Abstract
Our studies using X-ray microplanar beams generated with synchrotron radiation clearly showed that the recovery from reproductive cell death was quite different between normal and tumor cells. One possible mechanism might be the bystander effect between irradiated and unirradiated cells by X-ray microplanar beams, however it is still unknown not only biological effect itself but also its mechanism. This year we focused on the relationship between p53-gene status and bystander response to explain the phenomenon. Two p53-wild type normal human cells, one p53-wild type tumor cell line and two p53-mutated type tumor cell lines were irradiated with 25µm-thin (200µm beam space) X-ray microplanar beams generated with the SPring-8 at Japan Synchrotron Radiation Research Institute. The results showed that the recovery from reproductive cell death was occurred in the p53-wild type cells after 12h of post-irradiation incubation, while no recovery was observed in the p53-mutated type cells. Furthermore, the recovery observed in the p53-wild type cells was suppressed to the similar level of the reproductive cell death observed in the p53-mutated type cells, when using a specific inhibitor of gap-junction mediated cell-cell communications together. Our present results suggest that p53-mediated cellular responses play an important role of repair process between irradiated and unirradiated cells with X-ray microplanar beams.
