The role of p53 in bystander responses on normal liver cells were investigated by co-culturing irradiated hepatoma cells with non-irradiated bystander Chang liver cells.It was found that radiosensitivity of the hepatoma cells was relative to p53.HepG2 cells with wtp53 had the highest radiosensitivity followed by PLC/PRF/5 cells with mtp53 and Hep3B cells with null-p53.The induction of bystander micronucleus(MN) was observed only in the Chang liver cells that had been co-cultured with HepG2 cells but not co-cultured with PLC/PRF/5 or Hep3B.Also

this bystander MN was relative to the irradiation dose and the cell co-culture rime.When the hepatoma cells were treated with pifithrin-α

a p53 inhibitor

their radiosensitivities were reduced

and the bystander effect was diminished.The results indicate that p53 could regulate not only the radiosensitivity but also the bystander response.