Identification of proteomic markers in head and neck cancer using MALDI-MS Imaging, LC-MS/MS and Immunohistochemistry.

PURPOSE: The heterogeneity of squamous cell carcinoma tissue greatly complicates diagnosis and individualized therapy. Therefore, characterizing the heterogeneity of tissue spatially and identifying appropriate biomarkers is crucial. MALDI imaging (MSI) is capable of analyzing spatially resolved tissue biopsies on a molecular level.

EXPERIMENTAL DESIGN: We used MALDI MSI on snap frozen and formalin-fixed and paraffin-embedded (FFPE) tissue samples from patients with head and neck cancer (HNC) to analyze m/z values localized in tumor and non-tumor regions. Peptide identification was performed using LC-MS/MS and immunohistochemistry (IHC).

RESULTS: In both FFPE and frozen tissue specimens, we found eight characteristic masses of the tumor's epithelial region. Using LC-MS/MS, the peaks were identified as vimentin, keratin type II, nucleolin, heat shock protein 90, prelamin-A/C, junction plakoglobin and PGAM1. Lastly, vimentin, nucleolin and PGAM1 were verified with IHC.

CONCLUSIONS AND CLINICAL RELEVANCE: The combination of MALDI MSI, LC-MS/MS and subsequent IHC furnishes a tool suitable for characterizing the molecular heterogeneity of tissue. It is also suited for use in identifying new representative biomarkers to enable a more individualized therapy. This article is protected by copyright. All rights reserved.