肿瘤细胞特异性适配子筛选技术及其应用的研究进展

指数富集的配基系统进化技术(systematic evolution of ligands by exponential enrichment,SELEX)应用人工合成的随机寡核苷酸文库,通过筛选、分离、富集获得能与各种配体特异结合的寡核苷酸适配子(aptamer)。适配子能特异性结合多肽、蛋白质等多种靶分子,且具有高亲和力。细胞-SELEX技术在SELEX基础上发展起来,它以活细胞为基础,可以在对肿瘤细胞分子标志物一无所知的情况下有效地筛选出肿瘤细胞特异性适配子,是一个潜在的发现肿瘤细胞新标志物的理想策略。肿瘤细胞特异性适配子作为分子探针,在肿瘤基础研究、早期诊断,以及靶向治疗方面展示了巨大的应用前景。目前已筛选出淋巴细胞白血病、肝癌等多种肿瘤细胞的适配子,这些适配子已应用在肿瘤细胞检测,肿瘤早期发现、诊断、游离肿瘤细胞的分选和富集,以及肿瘤细胞靶向药物递送等方面,并且由于适配子适用范围广泛、易于修饰等特点,显示出良好的敏感性、特异性和其他独特的优越性。适配子在肿瘤研究中受到越来越多的关注,在肿瘤检测、诊断和治疗等方面发挥重要作用。     

c-Met靶向成像在肿瘤诊断中的应用

肝细胞生长因子受体(c-Met)是一种酪氨酸激酶型受体，对于肿瘤的发生发展至关重要，c-Met靶向治疗已初步应用于临床，其对于癌症患者的治疗具有显著的益处。目前，由于无法对c-Met表达阳性的肿瘤患者进行有效的早期筛选，使得c-Met靶向治疗在肿瘤治疗中总体有效率偏低。c-Met靶向分子成像借助靶向分子成像探针能够实现肿瘤c-Met表达水平及活化状态的定量检测和直观揭示，对于肿瘤的早期诊断、治疗和预后具有重要意义和巨大的潜在价值。结合近年来c-Met靶向分子成像的研究，本文将深入分析、探讨c-Met靶向分子成像探针的构建及其在肿瘤诊断中的应用。     

肿瘤坏死因子相关凋亡诱导配体及其受体与肝癌

肿瘤坏死因子相关凋亡诱导配体(TRAIL)及受体能在肝癌细胞中特异性地表达,并通过死亡受体特异性地诱导肿瘤细胞凋亡;TRAIL联合放疗、化疗能有效地克服肿瘤细胞的TRAIL耐受,促进肿瘤细胞凋亡,同时TRAIL的基因治疗在抗肿瘤临床治疗上已得到广泛的应用.     

功能化PSMA在前列腺癌核素靶向治疗中的研究进展

前列腺癌（PCa）是男性生殖系统发病率最高的恶性肿瘤。研究证实,前列腺特异性膜抗原（PSMA）是一种有效的前列腺癌诊疗靶点。治疗核素177Lu/90Y标记的抗PSMA小分子/多肽/单抗表现出重要的抑癌活性,但也产生腺体、骨髓的特异性摄取和肾脏的非特异性摄取带来的正常器官损伤。而且小分子/多肽易于经循环系统清除,基于小分子/多肽的放射性靶向治疗往往需要较高剂量或频繁给药,导致在抑制肿瘤的同时,也产生难以预料的器官毒性。放射性核素靶向治疗依赖于将放射性核素传递到肿瘤表达的受体,但配体与受体结合容量有限。为提高核素的使用效率,延长核素治疗型PSMA分子探针的体内代谢,增加靶/非靶比值,对PSMA分子探针进行功能化修饰以期改善药代动力学行为的研究已经取得了巨大进展。本文就近年功能化PSMA分子探针在前列腺癌核素靶向治疗中的临床转化及临床研究展开综述。     

