RNA interference-based therapeutics for human immunodeficiency virus HIV-1 treatment: synthetic siRNA or vector-based shRNA?

Nanotechnology-enabled gene delivery for cancer and other genetic diseases

INTRODUCTION

Despite gene therapy is ideal for genetic abnormality-related diseases, the easy degradation, poor targeting, and inefficiency in entering targeted cells are plaguing the effective delivery of gene therapy. Viral and non-viral vectors have been used for delivering gene therapeutics in vivo by safeguarding nucleic acid agents to target cells and to reach the specific intracellular location. A variety of nanotechnology-enabled safe and efficient systems have been successfully developed to improve the targeting ability for effective therapeutic delivery of genetic drugs.

AREAS COVERED

In this review, we outline the multiple biological barriers associated with gene delivery process, and highlight recent advances to gene therapy strategy in vivo, including gene correction, gene silencing, gene activation and genome editing. We point out current developments and challenges exist of non-viral and viral vector systems in association with chemical and physical gene delivery technologies and their potential for the future.

EXPERT OPINION

This review focuses on the opportunities and challenges to various gene therapy strategy, with specific emphasis on overcoming the challenges through the development of biocompatibility and smart gene vectors for potential clinical application.

Editing out HIV: application of gene editing technology to achieve functional cure

Highly active antiretroviral therapy (HAART) successfully suppresses human immunodeficiency virus (HIV) replication and improves the quality of life of patients living with HIV. However, current HAART does not eradicate HIV infection because an HIV reservoir is established in latently infected cells and is not recognized by the immune system. The successful curative treatment of the Berlin and London patients following bone marrow transplantation inspired researchers to identify an approach for the functional cure of HIV. As a promising technology, gene editing-based strategies have attracted considerable attention and sparked much debate. Herein, we discuss the development of different gene editing strategies in the functional cure of HIV and highlight the potential for clinical applications prospects.

Virus-associated ribozymes and nano carriers against COVID-19

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a zoo tonic, highly pathogenic virus. The new type of coronavirus with contagious nature spread from Wuhan (China) to the whole world in a very short time and caused the new coronavirus disease (COVID-19). COVID-19 has turned into a global public health crisis due to spreading by close person-to-person contact with high transmission capacity. Thus, research about the treatment of the damages caused by the virus or prevention from infection increases everyday. Besides, there is still no approved and definitive, standardized treatment for COVID-19. However, this disaster experienced by human beings has made us realize the significance of having a system ready for use to prevent humanity from viral attacks without wasting time. As is known, nanocarriers can be targeted to the desired cells in vitro and in vivo. The nano-carrier system targeting a specific protein, containing the enzyme inhibiting the action of the virus can be developed. The system can be used by simple modifications when we encounter another virus epidemic in the future. In this review, we present a potential treatment method consisting of a nanoparticle-ribozyme conjugate, targeting ACE-2 receptors by reviewing the virus-associated ribozymes, their structures, types and working mechanisms.

siRNA Therapeutics for Protein Misfolding Diseases of the Central Nervous System

Nanoparticles have been used to deliver siRNA to tissues and cells to silence specific genes in diverse organisms. Research and clinical application of nanoparticles like liposomes for drug delivery requires targeting them to specific anatomic regions or cell types, while avoiding off-target effects or clearance by the liver, kidney, or the immune system. Delivery to the central nervous system (CNS) presents additional challenges to cross the blood-brain barrier (BBB) to specific cell types like neurons, astrocytes, or glia. Here, we describe the generation of three different liposomal siRNA delivery vehicles to the CNS using the thin film hydration method. Utilizing cationic or anionic liposomes protects the siRNA from serum nucleases and proteases en route. To deliver the siRNA specifically to the CNS, the liposomes are complexed to a peptide that acts as a neuronal address by binding to nicotinic acetylcholine receptors (nAchRs). When injected intravenously or instilled intranasally, these liposome-siRNA-peptide complexes (LSPCs) or peptide addressed liposome-encapsulated therapeutic siRNA (PALETS) resist serum degradation, effectively cross the BBB, and deliver siRNA to AchR-expressing cells to suppress protein expression in the CNS.

