Intravenous, non-viral RNAi gene therapy of brain cancer

MicroRNA based theranostics for brain cancer: basic principles

BACKGROUND

Because of the complexity of the blood-brain barrier (BBB), brain tumors, especially the most common and aggressive primary malignant tumor type arising from the central nervous system (CNS), glioblastoma, remain an essential challenge regarding diagnostic and treatment. There are no approved circulating diagnostic or prognostic biomarkers, nor novel therapies like immune checkpoint inhibitors for glioblastoma, and chemotherapy brings only minimal survival benefits. The development of molecular biology led to the discovery of new potential diagnostic tools and therapeutic targets, offering the premise to detect patients at earlier stages and overcome the current poor prognosis.

MAIN BODY

One potential diagnostic and therapeutic breakthrough might come from microRNAs (miRNAs). It is well-known that miRNAs play a role in the initiation and development of various types of cancer, including glioblastoma. The review aims to answer the following questions concerning the role of RNA theranostics for brain tumors: (1) which miRNAs are the best candidates to become early diagnostic and prognostic circulating biomarkers?; (2) how to deliver the therapeutic agents in the CNS to overcome the BBB?; (3) which are the best methods to restore/inhibit miRNAs?

CONCLUSIONS

Because of the proven roles played by miRNAs in gliomagenesis and of their capacity to pass from the CNS tissue into the blood or cerebrospinal fluid (CSF), we propose miRNAs as ideal diagnostic and prognostic biomarkers. Moreover, recent advances in direct miRNA restoration (miRNA mimics) and miRNA inhibition therapy (antisense oligonucleotides, antagomirs, locked nucleic acid anti-miRNA, small molecule miRNA inhibitors) make miRNAs perfect candidates for entering clinical trials for glioblastoma treatment.

Doxorubicin and anti-VEGF siRNA co-delivery via nano-graphene oxide for enhanced cancer therapy in vitro and in vivo

BACKGROUND

Graphene oxide (GO) has attracted intensive interest in biological and medical fields in recent years due to its unique physical, chemical, and biological properties. In our previous work, we proved that GO could deliver small interfering RNA (siRNA) into cells and downregulate the expression of the desired gene.

METHODS

This study investigated the potential of a modified GO nanocarrier for co-delivery of siRNA and doxorubicin (DOX) for enhanced cancer therapy. Fourier transform infrared spectroscopy, laser particle size analyzer, UV-visible spectroscopy, gel electrophoresis retardation, and in vitro release assay were studied.

RESULTS

The results of real-time polymerase chain reaction revealed that the expression of vascular endothelial growth factor (VEGF) mRNA was decreased 46.84%±3.72% (mean ± SD). Enzyme-linked immunosorbent assay indicated that the expression of VEGF protein was down-regulated to 52.86%±1.10% (mean ± SD) in vitro. In vivo tumor growth assay GO-poly-l-lysine hydrobromide/folic acid (GPF)/DOX/siRNA exhibited gene silencing and tumor inhibition (66.95%±2.35%, mean ± SD) compared with naked siRNA (1.62%±1.47%, mean ± SD) and DOX (33.63%±5.85%, mean ± SD). GPF/DOX/siRNA exhibited no testable cytotoxicity.

CONCLUSION

The results indicated that co-delivery of siRNA and DOX by GPF could be a promising application in tumor clinical therapy.

Tumor-suppressing miR-141 gene complex-loaded tissue-adhesive glue for the locoregional treatment of hepatocellular carcinoma

microRNAs (miRNAs) regulate gene expression post-transcriptionally and have been extensively tested as therapeutic molecules against several human diseases. In vivo delivery of miRNAs needs to satisfy the following conditions: safety, efficiency, and long-term therapeutic effectiveness. To satisfy these conditions, we developed a tissue-adhesive nucleotide-polymer complex (NPX-glue) for in vivo delivery of miRNAs to treat hepatocellular carcinoma (HCC). Methods: Polyallylamine (PAA), a cationic polymer, was mixed with tumor-suppressing miR-141 to form NPX and then mixed with partially oxidized alginate (OA) to form NPX-glue. Delivery efficiency of miR-141:NPX-glue was determined in cultured HCC cells and in an implanted HCC tumor model. In vivo tumor-suppressive effects of miR-141 on HCC were examined in mice upon intratumoral injection of miR-141:NPX-glue. Result: NPX-glue was generated by mixing of NPX with OA, which eliminated the inherent cytotoxic effect of NPX. NPX-glue led to the efficient delivery of miR-141 and plasmid to cultured cells and solid tumors in mice, where their expression was maintained for up to 30 days. Upon intratumoral injection of miR-141:NPX-glue, the growth of the tumors was dramatically retarded in comparison with the negative control, NCmiR:NPX-glue, (p < 0.05). Molecular examination proved miR-141:NPX-glue efficiently regulated the target genes including MAP4K4, TM4SF1, KEAP1, HDGF, and TIAM1 and finally induced apoptosis of cancer tissues. Conclusion: Here, we show that NPX-glue delivers therapeutic miR-141 to solid tumors in a safe, stable, and long-term manner and prove that locoregional treatment of HCC is possible using the NPX-glue system.

Functionalized graphene oxide for anti-VEGF siRNA delivery: preparation, characterization and evaluation in vitro and in vivo

GO–PLL–SDGR/VEGF-siRNA inhibits tumor growth as a tumor targeting delivery system.

RNAi Based Approaches to the Treatment of Malignant Glioma

RNA interference (RNAi) is a recently discovered, powerful molecular mechanism that can be harnessed to engineer gene-specific silencing in mammalian tissues. A mechanism, where short double-stranded RNA (dsRNA) molecules, when introduced into cells elicit specific “knock-down” of gene expression via degradation of targeted messenger RNA, has lately become the technique of choice for analysis of gene function in oncology research. Thus, RNAi is currently being extensively evaluated as a potential therapeutic strategy against malignant gliomas, since surgical, radiological, and chemotherapeutic interventions during the past few decades have done little to improve the poor prognosis rate for patients with these dreaded tumors. This review summarizes the pre-clinical studies that are currently underway to test the validity of RNAi as a potential therapeutic strategy against malignant gliomas, and discusses the potential technical Hurdles that remain to be overcome before the technique can become a promising clinical therapy to combat this frequently lethal disease.

