RNA interference: ready to silence cancer?

An overview of Skp2: a promising new therapeutic target of psoriasis

INTRODUCTION

Psoriasis is a chronic immune-mediated disorder affecting over 2-3% of the population worldwide, significantly impacting quality of life. Despite the availability of various therapeutic interventions, concerns persist regarding lesion recurrence and potential alterations in immune surveillance promoting cancer progression. Recent advancements in understanding cellular and molecular pathways have unveiled key factors in psoriasis etiology, including IL-17, 22, 23, TNF-α, PDE-4, JAK-STAT inhibitors, and AhR agonists. This work explores the potential of S-phase kinase-associated protein 2 (Skp2) as a therapeutic target in psoriasis.

AREA COVERED

This review covers the current understanding of psoriasis pathophysiology, including immune dysregulation, and the role of keratinocytes and ubiquitin. It also delves into Skp2 role in cell cycle regulation, and its correlation with angiogenesis and ubiquitin in psoriasis. The evolving therapeutic approaches targeting Skp2, including small molecule inhibitors, are also discussed.

EXPERT OPINION

Targeting Skp2 holds promise for developing novel therapeutic approaches for psoriasis. By modulating Skp2 activity or expression, it may be possible to intervene in inflammatory and proliferative processes underlying the disease. Further research into Skp2 inhibitors and their efficacy in preclinical and clinical settings is warranted to harness the full potential of Skp2 as a therapeutic target in psoriasis management.

miR-133a acts as a tumor suppressor in colorectal cancer by targeting eIF4A1

Emerging evidence indicates that microRNAs play critical roles in carcinogenesis and cancer progression. In this study, miR-133a was found to be significantly downregulated in colon tumor tissues. We aimed to determine its biological function, molecular mechanisms, and direct target genes in colorectal cancer. From these results, we found that miR-133a was significantly downregulated in primary tumor tissues and colon cancer cell lines. Ectopic expression of miR-133a in colon cancer cell lines significantly suppressed cell growth, as evidenced by cell viability and colony formation assays, as well as reduced xenograft tumor growth in nude mice. However, the effect of miR-133a was abolished by the overexpression of eIF4A1. Moreover, miR-133a inhibited cellular migration and invasiveness. A luciferase activity assay revealed oncogene eukaryotic translation initiation factor 4A1 as a direct target gene of miR-133a, whose expression was inversely correlated with that of miR-133a. Our results demonstrate that miR-133a plays a pivotal role in colorectal cancer by inhibiting cell proliferation, invasion, and migration by targeting oncogenic eukaryotic translation initiation factor 4A1, which acts as a tumor suppressor and may provide a new potential therapeutic target in colorectal cancer.

Down-regulation of sidB gene by use of RNA interference in Aspergillus nidulans

BACKGROUND

Introduction of the RNA interference (RNAi) machinery has guided the researchers to discover the function of essential vital or virulence factor genes in the microorganisms such as fungi. In the filamentous fungus Aspergillus nidulans, the gene sidB plays an essential role in septation, conidiation and vegetative hyphal growth. In the present study, we benefited from the RNAi strategy for down-regulating a vital gene, sidB, in the fungus A. nidulans.

METHODS

The 21-nucleotide small interfering RNA (siRNA) was designed based on the cDNA sequence of the sidB gene in A. nidulans. Transfection was performed through taking up siRNA from medium by 6 hour-germinated spores. To evaluate the morphologic effects of siRNA on the fungus, germ tube elongation was followed. Moreover, total RNA was extracted and quantitative changes in expression of the sidB gene were analyzed by measuring the cognate sidB mRNA level by use of a quantitative real-time RT-PCR assay.

RESULTS

Compared to untreated-siRNA samples, a significant inhibition in germ tube elongation was observed in the presence of 25 nM of siRNA (42 VS 21 µM). In addition, at the concentration of 25 nM, a considerable decrease in sidB gene expression was revealed.

CONCLUSION

Usage of RNAi as a kind of post-transcriptional gene silencing methods is a promising approach for designing new antifungal agents and discovering new drug delivery systems.

Lentivirus-mediated knockdown of CUGBP1 suppresses gastric cancer cell proliferation in vitro

Gastric cancer is the second most common cause of cancer-related death worldwide. This study was designed to examine the role of CUGBP1 in cell growth via an RNA interference (RNAi) lentivirus system in gastric cancer cells in vitro. The expression of CUGBP1 was much stronger in gastric cancer tissues than that in adjacent normal tissues. The lentivirus-mediated knockdown of CUGBP1 resulted in a significant reduction of CUGBP1 expression in MGC-803 gastric cancer cells. The cell viability was remarkably decreased by 50 % after 5 days of infection, as determined by MTT assay. Moreover, the size and the number of colonies formed in MGC-803 cells were markedly reduced in the absence of CUGBP1. Furthermore, the silencing of CUGBP1 downregulated the expression levels of cyclin B1 and cyclin D1, which are involved in cell cycle control. These results clearly indicated that CUGBP1 is essential for the growth of gastric cancer cells. Therefore, silencing of CUGBP1 by RNAi could be developed as a promising therapeutic approach for gastric cancer.

