MYC and acute myeloid leukemia: Moreover, SDF1-mediated CXCR4 activation induces resistance to chemotherapy drug Cytarabine, by downregulating microRNA let-7a and promoting transcriptional activation of Myc and BCL2-like 1 isoform 1 (BCL-xL) in acute myeloid leukemia (AML) cells [55].