In this work

we investigated the bystander effect of the tumor and normal cells surrounding the target region caused by radiation-inducible target gene therapy combined with α-particle irradiation.The receptor tumor cell A549 and normal cell MRC-5 were co-cultured with the donor cells irradiated to 0.5 Gy or the non-irradiated donor cells

and their survival and apoptosis fractions were evaluated.The results showed that the combined treatment of Ad-ET and particle irradiation could induce synergistic antitumor effect on A549 tumor cell

and the survival fraction of receptor cells co-cultured with the irradiated cells decreased by 6%

compared with receptor cells co-cultured with non-irradiated cells

and the apoptosis fraction increased in the same circumstance

but no difference was observed with the normal cells.This study demonstrates that Ad-ET combined with α-particle irradiation can significantly cause the bystander effect on neighboring tumor cells by inhibiting cell growth and inducing apoptosis

without obvious toxicity to normal cells.This suggests that combining radiation-inducible TRAIL gene therapy and irradiation may improve tumor treatment efficacy by specifically targeting tumor cells and even involving the neighboring tumor cells.