肿瘤自杀基因靶向治疗

肿瘤自杀基因疗法是近年来肿瘤治疗的研究热点,尤其是自杀基因的选择与重组,载体系统的优化,基因的靶向性转移表达,以及自杀基因的联合治疗等均有助于提高自杀基因特异性表达,增强杀伤肿瘤细胞的作用。现就自杀基因在肿瘤治疗中的应用现状作一综述。     

肿瘤自杀基因靶向治疗的研究进展

自杀基因治疗是目前肿瘤基因治疗中的研究热点.本文重点从自杀基因的种类、载体、作用机制和发展应用前景等几方面进行综述.其中HSV1-tk/GCV自杀基因系统是研究最多、临床价值最为明确的自杀基因系统之一.治疗机制上除通过直接作用和旁观者效应发挥作用外,还从自杀基因联合使用、趋化因子等细胞因子作用、自杀基因与放射治疗联合作用、自杀基因与免疫治疗联合使用等多方面进行了探索和研究.众多研究结果认为自杀基因治疗是一种具有良好应用前景的肿瘤治疗方法,但在临床应用上还有很多问题需要解决,如将自杀基因安全、高效地转染到人体肿瘤组织和细胞中的方法,如何能使自杀基因在靶组织中稳定表达并发挥作用,各种治疗方法的协同作用等,均有待于我们在今后的研究中进一步解决.     

肿瘤自杀基因靶向治疗

肿瘤自杀基因疗法是近年来肿瘤治疗的研究热点，尤其是自杀基因的选择与重组，载体系统的优化，基因的靶向性转移表达，以及自杀基因的联合治疗等均有助于提高自杀基因特异性表达，增强杀伤肿瘤细胞的作用。现就自杀基因在肿瘤治疗中的应用现状作一综述。     

自杀基因治疗恶性肿瘤研究进展

恶性肿瘤的基因治疗是现代医学领域的研究热点，其中自杀基因疗法可能成为一种极具潜力和临床应用价值的治疗手段，在治疗范围上，已扩大到全身所有脏器及各种组织类型的恶性肿瘤，在提高其转录靶向调控机制上，已发现了许多特异性启动子元件，来增强自杀基因作用的特异性及可调控性，并已尝试利用辐射诱导来提高其转基因表达的外源性调控机制；此外，采用自杀基因与集落刺激因子(GM—CSF)、细胞因子等联合应用，诱导产生更强的抗肿瘤免疫，进一步增强杀伤肿瘤的效力。     

放射线诱导hEgr-1-CD对鼻咽癌CNE放射增敏作用的研究

目的 研究放射线诱导hEgr-1-CD自杀基因前药系统对鼻咽癌CNE细胞株放射增敏作用。方法 将pcDNA3.1（＋）Egr-1-CD利用脂质体转染的方法 转染入鼻咽癌细胞株,给予不同剂量的X线照射观察基因表达与放射的剂量效应关系,观察不同的放射线及不同剂量的前药对鼻咽癌细胞的杀伤效应。结果 电离辐射可诱导增强自杀基因阳性鼻咽癌CNE细胞株中CD基因的表达,电离辐射与前药5-Fc的联合应用大大增强了对自杀基因阳性细胞的杀伤作用,其杀伤作用大于单独自杀基因前药系统和单独照射。结论 hEgr-1-CD自杀基因前药系统对鼻咽癌CNE细胞株有放射增敏作用,其与放射联合应用对CNE细胞有明显的协同杀伤作用。     

自杀基因在肝癌治疗中的应用现状

目前，在自杀基因治疗肝癌的研究中，通过联合基因治疗，受体介导定位、改变酶特性，寻找新的自杀基因系统，以及选择不同用药策略和途径等，方法将自杀基因高效导入靶细胞， 并使之表达，从而增强特异性杀伤肝脏肿瘤细胞作用。临床应用前景广阔。     

SCF或(和)GM-CSF体内基因转染对"自杀基因"疗法抗肿瘤作用的增强效应及其相关机理的研究

目的通过增强体内抗原提呈功能提高“自杀基因”疗法疗效，探讨其相关免疫学机理。方法采用腺病毒介导的ＳＣＦ、ＧＭＣＳＦ基因体内转染联合ＣＤ／５ＦＣ“自杀基因”疗法治疗小鼠的ＣＴ２６结肠腺癌，观察肿瘤的生长和荷瘤小鼠的存活期、不同方法所诱导的ＣＴＬ杀伤活性及肿瘤局部的细胞因子表达。结果一次性低剂量腺病毒介导的ｍＧＭＣＳＦ或（和）ｍＳＣＦ基因的体内转染，能增强“自杀基因”疗法的疗效。在肿瘤局部出现新的细胞因子表达，包括ｍＩＬ４、ｍＩＬ２、ｍＩＦＮγ和ｍＴＮＦα。脾细胞对ＣＴ２６细胞的杀伤作用增强。结论ｍＧＭＣＳＦ或（和）ｍＳＣＦ基因的联合转染对“自杀基因”系统的疗效具有明显的增强作用，其与机体特异抗肿瘤免疫功能以及肿瘤局部分泌的细胞因子有关。     

自杀基因在肺癌中的研究进展

全文从自杀基因治疗体系的构成、作用机制、旁观者效应、与其他治疗联合应用、提高自杀基因转导效率及其在肺癌中的研究进展进行综述.     

