Figure 4. Dasatinib markedly reduces phosphotyrosine levels and pre-B cell numbers in the bone marrow.

(A) Total bone marrow cell lysates from 2 vehicle and 4 dasatinib (15 mg/kg twice daily) treated c-Cbl^A/− mice following 4 weeks of dosing were immunoblotted with the indicated antibodies. Bone marrow cells from the 6 mice were phenotyped by flow cytometry to determine (B) the percentage of lineage negative cells, (C) percentage of c-Kit⁺ Lin⁻ cells and (D) percentage of pre-B cells, i.e. B220⁺ IgM⁻ CD24⁺ CD43⁻ cells. (E) Flow cytometry profiles showing the loss of pre-B cells in the dasatinib-treated mice. (F) B6.CD45.1 mice repopulated with c-Cbl^A/− bone marrow were dosed twice daily with 15 mg/kg of dasatinib for the indicated number of days. Bone marrow cells were analyzed to determine when the loss of pre-B cell became evident, with the data showing a significant loss of pre-B cells by day 4 of dosing. The results are from 3 mice per time point and treatment, and are expressed as means ± standard errors. *P<0.05, **P<0.01, ***P<0.001 using the unpaired Student’s t test.