A semisynthetic cabazitaxel analogue,C1 overcomes P-gp-meditaed multidrug resistance in non-small-cell lung cancer

OBJECTIVE To investigate the effect of C1 against P-glycoprotein(P-gp)-meditaed multidrug resistance(MDR) in non-small-cell lung cancer cells. METHODS Human non-small-cell lung cancer(NSCLC) cell lines A549, H1299, H460, normal lung cell lines MRC5,taxol-resistant daughter line A549/TR and cisplatin-resistant daughter A549/CR were used to achieve this objective. Cell proliferation was analyzed by cytotoxicity assay,P-gp ATPase activity in vitro was detected by P-gp-Glo?Assay System, P-gp activity in vivo was determined by FACS analyses of intracellular accumulation of Rh123 in A549/TR and A549/CR cells, anti-tumor effect of C1 and taxol were evaluated by parental and drug-resistant cell xenograft of nude mice. RESULTS Cytotoxicity assay results showed that C1 potently inhibits cell proliferation in NSCLC cell lines but not in normal lung cells. However,C1 was more efficacious than taxol in the A549/TR-and A549/CR-treated cells that overproduced P-gp. The drugefflux function of P-gp depends on the ATP hydrolysis that reflects ATPase activity. Taxol, the most widely used taxoid in NSCLC treatment, could inhibit P-gp ATPase activity at lower concentrations, but stimulated it at higher concentrations. In contrast, C1 could significantly inhibit P-gp ATPase activity in a concentration-dependent manner.When the drug-resistant cells were treated in the presence of C1 at 0.1, 0.2 and 0.4 μmol·L-1, the intracellular accumulation of rhodamine 123 was higher than that in A549/TR and A549/CR treated with taxol at the same concentrations, respectively. These results indicated that C1 can reduce drug efflux through inhibiting the transmembrane pumping function of P-gp but not decreasing the expression of P-gp protein. We next compared the efficacy of TM2 and taxol in vivo using A549, A549-Taxol,and A549-CDDP xenograft models. In parental and drugresistant cell xenograft, C1 could significantly inhibit tumor growth in a dose-dependent manner. The TGI for the group receiving docetaxel treatment(8.5 mg · kg~(-1)) was 46.06% and 87.88% for the C1-treated group(10 mg·kg~(-1))in A549 xenografts. The maximal TGI of C1 was 80.4% in A549/TR xenografts, and 54.5% in A549/CR xenografts. Importantly, C1 produced a significant inhibition of tumor growth in drug-resistant cell xenografts, compared with taxol at the same dosing schedule and frequency.Additionally, C1 did not cause reduced body weight of the host mice or other side effects such as hair loss, mortality,and lethargy. CONCLUSION C1 overcomes P-gp-mediated MDR by directly inhibiting its transport function.