Application of soft-X-ray microbeams in radiation biology

Abstract

Evidence is accumulating that irradiated cells produce some signals which interact with non-exposed cells in the same population. Understanding this "Bystander effect" from ionizing radiation is important for understanding low dose effects on a cell population. In our COE program, we have been continuing a collaboration with the Gray Cancer Institute. The Gray Cancer Institute ultrasoft X-ray microprobe is a powerful tool for investigating the bystander effects, because it permits the irradiation of only a single cell nucleus within a population. The results suggest that bystander signals eventually induce DNA double strand breaks in non-exposed cells. Also, radical species induced intracellularly by ionizing radiation are involved in producing bystander signals in exposed cells. In these experiments there was no cell-to-cell contact between exposed and non-exposed cells. Therefore, it is possible that bystander factors such as cytokines from exposed cells are secreted and this secretion is influenced by signal activation related to radical species produced outside of the cell nucleus of the targeted cells. As an advanced new ultrasoft-X-ray microbeam has been introduced from Gray Cancer Institute to Nagasaki University, this facility will be a powerful tool for radiation biology in Asia.