缺氧诱导因子-1α基因沉默对食管鳞癌细胞体外生长的影响

目的:探讨食管鳞癌细胞中缺氧诱导因子-1α(HIF-1α)基因与食管鳞癌细胞增殖活力和细胞周期的关系。方法:以RNA干扰方法构建出HIF-1α基因沉默食管鳞癌细胞株,通过Westernblot检测HIF-1α基因在细胞中的表达,通过流式细胞术分析了解HIF-1α基因沉默后细胞周期的变化,通过细胞增殖实验观察HIF-1α基因沉默细胞与对照细胞、模拟缺氧细胞增殖活性的差异。结果:细胞增殖实验发现沉默HIF-1α基因后的Eca-109细胞增殖活力较对照细胞明显低下,为对照细胞的62.6%(0.4768±0.1743vs0.7611±0.2165,P=0.012),流式细胞仪分析表明,HIF-1α基因沉默后的Eca-109细胞与对照细胞相比,G1/G0期细胞明显增加(P<0.05),G2/M期细胞变化不大,S期细胞比例明显减少。结论:核糖核酸干扰HIF-1α的表达后,能抑制鳞癌细胞的增殖活力,并可能阻滞肿瘤细胞周期,抑制HIF-1α的表达,有可能导致肿瘤生长的抑制。     

Variability in infectivity of primary cell cultures of human brain tumors with HSV-1 amplicon vectors

We investigated the variability in infectivity of cells in primary brain tumor samples from different patients using an HSV-1 amplicon vector. We studied the infectivity of HSV-1 amplicon vectors in tumor samples derived from neurosurgical resections of 20 patients. Cells were infected with a definite amount of HSV-1 amplicon vector HSV-GFP. Transduction efficiency in primary tumor cell cultures was compared to an established human glioma line. Moreover, duration of transgene expression was monitored in different tumor cell types. All primary cell cultures were infectable with HSV-GFP with variable transduction efficiencies ranging between 3.0 and 42.4% from reference human Gli36 Delta EGFR glioma cells. Transduction efficiency was significantly greater in anaplastic gliomas and meningiomas (26.7+/-17.4%) compared to more malignant tumor types (glioblastomas, metastases; 11.2+/-8.5%; P=0.05). To further investigate the possible underlying mechanism of this variability, nectin-1/HevC expression was analyzed and was found to contribute, at least in part, to this variability in infectability. The tumor cells expressed the exogenous gene for 7 to 61 days with significant shorter expression in glioblastomas (18+/-13 d) compared to anaplastic gliomas (42+/-24 d; P<0.05). Interindividual variability of infectivity by HSV-1 virions might explain, at least in part, why some patients enrolled in gene therapy for glioblastoma in the past exhibited a sustained response to HSV-1-based gene- and virus therapy. Infectivity of primary tumor samples from respective patients should be tested to enable the development of efficient and safe herpes vector-based gene and virus therapy for clinical application.     

Dendritic cells transduced with HSV-1 amplicons expressing prostate-specific antigen generate antitumor immunity in mice

There is currently much interest in generating cytotoxic T lymphocyte (CTL) responses against tumor antigens as a therapy for cancer. This work describes a novel gene transfer technique utilizing dendritic cells (DCs), an extremely potent form of antigen-presenting cell (APC), and herpes simplex virus-1 (HSV-1) amplicons. HSV-1 amplicons are plasmid-based viral vectors that are packaged into HSV-1 capsids, but lack viral coding sequences. Amplicon vectors have been constructed that encode the model tumor antigen ovalbumin (HSV-OVA) and human prostate-specific antigen (HSV-PSA), a protein that is expressed specifically in prostate epithelium and prostate carcinoma cells. These amplicons were packaged using a helper virus-free system that produces vector stocks that are devoid of contaminating cytotoxic helper virus. Transduction of DCs with HSV-OVA or HSV-PSA and co-culture with CTL hybridomas results in specific activation, indicating that transduced DCs express these transgenes and process the tumor antigens for class I MHC presentation to CTL. Mice immunized with HSV-PSA-transduced DCs generate a specific CTL response that can be detected in vitro by a (51)Cr-release assay and are protected from challenge with tumors that express PSA. These results indicate that DCs transduced with HSV-1 amplicon vectors may provide a tool for investigation of the biology of CTL activation by DCs and a new modality for immunotherapy of cancer.     

