Molecular Biomarkers & Diagnosis

Identification of Core Proteins Carrying the Sialyl Lewis a Epitope in Pancreatic Cancers

Abstract

Yoshitoshi Hirao, Satoshi Ogasawara, Akira Togayachi, Yu-ki Matsuno, Makoto Ocho, Keishi Yamashita, Masahiko Watanabe, Shoji Nakamori, Yuzuru Ikehara and Hisashi Narimatsu

Identification of core proteins carrying the CA19-9 (carbohydrate antigen, sialyl Lewis a) epitope from various tissues will improve the diagnosis of pancreatic cancer in terms of specificity and sensitivity. In this study, we attempted to identify sialyl Lewis a-carrier proteins specifically expressed in pancreatic cancer. Pancreatic cancer is difficult to detect in the early stages of the disease, resulting in a high level of mortality. Therefore, in order to determine the correct course of treatment, it is vital to distinguish cancer from obstruction of the bile duct or other diseases. Our strategy to identify the carrier proteins was as follows: glycoproteins carrying sialyl Lewis a antigen were enriched from pancreatic cancer cell lines using anti-sialyl Lewis a antibody and then subjected to Peptide Mass Fingerprinting analysis. Based on these studies we identified nine glycoproteins carrying the sialyl Lewis a epitope. We evaluated candidate molecules by biochemical analyses of culture supernatants and human sera. In particular, we focused on one candidate molecule carrying a sialyl Lewis a epitope, Galectin-3BP/MAC2BP; M2BP, which was analyzed in detail. These results verified that our candidate molecule is a core protein carrying the sialyl Lewis a epitope. Furthermore, we demonstrated sandwich ELISA, which showed that the glycoprotein was able to detect CA19-9 antigen in culture supernatants. Our approach facilitated the identification of the core protein carrying the sialyl Lewis a epitope. We believe our approach will enable future developments in cancer glycobiomarker identification.