Gene Summary

Gene:DKK3; dickkopf WNT signaling pathway inhibitor 3
Aliases: RIG, REIC
Summary:This gene encodes a protein that is a member of the dickkopf family. The secreted protein contains two cysteine rich regions and is involved in embryonic development through its interactions with the Wnt signaling pathway. The expression of this gene is decreased in a variety of cancer cell lines and it may function as a tumor suppressor gene. Alternative splicing results in multiple transcript variants encoding the same protein. [provided by RefSeq, Jul 2008]
Databases:OMIM, VEGA, HGNC, Ensembl, GeneCard, Gene
Protein:dickkopf-related protein 3
Source:NCBIAccessed: 27 February, 2015


What does this gene/protein do?
Show (11)

Cancer Overview

Research Indicators

Publications Per Year (1990-2015)
Graph generated 27 February 2015 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • Cancer Gene Expression Regulation
  • Apoptosis
  • Translocation
  • Gene Silencing
  • Tissue Distribution
  • Breast Cancer
  • Proteins
  • Epigenetics
  • Signal Transduction
  • Genetic Therapy
  • Lung Cancer
  • Stomach Cancer
  • Promoter Regions
  • Immunohistochemistry
  • Squamous Cell Carcinoma
  • Cell Proliferation
  • Transcription Factors
  • Repressor Proteins
  • Signal Transducing Adaptor Proteins
  • alpha-Fetoproteins
  • Western Blotting
  • Chromosome 11
  • Umbilical Veins
  • Membrane Proteins
  • ras Proteins
  • Adenoviridae
  • Transfection
  • Wnt Signaling Pathway
  • Intercellular Signaling Peptides and Proteins
  • DNA Methylation
  • Staging
  • CpG Islands
  • Prostate Cancer
  • Adolescents
  • Adenocarcinoma
  • siRNA
  • Proto-Oncogene Proteins
  • Young Adult
  • Down-Regulation
  • Wnt1 Protein
  • Cervical Cancer
Tag cloud generated 27 February, 2015 using data from PubMed, MeSH and CancerIndex

Specific Cancers (5)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: DKK3 (cancer-related)

Song B, Ji W, Guo S, et al.
miR-545 inhibited pancreatic ductal adenocarcinoma growth by targeting RIG-I.
FEBS Lett. 2014; 588(23):4375-81 [PubMed] Related Publications
Pancreatic ductal adenocarcinoma (PDAC) ranks fourth on the list of cancer-related causes of death. Deregulation or dysfunction of miRNAs contribute to cancer development. In this study, we found that low miR-545 level and high RIG-I protein in PDAC tissues were both correlated with low survival rate. MiR-545 up-regulation inhibited PDAC cell lines growth and vice versa. 3'UTR of RIG-I was targeted by miR-545. Thus we concluded that low miR-545 levels in PDAC promote tumor cells growth, and this is associated with reduced survival in PDAC patients. MiR-545 exerts its effects by directly targeting RIG-1.

Bhoopathi P, Quinn BA, Gui Q, et al.
Pancreatic cancer-specific cell death induced in vivo by cytoplasmic-delivered polyinosine-polycytidylic acid.
Cancer Res. 2014; 74(21):6224-35 [PubMed] Article available free on PMC after 01/11/2015 Related Publications
Polyinosine-polycytidylic acid [pIC] is a synthetic dsRNA that acts as an immune agonist of TLR3 and RLR to activate dendritic and natural killer cells that can kill tumor cells. pIC can also trigger apoptosis in pancreatic ductal adenocarcinoma cells (PDAC) but its mechanism of action is obscure. In this study, we investigated the potential therapeutic activity of a formulation of pIC with polyethylenimine ([pIC](PEI)) in PDAC and investigated its mechanism of action. [pIC](PEI) stimulated apoptosis in PDAC cells without affecting normal pancreatic epithelial cells. Mechanistically, [pIC](PEI) repressed XIAP and survivin expression and activated an immune response by inducing MDA-5, RIG-I, and NOXA. Phosphorylation of AKT was inhibited by [pIC](PEI) in PDAC, and this event was critical for stimulating apoptosis through XIAP and survivin degradation. In vivo administration of [pIC](PEI) inhibited tumor growth via AKT-mediated XIAP degradation in both subcutaneous and quasi-orthotopic models of PDAC. Taken together, these results offer a preclinical proof-of-concept for the evaluation of [pIC](PEI) as an immunochemotherapy to treat pancreatic cancer.

