CXCR4 and acute lymphoblastic leukemia: The “bone marrow-derived” leukemic cells, CXCR4-dependent invaders [25, 24], T lymphoid precursors clonal proliferation, and the suggested intrathymic origin of T-ALL [32, 33] prompted us to analyze whether the Notch3+CXCR4+DP thymocytes, with high capability to migrate and circulate in N3-ICtg mice, could specifically engraft and infiltrate into BM of NSG recipient mice.