A single recombinant adenovirus expressing p53 and p21-targeting artificial microRNAs efficiently induces apoptosis in human cancer cells

Construction and application of adenoviral vectors

Adenoviral vectors have been widely used as vaccine candidates or potential vaccine candidates against infectious diseases due to the convenience of genome manipulation, their ability to accommodate large exogenous gene fragments, easy access of obtaining high-titer of virus, and high efficiency of transduction. At the same time, adenoviral vectors have also been used extensively in clinical research for cancer gene therapy and treatment of diseases caused by a single gene defect. However, application of adenovirus also faces a series of challenges such as poor targeting, strong immune response against the vector itself, and they cannot be used repeatedly. It is believed that these problems will be solved gradually with further research and technological development in related fields. Here, we review the construction methods of adenoviral vectors, including "gutless" adenovirus and discuss application of adenoviral vectors as prophylactic vaccines for infectious pathogens and their application prospects as therapeutic vaccines for cancer and other kinds of chronic infectious disease such as human papillomavirus, hepatitis B virus, and hepatitis C virus.

MicroRNA-based therapy for glioblastoma: Opportunities and challenges

Glioblastoma (GBM) is the most common and aggressive primary malignant brain tumor and is characterized by high mortality and morbidity rates and unpredictable clinical behavior. The disappointing prognosis for patients with GBM even after surgery and postoperative radiation and chemotherapy has fueled the search for specific targets to provide new insights into the development of modern therapies. MicroRNAs (miRNAs/miRs) act as oncomirs and tumor suppressors to posttranscriptionally regulate the expression of various genes and silence many target genes involved in cell proliferation, the cell cycle, apoptosis, invasion, stem cell behavior, angiogenesis, the microenvironment and chemo- and radiotherapy resistance, which makes them attractive candidates as prognostic biomarkers and therapeutic targets or agents to advance GBM therapeutics. However, one of the major challenges of successful miRNA-based therapy is the need for an effective and safe system to deliver therapeutic compounds to specific tumor cells or tissues in vivo, particularly systems that can cross the blood-brain barrier (BBB). This challenge has shifted gradually as progress has been achieved in identifying novel tumor-related miRNAs and their targets, as well as the development of nanoparticles (NPs) as new carriers to deliver therapeutic compounds. Here, we provide an up-to-date summary (in recent 5 years) of the current knowledge of GBM-related oncomirs, tumor suppressors and microenvironmental miRNAs, with a focus on their potential applications as prognostic biomarkers and therapeutic targets, as well as recent advances in the development of carriers for nontoxic miRNA-based therapy delivery systems and how they can be adapted for therapy.

MicroRNA as a Potential Therapeutic Molecule in Cancer

Small noncoding RNAs, as post-translational regulators of many target genes, are not only markers of neoplastic disease initiation and progression, but also markers of response to anticancer therapy. Hundreds of miRNAs have been identified as biomarkers of drug resistance, and many have demonstrated the potential to sensitize cancer cells to therapy. Their properties of modulating the response of cells to therapy have made them a promising target for overcoming drug resistance. Several methods have been developed for the delivery of miRNAs to cancer cells, including introducing synthetic miRNA mimics, DNA plasmids containing miRNAs, and small molecules that epigenetically alter endogenous miRNA expression. The results of studies in animal models and preclinical studies for solid cancers and hematological malignancies have confirmed the effectiveness of treatment protocols using microRNA. Nevertheless, the use of miRNAs in anticancer therapy is not without limitations, including the development of a stable nanoconstruct, delivery method choices, and biodistribution. The aim of this review was to summarize the role of miRNAs in cancer treatment and to present new therapeutic concepts for these molecules. Supporting anticancer therapy with microRNA molecules has been verified in numerous clinical trials, which shows great potential in the treatment of cancer.

Artificial miRNAs as therapeutic tools: Challenges and opportunities

RNA interference (RNAi) technology has been used for almost two decades to study gene functions and in therapeutic approaches. It uses cellular machinery and small, designed RNAs in the form of synthetic small interfering RNAs (siRNAs) or vector-based short hairpin RNAs (shRNAs), and artificial miRNAs (amiRNAs) to inhibit a gene of interest. Artificial miRNAs, known also as miRNA mimics, shRNA-miRs, or pri-miRNA-like shRNAs have the most complex structures and undergo two-step processing in cells to form mature siRNAs, which are RNAi effectors. AmiRNAs are composed of a target-specific siRNA insert and scaffold based on a natural primary miRNA (pri-miRNA). siRNAs serve as a guide to search for complementary sequences in transcripts, whereas pri-miRNA scaffolds ensure proper processing and transport. The dynamics of siRNA maturation and siRNA levels in the cell resemble those of endogenous miRNAs; therefore amiRNAs are safer than other RNAi triggers. Delivered as viral vectors and expressed under tissue-specific polymerase II (Pol II) promoters, amiRNAs provide long-lasting silencing and expression in selected tissues. Therefore, amiRNAs are useful therapeutic tools for a broad spectrum of human diseases, including neurodegenerative diseases, cancers and viral infections. Recent reports on the role of sequence and structure in pri-miRNA processing may contribute to the improvement of the amiRNA tools. In addition, the success of a recently initiated clinical trial for Huntington's disease could pave the way for other amiRNA-based therapies, if proven effective and safe. This article is categorized under: RNA Processing > Processing of Small RNAs Regulatory RNAs/RNAi/Riboswitches > RNAi: Mechanisms of Action RNA in Disease and Development > RNA in Disease.

