GLUT1/MDR1基因多态性和启动子甲基化对非小细胞肺癌患者18F-FDG 摄取的影响及其机制

18F-fluorodeoxyglucose (18F-FDG) -positron emission tomography with computed tomography（PET/CT） becomes the best method for early diagnosis in non-small cell lung cancer(NSCLC), However, the misdiagnosis were existed in the diagnosis of NSCLC by 18F-FDG PET/CT, and the mechanism is not clear completely. GLUT1 and P-glycoprotein (P-gp) are two key enzymes in transporting 18F-FDG into and out of cells, and the uptake of 18F-FDG is related to the expression of GLUT1 or P-gp in cancer cells. Recently, researches show that the genetic polymorphism and methylation can affect the expression of protein. Moreover, it has been reported that the single nucleotide polymorphism of the class I transporters (GLUT1) is associated with the uptake of 18F-FDG. So we hypothesized the genetic polymorphisms and methylation of GLUT1 and MDR1 may affect the uptake of 18F-FDG in NSCLC patients. In the present study, we are to detect the single nucleotide polymorphisms and methylation of GLUT1 and MDR1 gene, in NSCLC patients who prospectively receive PET/CT scan. Our aim is to explore the impact of GLUT1 and MDR1 genetic polymorphisms and methylation on the uptake of 18F-FDG in NSCLC patients. Furthermore, we assayed for GLUT1 and MDR1 gene mRNA and protein expression levels in NSCLC tissue. We introduced the plasmid which carrying different polymorphisms of GLUT1 and MDR1 gene into HEK293T cell line. We compared the difference of transcription level, protein expression level and the transport capability among the different cells. In addition, by primary culture, we build different cell lines from NSCLC patients which GLUT1 and MDR1 gene are different. We detect the uptake rate of 18F-FDG in the different cell lines isolated from NSCLC patients. This study is to investigate the the effect of genetic polymorphisms and methylation on the uptake of 18F-FDG in NSCLC patients, and has the ultimate objective of elucidation the molecular mechanism that the difference of the uptake of 18F-FDG in NSCLC patients. It provides a theoretical foundation for explain the misdiagnosis of 18F-FDG PET/CT, and may be used for elevating the accurate of 18F-FDG PET/CT according to the gene type of the patients.

18F-FDG PET/CT在非小细胞肺癌（NSCLC）的早期诊断中起重要作用，但存在明显误诊，且机制尚未完全明确。GLUT1和P-gp是介导18F-FDG进、出细胞的主要转运体，其表达与18F-FDG的摄取相关。近期研究表明基因多态性和启动子甲基化可影响蛋白的表达或活性，且已发现GLUT1基因多态性影响肿瘤对18F-FDG的摄取，因而我们推测GLUT1和P-gp编码基因的多态性及启动子甲基化也影响NSCLC对18F-FDG的摄取。本项目拟研究GLUT1/MDR1基因多态性及启动子甲基化对NSCLC患者18F-FDG 摄取的影响；从组织水平探讨其与mRNA和蛋白表达水平的相关性；从细胞水平考察GLUT1和MDR1基因多态性对其转录活性、蛋白表达和摄取18F-FDG功能的影响。以期揭示遗传因素对PET/CT显像的影响及其机制，为临床解释PET/CT误诊现象及结合基因特性提高诊断率提供实验依据

GLUT1和P-gp介导PET/CT显像剂18F-FDG进、出细胞，其编码基因的多态性和甲基化可通过改变转运体Glut1和P-gp的表达或活性，而影响细胞对18F-FDG的摄取，最终使PET/CT显像受到影响。本项目以术前行18F-FDG PET/CT检查的非小细胞肺癌患者为对象，考察在排除临床因素情况下，GLUT1和MDR1基因多态性或启动子甲基化对18F-FDG摄取的影响；采用实时荧光定量PCR检测GLUT1和MDR1基因的mRNA表达水平，采用Western-blotting方法检测癌组织中GLUT1和MDR1的蛋白表达水平，比较不同基因型患者癌组织中mRNA和蛋白表达水平的差异，分析基因多态性和甲基化水平对基因mRNA和蛋白表达水平的影响；将不同基因型患者的细胞原代培养，检测携带不同基因型细胞对18F-FDG摄取率的差异。结果显示GLUT1 -2841A>T多态性与18F-FDG的摄取相关，但GLUT1 -2841A>T多态性不影响其mRNA和蛋白的表达，且原代培养的三种基因型细胞对18F-FDG的摄取率亦无显著性差异，提示GLUT1 -2841A>T多态性影响非小细胞肺癌患者18F-FDG摄取的机制需要进一步探讨。GLUT1受试CpG位点甲基化不影响非小细胞肺癌患者肿瘤细胞对18F-FDG的摄取，且与GLUT1基因mRNA和蛋白的表达无相关性。MDR1基因多态性及其甲基化均不影响非小细胞肺癌肿瘤细胞对18F-FDG的摄取。综合上述结果，本研究揭示GLUT1基因多态性影响18F-FDG的摄取，为临床进行PET/CT诊断提供参考因素，同时为探讨GLUT1和MDR1基因多态性或甲基化对其蛋白表达或活性影响提供试验依据。项目资助发表核心论文2篇，待发表SCI论文2篇。资助在读研究生1名。国际会议大会发言1次。