肿瘤的自杀基因治疗研究进展

肿瘤的自杀基因治疗法是一种具有潜在临床应用价值的新的肿瘤治疗策略。综述了近年来自杀基因疗法在肿瘤治疗中取得的研究进展 ,分别从自杀基因作用机制、自杀基因体系、载体的构建、旁观者效应、自杀基因与免疫反应、联合基因治疗等几个方面进行综述。     

肿瘤的自杀基因治疗研究进展

肿瘤的自杀基因治疗法是一种具有潜在临床应用价值的新的肿瘤治疗策略。综述了近年来自杀基因疗法1在肿瘤治疗中取得的研究进展，分别从自杀基因作用机制、自杀基因体系、载体的构建、旁观者效应、自杀基因与免疫1反应、联合基因治疗等几个方面进行综述。     

自杀基因治疗恶性肿瘤的研究现状及展望

肿瘤的自杀基因疗法是近年来肿瘤基因治疗的研究热点,是一种具有潜在临床应用前景的新的肿瘤基因治疗策略。本文就近年来自杀基因疗法在肿瘤治疗中取得的研究进展,分别从作用机制、自杀基因系统、旁观者效应、自杀基因的转导以及联合基因治疗等几个方面进行综述。     

Prodrug suicide gene therapy for cancer targeted intracellular by mesenchymal stem cell exosomes

The natural behavior of mesenchymal stem cells (MSCs) and their exosomes in targeting tumors is a promising approach for curative therapy. Human tumor tropic mesenchymal stem cells (MSCs) isolated from various tissues and MSCs engineered to express the yeast cytosine deaminase::uracil phosphoribosyl transferase suicide fusion gene (yCD::UPRT-MSCs) released exosomes in conditional medium (CM). Exosomes from all tissue specific yCD::UPRT-MSCs contained mRNA of the suicide gene in the exosome's cargo. When the CM was applied to tumor cells, the exosomes were internalized by recipient tumor cells and in the presence of the prodrug 5-fluorocytosine (5-FC) effectively triggered dose-dependent tumor cell death by endocytosed exosomes via an intracellular conversion of the prodrug 5-FC to 5-fluorouracil. Exosomes were found to be responsible for the tumor inhibitory activity. The presence of microRNAs in exosomes produced from naive MSCs and from suicide gene transduced MSCs did not differ significantly. MicroRNAs from yCD::UPRT-MSCs were not associated with therapeutic effect. MSC suicide gene exosomes represent a new class of tumor cell targeting drug acting intracellular with curative potential.     

Quantitative evaluation and comparison of two prodrug-activating suicide gene therapies on oral squamous cell carcinoma

Prodrug-activating suicide gene therapy (PA suicide gene therapy for short) for cancer is to introduce cancer cells with suicide genes. The enzyme encoded by suicide gene is not toxic but is able to kill cancer cells by converting a non-toxic prodrug into a toxic compound. This approach is a promising cancer gene therapy that could reduce non-specific toxicity to normal tissue. However, there is no quantitative method to evaluate efficacy of suicide gene therapy in preclinical study. The aim of this study is to develop a new method to quantitatively evaluate and compare prodrug-activating suicide gene therapies. This study was carried out on an oral squamous cell carcinoma (OSCC) cell line CAL-27. Suicide genes were integrated into ROSA26 locus of CAL-27 by CRISPR-Cas9. CAL-27 cell lines stably expressing herpes simplex virus-thymidine kinase (TK) or yeast cytosine deaminase (CD) were used to evaluate and compare PA suicide gene therapies. The efficacies of PA suicide gene therapies were quantitatively evaluated from three aspects: effective prodrug concentration, prodrug treatment time, and bystander effect. This method also could be used for different types of suicide gene therapies and different types of cancer. When the prodrug concentration, treatment time, and rate of suicide gene-positive cells (related to bystander effect) are fixed, anti-cancer effects could be quantitatively measured. This information is important for suicide gene therapy preclinical development.     

