The search terms “ectoprotease”, “cell surface protease”, “DPP4/CD26”, “FAP/Seprase”, “APN/CD13”, “ADAM17/TACE”, “MMP/gelatinase”, “drug”, “inhibitor”, “clinical trial”, “metabolism”, “tumour”, “microenvironment” were employed for this purpose. The gene discussed is DPP4; the disease is neoplasm.