肿瘤基因治疗相关的特异性启动子研究新进展

肿瘤基因治疗是一种在基因水平上治疗肿瘤的方法,是现有治疗肿瘤的先进方法之一。但是,肿瘤基因治疗技术还存在很多未解决的问题,例如目的基因表达的靶向性问题等。现有研究证实,使用特异性启动子可以提高肿瘤基因治疗的靶向性。启动子是指能启动mRNA转录的一段特异性DNA序列,特异性启动子是指仅在特定组织或肿瘤中才会被激活的启动子。该文将就肿瘤基因治疗相关的特异性启动子的近期研究,按启动子的作用类型进行综述。     

超顺磁性纳米粒在肿瘤诊断治疗中的应用研究进展

超顺磁性氧化铁纳米粒（ SPION）作为一种新型纳米材料,具有超顺磁性、靶向性和良好的生物相容性。利用SPION的被动靶向和磁靶向的特点,使其在肿瘤部位富集,不仅作为磁共振成像（ MRI）的造影剂用于临床肿瘤的早期诊断,还可作为抗肿瘤药物载体,将药物靶向递送到病灶部位,提高生物利用度,减少不良反应。该文综述了SPION在MRI造影和作为药物载体方面应用的研究进展。     

肿瘤分子核医学

近年来以分子靶向为主导的分子核医学在肿瘤诊断和治疗的研究和应用中发展迅速。许多病变的标志物或其天然配体有不少能直接转换为显像剂。这些显像剂可用于：建立肿瘤诊断方法；指导治疗(因能显示肿瘤中相应靶分子的存在)；证实肿瘤基因治疗制剂的传送；评价肿瘤治疗后的反应；评价肿     

噬菌体展示技术在肿瘤诊断和治疗中的应用

噬菌体体内展示技术的出现,使器官靶向性多肽的筛选、器官特异性血管分子作图成为可能。更值得注意的是,通过动物体内的筛选,鉴定出了一系列肿瘤相关分子的标志物的特异性多肽配体,为肿瘤的诊断,肿瘤药物的输送以及肿瘤血管性基因治疗等提供了靶向性分子。最近,人们又成功地将此技术应用于肿瘤患者,并鉴定出与肿瘤特异性结合的多肽模序。     

RNA干扰在组织特异性靶向性基因治疗中的研究进展

RNA干扰（RNA interference,RNAI）技术是一种有效的基因沉默技术,由于其高度特异性、高效性以及稳定性等特点,RNA干扰技术在肿瘤基因治疗研究中得到了广泛的应用。靶向性基因治疗是肿瘤生物治疗的一个重要研究方向。本文以RNA干扰技术在靶向性基因治疗中的研究进展进行综述。     

介入手段实现的局部转导在肿瘤基因治疗系统中的应用

肿瘤的基因治疗主要包括自杀基因治疗、抑癌基因治疗、反义癌基因治疗和免疫基因治疗等，相应的载体可选用病毒类或非病毒类载体。在临床与研究中，介入手段实现的局部转导主要包括转基因载体的肿瘤瘤体内注射和经导管血管内灌注，具体手段的选择与治疗机理、载体以及肿瘤特性等多种因素相关。     

介入手术实现的忆部转在肿瘤基因治疗系统中的应用

肿瘤的基因治疗主要包括自杀基因治疗、抑癌基因治疗、反义癌基因治疗和免疫基因治疗等，相应的载体可选用病毒类或非病毒类载体。在临床与研究中，介入手段实现的局部转导主要包拓转基因载体的肿瘤瘤体内注射和经导管血管内灌注，具体手段的选择与治疗机理、载体以及肿瘤特性等多种因素相关。     

主动靶向脂质体在肿瘤MRI诊断中的应用

主动靶向脂质体作为MRI对比剂的载体,以其良好的生物相容性、无毒性、主动靶向性等特点在肿瘤诊断及治疗领域显示出独特的优势。通过在脂质体上标记特殊的分子识别系统或制成对pH值、温度敏感的脂质体,实现肿瘤靶向成像是研究的热点。该文就各种主动靶向脂质体在肿瘤MRI诊断中的应用进行综述。     

前列腺癌靶向治疗研究进展

肿瘤靶向治疗是目前肿瘤研究的热点。肿瘤靶向治疗是利用具有高导向性的载体将药物等运送到肿瘤这一特定＂靶标＂,发挥抗肿瘤作用,同时避免或减轻药物对正常细胞的损伤的治疗方法。目前,实现癌症靶向治疗的策略主要有单克隆抗体治疗、靶向基因治疗、RNA干扰技术、小分子靶向药物等。这些靶向治疗策略绝大部分还仅仅处于实验室研究阶段,且均存在一定的局限性。     