Satoh T, Wada R, Yajima N, et al.
Tumor microenvironment and RIG-I signaling molecules in Epstein Barr virus-positive and -negative classical Hodgkin lymphoma of the elderly.
J Clin Exp Hematop. 2014; 54(1):75-84 [PubMed] Related Publications
Classical Hodgkin lymphoma (CHL) is a B-cell neoplasm characterized by Hodgkin and Reed-Sternberg (HRS) cells. Its prevalence exhibits a bimodal pattern of peaking in young adults and the elderly. There is an association with Epstein-Barr virus (EBV) infection in about 50% of cases of CHL of the elderly, and the outcome of these patients is unfavorable. It is not well known how the latent infection of EBV is involved in the pathophysiology of CHL of the elderly. To address this issue, we examined the tumor microenvironment (TME) and the expression of molecules related to EBV infection in HRS cells in 10 EBV-positive CHL and 7 EBV-negative CHL patients older than 50 years. In EBV-positive CHL, we found an increased population of FOXP3(+) cells, while that of granzyme B(+) cells was reduced, compared with those in EBV-negative CHL. The expression of inhibitory chemokine CCL20 was increased in EBV-positive HRS cells compared with that in EBV-negative HRS cells. In addition, despite increased expression of a pattern recognition receptor, RIG-I, in intracellular innate immunity, there was no evidence of interferon regulatory factor 3 activation or interferon-ß induction in EBV-positive HRS cells in CHL of the elderly. The disease recurred frequently (50%) in EBV-positive CHL. The current study thus suggests the possibility that the latent infection of EBV alters the expression of chemokines and the innate immunity response in HRS cells and modulates TME to an immunosuppressive state, which may account for the unfavorable disease course in CHL of the elderly.

Wu MY, Xie X, Xu ZK, et al.
PP2A inhibitors suppress migration and growth of PANC-1 pancreatic cancer cells through inhibition on the Wnt/β-catenin pathway by phosphorylation and degradation of β-catenin.
Oncol Rep. 2014; 32(2):513-22 [PubMed] Article available free on PMC after 01/11/2015 Related Publications
Cantharidin is an active constituent of mylabris, a traditional Chinese medicine, and presents strong anticancer activity in various cell lines. Cantharidin is a potent and selective inhibitor of serine/threonine protein phosphatase 2A (PP2A). Our previous studies revealed the prospect of application of cantharidin, as well as other PP2A inhibitors, in the treatment of pancreatic cancer. However, the mechanisms involved in the anticancer effect of PP2A inhibitors have not been fully explored. The Wnt/β‑catenin pathway is involved in cell migration and proliferation and participates in the progression of pancreatic cancer. If β‑catenin is phosphorylated and degraded, the Wnt/β‑catenin pathway is blocked. PP2A dephosphorylates β‑catenin and keeps the Wnt/β‑catenin pathway active. In the present study, we found that PP2A inhibitor treatment induced phosphorylation and degradation of β‑catenin. The suppression on the migration and growth of PANC‑1 pancreatic cancer cells could be attenuated by pretreatment with FH535, a β‑catenin pathway inhibitor. Microarray showed that PP2A inhibitor treatment induced expression changes in 13 of 138 genes downstream of the β‑catenin pathway. Real‑time PCR further confirmed that FH535 attenuated the expression changes induced by PP2A inhibitors in 6 of these 13 candidate genes. These 6 genes, VEGFB, Dkk3, KRT8, NRP1, Cacnalg and WISP2, have been confirmed to participate in the migration and/or growth regulation in previous studies. Thus, the phosphorylation- and degradation-mediated suppression on β‑catenin participates in the cytotoxicity of PP2A inhibitors. Our findings may provide insight into the treatment of pancreatic cancer using a targeting PP2A strategy.

