Taxol Analogues Exhibit Differential Effects on Photoaffinity Labeling of β-Tubulin and the Multidrug Resistance Associated P-Glycoprotein

Several next-generation taxanes have been reported to possess high potency against Taxol-resistant cancer cell lines overexpressing βIII-tubulin and/or P-glycoprotein (P-gp), both of which are involved in drug resistance. Using a photoaffinity Taxol analogue, 2-(m-azidobenzoyl)taxol, two potent next-generation taxanes, SB-T-1214 and SB-CST-10202, exhibited distinct inhibitory effects on photolabeling of β-tubulin from different eukaryotic sources that differ in β-tubulin isotype composition. They also specifically inhibited photolabeling of P-gp, and the inhibitory effect correlated well with the steady-state accumulation of [3H]vinblastine in a multidrug resistant (MDR) cell line, SKVLB1. Several microtubule-stabilizing agents (MSAs)-resistant cell lines from the human ovarian cancer cell line Hey were isolated, and their MDR1 and βIII-tubulin levels determined. Distinct potencies of the two taxanes against different MSA-resistant cells expressing unique levels of MDR1 and βIII-tubulin were found. Cytoto...