In Situ Proteomic Analysis of Glioblastoma Multiforme: A Translational Approach to Improve Prognostic/Diagnostic Routines

In order to evaluate the use of matrix-assisted laser desorption ionization (MALDI) Mass Spectral Imaging (MSI) to Glioblastoma (GBM) studies, some sections of formalin fixed paraffin embedded samples of GBM tumors were submitted to classical immunoassays, to define the profile of distribution of some classical and well recognized molecular markers of GBM grade IV (Ki-67, S100, Glial GFAP, CD31 and CD34), while other sections of the same samples were submitted to in-tissueproteomic analysis by MALDI MSI, and both results compared to each other. The overlapping of the MALDI spectra obtained for the tryptic peptides with the immunohistochemical reactions of each marker protein were used to build a distribution map of the marker proteins all over the GBM tissue section. The results revealed a high correlation between both methods, indicating that MALDI MSI has enough sensitivity to be compared to the immunohistochemical methods, as well is sufficiently reliable to be used in biomarkers identification.