川芎嗪和siRNA沉默转化生长因子β1干预大鼠肝星状细胞结缔组织生长因子的表达

背景：作者前期研究发现川芎嗪可以通过抑制肝星状细胞的增殖、阻抑p38MARK信号通路、下调结缔组织生长因子的表达等多途径发挥抗肝纤维化的作用。一般认为转化生长因子β1是促进纤维化发生最重要的细胞因子,结缔组织生长因子是转化生长因子β1的下游效应介质,siRNA靶向抑制转化生长因子β1可能成为治疗肝纤维化的新方法。目的：观察川芎嗪及化学合成的siRNA转化生长因子β1对大鼠肝星状细胞结缔组织生长因子表达的影响。方法：体外培养大鼠肝星状细胞,从3条siRNA转化生长因子β1中筛选一条有效的基因沉默片段,然后利用脂质体转染试剂共同转染培养24h的细胞作为转染组,并设计空白对照组、转染试剂组、川芎嗪组及联合治疗组。结果与结论：与空白对照组相比,转染组、川芎嗪组、联合治疗组Ⅰ、Ⅲ型胶原及结缔组织生长因子mRNA表达均下调（P〈0.05）。在转染组、川芎嗪组及联合治疗组,结缔组织生长因子蛋白表达均下调（P〈0.05）;培养上清液中Ⅰ型胶原和Ⅲ型胶原含量均降低（P〈0.05）。结果表明,siRNA沉默转化生长因子β1基因能下调结缔组织生长因子的表达,减少Ⅰ、Ⅲ型胶原的表达。川芎嗪也能下调结缔组织生长因子的表达,但对Ⅰ、Ⅲ型胶原表达的抑制作用更加显著,提示川芎嗪抗肝纤维化可能是多种作用靶点。     

针对表皮生长因子受体基因RNA干扰质粒表达载体的构建

目的:表皮生长因子受体(EGFR)是一种酪氨酸激酶跨膜受体,人类的多种恶性肿瘤的发生与表皮生长因子受体过度表达有关。EGFR已成为阳性表达肿瘤的重要治疗靶标。在哺乳动物细胞中,RNA干扰是通过与目的基因特异互补的21-23个硷基的小双链RNA来抑制该基因的表达。有研究表明表达小发夹RNA的载体能诱导产生更好的RNA干扰效果。本实验通过向pSIREN-Shuttle质粒插入一段可被转录成小发夹RNA的双链寡核苷酸序列(其中含有于EGFR基因序列相同的19nt序列)重构了RNAi质粒表达载体。通过细胞转染评价该载体对人鼻咽癌细胞株(HNE1)EGFR基因的mRNA表达抑制效果。结果显示HNE1细胞的EGFR基因mRNA被明显抑制。提示shRNA质粒表达载体介导对EGFR基因的RNA干扰可能是鼻咽癌干预治疗的一种有效手段。     

Regulation of signaling phosphoproteins by epidermal growth factor and Iressa (ZD1839) in human endometrial cancer cells that model type I and II tumors

To understand how type I and II endometrial tumors uniquely respond to tyrosine kinase inhibitor treatments, we evaluated the signaling pathways of epidermal growth factor (EGF) receptor (EGFR) under the effects of EGF and Iressa (ZD1839, gefitinib) using Ishikawa H and Hec50co cells that model type I and II endometrial carcinomas, respectively. The cells were assayed for the expression of EGFR and both cell lines express an average of 100,000 EGFR per cell; however, Ishikawa H cells express higher levels of HER-2/neu compared with Hec50co cells (1.38 x 10(5) compared with 2.04 x 10(4), respectively). Using the Kinetworks multi-immunoblotting approach, which profiles 31 signaling phosphoproteins, the most striking result was that Hec50co cells show a higher number of basal phosphorylated sites compared with Ishikawa H cells. Furthermore, we identified targets of Iressa treatment in both cell lines. Iressa, at a dose of 1 micromol/L, blocked the autophosphorylation of EGFR in Ishikawa H and Hec50co cells with some distinctive effects on downstream effectors. Nevertheless, in both cell lines, EGF stimulated and Iressa blocked the major EGFR target mitogen-activated protein kinases extracellular signal-regulated kinase 1 and 2 equally. The high basal phosphorylation of numerous signaling molecules in Hec50co cells that were not inhibited by Iressa indicates that other growth factor pathways are active in addition to EGFR. We conclude that endometrial cancer cells that model type I and II carcinomas have the capacity to respond to EGFR inhibition as a therapeutic strategy; however, the response of the more aggressive type II tumors may be limited by the constitutive activation of other signaling pathways.     

