SDF-1 (CXCL12) in haematopoiesis and leukaemia: impact of DPP IV/CD26.

DPP IV/CD26 contributes to cell signalling by various mechanisms: as a receptor or co-receptor, as a component of a membrane-associated signal transduction complex and by virtue of its exopeptidase activity. The presence of enzymatically active DPP IV in a variety of tissues and in plasma makes it challenging to review clinical consequences of chemokine turnover by DPP IV activity, even more so in times when the concept of DPP IV inhibition for therapeutic purposes has reached the stage of clinical application. Among the known substrates of DPP IV/CD26, Stromal cell-derived factor 1 (SDF-1, CXCL12) has gained attention in recent years as a critical mediator of chemotaxis and tissue invasion, especially in the context of malignant disease. SDF-1 and its receptor, CXCR4, differ from other chemokines and their respective receptors by a lack of redundancy and pleiotropism. Therapeutic intervention using CXCR4 antagonists has been proposed. It seems appropriate to review the role of SDF-1 in haematopoiesis and its malignant counterpart, leukaemia, and to assess the interference of DPP IV/CD26 with the SDF-1/CXCR4 axis as well as possible risks and benefits of DPP IV inhibition.