Farkas SA, Vymetalkova V, Vodickova L, et al.
DNA methylation changes in genes frequently mutated in sporadic colorectal cancer and in the DNA repair and Wnt/β-catenin signaling pathway genes.
Epigenomics. 2014; 6(2):179-91 [PubMed] Related Publications
AIM: The onset and progression of colorectal cancer (CRC) involves a cascade of genetic and/or epigenetic events. The aim of the present study was to address the DNA methylation status of genes relevant in colorectal carcinogenesis and its progression, such as genes frequently mutated in CRC, genes involved in the DNA repair and Wnt signaling pathway.
MATERIAL & METHODS: We analyzed methylation status in totally 160 genes in 12 paired colorectal tumors and adjacent healthy mucosal tissues using the Illumina Infinium Human Methylation 450 BeadChip.
RESULTS: We found significantly aberrant methylation in 23 genes (NEIL1, NEIL3, DCLRE1C, NHEJ1, GTF2H5, CCNH, CTNNB1, DKK2, DKK3, FZD5 LRP5, TLE3, WNT2, WNT3A, WNT6, TCF7L1, CASP8, EDNRB1, GPC6, KIAA1804, MYO1B, SMAD2 and TTN). External validation by mRNA expression showed a good agreement between hypermethylation in cancer and down-regulated mRNA expression of the genes EDNRB1, GPC6 and SMAD2, and between hypomethylation and up-regulated mRNA expression of the CASP8 and DCLRE1C genes.
CONCLUSION: Aberrant methylation of the DCLRE1C and GPC6 genes are presented here for the first time and are therefore of special interest for further validation as novel candidate biomarker genes in CRC, and merit further validation with specific assays.

Fatima S, Luk JM, Poon RT, Lee NP
Dysregulated expression of dickkopfs for potential detection of hepatocellular carcinoma.
Expert Rev Mol Diagn. 2014; 14(5):535-48 [PubMed] Related Publications
The prognosis for hepatocellular carcinoma (HCC) remains dismal due to the lack of diagnostic markers for early detection. This review will discuss the clinical potential of the dickkopf (DKK) family members as diagnostic and/or prognostic markers for HCC. In comparison to serum α-fetoprotein (AFP) level, which remains the gold standard for HCC diagnosis, high serum DKK1 levels have higher diagnostic value for HCC, especially for AFP-negative HCC, and can distinguish HCC from non-malignant chronic liver diseases. Additionally, the combination of serum DKK1 and AFP levels enhances diagnostic accuracy for HCC compared to serum DKK1 or AFP levels alone. Although DKK1 offers potential for its use in HCC diagnosis this review will discuss the challenges facing DKK1 and also shed some light on recent developments on the remaining DKK family members: DKK2, DKK3 and DKK4.

Guo CC, Zhang XL, Yang B, et al.
Decreased expression of Dkk1 and Dkk3 in human clear cell renal cell carcinoma.
Mol Med Rep. 2014; 9(6):2367-73 [PubMed] Related Publications
The expression patterns of the Dickkopf (Dkk) family of proteins varies in different cancers. In the present study, the expression levels of Dkk1 and Dkk3 were investigated in clear cell renal cell carcinoma (ccRCC) tissues. Dkk1 and Dkk3 serum levels were also examined in patients with ccRCC, and the association between clinicopathological features and Dkk levels was investigated. Serum Dkk1 and Dkk3 were quantified using ELISA in 64 patients with ccRCC and in 30 healthy individuals (controls). The expression levels of Dkk1 and Dkk3 were analyzed in tumor and adjacent normal tissues obtained from patients with ccRCC (n=20) using quantitative polymerase chain reaction (qPCR), western blot analysis and immunohistochemistry. The mean serum levels of Dkk1 and Dkk3 in the patients with ccRCC were significantly lower than those in the healthy controls. Furthermore, the serum Dkk1 levels were significantly lower at higher tumor‑node‑metastasis stages and tumor grades. qPCR, western blot analysis and immunohistochemistry revealed a significant decrease in the Dkk1 and Dkk3 mRNA and protein levels in the tumor tissues compared with the adjacent normal tissues. Consequently, Dkk1 and Dkk3 may present a novel molecular target for the diagnosis and therapeutic treatment of ccRCC.

