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Stem Cells International
Volume 2016, Article ID 6809105, 17 pages
http://dx.doi.org/10.1155/2016/6809105
Review Article

Glioblastoma Stem Cells Microenvironment: The Paracrine Roles of the Niche in Drug and Radioresistance

1Department of Life, Health and Environmental Sciences, University of L’Aquila, 67100 L’Aquila, Italy
2Sbarro Institute for Cancer Research and Molecular Medicine, Temple University, Philadelphia, PA 19122, USA
3Department of Medicine, Surgery and Neuroscience, University of Siena, 53011 Siena, Italy
4National Institute for Nuclear Physics (INFN), Gran Sasso National Laboratory (LNGS), Assergi, 67100 L’Aquila, Italy

Received 19 August 2015; Revised 9 November 2015; Accepted 10 November 2015

Academic Editor: Ilya V. Ulasov

Copyright © 2016 Alessia Fidoamore et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Among all solid tumors, the high-grade glioma appears to be the most vascularized one. In fact, “microvascular hyperplasia” is a hallmark of GBM. An altered vascular network determines irregular blood flow, so that tumor cells spread rapidly beyond the diffusion distance of oxygen in the tissue, with the consequent formation of hypoxic or anoxic areas, where the bulk of glioblastoma stem cells (GSCs) reside. The response to this event is the induction of angiogenesis, a process mediated by hypoxia inducible factors. However, this new capillary network is not efficient in maintaining a proper oxygen supply to the tumor mass, thereby causing an oxygen gradient within the neoplastic zone. This microenvironment helps GSCs to remain in a “quiescent” state preserving their potential to proliferate and differentiate, thus protecting them by the effects of chemo- and radiotherapy. Recent evidences suggest that responses of glioblastoma to standard therapies are determined by the microenvironment of the niche, where the GSCs reside, allowing a variety of mechanisms that contribute to the chemo- and radioresistance, by preserving GSCs. It is, therefore, crucial to investigate the components/factors of the niche in order to formulate new adjuvant therapies rendering more efficiently the gold standard therapies for this neoplasm.