Improved herpes simplex virus type 1 amplicon vectors for proportional coexpression of positron emission tomography marker and therapeutic genes

For the development of efficient and safe gene therapy protocols for clinical application it is desirable to determine the tissue dose of vector-mediated therapeutic gene expression noninvasively in vivo. The herpes simplex virus type 1 thymidine kinase gene (HSV-1-tk) has been shown to function as a marker gene for the direct noninvasive in vivo localization of thymidine kinase (TK) expression by positron emission tomography (PET). Using bicistronic or multicistronic gene-expressing cassettes with tk as the PET marker gene, the quantitative analysis of tk gene expression may indirectly indicate the distribution and the level of expression of linked and proportionally coexpressed genes. Here, we describe the construction and functional evaluation of HSV-1 amplicon vectors mediating proportional coexpression of HSV-1-tk as PET marker gene and the enhanced green fluorescent protein gene (gfp) as proof of principle and cell culture marker gene and the Escherichia coli cytosine deaminase (cd) as therapeutic gene. Several double-/triple-gene constructs expressing HSV-1-tk, gfp, and E. coli cd were engineered based on gene fusion or the use of an internal ribosome entry site (IRES). Functional analysis in cell culture (green fluorescent protein [GFP] fluorescence and sensitivity to the prodrugs ganciclovir [GCV] and 5-fluorocytosine [5-FC]) and Western blots were carried out after infection of proliferating rat 9L gliosarcoma and human Gli36 glioma cells with helper virus-free packaged HSV-1 amplicon vectors. To study the ability of PET to differentiate various levels of tk expression noninvasively in vivo, retrovirally transduced and selected populations of rat F98 and human Gli36dEGFR glioma cells with defined levels of proportionally coexpressed tk and gfp genes were grown as subcutaneous tumors in nude rats and nude mice, and tk imaging by PET was performed. To study HSV-1 amplicon vector-mediated gene coexpression in vivo, HSV-1 amplicon vectors bearing coexpression constructs were injected (4 x 10(7) to 1 x 10(8) transducing units) into subcutaneously growing Gli36dEGFR gliomas in nude animals, and tk imaging was performed 24 hr later. All vector constructs mediated GFP expression and sensitized 9L and Gli36 cells toward GCV- and 5-FC-mediated cell killing in a drug dose-dependent manner, respectively. The levels of gene expression varied depending on the location of the genes within the constructs indicating the influence of the IRES on the level of expression of the second gene. Moreover, functional proportional coexpression of the PET marker gene HSV-1-tk and the linked therapeutic E. coli cd gene was observed. In selected tumor cell populations, subtle IRES-dependent differences of tk gene expression could be noninvasively distinguished by PET with good correlation between quantitative assays for IRES-dependent attenuated GFP and TK expression in culture and in vivo. After infection of subcutaneously growing gliomas with HSV-1 amplicon vectors, various levels of TK expression were found ranging from 0.011-0.062 percentage injected dose per gram (%ID/g). These values were 4.0- to 5.7-fold lower than positive control tumor cells. TK expression could be imaged by PET in vivo even with the tk gene located at the weak position downstream from the IRES. In conclusion, these HSV-1 amplicon vectors carrying HSV-1-tk as PET marker gene and any linked therapeutic gene will serve an indirect noninvasive assessment of the distribution of therapeutic gene expression by PET. Monitoring the correlation between primary transduction and therapeutic efficiency of a given vector is highly desirable for the development of safe and efficient gene therapy and vector application protocols in clinical applications.     

Protein kinase C-{alpha} mediates epidermal growth factor receptor transactivation in human prostate cancer cells

