The effect of Photon Activation Therapy on cisplatin pre-treated human tumour cell lines: comparison with conventional X-ray irradiation

Cisplatin is an antineoplastic drug widely used for the treatment of several solid tumours. However, the side effects related to cisplatin-based anticancer therapy often outweigh the benefits. Therefore, the identification of new anticancer strategies able to offer a better toxicity profile while maintaining the same level of efficacy as platinum-based treatments would be highly desirable. We assessed the efficacy of synchrotron radiation in triggering the Auger effect in human A549 non-small cell lung cancer and IGROV-1 ovarian cancer cells pre-treated with cisplatin. Cisplatin was chosen as the carrier of platinum atoms in the cells because of its alkylating-like activity and the irradiation was done with monochromatic beams above and below the platinum K-shell edge (78.39 keV). On cisplatin-treated cells, at concentrations allowing 80 percent of cell survival with respect to controls, no differences were observed in cell viability when they were irradiated either above or below the K-shell edge of platinum, suggesting that cisplatin toxicity can mask the enhancement of cell death induced by the irradiation. At lower cisplatin concentrations allowing 95-90 percent of cell survival, an enhancement in cellular death with respect to conventional irradiation conditions was clearly observed in all cancer types when cells were irradiated with beams either above or below the platinum K-shell edge. Our results lend additional support to the suggestion that the Photon Activation Therapy in combination with cisplatin treatment should be further explored in relevant in vivo models of glioma and non-glioma cancer models.