CXCR4 and acute myeloid leukemia: Exosomes carry factors like Fas Ligand (FAS-L), NPM1, FLT3, Matrix Metallopeptidase 9 (MMP9), insulin-like growth factor type 1 receptor (IGF1-R), CXCR4, and chaperones to alter the BM microenvironment, improve leukemic cell survival, and extrinsically mediate drug resistance in primarily sensitive AML [165,167,168].