To understand the key soluble factors responsible for hBMSC-CM-mediated protection, we examined whether cytokines highly expressed by BMSCs such as GM-CSF, IL-3, and FGF-2 that have been shown to protect FLT3-ITD AML cells from cell killing by FLT3 inhibitors (Traer et al., 2016; Sung et al., 2019) show similar effects to hBMSC-CM. This evidence concerns the gene FGF2 and acute myeloid leukemia.