Nanoparticles-assisted delivery of antiviral-siRNA as inhalable treatment for human respiratory viruses: A candidate approach against SARS-COV-2

The current pandemic of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has challenged healthcare structures across the globe. Although a few therapies are approved by FDA, the search for better treatment options is continuously on rise. Clinical management includes infection prevention and supportive care such as supplemental oxygen and mechanical ventilatory support. Given the urgent nature of the pandemic and the number of companies and researchers developing COVID-19 related therapies, FDA has created an emergency program to move potential treatments with already approved drugs to patients as quickly as possible in parallel to the development of new drugs that must first pass the clinical trials. In this manuscript, we have reviewed the available literature on the use of sequence-specific degradation of viral genome using short-interfering RNA (siRNA) suggesting it as a possible treatment against SARS-CoV-2. Delivery of siRNA can be promoted by the use of FDA approved lipids, polymers or lipid-polymer hybrids. These nanoparticulate systems can be engineered to exhibit increased targetability and formulated as inhalable aerosols.

Galactose Functionalized Mesoporous Silica Nanoparticles As Delivery Vehicle in the Treatment of Hepatitis C Infection

DNA and RNA based antiviral strategies using nonviral vectors have shown better potential over the viral pathway due to the fewer chances of gene recombination and immunogenicity. In this work a mesoporous silica nanoparticle (MSN) based carrier system has been used for targeted delivery of shDNA molecule against the conserved 5'-untranslated region (UTR) in the RNA of a hepatitis C virus to inhibit its replication. The MSNs coated with amine and galactose could specifically target liver cells. Significant reduction (about 94%) of viral RNA level was achieved in HCV-JFH1 infectious cell culture compared to the control RNA levels directed the successful delivery and action of the shDNA. This study showed that Gal-AMSN can be used as a synthetic delivery vector to deliver the shDNA effectively for the treatment of HCV infection.

Recent advances of enterovirus 71 [Formula: see text] targeting Inhibitors

With CA16, enterovirus-71 is the causative agent of hand foot and mouth disease (HFMD) which occurs mostly in children under 5 years-old and responsible of several outbreaks since a decade. Most of the time, HFMD is a mild disease but can progress to severe complications such as meningitis, brain stem encephalitis, acute flaccid paralysis (AFP) and even death; EV71 has been identified in all severe cases. Therefore, it is actually one of the most public health issues that threatens children's life. [Formula: see text] is a protease which plays important functions in EV71 infection. To date, a lot of [Formula: see text] inhibitors have been tested but none of them has been approved yet. Therefore, a drug screening is still an utmost importance in order to treat and/or prevent EV71 infections. This work highlights the EV71 life cycle, [Formula: see text] functions and [Formula: see text] inhibitors recently screened. It permits to well understand all mechanisms about [Formula: see text] and consequently allow further development of drugs targeting [Formula: see text]. Thus, this review is helpful for screening of more new [Formula: see text] inhibitors or for designing analogues of well known [Formula: see text] inhibitors in order to improve its antiviral activity.

Lipopeptide Delivery of siRNA to the Central Nervous System

RNA interference is a relatively new tool used to silence specific genes in diverse biological systems. The development of this promising new technique for research and therapeutic use in studying and treating neurological diseases has been hampered by the lack of an efficient way to deliver siRNA transvascularly across the blood-brain barrier (BBB) to the central nervous system (CNS). Here we describe the generation of three different liposomal siRNA delivery vehicles to the CNS using the thin film hydration method. Utilizing cationic or anionic liposomes protects the siRNA from serum nucleases and proteases en route. To deliver the siRNA specifically to the CNS, the liposomes are complexed to a peptide that acts as a neuronal address by binding to nicotinic acetylcholine receptors (nAchRs). When injected intravenously, these liposome-siRNA-peptide complexes (LSPCs) or peptide addressed liposome encapsulated therapeutic siRNA (PALETS) resist serum degradation, effectively cross the BBB and deliver siRNA to AchR-expressing cells to suppress protein expression in the CNS.

