Glioblastoma‐associated stromal cells (GASCs) from histologically normal surgical margins have a myofibroblast phenotype and angiogenic properties

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Abstract
Glioblastoma (GB) displays diffusely infiltrative growth patterns. Dispersive cells escape surgical resection and contribute to tumour recurrence within a few centimeters of the resection cavity in 90% of cases. We know that the non‐neoplastic stromal compartment, in addition to infiltrative tumour cells, plays an active role in tumour recurrence. We isolated a new stromal cell population from the histologically normal surgical margins of GB by computer‐guided stereotaxic biopsies and primary culture. These GB‐associated stromal cells (GASCs) share phenotypic and functional properties with the cancer‐associated fibroblasts (CAFs) described in the stroma of carcinomas. In particular, GASCs have tumour‐promoting effects on glioma cells in vitro and in vivo. Here, we describe a quantitative proteomic analysis, using iTRAQ labelling and mass spectrometry, to compare GASCs with control stromal cells derived from non‐GB peripheral brain tissues. A total of 1077 proteins were quantified and 67 proteins were found to differ between GASCs and control stromal cells. Several proteins changed in GASCs are related to a highly motile myofibroblast phenotype, and to wound healing and angiogenesis. The results for several selected proteins were validated by western blotting or flow cytometry. Furthermore, the effect of GASCs on angiogenesis was confirmed using the orthotopic U87MG glioma model. In conclusion, GASCs, isolated from GB histologically normal surgical margins and found mostly near blood vessels, could be a vascular niche constituent establishing a permissive environment, facilitating angiogenesis and possibly colonization of recurrence‐initiating cells. We identify various proteins as being expressed in GASCs: some of these proteins may serve as prognostic factors for GB and/or targets for anti‐glioma treatment. Copyright © 2014 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd

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