Gastric carcinoma remains among the top-5 leading cancers in incidence and mortality in Portugal as well as in several other European and non-European countries. The poor prognosis and high mortality of gastric carcinoma reflects the late diagnosis due to appearance of clinical symptoms only when the cancer has progressed. Early detection accomplished through an efficient screening program remains the most promising approach to improve the long-term survival of cancer patients. This project aims to identify and evaluate novel diagnostic biomarkers, useful for early detection of gastric carcinoma, based on distinct cancer-associated changes in one of the most abundant post-translational modification of proteins, O-glycosylation (O-PTM). Carcinomas express O-glycosylated glycoproteins characterized by the synthesis of truncated O-glycans. These novel epitopes distinguish the cancer glycoproteins from the normal counterparts and are considered a hallmark of glycosylation in carcinomas. Glycoproteins bearing truncated O-PTM can be shed into serum representing potential biomarkers. This project will use a combination of glycoproteomics, chemoenzymatic synthesis of glycopeptides, development of novel monoclonal antibodies, and ELISA-based assays for screening of human sera to identify biomarkers in gastric carcinoma. The specific aims of the project are: 1 The identification of glycoproteins carrying cancer-associated O-glycan haptens, Tn (GalNAcalpha1-OSer/Thr), STn (NeuAcalpha2-3GalNAcalpha1-O-Ser/Thr), and T (Galbeta1-3GalNAcalpha1-O-Ser/Thr) in serum of gastric carcinoma patients using state-of-the-art glycoproteomic approaches;
2 Chemoenzymatic synthesis, using recombinant glycosyltransferases, of Tn, STn and T glycopeptides/glycoproteins identified within the first aim and also of known glycoproteins (mucins) expressed with altered glycosylation in gastric carcinoma;
3 Production of monoclonal antibodies against O-PTM glycopeptides specifically directed to epitopes expressed in gastric carcinoma and development of an ELISA assay.
4 Serological detection of O-PTM biomarkers expressed in gastric carcinoma patients and identification of the biomarkers for early detection gastric carcinoma. The major goal of this project is to develop a serological assay to detect novel gastric carcinoma biomarkers for early detection of gastric carcinoma.