained intracellular decrease in vinorelbine concentration because of increased efflux, and anti-RLIP76 antibodies sensitize lung cancer cells to vinorelbine by inhibiting its efflux. These studies for the first time show that RLIP76 mediates vinorelbine transport and is capable of conferring drug accumulation defect and resistance to lung cancer cells.

Key Words: Navelbine • Lung Cancer • Transport • Drug Resistance • RLIP76

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