Identification of Fucosylated Haptoglobin as a Novel Tumor Marker for Pancreatic Cancer and Its Possible Application for a Clinical Diagnostic Test

Fucosylation is one of the most important oligosaccharide modifications in cancer and inflammation. The fucosylation level is increased in total cellular proteins of cancer cells as well as in sera of patients with cancer. Recently, on AAL blot analysis, we found a fucosylated glycoprotein of 40 kDa in sera of patients with pancreatic cancer. Based on its N-terminal sequence, this protein was identified as haptoglobin. Fucosylated haptoglobin was increased in sera of patients with several kinds of cancer and the positive rate was higher in pancreatic cancer. The level of fucosylated haptoglobin was not correlated with total haptoglobin, suggesting that a factor other than inflammation could regulate the production of fucosylated haptoglobin. Mass spectrometry analysis revealed the detailed oligosaccharide structure of fucosylated haptoglobin purified from sera of patients with pancreatic cancer. For clinical applications, we developed a lectin-antibody ELISA system for quantifying fucosylated haptoglobin. In this review, we would like to summarize the history of the identification of fucosylated haptoglobin as a marker for pancreatic cancer and its possible application for a clinical diagnostic test.