肺腺癌靶向基因放射治疗的体内研究及小动物正电子发射计算机体层摄影评价疗效的可行性

Gene-targeted radiation therapy mediated by radiation-sensitive promoter in lung adenocarcinoma and the feasibility of micro-PET/CT in evaluation of therapeutic effectiveness in small animals

目的探讨靶向基因放射治疗在裸鼠肺腺癌模型中的联合抗肿瘤作用，以及应用小动物正电子发射计算机体层摄影（Micro-PET-CT）动态评价疗效的可行性。方法建立肺腺癌A549裸鼠模型，并分为重组杆状病毒联合放疗组（即重组杆状病毒瘤内注射＋放疗组、重组杆状病毒尾静脉内注射＋放疗组、重组杆状病毒肌内注射＋放疗组）、单纯放疗组和对照组，计算其肿瘤生长抑制率和肿瘤生长延缓时间。采用Micro-PET-CT动态评价^18F-FDG代谢变化，采用免疫组化法检测肿瘤组织中血管内皮生长因子（VEGF）、CD31和Ki-67的表达情况。结果重组杆状病毒联合放疗组的肿瘤生长延缓时间〉12d，肿瘤抑制率〉45％，高于单纯放疗组（P〈0．05）。免疫组化结果显示，重组杆状病毒联合放疗组的VEGF、CD31和Ki-67表达显著低于单纯放疗组和对照组（P〈0．05）。Micro-PET-CT显像显示，重组杆状病毒联合放疗组的肿瘤最大标准摄取值（SUVmax）较对照组和单纯放疗组明显降低（P〈0．05），且重组杆状病毒瘤内注射＋放疗组、重组杆状病毒尾静脉内注射＋放疗组、重组杆状病毒肌内注射＋放疗组和单纯放疗组裸鼠治疗后肿瘤体积与SUVmax正相关（r分别为0．976、0．954、0．929和0．871，P〈0．05）。结论重组杆状病毒BacEgr1-K5联合放疗增强了抑制肺腺癌生长的作用，Egr1启动子的射线可诱导性实现了治疗的靶向性及可控性。Micro-PET-CT显像结果与治疗效果相关性好，可用于活体肿瘤的功能评价。

Objective To explore the combined anti-tumor effect of radiation therapy and gene- targeted suppression of tumor neovasculature in lung adenocarcinoma in vivo, and to explore the feasibility of micro-PET/CT in dynamic evaluation of treatment effectiveness. Methods Thirty 5-6-week old male BALB/e nude mice were used in this study. The mouse models of xenotransplanted human lung adenocarcinoma were divided into 5 groups at random, six mice in each group： the control group, radiation treatment alone group and three groups of recombinant baculovirus plus radiation treatment （intratumoral injection, tail vein injection, and intramuscular injection）. The tumor volume was measured every 2 days. Growth delay time （GD） and growth inhibition rate was calculated. FDG metabolism was evaluated by micro-PET-CT before and after treatment. The expressions of VEGF, CD31 and Ki-67 were detected by immunohistochemistry （IHC）. Results The tumor growth delay was 〉 12 days, and the tumor inhibition rate was 〉45% in the recombinant baculovirus combined with radiotherapy groups, significantly higher than that of the radiotherapy alone group （ P 〈 0.05 ）. Immunohistochemical analysis showed that the expressions of VEGF, CD31 and Ki-67 were significantly lower than that in other groups （P 〈0.05）. The micro-PET- CT assessment showed that the FDG-metabolism in the recombinant baculovirus combined with radiotherapy groups was significantly reduced （ P 〈 0.05 ）, and the SUVmax （ FDG metabolism） of transplanted tumors after treatment was also markedly decreased in comparison with that of the control group. The tumor volume after treatment was significantly correlated with SUVmax in the recombinant baculovirus intratumoral injection ＋ radiotherapy group （ r = 0.976）, recombinant baculovirus intravenous injection ＋ radiotherapy group （ r= 0. 954 ）, recombinant baculovirus intramuscular injection ＋ radiotherapy group （r = 0. 929 ）, and radiotherapy alone group （ r = 0. 871, P 〈 0.05 ）. Conclusions The recombinant baculovirus containing Egrl promoter and K5 gene combined with radiotherapy enhances the suppressing effect on the growth of lung adenocarcinoma in the tumor-bearing nude mice. The inducibility of Egrl promoter by radiation allows the targeting and controllability of treatment. Micro-PET-CT results have a good correlation with the treatment effectiveness. Therefore, it can be used in real-time evaluation of tumor metabolic function in vivo.