Figure 4. MK-8776 and VE-821 do not block Chk1 phosphorylation.
(A) OVCAR-8 cells were pretreated with vehicle (−), MK-8776 (0.3 and 1.0 µM), or VE-821 (1.0 or 4.0 µM) for 15 min and then exposed to cisplatin (4 µM), topotecan (TPT, 20 nM), veliparib (10 µM), or gemcitabine (Gem, 20 nM) for 4 h in the continued presence of MK-8776 or VE-821. (B) SKOV3 cells were pretreated with vehicle (−), MK-8776 (0.3, 1.0, and 4 µM), or VE-821 (1.0, 4.0, and 6.0 µM) for 15 min and then exposed to 20 nM gemcitabine for 4 h. (C, D) MiaPaCa (C) or U937 (D) cells were pretreated with vehicle (−), MK-8776 (0.3 and 1.0 µM), or VE-821 (1.0 or 4.0 µM) for 15 min and then exposed to gemcitabine (40 nM, MiaPaCa cells; 20 nM U937 cells) for 4 h. Cell lysates were then immunoblotted for the indicated antigens.