Balogh A, Bátor J, Markó L, et al.
Gene expression profiling in PC12 cells infected with an oncolytic Newcastle disease virus strain.
Virus Res. 2014; 185:10-22 [PubMed] Related Publications
Although the oncolytic potential of natural, non-engineered Newcastle disease virus (NDV) isolates are well-known, cellular mechanisms determining NDV sensitivity of tumor cells are poorly understood. The aim of the present study was to look for gene expression changes in PC12 pheochromocytoma cells infected with an attenuated NDV strain that may be related to NDV susceptibility. PC12 cells were infected with the NDV strain MTH-68/H for 12h at a titer corresponding to the IC₅₀ value. Total cytoplasmic RNA samples isolated from control and MTH-68/H-infected cells were analyzed using a rat specific Affymetrix exon chip. Genes with at least 2-fold increase or decrease in their expression were identified. MTH-68/H-induced gene expression changes of 9 genes were validated using quantitative reverse transcriptase PCR. A total of 729 genes were up- and 612 genes were down-regulated in PC12 cells infected with MTH-68/H. Using the DAVID functional annotation clustering tool, the up- and down-regulated genes can be categorized into 176 and 146 overlapping functional gene clusters, respectively. Gene expression changes affecting the most important signaling mechanisms (Toll-like receptor signaling, RIG-I-like receptor signaling, interferon signaling, interferon effector pathways, apoptosis pathways, endoplasmic reticulum stress pathways, cell cycle regulation) are analyzed and discussed in detail in this paper. NDV-induced gene expression changes described in this paper affect several regulatory mechanisms and dozens of putative key proteins that may determine the NDV susceptibility of various tumors. Further characterization of these proteins may identify susceptibility markers to predict the chances of virotherapeutic treatment of human tumors.

RIG-I inhibits SRC-mediated AKT/mTOR signaling and stemness in AML.
Cancer Discov. 2014; 4(3):OF19 [PubMed] Related Publications
RIG-I biases myeloid cells toward differentiation and autophagy via suppression of AKT/mTOR.

Matsumiya T, Hayakari R, Narita N, et al.
Role of type I- and type II-interferon in expression of melanoma differentiation-associated gene-5 in HSC-3 oral squamous carcinoma cells.
Biomed Res. 2014; 35(1):9-16 [PubMed] Related Publications
Melanoma differentiation-associated gene 5 (MDA-5) and retinoic acid-inducible gene-I (RIG-I)are members of DExH family of proteins, and known to play important roles in antiviral responses to induce type I interferons (IFNs). MDA-5 has been thought to sense RNA virus with long(>1 kb) double-stranded RNA. However, MDA-5 is also induced by type II IFN that is involved in acquired immunity, suggesting that role of MDA-5 remains to be elucidated. In addition, no study regarding MDA-5 in oral region has been performed. Here we investigated the role of MDA-5 in HCS-3 squamous carcinoma cells derived from oral epithelial cells. Treatment of HCS-3 cells with IFN-α2b or IFN-γ significantly induced MDA-5 as well as RIG-I. IFN-α2b exerted anti-proliferative effect in HSC-3 cells while no such effect was observed in the cells treated with IFN-γ. MDA-5 is known to be associated with tumor cell growth in melanoma. However, overexpression of MDA-5 did not alter the proliferation in HSC-3 cells, indicating that MDA-5 is unrelated to the cell growth in this type of cells. We conclude that MDA-5 is induced by both type I- and type II-IFNs in HSC-3 cells, and this suggests MDA-5 may play a role in immune responses in oral cavity.

