Rb deficiency reduces TGFβ inhibition of proliferation. The figure shows the percentage of cells in S phase at the indicated times after plating of one representative experiment. All hepatocytes for the experiment were isolated from the same Rb-floxed mouse. Control and Rb-/- cells are Rb-floxed cells treated at the time of plating with either adenovirus control (wild-type phenotype) (A); or adenovirus expressing Cre (Rb-/-) (B) respectively. Each point is the average proliferation in 2 independent cultures where 500 hepatocytes were counted +/- SEM. The experiment was repeated multiple times with similar results. Where appropriate (close symbols), TGFβ was added daily from 24 hours after plating.