The therapeutic landscape of HIV-1 via genome editing

Current treatment for HIV-1 largely relies on chemotherapy through the administration of antiretroviral drugs. While the search for anti-HIV-1 vaccine remain elusive, the use of highly active antiretroviral therapies (HAART) have been far-reaching and has changed HIV-1 into a manageable chronic infection. There is compelling evidence, including several side-effects of ARTs, suggesting that eradication of HIV-1 cannot depend solely on antiretrovirals. Gene therapy, an expanding treatment strategy, using RNA interference (RNAi) and programmable nucleases such as meganuclease, zinc finger nuclease (ZFN), transcription activator-like effector nuclease (TALEN), and clustered regularly interspaced short palindromic repeats/CRISPR-associated proteins (CRISPR-Cas9) are transforming the therapeutic landscape of HIV-1. TALENS and ZFNS are structurally similar modular systems, which consist of a FokI endonuclease fused to custom-designed effector proteins but have been largely limited, particularly ZFNs, due to their complexity and cost of protein engineering. However, the newly developed CRISPR-Cas9 system, consists of a single guide RNA (sgRNA), which directs a Cas9 endonuclease to complementary target sites, and serves as a superior alternative to the previous protein-based systems. The techniques have been successfully applied to the development of better HIV-1 models, generation of protective mutations in endogenous/host cells, disruption of HIV-1 genomes and even reactivating latent viruses for better detection and clearance by host immune response. Here, we focus on gene editing-based HIV-1 treatment and research in addition to providing  perspectives for refining these techniques.

Engineered Hydrogels for Local and Sustained Delivery of RNA-Interference Therapies

It has been nearly two decades since RNA-interference (RNAi) was first reported. While there are no approved clinical uses, several phase II and III clinical trials suggest the great promise of RNAi therapeutics. One challenge for RNAi therapies is the controlled localization and sustained presentation to target tissues, to both overcome systemic toxicity concerns and to enhance in vivo efficacy. One approach that is emerging to address these limitations is the entrapment of RNAi molecules within hydrogels for local and sustained release. In these systems, nucleic acids are either delivered as siRNA conjugates or within nanoparticles. A plethora of hydrogels has been implemented using these approaches, including both traditional hydrogels that have already been developed for other applications and new hydrogels developed specifically for RNAi delivery. These hydrogels have been applied to various applications in vivo, including cancer, bone regeneration, inflammation and cardiac repair. This review will examine the design and implementation of such hydrogel RNAi systems and will cover the most recent applications of these systems.

Recent advances in RNAi-based strategies for therapy and prevention of HIV-1/AIDS

RNA interference (RNAi) provides a powerful tool to silence specific gene expression and has been widely used to suppress host factors such as CCR5 and/or viral genes involved in HIV-1 replication. Newer nuclease-based gene-editing technologies, such as zinc finger nucleases (ZFN), transcription activator-like effector nucleases (TALEN) and the clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 system, also provide powerful tools to ablate specific genes. Because of differences in co-receptor usage and the high mutability of the HIV-1 genome, a combination of host factors and viral genes needs to be suppressed for effective prevention and treatment of HIV-1 infection. Whereas the continued presence of small interfering/short hairpin RNA (si/shRNA) mediators is needed for RNAi to be effective, the continued expression of nucleases in the gene-editing systems is undesirable. Thus, RNAi provides the only practical way for expression of multiple silencers in infected and uninfected cells, which is needed for effective prevention/treatment of infection. There have been several advances in the RNAi field in terms of si/shRNA design, targeted delivery to HIV-1 susceptible cells, and testing for efficacy in preclinical humanized mouse models. Here, we comprehensively review the latest advances in RNAi technology towards prevention and treatment of HIV-1.

Downregulation of VMP1 confers aggressive properties to colorectal cancer

Vacuole membrane protein 1 (VMP1) was recently found to be involved in the process of tumor metastasis and is also considered to play a vital role in balancing apoptosis and autophagy. In the present study, the expression of VMP1 in colorectal cancer and matched adjacent non‑cancerous tissues was evaluated by immunohistochemistry (IHC) for studying the role of VMP1 in the process of colorectal cancer. Kaplan‑Meier analysis and the log-rank test were used to calculate the correlation of classic clinicopathological characteristics related to survival and the expression of VMP1. In vitro, a VMP1 stable gene silencing cell model was constructed using a lentiviral vector. The invasive ability and proliferation of colorectal cancer cells were evaluated by Transwell and MTT assays, respectively, and the underlying signaling pathway was explored by western blotting. Additionally, drug susceptibility to cisplatin, oxaliplatin and 5-FU was tested before and after VMP1 knockout. Finally, an animal model was constructed to explore the role of VMP1 in the physiopathologic process of colorectal cancer. Our results indicated that VMP1 showed increased expression in the adjacent non-cancer tissues compared with that in the colorectal cancer tissues. For different stages of colorectal cancer, expression of VMP1 had a negative correlation with the malignancy of the cancer. In clinical research, we also found that the median survival of patients with low VMP1 expression was much shorter than the survival of patients with high expression. In vitro, after infection with the lentivirus, cells with VMP1 knockout gained significant aggressive properties in regards to invasion and proliferation, and the mechanisms may be related to the activation of the PI3K/Akt/ZO-1/E-cadherin pathway. We also found that shVMP1 cells were more sensitive to 5-FU, but not cisplatin and oxaliplatin. Finally, we found a higher number of formed nodules in nude mice after intraperitoneal injection with shVMP1 cells in the in vivo study.

