MALDI imaging in histopathology

Abstract

Introduction MALDI imaging is a new technique that allows the investigation of the molecular signatures directly on tissue sections. The technology allows for the quantification of pep-tides/proteins and their spatial distributed on these tissues. The technology has tremendous potential for the discovery of new biomarkers in cancer. The primary aim of this investigation was to interrogate the use of MALDI-TOF to determine the level and extent of peptide/protein profiles on FFPE histo-pathology tissue. Materials and methods Gastric cancer cases were obtained from the archives of the Division of Anatomical Pathology, University of Cape Town/National Health Laboratory Services. Formalin fixed paraffin embedded (FFPE) tissues was sectioned at 6u and picked up on ITO slides. The tissues were then antigen retrieved before MALDI preparation. The corresponding H&E sections were also scanned before image preparation. The tissue was coated with trypsin followed by the addition of the matrix coating. This step was done on the Braker Imageprep Instrument. The slides were then analysed in the Bruker Autoflex 111 instrument. The spectra were captured automatically and this was followed by analysis using the Fleximaging software. Results The peaks from the spectra generated were assigned different colours which could be imaged directly on the tissue section. We were successful in identifying specific peptide which was overexpressed in certain areas of the tissue. Conclusion We have shown that FFPE tissue can be used for MALDI imaging. This method is suitable for the identification and distribution of new biomarkers in association with the histological phenotype.