The sialyl Lewis A (sLeA) glycan forms the basis of the CA19-9 blood test and is the current biomarker for pancreatic ductal adenocarcinoma (PDAC). However, it is not elevated in approximately 25% of PDAC patients and it also has difficulties in diagnosing early-stage PDAC. My overarching goal was focusing on improving precision of overall PDAC diagnostics. I hypothesized that other glycans within the Lewis blood group family besides sLeA are aberrantly increased in the subpopulation of PDAC patients who do not secret sLeA into their blood. To test the hypothesis, two specific approaches were implemented in this study: 1) Profile an isomer of sLeA, named sialyl-Lewis X (sLeX), and glycans with fucosylated motifs in the plasma of sLeA-low PDAC patients using antibody and lectin microarray method; and 2) Test the sulfated and sialylated glycans derived from type 2 N-acetyl-lactosamine precursor in subpopulations of PDACs using a novel on-chip analysis method.In the first approach, I profiled the levels of multiple glycans and glycosylated mucins in plasma from two cohorts of 200 and 116 test subjects with PDACs and non-malignant disease patients. From these screens, I found significant increases in two categories of glycans: sialyl Lewis X variants, presented both in sulfated and non-sulfated forms, and the sialylated type 1 N-acetyl-lactosamine. These glycans are increased in distinct groups of PDAC patients and contribute to the improved accuracy of a biomarker panel.Thus, I concluded that detecting other glycans within the Lewis blood-group besides sLeA has the potential to improve diagnoses of PDAC patients.To further elucidate the structural nuances of sialyl Lewis X variants from initial screen, I developed a new assay called On-chip Glycan Modification and Probing and a complementary computational algorithm to accurately analyze novel sulfated and sialylated glycans from plasma of pancreatic cancer patients. In detailed structural information, I observed strong evidences of sulfated and sialylated type 2 N-acetyl-lactosamine glycans overexpressed in plasma of PDAC patients and pancreatic cancer cell lines, but not in the plasma of healthy people. In addition, the sulfated and sialylated type 2 N-acetyl-lactosamine glycans presented on a specific mucin, MUC5AC, was statistically associated (p < 0.001) with short time-to-progression of PDAC patients, but CA19-9 test was not. I concluded sulfated and sialylated type 2 N-acetyl-lactosamine glycans presented on MUC5AC were new serological biomarkers that could improve precision of current practices for diagnosis and prognosis of PDACs patients.
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