Confocal imaging of RAD51 foci. A. MDA-MB-231 cells were cultured on coverslips with 10 nmol/L gemcitabine for 0 – 24 h then stained for RAD51 foci. 100 cells were scored for each condition. Values reflect the mean and range of 2 independent experiments. B. Cells were untreated or incubated with either 1 μmol/L MK-8776 for 6 h, 10 nmol/L gemcitabine for 24 h, or 10 nmol/L gemcitabine 0–24 h with 1 μmol/L MK-8776 added for the last 6 h. Cells were scored as in A. Significance was calculated using an unpaired t-test.