Progression of human prostate cancer to a malignancy that is refractory to androgen-ablation therapy renders the disease resistant to available treatment options and accounts for the high prostate cancer mortality rate. Epidermal growth factor receptor (EGFR) expression in human prostate cancer specimens increases with disease progression to androgen-refractory prostate cancer, and experimental models implicate EGFR-dependent signaling to Erk1/2 activation in the androgen-refractory prostate cancer phenotype. 12-O-Tetradecanoylphorbol-13-acetate (TPA)-induced Erk1/2 activation in human prostate cancer PC-3 cells is a paradigm of diacylglycerol-induced EGFR transactivation in androgen-independent prostate cancer. In this report, we establish an obligatory role for TPA-induced protein kinase C (PKC)-alpha activation in EGFR transactivation and signaling to Erk1/2 activation in PC-3 cells. TPA-regulated molecules include PKCs, PKDs, and Ras guanyl nucleotide-releasing proteins. The PKC-selective inhibitors GF109203X and Go6983 each blocked TPA-induced EGFR transactivation, indicating a requirement for PKC. PC-3 cells express four PKC isozymes. Prolonged bryostatin 1 treatment abrogated PKCalpha expression without altering expression levels of the other PKC isozymes. Pharmacologic PKCalpha "knockdown" abrogated TPA-induced Erk1/2 activation without affecting the EGF/EGFR-induced response, indicating that PKCalpha was required for EGFR transactivation but dispensable for signaling of ligand-activated EGFR to Erk1/2 activation. We corroborated this by showing that Go6976, which is a PKCalpha-selective inhibitor in PC-3 cells, likewise abolished TPA-induced Erk1/2 activation and did not inhibit EGF/EGFR-induced Erk1/2 activation. Go6976 had similar effects in DU145 cells, providing evidence for a common PKCalpha-dependent Erk1/2 activation mechanism in androgen-independent human prostate cancer cells of distinct genetic origin. These results constitute a rational basis for selective PKCalpha inhibition as a modality of prostate cancer therapy.     

Expression of epidermal growth factor (EGF)/transforming growth factor-alpha by human lung cancer cells determines their response to EGF receptor tyrosine kinase inhibition in the lungs of mice

Epidermal growth factor receptor (EGFR) has been extensively targeted in the treatment of non-small cell lung cancer, producing responses in a small number of patients. To study the role of ligand expression in mediating response to EGFR antagonism, we injected NCI-H441 [EGFR and EGF/transforming growth factor-alpha (TGF-alpha) positive] or PC14-PE6 (EGFR positive and EGF/TGF-alpha negative) human lung adenocarcinoma cells into the lungs of nude mice. We randomized the mice to receive treatment with the EGFR tyrosine kinase inhibitors gefitinib or AEE788 or vehicle. Treatment of mice bearing NCI-H441 but not PC14-PE6 lung tumors resulted in a significant reduction in primary tumor growth, pleural effusion, and lymph node metastasis. Immunohistochemical analyses revealed that NCI-H441 and PC14-PE6 cells expressed EGFR but that the expression of EGF/TGF-alpha was high in NCI-H441 cells and very low in PC14-PE6 cells. Consequently, EGFR was activated in both tumor and tumor-associated endothelial cells in the NCI-H441 tumors but not in the PC14-PE6 tumors. Antagonism of EGFR signaling by treatment of mice with AEE788 decreased proliferation and increased apoptosis of both tumor cells and tumor-associated endothelial cells in NCI-H441 tumors but not in PC14-PE6 tumors. However, after transfection of PC14-PE6 cells with TGF-alpha, lung tumors derived from the transfected cells expressed and activated EGFR in both tumor and tumor-associated endothelial cells and tumors responded to treatment with AEE788. Collectively, these results strongly suggest that the response of human lung cancers growing orthotopically in mice to the inhibition of EGFR signaling is determined by ligand (EGF/TGF-alpha) expression by tumor cells. Our findings provide an additional explanation for the susceptibility of lung cancers to treatment with EGFR tyrosine kinase inhibitors.     

The use of a double subgenomic Sindbis virus expression system to study mosquito gene function: effects of antisense nucleotide number and duration of viral infection on gene silencing efficiency

Recently we established a simple, effective antisense strategy using a double subgenomic Sindbis (dsSIN) virus expression system to study gene function in mosquitoes. In this study, we further elucidate the effects of antisense nucleotide number and duration of viral infection on mosquito gene silencing efficiency by the dsSIN virus expression system. Over 15 days post virus infection, the degree of parasite melanization was progressively reduced by more than 95%, 75% and 55% in the mosquito Armigeres subalbatus transduced with 600, 147 or 36 bases antisense RNA, targeted to the highly conserved copper binding region of the Ar. subalbatus prophenoloxidase I gene (As-pro-POI), respectively. As the duration of viral infection increased from day 3-15, the degree of parasite melanization progressively decreased in all mosquitoes transduced with antisense RNA, irrespective of the lengths of antisense RNA. Progressive loss of parasite melanization function was found to correlate with down regulation of As-pro-PO expression at both the mRNA and protein activity levels, and reductions in virus titres in mosquitoes transduced with antisense RNA. A small pro-PO RNA (c. twenty-five nucleotides) was identified in mosquitoes transduced with antisense RNA. These data suggest that As-pro-POI gene expression is knocked down by degrading the As-pro-POI mRNA through the RNAi pathway. In conclusion, our study demonstrates that even a short antisense RNA (thirty-six bases) can cause silencing of the As-pro-POI gene, and the effects of endogenous gene silencing by dsSIN expression system on mosquito gene functions can be accumulative.     

