Figure 1. Identification of clinically relevant kinase inhibitors that sensitize cells to gemcitabine. (A) PANC1 cells were treated in triplicate with gemcitabine (10 nM) for 24 h before the addition of kinase inhibitors (all 1 µM) or UCN-01 (100 nM). Viability was assessed 48 h later using MTS assay. Assays were conducted at least 3 times and data are presented as the mean ± SD ***P < 0.00001, **P ≤ 0.0001, and *P < 0.005 compared with gemcitabine/untreated cells, respectively. (B) Clonogenic assays of PANC1 cells treated with or without gemcitabine (10 nM) for 24 h followed by a 3 h treatment with the indicated kinase inhibitors (1 µM) or UCN-01 (100 nM). All drugs were washed out and surviving colonies determined 7–10 d later. Assays were conducted in duplicate a minimum of 3 times and data are presented as the mean ± SD ***P < 0.005, **P < 0.01, and *P < 0.05. (C) PANC1 cells were treated as in (A).Following treatment, cells were harvested and apoptotic cell death determined via Annexin V staining. Experiments were conducted 3 times and data are presented as the mean ± SEM *P < 0.05, **P < 0.005, and ***P < 0.001.