title: iTRAQ-based proteomics profiling reveals increased metabolic activity and cellular cross-talk in angiogenic compared with invasive glioblastoma phenotype.
abstract: Malignant gliomas (glioblastoma multiforme) have a poor prognosis with an average patient survival under current treatment regimens ranging between 12 and 14 months. The tumors are characterized by rapid cell growth, extensive neovascularization, and diffuse cellular infiltration of normal brain structures. We have developed a human glioblastoma xenograft model in nude rats that is characterized by a highly infiltrative non-angiogenic phenotype. Upon serial transplantation this phenotype will develop into a highly angiogenic tumor. Thus, we have developed an animal model where we are able to establish two characteristic tumor phenotypes that define human glioblastoma (i.e. diffuse infiltration and high neovascularization). Here we aimed at identifying potential biomarkers expressed by the non-angiogenic and the angiogenic phenotypes and elucidating the molecular pathways involved in the switch from invasive to angiogenic growth. Focusing on membrane-associated proteins, we profiled protein expression during the progression from an invasive to an angiogenic phenotype by analyzing serially transplanted glioma xenografts in rats. Applying isobaric peptide tagging chemistry (iTRAQ) combined with two-dimensional LC and MALDI-TOF/TOF mass spectrometry, we were able to identify several thousand proteins in membrane-enriched fractions of which 1460 were extracted as quantifiable proteins (isoform- and species-specific and present in more than one sample). Known and novel candidate proteins were identified that characterize the switch from a non-angiogenic to a highly angiogenic phenotype. The robustness of the data was corroborated by extensive bioinformatics analysis and by validation of selected proteins on tissue microarrays from xenograft and clinical gliomas. The data point to enhanced intercellular cross-talk and metabolic activity adopted by tumor cells in the angiogenic compared with the non-angiogenic phenotype. In conclusion, we describe molecular profiles that reflect the change from an invasive to an angiogenic brain tumor phenotype. The identified proteins could be further exploited as biomarkers or therapeutic targets for malignant gliomas.
authors.affiliation: Norlux Neuro-Oncology Laboratory, Department of Oncology, Centre de Recherche Public Santé (CRP-Santé), 84 Val Fleuri, L-1526 Luxembourg, Luxembourg.
authors.forename: Uros
authors.initials: U
authors.lastname: Rajcevic
authors.forename: Kjell
authors.initials: K
authors.lastname: Petersen
authors.forename: Jaco C
authors.initials: JC
authors.lastname: Knol
authors.forename: Maarten
authors.initials: M
authors.lastname: Loos
authors.forename: Sébastien
authors.initials: S
authors.lastname: Bougnaud
authors.forename: Oleg
authors.initials: O
authors.lastname: Klychnikov
authors.forename: Ka Wan
authors.initials: KW
authors.lastname: Li
authors.forename: Thang V
authors.initials: TV
authors.lastname: Pham
authors.forename: Jian
authors.initials: J
authors.lastname: Wang
authors.forename: Hrvoje
authors.initials: H
authors.lastname: Miletic
authors.forename: Zhao
authors.initials: Z
authors.lastname: Peng
authors.forename: Rolf
authors.initials: R
authors.lastname: Bjerkvig
authors.forename: Connie R
authors.initials: CR
authors.lastname: Jimenez
authors.forename: Simone P
authors.initials: SP
authors.lastname: Niclou
mesh_terms: D000369:Aged, 80 and over; D000818:Animals; D001706:Biopsy; D001932:Brain Neoplasms / Q000378:metabolism / Q000473:pathology*; D002853:Chromatography, Liquid / Q000379:methods; D005260:Female; D005909:Glioblastoma / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D009368:Neoplasm Transplantation; D009389:Neovascularization, Pathologic; D020411:Oligonucleotide Array Sequence Analysis; D040901:Proteomics / Q000379:methods*; D051381:Rats; D011923:Rats, Nude; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
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