A review of the development of tumor vasculature and its effects on the tumor microenvironment
Received 25 January 2017
Accepted for publication 21 March 2017
Published 11 April 2017 Volume 2017:5 Pages 21—32
Checked for plagiarism Yes
Review by Single-blind
Peer reviewer comments 2
Editor who approved publication: Prof. Dr. Dörthe Katschinski
Jake C Forster,1,2 Wendy M Harriss-Phillips,1,2 Michael JJ Douglass,1,2 Eva Bezak1,3
1Department of Physics, University of Adelaide, 2Department of Medical Physics, Royal Adelaide Hospital, 3Sansom Institute for Health Research and the School of Health Sciences, University of South Australia, Adelaide, SA, Australia
Background: The imbalance of angiogenic regulators in tumors drives tumor angiogenesis and causes the vasculature to develop much differently in tumors than in normal tissue. There are several cancer therapy techniques currently being used and developed that target the tumor vasculature for the treatment of solid tumors. This article reviews the aspects of the tumor vasculature that are relevant to most cancer therapies but particularly to vascular targeting techniques.
Materials and methods: We conducted a review of identified experiments in which tumors were transplanted into animals to study the development of the tumor vasculature with tumor growth. Quantitative vasculature morphology data for spontaneous human head and neck cancers are reviewed. Parameters assessed include the highest microvascular density (h-MVD) and the relative vascular volume (RVV). The effects of the vasculature on the tumor microenvironment are discussed, including the distributions of hypoxia and proliferation.
Results: Data for the h-MVD and RVV in head and neck cancers are highly varied, partly due to methodological differences. However, it is clear that the cancers are typically more vascularized than the corresponding normal tissue. The commonly observed chronic hypoxia and acute hypoxia in these tumors are due to high intratumor heterogeneity in MVD and lower than normal blood oxygenation levels through the abnormally developed tumor vasculature. Hypoxic regions are associated with decreased cell proliferation.
Conclusion: The morphology of the vasculature strongly influences the tumor microenvironment, with important implications for tumor response to medical intervention such as radiotherapy. Quantitative vasculature morphology data herein may be used to inform computational models that simulate the spatial tumor vasculature. Such models may play an important role in exploring and optimizing vascular targeting cancer therapies.
Keywords: cancer, head and neck, vasculature morphology, hypoxia, radiotherapy response
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