For instance, AML M4 and M5 (acute myelomonocytic leukemia and acute monocytic leukemia) tend to show elevated SDF-1 levels, potentially due to their higher percentage of monocytic cells, which are known to express high levels of CXCR4 and are particularly responsive to SDF-1 signaling (15). The gene discussed is CXCR4; the disease is acute myeloid leukemia.