Identification of the optimum schedule for combining gemcitabine and MK-8776. The four indicated cell lines were incubated with gemcitabine for 6 h, and 2 μmol/L MK-8776 was added concurrently (column 2) or for a 6-h period at various times after removal of gemcitabine. After removal of drugs, cells were incubated for an additional 6–7 days and cell growth assayed based on DNA content. Experiments were performed in a 96 well format and results are expressed as 50% inhibition of growth of the culture. The values represent the mean and range for duplicate experiments. In addition, the mean and SEM of the values for additional experiments at 0 and 18–24 are presented in Table 1C.