Fig. 4

ICEC0942 and THZ1 resistance can be reversed by ABC-transport inhibitors. MCF7, and MCF7-942^R were treated with increasing concentrations of ICEC0942 or THZ1 for 48 h with addition of the ABCB1 inhibitors, verapamil or tariquidar (at indicated concentrations), or with vehicle (DMSO) (a–d). MCF7, and MCF7-THZ1^R were treated with increasing concentrations of THZ1 for 48 h with addition of the ABCG2 inhibitors, novobiocin (e) or KO-143 (f) (at indicated concentrations), or with vehicle (DMSO). The sum-of-squares F test was used to assess whether the addition of ABCB1/ABCG2 inhibitors significantly affected the GI₅₀ of ICEC0942 and/or THZ1, in MCF7-942^R and MCF7-THZ1^R. The corresponding F (degrees of freedom in brackets) and P values are presented (a–f). Dose-response curves shown are from single experiments (error bars = SEM, n = 6). For clarity, the vehicle control growth curves for MCF7 and MCF7-THZ1^R have been presented in both e, f