A foamy virus vector system for stable and efficient RNAi expression in mammalian cells

The promise of the RNA interference (RNAi) technology is equally dependent on the efficiency and stability of gene silencing. The aim of the present study was the development of foamy virus (FV) vectors for stable RNAi, utilizing two potent RNA polymerase III (Pol III) promoters. Using green fluorescent protein as a target gene, we examined the efficiency of mouse U6 (mU6) and human H1 Pol III promoters in different human cell lines and mouse hematopoietic stem cells (HSCs) ex vivo and in vivo, following bone marrow transplantation. Both our mU6 and H1 FV vectors mediated very efficient gene silencing with as low as one vector copy per cell. However, transduction of human cell lines with FV vectors expressing short hairpin RNA from mU6 led to the gradual elimination of cells in culture, as opposed to H1-harboring cells, underscoring the importance of the expression system or cellular context in the evaluation of the overall RNAi effects. The efficiency and stability of the H1 vectors were further shown by the successful silencing of BCR-ABL in K562 cells. Accordingly, mU6 vectors induced efficient and stable gene silencing in mouse HSCs following bone marrow transplantation. Our work is the first in vivo study on the efficiency and stability of RNAi gene silencing in HSCs with FV vectors, currently a safe alternative for viral gene transfer.     

Spatial and temporal expression of herpes simplex virus type 1 amplicon-encoded genes: implications for their use as immunization vectors

There is great interest in developing new immunization vectors. Helper virus-free herpes amplicons, plasmid-based vectors that encode no viral gene products and have an extremely large coding capacity, are attractive viral vaccine candidates for expressing recombinant proteins in vivo for immunization. Earlier studies in mice, using amplicons encoding the gp120 protein of human immunodeficiency virus (HIV), resulted in strikingly robust cellular immune responses as measured by cytotoxicity and interferon gamma enzyme-linked immunospot assays. To begin to understand how such vectors function in vivo to generate an immune response, we used amplicons encoding reporter constructs including green fluorescent protein (GFP) and luciferase to examine the duration of expression after administration to mice. Luciferase expression, measured with the IVIS system from Xenogen/Caliper Life Sciences (Hopkinton, MA) and by enzymatic assays of tissue extracts, revealed that expression after injection of the HSVluc amplicons peaked earlier than 24 hr after injection into mice. HSVegfp injection resulted in peak accumulation of GFP 24 hr after administration in vivo. Thus, both reporter genes revealed a rather rapid and robust expression pattern of short duration. The short period of expression appears in part to be due to gene silencing. Examination of the cells transduced by amplicons encoding GFP and human B7.1 suggested that the amplicons transduce a variety of cells, including professional antigen-presenting cells. From this and previous work, we conclude that amplicons may engender a potent immune response by directly transducing dendritic cells as well as by cross-priming of antigen produced by other transduced host cells.     

Improved gene transfer efficiency to primary and established human pancreatic carcinoma target cells via epidermal growth factor receptor and integrin-targeted adenoviral vectors.

In this study we analyzed two ways of retargeting of Ad-vectors to human pancreatic carcinoma with the aim of enhancing the gene transfer efficiency. First, we analyzed the expression of the epidermal growth factor receptor (EGFR) on primary, as well as established pancreatic carcinoma cells by flow cytometry which revealed high expression levels of EGFR on the surface of these cells. We showed that EGFR-retargeted entry pathway using a bispecific fusion protein formed by a recombinant soluble form of truncated Coxsackie and Adenovirus Receptor (sCAR) genetically fused with human EGF (sCAR-EGF) redirects them to the EGFR leading to an enhanced gene transfer efficiency to pancreatic carcinoma cells. Since flow cytometry revealed absence of CAR expression, but the presence of at least one of both alphav integrins on the pancreatic carcinoma cells, a second way of targeting was investigated using a genetically modified Ad vector which has an RGD (Arg-Gly-Asp)-containing peptide inserted into the HI-loop of the fiber knob. This RGD targeted Ad (AdlucRGD) revealed efficient CAR-independent infection by allowing binding to cellular integrins resulting in a dramatic enhancement of gene transfer. These findings have direct relevance for Ad-vector based gene therapy strategies for pancreatic carcinoma.