Abstract
Recently, heavy-ion radiotherapy attracts attention as a new cancer therapy, but the response of cancer cells which are irradiated by heavy-ion beams has not yet been clarified. Particularly, bystander effects are important to upgrade heavy-ion radiotherapy, because they may bring some influences to the outside of the irradiated area. So, it is required to clarify the mechanisms of bystander effects and their influences in the therapy. The purpose of this study is to detect bystander cell-killing effects between normal fibroblasts and lung cancer cells with different p53 status and to elucidate its mechanisms. In the study, we used human lung normal fibroblasts WI-38 line and human lung cancer cells H1299/wtp53 line which produces normal p53 proteins in their DNA damage response. We irradiated cells with carbon-ion broad beams (LET = 108 keV/μm, Dose = 0.5 Gy) or gamma-rays (LET = 0.2 keV/μm, Dose = 0.5 Gy), then calculated survival rates of bystander cells after 6- or 24-hours co-culture of irradiated and non-irradiated cells using colony formation assay. When we co-cultured irradiated H1299/wtp53 cells with non-irradiated WI-38 cells, it was found that survival rates of WI-38 cells were not decreased at all. Consequently, it was suggested that bystander cell-killing factors were not released from irradiated H1299/wtp53 cells.
