Figure 5.

Inhibition of CHK1 does not alter cellular sensitivity in cells with high RAD51 levels. (A) Sensitivity to hydrogen peroxide in U2OS cells with high RAD51 levels. Exponential growing cells were treated for 1 h with increasing hydrogen peroxide concentrations in the presence or absence of a 2 h pre-incubation with 100 nM UCN-O1 24 h after induction of high RAD51 expression and sensitivity was analyzed using the colony formation assay. Mean ± SEM of 3 independent experiments is shown. (B) Sensitivity to hydrogen peroxide after inhibition of CHK1 in breast cancer cell lines. Exponential growing cells were treated with 50 µM hydrogen peroxide in the presence or absence of a 2 h pre-incubation with100 nM UCN-O1 and sensitivity was monitored by colony formation. Mean ± SEM of at least 3 independent experiments is shown and statistical analysis was performed using Student's t-test.