PSCA and cancer: Prostate stem cell antigen (PSCA) is a glycosylphosphatidylinositol (GPI)-anchored cell surface protein associated with various cancer types such as prostate, bladder, gastric and pancreatic cancer, that has been proposed as a biomarker for detection of circulating tumour cells (CTCs) and for cytological examination of specimens in pancreatic cancer patients [136,137].