FLT3 and acute myeloid leukemia: Strikingly, in a murine AML cell line model of 32D cells that were retrovirally transduced with a FLT3-ITD overexpressing vector, mRNA levels of MTSS1 were significantly downregulated 30-fold, suggesting that MTSS1 is negatively regulated by FLT3-ITD signaling (Fig 5A).