全氟化碳类纳米分子成像探针增强乏氧肿瘤疗效研究进展

摘 要：肿瘤乏氧微环境的存在明显增加了肿瘤对临床常用治疗方法的抵抗和肿瘤自身的恶性程度。基于全氟化碳的纳米分子成像探针可携带、递送和释放氧气,具备可改善肿瘤乏氧的独特优势;另外,还能够进行19F-MR分子成像以监测和评价氧改善程度。其他协同当前多种临床常用以及全新的癌症诊疗方法方面都具有巨大的研究价值和应用潜力。全文对目前已研发的全氟化碳类纳米分子成像探针进行评述,讨论现有全氟化碳类纳米分子成像探针在缓解肿瘤乏氧微环境、协同不同癌症治疗方法方面研究进展。     

生长抑素受体显像与肿瘤的诊断和治疗

受体和配体的结合具有高度的特异性和组织专一性,研究发现多种肿瘤组织表达高密度的生长抑素受体(SSTR),放射性核素标记的生长抑素可以与肿瘤细胞膜上的生长抑素受体特异性结合,通过放射性核素的介导作用对肿瘤进行定位和诊断.β射线可以直接杀伤相应的肿瘤细胞起内辐射的治疗作用.     

以间皮素为靶点的肿瘤特异性核素成像研究进展

间皮素（mesothelin, MSLN）是多种肿瘤表面特异性表达的受体蛋白,特别是在以胰腺癌（80%~85%）为首的多种实体肿瘤中高表达,而在正常组织中间皮素的表达仅局限于胸膜、心包膜和腹膜中。通过新型核素标记抗MSLN抗体,可以对多种肿瘤进行特异性成像,对肿瘤早期诊断及预后评价起到重要的作用。本综述以间皮素为靶点,阐述与该靶点相关的胰腺癌等相关肿瘤间皮素靶点诊疗的重要进展,并重点阐述了核素标记的具有MSLN特异性的分子探针在肿瘤临床核素成像中的最新研究进展。     

生长抑素受体显像与肿瘤的诊断和治疗

受体和配体的结合具有高度的特异性和组织专一性，研究发现多种肿瘤组织表达高密度的生长抑素受体(SSTR)，放射性核素标记的生长抑素可以与肿瘤细胞膜上的生长抑素受体特异性结合，通过放射性核素的介导作用对肿瘤进行定位和诊断。口射线可以直接杀伤相应的肿瘤细胞起内辐射的治疗作用。     

肿瘤的靶向治疗

靶向治疗是针对肿瘤细胞恶性表型的分子靶点,作用于促进肿瘤生长、存活的特异性细胞受体、信号传导等通道,实现抑制肿瘤细胞生长或促进凋亡的抗肿瘤作用。新的靶向治疗药物rituximab、伊马替尼、赫赛汀和全反式维甲酸已开始用于临床治疗,本文综述这些药物的作用机制、适应证、疗效及安全性。与传统细胞毒化疗不同,肿瘤靶向治疗具有特异性抗肿瘤作用,并且毒性明显减少。肿瘤靶向治疗令人鼓舞的初步成果为其进一步发展奠定了基础,提供了典范,开创了肿瘤化疗的新领域。     

靶向 EphB4受体分子探针的研究进展

促红细胞生成素产生肝细胞受体（Eph）B 型受体4与肿瘤生长和肿瘤血管形成密切相关,并且在许多肿瘤中过量表达。EphB4靶向探针可提高肿瘤诊断的准确性和特异性。大量针对该靶点的分子探针已经被设计出来,有望为肿瘤的早期诊断和治疗提供新的方法。     

Update: improvement strategies for peptide receptor scintigraphy and radionuclide therapy

