The equilibrium between proliferation and differentiation of the hematopoietic stem cells (HSC) is controlled by endosteal region, a site of HSC niche, maintained mainly by the attractive chemokine (CXCL12) and by a central region, responsible for generation of different hematopoietic progenitor cells [36] Based on these characteristics, the bone marrow microenvironment is a fertile soil not only for HSC and its progenies, but also or the growth of cancer cells. The gene discussed is CXCL12; the disease is cancer.