ABCB1 and ovarian cancer: The tubulin labeling efficacy of 11, Tubulin Tracker Green, and siR-Tubulin were also compared in SK-OV-3-MDR1-M6/6 ovarian cancer cells, which express 1000-fold increased levels of the P-glycoprotein drug efflux pump MDR-1 as compared to the parental SK-OV-3 cell line (Fig. 8b and Supplementary Fig. 11).