MicroRNAs in Ocular Infection

MicroRNAs (miRNAs) are small, non-coding, regulatory RNA molecules and constitute a newly recognized, important layer of gene-expression regulation at post-transcriptional levels. miRNAs quantitatively fine tune the expression of their downstream genes in a cell type- and developmental stage-specific fashion. miRNAs have been proven to play important roles in the normal development and function as well as in the pathogenesis of diseases in all tissues and organ systems. miRNAs have emerged as new therapeutic targets and biomarkers for treatment and diagnosis of various diseases. Although miRNA research in ocular infection remains in its early stages, a handful of pioneering studies have provided insight into the roles of miRNAs in the pathogenesis of parasitic, fungal, bacterial, and viral ocular infections. Here, we review the current status of research in miRNAs in several major ocular infectious diseases. We predict that the field of miRNAs in ocular infection will greatly expand with the discovery of novel miRNA-involved molecular mechanisms that will inform development of new therapies and identify novel diagnostic biomarkers.

p21 in Cancer Research

p21 functions as a cell cycle inhibitor and anti-proliferative effector in normal cells, and is dysregulated in some cancers. Earlier observations on p21 knockout models emphasized the role of this protein in cell cycle arrest under the p53 transcription factor activity. Although tumor-suppressor function of p21 is the most studied aspect of this protein in cancer, the role of p21 in phenotypic plasticity and its oncogenic/anti-apoptotic function, depending on p21 subcellular localization and p53 status, have been under scrutiny recently. Basic science and translational studies use precision gene editing to manipulate p21 itself, and proteins that interact with it; these studies have led to regulatory/functional/drug sensitivity discoveries as well as therapeutic approaches in cancer field. In this review, we will focus on targeting p21 in cancer research and its potential in providing novel therapies.

Unleashing the Full Potential of Oncolytic Adenoviruses against Cancer by Applying RNA Interference: The Force Awakens

Oncolytic virus therapy of cancer is an actively pursued field of research. Viruses that were once considered as pathogens threatening the wellbeing of humans and animals alike are with every passing decade more prominently regarded as vehicles for genetic and oncolytic therapies. Oncolytic viruses kill cancer cells, sparing healthy tissues, and provoke an anticancer immune response. Among these viruses, recombinant adenoviruses are particularly attractive agents for oncolytic immunotherapy of cancer. Different approaches are currently examined to maximize their therapeutic effect. Here, knowledge of virus–host interactions may lead the way. In this regard, viral and host microRNAs are of particular interest. In addition, cellular factors inhibiting viral replication or dampening immune responses are being discovered. Therefore, applying RNA interference is an attractive approach to strengthen the anticancer efficacy of oncolytic viruses gaining attention in recent years. RNA interference can be used to fortify the virus’ cancer cell-killing and immune-stimulating properties and to suppress cellular pathways to cripple the tumor. In this review, we discuss different ways of how RNA interference may be utilized to increase the efficacy of oncolytic adenoviruses, to reveal their full potential.

Up-regulation of p21WAF1/CIP1 by small activating RNA inhibits the in vitro and in vivo growth of pancreatic cancer cells

Aims and background

To study the inhibitory effect of p21WAF1/CIP1 activation by saRNA on the growth of human pancreatic cancer cells PANC-1 in vitro and in vivo.

Methods and study design

A dsRNA (dsP21) targeting the p21WAF1/CIP1 gene promoter at position-322 relative to the transcription start site was transfected into PANC-1 cells. Expression of mRNA and protein was evaluated by semiquantitative RT-PCR and Western blotting. Proliferation of PANC-1 cells was measured by the MTT method, and the apoptosis rate was detected by flow cytometry. PANC-1 cells were transplanted subcutaneously in nude mice, and the inhibitory effect of dsP21 on tumor growth was observed.

Results

The introduction of dsP21 was shown to efficiently up-regulate expression of the p21WAF1/CIP1 gene in PANC-1 cells according to the results of RT-PCR and Western blotting (P <0.01, compared with controls). The inhibitory effect on cell proliferation was confirmed by the MTT test (P <0.05, compared with controls). The apoptosis rate of PANC-1 cells treated with dsP21 was significantly higher than that of the control cells (P <0.01). Our experimental data showed that dsP21-mediated up-regulation of p21 expression exerted an apparent growth inhibitory effect on PANC-1 cells in vivo.

Conclusions

dsP21 targeting the p21WAF1/CIP1 gene promoter can specifically up-regulate expression of the p21WAF1/CIP1 gene in PANC-1 cells. It therefore has a substantially inhibitory effect on cell proliferation in vitro and in vivo and can be used as a new method and material for the gene therapy of pancreatic cancer.

Adenovirus-mediated artificial miRNA targetting fibrinogen-like protein 2 attenuates the severity of acute pancreatitis in mice

Severe acute pancreatitis (SAP) remains to be challenging for its unpredictable inflammatory progression from acute pancreatitis to SAP. Apoptosis is an important pathology of SAP. Fibrinogen-like protein 2 (FGL2) has been reported to be involved in apoptosis. The present study aimed to explore the therapeutic effect of an adenovirus-mediated artificial miRNA targetting FGL2 (Ad-FGL2-miRNA) in taurocholate-induced murine pancreatitis models. Sodium taurocholate was retrogradely injected into the biliopancreatic ducts of the C57/BL mice to induce SAP. FGL2 expression was measured with reverse transcription-PCR, Western blotting, and immunohistochemical staining. ELISA was used to detect the activity of amylase and the concentrations of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β). In addition, the mRNA levels of TNF-α and IL-1β were also detected. Finally, apoptosis was assessed by terminal deoxynucleotidyl transferase mediated dUTP-biotin nick-end labeling (TUNEL) method and Western blotting. Ad-FGL2-miRNA significantly suppressed FGL2 expression and alleviated pancreatic injury. Also, Ad-FGL2-miRNA markedly inhibited a post-SAP increase in the activation of TNF-α and IL-1β. Finally, pretreatment with Ad-FGL2-miRNA ameliorated apoptosis at the early stage of SAP by modulating cleaved caspase-3 and therefore played a protective role. These results indicated that FGL2 might be a promising target for attenuating the severity of SAP and adenovirus-mediated artificial miRNAs targetting FGL2 represented a potential therapeutic approach for the treatment of SAP.

