Presentation Macrophage, Co-cultured with Irradiated Lung Cancer Cells, Plays a Role in Triggering Secondary Bystander Effects on Epithelial Cells

Shao, Chunlin  ,  Dong, Chen  ,  Tu, Wenzhi  ,  Konishi, Teruaki  ,  Uchihori, Yukio  ,  Furusawa, Yoshiya

Microbeam particles can precisely target sub-cellular organs and hence has become an advantageous tool in studying the mechanisms of low dose radiation responses including radiation-induced bystander effect (RIBE). Besides nuclei, mitochondria and endoplasmic reticulum in cytoplasm may be involved in RIBE as potential radiation targets. When only one or few cells in a population with million cells were irradiated with microbeam particles through either nuclei or cytoplasm, DNA damage could be observed in thousands of other nonirradiated cells, which hints that radiation induced signals could be transferred from one cell to other cells. But so far no direct evidence to show that any cell plays a role as an intermediate between irradiated cells and nonirradiated cells. Here we found when macrophage U937 cells were co- cultured with lung cancer cells NCI-H446 irradiated with either y-rays or carbon ions, this U937 became a bystander signal transmitter and could further induce DNA damage in its neighboring bronchial epithelial cells BEAS-2B. Interestingly, U937 cells were only activated by y-irradiated NCI-H446 cells so that the secondary injuries in BEAS-2B cells under carbon ions irradiation were weaker than y-rays. Both TNF-a and IL-1α were involved in y-irradiation induced abscopal effect but only TNF-α contributed to carbon irradiation-induced response. Further assay disclosed that IL-1α but not TNF-α was largely responsible for the activation of macrophages and micronucleus formation in BEAS-2B cells. These data suggest that macrophage as a transmitter plays an important role in the abscopal effect of photon irradiation, while carbon ion irradiation has conspicuous advantage due to its reduced abscopal injury.
15th International Congress of Radiation Research

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