Anticancer effects of chemokine receptor 4(CXCR4) gene silenced by CXCR4-siRNA in nude mice model of ovarian cancer

The aim is to study the anticancer effect of CXCR4 gene knockdown by CXCR4-siRNA in nude mice model of ovarian cancer. Injecti the SW626 tumor cells which had been transfected by vectors to make nude mouse model of ovarian cancer. The model mice were divided into interference group, negative control group, and blank control group. When the level of target genes were knocked down, the tumor volume was monitored and the tumor quality was measured; the expression of CXCR4 gene in the xenograft tumor was detected by RT-PCR, Western blot, and immunohistochemical staining. Nude mice model with implanted tumor were built successfully, after observing for 20 days. While the CXCR4 was knocked down, the abilities of invasion were weakened; the tumor volume and the tumor quality were also decreased. The CXCR4 mRNA and protein of the interference group decreased significantly (P < 0.05). The animal experiment was confirmed that silencing of CXCR4 gene by siRNA can obviously inhibit the tumorigenesis of ovarian cancer. Our work will provide the theoretical basis for genes interference therapy of ovarian cancer in future.

BBB-targeting, protein-based nanomedicines for drug and nucleic acid delivery to the CNS

The increasing incidence of diseases affecting the central nervous system (CNS) demands the urgent development of efficient drugs. While many of these medicines are already available, the Blood Brain Barrier and to a lesser extent, the Blood Spinal Cord Barrier pose physical and biological limitations to their diffusion to reach target tissues. Therefore, efforts are needed not only to address drug development but specially to design suitable vehicles for delivery into the CNS through systemic administration. In the context of the functional and structural versatility of proteins, recent advances in their biological fabrication and a better comprehension of the physiology of the CNS offer a plethora of opportunities for the construction and tailoring of plain nanoconjugates and of more complex nanosized vehicles able to cross these barriers. We revise here how the engineering of functional proteins offers drug delivery tools for specific CNS diseases and more transversally, how proteins can be engineered into smart nanoparticles or 'artificial viruses' to afford therapeutic requirements through alternative administration routes.

Delivery of RNAi therapeutics: work in progress

RNA interference (RNAi) therapeutics appear to offer substantial opportunities for future therapy. However, post-administration RNAi effectors are typically unable to reach disease target cells in vivo without the assistance of a delivery system or vector. The main focus of this review is on lipid-based nanoparticle (LNP) delivery systems in current research and development that have at least been shown to act as effective delivery systems for functional delivery of RNAi effectors to disease target cells in vivo. The potential utility of these LNP delivery systems is growing rapidly, and LNPs are emerging as the preferred synthetic delivery systems in preclinical studies and current nonviral RNAi effector clinical trials. Moreover, studies on LNP-mediated delivery in vivo are leading to the emergence of useful biophysical parameters and physical organic chemistry rules that provide a framework for understanding in vivo delivery behaviors and outcomes. These same parameters and rules should also suggest ways and means to develop next generations of LNPs with genuine utility and long-term clinical viability.

Silencing neurodegenerative disease: bringing RNA interference to the clinic

RNA interference (RNAi) is a recently described conserved biological pathway where non-coding RNAs suppress the expression of specific genes. Research efforts in the RNAi field aim to gain a better understanding of how its underlying machinery is orchestrated, to define the biological role of this conserved pathway, determine how to effectively manipulate RNAi in the laboratory and to integrate all this knowledge to develop novel therapies for human disease. This review summarizes the advances in the design of therapeutic RNAi for neurodegenerative diseases and discusses some of the experimental steps required to bring this therapy to human clinical trials.

Present and potential future issues in glioblastoma treatment

The treatment of glioblastomas requires a multidisciplinary approach that takes the presently incurable nature of the disease into consideration. Treatments are multimodal and include surgery, radiotherapy and chemotherapy. Current recommendations are that patients with glioblastomas should undergo maximum surgical resection, followed by concurrent radiation and chemotherapy with the novel alkylating drug temozolomide. This is then to be followed by additional adjuvant temozolomide for a period of up to 6 months. Major advances in surgical and imaging technologies used to treat glioblastoma patients are described. These technologies include magnetic resonance imaging and metabolic data that are helpful in the diagnosis and guiding of surgical resection. However, glioblastomas almost invariably recur near their initial sites. Disease progression usually occurs within 6 months and leads rapidly to death. A number of signaling pathways can be activated constitutively in migrating glioma cells, thus rendering these cells resistant to proapoptotic insults, such as conventional chemotherapies. Therefore, the molecular and cellular therapies and local drug delivery that could be used to complement conventional treatments are described, and some of the currently ongoing clinical trials are reviewed, with respect to these new approaches.

Epigenetics of Alzheimer's disease and frontotemporal dementia

This article will review the recent advances in the understanding of the role of epigenetic modifications and the promise of future epigenetic therapy in neurodegenerative dementias, including Alzheimer's disease and frontotemporal dementia.