RNA interference approaches for treatment of HIV-1 infection

HIV/AIDS is a chronic and debilitating disease that cannot be cured with current antiretroviral drugs. While combinatorial antiretroviral therapy (cART) can potently suppress HIV-1 replication and delay the onset of AIDS, viral mutagenesis often leads to viral escape from multiple drugs. In addition to the pharmacological agents that comprise cART drug cocktails, new biological therapeutics are reaching the clinic. These include gene-based therapies that utilize RNA interference (RNAi) to silence the expression of viral or host mRNA targets that are required for HIV-1 infection and/or replication. RNAi allows sequence-specific design to compensate for viral mutants and natural variants, thereby drastically expanding the number of therapeutic targets beyond the capabilities of cART. Recent advances in clinical and preclinical studies have demonstrated the promise of RNAi therapeutics, reinforcing the concept that RNAi-based agents might offer a safe, effective, and more durable approach for the treatment of HIV/AIDS. Nevertheless, there are challenges that must be overcome in order for RNAi therapeutics to reach their clinical potential. These include the refinement of strategies for delivery and to reduce the risk of mutational escape. In this review, we provide an overview of RNAi-based therapies for HIV-1, examine a variety of combinatorial RNAi strategies, and discuss approaches for ex vivo delivery and in vivo delivery.

Lipid nanoparticle delivery systems for siRNA-based therapeutics

Therapeutics based on small interfering RNA (siRNA) have a huge potential for the treatment of disease but requires sophisticated delivery systems for in vivo applications. Lipid nanoparticles (LNP) are proven delivery systems for conventional small molecule drugs with over eight approved LNP drugs. Experience gained in the clinical development of LNP for the delivery of small molecules, combined with an understanding of the physical properties of lipids, can be applied to design LNP systems for in vivo delivery of siRNA. In particular, cationic lipids are required to achieve efficient encapsulation of oligonucleotides; however, the presence of a charge on LNP systems can result in toxic side effects and rapid clearance from the circulation. To address these problems, we have developed ionizable cationic lipids with pKa values below 7 that allow oligonucleotide encapsulation at low pH (e.g., pH 4) and a relatively neutral surface at physiological pH. Further optimization of cationic lipids to achieve maximized endosomal destabilization following uptake has resulted in LNP siRNA systems that can silence genes in hepatocytes at doses as low as 0.005 mg siRNA/kg body weight in mouse models. These systems have been shown to be highly effective clinically, with promising results for the treatment of hypercholesterolemia and transthyretin-induced amyloidosis among others. More LNP siRNA therapeutics, targeting different tissues and diseases, are expected to become available in the near future.

RNA interference targeting enhancer of polycomb1 exerts anti-tumor effects in lung cancer

BACKGROUND AND AIM

Lung cancer is one of leading malignant tumor worldwide with a high mortality rate. A new therapy target, enhancer of polycomb1 (EPC1) knocked down by short hairpin RNA (shRNA) interference technology, for lung cancer was established to investigate its effects on lung cancer in present study.

METHODS

RNA interference technology was applied to down-regulate the expression of EPC1 by specific-shRNA with lentivirus vector in neoplastic human alveolar basal epithelial cells (A549 cells). The survival rate and apoptosis were respectively measured by MTT and Flow Cytometry to evaluate the effects of shRNA EPC1 on cells. Mice xenografts of HCT116 cells with shRNA EPC1 were also established to assess the effect on tumor growth. The levels of AKT and p65 were detected by western blotting.

RESULTS

The down-regulation of EPC1 by specific-shRNA with lentivirus vector was significantly decreased the survival rate and apoptosis of A549 cells, and the tumors in EPC1 shRNA transfection group had a significant lower size and weight compared with the ones with control shRNA. The protein expression of p-AKT and p65 was reduced by EPC1 shRNA in both in vitro and in vivo experiments.