Long non-coding RNA NEAT1 is a transcriptional target of p53 and modulates p53-induced transactivation and tumor-suppressor function

p53 is one of the most important tumor suppressor genes, and the direct transcriptional targets of p53 must be explored to elucidate its functional mechanisms. Thus far, the p53 targets that have been primarily studied are protein-coding genes. Our previous study revealed that several long non-coding RNAs (lncRNAs) are direct transcriptional targets of p53, and knockdown of specific lncRNAs modulates p53-induced apoptosis. In this study, analysis of next-generation chromatin immunoprecipitation-sequencing (ChIP-seq) data for p53 revealed that the lncRNA NEAT1 is a direct transcriptional target of p53. The suppression of NEAT1 induction by p53 attenuates the inhibitory effect of p53 on cancer cell growth and also modulates gene transactivation, including that of many lncRNAs. Furthermore, low expression of NEAT1 is related to poor prognosis in several cancers. These results indicate that the induction of NEAT1 expression contributes to the tumor-suppressor function of p53 and suggest that p53 and NEAT1 constitute a transcriptional network contributing to various biological functions and tumor suppression.

p53 mediates the suppression of cancer cell invasion by inducing LIMA1/EPLIN

The tumor suppressor gene p53 is frequently mutated in human cancer. p53 executes various functions, such as apoptosis induction and cell cycle arrest, by modulating transcriptional regulation. In this study, LIM domain and Actin-binding protein 1 (LIMA1) was identified as a target of the p53 family using a cDNA microarray. We also evaluated genome-wide occupancy of the p53 protein by performing chromatin immunoprecipitation-sequencing (ChIP-seq) and identified two p53 response elements in the LIMA1 gene. LIMA1 protein levels were increased by treatment with nutlin-3a, a small molecule that activates endogenous p53. In addition, LIMA1 expression was significantly downregulated in cancers compared with normal tissues. Knockdown of LIMA1 significantly enhanced cancer cell invasion and partially inhibited p53-induced suppression of cell invasion. Furthermore, low expression of LIMA1 in cancer patients correlated with decreased survival and poor prognosis. Thus, p53-induced LIMA1 inhibits cell invasion, and the downregulation of LIMA1 caused by p53 mutation results in decreased survival in cancer patients. Collectively, this study reveals the molecular mechanism of LIMA1 downregulation in various cancers and suggests that LIMA1 may be a novel prognostic predictor and a therapeutic target for cancer.

Triple-amiRNA VEGFRs inhibition in pancreatic cancer improves the efficacy of chemotherapy through EMT regulation

Pancreatic ductal adenocarcinoma (PDAC) is a devastating disease with dismal outcome. Both novel prognostic markers and therapeutic targets are needed to improve the overall outcome of patients. Although single or double VEGFRs have been studied in PDAC, little is known about the role of triple combination of VEGFRs (VEGFR1, 2, and 3) in prognosis and therapy. We determined VEGFRs protein expression in 241 pancreatic tissues by tissue microarray immunohistochemistry (TMA-IHC), and correlated with patients' clinical characteristics and overall survival. Subsequently, we inactivated VEGFRs expression using artificial microRNAs (amiRNAs) in vitro. Triple combination of amiRNAs to VEGFRs reduced cell proliferation, increased apoptosis, and reduced cell migration and invasion in pancreatic cancer cell lines. In the mouse xenograft pancreatic cancer model, triple VEGFRs silencing significantly reduced tumor growth, had synergistic effect with standard chemotherapy, and was associated with inhibition of epithelial mesenchymal transition (EMT). We conclude that triple combination of VEGFRs is a prognostic marker for PDAC, and inhibition of VEGFRs expression via amiRNA represents a novel targeted therapy in PDAC through regulating EMT.

An Artificially Designed Interfering lncRNA Expressed by Oncolytic Adenovirus Competitively Consumes OncomiRs to Exert Antitumor Efficacy in Hepatocellular Carcinoma

Endogenous miRNAs, especially oncogenic miRNAs (OncomiR), have been molecular targets for cancer therapy. We generated an artificially designed interfering long noncoding RNA (lncRNAi), which contains the sequences that can complementarily bind to multiple OncomiRs and is expressed by cancer-selectively replicating adenovirus. The adenovirus-expressed lncRNAi with high levels in hepatocellular carcinoma (HCC) cells competes with OncomiR target genes to bind to and consume OncomiRs, thereby achieving the targeted anti-HCC efficacy. With the targeting replication of adenovirus in HCC cells, lncRNAi was highly expressed and resulted in decreased abilities of proliferation, migration, and invasion, induced cell-cycle changes and apoptosis, and markedly changed the cellular mRNA and miRNA expression profiles in HCC cells. The optimal antitumor effect was also demonstrated on HCC cell line xenograft models and HCC patient-derived xenograft (PDX) tumor models in nude mice. This strategy has established a technology platform with a reliable therapeutic effect for HCC therapy. Mol Cancer Ther; 15(7); 1436-51. ©2016 AACR.

MAP3K1-targeting therapeutic artificial miRNA suppresses the growth and invasion of breast cancer in vivo and in vitro

Recent investigations have highlighted that therapeutic artificial microRNAs could be promising candidates for cancer therapy through the modulation of tumor promoter or suppressor. MEK kinase 1 (MEKK1) is expressed by mitogen-activated kinase kinase kinase 1 (MAP3K1), an important kinase that links Ras activation to MAPK signaling. In the present study, we showed that synthetic MAP3K1-targeting artificial miRNA may provide considerable beneficial effects in the prevention of breast cancer growth and metastasis. We showed that MEKK1 was highly expressed in human breast cancer specimens, compared with adjacent normal tissues. Using a miRNA-expressing lentivirus system, we delivered a artificial miRNA (Map3k1 amiRNA) that targets MAP3K1 into 4T1 breast cancer cells and investigated the impact of MAP3K1-targeting miRNA on the growth and invasive behavior of breast cancer in vitro and in vivo. We found that overexpression of Map3k1 amiRNA led to impaired activities of p-ERK and p-p38. In addition, Map3k1 amiRNA induced marked proliferative impairment and invasive attenuation in breast cancer cells. However, Map3k1 amiRNA did not have evident influence on the apoptotic response of 4T1 cells. Moreover, using in vivo nude mice model, we identified that Map3k1 amiRNA attenuated tumor growth and lung metastasis of breast cancer cells. Taken together, our findings explicitly indicated that MEKK1 exerted important oncogenic property in breast cancer development, and MAP3K1-targeting artificial miRNA may provide promising therapeutic effects in the treatment of breast cancer.

