人BNIP3真核表达载体和shRNA表达载体的构建及其对肝癌细胞自噬的影响

目的利用人BNIP3的真核表达载体和靶向BNIP3的shRNA表达载体,研究BNIP3过表达和封闭时对肝癌细胞自噬的影响。方法从人肝癌细胞系中,通过RT-PCR扩增人BNIP3基因编码区序列,酶切后插入pcDNA3.1-His-C载体,以此构建重组pcDNA3.1-BNIP3真核表达载体。同时构建靶向人BNIP3基因的shRNA表达载体pSilencer-BNIP3。分别经测序、酶切、RT-PCR和Western blot等方法对重组载体是否构建成功进行验证。并通过采用Western blot检测自噬标志物LC3蛋白的剪切,研究BNIP3过表达和抑制时对肝癌细胞自噬的影响。结果pcDNA3.1-BNIP3和pSilencer-BNIP3分别过表达BNIP3和抑制BNIP3的表达。BNIP3过表达能够显著增加肝癌细胞的自噬;BNIP3表达受到抑制时,肝癌细胞的自噬明显减少。结论成功构建了人BNIP3的真核表达载体pcDNA3.1-BNIP3和shRNA表达载体pSilencer-BNIP3,并在人肝癌细胞系中证实BNIP3对肝癌细胞自噬的促进作用。     

CCR4 dependent migration of Foxp3+ Treg cells to skin grafts and draining lymph nodes is implicated in enhanced graft survival in CD200tg recipients

We have previously reported that transgenic overexpression of CD200 in either mouse skin graft donors or recipients significantly enhances skin allograft survival. By focused microarray analysis we showed this enhanced graft survival is associated with increased expression of Foxp3, GITR, CTLA-4 and CCR4 mRNA, all genes related to T_reg cell induction/function, and of Gata3, IL-4, IL-5, IL-13, and somewhat surprisingly, of T-bet, INF-γ and granzyme b. Gene-specific real-time PCR and immunohistochemistry analysis confirmed an increase in Foxp3⁺ T_reg cells in both the skin grafts and draining lymph nodes (DLNs) of CD200^tg recipient mice at both 7/14 days post engraftment, as well as providing evidence for increased expression of the ligands for CCR4, CCL17 and CCL22 in both locations. Following lentivirus-mediated shRNA treatment of Dox-treated CD200^tg mice to attenuate expression of CCR4 mRNA, the increased localization of T_reg cells in skin/DLN of CD200^tg recipients was abolished, and the enhanced graft survival similarly reversed. We conclude that enhanced CCR4 dependent migration of Foxp3⁺ T_reg to grafted tissue and DLNs is an essential step in the graft prolongation afforded by overexpression of CD200.     

Multidrug resistance protein (MRP) 4 attenuates benzo[a]pyrene-mediated DNA-adduct formation in human bronchoalveolar H358 cells

Multi-drug resistance protein (MRP) 4, an ATP-binding cassette (ABC) transporter, has broad substrate specificity. It facilitates the transport of bile salt conjugates, conjugated steroids, nucleoside analogs, eicosanoids, and cardiovascular drugs. Recent studies in liver carcinoma cells and hepatocytes showed that MRP4 expression is regulated by the aryl hydrocarbon receptor (AhR) and nuclear factor E2-related factor 2 (Nrf2). The AhR has particular importance in the lung and is most commonly associated with the up-regulation of cytochrome P-450 (CYP)-mediated metabolism of benzo[a]pyrene (B[a]P) to reactive intermediates. Treatment of H358, human bronchoalveolar, cells with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or (−)-benzo[a]pyrene-7,8-dihydro-7,8-diol (B[a]P-7,8-dihydrodiol), the proximate carcinogen of B[a]P, revealed that MRP4 expression was increased compared to control. This suggested that MRP4 expression might contribute to the paradoxical decrease in (+)-7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene-2′-deoxyguanosine ((+)-anti-trans-B[a]PDE-dGuo) DNA-adducts observed in TCDD-treated H358 cells. We have now found that decreased MRP4 expression induced by a short hairpin RNA (shRNA), or chemical inhibition with probenecid, increased (+)-anti-trans-B[a]PDE-dGuo formation in cells treated with (−)-B[a]P-7,8-dihydrodiol, but not the ultimate carcinogen (+)-anti-trans-B[a]PDE. Thus, up-regulation of MRP4 increased cellular efflux of (−)-B[a]P-7,8-dihydrodiol, which attenuated DNA-adduct formation. This is the first report identifying a specific MRP efflux transporter that decreases DNA damage arising from an environmental carcinogen.     