CONCLUSION

Silencing EPC1 by shRNA technology had the inhibition effects on cell proliferation and tumor growth in lung cancer, which provided a new potential target for treatment of cancers.

Wound healing improvement with PHD-2 silenced fibroblasts in diabetic mice

BACKGROUND

Hypoxia-inducible factor 1α is the central regulator of the hypoxia-induced response which results in the up-regulation of angiogenic factors. Its activity is under precise regulation of prolyl-hydroxylase domain 2. We hypothesized that PHD2 silenced fibroblasts would increase the expression of angiogenic factors, which might contribute to the improvement of the diabetic wound healing.

MATERIALS AND METHODS

50 dB/db mice were employed and randomly assigned into five groups with 10 mice in each: group 1 (untreated cell), group 2 (PHD2 silenced cell), group 3 (L-mimosine treated cells), group 4 (nontargeting siRNA treated cells) and group 5 (sham control). Fibroblasts were cultivated from the dermis of mice in each group and treated with PHD2 targeting siRNA, L-mimosine and non-targeting siRNA respectively. A fraction of the fibroblasts were employed to verify the silencing rate of PHD2 after 48 hours. The autologous fibroblasts (treated and untreated) labeled with adenovirus-GFP were implanted around the wound (Φ6mm), which was created on the dorsum of each mouse. The status of wounds was recorded periodically. Ten days postoperatively, 3 mice from each group were sacrificed and wound tissues were harvested. Molecular biological examinations were performed to evaluate the expressions of cytokines. 28 days postoperatively, the remaining mice were sacrificed. Histological examinations were performed to evaluate the densities of GFP+ cells and capillaries.

RESULTS

The expression of PHD2 reduced to 12.5%, and the expressions of HIF-1α and VEGFa increased significantly after PHD2 siRNA treatment. With the increasing expressions of HIF-1α and VEGFa, the time to wound closure in group 2 was less than 2 weeks. Increased numbers of GFP+ cells and capillaries were observed in group 2.

CONCLUSION

PHD2 siRNA treatment not only increased the expression of HIF1α and VEGFa, but also improved the fibroblast proliferation. These effects might contribute to the improvement of the diabetic wound healing.

Newer gene editing technologies toward HIV gene therapy

Despite the great success of highly active antiretroviral therapy (HAART) in ameliorating the course of HIV infection, alternative therapeutic approaches are being pursued because of practical problems associated with life-long therapy. The eradication of HIV in the so-called "Berlin patient" who received a bone marrow transplant from a CCR5-negative donor has rekindled interest in genome engineering strategies to achieve the same effect. Precise gene editing within the cells is now a realistic possibility with recent advances in understanding the DNA repair mechanisms, DNA interaction with transcription factors and bacterial defense mechanisms. Within the past few years, four novel technologies have emerged that can be engineered for recognition of specific DNA target sequences to enable site-specific gene editing: Homing Endonuclease, ZFN, TALEN, and CRISPR/Cas9 system. The most recent CRISPR/Cas9 system uses a short stretch of complementary RNA bound to Cas9 nuclease to recognize and cleave target DNA, as opposed to the previous technologies that use DNA binding motifs of either zinc finger proteins or transcription activator-like effector molecules fused to an endonuclease to mediate sequence-specific DNA cleavage. Unlike RNA interference, which requires the continued presence of effector moieties to maintain gene silencing, the newer technologies allow permanent disruption of the targeted gene after a single treatment. Here, we review the applications, limitations and future prospects of novel gene-editing strategies for use as HIV therapy.

RNAi induces innate immunity through multiple cellular signaling pathways

BACKGROUND AIMS

Our previous results showed that the knockdown of woodchuck hepatitis virus (WHV) by RNA interference (RNAi) led to upregulation of interferon stimulated genes (ISGs) in primary hepatocytes. In the present study, we tested the hypothesis that the cellular signaling pathways recognizing RNA molecules may be involved the ISG stimulation by RNAi.

METHODS

Primary murine hepatocytes (PMHs) from wild type mice and WHV transgenic (Tg) mice were prepared and treated with defined siRNAs. The mRNA levels of target genes and ISGs were detected by real-time RT-PCR. The involvement of the signaling pathways including RIG-I/MDA5, PKR, and TLR3/7/8/9 was examined by specific inhibition and the analysis of their activation by Western blotting.