p53 Replacement Therapy for Cancer

Tumor suppressor gene (TSG) replacement therapy that involves various delivery systems is emerging as a promising antitumor strategy because malignant tumors develop through genetic alterations in TSGs. The most potent therapeutic TSG for tumor suppression is the multifunctional transcription factor p53 gene that regulates diverse cellular phenomena such as cell cycle arrest, senescence, apoptosis, and autophagy. Since the p53 gene is frequently inactivated by aberrant genetic regulation in human cancers, p53 replacement therapy is widely and frequently used as a potent antitumor strategy to restore wild-type p53 function in the p53-inactivated tumors. This chapter focuses on four types of p53 transfer systems: cationic liposome-DNA plasmid complexes, a replication-deficient adenovirus vector, a replication-competent adenovirus vector, and a protein transduction system. Moreover, we discuss recent advances in our understanding of the molecular basis of the p53-mediated cell death signaling pathway and therapeutic methods for enhancing tumor cell death and induction of bystander effects within tumor tissues in p53 replacement therapy. Exploration of the molecular mechanism underlying the p53-mediated tumor-suppressive network system and development of an effective strategy for enhancing p53-mediated cell death signaling pathways would lead to an improvement in the clinical outcome of patients with p53-inactivated cancers.

Scaffolds for Artificial miRNA Expression in Animal Cells

Artificial miRNAs (amiRNAs) are molecules that have been developed to promote gene silencing in a similar manner to naturally occurring miRNAs. amiRNAs are generally constructed by replacing the mature miRNA sequence in the pre-miRNA stem-loop with a sequence targeting a gene of interest. These molecules offer an interesting alternative to silencing approaches that are based on shRNAs and siRNAs because they present the same efficiency as these options and are less cytotoxic. amiRNAs have mostly been applied to gene knockdown in plants; they have been examined to a lesser extent in animal cells. Therefore, this article reviews the amiRNAs that have been developed for animal cells and focuses on the miRNA scaffolds that can already be applied to construct the artificial counterparts, as well as on the different approaches that have been described to promote amiRNA expression and silencing efficiency. Furthermore, the availability of amiRNA libraries and other tools that can be used to design and construct these molecules is briefly discussed, along with an overview of the therapeutic applications for which amiRNAs have already been evaluated.

Array-based genome-wide RNAi screening to identify shRNAs that enhance p53-related apoptosis in human cancer cells

p53 transduction is a potentially effective cancer therapy but does not result in a good therapeutic response in all human cancers due to resistance to apoptosis. To discover factors that overcome resistance to p53-induced apoptosis, we attempted to identify RNAi sequences that enhance p53-induced apoptosis. We screened a genome-wide lentiviral shRNA library in liver cancer Huh-7 and pancreatic cancer Panc-1 cells, both of which resist p53-induced apoptosis. After the infection of adenovirus expressing p53 or LacZ as a control, shRNA-treated populations were analyzed by microarray. We identified shRNAs that were significantly decreased in p53-infected cells compared with control cells. Among these shRNAs, shRNA-58335 was markedly decreased in both cancer cell lines tested. shRNA-58335 enhanced p53-related apoptosis in vitro and augmented the inhibitory effect of adenoviral p53 transduction on tumor growth in vivo. Furthermore, the enhanced apoptotic response by shRNA-58335 was also confirmed by treatment with PRIMA-1, which reactivates mutant p53, instead of adenoviral p53 transduction. We found that shRNA-58335 evokes the apoptotic response following p53 transduction or functional restoration of p53 with a small molecule drug in cancer cells resistant to p53-induced apoptosis. The combination of p53 restoration and RNAi-based drugs is expected to be a promising novel cancer therapy.

Clinical utility of recombinant adenoviral human p53 gene therapy: current perspectives

Gene therapy has promised to be a highly effective antitumor treatment by introducing a tumor suppressor gene or the abrogation of an oncogene. Among the potential therapeutic transgenes, the tumor suppressor gene p53 serves as an attractive target. Restoration of wild-type p53 function in tumors can be achieved by introduction of an intact complementary deoxyribonucleic acid copy of the p53 gene using a suitable viral vector, in most cases an adenoviral vector (Adp53). Preclinical in vitro and in vivo studies have shown that Adp53 triggers a dramatic tumor regression response in various cancers. These viruses are engineered to lack certain early proteins and are thus replication defective, including Gendicine, SCH-58500, and Advexin. Several types of tumor-specific p53-expressing conditionally replicating adenovirus vectors (known as replication-competent CRAdp53 vectors) have been developed, such as ONYX 015, AdDelta24-p53, SG600-p53, OBP-702, and H101. Various clinical trials have been conducted to investigate the safety and efficiency of these adenoviral vectors. In this review we will talk about the biological mechanisms, clinical utility, and therapeutic potentials of the replication-deficient Adp53-based and replication-competent CRAdp53-based gene therapy.

Advances in adenovirus-mediated p53 cancer gene therapy

INTRODUCTION

The tumor suppressor p53 gene regulates diverse cellular processes, such as cell-cycle arrest, senescence, apoptosis and autophagy, and it is frequently inactivated by genetic alterations in ∼ 50% of all types of human cancers. To restore wild-type p53 function in p53-inactivated tumors, adenovirus-mediated p53 gene therapy has been developed as a promising antitumor strategy in preclinical experiments and clinical studies.

AREAS COVERED

This review focuses on the clinical relevance of replication-deficient adenovirus vectors that carry the wild-type p53 gene (Ad-p53; Advexin, Gendicine and SCH-58500) in clinical studies of patients with various cancers and the future perspectives regarding conditionally replicating adenovirus vectors expressing the wild-type p53 gene (CRAd-p53; AdDelta24-p53, SG600-p53, OBP-702) in preclinical experiments. Moreover, the recent advances in our understanding of the molecular basis for the p53-mediated tumor suppression network induced by Ad-p53 and CRAd-p53 vectors and the combination therapies for promoting the therapeutic potential of adenovirus-mediated p53 gene therapy are discussed.