小鼠STAT4，STAT6基因shRNA真核表达质粒的构建及鉴定

目的:构建并鉴定小鼠信号转导子和转录激活因子4(STAT4),信号转导子和转录激活因子6(STAT6)具有发夹结构小干扰RNA(shRNA)表达质粒.方法:根据STAT4和STAT6基因mRNA序列,在体外分别合成有小发夹结构的2条STAT4特异性寡核苷酸序列,2条STAT6特异性寡核苷酸序列,退火后与线性化pGenesil-3质粒连接,转化感受态细胞DH5α,扩增,纯化得到所需质粒.同时设计构建分别针对小鼠甘油醛-3-磷酸脱氢酶(GAPDH)的干扰质粒作为阳性对照,不具有基因同源性的非特异性基因的质粒作为阴性对照序列.通过酶切后琼脂糖凝胶电泳和基因测鉴定纯化质粒分子量及插入片段的序列.结果:经限制性酶切和测序鉴定分析证实基因插入正确,与设计的序列完全相符.结论:成功构建了针对小鼠STAT4,STAT6基因的发夹结构小干扰RNA表达载体.为今后利用基因沉默技术从转录后水平抑制STAT4,STAT6的研究奠定基础.     

Enhanced self-renewal capability in hepatic stem/progenitor cells drives cancer initiation

BACKGROUND & AIMS: Transformed hematopoietic stem/progenitor cells with an enhanced or acquired self-renewal capability function as leukemic stem cells. In a variety of solid cancers, stem/progenitor cells could be also targets of carcinogenesis. However, it remains unclear whether disruption of stem cell function directly contributes to cancer initiation. We sought to elucidate the mechanisms of self-renewal in hepatic stem/progenitor cells and the relation between stem cell function and hepatocarcinogenesis. METHODS: Functional analyses of polycomb-group protein Bmi1 and Wnt/beta-catenin, the molecules that are responsible for the self-renewal capability of many types of stem cells, were conducted in c-Kit(-)CD29(+)CD49f(+/low)CD45(-)Ter-119(-) hepatic stem/progenitor cells using retrovirus- or lentivirus-mediated gene transfer. The tumorigenicity of these cells transduced with the indicated retroviruses was also assessed by transplantation into nonobese diabetic/severe combined immunodeficient mice. RESULTS: Forced expression of Bmi1 and constitutively active beta-catenin mutant similarly promoted the self-renewal of hepatic stem/progenitor cells. The transplantation of Bmi1- or beta-catenin-transduced cells clonally expanded from single hepatic stem/progenitor cells produced tumors, which exhibited the histologic features of combined hepatocellular and cholangiocarcinoma. CONCLUSIONS: These observations imply that the dysregulated self-renewal of hepatic stem/progenitor cells serves as an early event in hepatocarcinogenesis, and they highlight the important roles of Bmi1 and the Wnt/beta-catenin pathway in regulating the self-renewal of normal or cancer stem cells in liver.     

The suppression of lung tumorigenesis by aerosol-delivered folate–chitosan-graft-polyethylenimine/Akt1 shRNA complexes through the Akt signaling pathway

RNA interference (RNAi) represents a promising new approach to the inhibition of gene expression in vitro and in vivo, and has therapeutic potential for human diseases. Efficient delivery of small interfering RNA (siRNA) or small hairpin RNA (shRNA) is a critical concern in RNAi studies. Here we report the development of a new polymeric gene carrier for cancer cell-targeting, designed to enhance the intracellular delivery of shRNA and reduce cytotoxicity. Folate–chitosan-graft-polyethylenimine (FC-g-PEI) copolymer was prepared by an imine reaction between periodate-oxidized folate–chitosan (FC) and low molecular weight polyethylenimine (PEI). FC-g-PEI copolymer was investigated as a potential cancer cell-targeting gene carrier. The composition of FC-g-PEI was characterized using ¹H nuclear magnetic resonance (¹H NMR), and particle size and zeta potential of FC-g-PEI/shRNA complexes were measured using dynamic light scattering (DLS). FC-g-PEI showed good shRNA condensation ability and high protection of shRNA from nuclease attack. It also exhibited lower cytotoxicity compared to PEI 25K control, and showed good cancer cell-targeting ability. Furthermore, aerosol delivery of FC-g-PEI/Akt1 shRNA complexes suppressed lung tumorigenesis in a urethane-induced lung cancer model mouse through the Akt signaling pathway. Together, these results suggest that FC-g-PEI may be useful for shRNA-based gene therapy.     

