18F-FLT摄取与肺癌细胞增殖的相关性

背景与目的:近年来,3′-脱氧-3′-18F-氟代胸苷(3′-deoxy-3′-18F-fluoro-thymidine,18F-FLT)被认为是反映肿瘤细胞增殖的新的PET(positronemissiontomography)示踪剂。本实验旨在研究18F-FLT在荷肺癌小鼠的生物分布和PET显像,并探讨18F-FLT摄取与肺癌细胞增殖的相关性。方法:48只荷肺腺癌T739小鼠根据示踪剂不同被随机分为18F-FLT组和18F-氟代脱氧葡萄糖(2-18F-fluoro-2-deoxy-D-glucose,18F-FDG)组两组,各组再分为3组(每组8只):(A)对照组;(B)治疗后1天组;(C)治疗后2天组。治疗组采用顺铂进行治疗。所有小鼠经尾静脉注入18F-FLT或18F-FDG,注药后60min用井型探测仪测量小鼠18F-FLT和18F-FDG的生物分布,并行PET显像。肿瘤增殖判定采用免疫组化测定增殖细胞核抗原(proliferatingcellnuclearantigen,PCNA)。结果:在两组对照组中,两种示踪剂的肿瘤PET显像均很清晰。生物分布研究显示肿瘤均有大量放射性摄取,肿瘤在血液、肌肉和肺的T/NT比值均>2.0。18F-FLT组顺铂治疗后肿瘤PCNA阳性率明显减低A组(90.3±3.9)%ID/g,B组(65.5±9.2)%ID/g,C组(47.7±7.2)%ID/g],18F-FDG组同样明显减低A组(91.2±3.5)%ID/g,B组(67.8±8.2)%ID/g,C组(45.9±9.1)%ID/g]。治疗后肿瘤18F-FLT摄取快速降低A组(1.25±0.19)%ID/g,B组(0.82±0.19)%ID/g,C组(0.37±0.17)%ID/g],较18F-FDG摄取变化明显A组(8.83±1.73)%ID/g,B组(7.88±1.78)%ID/g,C组(7.45±1.67)%ID/g]。PET显像证实B组和C组较A组肿瘤部位18F-FLT放射性浓聚减低。PCNA阳性率与肿瘤18F-FLT摄取呈显著相关性(r=0.930,P<0.001),而与18F-FDG摄取无相关性(r=-0.136,P=0.538)。结论:肺恶性肿瘤组织中18F-FLT摄取高于正常组织,通过PET能清楚显示肺恶性肿瘤;肿瘤18F-FLT摄取与PCNA阳性率的相关性较18F-FDG显著。18F-FLT是一种可反映肺癌细胞增殖的PET示踪剂。

Correlation of 3'-deoxy-3'-18F-fluorothymidine uptake to cell proliferation in lung carcinoma xenografts

BACKGROUND & OBJECTIVE: 3'-Deoxy-3'-(18)F-fluorothymidine ((18)F-FLT) has been described recently as a new positron emission tomography (PET) tracer for imaging tumor cell proliferation. This study was to investigate the biodistribution and PET imaging of (18)F-FLT in a murine model of lung cancer, and to explore the correlation of (18)F-FLT uptake to cell proliferation of lung cancer. METHODS: A total of 48 T739 mice bearing lung adeno-carcinoma were randomized into (18)F-FLT group and 2-(18)F-fluoro-2-deoxy-D-glucose ((18)F-FDG) group according to the radioactive tracers. Each group was also divided into 3 subgroups: (A) untreated controls, (B) 1 day after treatment of cisplatin, (C) 2 days after treatment of cisplatin. Each subgroup contained 8 mice. All mice were injected with (18)F-FLT or (18)F-FDG through the tail veins. The biodistribution of (18)F-FLT and (18)F-FDG in tumor tissue was measured with well-gamma detector 60 min after injection; the PET imaging of mice was performed. Tumor cell proliferation was determined by immunohistochemical examination of proliferating cell nuclear antigen (PCNA). RESULTS: In both subgroups A, the PET images of the tracers in tumor were clear. Considerable radioactive uptake of tumor was observed; the T/NT ratios of tumor/blood, tumor/muscle and tumor/lung were all above 2.0. The positive rate of PCNA was reduced significantly in (18)F-FLT group after treatment of cisplatin (90.3+/-3.9)% (A) vs. (65.5+/-9.2)% (B) and (47.4+/-7.2)% (C), P<0.01], and in (18)F-FDG group (91.2+/-3.5)% (A) vs. (67.8+/-8.2)% (B) and (45.9+/-9.1)% (C), P<0.01]. Tumor uptake of (18)F-FLT was decreased rapidly after treatment (1.25+/-0.19) %ID/g (A) vs. (0.82+/-0.19) %ID/g (B) and (0.37+/-0.17) %ID/g (C), P<0.01]; tumor uptake of (18)F-FDG was decreased slightly after treatment (8.83+/-1.73)%ID/g (A) vs. (7.88+/-1.78)% ID/g (B) and (7.45+/-1.67)%ID/g (C), P>0.05]. The PET imaging confirmed that tumor (18)F-FLT retention was suppressed after treatment. Tumor uptake of (18)F-FLT was correlated to the positive rate of PCNA (r=0.930, P<0.001), but tumor uptake of (18)F-FDG did not (r=-0.136, P=0.538). CONCLUSIONS: The uptake of (18)F-FLT in lung malignant tissues is higher than that in normal tissues, therefore, the tumor could be imaged clearly with PET. The correlation of tumor uptake of (18)F-FLT to PCNA expression is more obvious than that of (18)F-FDG. (18)F-FLT is a promising PET tracer for reflecting cell proliferation in lung carcinoma.