Revealing the biomolecular response of glioma cells to helium, carbon and oxygen minibeam radiation therapy using synchrotron-based infrared microspectroscopy

Abstract

Combining helium, carbon or oxygen beams with minibeam radiation therapy (MBRT) may benefit the treatment of radioresistant tumours while better protecting healthy tissues from radiation toxicities. In this study, the biomolecular response of glioma cell lines to HeMBRT, CMBRT and OMBRT was evaluated using synchrotron-based Fourier transform infrared microspectroscopy (SR-FTIRM). F98 (rat glioma) and U-87 MG (human glioma) cell lines were subjected to conventional broad beam RT (BB) or MBRT at the Heidelberg Ion-Beam Therapy Centre (Germany). Biomolecular effects were assessed with SR-FTIRM at the MIRAS beamline of the ALBA Synchrotron (Spain). Principal component analysis (PCA) uncovered the spectral alterations due to the different irradiation modalities. In F98 cells, IR signatures in the 1254–1225 cm⁻¹ spectral region, mainly related to DNA and RNA geometries, were altered by both BB and MBRT modalities and the two ion species. Alterations of IR signatures in the 1097–1074 cm⁻¹ spectral region, associated with the phosphodiester backbone of nucleic acids, and IR signatures associated with C–O vibrational modes in the 1110–1097 cm⁻¹ (mainly due to nucleic acids), 1182–1163 cm⁻¹ (mainly due to phospholipids), 1135–1110 cm⁻¹ and 1071–1040 cm⁻¹ (mainly due to carbohydrates) spectral regions, were generally enhanced by CMBRT; OBB and OMBRT also resulted in dose-dependent modifications of these spectral bands, suggesting nucleic acid modifications or oxidative damage. CMBRT, OBB and OMBRT also induced changes in IR signatures of the Amide I band associated with α-helical and β-sheet protein secondary structures, which might result from protein oxidation or cell death mechanisms. In U-87 MG cells, specific IR signatures in the Phosphate II band (i.e. 1173 cm⁻¹, 1150 cm⁻¹, 1080 cm⁻¹, 1065 cm⁻¹ and 1025 cm⁻¹), primarily associated with C–O signals present in phospholipids, carbohydrates and the phosphodiester backbone of nucleic acids, were greatly affected by helium-, carbon- and oxygen-ion RT, in both conventional and spatially fractionated modes. Biomolecular changes in the C–H vibrational modes of lipids for both cell lines were consistent with free radical attacks. Cell viability results revealed cell line-dependent sensitivities to treatment, with findings consistent with the modifications observed in the SR-FTIRM analysis.