The Establishment Of Cell Substrain To IR And Investigate The Potentiall Mechanism Of The Radioresistance In Breast Cancer

Objective:Because of large individual differences about breast cancer patients, the radio-resistanceoften occur in radiation therapy in clinical practice. Therefore, explore the mechanism ofthe molecular biology about radio-resistance phenomenon has very important significanceto improve tumor cells being sensitive to radiation and improve the effect of radiotherapy.In this study, firstly, we intend to explore the method of inducing and building breastcancer cell subline with radiation resistance, and then to investigate the potentialmechanism of the radioresistance in breast cancer.Methods:The subject is human breast cancer MCF-7cell line, cultivating MCF-7in vitro,Simulating the clinical radiotherapy, the breast cancer cell line MCF-7were repeatedlygiven individual dose of X-rays with liner accelerator to induce radiation resistance, thechanges of cell morphology, cell cycle, apoptosis rate and radio sensibility in the inducedcell line were compared with the parental cell line at the end of inducing course. Theintracellular ultrastructure of the strains were observed by scanning electron microscopyand transmission electron microscopy; the cell cycle rate and apoptosis rate were examinedby Flow Cytometry; both of the cell intro-radiosensitivity were assayed by ColonyFormation assay, and calculated the survival fraction, clicked the multi-target model whichfitting the cell survival curve; Western bloting detected the pAkt and HIF-1α inMCF-7,MCF-7R,MCF-7+6Gy and MCF-7R+6Gy, in order to investigate the intialmechanisms of radio resisitance in breast cancer. Results:The resistance to radiation MCF-7R compared with the parental line MCF-7:1. Microscope and electron microscopy show that there were significant changes inmorphology such as shape and organelles.2. The percentage of G0/G1phase increased from52.81±0.14to57.65±1.09(P<0.01); S phase percentage decreased from33.39±0.12to32.92±0.04(P<0.05); thepercentage of G2/M phase decreased significantly, by13.32±0.25to9.43±0.11,statisticallysignificant differences (P<0.01).The apoptosis rate increased from2.03±0.22to7.35±0.41(P <0.01).3. Cell clone analysis demonstrated that MCF-7R had greater SF2(survivalfractionafter2Gy irradiation, increased by34%, P<0.001)、Dq(2.261to3.695, P<0.05) andDo(1.215to1.834, P<0.05).4. Western blot show the expression of pAkt and HIF-1α were higher in MCF-7R thanin MCF-7(P<0.05); MCF-7R+6Gy express pAkt and HIF-1α higher than in MCF-7、MCF-7R and MCF-7+6Gy (P <0.01); there was no significance differences in MCF-7andMCF-7+6Gy (P>0.05).Conclusion:1. The method of radiating cells step by step and repeatedly is viable to establishradio-resistant breast cancer cell line-MCF-7R.2. The mechanisms of radioresisitance in breast cancer is associated with the PI3K/Aktpathway, and possibly through the downstream effector HIF-1α of PI3K/Akt pathway.