Purpose: Gioblastoma multiforme as a chemoresistant and radioresistant malignant cell
line needs to novel strategies to treatment. Low-dose hyper-radiosensitivity (LDHRS) seems to be an
effective phenomenon to irradiation that can save normal brain fibroblasts. Genistein which is a soy
isoflavone can be cytotoxic in some tumor cell lines. So we determined to study the effect of combining
these two treatment modalities.
Materials and Methods: After 30 hours incubation with Genistein in different concentrations on
U87MG cell line, proliferation and clonogenicity were conducted by both clonogenic and MTT assays.
A conventional 2Gy radiation dose was compared with 10 doses of 0.2Gy gamma irradiation
with 3 minutes and 1 hour intervals. Finally, concurrent effect of these modalities was assessed.
Results: Based on acquired cell doubling time (30 hours), one doubling time treatment by Genistein
could decrease clonogenicity. U87MG cell line exhibited HRS at low dose irradiations. 2Gy irradiation
was more effective than ultra-fractionation methods in comparison with control group. All
groups with 50uM concentration of Genistein showed decrease in the survival. This decrease compared
with control group, in 10x0.2Gy with 3 minutes intervals plus 50uM Genistein was significant
and for groups with the same dose of Genistein but along with continuous 2Gy was more significant.
Conclusion: In one day treatment regimen, 10x0.2Gy ultra-fractionation with 3 minutes and 1 hour
intervals seems to be less effective than conventional 2Gy irradiation, however adding 50uM Genistein
can decrease survival more. Although 2Gy conventional dose plus 50uM Genistein was the most