Validation of CHK1 as a sensitizing target to gemcitabine in pancreatic cancer cells. MIA PaCa-2 and BxPC3 pancreatic cancer cells were transfected with either CHK1, CHK2 or non-silencing siRNA. After 24 hours, cells were treated with varying concentrations of gemcitabine and incubated for an additional 72 hours. Cell number was assessed and data was normalized to siRNA plus vehicle control and plotted. Silencing of CHK1 showed potentiation of gemcitabine response in (A) MIA PaCa-2 and (C) BxPC3 cells as seen by the shift in the dose response curves. Silencing of CHK2 did not affect the response to gemcitabine in either (B) MIA PaCa-2 cells or (D) BxPC3 cells. Data is representative of three independent experiments.