Targeting intestinal inflammation with CD98 siRNA/PEI-loaded nanoparticles

Intestinal CD98 expression plays a crucial role in controlling homeostatic and innate immune responses in the gut. Modulation of CD98 expression in intestinal cells therefore represents a promising therapeutic strategy for the treatment and prevention of inflammatory intestinal diseases, such as inflammatory bowel disease. Here, the advantages of nanoparticles (NPs) are used, including their ability to easily pass through physiological barriers and evade phagocytosis, high loading concentration, rapid kinetics of mixing and resistance to degradation. Using physical chemistry characterizations techniques, CD98 siRNA/polyethyleneimine (PEI)-loaded NPs was characterized (diameter of ~480 nm and a zeta potential of -5.26 mV). Interestingly, CD98 siRNA can be electrostatically complexed by PEI and thus protected from RNase. In addition, CD98 siRNA/PEI-loaded NPs are nontoxic and biocompatible with intestinal cells. Oral administration of CD98/PEI-loaded NPs encapsulated in a hydrogel reduced CD98 expression in mouse colonic tissues and decreased dextran sodium sulfate-induced colitis in a mouse model. Finally, flow cytometry showed that CD98 was effectively downregulated in the intestinal epithelial cells and intestinal macrophages of treated mice. Finally, the results collectively demonstrated the therapeutic effect of "hierarchical nano-micro particles" with colon-homing capabilities and the ability to directly release "molecularly specific" CD98 siRNA in colonic cells, thereby decreasing colitis.

Neuroprotective effects of microRNA-210 on hypoxic-ischemic encephalopathy

Objectives. To reveal the effect of microRNA-210 on cell apoptosis caused by HIE. Methods. Postnatal day 7 rats after HI injury were intraventricularly injected with microRNA-210 mimic, microRNA-210 inhibitor, or physiological saline. 72 h after the injection, rats were sacrificed and the left hemispheres were collected. The expression level of microRNA-210 was identified by quantitative real-time PCR analysis. Apoptosis in brain sections was investigated by TUNEL assay. Apoptosis-related protein expressions were studied by Western blot analysis. Results. The results showed that microRNA-210, whose expression was downregulated in the brain 72 h after HI injury, suppressed neuronal apoptosis by inhibiting caspase activity and regulating the balance between bcl-2 and bax levels. Discussion. Recent study demonstrated that microRNA-210 has neuroprotective effects through inhibiting apoptosis in a murine model of HIE. It represents a potential novel therapeutic approach for the treatment of HIE.

microRNAs: innovative targets for cerebral ischemia and stroke

Stroke is one of the leading causes of death and disability worldwide. Because stroke is a multifactorial disease with a short therapeutic window many clinical stroke trials have failed and the only currently approved therapy is thrombolysis. MicroRNAs (miRNA) are endogenously expressed noncoding short single-stranded RNAs that play a role in the regulation of gene expression at the post-transcriptional level, via degradation or translational inhibition of their target mRNAs. The study of miRNAs is rapidly growing and recent studies have revealed a significant role of miRNAs in ischemic disease. miRNAs are especially important candidates for stroke therapeutics because of their ability to simultaneously regulate many target genes and since to date targeting single genes for therapeutic intervention has not yet succeeded in the clinic. Although there are already quite a few review articles about miRNA in ischemic heart disease, much less is currently known about miRNAs in cerebral ischemia. This review summarizes current knowledge about miRNAs and cerebral ischemia, focusing on the role of miRNAs in ischemia, both changes in expression and identification of potential targets, as well as the potential of miRNAs as biomarkers and therapeutic targets in cerebral ischemia.

Targeting potassium channels for increasing delivery of imaging agents and therapeutics to brain tumors

Every year in the US, 20,000 new primary and nearly 200,000 metastatic brain tumor cases are reported. The cerebral microvessels/capillaries that form the blood-brain barrier not only protect the brain from toxic agents in the blood but also pose a significant hindrance to the delivery of small and large therapeutic molecules. Different strategies have been employed to circumvent the physiological barrier posed by blood-brain tumor barrier (BTB). Studies in our laboratory have identified significant differences in the expression levels of certain genes and proteins between normal and brain tumor capillary endothelial cells (ECs). In this study, we validated the non-invasive and clinically relevant dynamic contrast enhancing-magnetic resonance imaging (DCE-MRI) method with invasive, clinically irrelevant but highly accurate quantitative autoradiography method using rat glioma model. We also showed that DCE-MRI metric of tissue vessel perfusion-permeability is sensitive to changes in blood vessel permeability following administration of calcium-activated potassium (BKCa) channel activator NS-1619. Our results show that human gliomas and brain tumor ECs that overexpress BKCa channels can be targeted for increased BTB permeability for MRI enhancing agents to brain tumors. We conclude that monitoring the outcome of increased MRI enhancing agents' delivery to microsatellites and leading tumor edges in glioma patients would lead to beneficial clinical outcome.

The MicroRNA

MicroRNAs (miRNAs), widely distributed, small regulatory RNA genes, target both messenger RNA (mRNA) degradation and suppression of protein translation based on sequence complementarity between the miRNA and its targeted mRNA. Different names have been used to describe various types of miRNA. During evolution, RNA retroviruses or transgenes invaded the eukaryotic genome and inserted itself in the noncoding regions of DNA, conceivably acting as transposon-like jumping genes, providing defense from viral invasion and fine-tuning of gene expression as a secondary level of gene modulation in eukaryotes. When a transposon is inserted in the intron, it becomes an intronic miRNA, taking advantage of the protein synthesis machinery, i.e., mRNA transcription and splicing, as a means for processing and maturation. Recently, miRNAs have been found to play an important, but not life-threatening, role in embryonic development. They might play a pivotal role in diverse biological systems in various organisms, facilitating a quick response and accurate plotting of body physiology and structures. Based on these unique properties, manufactured intronic miRNAs have been developed for in vitro evaluation of gene function, in vivo gene therapy, and generation of transgenic animal models. The biogenesis and identification of miRNAs, potential applications, and future directions for research are presented in this chapter, hopefully providing a guideline for further miRNA and gene function studies.