RESULTS

In PMHs from WHV Tg mice, specific siRNAs targeting WHV, mouse β-actin, and GAPDH reduced the levels of targeted mRNAs and increased the mRNA expression of IFN-β, MxA, and IP-10. The enhanced ISG expression by siRNA transfection were abolished by siRNA-specific 2'-O-methyl antisense RNA and the inhibitors 2-AP and chloroquine blocking PKR and other TLR-mediated signaling pathways. Furthermore, Western blotting revealed that RNAi results in an increase in PKR phosphorylation and nuclear translocation of IRF3 and NF-êB, indicating the possible role of IRF3 in the RNAi-directed induction of ISGs. In contrast, silencing of RIG-I and MDA5 failed to block RNAi-mediated MxA induction.

CONCLUSIONS

RNAi is capable of enhancing innate immune responses through the PKR- and TLR-dependent signaling pathways in primary hepatocytes. The immune stimulation by RNAi may contribute to the antiviral activity of siRNAs in vivo.

Lipopeptide delivery of siRNA to the central nervous system

RNA interference is a relatively new tool used to silence specific genes in diverse biological systems. The development of this promising new technique for research and therapeutic use in studying and treating neurological diseases has been hampered by the lack of an efficient way to deliver siRNA transvascularly across the blood-brain barrier (BBB) to the central nervous system (CNS). Here we describe a method for delivering siRNA to the CNS by complexing it to a peptide that acts as a neuronal address by binding to acetylcholine receptors (AchRs). Adding cationic liposomes to the complex protects it from serum nucleases and proteases en route. When injected intravenously, these liposome-siRNA-peptide complexes resist serum degradation, effectively cross the BBB, and deliver siRNA to AchR-expressing cells to suppress protein expression in the CNS.

Nanoparticle-based delivery of small interfering RNA: challenges for cancer therapy

During recent decades there have been remarkable advances and profound changes in cancer therapy. Many therapeutic strategies learned at the bench, including monoclonal antibodies and small molecule inhibitors, have been used at the bedside, leading to important successes. One of the most important advances in biology has been the discovery that small interfering RNA (siRNA) is able to regulate the expression of genes, by a phenomenon known as RNA interference (RNAi). RNAi is one of the most rapidly growing fields of research in biology and therapeutics. Much research effort has gone into the application of this new discovery in the treatment of various diseases, including cancer. However, even though these molecules may have potential and strong utility, some limitations make their clinical application difficult, including delivery problems, side effects due to off-target actions, disturbance of physiological functions of the cellular machinery involved in gene silencing, and induction of the innate immune response. Many researchers have attempted to overcome these limitations and to improve the safety of potential RNAi-based therapeutics. Nanoparticles, which are nanostructured entities with tunable size, shape, and surface, as well as biological behavior, provide an ideal opportunity to modify current treatment regimens in a substantial way. These nanoparticles could be designed to surmount one or more of the barriers encountered by siRNA. Nanoparticle drug formulations afford the chance to improve drug bioavailability, exploiting superior tissue permeability, payload protection, and the “stealth” features of these entities. The main aims of this review are: to explain the siRNA mechanism with regard to potential applications in siRNA-based cancer therapy; to discuss the possible usefulness of nanoparticle-based delivery of certain molecules for overcoming present therapeutic limitations; to review the ongoing relevant clinical research with its pitfalls and promises; and to evaluate critically future perspectives and challenges in siRNA-based cancer therapy.

