Considering the interaction of DPPIV/CD26 with extracellular matrix components and through regulation of E-cadherin, matrix metalloproteinases (MMPs), and tissue inhibitors of matrix metalloproteinases (TIMPs), it remains to be more clearly established whether tumor progression is more affected by the ectopeptidase activity or non-proteolytic mechanisms. The gene discussed is FAP; the disease is neoplasm.