Specific knockdown of PPARδ gene in colon cancer cells by lentivirus-mediated RNA interfering

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors. Of this family, PPARδ has been implicated in the pathogenesis of colorectal cancer, whereas its exact role is highly controversial as available studies yield conflicting results. Therefore, further studies using powerful and duplicable methods are needed to clarify the functions of PPARδ in colorectal cancer. RNA interference (RNAi) is such a powerful tool for specific suppression of gene expression at the posttranscriptional level. Of available RNAi methods, lentivirus has been shown to mediate RNAi most efficiently and stably based on its remarkable advantages, such as powerful transduction efficiency and a wider range of target cells, integration of expression cassette into host genomics, low immunogenicity and self-inactivated and replication-incompetent after integrating into host genomics. In this chapter, we will introduce the details of using lentivirus-mediated RNAi to specifically knockdown the expression of PPARδ in colon cancer cell lines. This method includes: designing and cloning short-hairpin RNA cassette into lentivector, constructing and titrating lentiviral particles, infecting target cells with lentivirus and assaying the knockdown efficiency.

RNA interference--a silent but an efficient therapeutic tool

RNA interference (RNAi) is an evolutionary conserved gene regulation pathway that has emerged as an important discovery in the field of molecular biology. One of the important advantages of RNAi in therapy is that it brings about efficient downregulation of gene expression by targeting complementary transcripts in comparison with other antisense-based techniques. RNAi can be can be achieved by introducing chemically synthesized small interfering RNAs (siRNAs) into a cell system. A more stable knockdown effect can be brought about by the use of plasmid or viral vectors encoding the siRNA. RNAi has been used in reverse genetics to understand the function of specific genes and also as a therapeutic tool in treating human diseases. This review provides a brief insight into the therapeutic applications of RNAi against debilitating diseases.

VDAC, a multi-functional mitochondrial protein regulating cell life and death

Research over the past decade has extended the prevailing view of the mitochondrion to include functions well beyond the generation of cellular energy. It is now recognized that mitochondria play a crucial role in cell signaling events, inter-organellar communication, aging, cell proliferation, diseases and cell death. Thus, mitochondria play a central role in the regulation of apoptosis (programmed cell death) and serve as the venue for cellular decisions leading to cell life or death. One of the mitochondrial proteins controlling cell life and death is the voltage-dependent anion channel (VDAC), also known as mitochondrial porin. VDAC, located in the mitochondrial outer membrane, functions as gatekeeper for the entry and exit of mitochondrial metabolites, thereby controlling cross-talk between mitochondria and the rest of the cell. VDAC is also a key player in mitochondria-mediated apoptosis. Thus, in addition to regulating the metabolic and energetic functions of mitochondria, VDAC appears to be a convergence point for a variety of cell survival and cell death signals mediated by its association with various ligands and proteins. In this article, we review what is known about the VDAC channel in terms of its structure, relevance to ATP rationing, Ca(2+) homeostasis, protection against oxidative stress, regulation of apoptosis, involvement in several diseases and its role in the action of different drugs. In light of our recent findings and the recently solved NMR- and crystallography-based 3D structures of VDAC1, the focus of this review will be on the central role of VDAC in cell life and death, addressing VDAC function in the regulation of mitochondria-mediated apoptosis with an emphasis on structure-function relations. Understanding structure-function relationships of VDAC is critical for deciphering how this channel can perform such a variety of functions, all important for cell life and death. This review also provides insight into the potential of VDAC1 as a rational target for new therapeutics.

Future approaches in periodontal regeneration: gene therapy, stem cells, and RNA interference

Periodontal disease is a major public health issue and the development of effective therapies to treat the disease and regenerate periodontal tissue is an important goal of today's medicine. This article highlights recent scientific advancements in gene therapy, stem cell biology, and RNA interference with the intent of identifying their potential in periodontal tissue regeneration. Results from basic research, preclinical, and clinical studies indicate that these fields of research may soon contribute to more effective regenerative therapies for periodontal disease.

Inhibitors of indoleamine-2,3-dioxygenase for cancer therapy: can we see the wood for the trees?

Indoleamine-2,3-dioxygenase (IDO) is an immunosuppressive enzyme capable of inhibiting a destructive maternal T cell response against allogeneic fetuses. Expression of IDO is evident in tumours and is thought to enable escape from immunologically mediated rejection. Consequently, clinical trials using an inhibitor of IDO, 1-methyltryptophan (1MT), have been initiated. However, a review of the current literature indicates that we are far from understanding the biological relevance of IDO expression during tumorigenesis. A better understanding of IDO biology is needed to comprehend the effect of IDO inhibitors and to provide a rationale for their therapeutic application in cancer.