EXPERT OPINION

Exploration of the molecular mechanism underlying the p53-mediated tumor suppression network and the effective strategy for enhancing the p53-mediated cell death signaling pathway would provide novel insights into the improvement of clinical outcome in p53-based cancer gene therapy.

MicroRNA-146b improves intestinal injury in mouse colitis by activating nuclear factor-κB and improving epithelial barrier function

BACKGROUND

The precise role of microRNAs in inflammatory disease is not clear. The present study investigated the effect of microRNA (miR-146b) with respect to improving intestinal inflammation.

METHODS

The microRNA profile in interleukin-10 deficient mice was examined using microRNA arrays and miR-146b was selected for the subsequent experiments. The expression vectors containing either the whole sequence of miR-146b or small interfering RNA for miR-146b were intraperitoneally administered to the dextran sodium sulfate (DSS)-induced colitis mouse. The expression levels of inflammation-related mediators were examined by the reverse transcriptase-polymerase chain reaction and western blotting analysis. Intestinal barrier function was evaluated by an ex vivo mannitol flux study.

RESULTS

The overexpression of miR-146b activated the NF-κB pathway, improved epithelial barrier function, relieved intestinal inflammation in the DSS-induced colitis mice, and improved the survival rate of mice with lethal colitis. Furthermore, this amelioration of intestinal inflammation by miR-146b was negated by the inhibitor for the NF-κB pathway. The overexpression of miR-146b decreased the expression of siah2, which has a target sequence for miR-146b, and promoted the ubiquitination of TRAF proteins. This suggests that the up-regulation of NF-κB by miR-146b was mediated by inhibition of the ubiquitination of TRAF proteins upstream of NF-κB.

CONCLUSIONS

miR-146b improves intestinal inflammation by up-regulating NF-κB as a result of the decreased expression of siah2, which ubiquitinates TRAF proteins. Modulation of the miR-146b expression is a potentially useful therapy for the treatment of intestinal inflammation via activation of the NF-κB pathway.

Identification and analysis of large intergenic non-coding RNAs regulated by p53 family members through a genome-wide analysis of p53-binding sites

p53 is one of the most important known tumor suppressor genes, and it is inactivated in approximately half of human cancers. p53 family members execute various functions, such as apoptosis induction and cell cycle arrest, by modulating transcriptional regulation. Therefore, the direct transcriptional targets of the p53 family must be explored to elucidate the functional mechanisms of family members. To identify the direct transcriptional targets of p53 family members, we performed chromatin immunoprecipitation together with next-generation sequencing (ChIP-seq) and searched for p53-binding motifs across the entire human genome. Among the identified ChIP-seq peaks, approximately half were located in an intergenic region. Therefore, we assumed large intergenic non-coding RNAs (lincRNAs) to be major targets of the p53 family. Recent reports have revealed that lincRNAs play an important role in various biological and pathological processes, such as development, differentiation, stemness and carcinogenesis. Through a combination of ChIP-seq and in silico analyses, we found 23 lincRNAs that are upregulated by the p53 family. Additionally, knockdown of specific lincRNAs modulated p53-induced apoptosis and promoted the transcription of a gene cluster. Our results suggest that p53 family members, and lincRNAs constitute a complex transcriptional network involved in various biological functions and tumor suppression.

MicroRNA function and dysregulation in bone tumors: the evidence to date

Micro ribonucleic acids (miRNAs) are small non-coding RNA segments that have a role in the regulation of normal cellular development and proliferation including normal osteogenesis. They exert their effects through inhibition of specific target genes at the post-transcriptional level. Many miRNAs have altered expression levels in cancer (either increased or decreased depending on the specific miRNA). Altered miRNA expression profiles have been identified in several malignancies including primary bone tumors such as osteosarcoma and Ewing’s sarcoma. It is thought that they may function as tumor suppressor genes or oncogenes and hence when dysregulated contribute to the initiation and progression of malignancy. miRNAs are also thought to have a role in the development of bone metastases in other malignancies. In addition, evidence increasingly suggests that miRNAs may play a part in determining the response to chemotherapy in the treatment of osteosarcoma. These molecules are readily detectable in tissues, both fresh and formalin fixed paraffin embedded and, more recently, in blood. Although there are fewer published studies regarding circulating miRNA profiles, they appear to reflect changes in tissue expression. Thus miRNAs may serve as potential indicators of disease presence but more importantly, may have a role in disease characterization or as potential therapeutic targets. This review gives a brief overview of miRNA biochemistry and explores the evidence to date implicating these small molecules in the pathogenesis of bone tumors.

Dual programmed cell death pathways induced by p53 transactivation overcome resistance to oncolytic adenovirus in human osteosarcoma cells

Tumor suppressor p53 is a multifunctional transcription factor that regulates diverse cell fates, including apoptosis and autophagy in tumor biology. p53 overexpression enhances the antitumor activity of oncolytic adenoviruses; however, the molecular mechanism of this occurrence remains unclear. We previously developed a tumor-specific replication-competent oncolytic adenovirus, OBP-301, that kills human osteosarcoma cells, but some human osteosarcoma cells were OBP-301-resistant. In this study, we investigated the antitumor activity of a p53-expressing oncolytic adenovirus, OBP-702, and the molecular mechanism of the p53-mediated cell death pathway in OBP-301-resistant human osteosarcoma cells. The cytopathic activity of OBP-702 was examined in OBP-301-sensitive (U2OS and HOS) and OBP-301-resistant (SaOS-2 and MNNG/HOS) human osteosarcoma cells. The molecular mechanism in the OBP-702-mediated induction of two cell death pathways, apoptosis and autophagy, was investigated in OBP-301-resistant osteosarcoma cells. The antitumor effect of OBP-702 was further assessed using an orthotopic OBP-301-resistant MNNG/HOS osteosarcoma xenograft tumor model. OBP-702 suppressed the viability of OBP-301-sensitive and -resistant osteosarcoma cells more efficiently than OBP-301 or a replication-deficient p53-expressing adenovirus (Ad-p53). OBP-702 induced more profound apoptosis and autophagy when compared with OBP-301 or Ad-p53. E1A-mediated miR-93/106b upregulation induced p21 suppression, leading to p53-mediated apoptosis and autophagy in OBP-702-infected cells. p53 overexpression enhanced adenovirus-mediated autophagy through activation of damage-regulated autophagy modulator (DRAM). Moreover, OBP-702 suppressed tumor growth in an orthotopic OBP-301-resistant MNNG/HOS xenograft tumor model. These results suggest that OBP-702-mediated p53 transactivation is a promising antitumor strategy to induce dual apoptotic and autophagic cell death pathways via regulation of miRNA and DRAM in human osteosarcoma cells.