Shien K, Tanaka N, Watanabe M, et al.
Anti-cancer effects of REIC/Dkk-3-encoding adenoviral vector for the treatment of non-small cell lung cancer.
PLoS One. 2014; 9(2):e87900 [PubMed] Article available free on PMC after 01/11/2015 Related Publications
OBJECTIVES: REIC/Dkk-3 is down-regulated in a broad range of human cancer cells and is considered to function as a tumor suppressor. We previously reported that REIC/Dkk-3-expressing adenovirus vector (Ad-REIC) induced endoplasmic reticulum (ER) stress and cancer-specific apoptosis in human prostate cancer. In this study, we examined the therapeutic impact of Ad-REIC on non-small cell lung cancer (NSCLC).
MATERIALS AND METHODS: We examined the anti-tumor effect of Ad-REIC on 25 NSCLC cell lines in vitro and A549 cells in vivo. Two of these cell lines were artificially established as EGFR-tyrosine kinase inhibitor (TKI) resistant sublines.
RESULTS: Ad-REIC-treatment inhibited the cell viability by 40% or more in 13 (52%) of the 25 cell lines at multiplicity of infection (MOI) of 20 (20 MOI). These cell lines were regarded as being highly sensitive cells. The cell viability of a non-malignant immortalized cell line, OUMS-24, was not inhibited at 200 MOI of Ad-REIC. The effects of Ad-REIC on EGFR-TKI resistant sublines were equivalent to those in the parental cell lines. Here, we demonstrated that Ad-REIC treatment activated c-Jun N-terminal kinase (JNK) in NSCLC cell lines, indicating the induction of ER stress with GRP78/BiP (GRP78) up-regulation and resulting in apoptosis. A single intratumoral injection of Ad-REIC significantly inhibited the tumorigenic growth of A549 cells in vivo. As predictive factors of sensitivity for Ad-REIC treatment in NSCLC, we examined the expression status of GRP78 and coxsackievirus and adenovirus receptor (CAR). We found that the combination of the GRP78 and CAR expressional statuses may be used as a predictive factor for Ad-REIC sensitivity in NSCLC cells.
CONCLUSION: Ad-REIC induced JNK activation and subsequent apoptosis in NSCLC cells. Our study indicated that Ad-REIC has therapeutic potential against NSCLC and that the expression statuses of GRP78 and CAR may predict a potential therapeutic benefit of Ad-REIC.

Widau RC, Parekh AD, Ranck MC, et al.
RIG-I-like receptor LGP2 protects tumor cells from ionizing radiation.
Proc Natl Acad Sci U S A. 2014; 111(4):E484-91 [PubMed] Article available free on PMC after 01/11/2015 Related Publications
An siRNA screen targeting 89 IFN stimulated genes in 14 different cancer cell lines pointed to the RIG-I (retinoic acid inducible gene I)-like receptor Laboratory of Genetics and Physiology 2 (LGP2) as playing a key role in conferring tumor cell survival following cytotoxic stress induced by ionizing radiation (IR). Studies on the role of LGP2 revealed the following: (i) Depletion of LGP2 in three cancer cell lines resulted in a significant increase in cell death following IR, (ii) ectopic expression of LGP2 in cells increased resistance to IR, and (iii) IR enhanced LGP2 expression in three cell lines tested. Studies designed to define the mechanism by which LGP2 acts point to its role in regulation of IFNβ. Specifically (i) suppression of LGP2 leads to enhanced IFNβ, (ii) cytotoxic effects following IR correlated with expression of IFNβ inasmuch as inhibition of IFNβ by neutralizing antibody conferred resistance to cell death, and (iii) mouse embryonic fibroblasts from IFN receptor 1 knockout mice are radioresistant compared with wild-type mouse embryonic fibroblasts. The role of LGP2 in cancer may be inferred from cumulative data showing elevated levels of LGP2 in cancer cells are associated with more adverse clinical outcomes. Our results indicate that cytotoxic stress exemplified by IR induces IFNβ and enhances the expression of LGP2. Enhanced expression of LGP2 suppresses the IFN stimulated genes associated with cytotoxic stress by turning off the expression of IFNβ.

Li XY, Jiang LJ, Chen L, et al.
RIG-I modulates Src-mediated AKT activation to restrain leukemic stemness.
Mol Cell. 2014; 53(3):407-19 [PubMed] Related Publications
Retinoic acid (RA)-inducible gene I (RIG-I) is highly upregulated and functionally implicated in the RA-induced maturation of acute myeloid leukemia (AML) blasts. However, the underlying mechanism and the biological relevance of RIG-I expression to the maintenance of leukemogenic potential are poorly understood. Here, we show that RIG-I, without priming by foreign RNA, inhibits the Src-facilitated activation of AKT-mTOR in AML cells. Moreover, in a group of primary human AML blasts, RIG-I reduction renders the Src family kinases hyperactive in promoting AKT activation. Mechanistically, a PxxP motif in RIG-I, upon the N-terminal CARDs' association with the Src SH1 domain, competes with the AKT PxxP motif for recognizing the Src SH3 domain. In accordance, mutating PxxP motif prevents Rig-I from inhibiting AKT activation, cytokine-stimulated myeloid progenitor proliferation, and in vivo repopulating capacity of leukemia cells. Collectively, our data suggest an antileukemia activity of RIG-I via competitively inhibiting Src/AKT association.

