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Combined effects of cisplatin and photon or proton irradiation in cultured cells: radiosensitization, patterns of cell death and cell cycle distribution.

ABSTRACT: The purpose of the current study was to investigate the biological effects of protons and photons in combination with cisplatin in cultured cells and elucidate the mechanisms responsible for their combined effects. To evaluate the sensitizing effects of cisplatin against X-rays and proton beams in HSG, EMT6 and V79 cells, the combination index, a simple measure for quantifying synergism, was estimated from cell survival curves using software capable of performing the Monte Carlo calculation. Cell death and apoptosis were assessed using live cell fluorescence imaging. HeLa and HSG cells expressing the fluorescent ubiquitination-based cell cycle indicator system (Fucci) were irradiated with X-rays and protons with cisplatin. Red and green fluorescence in the G1 and S/G2/M phases, respectively, were evaluated and changes in the cell cycle were assessed. The sensitizing effects of ?1.5 ?M cisplatin were observed for both X-ray and proton irradiation (P < 0.05). In the three cell lines, the average combination index was 0.82-1.00 for X-rays and 0.73-0.89 for protons, indicating stronger effects for protons. In time-lapse imaging, apoptosis markedly increased in the groups receiving ?1.5 ?M cisplatin + protons. The percentage of green S/G2/M phase cells at that time was higher when cisplatin was combined with proton beams than with X-rays (P < 0.05), suggesting more significant G2 arrest. Proton therapy plus ?1.5 ?M cisplatin is considered to be very effective. When combined with cisplatin, proton therapy appeared to induce greater apoptotic cell death and G2 arrest, which may partly account for the difference observed in the combined effects.

SUBMITTER: Iwata H

PROVIDER: S-EPMC7674701 | biostudies-literature | 2020 Nov

REPOSITORIES: biostudies-literature

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Combined effects of cisplatin and photon or proton irradiation in cultured cells: radiosensitization, patterns of cell death and cell cycle distribution.

Iwata Hiromitsu H Shuto Tsuyoshi T Kamei Shunsuke S Omachi Kohei K Moriuchi Masataka M Omachi Chihiro C Toshito Toshiyuki T Hashimoto Shingo S Nakajima Koichiro K Sugie Chikao C Ogino Hiroyuki H Kai Hirofumi H Shibamoto Yuta Y

Journal of radiation research 20201101 6

The purpose of the current study was to investigate the biological effects of protons and photons in combination with cisplatin in cultured cells and elucidate the mechanisms responsible for their combined effects. To evaluate the sensitizing effects of cisplatin against X-rays and proton beams in HSG, EMT6 and V79 cells, the combination index, a simple measure for quantifying synergism, was estimated from cell survival curves using software capable of performing the Monte Carlo calculation. Cel ...[more]

PMID: 32880637

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Project description:PurposeCompared with photon cranial radiation therapy (X-CRT), proton cranial radiation therapy (P-CRT) offers potential advantages in limiting radiation-induced sequalae in the treatment of pediatric brain tumors. This study aims to identify cognitive, functional magnetic resonance and positron emission tomography imaging markers and molecular differences between the radiation modalities.Methods and materialsJuvenile rats received a single faction of 10 Gy (relative biological effectiveness-weighted dose) delivered with 6 MV X-CRT or at the midspread out Bragg peak of a 100 MeV P-CRT beam. At 3, 6, and 12 months post-CRT, executive function was measured using 5-choice serial reaction time task. At ∼12 months post-CRT, animals were imaged with 18F-Flurodeoxy-glucose positron emission tomography imaging followed by functional ex vivo magnetic resonance imaging and stained for markers of neuroinflammation.ResultsIrradiated animals had cognitive impairment with a higher number of omissions and lower incorrect and premature responses compared with sham (P ≤ .05). The accuracy of the animals' X-CRT was less than that of sham (P ≤ .001). No significant difference in rates of cognitive change were found between the radiation modalities. At 12 months post-CRT, glucose metabolism was significantly higher than sham in X-CRT (P = .04) but not P-CRT. Using diffusion tensor imaging, P-CRT brains were found to have higher white matter volume and fiber lengths compared with sham (P < .03). Only X-CRT animals had higher apparent diffusion coefficient values compared with sham (P = .04). P-CRT animals had more connectomic changes compared with X-CRT. Correlative analysis identified several imaging features with cognitive performance. Furthermore, microgliosis (P < .05), astrogliosis (P < .01), and myelin thinning (P <.05) were observed in both radiation modalities, with X-CRT showing slightly more inflammation.ConclusionsBoth P-CRT and X-CRT lead to neurocognitive changes compared with sham. Although no significant difference was observed in neuroinflammation between the irradiated groups, differences were found in late-term glucose metabolism and brain connectome. Our results indicate that despite relative biological effectiveness weighting of the proton dose there are still differential effects which warrants further investigation.

Project description:The growing number of particle treatment facilities worldwide and patients treated with particles instead of X-rays marks the upcoming rearrangement of modern radiotherapy. Especially for tumors being difficult to access and for tumors that are resistant to conventional X-ray treatment particle radiotherapy is a beneficial technology. At the Heidelberg Ion Beam Therapy Center (HIT) patients are treated with this technology since 2009 as it offers clear benefits. Contrary to X-rays, which show an exponential dose decrease (after reaching electron equilibrium) with increasing tissue depth, charged particles deposit most of their energy to a small region within the tissue with a sharp dose fall-off after the so-called Bragg peak. This precise dose localization enables further dose escalation within the tumor while sparing healthy tissue. Besides physical advantages, particle radiotherapy offers additional biological advantages. In radiobiology, the term relative-biological effectiveness (RBE) is defined as the ratio of X-rays dose to an alternative irradiation modality dose which produce the same biological effect (e.g. survival or number of DSBs). While protons have a relative biological effectiveness (RBE) comparable to X-rays, carbon ions are more effective in inducing DNA damage(1, 2) and are therefore especially useful for radioresistant tumors. This is due to the fact, that carbon ions induce clustered and direct DNA damage, which is considered to be less dependent on cell cycle stage, oxygen level, genetic background and hinders DNA repair mechanisms(3–6). Nevertheless, their exact mode of action and cellular mechanisms are largely unknown. We show the first comprehensive proteomic and phosphoproteomic study elucidating the cellular response to treatment with protons, carbon ions and X-rays. We found that 2h after treatment with these radiations negligible regulation occurred at protein expression level. But 181 phosphorylation sites were deregulated by ionizing radiation contributing mainly to DNA damage response functionalities. Interestingly we found 55 phosphorylation sites being differentially regulated between the radiations. Here, we observed protons and carbon ions producing equal cellular response whereas X-rays show altered regulation for certain phosphorylation sites. A subset of 28 phosphorylation sites being involved in the DNA damage response or differentially regulated between the ionizing radiations was selected for result confirmation.

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Dataset Information

Combined effects of cisplatin and photon or proton irradiation in cultured cells: radiosensitization, patterns of cell death and cell cycle distribution.

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Combined effects of cisplatin and photon or proton irradiation in cultured cells: radiosensitization, patterns of cell death and cell cycle distribution.

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