Structure and stability of the complex formed by oligonucleotides

Polycations and cationic lipids have been widely used as non-viral vectors for the delivery of plasmid DNA, siRNA and anti-sense oligonucleotides. To demonstrate that one polycation can form a complex with several types of DNA, we conducted a comparative study on the complexation of poly(L-lysine) (PLL) with 2000 bp salmon testes DNA (dsDNA), 21 bp double-stranded oligonucleotides (ds-oligo), and 21 nt single-stranded oligonucleotides (ss-oligo) in PBS buffer. The complexes are prepared by a titration method and the process is monitored by laser light scattering. It was found that in most cases, ss-oligo and ds-oligo form complexes with higher molecular weights than the complex formed by dsDNA at the same +/- ratio immediately after mixing. More importantly, the complexes formed by oligonucleotides are not stable, the scattered intensity gradually decreases to the level of the solvent in weeks. Atomic force microscopy measurements also indicate that the freshly prepared complex is subject to environmental changes and could dissociate very quickly. The behaviour of oligonucleotides cannot be predicted by the classical polyelectrolyte theories.

Gene silencing of IL-12 in dendritic cells inhibits autoimmune arthritis

Background

We have previously demonstrated that immune modulation can be accomplished by administration of gene silenced dendritic cells (DC) using siRNA. In this study, we demonstrate the therapeutic utilization of shRNA-modified DC as an antigen-specific tolerogenic vaccine strategy for autoimmune arthritis.

Methods

A shRNA that specifically targets IL-12 p35 was designed and cloned into a plasmid vectors (IL-12 shRNA). Bone marrow-derived DC from DBA/1 mice were transfected with the IL-12 shRNA construct in vitro. Mice with collagen II (CII)-induced arthritis (CIA) were treated with the modified DCs expressing the shRNA. Recall response and disease progression were assessed.

Results

After gene silencing of IL-12 in DC, DC were shown to selectively inhibit T cell proliferation on recall responses and in an MLR. In murine CIA, we demonstrated that administration of IL-12 shRNA-expressing DC that were pulsed with CII inhibited progression of arthritis. The therapeutic effects were evidenced by decreased clinical scores, inhibition of inflammatory cell infiltration in the joint, and suppression of T cell and B cell responses to CII.

Conclusion

We demonstrate a novel tolerance-inducing protocol for the treatment of autoimmune inflammatory joint disease in which the target antigen is known, utilizing DNA-directed RNA interference.

Polyphosphonium polymers for siRNA delivery: an efficient and nontoxic alternative to polyammonium carriers

A water-soluble polyphosphonium polymer was synthesized and directly compared with its ammonium analog in terms of siRNA delivery. The triethylphosphonium polymer shows transfection efficiency up to 65% with 100% cell viability, whereas the best result obtained for the ammonium analog reaches only 25% transfection with 85% cell viability. Moreover, the nature of the alkyl substituents on the phosphonium cations is shown to have an important influence on the transfection efficiency and toxicity of the polyplexes. The present results show that the use of positively charged phosphonium groups is a worthy choice to achieve a good balance between toxicity and transfection efficiency in gene delivery systems.

Cell surface receptors in malignant glioma

Despite advances in surgery, radiation, and chemotherapy, malignant gliomas are still highly lethal tumors. Traditional treatments that rely on nonspecific, cytotoxic approaches have a marginal impact on patient survival. However, recent advances in the molecular cancer biology underlying glioma pathogenesis have revealed that abnormalities in common cell surface receptors, including receptor tyrosine kinase and other cytokines, mediate the abnormal cellular signal pathways and aggressive biological behavior among the majority of these tumors. Some cell surface receptors have been targeted by novel agents in preclinical and clinical development. Such cancer-specific targeted agents might offer the promise of improved cancer control without substantial toxicity. Here, we review these common cell surface receptors with clinical significance for malignant glioma and discuss the molecular characteristics, pathological significance, and potential therapeutic application of these cell surface receptors. We also summarize the clinical trials of drugs targeting these cell surface receptors in malignant glioma patients.

Tiny non-coding RNAs in Parkinson's disease: implications, expectations and hypes

Parkinson's disease (PD) is the second most prevalent, progressive and aging related neurodegenerative disorder, characterized by the irreversible and selective degeneration of the nigrostriatal dopaminergic neurons. The early diagnosis, molecular explanation and permanent cure of this devastating and baffling disease have not yet been completely deciphered. Tiny non-coding RNAs, which consist of small or short interfering RNA (siRNA) and micro RNA (miRNA), intervene with and silence the expression of the specific genes through the evolutionary conserved process of RNA interference and act as post-transcriptional regulators. The differential expression patterns of miRNAs operate as key watchdogs and facilitate the identification of the potential therapeutic targets; however, miRNA modifiers aid in designing the strategies to encounter PD. Similarly, siRNA-mediated gene silencing paves the way to understand the function of the specific genes in PD pathogenesis by knocking down their expression. Applications of siRNAs and contributions of the potential miRNAs in investigating the etiology and molecular mechanisms of PD as well as in therapeutic interventions have been discussed in this article. The review also highlights the achievements, expectations and hypes associated with these tiny non-coding RNAs in PD.

Localized, targeted, and sustained siRNA delivery

Short interfering RNA (siRNA) functions directly in the cytoplasm, where it is assembled into an RNA-induced silencing complex (RISC). The localized delivery of siRNA to a specific site in vivo is highly challenging. There are many disease states in which a systemic effect of RNAi may be desirable; some examples include non-localized cancers, HIV, neurodegenerative diseases, respiratory viruses, and heart and vascular disease. In this Concept, we will focus on the localized delivery of siRNA to a target site using various delivery modalities. In certain tissues, such as the eye, central nervous system and lung, it has been demonstrated that a simple injection of naked siRNA will silence gene expression specifically in that tissue. To achieve local gene silencing in other tissues, a variety of approaches have been pursued to help stabilize the siRNA and facilitate uptake; they include chemical modification of the siRNA or complexation within liposomes or polymers to form nanoparticles. Recently, the use of macroscopic biomaterial scaffolds for siRNA delivery has been reported, and although there is still significant work to be done in this area to optimize the delivery systems, it is an important area of research that offers the potential for having great impact on the field of siRNA delivery.

