Raman spectroscopy to evaluate radiobiological sensitivity of normal human breast cells at different time points after irradiation by a clinical proton beam

Among different radiotherapy techniques, proton irradiation is an established and effective method for treatment of several types of cancer, because less healthy tissue is exposed with respect to conventional radiotherapy by photons/electrons. Recently, proton therapy has been proposed for the treatment of breast cancer. In vitro study of proton irradiated normal human breast cells can provide information about cellular radioresponse, particularly as far as healthy tissue is concerned. In this paper, a study of the effects at different time points, following proton irradiation at different doses, of human normal MCF10A breast cells is performed by Raman spectroscopy. The aim of this investigation is to detect unwanted effects of proton treatment and to investigate the possibility to monitor them and to assess the cellular sensitivity by means of such a technique. The obtained results seem to indicate a rather significant sensitivity of MCF10A cells to proton irradiation. In fact, even at doses as low as 0.5 Gy, biological effects are clearly detectable in Raman spectra. In particular, ratiometric analysis of the Raman spectra measured from the nucleoplasm compartment showed that DNA/RNA damage increases with time, suggesting that most of cells are unable to repair DNA/RNA broken bonds. The results obtained by the Raman spectroscopy analysis exhibit a similar trend with dose to those obtained by commonly used radiobiological assays (i.e. MTT, clonogenic assay, senescence, apoptosis and necrosis). The results of this study strongly suggest the possibility that Raman technique can be used to identify molecular markers predicting radiation response.