Abstract:

Objective To investigate the radiosensitization effect of quercetin on cervical cancer HeLa cells and to explore its possible mechanism. Methods

Clone forming assay was used to observe the radiosensitizing effect of quercetin on HeLa cells after radiation with drug by various schedules and different drug concentrations（20% IC50 and IC50）. According to the experimental protocol， the experiments were carried out in radiation alone group， 20% IC50 quercetin+radiation group， radiation+20% IC50 quercetin group， IC50 quercetin+radiation group and radiation+IC50 quercetin group. The surviving fraction（SF） of above all groups after X-ray radiation of 12， 8， 6， 4， 2 and 0 Gy were calculated and the optimum schedule was selected. The below experiments were carried out in negative control group， quercetin group（20% IC50 and IC50）， radiation group and quercetin+irradiation group（20% IC50 and IC50）， and the dose of radiation was 4 Gy. Flow cytometry， DAPI staining， Western blotting（20%IC50 quercetin only） were explored to detect the cell cycle distribution， apoptotic changes and expression of Bcl-2 and Bax protein at 24 h after treatment. Results Compared with radiation alone group， the SF were reduced by the treatment of different concentration of radiation， quercetin in different sequence（P＜0.05）. The SF were inversely proportional to the concentration of quercetin， while the radiosensitization of quercetin was in concentration depended manner. Under the same concentration of quercetin and dose of X-ray，the SF in radiation+quercetin groups were lower than those in quercetin+radiation groups. DAPI staining showed that nucleus shrinkage were observed with the treatment of quercetin or radiation， and the combination of them could cause nucleus shrinkage and fragmentation more marked. Flow cytometry demonstrated that compare with other groups， quercetin+radiation groups could arrest cell cycle in G2/M phase（P＜0.05）. Western blotting showed that the levels of Bcl-2 protein was lowed in quercetin+radiation group than other groups（P＜0.05）；Bax levels increased in quercetin+radiation group， but it had no significance compared with quercetin group. Conclusion Quercetin has radiosensitization effect on HeLa cells and its effect is influenced by schedule and concentration of quercetin. The mechanism may be related to arrest of cell cycle in G2/M phase， cell apoptosis and the down-regulating the ratio of Bcl-2/Bax.