Clonogenic survival measurement of human glioblastoma (U87) cells cultured in 3Dbio-phantom after proton and X-ray irradiations

Abstract Background: Glioblastoma multiforme (GBM) is the most malignant brain tumor and is resistant to conventional radiotherapy. Proton radiotherapy utilizes accelerated proton beams to irradiate deep-seated tumor or cancer cells with minimum ionization in the entrance channel and maximum ionization in the tumor region, thanks to its inverted dose profile. The aim of this work is to investigate the response of human glioma (U87) cells grown in a 3D bio-phantom after irradiation using X-rays and proton beams. Methods: U87 cells have been cultured in matrigel matrix inside 96-well plate and incubated for 48 hours. Next, cells were irradiated using 6 MV X-rays and 70 MeV monoenergetic proton beams. Post-irradiation, the surviving cells were determined by a colony formation assay and cell survival fractions were plotted to obtain the survival curves of U87 after X-ray and proton irradiation. Results: The response of cells in the 3D bio-phantom following X-ray and pro-ton irradiations demonstrated an increased survival fraction in the high dose region compared to cells in the monolayer. However, U87 cells showed more sensitivity towards proton irradiation compared to X-ray irradiation, regardless of the culture setup. Finally, we obtained the RBE10% value of 1.15 for cells in 3Dbio-phantom and 1.29 for cells in monolayer. Conclusion: Based on the results, proton irradiation produces more cell killing compared to X-ray irradiation, and proton therapy could be an alternative treatment for treating glioblastoma without harming the neighboring healthy tissues.