Functional TNFα gene silencing mediated by polyethyleneimine/TNFα siRNA nanocomplexes in inflamed colon

During inflammatory bowel disease, TNFα is the major pro-inflammatory cytokine mainly secreted from macrophages and dendritic cells. Here, we have demonstrated that TNFα siRNA/polyethyleneimine loaded into polylactide at an optimal concentration of 20 g/L nanoparticles covered with polyvinyl alcohol are efficiently taken up by inflamed macrophages and inhibit TNFα secretion by the macrophages. Those nanoparticles have a diameter of ∼380 nm and zeta potential of -8 mV at pH 7.2, and are non-cytotoxic. Complexation, interactions and protection from RNAse between TNFα siRNA and polyethyleneimine were higher than those using chitosan. Importantly, complexation between TNFα siRNA and polyethyleneimine facilitated higher rates of siRNA loading into nanoparticles, compared to Chi or free siRNA mixed with Lipofectamine. Oral administration of encapsulated TNFα siRNA-loaded nanoparticles specifically reduced the TNFα expression/secretion in colonic tissue in LPS-treated mice. In conclusion, we have shown: (1) that proposed TNFα siRNA-loaded NPs are prepared via a non-denaturing synthetic process; (2) a high encapsulation rate of TNFα siRNA complexed to polyethyleneimine into NPs; (3) effective enzymatic protection of TNFα siRNA by polyethyleneimine; (4) non-cytotoxicity and biodegradability of nanoparticles loaded with polyethyleneimine/TNFα siRNA; and (5) in vitro and in vivo significant anti-inflammatory effects at low TNFα siRNA dose that is specific and restricted to the colonic cells. Our results collectively indicate that polyethyleneimine/TNFα siRNA nanocomplexes represent an efficient therapeutic option for diseases such as IBD.

Nanomedicine in GI

Recent advances in nanotechnology offer new hope for disease detection, prevention, and treatment. Nanomedicine is a rapidly evolving field wherein targeted therapeutic approaches using nanotechnology based on the pathophysiology of gastrointestinal diseases are being developed. Nanoparticle vectors capable of delivering drugs specifically and exclusively to regions of the gastrointestinal tract affected by disease for a prolonged period of time are likely to significantly reduce the side effects of existing otherwise effective treatments. This review aims at integrating various applications of the most recently developed nanomaterials that have tremendous potential for the detection and treatment of gastrointestinal diseases.

Silencing of ferrochelatase enhances 5-aminolevulinic acid-based fluorescence and photodynamic therapy efficacy

Background:

Recurrence of glioma frequently occurs within the marginal area of the surgical cavity due to invading residual cells. 5-Aminolevulinic acid (5-ALA) fluorescence-guided resection has been used as effective therapeutic modalities to improve discrimination of brain tumour margins and patient prognosis. However, the marginal areas of glioma usually show vague fluorescence, which makes tumour identification difficult, and the applicability of 5-ALA-based photodynamic therapy (PDT) is hampered by insufficient therapeutic efficacy in glioma tissues.

Methods:

To overcome these issues, we assessed the expression of ferrochelatase (FECH) gene, which encodes a key enzyme that catalyses the conversion of protoporphyrin IX (PpIX) to heme, in glioma surgical specimens and manipulated FECH in human glioma cell lines.

Results:

Prominent downregulation of FECH mRNA expression was found in glioblastoma tissues compared with normal brain tissues, suggesting that FECH is responsible for PpIX accumulation in glioblastoma cells. Depletion of FECH by small interference RNA enhanced PpIX fluorescence after exposure to 5-ALA concomitant with increased intracellular PpIX accumulation in glioma cells. Silencing of FECH caused marked growth inhibition and apoptosis induction by PDT in glioma cells.

Conclusion:

These results suggest that knockdown of FECH is a potential approach to enhance PpIX fluorescent quality for optimising the subjective discrimination of vague fluorescence and improving the effect of 5-ALA-PDT.

RNA interference therapy for glioblastoma

IMPORTANCE OF THE FIELD

Despite numerous advances made during the last decade in brain tumor therapy, the prognosis of glioblastoma has not improved and these tumors inevitably recur with no effective treatment. Thus, any new therapeutic strategy to target this most malignant tumor will be of significant benefit. RNAi is a powerful gene silencing method that might be used in combination with other agents to improve the efficacy of glioblastoma treatment.

AREAS COVERED IN THIS REVIEW

Recent progress and challenges of pre-clinical and clinical research of RNAi therapy for glioblastoma. The review covers literature from 2003 to 2009.

WHAT THE READER WILL GAIN

The principle of RNA interference therapy, three categories of RNAi triggers, different RNAi delivery system and pre-clinical and clinical studies that are currently underway to evaluate the validity of RNAi as a potential therapeutic strategy against glioblastoma are discussed.

TAKE HOME MESSAGE

RNA inference therapy combined with other therapeutics may offer therapeutic potential for glioblastoma multiforme. Further studies are required to develop more efficient and specific delivery systems, select suitable gene targets, optimize treatment dose and administration schedule, evaluate the efficacy of combination treatment strategies, establish a validated clinical response measure system etc.

Delivery of RNAi mediators

Delivering polynucleotides into animals has been a major challenge facing their success as therapeutic agents. Given the matured understanding of antibody‐mediated delivery techniques, it is possible to rationally design delivery vehicles that circulate in the blood stream and are specifically delivered into target organs. If the targeting moiety is designed to contain the cargo of an RNAi mediator without impacting its paratope, directed delivery can be achieved. In this article, we review the state of art in delivery technology for RNA mediators and address how this technique could soon be used to enhance the efficacy of the numerous small RNA therapeutic programs currently under evaluation. Copyright © 2010 John Wiley & Sons, Ltd.

