Carbohydrate 3′-sialyllactose as a novel target for theranostics in pancreatic ductal adenocarcinoma

We previously demonstrated that the carbohydrate 3′-sialyllactose is overexpressed in cancer stem-like cells such as metastatic pancreatic and poorly differentiated gastric cancer cells, and undifferentiated human embryonic stem cells. In this study, we investigated the possibility of 3′-sialyllactose as a target for theranostics in cancers using a recombinant mouse monoclonal antibody r3B1E2 that binds to 3′-sialyllactose. Immunohistochemistry analysis confirmed an elevated expression of 3′-sialyllactose in tumors of pancreas, stomach, and testis, while no expression of 3′-sialyllactose was observed in corresponding normal controls. In addition, a stage-independent expression of 3′-sialyllactose was observed, especially in pancreatic ductal adenocarcinoma (PDAC). The level of serum 3′-sialyllactose in PDAC subjects was significantly higher than that in healthy controls, providing excellent AUC of 0.88. We next explored the therapeutic potential of r3B1E2 for PDAC in vitro. Treatment of r3B1E2 with 3′-sialyllactose-bearing human PDAC cells exhibited a complement-dependent cytotoxicity, whereas no significant activity of r3B1E2 against 3′-sialyllactose-negative cells was observed. Collectively, these findings raise the possibility of 3′-sialyllactose as a novel target for theranostics in PDAC.