基因转移技术与基因靶向性核素治疗

随着在细胞分子水平上对疾病发病机制认识的深入,基因治疗已成为目前医学分子生物学最重要的研究领域之一。基因治疗过程中基因转移技术起着关键作用,携带目的基因的载体有待进一步开发和改进。在基因治疗过程中,需要进行基因监测,基因显像是其最有效的方法。将基因治疗与靶向核素治疗相结合,即"基因靶向核素治疗"为肿瘤基因治疗开辟了一条崭新的途径。     

磁性纳米氧化铁粒子在肿瘤影像及治疗中的应用及进展

磁性纳米氧化铁粒子是指直径在纳米范围的氧化铁粒子,具有化学性质稳定、血液滞留时间长、低毒性、顺磁性、生物可降解性等特点,可通过静电作用或化学作用耦联多肽、单克隆抗体、化疗药物、基因片段等靶肿瘤功能分子,因而在肿瘤影像、治疗、研究中有着广泛的应用.该文对近年来磁性纳米氧化铁粒子在肿瘤影像及治疗中的应用及进展进行了评述.     

Imaging and therapy of tumors induced to express somatostatin receptor by gene transfer using radiolabeled peptides and single chain antibody constructs

The fields of radioimmunodetection and radioimmunotherapy began with an initial paradigm that a targeting molecule (eg, antibody) carrying a radioisotope had the potential of selectively imaging and delivering a therapeutic dose of radiation to tumor sites. A second paradigm was developed in which injection of the targeting molecule was separated from injection of a short-lived radioisotope-labeled ligand (so-called "pretargeting strategy"). This strategy has improved radioisotope delivery to tumors in animal models, enhanced radioimmune imaging in man, and therapeutic trials are in an early phase. We proposed a third paradigm to achieve radioisotopic localization at tumor sites by inducing tumor cells to synthesize a membrane expressed receptor with a high affinity for infused radiolabeled ligands. The use of gene transfer technology to induce expression of high affinity membrane receptors can enhance the specificity of radioligand localization, while the use of radioisotopes with the ability to deliver radiation damage across several cell diameters will compensate for less than perfect transduction efficiency. This approach was termed "Genetic Radioisotope Targeting Strategy." Using this strategy, induction of high levels of gastrin releasing peptide receptor or human somatostatin receptor subtype 2 expression and selective tumor uptake of radiolabeled peptides was achieved. The advantages of the genetic transduction approach are (1) constitutive expression of a tumor-associated antigen/receptor is not required; (2) tumor cells are altered to express a new target receptor or increased quantities of an existing receptor at levels that may significantly improve tumor targeting of radiolabeled ligands compared with normal tissues; (3) gene transfer can be achieved by intratumoral or regional injection of gene vectors; (4) it is feasible to target adenovirus vectors to receptors overexpressed on tumor cells by modifying adenoviral tropism (binding) so that the virus will be targeted specifically to the desired tumor; and (5) it is possible to coexpress the receptor gene and a therapeutic gene, such as cytosine deaminase, for molecular prodrug therapy to produce an enhanced therapeutic effect.     

基于树状大分子材料构建的纳米载药体系用于肿瘤靶向治疗的研究进展

近年来兴起的树状大分子材料的结构可控,且其与细胞膜和各种活性药物分子具有独特的相互作用,因此成为构建纳米载药体系的优良材料,并在肿瘤靶向治疗领域得到了广泛研究。树状大分子作为具有良好生物相容性的纳米分子,可与肿瘤靶向分子偶联,从而将活性药物分子特异性递送到肿瘤组织,如此可最大限度地提高药物的靶向性,并减少其对非靶组织的毒性作用。笔者就近年来基于树状大分子材料构建的纳米载药体系用于肿瘤靶向治疗的研究进展进行综述。     

Biodistribution and antitumor effect of Cetuximab-targeted lentivirus

Viral vectors are central tools for gene therapy. Targeting of the vector to desired tissues followed by expression of the therapeutic gene forms one of the most critical points in effective therapy. In this study we used streptavidin-displaying lentivirus conjugated to biotinylated anti-epidermal growth factor receptor (EGFR) antibody (Cetuximab) to target vector specifically to ovarian tumors.Biodistribution of the targeted virus was studied in nude mice with orthotropic SKOV-3m human ovarian carcinoma xenografts. Radiolabeled antibodies were conjugated to streptavidin-displaying lentiviruses and biodistribution of the virus after the intravenous delivery to tumor-bearing mice was monitored up to 6 days using combined SPECT/CT imaging modality. Organ samples were collected post mortem and specific organ activities were measured. The integration of lentivirus vectors in collected tissue samples was analyzed using qPCR and the expression of green fluorescent protein (GFP)-transgene was tested by enzyme-linked immunosorbent assay.Our results showed that lentiviruses conjugated to Cetuximab (Cet-LV) or control human IgG (IgG-LV) accumulated mainly to the liver and spleen of the mice and to lower extent to lung, kidneys and tumors. Strikingly, in 50% of the mice injected with cetuximab-targeted lentivirus no tumor tissue was found, whereas the remaining half showed a significant decrease in tumor size. We hypothesize/present data that lentivirus-mediated INF-αβ production together with tumor targeting could function as an effective antitumor treatment.     

