Effects of 60 MeV protons and 250 kV X-rays on cell viability

Particle radiotherapy such as the one using proton beams, provides a successful treatment approach in many cancer types. However, the cellular and molecular mechanisms by which proton irradiation induces cell death, particularly in a human peripheral blood lymphocyte model has not been examined in detail. Comparative studies of the biological effects, such as cell death, of particle therapy versus conventional X-rays treatment are of utmost importance. Here, we compared the viability of human peripheral blood lymphocyte following in vitro irradiation with protons (therapeutic 60 MeV proton beam) and photon beam (250 kV, X-rays), by applying separate doses within the range of 0.3-4.0 Gy. Cell viability was assessed 1 and 4 h after irradiation with protons and X-rays by the FITC-Annexin V labelling procedure (Apoptotic & Necrotic & Healthy Cells Quantification Kit, Biotium). Results showed that irradiation with both radiation types reduced the number of viable cells in a dose-dependent manner, as assessed as a function of the duration of post-irradiation time. Protons proved more fatal to the cells treated than X-ray photons. This demonstrates a difference in cell viability after irradiation with protons and photons in a human peripheral blood lymphocyte model.