HSC-regulating genes (BMP4, ANGPT1, and VCAM1) (25–27) were strongly down-regulated in BMSCs (BMP4, p<0.0001; ANGPT1, p<0.0001; VCAM1, p<0.0001) and in their pre-osteoblast progeny (BMP4, p=0.0005; ANGPT1, p<0.0001; VCAM1, p=0.0004) after exposure to HL-60 AML cells (Figure 3A). Here, BMP4 is linked to acute myeloid leukemia.