MicroRNAs in brain metastases: big things come in small packages

Metastatic brain tumors provide a formidable obstacle in the survival of affected cancer patients, an obstacle that current treatment is essentially ineffective against. Our understanding of the metastatic cascade has demonstrated the role of incorrectly regulated protein expression and proved it to be a crucial component of this process. Recently, molecular studies have emphasized the role of microRNAs, small non-coding RNAs that alter protein expression, in the regulation of both normal and abnormal biological processes, including cancer and its metastasis to the brain. Furthermore, studies have demonstrated the ability to distinguish normal from cancerous cells, primary from secondary brain tumors, and correctly categorize metastatic brain tumor tissue of origin based solely on microRNA profiles. Interestingly, manipulation of microRNAs has proven effective in cancer treatment. With the promise of reduced toxicity, increased efficacy, and individually directed therapy, using microRNA in the treatment of metastatic brain tumors may prove very useful. In this review, we focus on the multiple potential microRNA targets for the treatment of metastatic brain lesions as well as current and future directions for its use in gene therapy.

Adenoviral delivery of the EMX2 gene suppresses growth in human gastric cancer

BACKGROUND

EMX2 is a human orthologue of the Drosophila empty spiracles homeobox gene that has been implicated in embryogenesis. Recent studies suggest possible involvement of EMX2 in human cancers; however, the role of EMX2 in carcinogenesis needs further exploration.

RESULTS

In this study, we reported that down-regulation of EMX2 expression was significantly correlated with EMX2 promoter hypermethylation in gastric cancer. Restoring EMX2 expression using an adenovirus delivery system in gastric cancer cell lines lacking endogenous EMX2 expression led to inhibition of cell proliferation and Wnt signaling pathway both in vitro and in a gastric cancer xenograft model in vivo. In addition, we observed that animals treated with the adenoviral EMX2 expression vector had significantly better survival than those treated with empty adenoviral vector.

CONCLUSION

Our study suggests that EMX2 is a putative tumor suppressor in human gastric cancer. The adenoviral-EMX2 may have potential as a novel gene therapy for the treatment of patients with gastric cancer.

Revealing the anti-tumor effect of artificial miRNA p-27-5p on human breast carcinoma cell line T-47D

microRNAs (miRNAs) cause mRNA degradation or translation suppression of their target genes. Previous studies have found direct involvement of miRNAs in cancer initiation and progression. Artificial miRNAs, designed to target single or multiple genes of interest, provide a new therapeutic strategy for cancer. This study investigates the anti-tumor effect of a novel artificial miRNA, miR P-27-5p, on breast cancer. In this study, we reveal that miR P-27-5p downregulates the differential gene expressions associated with the protein modification process and regulation of cell cycle in T-47D cells. Introduction of this novel artificial miRNA, miR P-27-5p, into breast cell lines inhibits cell proliferation and induces the first “gap” phase (G1) cell cycle arrest in cancer cell lines but does not affect normal breast cells. We further show that miR P-27-5p targets the 3′-untranslated mRNA region (3′-UTR) of cyclin-dependent kinase 4 (CDK4) and reduces both the mRNA and protein level of CDK4, which in turn, interferes with phosphorylation of the retinoblastoma protein (RB1). Overall, our data suggest that the effects of miR p-27-5p on cell proliferation and G1 cell cycle arrest are through the downregulation of CDK4 and the suppression of RB1 phosphorylation. This study opens avenues for future therapies targeting breast cancer.

Protective role of estrogen-induced miRNA-29 expression in carbon tetrachloride-induced mouse liver injury

Previous studies have indicated that female animals are more resistant to carbon tetrachloride (CCl(4))-induced liver fibrosis than male animals, and that estradiol (E(2)) treatment can inhibit CCl(4)-induced animal hepatic fibrosis. The underlying mechanism governing these phenomena, however, has not been fully elucidated. Here we reported the role of estrogen-induced miRNA-29 (miR-29) expression in CCl(4)-induced mouse liver injury. Hepatic miR-29 levels were differentially regulated in female and male mice during CCl(4) treatment. Specifically, the levels of miR-29a and miR-29b expression were significantly decreased in the livers of male, but not female, mice following 4 weeks of CCl(4) treatment. The down-regulation of miR-29a and miR-29b in male mouse livers correlated with the early development of liver fibrosis, as indicated by increased expressions of fibrotic markers in male mice relative to female mice. In addition, E(2) was maintained at a higher level in female mice than in male mice. In contrast to TGF-β1 that decreased miR-29a/b expression in murine hepatoma IAR20 cells and normal hepatocytes, E(2) enhanced the expression of miR-29a/b through suppression of the nuclear factor-κB (NF-κB) signal pathway, which negatively regulates miR-29 expression. Furthermore, both E(2) treatment and intravenous injection of the recombinant adenovirus expressing miR-29a/b markedly increased the miR-29a/b level and attenuated the expression of fibrotic markers in mouse livers during CCl(4) treatment, supporting the protective role of E(2)-induced miR-29 in CCl(4)-induced hepatic injury. In conclusion, our results collectively demonstrate that estrogen can inhibit CCl(4)-induced hepatic injury through the induction of hepatic miR-29.

