DPP4 and non-small cell lung carcinoma: Our results showed abundant CD26 expression in highly invasive NSCLC cell lines (A549, H1975, and CL1–5), but low CD26 expression in the poorly invasive CL1–0 cell line and found a significant correlation between CD26 protein levels and the invasive abilities of a set of NSCLC cell lines (A549, CL1–0, CL1–3, CL1–5, HCC827, PC9, and H1975).