Somatostatin receptor-targeting peptides are widely used for the imaging and therapy of neuroendocrine tumors. Peptide-receptor radionuclide therapy (PRRT) in neuroendocrine tumor patients with radiolabeled somatostatin analogs has resulted in symptomatic improvement, prolonged survival, and enhanced quality of life. The side-effects of PRRT are few and mostly mild, certainly when using kidney protective agents. If a more widespread use of PRRT is possible, such therapy might become the therapy of first choice in patients with metastasized or inoperable neuroendocrine gastroenteropancreatic tumors. Yet, much profit can be gained from improving the receptor-targeting strategies available and developing new strategies. This review presents an overview of several options to optimize receptor-targeted imaging and radionuclide therapy. These include the optimization of peptide analogs, increasing the number of receptors on the tumor site, and combining PRRT with other treatment strategies. The development of new peptide analogs with increased receptor-binding affinity and improved stability might lead to a higher accumulation of radioactivity inside tumor cells. Analogs of somatostatin have been widely studied. However, much profit can be gained in improving peptide analogs targeting other tumor-related receptors, including gastrin-releasing peptide (GRP) receptors, neurotensin (NT) receptors, cholecystokinin (CCK) receptors, and glucagon-like peptide-1 (GLP-1) receptors. Several peptide analogs targeting these receptors are well on their way to clinical utilization. The literature shows that it is possible to increase the receptor density on tumor cells by using different methods, which results in higher binding and internalization rates and thus a higher contrast during peptide-receptor scintigraphy. In PRRT treatment, this would enable the administration of higher therapeutic doses to tumors, which might lead to a higher cure rate in patients. Combinations of radionuclide therapy with other treatment modalities, such as chemotherapy or pretreatment with radiosensitizers, might increase the impact of the treatment. Further, the administration of higher dosages of radioactivity to the patient, enabled by combinations of PRRT with strategies reducing the radiation dose to healthy organs, will improve the outcome of tumor treatment. Also, targeting one or several tumor-specific receptors by using combinations of therapeutic agents, as well as by reducing nontarget uptake of radioactivity, will enlarge the therapeutic window of PRRT. Clinical studies will provide more insight in the effects of combining treatment strategies in cancer patients.     

Nanomedicine for drug delivery and imaging: a promising avenue for cancer therapy and diagnosis using targeted functional nanoparticles

The diagnosis and treatment of cancer or tumor at the cellular level will be greatly improved with the development of techniques that enable the delivery of analyte probes and therapeutic agents into cells and cellular compartments. Organic and inorganic nanoparticles that interface with biological systems have recently attracted widespread interest in the fields of biology and medicine. The new term nanomedicine has been used recently. Nanoparticles are considered to have the potential as novel intravascular or cellular probes for both diagnostic (imaging) and therapeutic purposes (drug/gene delivery), which is expected to generate innovations and play a critical role in medicine. Target-specific drug/gene delivery and early diagnosis in cancer treatment is one of the priority research areas in which nanomedicine will play a vital role. Some recent breakthroughs in this field recently also proved this trend. Nanoparticles for drug delivery and imaging have gradually been developed as new modalities for cancer therapy and diagnosis. In this article, we review the significance and recent advances of gene/drug delivery to cancer cells, and the molecular imaging and diagnosis of cancer by targeted functional nanoparticles.     

钆类分子探针在肿瘤靶点显像中的研究进展

钆类对比剂是临床上常用的磁共振对比剂,靶向钆类分子探针较普通钆剂具备独特的优势,为疾病的精确诊断提供了新的思路。肿瘤分子影像学是近年来关注的焦点,本文就钆类分子探针在肿瘤靶点显像的研究展开综述。     

