The Research About Insulin Increasing The Radiosensitivity Of A549 Lung Adenocarcinoma Cells

Objective:To detect whether adding insulin before radiotherapy increase the radio- sensitivity of A549 lung Adenocarcinoma cells in vitro.Method:Divide A549 lung Adenocarcinoma cells in logarithmic growth phase into four groups.Cells in A group under normal growth.Cells in B group accept the exposure of insulin only.Cells in C group accept the exposure of X-ray only.Cells in D group accept the exposure of insulin and X-ray both.After these cells are exposed to insulin and(or) X-ray,we make use of methyl thiazolyl tetrazolium(MTT) and flow cytometry to observe survivorship of A549 lung Adenocarcinoma cells.Result:The results of MTT for these A549 lung adenocarcinoma cells in group B which are exposed to X-ray only and in group A which are under normal growth indicate that there is negative correlation between the OD value and the dose of radiotherapy(pearson correlation r= -0.920,P<0.01),which can indicate that there is negative correlation between the amount of cells and the dose of radiotherapy.When add insulin only to these cells in group C,the result of MTT indicate that there is no significant difference of the optical density(OD) value between cells in group C and cells in group A which under normal growth(P>0.05).The result is the same of the comparison between the amout of cells in group A and group C.Compared these cells in group C which accept insulin only with these cells in group D which accept insulin and the exposure of X-ray both,the OD value of cells in group C decrease,there is statistical significant of the difference between them(P<0.05),the amount of cell in the two group is different.Compared with the cells in group B which are exposed to X-ray only, insulin of some concentration rang from 2 mu/ml to 64 mu/ml can decrease the OD values of A549 lung Adenocarcinoma cells in group D which accept insulin of these concentration before the exposure of X-ray. Use the formula(1-OD value of experimental group/OD value of control group) to calculate the inhibition rate ,which of cells in group D increase.Detect the cells in group B and cells in group D of which insulin concentration is 4,8,16,32 mu/ml by folw cytometry, the result is that the rate of apoptosis in group D is higher than that in group B.The concentration of insulin added to these cells which has the highest apoptosis rate are 4 mu/ml and 8 mu/ml.These results indicate that the amout of cells in group D is less than that in group B,and the apoptosis is enhanced.There is statistical significant of the difference between these two groups(P<0.05).Conclusion:Insulin of different concentration can not promote the proliferation of A549 cells perpetually,insulin of some concentration rang from 2 mu/ml to 64 mu/ml can increase the radiosensitivity and promote apoptosis of A549 lung adenocarcinoma cells,the concentration of insulin with the most radiosensitization are 4 mu/ml and 8 mu/ml .These results could provide some underlaying evidence for the use of insulin as sensitizer of radiotherapy in clinical treatment.