Furthermore, hypoxia can also upregulate C-X-C chemokine receptor type 4 (CXCR4) expression in AML cells, the cognate receptor of chemokine ligand 12 (CXCL12), and promote CXCL12 expression in BMSCs via HIF-1α [45, 46]. Here, CXCL12 is linked to acute myeloid leukemia.