Imaging probes targeting matrix metalloproteinases

During the past few years, several imaging probes targeting matrix metalloproteinases (MMPs) have been developed. Most of these probes have been validated in animal models. Overall, results derived from most of these studies have been disappointing. Whether or not this relates to shortcomings of the imaging probes used or to the set-up of the reported studies is currently unclear. Firstly, MMPs targeted in these studies, MMP-1, -2 and -9, are cell secreted and their expression is known to vary extensively within one tumor type, depending on the stage of development of the tumor and on the presence of naturally occurring TIMPs. Given the lack of data on the levels of MMP expression by incoculated tumor tissue at the time of imaging in most studies reported, it cannot be excluded that the negative results reported are, in fact, false-negative imaging results. Secondly, given that most of the agents used for imaging are intrinsically broad-spectrum agents, their higher affinity for specific subsets of MMPs does not necessarily imply that a positive imaging result also corresponds to overexpression of specific subsets of MMPs, as suggested in some papers published. Accordingly, well-characterized tumor models need to be developed for the purpose of validating currently available, as well as future, MMP-imaging probes. So far, only 111In-DTPA-N-TIMP-2 has been injected in patients, respectively suffering from Kaposi Sarcoma. Imaging results obtained with this agent proved disappointing. Imaging results obtained with other MMP-targeting probes in patients are awaited.     

MR and iron magnetic nanoparticles. Imaging opportunities in preclinical and translational research

Ultrasmall superparamagnetic iron oxide nanoparticles and magnetic resonance imaging provide a non-invasive method to detect and label tumor cells. These nanoparticles exhibit unique properties of superparamagnetism and can be utilized as excellent probes for magnetic resonance imaging. Most work has been performed using a magnetic resonance scanner with high field strength up to 7 T. Ultrasmall superparamagnetic iron oxide nanoparticles may represent a suitable tool for labeling molecular probes that target specific tumor-associated markers for in vitro and in vivo detection by magnetic resonance imaging. In our study, we demonstrated that magnetic resonance imaging at 1.5 T allows the detection of ultrasmall superparamagnetic iron oxide nanoparticle conjugated antibody specifically bound to human tumor cells in vitro and in vivo, and that the magnetic resonance signal intensity correlates with the concentration of ultrasmall superparamagnetic iron oxide nanoparticle antibody used and with the antigen density at the cell surface. The experiments were performed using two different means of targeting: direct and indirect magnetic tumor targeting. The imaging of tumor antigens using immunospecific contrast agents is a rapidly evolving field, which can potentially aid in early disease detection, monitoring of treatment efficacy, and drug development. Cell labeling by iron oxide nanoparticles has emerged as a potentially powerful tool to monitor trafficking of a large number of cells in the cell therapy field. We also studied the labeling of natural killer cells with iron nanoparticles to a level that would allow the detection of their signal intensity with a clinical magnetic resonance scanner at 1.5 T. Magnetic resonance imaging and iron magnetic nanoparticles are able to increase the accuracy and the specificity of imaging and represent new imaging opportunities in preclinical and translational research.     

Fluorescence imaging agents in cancerology

BACKGROUND: One of the major challenges in cancer therapy is to improve early detection and prevention using novel targeted cancer diagnostics. Detection requests specific recognition. Tumor markers have to be ideally present on the surface of cancer cells. Their targeting with ligands coupled to imaging agents make them visible/detectable. CONCLUSIONS: Fluorescence imaging is a newly emerging technology which is becoming a complementary medical method for cancer diagnosis. It allows detection with a high spatio-temporal resolution of tumor markers in small animals and in clinical studies. In this review, we focus on the recent outcome of basic studies in the design of new approaches (probes and devices) used to detect tumor cells by fluorescence imaging.     

