CDK inhibitor induced cell death is MYC dependent. (A) MYC dependency of cell death induced by CDK inhibition in RPE cells. RPE-MYC cells were first treated with either MYC siRNA or control nonspecific siRNA for 24 h, and then treated with purvalanol A for 72 h. The collected cells were analyzed for cell viability by Guava ViaCount assay and for PARP activation by Western blotting. The experiments were repeated three times in triplicate. The error bars represent means ± SEM. P-values were calculated by two-tailed Student’s t test. (B) siRNA-mediated MYC knockdown in triple-negative cells undergoing purvalanol A treatment. The experiment was independently repeated three times. The error bars represent means ± SEM. P-values were calculated by two-tailed Student’s t test. (C) Receptor-positive cell lines T47D and HCC1428, engineered to overexpress MYC and exposed for 72 h to purvalanol A treatment. The experiments were repeated three times in triplicate. The error bars represent means ± SEM. P-values were calculated by two-tailed Student’s t test.