Artiste linear accelerator

Cell monolayers at 75% confluence on cover slides in six-well plates (see above for details) were irradiated with 4 Gy total dose by 6 MeV photons using an Artiste linear accelerator (Siemens, Munich, Germany). Cells were transported at 37 ${}^{\circ }$ C and irradiated at ambient temperature (approx. 20–25 ${}^{\circ }$ C). Cells were kept at cell culture ambient conditions and fixed at 45–60 min after irradiation (see Figure S2).

Radiation treatment was delivered once a day, five times per week, using Siemens ARTISTE Linear Accelerator.

A total of 15 patients, who had undergone breast conserving surgery (BCS), were retrospectively selected for this study according to the breast separation. The patients received three‐field treatment using wedged‐field and field‐within‐a‐field tangents (FIF) for the opposing tangential and a slightly oblique anterior field for the SCV region. Eight patients had right‐sided breast cancer and seven had left‐sided breast cancer. The separation between the medial and lateral aspect of the breast were grouped to small, medium, and large (Table 1). All the patients were treated with 6 and 10 MV photons on Siemens ARTISTE linear accelerator (Siemens Medical Solutions USA, Inc., Malvern, PA). Weekly megavoltage (MV) imaging was acquired to verify patient positioning and AlignRT (Vision RT, London, UK) was used for daily patient setup. The prescription dose was 50 Gy in 25 fractions to the breast and 46 Gy to 50 Gy to the supraclavicular lymph nodes.

C57BL/6-N mice (2-month-old) were purchased from Charles River Laboratories (Sulzfeld, Germany) and housed in pathogen-free rooms to minimize infection risks, and supplied with a standard laboratory diet and water ad libitum. For whole-body irradiation (6-MV photons; dose-rate, 2 Gy/min) using an Artiste™ linear accelerator (Siemens, Munich, Germany), the animals were placed in an 18 cm-diameter Plexiglass cylinder covered by 1.5 cm thick plastic to improve dose homogeneity. Computed-tomography-based three-dimensional dose calculations were made with the Pinnacle planning system (Philips Radiation Oncology Systems, Fitchburg, WI, USA). Animals were irradiated with single-doses (10 Gy or 2 Gy) or with fractionated IR (once daily from Monday to Friday: 5 × 2 Gy, 20 × 0.1 Gy). At defined time-points after the last IR exposure, mice were anesthetized, perfused, and the lungs were removed, fixed overnight in 4% paraformaldehyde (Sigma-Aldrich Chemie GmbH, Munich, Germany), and processed for further analysis. At least three biological (experimental animals) and three technical (whole lung slices) replicates were examined for each irradiation regimen. The experimental protocol was approved by Medical Sciences Animal Care and Use Committee of Saarland University.