A novel apoptotic mechanism of genetically engineered adenovirus-mediated tumour-specific p53 overexpression through E1A-dependent p21 and MDM2 suppression

Oncolytic viruses engineered to replicate in tumour cells but not in normal cells could be used as tumour-specific vectors carrying the therapeutic genes. We previously developed a telomerase-specific oncolytic adenovirus, OBP-301, that causes cell death in human cancer cells with telomerase activities. Here, we further modified OBP-301 to express the wild-type p53 tumour suppressor gene (OBP-702), and investigated whether OBP-702 induces stronger antitumour activity than OBP-301. The antitumour effect of OBP-702 was compared to that of OBP-301 on OBP-301-sensitive (H358 and H460) and OBP-301-resistant (T.Tn and HSC4) human cancer cells. OBP-702 suppressed the viability of both OBP-301-sensitive and OBP-301-resistant cancer cells more efficiently than OBP-301. OBP-702 caused increased apoptosis compared to OBP-301 or a replication-deficient adenovirus expressing the p53 gene (Ad-p53) in H358 and T.Tn cells. Adenovirus E1A-mediated p21 and MDM2 downregulation was involved in the apoptosis caused by OBP-702. Moreover, OBP-702 significantly suppressed tumour growth in subcutaneous tumour xenograft models compared to monotherapy with OBP-301 or Ad-p53. Our data demonstrated that OBP-702 infection expressed adenovirus E1A and then inhibited p21 and MDM2 expression, which in turn efficiently induced apoptotic cell death. This novel apoptotic mechanism suggests that the p53-expressing OBP-702 is a promising antitumour reagent for human cancer and could improve the clinical outcome.

Salinomycin sensitizes antimitotic drugs-treated cancer cells by increasing apoptosis via the prevention of G2 arrest

Here, we investigated whether Sal could sensitize cancer cells to antimitotic drugs. We demonstrated that Sal sensitized paclitaxcel (PAC)-, docetaxcel (DOC)-, vinblastin (VIN)-, or colchicine (COL)-treated cancer cell lines, suggesting that Sal has the ability to sensitize the cells to any form of microtubule-targeting drugs. Sensitization to the antimitotic drugs could be achieved with very low concentrations of Sal, suggesting that there is a possibility to minimize Sal toxicity associated with human cancer patient treatments. Sensitization by Sal increased apoptosis, which was observed by C-PARP production. Sal sensitized the cancer cells to antimitotic drugs by preventing G2 arrest, suggesting that Sal contributes to the induction of mitotic catastrophe. Sal generally reduced cyclin D1 levels in PAC-, DOC-, and VIN-treated cells. In addition, Sal treatment increased pH2AX levels and reduced p21 levels in antimitotic drugs-treated cells. These observations suggest that the mechanisms underlying Sal sensitization to DNA-damaging compounds, radiation, and microtubule-targeting drugs are similar. Our data demonstrated that Sal sensitizes cancer cells to antimitotic drugs by increasing apoptosis through the prevention of G2 arrest via conserved Sal-sensitization mechanisms. These results may contribute to the development of Sal-based chemotherapy for cancer patients treated with antimitotic drugs.

Salinomycin sensitizes cancer cells to the effects of doxorubicin and etoposide treatment by increasing DNA damage and reducing p21 protein

BACKGROUND AND PURPOSE

Salinomycin (Sal) has recently been shown to inhibit various cancer stem cells. Here, we investigated whether Sal could sensitize cancer cells to the effects of doxorubicin (DOX) or etoposide (ETO).

EXPERIMENTAL APPROACH

Using the Comet assay, immunocytochemistry and Western blot analysis, we assessed the ability of Sal to increase DNA breakage. We performed a cell proliferation assay to determine cell viability, cellular detachment, increased pre-G1 region, Annexin V staining and TUNEL assay to measure the ability of Sal to increase apoptosis.

KEY RESULTS

Sal increased DNA breakage and phosphorylated levels of p53 and H2AX. Sal also induced the formation of DNA foci with pH2AX and 53BP1. Furthermore, Sal increased the sensitivity of cancer cells to the apoptotic effects of DOX or ETO. We found that pH2AX, pBRCA1, p53BP1 and pChk1 levels were greatly increased after co-treatment of Sal with DOX or ETO. The level of anti-apoptotic p21 protein was increased by DOX or ETO but decreased by Sal, which increased proteasome activity.

CONCLUSIONS AND IMPLICATIONS

This is the first study to report that Sal increases DNA damage, and this effect plays an important role in the increased apoptosis caused by Sal. Overall, we demonstrated that the ability of Sal to sensitize cancer cells to the effects of DOX or ETO is associated with an increase in DNA damage and a decrease in anti-apoptotic protein p21 levels. These results may contribute to the development of Sal-based chemotherapy for cancer patients receiving DOX or ETO treatment.

miRNA cassettes in viral vectors: problems and solutions

The discovery of RNA interference (RNAi), an evolutionary conserved gene silencing mechanism that is triggered by double stranded RNA, has led to tremendous efforts to use this technology for basic research and new RNA therapeutics. RNAi can be induced via transfection of synthetic small interfering RNAs (siRNAs), which results in a transient knockdown of the targeted mRNA. For stable gene silencing, short hairpin RNA (shRNA) or microRNA (miRNA) constructs have been developed. In mammals and humans, the natural RNAi pathway is triggered via endogenously expressed miRNAs. The use of modified miRNA expression cassettes to elucidate fundamental biological questions or to develop therapeutic strategies has received much attention. Viral vectors are particularly useful for the delivery of miRNA genes to specific target cells. To date, many viral vectors have been developed, each with distinct characteristics that make one vector more suitable for a certain purpose than others. This review covers the recent progress in miRNA-based gene-silencing approaches that use viral vectors, with a focus on their unique properties, respective limitations and possible solutions. Furthermore, we discuss a related topic that involves the insertion of miRNA-target sequences in viral vector systems to restrict their cellular range of gene expression. This article is part of a Special Issue entitled: MicroRNAs in viral gene regulation.