This article is categorized under: 1

Regulatory RNAs/RNAi/Riboswitches > RNAi: Mechanisms of Action

2

RNA Methods > RNA Analyses in Cells

3

RNA in Disease and Development > RNA in Disease

Recent advances in the manipulation of murine gene expression and its utility for the study of human neurological disease

Transgenic mouse models have vastly contributed to our knowledge of the genetic and molecular pathways underlying the pathogenesis of neurological disorders that affect millions of people worldwide. Not only have they allowed the generation of disease models mimicking the human pathological state but they have also permitted the exploration of the pathological role of specific genes through the generation of knock-out and knock-in models. Classical constitutive transgenic mice have several limitations however, due to behavioral adaptation process occurring and conditional mouse models are time-consuming and often lack extensive spatial or temporal control of gene manipulation. These limitations could be overcome by means of innovative methods that are now available such as RNAi, viral vectors and large cloning DNA vectors. These tools have been extensively used for the generation of mouse models and are characterized by the superior control of transgene expression that has been proven invaluable in the assessment of novel treatments for neurological diseases and to further investigate the molecular processes underlying the etiopathology of neurological disorders. Furthermore, in association with classical transgenic mouse models, they have allowed the validation of innovative therapeutic strategies for the treatment of human neurological disorders. This review describes how these tools have overcome the limitations of classical transgenic mouse models and how they have been of value for the study of human neurological diseases.

Localized and sustained delivery of silencing RNA from macroscopic biopolymer hydrogels

The ability to silence the expression of specific genes at a particular location of the body would provide a powerful new therapeutic tool for treatment of diseases such as cancer or for use in regenerative medicine. RNA interference (RNAi) is a gene silencing mechanism where specific mRNA molecules that are complementary to short interfering RNA (siRNA) are degraded, thus inhibiting gene expression at the post-transcriptional level. However, the use of siRNA has not yet realized its full clinical potential due to degradation in vivo, the difficulty retaining siRNA at the site of interest, and the relatively short-term effect it has on rapidly dividing cells. In this work a new paradigm is presented that will allow for the localized delivery of siRNA that is controlled and sustained over time, thus allowing cells at the site of interest to be directly exposed to a gradual release of bioactive siRNA. To accomplish this, three different types of macroscopic, degradable biomaterial hydrogel scaffolds were employed: calcium crosslinked alginate, photocrosslinked alginate, and collagen. Differing rates of release from these hydrogels were achieved, and the ability of the released siRNA to knock down the expression of GFP in cells that constitutively express this protein was shown. Furthermore, the ability to encapsulate cells within these materials and achieve sustained gene silencing of these incorporated cells was demonstrated. These biopolymer hydrogels are injectable and, therefore, can be delivered in a minimally invasive manner, and they can serve as delivery vehicles for both siRNA and transplanted cell populations.

siRNA-mediated integrin-linked kinase suppression: nonspecific effects of siRNA/cationic liposome complexes trigger changes in the expression of phosphorylated-AKT and mTOR independently of ILK silencing

Short interfering RNA targeting ILK (ILK siRNA) could be used to treat patients with cancers where constitutive activation of the AKT/PI3K pathway is prominent (e.g., those cancers lack functional PTEN). It is generally believed that siRNA therapeutics will require the use of delivery systems and lipid-based formulations containing cationic lipids (CLs) are a viable option. However, CLs are known to be toxic and exposure to CLs can influence cell survival pathways. This study characterized how CLs combine with ILK siRNA to influence the AKT/PI3K pathway. Using PTEN-negative cell lines (PC3 castration-insensitive prostate cancer cells and U251 glioma cancer cells), the influence of CLs on the downstream consequences of ILK silencing was determined. When comparing nucleofection (an electroporation method that does not require the use of CLs) and CLs as means to deliver ILK siRNA, a 12- to 30-fold increase in siRNA delivery was achieved when using a CL formulation, yet ILK suppression was less efficient. Importantly, time-dependent signaling consequences associated with ILK silencing, including suppression of phosphorylated (serine 473)-AKT and changes in mTOR expression, were observed independently of ILK suppression when the target cells were exposed to cationic lipids following nucleofection-based delivery of ILK siRNA.

Delivery of small-interfering RNA (siRNA) to the brain

BACKGROUND

Two fundamental difficulties in the delivery of drugs to treat central nervous system (CNS) diseases are the systemic delivery of therapeutics across the bloodbrain-barrier (BBB), and the targeting of drugs to specific tissues or cells within the brain. With the advent and promise of RNA-based therapeutics that utilize RNA interference (RNAi) to trigger specific silencing of genes within diseased tissues, the necessity to surmount such obstacles has become even more urgent.

OBJECTIVE

Most pre-clinical and clinical studies on delivery of RNAi to the CNS have utilized invasive, intra-cerebral delivery of RNA to the targeted tissue. Thus, methods need to be developed to facilitate delivery of therapeutically significant quantities of RNA to the CNS via the systemic route, and to elicit clinically significant RNAi effects within the CNS tissues.

METHODS

Cell-penetrating-peptides (CPPs) are 'molecular delivery vehicles' that can traverse cell membranes and co-transport peptides or polynucleotides. The present invention examines 1) the utility of CPP-RNA duplexes for delivery of RNA to CNS tissues and, 2) cell-mediated release of the RNA payload once the CPP-RNA duplex is internalized by the CNS cells.

CONCLUSIONS

The invention and embodiments listed therein outline molecular tools that can be adapted for non-invasive, systemic delivery of therapeutic RNA to the CNS in a future clinical setting.

