Biomedical Sciences Research Institute, University of Ulster, Coleraine, Northern Ireland, UK.
Br J Radiol. 2014 Mar;87(1035):20130676. doi: 10.1259/bjr.20130676.
Tumour hypoxia is increasingly recognized as a major deleterious factor in cancer therapies, as it compromises treatment and drives malignant progression. This review seeks to clarify the oxygen levels that are pertinent to this issue. It is argued that normoxia (20% oxygen) is an extremely poor comparator for "physoxia", i.e. the much lower levels of oxygen universally found in normal tissues, which averages about 5% oxygen, and ranges from about 3% to 7.4%. Importantly, it should be recognized that the median oxygenation in untreated tumours is significantly much lower, falling between approximately 0.3% and 4.2% oxygen, with most tumours exhibiting median oxygen levels <2%. This is partially dependent on the tissue of origin, and it is notable that many prostate and pancreatic tumours are profoundly hypoxic. In addition, therapy can induce even further, often unrecognized, changes in tumour oxygenation that may vary longitudinally, increasing or decreasing during treatment in ways that are not always predictable. Studies that fail to take cognizance of the actual physiological levels of oxygen in tissues (approximately 5%) and tumours (approximately 1%) may fail to identify the real circumstances driving tumour response to treatment and/or malignant progression. This can be of particular importance in genetic studies in vitro when comparison to human tumours is required.
肿瘤缺氧越来越被认为是癌症治疗中的一个主要有害因素，因为它会影响治疗效果并促使恶性进展。本文旨在澄清与这一问题相关的氧气水平。有人认为，常氧（20%氧气）与“乏氧”（即正常组织中普遍存在的低氧水平）相比是一个非常差的对照，正常组织中的氧水平平均约为 5%，范围在 3%到 7.4%之间。重要的是，应该认识到未经治疗的肿瘤的中位氧合水平显著低得多，介于约 0.3%到 4.2%的氧之间，大多数肿瘤的中位氧水平<2%。这部分取决于组织的起源，值得注意的是，许多前列腺和胰腺肿瘤严重缺氧。此外，治疗还会导致肿瘤氧合的进一步变化，这些变化通常是不可预测的，在治疗过程中可能会纵向增加或减少，而这些变化往往没有被认识到。如果研究未能认识到组织（约 5%）和肿瘤（约 1%）中实际的生理氧水平，就可能无法确定驱动肿瘤对治疗反应和/或恶性进展的真实情况。在需要与人类肿瘤进行比较的体外遗传研究中，这一点尤为重要。