Salinomycin, a p-glycoprotein inhibitor, sensitizes radiation-treated cancer cells by increasing DNA damage and inducing G2 arrest

Salinomycin (Sal) is potentially useful for the treatment of cancer. The present study examined a novel mechanism of Sal sensitization in cancer cells. Sal sensitized radiation-treated cancer cells by inducing G2 arrest and causing DNA damage. Sal treatment also reduced p21 levels in radiation-treated cells. Considering that Sal sensitizes doxorubicin (DOX)- or etoposide (ETO)-treated cancer cells by causing DNA damage and reducing p21 expression, the results from our study suggest that the mechanism underlying Sal sensitization is conserved in both chemo- and radiation-treated cells. We also tested the ability of Sal to inhibit p-glycoprotein (P-gp), which plays a role in the efflux of anti-cancer drugs to reduce cellular damage. In particular, we compared Sal to verapamil (Ver), a well-known P-gp inhibitor. Sal inhibits P-gp with a different substrate distinct from that of Ver. In addition, Sal sensitized Ver-resistant cells, indicating that this compound is more effective for sensitizing than Ver. Taken together, the results from our study may contribute to the development of Sal-based therapy for cancer patients treated with P-gp-inhibiting drugs or radiation therapy.

Tumor suppressor miR-22 determines p53-dependent cellular fate through post-transcriptional regulation of p21

Selective activation of p53 target genes in response to various cellular stresses is a critical step in determining the ability to induce cell-cycle arrest or apoptosis. Here we report the identification of the microRNA miR-22 as a p53 target gene that selectively determines the induction of p53-dependent apoptosis by repressing p21. Combinatorial analyses of the AGO2 immunocomplex and gene expression profiles identified p21 as a direct target of miR-22. Induction of p21 was inhibited by miR-22 after exposure to the genotoxic agent Adriamycin (doxorubicin; Bedford Laboratories), sensitizing cells to p53-dependent apoptosis. Interestingly, the activation of miR-22 depended on the intensity of the stresses that induced cells to undergo apoptosis in the presence of p21 suppression. Our findings define an intrinsic molecular switch that determines p53-dependent cellular fate through post-transcriptional regulation of p21.

MicroRNA dysregulation in colorectal cancer: a clinical perspective

Recent researches have shed light on the biological importance of microRNAs (miRNAs) in colorectal cancer (CRC) genesis, progression and response to treatments. The potential utility of miRNAs in the preclinical stage have been explored and investigated. In this review, we explored the literature and reviewed the cutting edge progress in the discovery of noninvasive plasma and faecal miRNAs for CRC early diagnosis, as well as their measurability and predictability. We also discussed the utility of miRNAs as novel prognostic and predictive markers, and their association with CRC clinical phenotypes including recurrence, metastasis and therapeutic outcomes. Finally, we summarised miRNA-related single-nucleotide polymorphisms and their potential influence on sporadic CRC susceptibility and therapeutic response. In conclusion, the use of miRNAs as biomarker for CRC is still in its infancy and need further characterisation and evaluation.

MicroRNA dysregulation in colorectal cancer: a clinical perspective

Recent researches have shed light on the biological importance of microRNAs (miRNAs) in colorectal cancer (CRC) genesis, progression and response to treatments. The potential utility of miRNAs in the preclinical stage have been explored and investigated. In this review, we explored the literature and reviewed the cutting edge progress in the discovery of noninvasive plasma and faecal miRNAs for CRC early diagnosis, as well as their measurability and predictability. We also discussed the utility of miRNAs as novel prognostic and predictive markers, and their association with CRC clinical phenotypes including recurrence, metastasis and therapeutic outcomes. Finally, we summarised miRNA-related single-nucleotide polymorphisms and their potential influence on sporadic CRC susceptibility and therapeutic response. In conclusion, the use of miRNAs as biomarker for CRC is still in its infancy and need further characterisation and evaluation.

Prognostic biomarkers in squamous cell carcinoma of the anus: a systematic review

BACKGROUND

recent decades have seen combination chemoradiotherapy become the standard treatment for anal squamous cell carcinoma (SCC). However, the burden of this disease continues to rise, with only 10% of patients with metastatic disease surviving >2 years. Further insight into tumour characteristics and molecular biology may identify novel therapeutic targets. This systematic review examines current prognostic markers in SCC of the anus.

METHODS

an extensive literature search was performed to identify studies reporting on biomarkers in anal cancer in the context of clinical outcome following treatment primarily with chemoradiotherapy.

RESULTS

in all, 21 studies were included. A total of 29 biomarkers were studied belonging to 9 different functional classes. Of these biomarkers, 13 were found to have an association with outcome in at least one study. The tumour-suppressor genes p53 and p21 were the only markers shown to be of prognostic value in more than one study.

CONCLUSIONS

an array of biomarkers have been identified that correlate with survival following chemoradiotherapy in anal cancer. However, investigators are yet to identify a biomarker that has the ability to consistently predict outcome in this disease. Further studies are needed to elucidate whether these candidate biomarkers demonstrate their optimum value when they serve as targets for new therapeutic strategies.

Review article: gene therapy, recent developments and future prospects in gastrointestinal oncology

BACKGROUND

Gene therapy consists of the introduction of genetic material into cells for a therapeutic purpose. A wide range of gene therapy vectors have been developed and used for applications in gastrointestinal oncology.

AIM

To review recent developments and published clinical trials concerning the application of gene therapy in the treatment of liver, colon and pancreatic cancers.

METHODS

Search of the literature published in English using the PubMed database.

RESULTS

A large variety of therapeutic genes are under investigation, such as tumour suppressor, suicide, antiangiogenesis, inflammatory cytokine and micro-RNA genes. Recent progress concerns new vectors, such as oncolytic viruses, and the synergy between viral gene therapy, chemotherapy and radiation therapy. As evidence of these basic developments, recently published phase I and II clinical trials, using both single agents and combination strategies, in adjuvant or advanced disease settings, have shown encouraging results and good safety records.

CONCLUSIONS

Cancer gene therapy is not yet indicated in clinical practice. However, basic and clinical advances have been reported and gene therapy is a promising, new therapeutic approach for the treatment of gastrointestinal tumours.