Interestingly, treatment with recombinant TGF-β1 increased the percentage of ALDH+ cells from 30% ± 5% to 90% ± 3% and from 10% ± 4% to 25% ± 3% in OCI-AML3 and HL60 cells, respectively, suggesting that TGF-β1 directly regulates ALDH activity in AML cells (Fig 4A and 4B). Here, TGFB1 is linked to acute myeloid leukemia.