Abstract
Tumor growth is frequently limited by oxygen supply. Tumor cells may be chronically hypoxic if they are too far away from blood vessels, or transiently hypoxic if a blood vessel is temporarily blocked. Tumors secrete angiogenesis factors, such as VEGF, to increase their blood supply. Hypoxic tumor cells are resistant to radiation. Tumor hypoxia may be measured with various invasive and non-invasive methods. During fractionated irradiation, reoxygenation decreases radioresistance. The classic hypoxia signaling pathway is mediated by HIF-1. Tumor hypoxia may predispose cells to genomic instability, invasion, and metastasis.
Tumor stem cells are a small percentage of the tumor that accounts for most of its clonogenic activity and resistance to therapy. If a course of therapy does not eradicate the tumor stem cells, the tumor will recur.
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© 2014 Springer Science+Business Media New York
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Chang, D.S., Lasley, F.D., Das, I.J., Mendonca, M.S., Dynlacht, J.R. (2014). Tumor Microenvironment. In: Basic Radiotherapy Physics and Biology. Springer, Cham. https://doi.org/10.1007/978-3-319-06841-1_23
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DOI: https://doi.org/10.1007/978-3-319-06841-1_23
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