Details

Autor(en) / Beteiligte

• Kyle, Alastair H.
• Karan, Tania
• Baker, Jennifer H.E.
• Püspöky Banáth, Judit
• Wang, Taixiang
• Liu, Anam
• Mendez, Claudia
• Peter Petric, M.
• Duzenli, Cheryl
• Minchinton, Andrew I.

Titel

Detection of FLASH-radiotherapy tissue sparing in a 3D-spheroid model using DNA damage response markers

Ist Teil von

• Radiotherapy and oncology, 2024-07, Vol.196, p.110326, Article 110326

Ort / Verlag

Ireland: Elsevier B.V

Erscheinungsjahr

2024

Quelle

MEDLINE

Beschreibungen/Notizen

• •FLASH-RT protection was characterized in a 3D-tissue spheroid-model using DNA Damage Response markers as a readout of radiation response.•The degree of FLASH-RT protection was observed to be dose and oxygen dependent, with the model predicting a maximal FLASH dose-modifying protection factor of 1.1 at 15 Gy and 1.3 at 50 Gy.•Modelling of the observed protective effect by assuming a radiolytic-oxygen-consumption process yielded an estimate for FLASH-RT tissue oxygen consumption of 0.73 ± 0.25 µM/Gy with a km of 5.4 µM. The oxygen depletion hypothesis has been proposed as a rationale to explain the observed phenomenon of FLASH-radiotherapy (FLASH-RT) sparing normal tissues while simultaneously maintaining tumor control. In this study we examined the distribution of DNA Damage Response (DDR) markers in irradiated 3D multicellular spheroids to explore the relationship between FLASH-RT protection and radiolytic-oxygen-consumption (ROC) in tissues. Methods: Studies were performed using a Varian Truebeam linear accelerator delivering 10 MeV electrons with an average dose rate above 50 Gy/s. Irradiations were carried out on 3D spheroids maintained under a range of O2 and temperature conditions to control O2 consumption and create gradients representative of in vivo tissues. Results: Staining for pDNA-PK (Ser2056) produced a linear radiation dose response whereas γH2AX (Ser139) showed saturation with increasing dose. Using the pDNA-PK staining, radiation response was then characterised for FLASH compared to standard-dose-rates as a function of depth into the spheroids. At 4 °C, chosen to minimize the development of metabolic oxygen gradients within the tissues, FLASH protection could be observed at all distances under oxygen conditions of 0.3–1 % O2. Whereas at 37 °C a FLASH-protective effect was limited to the outer cell layers of tissues, an effect only observed at 3 % O2. Modelling of changes in the pDNA-PK-based oxygen enhancement ratio (OER) yielded a tissue ROC g0-value estimate of 0.73 ± 0.25 µM/Gy with a km of 5.4 µM at FLASH dose rates. Conclusions: DNA damage response markers are sensitive to the effects of transient oxygen depletion during FLASH radiotherapy. Findings support the rationale that well-oxygenated tissues would benefit more from FLASH-dose-rate protection relative to poorly-oxygenated tissues.