CXCR4 and B-cell chronic lymphocytic leukemia: About the set of cytokines secreted by both stromal fibroblasts and the co-culture, as expected, it was detected CXCL12 (SDF-1: Stromal Derived Factor-1), a chemokine that promotes cell survival by binding its specific receptor CXCR4, particularly present and highly expressed in CLL and other of blood malignancies.