Treatment of diffuse intrinsic brainstem gliomas: failed approaches and future strategies

Diffuse intrinsic pontine gliomas constitute ~ 60-75% of tumors found within the pediatric brainstem. These malignant lesions present with rapidly progressive symptoms such as cranial nerve, long tract, or cerebellar dysfunctions. Magnetic resonance imaging is usually sufficient to establish the diagnosis and obviates the need for surgical biopsy in most cases. The prognosis of the disease is dismal, and the median survival is < 12 months. Resection is not a viable option. Standard therapy involves radiotherapy, which produces transient neurological improvement with a progression-free survival benefit, but provides no improvement in overall survival. Clinical trials have been conducted to assess the efficacy of chemotherapeutic and biological agents in the treatment of diffuse pontine gliomas. In this review, the authors discuss recent studies in which systemic therapy was administered prior to, concomitantly with, or after radiotherapy. For future perspective, the discussion includes a rationale for stereotactic biopsies as well as possible therapeutic options of local chemotherapy in these lesions.

Present and potential future adjuvant issues in high-grade astrocytic glioma treatment

Despite major advances in the management of malignant gliomas of which glioblastomas represent the ultimate grade of malignancy, they remain characterized by dismal prognoses. Glioblastoma patients have a median survival expectancy of only 14 months on the current standard treatment of surgical resection to the extent feasible, followed by adjuvant radiotherapy plus temozolomide, given concomitantly with and after radiotherapy. Malignant gliomas are associated with such dismal prognoses because glioma cells can actively migrate through the narrow extra-cellular spaces in the brain, often travelling relatively long distances, making them elusive targets for effective surgical management. Clinical and experimental data have demonstrated that invasive malignant glioma cells show a decrease in their proliferation rates and a relative resistance to apoptosis (type I programmed cell death) as compared to the highly cellular centre of the tumor, and this may contribute to their resistance to conventional pro-apoptotic chemotherapy and radiotherapy. Resistance to apoptosis results from changes at the genomic, transcriptional and post-transcriptional level of proteins, protein kinases and their transcriptional factor effectors. The PTEN/ PI3K/Akt/mTOR/NF-kappaB and the Ras/Raf/MEK/ERK signaling cascades play critical roles in the regulation of gene expression and prevention of apoptosis. Components of these pathways are mutated or aberrantly expressed in human cancer, notably glioblastomas. Monoclonal antibodies and low molecular-weight kinase inhibitors of these pathways are the most common classes of agents in targeted cancer treatment. However, most clinical trials of these agents as monotherapies have failed to demonstrate survival benefit. Despite resistance to apoptosis being closely linked to tumorigenesis, tumor cells can still be induced to die by non-apoptotic mechanisms such as necrosis, senescence, autophagy (type II programmed cell death) and mitotic catastrophe. Temozolomide brings significant therapeutic benefits in glioblastoma treatment. Part of temozolomide cytotoxic activity is exerted through pro-autophagic processes and also through the induction of late apoptosis. Autophagy, type II programmed cell death, represents an alternative mechanism to overcome, at least partly, the dramatic resistance of many cancers to pro-apoptotic-related therapies. Another way to potentially overcome apoptosis resistance is to decrease the migration of malignant glioma cells in the brain, which then should restore a level of sensitivity to pro-apoptotic drugs. Recent series of studies have supported the concept that malignant gliomas might be seen as an orchestration of cross-talks between cancer cells, microenvironment, vasculature and cancer stem cells. The present chapter focuses on (i) the major signaling pathways making glioblastomas resistant to apoptosis, (ii) the signaling pathways distinctly activated by pro-autophagic drugs as compared to pro-apoptotic ones, (iii) autophagic cell death as an alternative to combat malignant gliomas, (iv) the major scientific data already obtained by researchers to prove that temozolomide is actually a pro-autophagic and pro-apoptotic drug, (v) the molecular and cellular therapies and local drug delivery which could be used to complement conventional treatments, and a review of some of the currently ongoing clinical trials, (vi) the fact that reducing the levels of malignant glioma cell motility can restore pro-apoptotic drug sensitivity, (vii) the observation that inhibiting the sodium pump activity reduces both glioma cell proliferation and migration, (viii) the brain tumor stem cells as a target to complement conventional treatment.

Endocytosis at the blood–brain barrier: From basic understanding to drug delivery strategies

The blood-brain barrier (BBB) protects the central nervous system (CNS) from potentially harmful xenobiotics and endogenous molecules. Anatomically, it comprises the brain microvasculature whose functionality is nevertheless influenced by associated astrocyte, pericyte and neuronal cells. The highly restrictive paracellular pathway within brain microvasculature restricts significant CNS penetration to only those drugs whose physicochemical properties afford ready penetration into hydrophobic cell membranes or are capable of exploiting endogenous active transport processes such as solute carriers or endocytosis pathways. Endocytosis at the BBB is an essential pathway by which the brain obtains its nutrients and affords communication with the periphery. The development of strategies to exploit these endocytic pathways for the purposes of drug delivery to the CNS is still an immature field although some impressive results have been documented with the targeting of particular receptors. This current article initially provides an overview of general endocytosis processes and pathways showing evidence of their functional existence within the BBB. Subsequent sections provide, in an entity-specific manner, comprehensive reviews on BBB transport investigations of endocytosis involving: transferrin and the targeting of the transferrin receptor; hormones; cytokines; cell penetrating peptides; microorganisms and toxins, and nanoparticles aimed at more effectively delivering drugs to the CNS.

