A Study On The Effect And Mechanism Of Dihydroartemisinin On The Radiosensitivity Of Hela And Siha Cells Of Cervical Cancer

Objective This study is to investigate the effect and mechanism of dihydroartemisinin(DHA) on radiosensitivity of p53 mutant HeLa cells and p53 wild type Siha cells.To determine the proper concentration and action time of DHA used in radiosensitising study by studing the inhibition effect of DHA on HeLa and Siha cells with change of the concentration and action time.To discuss the effect of DHA on the radiosensitivity of cells by the studing effect of DHA on proliferation capacity of HeLa and Siha cells after radiate.To discuss the mechanism of radiosensitising of DHA by the studing effect of DHA combined with X-ray on cell cycle and expression of cell cycle regulatory protein weel,cyclinB1 and cdc2.To compare and analyze the difference of radiosensitising effect and mechanism of DHA on human cervical cancer cells with different p53 states.Methods(1) The effect of DHA on survival fraction of human HeLa and Siha cells of cervical cancer was assessed by MTT assay.(2) The effect of DHA on radiosensitization on the cells was assessed by colony formation and cell apoptosis assay. (3) The changes of cell cycle distribution effected by DHA combined with X-ray irradiation was detected by flow cytometry.(4) Change of expression of cycle regulatory protein weel,cyclinB1,cdc2 caused by DHA combined with X-ray irradiation was investigated by Western blot.Results(1) The inhibition of DHA on human HeLa and Siha cells of cervical cancer were in concentration-dependent and time-depentent manners.(2) Inhibition rate of DHA to cells of different p53 state was different,when inhibition rate of DHA to HeLa and Siha cells both reached about 16%,drug concentration was 20μmol/L and 100μmol/L respectively.(3) With the same dose of radiation,clone formation rate decreased with the increase of concentration of DHA.With the same drug concentration,clone formation rate decreased with the increase of radiation dose.DHA had obvious radiosensitising effect to p53 mutant HeLa cells,while had no such effect to p53 wide type Siha cells.As to HeLa cells,in radiation group and drug plus radiation group,the mean lethal dose(D₀) was 2.32Gy and 1.58Gy respectively,and the quasi-threshold dose(Dq) was 1.18Gy and 0.59Gy respectively,so SER was 1.47.To Siha cells,the mean lethal dose(D₀) was 2.26Gy and 2.14Gy respectively,the quasi-threshold dose(Dq) was 1.18Gy and1.00Gy respectively,so SER was 1.06.(4) Flow cytometry results showed that,compared with apoptosis rate of 16.26%in radiation group,apoptosis rate of HeLa cells in drug combined with radiation group rised to 26.87%,and the difference was significant(p＜0.01).As in Siha cells,apoptosis rate of cells in radiation and drug combined with radiation group was 26.38%and 27.55%respectively,and the difference was not significant(p＞0.05).(5) Compared with radiation group,in HeLa cells,the percent of cells in G₁ phase increased and G₂ phase decreased in the radiation combined with drug group,and apoptosis also increased;in Siha cells,the G₁/S phase and G₂/M phase didn't show obvious change,the apoptosis also had no statistically significant change.(6) Western blot result showed that, compared with radiation group,in HeLa cells,expression of weel decreased and cyclinB1 increased while cdc2 had no significant change in radiation combined with drug group;in Siha cells,expression of wee1,cyclinB1 and cdc2 had no significant change.Conclusions(1) The inhibition of DHA on human HeLa and Siha cells of cervical cancer increased with concentrations and time.(2) DHA can increase the radiosensitivity of human HeLa cells of cervival cancer with p53 mutant,but had no such effect on wide type p53 Siha cells.(3) DHA can increase the radiosensitivity of human HeLa cells,the mechanism is related with G₂/M arrest induced by radiation,which probably drived more irradiation damaged cells to enter M phase,finally the cells died with no time to rapair,but in Siha cells,irradiation mainly induce G₁/S arrest without G₂/M arrest,so DHA had no radiosensitizing effect on Siha cells.(4) Treated with drug combined with radiation,expression of wee1 decreased and cyclinB1 increased in HeLa cells so as to weaken G₂/M arrest induced by radiation to show radiosensitising effect.In Siha cells treated with drug combined with radiation,expression of wee1 and cyclinB1 which is related to control of G₂/M arrest had no significant change.(5) Expression of cdc2 in HeLa and Siha cells treated with drug combined with radiation had no significant change,showing that it is possible that DHA can affect the expression of cdc2 through wee1,rather than affect expression of cdc2 directly.