微型PET及其在医药研究中的应用

由于基因表达和基因治疗方面的需要 ,使得分子显像尤为重要。PET是分子显像技术的一种 ,可用于发现、研究和早期诊断疾病 ,测定心肌活力 ,发现早期肿瘤 ,鉴别良恶性病变 ,判定肿瘤有无转移及监测疗效。而临床使用的PET系统对小动物研究分辨率不够 ,这促使人们开发了专用的微型PET。一、微型PET技术上的改进微型PET仪使用了新的技术 ,使得分辨率大大提高 ,在小鼠、大鼠、猴和人活体分子显像方面具有相似的显像能力。Chatziioannou等[1 ] 开发的微型PETⅠ应用了单个晶体光纤读出技术以及新的闪烁材料硅酸镥 (lutetiumoxyorthosili cat…     

PET报告基因显像研究进展

近20年的基因研究已经取得了很多研究成果,使基因治疗从实验室走向临床治疗成为可能。然而体内基因表达的监测仍有许多至关重要的问题没有解决,随着技术的发展,利用特定的报告基因和报告探针行PET显像,去推测基因在体内的表达成为可能。通过PET,不但能够正确理解基因治疗的过程,也为基因治疗的发展和用于临床提供了依据。     

PET报告基因显像研究进展

近20年的基因研究已经取得了很多研究成果,使基因治疗从实验室走向临床治疗成为可能.然而体内基因表达的监测仍有许多至关重要的问题没有解决,随着技术的发展,利用特定的报告基因和报告探针行PET显像,去推测基因在体内的表达成为可能.通过PET,不但能够正确理解基因治疗的过程,也为基因治疗的发展和用于临床提供了依据.     

动物PET研究进展

分子医学研究需要在活体实验动物上观察分子水平的生物学过程,因而正电子发射体层(PET)显像作为目前最成熟的分子显像方法,正被越来越多地用于动物实验。新开发的实验动物专用PET扫描仪的各项性能也逐步趋于完善。该技术将在疾病研究、新药开发、基因治疗等领域发挥重要作用。     

正电子断层显像的特点和临床应用价值

正电子断层显像(Positron Emission Tomography,PET)是一种非创伤性显像技术,在很多情况下,它可提供其它方法所不能提供的重要诊断信息。当进行这种显像时,将     

动物PET研究进展

分子医学研究需要在活体实验动物上观察分子水平的生物学过程，因而正电子发射体层（PET）显像作为目前最成熟的分子显像方法，正被直来越多地用于动物实验。新开发的实验动物专用PET扫描仪的各项性能也逐步趋于完善。该技术将在疾病研究、新药开发、基因治疗等领域发挥重要作用。     

18F-FDG PET/CT显像用于肺癌诊疗的研究进展

常规¹⁸F-FDG PET/CT静态显像在肺癌的诊断、分期、疗效评估等方面发挥了重要作用,并能通过标准化摄取值等代谢参数进行半定量分析,但静态显像无法提供病变的示踪动力学信息。近年出现的动态显像技术能够连续评估某一时间段内病变的代谢变化过程,并可应用净摄取速率常数等动力学参数进行定量分析,与静态显像相互补充,为肺癌的诊断提供更丰富的信息。就 ¹⁸F-FDG PET/CT静态及动态显像在肺癌诊疗中的研究进展进行综述。     

^18F-脱氧胸苷PET显像在肺癌中的应用进展

PET显像是先进的分子影像技术。目前，^18F-FDG PET显像已成为肺癌诊断及分期的重要手段。然而，^18F-FDG仅反映体内葡萄糖代谢，为非肿瘤特异性显像剂，其也可在炎性结节中积聚。     

基因表达正电子发射断层显像

分子生物学与核医学的结合形成了分子核医学,基因表达正电子发射断层(PET)显像是当今分子核医学研究的热点和前沿领域之一。基因表达PET显像包括反义PET显像和报告基因PET显像,反义PET显像由于技术上的问题,远不如报告基因PET显像那样发展迅速,报告基因PET显像已广泛用于动物实验研究,可望不久的将来会用于临床研究。     

