Concentration and schedule dependence for the induction of DNA damage by gemcitabine plus MK-8776 in MDA-MB-231 cells. A. Cells were incubated with the indicated concentration of gemcitabine for 24 h without, or concurrently with 1 μmol/L MK-8776. Cell lysates were analyzed by western blotting. B. Cells were incubated with 1–10 nmol/L gemcitabine for 0 – 24 h, without or with 1 μmol/L MK-8776. The 24-h sample incubated with 1 nmol/L gemcitabine was run on the other western blots to compare band intensities. C. Cells were incubated with or without gemcitabine for 0–24 h, and MK-8776 was added for the last 2 h. D. Cells were incubated with or without gemcitabine for 24 h, and MK-8776 was added concurrently or for the final 6, 4 or 2 h. Parallel cultures were incubated with MK-8776 alone. Cell lysates were analyzed by western blotting.