Hapten-directed targeting to single-chain antibody receptors

Artificial recombinant receptors may be useful for selectively targeting imaging and therapeutic agents to sites of gene expression. To evaluate this approach, we developed transgenes to express highly on cells a single-chain antibody (scFv) against the hapten 4-ethoxymethylene-2-phenyl-2-oxazoline-5-one (phOx). A phOx enzyme conjugate was created by covalently attaching phOx molecules to polyethylene glycol (PEG)-modified beta-glucuronidase. Cells expressing phOx scFv but not control scFv receptors were selectively killed after exposure to ss-glucuronidase derivatized with phOx and PEG (phOx-beta G-PEG) and a glucuronide prodrug (p-hydroxy aniline mustard beta-D-glucuronide, HAMG) of p-hydroxyaniline mustard. Targeted activation of HAMG produced bystander killing of receptor-negative cells in mixed populations containing as few as 10% phOx-receptor-positive cells. Functional phOx scFv receptors were stably expressed on B16-F1 melanoma tumors in vivo. Treatment of mice bearing established phOx-receptor-positive tumors with phOx-beta G-PEG and HAMG significantly (P< or =.0005) suppressed tumor growth as compared with treatment with beta G-PEG and HAMG or prodrug alone. phOx was unstable in the serum, suggesting alternative haptens may be more suitable for in vivo applications. Our results show that therapeutic agents can be targeted to artificial hapten receptors in vitro and in vivo. The expression of artificial receptors on target cells may allow preferential delivery of therapeutic or imaging molecules to sites of transgene expression.     

全人源抗TRAIL-R1／-R2单克隆抗体肿瘤治疗的研究进展

目前全人源TRAIL受体（TRAIL-Rs）的单克隆抗体（单抗）对肿瘤靶向治疗已进入临床Ⅰ～Ⅳ期研究。TRAIL-Rs单抗可分别与死亡受体TRAIL-R1和TRAIL-R2结合,形成死亡诱导信号复合体（DISC）,诱导肿瘤细胞凋亡,成为抗肿瘤抗体药物研发的热点之一。全人源TRAIL-Rs单抗与放疗、化疗药物或其它制剂以及免疫治疗方法联合应用在肿瘤治疗中取得了显著的效果,为临床抗肿瘤治疗提供了新方案。     

Nanoparticles for imaging and tumor gene delivery

Molecular imaging of receptors expressed on the surface of tumor cells is becoming a major field of investigation in clinical oncology, especially for the detection of cancer at its earliest stages. Nowadays, MRI, microcomputed tomography (microCT), ultrasound, positron emission tomography (PET), optical coherence tomography (OCT), and other major imaging systems are available to scientists and clinicians. Each technique has advantages and limitations, thus making them complementary. We report herein our investigations on the synthesis and use of new probes for small animal imaging as well as on the preparation and use of targeting complexes to deliver specific gene in tumors cells.     

The histone deacetylase inhibitor NVP-LAQ824 inhibits angiogenesis and has a greater antitumor effect in combination with the vascular endothelial growth factor receptor tyrosine kinase inhibitor PTK787/ZK222584

Chromatin remodeling agents such as histone deacetylase inhibitors have been shown to modulate gene expression in tumor cells and inhibit tumor growth and angiogenesis. Vascular endothelial growth factor (VEGF) and VEGF receptors represent critical molecular targets for antiangiogenesis therapy. In this study, we investigated the biological effect of the histone deacetylase inhibitor NVP-LAQ824 in combination with the VEGF receptor tyrosine kinase inhibitor PTK787/ZK222584 on tumor growth and angiogenesis. We report that treatment with NVP-LAQ824 affected tumor and endothelial cells and was associated with increased histone acetylation, p21 up-regulation, and growth inhibition. In addition, NVP-LAQ824 treatment inhibited the expression of angiogenesis-related genes such as angiopoietin-2, Tie-2, and survivin in endothelial cells and down-regulated hypoxia-inducible factor 1-alpha and VEGF expression in tumor cells. Combination treatment with NVP-LAQ824 and PTK787/ZK222584 was more effective than single agents in inhibiting in vitro and in vivo VEGF-induced angiogenesis. Endothelial cell proliferation, tube formation, and invasion into the Matrigel plugs were reduced. In mouse models with established subcutaneous prostate (PC3) and orthotopic breast tumors (MDA-MB321), this combination treatment induced 80 to 85% inhibition of tumor growth without overt toxicity. These results suggest that the combination of histone deacetylase inhibitors and VEGF receptor inhibitors may target multiple pathways in tumor progression and angiogenesis and represents a novel therapeutic approach in cancer treatment.