DPP4 and mesothelioma: We used the mesothelioma cell line ACC-MESO1 (MESO1) cells which naturally express CD26, MSTO-211H cells which do not express CD26 (MSTO-Wild), and CD26 transfectant of MSTO-211H cells (designated as MSTO-CD26 (+) cells) (Figure 1A).