A step-by-step procedure to analyze the efficacy of siRNA using real-time PCR

Knockdown of cellular RNA using short interfering RNA has enabled researchers to perform loss-of-function (LOF) experiments in a wide variety of cell types and model systems. RNA interference techniques and reagents have made possible experiments that test everything from the analysis of function of single genes to screening for genes that are involved in critical biological pathways on a genome-wide scale. Although siRNA experiments are generally common practice in research laboratories, it is still important to keep in mind that many factors can influence efficacy of knockdown. A properly designed siRNA, optimized protocols of siRNA delivery, and an appropriate and well-optimized readout are all critical parameters for ensuring the success of your experiment. In this chapter, we provide step-by-step procedures for performing an siRNA knockdown experiment from cell culture to analysis of knockdown using quantitative real-time PCR.

RNA interference against peroxisome proliferator-activated receptor delta gene promotes proliferation of human colorectal cancer cells

PURPOSE

This study was designed to investigate the effects of peroxisome proliferator-activated receptor delta (PPAR delta) on the proliferation and apoptosis of human colorectal cancer cells.

METHODS

For RNA interfering (RNAi), HCT-116 cells were transfected with short hairpin RNA (shRNA)-expressing plasmids against PPAR delta or negative control vectors, and the stably transfected cells were selected with G418. The efficacy of RNAi was assessed by real-time reverse transcription polymerase chain reaction (RT-PCR) and Western blotting analysis. The proliferation, cell cycle, and apoptosis of HCT-116 cells treated by RNAi, compared with those containing control vectors or untreated, were analyzed respectively by using MTT (methyl thiazolyl tetrazolium), flow cytometry, and TdT (terminal deoxynucleotidyl transferase)-mediated dUTP nick end-labeling (TUNEL) assay.

RESULTS

RNAi targeting PPAR delta resulted in substantial suppression of PPAR delta expression and significantly promoted the proliferation of HCT-116 cells relative to those with control vectors or untreated, obviously decreasing the frequency of G1-phase cells but had no effect on cell apoptosis.

CONCLUSIONS

PPAR delta may inhibit the proliferation of CRC cells and increase the number of cells in G1 phase, without any function in cell apoptosis.

MicroRNA in Cutaneous Wound Healing: A New Paradigm

Repair of a defect in the human skin is a highly orchestrated physiological process involving numerous factors that act in a temporally resolved synergistic manner to re-establish barrier function by regenerating new skin. The inducible expression and repression of genes represents a key component of this regenerative process. MicroRNAs (miRNAs) are approximately 22-nucleotide-long endogenously expressed non-coding RNAs that regulate the expression of gene products by inhibition of translation and/or transcription in animals. miRNAs play a key role in skin morphogenesis and in regulating angiogenesis. The vascular endothelial growth factor signaling path seems to be under repressor control by miRNAs. Mature miRNA-dependent mechanisms impair angiogenesis in vivo. It is critically important to recognize that the understanding of cutaneous wound healing is incomplete without appreciating the functional significance of wound-induced miRNA. Ongoing work in our laboratory has led to the observation that the cutaneous wound healing process involves changes in the expression of specific miRNA at specific phases of wound healing. We hypothesize that dysregulation of specific miRNA is critical in derailing the healing sequence in chronic problem wounds. If tested positive, this hypothesis is likely to lead to completely novel diagnostic and therapeutic strategies for the treatment of problem wounds.

RNAi applications in target validation

The emergence of systems biology is certain to transform the identification and validation of therapeutic targets in modern drug discovery. A relatively recent systems biology approach is functional genomics, which identifies the molecular mechanisms responsible for a specific phenotype by interrogating the activity of all of an organism's genes. Initially undertaken in model organisms such as Caenorhabditis elegans, Saccharomyces cerevisiae, and Drosophila melanogaster, functional genomics has now moved into the realm of mammalian cells both in vitro and in vivo due to the development of RNA interference. RNA interference is a conserved biological process that has evolved to specifically and efficiently silence genes. Genome-wide screens using RNA interference have proven powerful in elucidating components of functionally related pathways and have therefore become integral for the development of new and improved therapeutic targets. This article provides an overview of many of the systems biology approaches taken, using RNA interference, in order to demonstrate how it may be used today for drug discovery and tomorrow as a targeted therapy.

MYCN deregulation as a potential target for novel therapies in rhabdomyosarcoma

Rhabdomyosarcoma is the most common soft-tissue sarcoma of childhood. Treatment requires a multimodality approach combining chemotherapy with surgery and radiotherapy. Although overall outcomes have improved considerably, the outlook for patients with high-risk disease, particularly the alveolar subtype, remains bleak and there is a clear need for new chemotherapeutic strategies. This review focuses on the possibilities for interventions targeting myc myelocytomatosis viral related oncogene, neuroblastoma derived (MYCN). The importance of aberrant expression of this oncogene is well established in neuroblastoma and recent data indicate that MYCN deregulation also occurs in up to a quarter of alveolar subtype cases. A range of possible approaches to target MYCN is discussed, including nucleic acid-based and immunotherapy strategies.