Supplementary MaterialsS1 Fig: Representative images of colonies formed by Mel270 and BLM cells. trajectory with initial point of each trajectory set at the 0 point of the diagram. Cells were seeded 20 days after irradiation with proton beam or X-rays. Cell movement was recorded for 10 hrs, with 10 min intervals. A representative transmitted light image of the cells is to the right (magnification ML367 200x).(TIF) pone.0186002.s004.tif (1.6M) GUID:?719C04D1-CED3-47B7-9955-3E85DA59EB99 Data Availability StatementAll relevant data are within the paper and its Supporting Information files. Abstract Purpose In recent years experimental data have indicated that low-energy proton beam radiation might induce a difference in cellular migration in comparison to photons. We therefore set out to compare the effect of proton beam irradiation and X-rays on the survival and long-term migratory properties of two cell lines: uveal melanoma Mel270 and skin melanoma BLM. Materials and methods Cells treated with either proton beam or X-rays were analyzed for their survival using clonogenic assay and MTT test. Long-term migratory properties were assessed with time-lapse monitoring of individual cell movements, wound test and transpore migration, while the expression of the related proteins was measured with western blot. Results Exposure to proton beam and X-rays led to similar survival but the quality of the cell colonies was markedly different. More paraclones with a low proliferative activity and fewer highly-proliferative holoclones were found after proton beam irradiation in comparison to X-rays. At 20 or 40 days post-irradiation, migratory capacity was decreased more by proton beam than by X-rays. The beta-1-integrin level was decreased in Mel270 cells after both types of radiation, while vimentin, a marker of EMT, was increased in BLM cells only. Conclusions We conclude that proton beam irradiation induced long-term inhibition of cellular motility, as well as changes in the level of beta-1 integrin and vimentin. If confirmed, the change in ML367 the quality, TNFAIP3 but not in the number of colonies after proton beam irradiation ML367 might favor tumor growth inhibition after fractionated proton therapy. Introduction Proton beam radiation is used to treat malignancies because of its superior biophysical properties concerning dose deposition in tissues compared to ML367 photon radiation [1]. In contrast to the widely accepted view, that the two types of radiation exert similar biological effects in tissues, with the relative biological effectiveness of 1 1.1, several intriguing differences between low-energy proton beam and photon irradiated tumor cells have been reported. For example, homologous recombination was more significant for proton beam induced DNA damage [2]. High-LET proton beam irradiation caused cluster DNA damage with higher complexity with increasing LET [3], but low-LET proton beam caused similar DNA damage to photon irradiation [4]. Other differences were found in the level of the production of free radicals, cell cycle inhibition and apoptotic signaling [5]. In vitro treatment of tumor cells with a proton beam resulted in a higher percentage of apoptotic cells when compared to photon radiation [6]. Additionally, differences were observed in cell cycle regulation: a high-LET proton radiation induced a G2 phase arrest which was noticeably longer and harder to resolve in comparison to similar doses of photon radiation [7]. This was not seen for low-LET proton radiation [8]. Radiation may also affect the formation of metastasis, including cell detachment from the primary tumor, migration along the extra-cellular matrix (ECM), degradation of the basement membrane, and intravasation into the blood or lymphatic vessels [9]. Tumor cell-migration itself is a multistage process which depends on various factors such as proteinase activity [10,11], the cytoskeleton organization of the migrating cells [12] and adhesion to the ECM mediated by receptors such as integrins. Radiation may affect many of these steps, and a differential influence of proton and photon radiation has been suggested [5]. As proton beam therapy as well as radio-active plaque therapy are mainstays in the treatment of uveal melanoma, we wondered how these different approaches affected melanoma cells. We therefore studied the long-term effects of sublethal doses of proton beam irradiation and of photon treatment on the migratory properties of uveal melanoma and metastatic human melanoma skin cells. We tested cellular survival, motility and the level of 1-integrin and vimentin after proton beam and photon irradiation and showed that proton beam, but not photon irradiation, inhibited cellular rectilinear motility and changed heterogeneity of colonies. These effects were.