BCL2 and leukemia: In childhood B cell precursor acute lymphoblastic leukemia, increased Helios expression in Tregs facilitates the infiltration and metastasis of leukemia stem cells by elevating Vascular endothelial growth factor A (VEGFA) expression and Vascular endothelial growth factor receptor 2 (VEGFR2) activity and modulates leukemia cell apoptosis by promoting the expression of the antiapoptosis protein Bcl-2 [36].