Gene expression imaging with radiolabeled peptides

An approach to image radiolabeled peptide localization at tumor sites by inducing tumor cells to synthesize membrane expressed human somatostatin receptor subtype 2 (hSSTr2) with a high affinity for radiolabeled somatostatin analogues is described. The use of gene transfer technology to induce expression of high affinity membrane hSSTr2 can enhance the specificity and degree of radiolabeled peptide localization in tumors. Employing this strategy, induction of high levels of hSSTr2 expression with selective tumor uptake of radiolabeled peptides was achieved in both subcutaneous non-small cell lung cancer and intraperitoneal ovarian cancer mouse human tumor xenograft models. The features of this genetic transduction imaging approach are: (1) constitutive expression of a tumor-associated receptor is not required; (2) tumor cells are altered to express a new target receptor or increased quantities of a constitutive receptor at levels which may significantly increase tumor targeting of radiolabeled peptides compared to uptake in normal tissues; (3) gene transfer can be accomplished by local or regional injection of adenoviral vectors; (4) it is feasible to target adenovirus vectors to tumor cells by modifying adenoviral tropism (binding) or by the use of tumor-specific promoters such that the hSSTr2 will be specifically expressed in the desired tumor; and (5) this technique can be used to image expression of a second therapeutic gene.     

Pretargeted radioimmunotherapy of mesothelin-expressing cancer using a tetravalent single-chain Fv-streptavidin fusion protein.

Mesothelin is a glycoprotein that is overexpressed in several human tumors, including mesotheliomas and ovarian cancers, and has been identified as a potential target for therapy. We evaluated the biodistribution and tumor-targeting ability of an antimesothelin tetravalent single-chain Fv-streptavidin fusion protein (SS1scFvSA) in mice. METHODS: SS1scFvSA was labeled with 125I or 111In for evaluation of internalization in vitro and for optimization of its biodistribution. The A431-K5 mesothelin transfected cell line was used as the target. We used a 3-step pretargeting approach consisting of injections of (i) SS1scFvSA, followed 20 h later by (ii) a synthetic clearing agent, and (iii) 4 h later, radiolabeled (111In, 88Y/90Y, or 177Lu) 1,4,7,10-tetraazacyclododecane-N,N',N',N'-tetraacetic acid (DOTA)-biotin. To optimize the tumor uptake, the effect of the specific activity of 111In-DOTA-biotin was evaluated. RESULTS: Approximately 60% of SS1sc FvSA internalized within 6 h. The optimal dose of SS1scFvSA for pretargeting was 600 microg. Decreasing the specific activity of DOTA-biotin by administering 0.1-5 microg of DOTA-biotin resulted in tumor uptake decreasing from 31.8 to 5.5 %ID/g (percentage injected dose per gram) at 2 h. Pretargeted therapy of A431-K5 tumor with 90Y doses of 11.1-32.4 MBq resulted in a dose-dependent tumor response. With 32.4 MBq, 86% of mice survived tumor free for 110 d. All nontreated mice died, with a median survival of 16 d. CONCLUSION: SS1scFvSA localized in the mesothelin-expressing tumor, resulting in a high accumulation of radiolabeled DOTA-biotin. The specific activity of DOTA-biotin had a significant effect on its tumor uptake. Therapeutic tumor doses were obtained without dose-limiting toxicity.     

内皮抑素基因联合放射治疗对大鼠Walker-256细胞种植性肿瘤的抑制作用

目的探讨鼠源性内皮抑素（endostatin）基因联合放射治疗对大鼠种植性肿瘤的抑制效应。方法制作大鼠乳腺癌Walker-256细胞种植性肿瘤的动物模型，通过检测肿瘤重量和肿瘤生长速率观察内皮抑素基因治疗联合放疗的抑瘤效应。体外采用Western blot检测构建pCMV-endostatin质粒转染的Walke-256细胞endostatin蛋白表达，体内采用BT-PCR观察各组endostatin mRNA表达。结果基因治疗组和基因治疗联合放射治疗组均可见到endostatin mRNA及其蛋白明显表达，但两组间表达无统计学意义；基因与放射联合组肿瘤的生长速率和重量均明显小于单纯基因治疗和放疗组（P〈0．01），后两组其肿瘤的生长速率和重量明显低于对照组（P〈0．01），但二者之间差异无统计学意义。结论pCMV-endostatin在Walker-256细胞内有明显表达endostatin mRNA及其蛋白；endostatin基因治疗有明显的抑瘤作用，但endostatin基因联合放疗的抑瘤效应更明显，促进放疗的抑瘤效果。     

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。