Watanabe M, Sakaguchi M, Kinoshita R, et al.
A novel gene expression system strongly enhances the anticancer effects of a REIC/Dkk-3-encoding adenoviral vector.
Oncol Rep. 2014; 31(3):1089-95 [PubMed] Article available free on PMC after 01/11/2015 Related Publications
Gene expression systems with various promoters, including the cytomegalovirus (CMV) promoter, have been developed to increase the gene expression in a variety of normal and cancer cells. In particular, in the clinical trials of cancer gene therapy, a more efficient and robust gene expression system is required to achieve sufficient therapeutic outcomes. By inserting the triple translational enhancer sequences of human telomerase reverse transcriptase (hTERT), Simian virus 40 (SV40) and CMV downstream of the sequence of the BGH polyA, we were able to develop a novel gene expression system that significantly enhances the expression of the genes of interest. We termed this novel gene expression cassette the super gene expression (SGE) system, and herein verify the utility of the SGE cassette for a replication-deficient adenoviral vector. We newly developed an adenoviral vector expressing the tumor suppressor, reduced expression in immortalized cells (REIC)/Dickkopf-3 (Dkk-3), based on the CMV promoter-driven SGE system (Ad-SGE-REIC) and compared the therapeutic utility of Ad-SGE-REIC with that of the conventional adenoviral vectors (Ad-CMV-REIC or Ad-CAG-REIC). The results demonstrated that the CMV promoter-SGE system allows for more potent gene expression, and that the Ad-SGE-REIC is superior to conventional adenoviral systems in terms of the REIC protein expression and therapeutic effects. Since the SGE cassette can be applied for the expression of various therapeutic genes using various vector systems, we believe that this novel system will become an innovative tool in the field of gene expression and gene therapy.

Uchida D, Shiraha H, Kato H, et al.
Potential of adenovirus-mediated REIC/Dkk-3 gene therapy for use in the treatment of pancreatic cancer.
J Gastroenterol Hepatol. 2014; 29(5):973-83 [PubMed] Related Publications
BACKGROUND AND AIM: The reduced expression in immortalized cells REIC/the dickkopf 3 (Dkk-3) gene, tumor suppressor gene, is downregulated in various malignant tumors. In a prostate cancer study, an adenovirus vector carrying the REIC/Dkk-3 gene (Ad-REIC) induces apoptosis. In the current study, we examined the effects of REIC/Dkk-3 gene therapy in pancreatic cancer.
METHODS: REIC/Dkk-3 expression was assessed by immunoblotting and immunohistochemistry in the pancreatic cancer cell lines (ASPC1, MIAPaCa2, Panc1, BxPC3, SUIT-2, KLM1, and T3M4) and pancreatic cancer tissues. The Ad-REIC agent was used to investigate the apoptotic effect in vitro and antitumor effects in vivo. We also assessed the therapeutic effects of Ad-REIC therapy with gemcitabine.
RESULTS: The REIC/Dkk-3 expression was lost in the pancreatic cancer cell lines and decreased in pancreatic cancer tissues. Ad-REIC induced apoptosis and inhibited cell growth in the ASPC1 and MIAPaCa2 lines in vitro, and Ad-REIC inhibited tumor growth in the mouse xenograft model using ASPC1 cells. The antitumor effect was further enhanced in combination with gemcitabine. This synergistic effect may be caused by the suppression of autophagy via the enhancement of mammalian target of rapamycin signaling.
CONCLUSIONS: Ad-REIC induces apoptosis and inhibits tumor growth in pancreatic cancer cell lines. REIC/Dkk-3 gene therapy is an attractive therapeutic tool for pancreatic cancer.

