GPA33 and cancer: Of the tissue-specific proteins which have not been previously studied as serum cancer or benign disease biomarkers, colon-specific protein GPA33, pancreas-specific proteins chymotrypsinogen B1 and B2, chymotrypsin C, CUB and zona pellucida-like domains 1, KLK1, PNLIP-related protein 1 and 2, regenerating islet-derived 1 beta and 3 gamma and prostate-specific protein NPY represent such candidates.