Sequential Histopathological Changes in vivo after Suicide Gene Therapy of Gastric Cancer Induced by N-Methyl-N'-nitro-N-nitrosoguanidine in Rats

Gastrointestinal cancer is the most important clinical target of gene therapy. Suicide gene therapy, such as with the herpes simplex virus type 1 thymidine kinase ( HSV-TK ) gene, has been shown to exert antitumor efficacy in various cancer models in vitro. We previously reported in situ gene transfer and gene therapy for gastric cancer induced by N -ethyl-. N '-nitro-. N -nitrosoguanidine (ENNG) in dogs. Here, we describe the sequential histopathological changes after suicide gene therapy of N -methyl-. N '-nitro-. N nitrosoguanidine (MNNG)-induced gastric cancer in rats. Gastric tumors were induced by MNNG in 38/73 (52%) of Wistar strain rats. The suicide gene therapy group (14 rats) was subjected to in situ gene transfer with a recombinant adenovirus vector carrying the HSV-TK gene driven by CAG promoter (Ad.CAGHSV-TK) in gastric tumor, followed by the antiviral drug ganciclovir (GCV). To observe the histopathological changes at various tunes after HSV-TK/GCV gene therapy, groups of animals were sacrificed at 3, 8, and 30 days after gene transfer. Apoptosis in the gastric tumors was detected by the TUNEL method to assess the efficacy of HSV-TK/GCV gene therapy, and it was marked in the 8- and 30-day treatment groups compared to the sham operation controls ( P <0.001). Various histopathological changes, degeneration of cancer tissue and fibrosis after necrosis and apoptosis were significantly greater in the 30-day treatment group. The HSV-TK gene was detectable in peripheral blood by PCR until 30 days after gene transfer. These results may be useful in devising a method of suicide gene therapy for humans.     

Intracellular prodrug gene therapy for cancer mediated by tumor cell suicide gene exosomes

Recently, we reported about exosomes possessing messenger RNA (mRNA) of suicide gene secreted from mesenchymal stem/stromal cells (MSCs) engineered to express the suicide gene—fused yeast cytosine deaminase::uracil phosphoribosyltransferase (yCD::UPRT). The yCD::UPRT‐MSC exosomes are internalized by tumor cells and intracellularly convert prodrug 5‐fluorocytosine (5‐FC) to cytotoxic drug 5‐fluorouracil (5‐FU). Human tumor cells with the potential to metastasize release exosomes involved in the creation of a premetastatic niche at the predicted organs. We found that cancer cells stably transduced with yCD::UPRT gene by retrovirus infection released exosomes acting similarly like yCD::UPRT‐MSC exosomes. Different types of tumor cells were transduced with the yCD::UPRT gene. The homogenous cell population of yCD::UPRT‐transduced tumor cells expressed the yCD::UPRT suicide gene and secreted continuously exosomes with suicide gene mRNA in their cargo. All tumor cell suicide gene exosomes upon internalization into the recipient tumor cells induced the cell death by intracellular conversion of 5‐FC to 5‐FU and to 5‐FUMP in a dose‐dependent manner. Most of tumor cell‐derived suicide gene exosomes were tumor tropic, in 5‐FC presence they killed tumor cells but did not inhibit the growth of human skin fibroblast as well as DP‐MSCs. Tumor cell‐derived suicide gene exosomes home to their cells of origin and hold an exciting potential to become innovative specific therapy for tumors and potentially for metastases.     

Combination gene therapy using multidrug resistance (MDR1) gene shRNA and herpes simplex virus-thymidine kinase

The current study was designed to evaluate the anti-tumor effects of MDR1 shRNA in combination with herpes simplex virus-thymidine kinase/ganciclovir (HSV-tk/GCV) suicide gene therapy system. Introduction of an MDR1-targeted small hairpin RNA (shMDR) markedly enhanced the intracellular accumulation of and increased sensitivity to drugs transported by P-glycoprotein. Functional TK-eGFP fusion protein expression was confirmed by Western blot analysis and ganciclovir uptake assay. Compared with GCV or doxorubicin alone, the combination of anti-cancer drug chemotherapy with GCV administration displays additive cytotoxicity in shMDR1-TK-eGFP expressing cells. These results for the first time suggest the potential of combination gene therapy using suicide gene therapy and RNAi-based gene therapy in vitro.     

