1,139 research outputs found
Targeting Tumor Perfusion and Oxygenation Modulates Hypoxia and Cancer Sensitivity to Radiotherapy and Systemic Therapies
Hypoxia, a partial pressure of oxygen (pO2) below physiological needs, is a limiting factor affecting the efficiency of radiotherapy. Indeed, the reaction of reactive oxygen species
(ROS, produced by water radiolysis) with DNA is readily reversible unless oxygen stabilizes
the DNA lesion. While normal tissue oxygenation is around 40 mm Hg, both rodent and
human tumors possess regions of tissue oxygenation below 10 mm Hg, at which tumor cells
become increasingly resistant to radiation damage (radiobiological hypoxia) (Gray, 1953).
Because of this so-called “oxygen enhancement effect”, the radiation dose required to
achieve the same biologic effect is about three times higher in the absence of oxygen than in
the presence of normal levels of oxygen (Gray et al., 1953; Horsman & van der Kogel, 2009).
Hypoxic tumor cells, which are therefore more resistant to radiotherapy than well
oxygenated ones, remain clonogenic and contribute to the therapeutic outcome of
fractionated radiotherapy (Rojas et al., 1992)
Targeting Tumor Perfusion and Oxygenation to Improve the Outcome of Anticancer Therapy1
Radiotherapy and chemotherapy are widespread clinical modalities for cancer treatment. Among other biological influences, hypoxia is a main factor limiting the efficacy of radiotherapy, primarily because oxygen is involved in the stabilization of the DNA damage caused by ionizing radiations. Radiobiological hypoxia is found in regions of rodent and human tumors with a tissue oxygenation level below 10 mmHg at which tumor cells become increasingly resistant to radiation damage. Since hypoxic tumor cells remain clonogenic, their resistance to the treatment strongly influences the therapeutic outcome of radiotherapy. There is therefore an urgent need to identify adjuvant treatment modalities aimed to increase tumor pO2 at the time of radiotherapy. Since tumor hypoxia fundamentally results from an imbalance between oxygen delivery by poorly efficient blood vessels and oxygen consumption by tumor cells with high metabolic activities, two promising approaches are those targeting vascular reactivity and tumor cell respiration. This review summarizes the current knowledge about the development and use of tumor-selective vasodilators, inhibitors of tumor cell respiration, and drugs and treatments combining both activities in the context of tumor sensitization to X-ray radiotherapy. Tumor-selective vasodilation may also be used to improve the delivery of circulating anticancer agents to tumors. Imaging tumor perfusion and oxygenation is of importance not only for the development and validation of such combination treatments, but also to determine which patients could benefit from the therapy. Numerous techniques have been developed in the preclinical setting. Hence, this review also briefly describes both magnetic resonance and non-magnetic resonance in vivo methods and compares them in terms of sensitivity, quantitative or semi-quantitative properties, temporal, and spatial resolutions, as well as translational aspects
Application of Electron Paramagnetic Resonance (EPR) Oximetry to Monitor Oxygen in Wounds in Diabetic Models
Metabolic changes associated with tumor metastasis, part 2: Mitochondria, lipid and amino acid metabolism
Metabolic changes associated with tumor metastasis, part 1: Tumor pH, glycolysis and the pentose phosphate pathway
Intrinsic and irradiation-induced tumor selectivity of liposome-based gene therapy targeting Akt activation.
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