PRNP and colorectal cancer: The expression of PRNP is positively associated with tumor development, drug resistance and poor prognosis in colorectal cancer [6,7], pancreatic carcinoma [8,9,10], breast cancer [11,12], hepatocellular carcinoma [13], esophageal squamous cell carcinoma [14], glioma [15] and lung cancer [16,17].