肿瘤双自杀基因治疗系统pTRKH2-PsT/CD,pTRKH2-PsT/UPRT在厌氧婴儿双歧杆菌中的构建

Objective: We recombine the suicide gene CD, UPRT into plasmid pTRKH2 and clone the recombinant dual suicide gene therapy system into tumor-hypoxia-targeting vector Bifidobacterium infantis and characterize its function. Methods: CD gene, UPRT gene and lactic acid bacteria expression plasmid pTRKH2 were digested by restriction endonuclease BamH I and Sal I, and constructed recombinant plasmids pTRKH2/CD and pTRKH2/UPRT in E. coll. The recombinant plasmids were then transfected into Bifidobacterium Infantis by electroporation. Identification of pTRKH2/CD and pTRKH2/UPRT was processed by dual restriction endonuclease digesting and sequencing. RT-PCR and SDS-PAGE were used to examine the expression of CD and UPRT genes at RNA and protein levels. The killing effects on Melanoma B16-F10 cells by pTRKH2/CD and pTRKH2/UPRT suicide gene therapy system with 5-FC were examined by MTT assay. Results: The CD gene and UPRT gene was successfully recombined into lactic acid bacteria expression plasmid pTRKH2. After dual endonuclease digestion of plasmid purified from the positively transfected E. co/i, two fragments of 6.9 Kb and 1.3 Kb were found for CD gene and two fragments of 6.9 Kb and 620 bp were found for UPRT gene. The sequencing of CD gene and UPRT gene proved consistent sequences with Genebank published data. A fragment of 1.3 Kb for CD gene and fragment of 620 bp for UPRT gene was found in recombinant Bifidobac- terium by RT-PCR. A 52 KDa protein for CD gene was identified in whole-cell protein of recombinant Bifidobacterium and a 26 KDa protein for UPRT gene was identified in supernatant fluid of recombinant Bifidobacterium. The survival rate of tumor cells treated by extracts from culture of recombinant Bifidobacterium with 5-FC showed a strong killing effects of pTRKH2/CD and pTRKH2/UPRT dual suicide gene therapy system on Melanoma B16-F10 cells. Conclusion: CD gene and UPRT gene are suc- cessfully inserted into pTRKH2 and transfected into tumor-hypoxia-targeting vector Bifldobacterium Infantis. This dual suicide gene therapy system shows a high efficiency for tumor cells killing.     

肿瘤厌氧靶向双自杀基因治疗系统pTRKH2-PsT/CD、pTRKH2-PsT/UPRT的构建

目的 利用婴儿双歧杆菌对实体瘤低氧区的靶向效应,构建肿瘤厌氧靶向双自杀基因治疗系统pTRKH2-PsT /CD和pTRKH2-PsT /UPRT。方法 用PCR的方法从质粒pGEX/CD和pGEX/UPRT中扩增出CD基因和UPRT基因,双酶切CD基因、UPRT基因和质粒pTRKH2-PsT,分别连接后重组于大肠杆菌中。之后用电转化的方法将重组质粒转入婴儿双歧杆菌中。用RT-PCR检测该系统mRNA水平的表达,SDS-PAGE检测该系统在蛋白质水平的表达。在黑色素瘤B16-F10细胞上检测该系统的体外肿瘤细胞杀伤效果。结果 成功地将CD基因和UPRT基因转入了质粒pTRKH2-PsT,CD基因和UPRT基因的测序结果表明序列与Genebank公布的序列一致。RT-PCR检测到CD和UPRT mRNA水平的明显表达。在含有CD基因的婴儿双歧杆菌细胞全蛋白中发现了CD蛋白质的表达,在含有UPRT基因的婴儿双歧杆菌上清液中发现了UPRT蛋白质的表达。黑色素瘤细胞的低存活率证明了pTRKH2-PsT/CD、pTRKH2-PsT/UPRT自杀基因治疗系统对黑色素瘤的显著杀伤作用。结论 肿瘤厌氧靶向双自杀基因治疗系统pTRKH2-PsT/CD、pTRKH2-PsT/UPRT构建成功并显示出杀伤肿瘤细胞的作用。     

The growth of brain tumors can be suppressed by multiple transplantation of mesenchymal stem cells expressing cytosine deaminase

Suicide genes have recently emerged as an attractive alternative therapy for the treatment of various types of intractable cancers. The efficacy of suicide gene therapy relies on efficient gene delivery to target tissues and the localized concentration of final gene products. Here, we showed a potential ex vivo therapy that used mesenchymal stem cells (MSCs) as cellular vehicles to deliver a bacterial suicide gene, cytosine deaminase (CD) to brain tumors. MSCs were engineered to produce CD enzymes at various levels using different promoters. When co‐cultured, CD‐expressing MSCs had a bystander, anti‐cancer effect on neighboring C6 glioma cells in proportion to the levels of CD enzymes that could convert a nontoxic prodrug, 5‐fluorocytosine (5‐FC) into cytotoxic 5‐fluorouracil (5‐FU) in vitro. Consistent with the in vitro results, for early stage brain tumors induced by intracranial inoculation of C6 cells, transplantation of CD‐expressing MSCs reduced tumor mass in proportion to 5‐FC dosages. However, for later stage, established tumors, a single treatment was insufficient, but only multiple transplantations were able to successfully repress tumor growth. Our findings indicate that the level of total CD enzyme activity is a critical parameter that is likely to affect the clinical efficacy for CD gene therapy. Our results also highlight the potential advantages of autograftable MSCs compared with other types of allogeneic stem cells for the treatment of recurrent glioblastomas through repetitive treatments.