Effects of PP2 on proliferation. BaF3 cell lines expressing wild-type Mpl, T69, T111, and Y112F were grown in the presence of added TPO plus the indicated concentrations of Src kinase inhibitor (PP2). Proliferation was measured in triplicate wells by MTS assay in 96-well plates. Results of MTS proliferation assays are expressed as the mean values of 4 separate experiments. To account for differences in cell number between cell lines, the data have been normalized as a percentage of maximal proliferation induced by IL-3. Error bars indicate SD.