Objective      To examine the effect of Genistein combined with radiotherapy on the proliferation

apoptosis and Ape1/Ref1 protein expression of human pulmonary adenocarcinoma cell line A549.      Methods      A549 cells were divided into 4 groups including a control group (cells with no treatment)

a Genistein group (cells treated with Genistein in the doses of 0 μmol/L

10 μmol/L

30 μmol/L

60 μmol/L and 90 μmol/L

respectively

for 48 h)

an IR group (cells treated with a 8 Gy irradiation) and a Genistein +IR group (cells pretreated with the same doses of Genistein for 24 h and with a 8 Gy irradiation by a linear accelerator and continuously cultured for another 24 h). The cell proliferation was examined by methyl thiazolyl tetrazolium (MTT) assay to determine a most suitable Genistein concentration combined with radiotherapy. Cell apoptosis of the 4 groups was observed by flow cytometry

and Ape1/Ref1 protein expression was measured by Western blotting.      Results      The inhibition rate of cell proliferation was higher in the treatment of 30 μmol/L，60 μmol/L and 90 μmol/L Genistein combined with irradiation than in the same doses of Genistein treatment alone (P0.05)

and the most suitable concentration of Genistein was 30 μmol/L. No significant difference was found between the cells treated with low concentration (10 μmol/L) of Genistein combined with irradiation and with irradiation alone [(26.67±1.26)% vs (24.70±0.72)%

P=0.102]. The early apoptotic rates of the IR group and the Genistein+IR group were significantly higher than that of the control group[(30.88±7.63)%

(42.98±1.46)% vs (6.80±0.98)%

respectively

P0.05]

while there was no statistical difference between the control group and the Genistein group [(12.96±4.99)% vs (6.80±0.98)%

P=0.143]. As compared with the Ape1/Ref1 protein expression of the control group

the IR group and the Genistein group

that of the Genistein+IR group decreased significantly.      Conclusion      Genistein (30 μmol/L) can enhance the inhibition effect of radiotherapy on A549 cell proliferation through the reduction of Ape1/Ref1 protein expression.