Delivery of hydrophobised 5-fluorouracil derivative to brain tissue through intravenous route using surface modified nanogels

Random copolymeric micelles composed of N-isopropylacrylamide (NIPAAM) and N-vinylpyrrolidone (VP) cross-linked with N,N'-methylenebisacrylamide (MBA) have been used as nanogel carriers to encapsulate N-hexylcarbamoyl-5-fluorouracil (HCFU), a prodrug of 5-FU, and have been targeted to brain tissue across blood-brain barrier (BBB) after coating with polysorbate 80. Accumulation of nanogel particles in the brain and other tissues of "strain A" mice had been monitored by radiolabeling of nanogels with (99m)Tc. Gamma Scintigraphic technique was also performed to see the distribution of (99m)Tc labeled nanogels in the brain. The retention time in blood appeared to be slightly longer for coated nanogels than that of uncoated nanogels though the accumulation of coated nanogels in the RES was more or less same as that of uncoated nanogels. The blood however had almost double accumulation of polysorbate 80 coated nanogels in the initial 5 min compared to that shown by uncoated nanogels. We speculate that coating of nanogels with polysorbate 80 alters the surface properties of nanogels, which results in relatively higher uptake in the brain tissue. The studies revealed that a large portion of (99m)Tc labeled HCFU loaded nanogels are accumulated in the RES (lung, liver and spleen). The accumulation of the labeled nanogels in the brain, however, is much less compared to RES and it has been found that while an amount of uncoated labeled nanogels was found to be 0.18% of the injected dose, it increased to 0.52% on coating with polysorbate 80. The optimal amount of polysorbate 80 added to nanogels for the maximum delivery of particles to brain was found to be 1% w/w. These results were further supported by the gamma scintigrams of New Zealand rabbits. Thus, the present nanogel system has opened a new avenue for poorly soluble drugs to be targeted to brain by coating the particles with polysorbate 80.

Animal models for target diseases in gene therapy--using DNA and siRNA delivery strategies

Nanoparticles, including lipopolyamines leading to lipoplexes, liposomes, and polyplexes are targeted drug carrier systems in the current search for a successful delivery system for polynucleic acids. This review is focused on the impact of gene and siRNA delivery for studies of efficacy, pharmacodynamics, and pharmacokinetics within the setting of the wide variety of in vivo animal models now used. This critical appraisal of the recent literature sets out the different models that are currently being investigated to bridge from studies in cell lines through towards clinical reality. Whilst many scientists will be familiar with rodent (murine, fecine, cricetine, and musteline) models, few probably think of fish as a clinically relevant animal model, but zebrafish, madake, and rainbow trout are all being used. Larger animal models include rabbit, cat, dog, and cow. Pig is used both for the prevention of foot-and-mouth disease and human diseases, sheep is a model for corneal transplantation, and the horse naturally develops arthritis. Non-human primate models (macaque, common marmoset, owl monkey) are used for preclinical gene vector safety and efficacy trials to bridge the gap prior to clinical studies. We aim for the safe development of clinically effective delivery systems for DNA and RNAi technologies.

Endothelial transcytosis in health and disease

The visionaries predicted the existence of transcytosis in endothelial cells; the cell biologists deciphered its mechanisms and (in part) the molecules involved in the process; the cell pathologists unravelled the presence of defective transcytosis in some diseases. The optimistic perspective is that transcytosis, in general, and receptor-mediated transcytosis, in particular, will be greatly exploited in order to target drugs and genes to exclusive sites in and on endothelial cells (EC) or underlying cells. The current recognition that plasmalemmal vesicles (caveolae) are the vehicles involved in EC transcytosis has moved through various phases from initial considerations of caveolae as unmovable sessile non-functional plasmalemma invaginations to the present identification of a multitude of molecules and a crowd of functions associated with these ubiquitous structures of endothelial and epithelial cells. Further understanding of the molecular machinery that precisely guides caveolae through the cells so as to reach the target membrane (fission, docking, and fusion), to avoid lysosomes, or on the contrary, to reach the lysosomes, and discharge the cargo molecules will assist in the design of pathways that, by manipulating the physiological route of caveolae, will carry molecules of choice (drugs, genes) at controlled concentrations to precise destinations.

Transferrin- and transferrin-receptor-antibody-modified nanoparticles enable drug delivery across the blood-brain barrier (BBB)

Human serum albumin (HSA) nanoparticles were manufactured by desolvation. Transferrin or transferrin receptor monoclonal antibodies (OX26 or R17217) were covalently coupled to the HSA nanoparticles using the NHS-PEG-MAL-5000 crosslinker. Loperamide was used as a model drug since it normally does not cross the blood-brain barrier (BBB) and was bound to the nanoparticles by adsorption. Loperamide-loaded HSA nanoparticles with covalently bound transferrin or the OX26 or R17217 antibodies induced significant anti-nociceptive effects in the tail-flick test in ICR (CD-1) mice after intravenous injection, demonstrating that transferrin or these antibodies covalently coupled to HSA nanoparticles are able to transport loperamide and possibly other drugs across the BBB. Control loperamide-loaded HSA nanoparticles with IgG2a antibodies yielded only marginal effects.

PDX-1 acts as a potential molecular target for treatment of human pancreatic cancer

OBJECTIVES

The purpose of this study was to investigate whether pancreatic and duodenal homeobox factor 1 (PDX-1) could serve as a potential molecular target for the treatment of pancreatic cancer.

METHODS

Cell proliferation, invasion capacity, and protein levels of cell cycle mediators were determined in human pancreatic cancer cells transfected with mouse PDX-1 (mPDX-1) alone or with mPDX-1 short hairpin RNA (shRNA) and/or human PDX-1 shRNA (huPDX-1 shRNA). Tumor cell growth and apoptosis were also evaluated in vivo in PANC-1 tumor-bearing severe combined immunodeficient mice receiving multiple treatments of intravenous liposomal huPDX-1 shRNA.

RESULTS

mPDX-1 overexpression resulted in the significant increase of cell proliferation and invasion in MIA PaCa2, but not PANC-1 cells. This effect was blocked by knocking down mPDX-1 expression with mPDX-1 shRNA. Silencing of huPDX-1 expression in PANC-1 cells inhibited cell proliferation in vitro and suppressed tumor growth in vivo which was associated with increased tumor cell apoptosis. PDX-1 overexpression resulted in dysregulation of the cell cycle with up-regulation of cyclin D, cyclin E, and Cdk2 and down-regulation of p27.

CONCLUSIONS

PDX-1 regulates cell proliferation and invasion in human pancreatic cancer cells. Down-regulation of PDX-1 expression inhibits pancreatic cancer cell growth in vitro and in vivo, implying its use as a potential therapeutic target for the treatment of pancreatic cancer.