Oxygen enhancement ratios of cancer cells after exposure to intensity modulated x-ray fields: DNA damage and cell survival

• Published in: Physics in medicine & biology Vol. 66; no. 7; pp. 75014 - 75024
• Main Authors: Matsuya, Yusuke, McMahon, Stephen J, Butterworth, Karl T, Naijo, Shingo, Nara, Isshi, Yachi, Yoshie, Saga, Ryo, Ishikawa, Masayori, Sato, Tatsuhiko, Date, Hiroyuki, Prise, Kevin M
• Format: Journal Article
• Language: English
• Published: England IOP Publishing 07.04.2021
• Subjects: cell survival; DNA damage; intensity modulated radiation fields; oxygen enhancement ratio; Oxygen enhancement ratio; Cell survival; Intensity modulated radiation fields; DNA damage
• ISSN: 0031-9155; 1361-6560
• DOI: 10.1088/1361-6560/abf011

Hypoxic cancer cells within solid tumours show radio-resistance, leading to malignant progression in fractionated radiotherapy. When prescribing dose to tumours under heterogeneous oxygen pressure with intensity-modulated radiation fields, intercellular signalling could have an impact on radiosensitivity between in-field and out-of-field cells. However, the impact of hypoxia on radio-sensitivity under modulated radiation intensity remains to be fully clarified. Here, we investigate the impact of hypoxia on in-field and out-of-field radio-sensitivities using two types of cancer cells, DU145 and H1299. Using a nBIONIX hypoxic culture kit and a shielding technique to irradiate 50% of a cell culture flask, oxygen enhancement ratios (OERs) for double-strand breaks (DSB) and cell death endpoints were determined. These in vitro measurements indicate that hypoxia impacts out-of-field cells, although the hypoxic impacts on out-of-field cells for cell survival were dose-dependent and smaller compared to those for in-field and uniformly irradiated cells. These decreased radio-sensitivities of out-of-field cells were shown as a consistent tendency for both DSB and cell death endpoints, suggesting that radiation-induced intercellular communication is of importance in advanced radiotherapy dose-distributions such as with intensity-modulated radiotherapy.