Inhibition of RalA signaling pathway in treatment of non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is the most common type of lung cancer and relatively resistant to chemotherapy. The most prevalent molecular abnormality in NSCLC is the overactivation of K-Ras proto-oncogene; therefore, elucidating down-stream Ras signaling in NSCLC is significantly important in developing novel therapies against this malignancy. Our work indicates that RalA, an important effector of Ras, is activated in NSCLC cell lines. While RalA was also overactivated in fetal human broncho-epithelial cells, RalBP1 (Ral binding protein-1), an important down-stream effector of RalA, was expressed at higher levels in cancer cell lines. Aurora kinase-A (AKA), an upstream activator of RalA, was also found to be active only in malignant cells. The outcome of inhibition of RalA (by gene specific silencing using a lentivirus) on the malignant phenotype of A549 cells was also studied. While proliferation and invasiveness of A549 cells were reduced upon silencing RalA, apoptosis and necrosis were elevated in such conditions. Additionally, the in vivo tumorigenesis of A549 cells was reduced upon partial inhibition of RalA and AKA using pharmacological inhibitors. Finally, we were interested in evaluating the level of active RalA in the fraction of NSCLC cells expressing cancer stem cell markers. For this purpose cells with increased expression of CD44 were separated from A549 cells and compared with cells with low level of expression of this marker and an unsorted population. A significant enhancement of RalA activation in high CD44+ cells was found as potential evidence for involvement of RalA signaling in initiation of the neoplastic procedure and an important contributor for tumor maintenance in NSCLC. Further studies can reveal therapeutic, preventive and diagnostic value of RalA pathway in this deadly disease.

Considering RNAi experimental design in parasitic helminths

Almost a decade has passed since the first report of RNA interference (RNAi) in a parasitic helminth. Whilst much progress has been made with RNAi informing gene function studies in disparate nematode and flatworm parasites, substantial and seemingly prohibitive difficulties have been encountered in some species, hindering progress. An appraisal of current practices, trends and ideals of RNAi experimental design in parasitic helminths is both timely and necessary for a number of reasons: firstly, the increasing availability of parasitic helminth genome/transcriptome resources means there is a growing need for gene function tools such as RNAi; secondly, fundamental differences and unique challenges exist for parasite species which do not apply to model organisms; thirdly, the inherent variation in experimental design, and reported difficulties with reproducibility undermine confidence. Ideally, RNAi studies of gene function should adopt standardised experimental design to aid reproducibility, interpretation and comparative analyses. Although the huge variations in parasite biology and experimental endpoints make RNAi experimental design standardization difficult or impractical, we must strive to validate RNAi experimentation in helminth parasites. To aid this process we identify multiple approaches to RNAi experimental validation and highlight those which we deem to be critical for gene function studies in helminth parasites.

The effects of vascular endothelial growth factor C knockdown in esophageal squamous cell carcinoma

PURPOSE

We investigated the role of vascular endothelial growth factor C (VEGF-C) in esophageal squamous cell carcinoma (ESCC) by knocking down VEGF-C expression in the ESCC cell line EC9706.

METHODS

Immunohistochemistry and in situ hybridization techniques were used to detect the expression of VEGF-C expression in ESCC tissues. We also investigated the relationship between VEGF-C expression and lymph node metastasis. We designed a siRNA expression plasmid for VEGF-C and transfected it into EC9706 cells. Stable clones were selected, and VEGF-C expression was analyzed by RT-PCR and western blotting. Cells were inoculated into nude mice. The expression of VEGF-C in the resulting tumors was analyzed by immunohistochemistry and in situ hybridization.

RESULTS

VEGF-C is highly expressed in ESCC and correlated with lymph node metastasis, as high levels were observed in patients presenting with lymph node metastases relative to those who did not (P < 0.01). Transfection with VEGF-C-siRNA decreased the expression of VEGF-C mRNA and protein. ESCC cells stably transfected with VEGF-C-siRNA expressed very low levels of VEGF-C (P < 0.01 compared with control). This knockdown effect persisted when the cells were inoculated into nude mice and allowed to form tumors.

CONCLUSIONS

The siRNA-targeted knockdown of VEGF-C led to a significant reduction in VEGF-C expression. This siRNA technique could be used for gene therapy in ESCC.

