P53-dependent cell-killing effect via bystander effect using carbon-ion microbeams simulating the spot scanning system with pencil beams at HIMAC

Suzuki, Masao*; Funayama, Tomoo; Yokota, Yuichiro; Suzuki, Michiyo; Ikeda, Hiroko; Sakashita, Tetsuya; Kobayashi, Yasuhiko; Murakami, Takeshi*

We irradiated either 4-cell lines with wild-type P53 or 4-cell lines with mutated-type P53 using the microbeams of JAEA-Takasaki collimated by 20m in diameter. We can easily estimate the number of the directly irradiated cells to be just 0.04% of the total cells on the dish using the highly controlled microbeam irradiation system. The percent survival in the cells with wild-type P53 was around 90%, while almost 100% was observed in the cells with mutated-type P53. The results are consistent with the data using the carbon-ion broad beams with the shielding method at HIMAC. Our overall results showed that bystander cell-killing effect was observed in the cells with wild-type P53, but not in the P53-mutated cells. There is clear evidence that the spot scanning irradiation system of carbon ions enables the enhanced cell killing in cells with wild-type P53 gene via gap-junction mediated bystander effect.