DPP4 and gastrointestinal stromal tumor: CD26 expression has been characterized on various cancers such as malignant pleural mesothelioma (MPM), colorectal cancer (CRC), hepatocellular carcinoma (HCC), renal cell carcinoma (RCC), lung cancer, prostate cancer, thyroid cancer, gastrointestinal stromal tumor (GIST), thyroid cancer, and selected hematologic malignancies [20].