PET显像多层面容积重建显示技术的建立及临床应用

目的　建立可在PC机上运行的PET显像容积数据最大密度投影法 (MIP)和平均密度投影法 (AIP)多层面容积重建显示软件 ,并用于临床。方法　在PC机上 ,对1 3N NH3、1 8F 脱氧葡萄糖(FDG)PET显像原始三维容积数据 ,经归一化数据转换、三维几何和观察变换、透视变换等步骤 ,生成MIP或AIP投影图像 ,透视变换采用平行投影透视法。结果　最终的PET显像三维容积数据多层面容积重建显示程序具有灵活的交互式图形用户界面 ,可在PC机上运行 ,可生成PET显像三维容积数据多角度多方位的MIP或AIP投影图像 ;对心脏、垂体、肾脏等器官动态1 3N NH3或1 8F FDGPET显像 ,可多角度多方位投影图像 ,直观、整体显示血流灌注相靶器官及周围大血管和血池。结论　建立的PET显像三维容积数据多层面容积重建显示技术可多角度多方位直观、整体显示血流灌注相靶器官及周围大血管和血池 ,有一定的临床应用前景。     

Reporter gene imaging: potential impact on therapy

Positron emission tomography (PET)-based molecular-genetic imaging in living organisms has enjoyed exceptional growth over the past 5 years; this is particularly striking since it has been identified as a new discipline only within the past decade. Positron emission tomography is one of three imaging technologies (nuclear, magnetic resonance and optical) that has begun to incorporate methods that are established in molecular and cell biology research. The convergence of these disciplines and the wider application of multi-modality imaging are at the heart of this success story. Most current molecular-genetic imaging strategies are "indirect," coupling a "reporter gene" with a complimentary "reporter probe." Reporter gene constructs can be driven by constitutive promoter elements and used to monitor gene therapy vectors and the efficacy of trans gene targeting and transduction, as well as to monitor adoptive cell-based therapies. Inducible promoters can be used as "sensors" to regulate the magnitude of reporter gene expression and can be used to provide information about endogenous cell processes. Reporter systems can also be constructed to monitor mRNA stabilization and specific protein-protein interactions. Promoters can be cell specific and restrict transgene expression to certain tissue and organs. The translation of reporter gene imaging to specific clinical applications is discussed. Several examples that have potential for patient imaging studies in the near future include monitoring adenoviral-based gene therapy, oncolytic herpes virus therapy, adoptive cell-based therapies and Salmonella-based tumor-targeted cancer therapy and imaging. The primary translational applications of noninvasive in vivo reporter gene imaging are likely to be (a) quantitative monitoring of the gene therapy vector and the efficacy of transduction in clinical protocols, by imaging the location, extent and duration of transgene expression; (b) monitoring cell trafficking, targeting, replication and activation in adoptive therapies, involving ex vivo transduction of harvested immune-competent cells and stem/progenitor cells; (c) assessments of endogenous molecular events using different reporter gene imaging technologies following the development of safe, efficient and target-specific vectors for "diagnostic transductions."     

The human norepinephrine transporter in combination with 11C-m-hydroxyephedrine as a reporter gene/reporter probe for PET of gene therapy.

Although the herpes simplex virus thymidine kinase gene has been frequently applied as a reporter gene for monitoring gene transfection in animals, it has some intrinsic limitations for use in humans. In our search for a reporter gene that lacks these limitations, we have evaluated the feasibility of the human norepinephrine transporter (hNET) as a reporter gene in combination with the reporter probe 11C-m-hydroxyephedrine (mHED) for PET. METHODS: An adenoviral vector (AdTrack-hNET) containing the hNET gene as reporter gene and the enhanced green fluorescent protein (EGFP) as a substitute for a therapeutic gene was constructed. After COS-7, A2780, and U373 cells were transiently transduced with AdTrack-hNET, hNET protein expression, EGFP fluorescence, and cellular uptake of 11C-mHED were determined. In rats, U373 tumor xenografts were grown and transiently transduced with either AdTrack-hNET or an AdTrack-Luc control adenovirus. Intratumoral accumulation of 11C-mHED was determined by PET and ex vivo biodistribution. The tumors were subsequently examined for EGFP fluorescence. RESULTS: 11C-mHED uptake was positively correlated with AdTrack-hNET viral titer and hNET protein expression. However, large differences in transfection efficiency between cell lines were observed. The highest 11C-mHED uptake was found in hNET transfected U373 cells, in which tracer uptake was >70-fold higher than that in control cells. 11C-mHED accumulation could be inhibited by desipramine, a potent inhibitor of hNET. In all cell lines, 11C-mHED uptake was positively correlated with EGFP fluorescence, implying that imaging of hNET with 11C-mHED would enable monitoring of a coexpressed therapeutic gene. In the animal model, gene transfection efficiencies were very low, as determined by EGFP fluorescence. Still, a significantly higher 11C-mHED uptake in hNET transduced tumors than that in control tumors was demonstrated by ex vivo biodistribution studies. PET with a clinical camera could visualize 1 of 3 hNET transduced tumors, indicating that the transfection efficiency was near the detection limit. CONCLUSION: These results indicate that monitoring of gene therapy using the hNET/11C-mHED reporter gene/probe is feasible, but further investigation with regard to the sensitivity of the technique is required.     

