Interaction of SDF-1/CXCR4 was assayed in human leukemia CCRF-CEM cells expressing high levels of human CXCR4, MDA-MB-435 cells stably transfected with monkey CXCR4, and mouse 2PK-3 lymphoma cells expressing high levels of mouse CXCR4. The gene discussed is CXCL12; the disease is leukemia.