The oncosuppressor activity associated with AML let-7 miRNAs depends on their capability to target oncogenes as c-Myc, Ras, BCLXL, HMGA, JAK, STAT3 and NIRF, regulating cell proliferation, apoptosis and motility (Figure 1); among the let-7 miRNAs dysregulated in AML, let-7b and let-7i have been reported to exert possible oncogenic roles in certain types of lymphomas [24]. Here, STAT3 is linked to acute myeloid leukemia.