报告基因显像监测基因治疗研究进展

为评价基因治疗,需要随时对治疗基因的定位和表达进行监测。放射性核素报告基因技术是检测基因表达的最好方法。用基因融合、双顺反子、双启动子及双向转录等重组技术,构建表达报告基因的腺病毒载体,导入靶细胞或组织内,然后注射与报告基因偶合的核素标记的探针,进行PET、SPECT或γ-照相,可无创伤地、重复地定量显示报告基因表达。目前,用于基因治疗的报告基因和报告探针系统有:HSV1-tk(单纯疱疹病毒胸腺嘧啶核苷激酶基因)和碘、氟同位素标记的尿嘧啶、鸟嘌呤的衍生物;突变的多巴胺D₂R(多巴胺2型受体)基因和(18F-FESP(18F-氟乙基螺环哌丁苯);SSTr2(生长抑素2型受体基因)和生长抑素类似物等。其中,部分已用于临床试验治疗。     

Assays for noninvasive imaging of reporter gene expression.

Repeated, noninvasive imaging of reporter gene expression is emerging as a valuable tool for monitoring the expression of genes in animals and humans. Monitoring of organ/cell transplantation in living animals and humans, and the assessment of environmental, behavioral, and pharmacologic modulation of gene expression in transgenic animals should soon be possible. The earliest clinical application is likely to be monitoring human gene therapy in tumors transduced with the herpes simplex virus type 1 thymidine kinase (HSV1-tk) suicide gene. Several candidate assays for imaging reporter gene expression have been studied, utilizing cytosine deaminase (CD), HSV1-tk, and dopamine 2 receptor (D2R) as reporter genes. For the HSV1-tk reporter gene, both uracil nucleoside derivatives (e.g., 5-iodo-2'-fluoro-2'-deoxy-1-beta-D-arabinofuranosyl-5-iodouracil [FIAU] labeled with 124I, 131I) and acycloguanosine derivatives [e.g., 8-[18F]fluoro-9-[[2-hydroxy-1-(hydroxymethyl)ethoxy]methyl]guanine (8-[18F]-fluoroganciclovir) ([18F]FGCV), 9-[(3-[18F]fluoro-1-hydroxy-2-propoxy)methyl]guanine ([18F]FHPG)] have been investigated as reporter probes. For the D2R reporter gene, a derivative of spiperone [3-(2'-[18F]-Fluoroethyl)spiperone ([18F]FESP)] has been used with positron emission tomography (PET) imaging. In this review, the principles and specific assays for imaging reporter gene expression are presented and discussed. Specific examples utilizing adenoviral-mediated delivery of a reporter gene as well as tumors expressing reporter genes are discussed.     

