PROK1 and pancreatic ductal adenocarcinoma: Recently, its association with malignant tumors has been studied, and the following findings have been obtained: 1) increased PROK1 expression is associated with increased malignancy of prostate cancer, neuroblastoma, thyroid cancer and pancreatic duct cancer [25–28]; 2) PROK1 mRNA expression in the resected primary lesion of colorectal cancer patients is associated with a significantly worse prognosis, compared with those patients who did not express PROK1 [29–32]; and 3) increased PROK1 expression is associated with angiogenesis involving hepatic metastasis [33].