Indirectly, AML cells — by altering BM niche components (30, 66) via exosomes (45, 46, 67) or TGF-β1 release (30, 31, 43) and/or by modifying the metabolic milieu (28, 68) — affect HSC proliferation and/or mobilization out of the niche. This evidence concerns the gene TGFB1 and acute myeloid leukemia.