Figure 4.

Effect of alectinib on the efflux of Rho 123, ATPase activity and the [¹²⁵I]-IAAP photoaffinity labeling of ABCB1 and ABCG2. The cells were pre-incubated with 5 μM Rho 123 at 37 °C for 30 min and then incubated with alectinib for the indicated time points in Rho 123-free media. Rho 123 retention was measured by flow cytometry in KB, KBv200, S1 and S1-MI-80 cells (a, b). The vanadate-sensitive ABCB1 or ABCG2 ATPase activity was evaluated in the presence of the indicated concentrations of alectinib (c, d). Alectinib competed for photolabeling of ABCB1 or ABCG2 by [¹²⁵I]-IAAP. A representative autoradiogram is shown for three independent experiments. The relative amount of [¹²⁵I]-IAAP incorporated was plotted against the concentration of alectinib present. Hundred percent incorporation refers to the absence of alectinib (e, f). The data points represent the mean±s.d. of at least three independent experiments. **P<0.01.