Notch信号通路小分子抑制剂DAPT的11C标记及在正常兔体内的初步动态显像研究

目的研究正电子核素11C标记Notch通路抑制剂（3,5-二氟苯乙酰基)-L-丙氨酰基-S-苯基甘氨酸叔丁酯（DAPT）的制备方法，并进行正常兔PET/CT的初步动态显像。方法采用细胞计数Kit-8法检测不同浓度DAPT和CH₃-DAPT对人胰腺癌细胞株MiaPaCa-2增殖的影响，并计算半抑制浓度（IC₅₀）。以DAPT为前体，使用全自动合成仪进行合成，得到产物11C-N-甲基-DAPT(简称11C-DAPT)，并用高效液相色谱（HPLC）仪进行分离纯化。正常新西兰兔静脉注射125.8 MBq（3.4 mCi）11C-DAPT后，用PET/CT进行全身动态扫描。在不同器官勾画感兴趣区，测量放射性浓度随时间的动态变化。结果DAPT和CH₃-DAPT均可抑制人胰腺癌MiaPaCa-2细胞的增殖，呈浓度依赖关系，72 h的IC₅₀分别为64.2、180.0 μmol/L。11C-DAPT合成过程大约30 min，未校正放射化学产率为25%～35%，放射化学纯度>95%。11C-DAPT主要经肾脏排泄，全身脏器中肾脏摄取最高，肝脏、肠道、肺和脑摄取低。静脉注射后7 min肝脏、肾脏摄取达到高峰，28 min后降低>50%。结论11C-DAPT的合成过程简便、快速，放射化学纯度高。PET/CT的初步显像为进一步探索11C-DAPT作为胰腺癌新型靶向分子探针奠定了基础。

11C-labeling DAPT a small-molecular inhibitor of the Notch signaling pathway,and preliminary imaging study of dynamic distribution in a normal rabbit

ObjectiveTo label N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester(DAPT), an inhibitor of the Notch signaling pathway, with 11C and perform preliminarily dynamic imaging in normal rabbit.MethodsProliferation of human pancreatic cancer cell line MiaPaCa-2 were assessed by cell counting kit-8 method after treatment with various concentrations of DAPT and CH₃-DAPT. Half-maximal inhibitory concentration(IC₅₀) was calculated. DAPT was then used as a precursor to prepare 11C-N-methyl-DAPT(11C-DAPT) with a fully automatic synthesizer. The final product was purified through semipreparative high performance liquid chromatography(HPLC). After intravenous injection of 125.8 MBq(3.4 mCi) 11C-DAPT, a normal New Zealand rabbit was subjected to dynamic whole-body PET/CT scanning. The dynamic changes in radioactivity were measured by drawing regions of interest over different organs.ResultsDAPT and CH₃-DAPT concentration-dependently inhibited the growth of the human pancreatic cancer cell line MiaPaCa-2. The IC₅₀ values were 64.2 and 180.0 μmol/L at 72 h after administration, respectively. 11C-DAPT was synthesized for approximately 30 min. The uncorrected radiochemical yield was 25%–35%. Radiochemical purity was above 95%. 11C-DAPT was mainly excreted through the kidney, the highest uptake was in the kidneys, and the uptake in the liver, intestine, lung, and brain was relatively low. The tracer uptake in the kidneys and liver peaked at 7 min after injection and decreased to >50% at 28 min.Conclusions11C-DAPT can be easily and rapidly synthesized with high radiochemical purity. Preliminary PET/CT imaging can lay a foundation for further investigating 11C-DAPT as a novel molecular probe.