Determining the Protein Profile of Prostate Cancer Samples Harboring the ERG Rearrangement Using MALDI Imaging Mass Spectrometry.
Roopika Menon, Kristina Schwamborn, Pavel Nikolov, Martin Braun, Richard M Caprioli, Sven Perner. Institute of Pathology, University Hospital Bonn, Germany; Mass Spectrometry Research Center, Vanderbilt University Medical Center, Nashville
Background: The ERG gene rearrangement is seen in a majority of patients suffering from prostate cancer (PCa). This gene fusion has been characterized at the genomic level, but much is yet to be done at the protein level. The aim of our study was to molecularly determine a protein profile specific to PCa samples harboring the ERG rearrangement, using MALDI imaging mass spectrometry.
Design: We characterized 94 fresh frozen PCa samples, from a consecutive prostatectomy series, for ERG rearrangement status by fluorescence in-situ hybridization (FISH). 68 samples were positive and 26 samples were negative for the ERG rearrangement status. The samples were further processed for MALDI imaging as follows: Fresh frozen prostate sections (12 µm) were thawed and mounted onto conductive glass slides and fixed in graded ethanol washes. Matrix application was achieved by spotting sinapinic acid onto the tissue in an array pattern using an acoustic reagent multispotter (Portrait 630, Labcyte). Samples were analyzed utilizing an Autoflex speed MALDI-TOF mass spectrometer (Bruker). Data analysis was performed by using the ClinProTools 2.2 and FlexImaging 2.1 software (Bruker).
Results: The analyzed PCa tissue revealed on average 156 peptides and proteins in the mass range from m/z 2,000-20,000. Distinctive differences in peak patterns could be identified between ERG rearranged and non-rearranged samples. Combining five peaks in a genetic algorithm based model resulted in an overall sensitivity of 91.2% and a specificity of 73.1% using the ClinProTools 2.2 and FlexImaging 2.1 software. For example, two proteins (m/z 9076 and 9750) had significantly higher expression in samples with ERG rearrangement.
Conclusions: This is the first study investigating the protein profile specific for the ERG rearrangement in PCa. Identifying the differentially expressed proteins and validation using western blot and IHC, will provide further insight into the downstream protein signaling of the ERG rearrangement dependent PCa.
Monday, February 28, 2011 8:45 AM
Platform Session: Section G 1, Monday Morning