DPP4 and mesothelioma: The murine CD26 mAbs, 1F7 and 14D10, which recognize the cell membrane-proximal glycosylated region starting with a 20-amino acid flexible stalk region of human CD26, are reported to have anti-tumor effects against T cell leukemia/lymphoma, mesothelioma and renal carcinoma cells, both in vitro and in vivo [4-6].