We also see a reduction in the total RB level, as has been observed previously with CDK4/6 knockdown in neuroblastoma cell lines.44 Consistently, 5 days of PB treatment resulted in a significant decrease in proliferation, compared with the vehicle control, as shown by EdU incorporation and crystal violet staining (Figures 1B–1G). The gene discussed is CDK4; the disease is neuroblastoma.