FLT3 and acute myeloid leukemia: Treatment with 2 ng/mL rhTGF-β1, equivalent to the levels of TGF-β produced by osteoblastic cell lines [37], reduced apoptosis induction by Ara-C in both FLT3/ITD mutant MV4;11 and in wt-FLT3 U937 and THP-1 AML cells (Figure 1A).