慢病毒载体在RNA干扰中的应用进展

小分子RNA干扰技术是一种新兴的特异性地阻断某些基因表达的研究手段,在肿瘤、病毒感染,遗传病及其它疾病的治疗中均有广泛应用。慢病毒载体是一类来源于重组逆转录病毒的载体,由于具有可以感染非分裂期与分裂期细胞,容纳大的外源性目的基因片段,免疫反应小等特点,现已成为转移目的基因进入哺乳动物细胞的理想载体。将慢病毒载体应用于RNA干扰当中,可以特异性抑制哺乳动物的各类细胞中基因的表达,成为基因功能研究和基因治疗的有力手段。本文将试图对近期慢病毒载体在RNA干扰当中的应用的最新进展进行综述。     

Adenovirus expressing dual c-Met-specific shRNA exhibits potent antitumor effect through autophagic cell death accompanied by senescence-like phenotypes in glioblastoma cells

c-Met, a cognate receptor tyrosine kinase of hepatocyte growth factor, is overexpressed and/or mutated in number of tumors. Therefore, abrogation of c-Met signaling may serve as potential therapeutic targets. In this study, we generated Ads expressing single shRNA specific to c-Met (shMet) (dl/shMet4 and dl/shMet5) or dual shRNAs specific to c-Met (dl/shMet4+5); and examined the therapeutic potential of these newly engineered Ads in targeting c-Met, and delineated their mechanism of action in vitro and in vivo. Ads expressing shMet induced knock-down in c-Met, and phenotypically resulted in autophagy-like features including appearance of membranousvacuoles, formation of acidic vesicular organelles, and cleavage and recruitment of microtubule-associated protein1 light chain 3 to autophagosomes. Ads expressing shMet also suppressed Akt phosphorylation and increased number of senescence-related gene products including SM22, TGase II, and PAI-1. These changes resulted in inhibition of cell proliferation and G₂/M arrest of U343 cells. In vivo, intratumoral injection with dl/shMet4+5 resulted in a significant reduction of tumor growth with corresponding increasing overall survival. Histopathological analysis of these treated tumors revealed that Atg5 was highly up-regulated, indicating the therapeutic induction of autophagy. In sum, these results reveal that autophagic cell death induced by shMet-expressing Ads provide a novel strategy for targeting c-Met-expressing tumors through non-apoptotic mechanism of cell death.     

Inhibition of hepatitis B virus replication in 2.2.15 cells by expressed shRNA

Summary.  Hepatitis B virus (HBV) infection is a worldwide health problem. To determine whether RNA interference (RNAi) could inhibit ongoing HBV replication in 2.2.15 cells, we constructed shRNA-producing vector pU6P based on the mouse U6 RNA promoter and cloned 12 targeted sequences against HBV into the vector, resulting in a series of pU6-siHBV vectors. The recombinant vectors were transfected into 2.2.15 cells, HBsAg and HBeAg in cultured media were assayed using enzyme-linked immunosorbent assay at various days after transfection. The amount of HBV DNA in the culture medium was quantitated by real-time polymerase chain reaction. HBsAg and HBeAg expression were inhibited by 72.8 ± 5.4% ( P  = 0.00003) and 55.8 ± 6.2% ( P  = 0.000026), respectively, 4 days after transfection with pU6-siHBV5. The greatest inhibition of HBV DNA was decreased by approximately 1.9-fold ( P  = 0.013) on day 6 post transfection with pU6-siHBV11 compared with that of empty vector. No change was found for HBV protein expression and DNA replication on pU6-siGFP (negative control) transfected cells. Our data demonstrate that the transfection of HBV-targeted shRNA-producing vector in 2.2.15 cells could inhibit the HBV protein expression and HBV DNA replication specifically. RNAi may be considered as a potential antiviral approach for human HBV infection.     

核糖体蛋白S6 shRNA慢病毒载体的构建及其对肺腺癌A549细胞株增殖的影响

目的 探讨靶向抑制核糖体蛋白S6（rpS6）表达的短发夹RNA（short hairpin RNA, shRNA）慢病毒载体的构建方法及抑制rpS6表达对肺腺癌A549细胞株增殖的影响。方法 合成针对rpS6基因的双链寡核苷酸序列,插入质粒载体pGCsil-GFP,转化大肠杆菌细胞,测序鉴定插入片段;再通过293T细胞转染和慢病毒包装,收集浓缩病毒并感染肺腺癌A549细胞株。流式细胞技术分选强阳性表达绿色荧光蛋白(GFP)的细胞克隆,荧光定量PCR及Western blot检测rpS6基因的mRNA和蛋白干扰效率。体外利用CCK-8试剂盒定点检测细胞的光密度(OD)值,分析抑制rpS6表达对肺腺癌A549细胞株增殖能力的影响。结果 重组pGCsil-sh-rpS6-GFP质粒经测序鉴定示：插入序列与rpS6干扰序列完全符合,证实pGCsil-sh-rpS6-GFP质粒构建成功。sh-rpS6慢病毒稳定感染A549细胞株后,流式细胞技术分选GFP强阳性表达的细胞克隆比率为86.80%。荧光定量PCR与Western blot检测示： sh-rpS6组的mRNA和蛋白干扰效率分别为(79.72±6.83)%、（83.77±12.13)%。体外增殖实验示：与A549细胞相比,sh-rpS6组在各时间点的OD值较对照组均下降（均P<0.05）。结论 构建的sh-rpS6慢病毒载体能稳定、有效地抑制肺腺癌A549细胞株rpS6的表达,并有效减慢A549细胞株的增殖速度。     

