Amongst its substrates that are key cell mediators are the cell-directing peptides known as chemokines, and the highest affinity of DPP4 is for CXCL12 (stromal-derived factor-1, SDF-1), which is the ligand for the receptor CXCR4, a regulator of cell migration that is itself regulated by constituents of the tumour microenvironment (Richard et al., 2006; Richard et al., 2007; Richard and Blay 2008). The gene discussed is DPP4; the disease is neoplasm.