Survival Analysis of F98 Glioma Rat Cells Following Minibeam or Broad-Beam Synchrotron Radiation Therapy

Silvia Gil,Albert Biete,Manel Sabés,Yolanda Prezado,Sukhéna Sarun

doi:10.1186/1748-717x-6-37

Abstract

BackgroundIn the quest of a curative radiotherapy treatment for gliomas new delivery modes are being explored. At the Biomedical Beamline of the European Synchrotron Radiation Facility (ESRF), a new spatially-fractionated technique, called Minibeam Radiation Therapy (MBRT) is under development. The aim of this work is to compare the effectiveness of MBRT and broad-beam (BB) synchrotron radiation to treat F98 glioma rat cells. A dose escalation study was performed in order to delimit the range of doses where a therapeutic effect could be expected. These results will help in the design and optimization of the forthcoming in vivo studies at the ESRF.MethodsTwo hundred thousand F98 cells were seeded per well in 24-well plates, and incubated for 48 hours before being irradiated with spatially fractionated and seamless synchrotron x-rays at several doses. The percentage of each cell population (alive, early apoptotic and dead cells, where either late apoptotic as necrotic cells are included) was assessed by flow cytometry 48 hours after irradiation, whereas the metabolic activity of surviving cells was analyzed on days 3, 4, and 9 post-irradiation by using QBlue test.ResultsThe endpoint (or threshold dose from which an important enhancement in the effectiveness of both radiation treatments is achieved) obtained by flow cytometry could be established just before 12 Gy in the two irradiation schemes, whilst the endpoints assessed by the QBlue reagent, taking into account the cell recovery, were set around 18 Gy in both cases. In addition, flow cytometric analysis pointed at a larger effectiveness for minibeams, due to the higher proportion of early apoptotic cells.ConclusionsWhen the valley doses in MBRT equal the dose deposited in the BB scheme, similar cell survival ratio and cell recovery were observed. However, a significant increase in the number of early apoptotic cells were found 48 hours after the minibeam radiation in comparison with the seamless mode.

Highlights

In the quest of a curative radiotherapy treatment for gliomas new delivery modes are being explored
Synchrotron sources are ideal for spatially fractionated techniques such as Microbeam Radiation Therapy (MRT) and Minibeam Radiation Therapy (MBRT), currently under development at the European Synchrotron Radiation Facility -ESRF- in Grenoble, France
Data obtained from the QBlue assays on days 3, 4, and 9 after both, MBRT and Broad Beam (BB), are shown

Summary

Introduction

In the quest of a curative radiotherapy treatment for gliomas new delivery modes are being explored. The reason is that synchrotron beams possess two relevant features: a negligible divergence allowing to have sharp defined irradiation edges, and a 106 times higher fluence of x-rays than standard medical irradiators, which permits to avoid the beam smearing to the cardiosynchronous pulsations [2]. These two innovative techniques, MRT and MBRT, are based on the dose-volume effect: the smaller the irradiated volume is, the higher the dose tolerances of the healthy tissue are [3]. The energy spectrum employed ranges from 50 to 500 keV, and with a mean energy at around 100 keV [4]

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