短发夹RNA沉默促肝细胞再生磷酸酶-3基因表达对乳腺癌MCF-7细胞生长和侵袭能力的影响

目的构建以促肝细胞再生磷酸酶-3（PRL-3）为靶基因的短发夹状小干扰RNA（short hairpin RNA,shRNA）表达载体,并探讨PRL-3-shRNA表达载体对人乳腺癌MCF-7细胞增殖、凋亡和侵袭能力的影响。方法 构建PRL-3基因特异性shRNA表达载体,使用脂质体法将PRL-3-shRNA表达载体转染入MCF-7细胞。采用Real-ti me PCR和Western blot分别检测转染后MCF-7细胞中PRL-3基因mRNA和蛋白的表达;运用四甲基偶氮唑蓝（methyl thiazolyl tetrazolium,MTT）比色法检测转染后MCF-7细胞的增殖水平,用流式细胞仪检测细胞凋亡的情况;采用Transwell小室法检测细胞侵袭力变化。计量资料采用单因素方差分析或重复测量方差分析。结果 酶切鉴定和测序分析证实PRL-3-shRNA表达载体成功构建。转染成功后,shRNA-1~3组PRL-3基因mRNA表达分别为（0.31±0.27）、（0.15±0.14）和（0.31±0.03）,与空白组和阴性组（1.00±0.00、0.98±0.18）相比,差异有统计学意义（P〈0.05）。PRL-3-shRNA-2组PRL-3蛋白的表达量明显低于阴性组和空白组（0.50±0.02比0.91±0.03和0.89±0.02,P〈0.05）;PRL-3-shRNA-2转染入MCF-7细胞后能明显降低其增殖水平（P〈0.05）;PRL-3-shRNA-2组凋亡率明显高于空白组和阴性组[（8.37±1.85）%比（1.60±1.58）%和（0.16±0.05）%,P〈0.05];Transwell小室侵袭实验显示,PRL-3-shRNA-2组穿膜细胞数明显低于阴性组和空白组（P〈0.05）。结论 沉默PRL-3基因表达可抑制MCF-7细胞的增殖,促进凋亡,抑制其侵袭能力     

大鼠野生型TRAF6基因和TRAF6 shRNA表达质粒的构建及鉴定

目的:构建大鼠野生型肿瘤坏死因子受体相关因子6(tumor necrosis factor receptor-associated factor 6,TRAF6)基因及其特异性短发卡状小干涉RNA(shRNA)真核表达质粒,并观察其在大鼠肾小球系膜细胞(GMC)中过表达和沉默TRAF6基因的情况?方法:用DNA重组技术将针对大鼠TRAF6基因的CDS区序列(加HA标签)和针对其不同位点所设计的3种shRNA序列分别克隆到pcDNA3.1及pGenesil-1/GFP真核表达质粒中?在酶切鉴定及序列测定正确后,用NeonTM电转仪,将上述质粒分别转染入培养的大鼠GMC中,然后用Western blot检查HA-TRAF6融合蛋白的表达情况,同时筛选最有效的TRAF6 shRNA?结果:限制性酶切及核酸序列分析确证,上述TRAF6基因过表达和shRNA表达质粒均构建成功?Western blot显示,构建的pcDNA3.1-HA-TRAF6质粒能在大鼠GMC中表达,且TRAF6 shRNA-1具有最佳的沉默效率?结论:本实验成功构建了大鼠野生型TRAF6真核表达质粒及其特异性的shRNA表达载体,这为今后进一步研究TRAF6基因的生物学功能提供了实验基础?