TGFB1 and acute lymphoblastic leukemia: Using intracytoplasmic flow cytometry analysis of SMAD2/3 protein phosphorylation in different BCP-ALL cell lines, we found heterogeneous phosphorylated SMAD2/3 levels at the basal state following dose-dependent stimulation with TGF-β1 as well as following inhibition by dasatinib, which varied from partial to lacking responsiveness (Figure 3a,b).