Experimental Study Of Predicting Tumor Radiosensitivity With¹⁸F-FLT PET

Objective:To research the value of18F-FLT PET imaging for early predicting radiosensitivity of tumor cells and xenografts in human breast cancer cell line MB-MDA-231and human glioma cell line LN229.Methods:The experiment divides two parts. Part I:(1) The change of tumor cell morphous and numbers of human breast cancer cell line MB-MDA-231and human glioma cell line LN229were observed at24hour、48hour and72hour respectively after radiotherapy with0Gy、8Gy and16Gy by using optical microscope.(2) The change of tumor cell porghous、numbers and apoptosis in the two cell lines were measured24hour after irradiation with0Gy、8Gy and16Gy by using fluorescence microscope.(3) The change of cell cycle distribution of the two cell lines were observed at24hour and48hour respectively after radiotherapy with0Gy、8Gy and16Gy by using flow cytometry.(4) The cell growth rate of the two cell lines were measured at24hou、48hour and72hour respectively after radiotherapy with0Gy、8Gy and16Gy by MTT method.(5) Expression of TK-1were analyzed following irradiation with0Gy、8Gy and16Gy by Western blot.(6) The colony forming efficiency of the two cell lines were analyzed following irradiation with OGy、8Gy and16Gy.(7)The difference of uptake of18F-FLT in two cell lines were determined at24hour、48hour and72hour respectively after radiotherapy with OGy、8Gy and16Gy by using γ well-type survey meter; correlate analysis were conducted between the cell uptake of18F-FLT48hour after radiotherapy and the survival fraction. Part II:(1) The expression of TK-1in the two cell lines were determined at1day、3day and7day respectively after radiotherapy with OGy、8Gy and16Gy by using immunohistochemistry.(2) The difference of T/NT value were analyzed at1day、3day and7day respectively after radiotherapy with0Gy、8Gy and16Gy by using18F-FLT PET imaging; correlate analysis were conducted between T/NT value and TK-1expression in the two cell lines.Results:Part I:(1) After radiotherapy, the numbers of survival tumor cells decreased, dead cells and apoptosis of the two cell lines increased. By contrast, the change in human breast cancer cell line MB-MDA-231was more apparent than in human glioma cell line LN229under the same treatment.(2) The human breast cancer cell line MB-MDA-231has higher inhibition ratio of tumor cells and lower growth ratio of cell apoptosis with Hoechst33342. Mito-Tracker Red and Yo-Pro-1staining.(3) The two groups have no apparent different of G2/M arrest at24hour following irradiation with8Gy, and the human breast cancer cell line MB-MDA-231has apparent G2/M arrest at48hour after radiotherapy.(4) The inhibition ratio was lower in the human breast cancer cell line MB-MDA-231at24hour and48hour following irradiation and increased gradually and exceeded that in the human glioma cell line LN229at72hour after irradiation.(5) There is no apparent difference of TK-1expression between the two groups after irradiation with8Gy, and the TK-1expression of the human breast cancer cell line MB-MDA-231was lower with radiation dose of16Gy.(6) The cell survival fraction of the human breast cancer cell line MB-MDA-231decreased apparently, and has statistic difference.(7) The uptake of18F-FLT of the two groups increased slowly at the beginning of48hour after irradiation, and it began to decrease in the human breast cancer cell line MB-MDA-231at48hour after irradiation. The uptake of18F-FLT48hour following irradiation was correlated with survival fraction,(p<0.05). Part Ⅱ:The T/NT value of the human breast cancer cell line MB-MDA-231decreased at first, then increase gradually from24hour following radiotherapy; and that of glioma cell line LN229increased at24hour after radiotherapy and decreased gradually. The change of T/NT value was correlated with Tk-1expression and has statistic difference,(p<0.05).Conclusions:(1) Laboratory test show that the human breast cancer cell line MB-MDA-231has more radiosensitivity than the human glioma cell line LN229.(2) The uptake of18F-FLT of the two groups correlate with cell survival fraction.(3) The change of T/NT value correlates with TK-1expression.(4) Elementary results show that18F-FLT PET imaging can predict tumor radiosensitivity, and further clinical trials are needed.