Humanized mouse models of HIV infection

Because of the limited tropism of HIV, in vivo modeling of this virus has been almost exclusively limited to other lentiviruses, such as simian immunodeficiency virus, that reproduce many important characteristics of HIV infection. However, there are significant genetic and biological differences among lentiviruses and some HIV-specific interventions are not effective against other lentiviruses in nonhuman hosts. For these reasons, much emphasis has recently been placed on developing alternative animal models that support HIV replication and recapitulate key aspects of HIV infection and pathogenesis in humans. Humanized mice, CD34+ hematopoietic progenitor cell transplanted immunodeficient mice, and in particular mice also implanted with human thymus/liver tissue (bone marrow liver thymus mice) that develop a functional human immune system, have been the focus of a great deal of attention as possible models to study virtually all aspects of HIV biology and pathogenesis. Humanized mice are systemically reconstituted with human lymphoid cells, offering rapid, reliable, and reproducible experimental systems for HIV research. Peripheral blood of humanized mice can be readily sampled longitudinally to assess reconstitution with human cells and to monitor HIV replication, permitting the evaluation of multiple parameters of HIV infection such as viral load levels, CD4+ T-cell depletion, immune activation, as well as the effects of therapeutic interventions. Of high relevance to HIV transmission is the extensive characterization and validation of the reconstitution with human lymphoid cells of the female reproductive tract and of the gastrointestinal tract of humanized bone marrow liver thymus mice that renders them susceptible to both vaginal and rectal HIV infection. Other important attributes of all types of humanized mice include: (i) their small size and cost that make them widely accessible; (ii) multiple cohorts of humanized mice can be made from multiple human donors and each cohort has identical human cells, permitting control of intragenetic variables; (iii) continuous de novo production of human immune cells from the transplanted CD34+ cells within each humanized mouse facilitates long-term experiments; (iv) both primary and laboratory HIV isolates can be used for experiments; and (v) in addition to therapeutic interventions, rectal and vaginal HIV prevention approaches can be studied. In summary, humanized mice can have an important role in virtually all aspects of HIV research, including the analysis of HIV replication, the evaluation of HIV restriction factors, the characterization of successful biomedical HIV prevention strategies, the evaluation of new treatment regimens, and the evaluation of novel HIV eradication strategies.

Dual functional RNA nanoparticles containing phi29 motor pRNA and anti-gp120 aptamer for cell-type specific delivery and HIV-1 inhibition

The potent ability of small interfering RNA (siRNA) to inhibit the expression of complementary RNA transcripts is being exploited as a new class of therapeutics for diseases including HIV. However, efficient delivery of siRNAs remains a key obstacle to successful application. A targeted intracellular delivery approach for siRNAs to specific cell types is highly desirable. HIV-1 infection is initiated by the interactions between viral glycoprotein gp120 and cell surface receptor CD4, leading to fusion of the viral membrane with the target cell membrane. Once HIV infects a cell it produces gp120 which is displayed at the cell surface. We previously described a novel dual inhibitory anti-gp120 aptamer-siRNA chimera in which both the aptamer and the siRNA portions have potent anti-HIV activities. We also demonstrated that gp120 can be used for aptamer mediated delivery of anti-HIV siRNAs. Here we report the design, construction and evaluation of chimerical RNA nanoparticles containing a HIV gp120-binding aptamer escorted by the pRNA of bacteriophage phi29 DNA-packaging motor. We demonstrate that pRNA-aptamer chimeras specifically bind to and are internalized into cells expressing HIV gp120. Moreover, the pRNA-aptamer chimeras alone also provide HIV inhibitory function by blocking viral infectivity. The Ab' pRNA-siRNA chimera with 2'-F modified pyrimidines in the sense strand not only improved the RNA stability in serum, but also was functionally processed by Dicer, resulting in specific target gene silencing. Therefore, this dual functional pRNA-aptamer not only represents a potential HIV-1 inhibitor, but also provides a cell-type specific siRNA delivery vehicle, showing promise for systemic anti-HIV therapy.

Selective gene silencing by viral delivery of short hairpin RNA

RNA interference (RNAi) technology has not only become a powerful tool for functional genomics, but also allows rapid drug target discovery and in vitro validation of these targets in cell culture. Furthermore, RNAi represents a promising novel therapeutic option for treating human diseases, in particular cancer. Selective gene silencing by RNAi can be achieved essentially by two nucleic acid based methods: i) cytoplasmic delivery of short double-stranded (ds) interfering RNA oligonucleotides (siRNA), where the gene silencing effect is only transient in nature, and possibly not suitable for all applications; or ii) nuclear delivery of gene expression cassettes that express short hairpin RNA (shRNA), which are processed like endogenous interfering RNA and lead to stable gene down-regulation. Both processes involve the use of nucleic acid based drugs, which are highly charged and do not cross cell membranes by free diffusion. Therefore, in vivo delivery of RNAi therapeutics must use technology that enables the RNAi therapeutic to traverse biological membrane barriers in vivo. Viruses and the vectors derived from them carry out precisely this task and have become a major delivery system for shRNA. Here, we summarize and compare different currently used viral delivery systems, give examples of in vivo applications, and indicate trends for new developments, such as replicating viruses for shRNA delivery to cancer cells.