Abstract 540: A MALDI imaging mass spectrometry approach using tissue microarrays to identify an N-glycan biomarker panel for pancreatic cancers

Abstract

We have recently developed a MALDI imaging mass spectrometry (MALDI-IMS) method to spatially profile N-linked glycans in frozen and formalin-fixed paraffin-embedded (FFPE) tissue sections and tissue microarrays (TMAs). Tissues are incubated with peptide N-glycosidase, and released N-glycans are detected directly using MALDI-FTICR, linked directly with tissue histopathology. Other methods to detect the localization of glycans in tissues rely on detection of broader glycan structural motifs (i.e., lectins or carbohydrate antigen antibodies), whereas our method is able to simultaneously identify and distinguish 40 or more components of the N-glycome on a single slide. To demonstrate the ability of MALDI-IMS to generate biomarker panels, pancreatic cancer tissue blocks and six TMAs containing matched tumor and non-tumor regions from over 70 patients were profiled. Aberrant glycosylation, such as elevated CA-19-9, is well documented in pancreatic cancer, making this an ideal sample set. To best analyze this complex data set, we developed an in-house analysis script that can extract spectra from tissue cores, and return non-biased statistics for observed glycan ions. Panels were generated using a training set of data and tested on external validation data set. The most accurate panel of 12 glycans achieved an overall sensitivity of 92.9% and specificity of 86.7%. Structural identification of N-glycans has been confirmed by techniques such as on-tissue CID, ethylation analysis, sequential glycosidase digestions, and comparison to glycan structural databases. Furthermore, imaging of entire FFPE sections matched with histological analysis revealed a vast diversity of N-glycan localizations, which could distinguish not only tumor from normal tissue, but also regions of pancreatitis and pancreatic intraepithelial neoplasia. The generated glycan tissue maps will also be used to determine specific glycoprotein carriers of biomarker candidate glycans in tissue and biofluid samples.

Citation Format: Richard R. Drake, Thomas W. Powers, Benjamin A. Neely. A MALDI imaging mass spectrometry approach using tissue microarrays to identify an N-glycan biomarker panel for pancreatic cancers. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 540. doi:10.1158/1538-7445.AM2015-540