Radionuclide reporter gene imaging for cardiac gene therapy

INTRODUCTION: In the field of cardiac gene therapy, angiogenic gene therapy has been most extensively investigated. The first clinical trial of cardiac angiogenic gene therapy was reported in 1998, and at the peak, more than 20 clinical trial protocols were under evaluation. However, most trials have ceased owing to the lack of decisive proof of therapeutic effects and the potential risks of viral vectors. In order to further advance cardiac angiogenic gene therapy, remaining open issues need to be resolved: there needs to be improvement of gene transfer methods, regulation of gene expression, development of much safer vectors and optimisation of therapeutic genes. For these purposes, imaging of gene expression in living organisms is of great importance. In radionuclide reporter gene imaging, "reporter genes" transferred into cell nuclei encode for a protein that retains a complementary "reporter probe" of a positron or single-photon emitter; thus expression of the reporter genes can be imaged with positron emission tomography or single-photon emission computed tomography. Accordingly, in the setting of gene therapy, the location, magnitude and duration of the therapeutic gene co-expression with the reporter genes can be monitored non-invasively. In the near future, gene therapy may evolve into combination therapy with stem/progenitor cell transplantation, so-called cell-based gene therapy or gene-modified cell therapy. CONCLUSION: Radionuclide reporter gene imaging is now expected to contribute in providing evidence on the usefulness of this novel therapeutic approach, as well as in investigating the molecular mechanisms underlying neovascularisation and safety issues relevant to further progress in conventional gene therapy.     

Human reporter genes: potential use in clinical studies

The clinical application of positron-emission-tomography-based reporter gene imaging will expand over the next several years. The translation of reporter gene imaging technology into clinical applications is the focus of this review, with emphasis on the development and use of human reporter genes. Human reporter genes will play an increasingly more important role in this development, and it is likely that one or more reporter systems (human gene and complimentary radiopharmaceutical) will take leading roles. Three classes of human reporter genes are discussed and compared: receptors, transporters and enzymes. Examples of highly expressed cell membrane receptors include specific membrane somatostatin receptors (hSSTrs). The transporter group includes the sodium iodide symporter (hNIS) and the norepinephrine transporter (hNET). The endogenous enzyme classification includes human mitochondrial thymidine kinase 2 (hTK2). In addition, we also discuss the nonhuman dopamine 2 receptor and two viral reporter genes, the wild-type herpes simplex virus 1 thymidine kinase (HSV1-tk) gene and the HSV1-tk mutant (HSV1-sr39tk). Initial applications of reporter gene imaging in patients will be developed within two different clinical disciplines: (a) gene therapy and (b) adoptive cell-based therapies. These studies will benefit from the availability of efficient human reporter systems that can provide critical monitoring information for adenoviral-based, retroviral-based and lenteviral-based gene therapies, oncolytic bacterial and viral therapies, and adoptive cell-based therapies. Translational applications of noninvasive in vivo reporter gene imaging are likely to include: (a) quantitative monitoring of gene therapy vectors for targeting and transduction efficacy in clinical protocols by imaging the location, extent and duration of transgene expression; (b) monitoring of cell trafficking, targeting, replication and activation in adoptive T-cell and stem/progenitor cell therapies; (c) and assessments of endogenous molecular events using different inducible reporter gene imaging systems.     

18F-FDG-PET/MRI in lymphoma patients

The introduction of hybrid PET/MRI imaging using integrated systems into clinical practice has opened up the possibility of reducing the radiation dose from hybrid imaging by eliminating the contribution from computed tomography. Studies comparing the possibilities of PET/CT and PET/MRI imaging demonstrated it is possible to use the advantages of the high contrast resolution of magnetic resonance for soft tissue and bone marrow along with PET records in a quality comparable to PET/CT imaging. The significant feature for PET imaging in Hodgkińs lymphoma is that it is a tissue with high levels of radiopharmaceutical accumulation, which decreases proportionally after successful therapeutic effect, the effect of therapy is assessed using Deauville score system on interim examinations. While the efficacy of prognosis determined using the Deauville scale in HL is widely accepted, it turns out that in DLBCL, the prognostic value of PET imaging is bound to the evaluation of subtypes. PET/MRI scanning can be used to evaluate a relapse if follicular lymphoma has already been treated, or to confirm transformation into more aggressive forms. In children and adults with Burkitt's lymphoma, negative findings after induction therapy have a high negative predictive value for relapse prognosis.     

分子影像报告基因系统的研究进展

分子影像报告基因系统的应用使基因治疗从实验阶段逐渐走向了临床应用,为无创性监测治疗基因的表达及进行定量分析提供了方法学技术.目前研究最多、最成熟的仍是放射性核素报告基因系统,近年来磁共振报告基因系统和光学报告基因系统的兴起和发展,极大地丰富和完善了分子影像报告基因系统的内容,并且在与应用化学和分子生物学等多学科交叉合作的基础上,涌现出了很多新型的修饰或改良的报告基因和分子探针.该文主要概述各类报告基因系统的优缺点和发展趋势.