Delivery of RNA interference triggers to sensory neurons in vivo using herpes simplex virus

Importance of the field: Pain is a hugely important area of research attracting considerable academic and commercial interest. However, the application of RNA interference (RNAi) to the study of nociceptive processes and the development of new analgesics has been limited by the specific challenges associated with the delivery of RNAi triggers to the cell bodies of sensory neurons in the dorsal root ganglia (DRG).Areas covered in this review: In the past five years, delivery of small-interfering RNA (siRNA) to the DRG and spinal cord has achieved effective and specific silencing of targeted genes in various animal models of pain. However, delivery of short-hairpin RNA (shRNA) or artificial microRNA (miRNA) to sensory neurons in vivo has not been feasible using most delivery systems currently available. What the reader will gain: Replication-defective vectors based on herpes simplex virus (HSV), which are particularly efficient at targeting DRG neurons, have been recently engineered to express shRNA and artificial miRNA. Whilst silencing induced by siRNA is transient and requires relatively high doses of silencing triggers, HSV-mediated expression of shRNA/miRNA in sensory neurons allows silencing of targeted genes for at least one week following a single injection.Take home message: The potential to use inducible or tissue-specific promoters and to simultaneously silence multiple gene targets, in addition to recent studies suggesting that artificial miRNAs may have improved safety profiles, hold clear advantages for the use of miRNA-based vectors for gene silencing in sensory neurons.     

Genetic reconstitution of tumorigenesis in primary intestinal cells

Animal models for human colorectal cancer recapitulate multistep carcinogenesis that is typically initiated by activation of the Wnt pathway. Although potential roles of both genetic and environmental modifiers have been extensively investigated in vivo, it remains elusive whether epithelial cells definitely require interaction with stromal cells or microflora for tumor development. Here we show that tumor development could be simply induced independently of intestinal microenvironment, even with WT murine primary intestinal cells alone. We developed an efficient method for lentiviral transduction of intestinal organoids in 3D culture. Despite seemingly antiproliferative effects by knockdown of adenomatous polyposis coli (APC), we managed to reproducibly induce APC-inactivated intestinal organoids. As predicted, these organoids were constitutively active in the Wnt signaling pathway and proved tumorigenic when injected into nude mice, yielding highly proliferative tubular epithelial glands accompanied by prominent stromal tissue. Consistent with cellular transformation, tumor-derived epithelial cells acquired sphere formation potential, gave rise to secondary tumors on retransplantation, and highly expressed cancer stem cell markers. Inactivation of p53 or phosphatase and tensin homolog deleted from chromosome 10, or activation of Kras, promoted tumor development only in the context of APC suppression, consistent with earlier genetic studies. These findings clearly indicated that genetic cooperation for intestinal tumorigenesis could be essentially recapitulated in intestinal organoids without generating gene-modified mice. Taken together, this in vitro model for colon cancer described herein could potentially provide unique opportunities for carcinogenesis studies by serving as a substitute or complement to the currently standard approaches.     

Increasing Resistance of Tubular Epithelial Cells to Apoptosis by shRNA Therapy Ameliorates Renal Ischemia-Reperfusion Injury

Renal tubular epithelial cells (TEC) die by apoptosis or necrosis in renal ischemia-reperfusion injury (IRI). Fas/Fas ligand-dependent fratricide is critical in TEC apoptosis, and Fas promotes renal IRI. Therefore, targeting Fas or caspase-8 may have therapeutic potential for renal injury in kidney transplant or failure. RNA silencing by short hairpin RNA (shRNA) is a novel strategy to down-regulate protein expression. Using this approach, silencing of Fas or caspase-8 by shRNA to prevent TEC apoptosis and IRI was evaluated. IRI was induced by renal artery clamping for 45 or 60 min at 32 degrees C in uninephrectomized C57BL/6 mice. Here, we showed that Fas or pro-caspase-8 expression was significantly knocked down in TEC by stable expression of shRNA, resulting in resistance to apoptosis induced by superoxide, IFN-gamma/TNF-alpha and anti-Fas antibody. Inferior vena cava delivery of pHEX-small interfering RNA targeting Fas or pro-caspase-8 resulted in protection of kidney from IRI, indicated by reduction of renal tubular injury (necrosis and apoptosis) and serum creatinine or blood urea nitrogen. Our data suggest that shRNA-based therapy targeting Fas and caspase-8 in renal cells can lead to protection of kidney from IRI. Attenuation of pro-apoptotic proteins using genetic manipulation strategies such as shRNA might represent a novel strategy to promote kidney allograft survival from rejection or failure.