Panel 4A, Cell proliferation after 24, 48, or 72 hr incubation in the presence of the indicated concentrations of radicicol (n=3). Panel 4B, Cdk6 levels after 24 hr of treatment with the indicated concentrations of radicicol. Panel 4C, Densitometry of Cdk6 levels remaining after 24 hr of treatment with the indicated concentrations of radicicol (n=3). Panel 4D, PARP cleavage after 24 treatment with the indicated concentrations of radicicol.