Figure 4.

CDK2 inactivation mediates cell cycle arrest by MYC depletion and is not selectively lethal to MYC-dependent breast cancer cells. (A) Cells were transfected with either pooled MYC siRNA (siMYC) or Non-targeting siRNA control (siCON) at 2 nM or 10 nM. Cell lysates were collected at 72 hour post-transfection and then subjected to Western blotting. β-ACTIN was used as loading control for whole-cell lysates. (B) Cells were transfected with either pooled CDK2 siRNA (siCDK2) or Non-targeting siRNA control (siCON) at 10 nM. 72 hours after transfection, cell proliferation was measured by BrdU incorporation. Data are mean ± SEM analysed in triplicate experiments. (C) A panel of 17 human breast cancer cell lines were treated with CDK2 inhibitor SNS-032 at a series of concentrations for 48 hours followed by measurement of BrdU incorporation. The correlation between sensitivity to MYC siRNA and SNS-032 was assessed. Sensitivity to MYC siRNA was determined by inhibition of BrdU incorporation at 10 nM MYC siRNA and sensitivity to SNS-032 determined by the IC₅₀ value for each cell line shown in Additional file 1: Table S2 and S3, respectively. R = Pearson correlation coefficient, P = the corresponding P-value.