Expression of FHIT in AHH-1 cells irradiated by ^60 Co γ-ray and bystander effect cells

Objective To investigate the expression of FHIT gene in the ^60 Co gamma-ray irradiated human lymphocytoblast （AHH-1） cell and the bystander effect cell, and to explore the function of FHIT gene in the bystander effect of ionizing radiation. Method Preparation of bystander effect cell model： after irradiated with different dose of ^60 Co gamma-ray （0, 2, 5 Gy）, the directly irradiated AHH-1 cells were collected immediately by eentrifugation and co-cultivated with non-irradiated cells in Transwell, forming the bystander effect group P1. In addition, some culture media supematant of directly irradiated cells were transferred to the non- irradiated cells culture medium, forming the group P2. Then cells were collected at 0, 6, 12, and 24 h after irradiation and the total RNA and protein were extracted. RT-PCR and Western blot were performed to determine the FHIT mRNA and protein level, respectively. Flow eytometry assay and cell counting were conducted to detect the alteration of cell cycle and cell proliferation, respectively at 0, 24 h after irradiation. Results The mRNA level of FHIT gene among control cells, directly irradiated cells and bystander cells showed no obvious difference, while the FHIT protein level of the directly irradiated cells and bystander cells was significantly down-regulated compared with the control cells （ F = 102.45, P 〈 0.001 ）. Moreover, the directly irradiated cells and bystander cells showed significant G2 phase arrest and obviously inhibited the proliferation ability. Conclusions 2 and 5 Gy of ^60Co γ-ray irradiated AHH-1 cells can result in down regulation of the FHIT protein expression, which suggests that FHIT gene is involved in the process of bystander effect induced by irradiation. Key words: ^60Co γ ray;  Bystander effect;  AHH-1 cell;  FHIT