Analysis of colorectal adenocarcinoma tissue by desorption electrospray ionization mass spectrometric imaging

Stefanie Gerbig, Ottmar Golf, Julia Balog, Julia Denes, Zsolt Baranyai, Attila Zarand, Erzsebet Raso, Jozsef Timar, Zoltan Takats

Research output: Contribution to journalArticle

66 Citations (Scopus)

Abstract

Negative ion desorption electrospray ionization (DESI) was used for the analysis of an ex vivo tissue sample set comprising primary colorectal adenocarcinoma samples and colorectal adenocarcinoma liver metastasis samples. Frozen sections (12 μm thick) were analyzed by means of DESI imaging mass spectrometry (IMS) with spatial resolution of 100 μm using a computer-controlled DESI imaging stage mounted on a high resolution Orbitrap mass spectrometer. DESI-IMS data were found to predominantly feature complex lipids, including phosphatidylinositols, phophatidyl-ethanolamines, phosphatidyl-serines, phosphatidyl-ethanolamine plasmalogens, phosphatidic acids, phosphatidyl-glycerols, ceramides, sphingolipids, and sulfatides among others. Molecular constituents were identified based on their exact mass and MS/MS fragmentation spectra. An identified set of molecules was found to be in good agreement with previously reported DESI imaging data. Different histological tissue types were found to yield characteristic mass spectrometric data in each individual section. Histological features were identified by comparison to hematoxylin-eosin stained neighboring sections. Ions specific to certain histological tissue types (connective tissue, smooth muscle, healthy mucosa, healthy liver parenchyma, and adenocarcinoma) were identified by semi-automated screening of data. While each section featured a number of tissuespecific species, no potential global biomarker was found in the full sample set for any of the tissue types. As an alternative approach, data were analyzed by principal component analysis (PCA) and linear discriminant analysis (LDA) which resulted in efficient separation of data points based on their histological types. A pixel-by-pixel tissue identification method was developed, featuring the PCA/LDA analysis of authentic data set, and localization of unknowns in the resulting 60D, histologically assigned LDA space. Novel approach was found to yield results which are in 95% agreement with the results of classical histology. KRAS mutation status was determined for each sample by standard molecular biology methods and a similar PCA/LDA approach was developed to assess the feasibility of the determination of this important parameter using solely DESI imaging data. Results showed that the mutant and wild-type samples fully separated. DESI-MS and molecular biology results were in agreement in 90% of the cases.

Original languageEnglish
Pages (from-to)2315-2325
Number of pages11
JournalAnalytical and Bioanalytical Chemistry
Volume403
Issue number8
DOIs
Publication statusPublished - Jun 1 2012

Keywords

  • Colorectal adenocarcinoma
  • Desorption electrospray ionization
  • KRAS mutation
  • Mass spectrometry imaging
  • Multivariate statistical analysis
  • Phospholipid profile

ASJC Scopus subject areas

  • Analytical Chemistry
  • Biochemistry

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