Hou J, Zhou Y, Zheng Y, et al.
Hepatic RIG-I predicts survival and interferon-α therapeutic response in hepatocellular carcinoma.
Cancer Cell. 2014; 25(1):49-63 [PubMed] Related Publications
In hepatocellular carcinoma (HCC), biomarkers for prediction of prognosis and response to immunotherapy such as interferon-α (IFN-α) would be very useful in the clinic. We found that expression of retinoic acid-inducible gene-I (RIG-I), an IFN-stimulated gene, was significantly downregulated in human HCC tissues. Patients with low RIG-I expression had shorter survival and poorer response to IFN-α therapy, suggesting that RIG-I is a useful prognosis and IFN-α response predictor for HCC patients. Mechanistically, RIG-I enhances IFN-α response by amplifying IFN-α effector signaling via strengthening STAT1 activation. Furthermore, we found that RIG-I deficiency promotes HCC carcinogenesis and that hepatic RIG-I expression is lower in men than in women. RIG-I may therefore be a tumor suppressor in HCC and contribute to HCC gender disparity.

Voorham QJ, Janssen J, Tijssen M, et al.
Promoter methylation of Wnt-antagonists in polypoid and nonpolypoid colorectal adenomas.
BMC Cancer. 2013; 13:603 [PubMed] Article available free on PMC after 01/11/2015 Related Publications
BACKGROUND: Nonpolypoid adenomas are a subgroup of colorectal adenomas that have been associated with a more aggressive clinical behaviour compared to their polypoid counterparts. A substantial proportion of nonpolypoid and polypoid adenomas lack APC mutations, APC methylation or chromosomal loss of the APC locus on chromosome 5q, suggesting the involvement of other Wnt-pathway genes. The present study investigated promoter methylation of several Wnt-pathway antagonists in both nonpolypoid and polypoid adenomas.
METHODS: Quantitative methylation-specific PCR (qMSP) was used to evaluate methylation of four Wnt-antagonists, SFRP2, WIF-1, DKK3 and SOX17 in 18 normal colorectal mucosa samples, 9 colorectal cancer cell lines, 18 carcinomas, 44 nonpolypoid and 44 polypoid adenomas. Results were integrated with previously obtained data on APC mutation, methylation and chromosome 5q status from the same samples.
RESULTS: Increased methylation of all genes was found in the majority of cell lines, adenomas and carcinomas compared to normal controls. WIF-1 and DKK3 showed a significantly lower level of methylation in nonpolypoid compared to polypoid adenomas (p < 0.01). Combining both adenoma types, a positive trend between APC mutation and both WIF-1 and DKK3 methylation was observed (p < 0.05).
CONCLUSIONS: Methylation of Wnt-pathway antagonists represents an additional mechanism of constitutive Wnt-pathway activation in colorectal adenomas. Current results further substantiate the existence of partially alternative Wnt-pathway disruption mechanisms in nonpolypoid compared to polypoid adenomas, in line with previous observations.

Li Q, Shen K, Zhao Y, et al.
MiR-92b inhibitor promoted glioma cell apoptosis via targeting DKK3 and blocking the Wnt/beta-catenin signaling pathway.
J Transl Med. 2013; 11:302 [PubMed] Article available free on PMC after 01/11/2015 Related Publications
BACKGROUND: MiR-92b was upregulated in gliomas. However, the association of miR-92b with glioma cell apoptosis and survival remains unknown.
METHODS: Proliferation capability of glioma cells upon tranfection with miR-92b mimics or inhibitors was detected by mutiple analyses, including MTT assays, colony formation assay. Apoptosis abilities of glioma cells were detected by flow cytometric analysis. The target of miR-92b was determined by luciferase reporter and western blot. The association of miR-92b with outcome was examined in twenty glioma patients.
RESULTS: MiR-92b expression was significantly increased in high-grade gliomas compared with low-grade gliomas, and positively correlated with the degree of glioma infiltration. Over-expression of miR-92b increased cell proliferation, whereas knockdown of miR-92b decreased cell proliferation via modulating the levels of the target, Target prediction analysis and a dual luciferase reporting assay confirmed that the inhibitory protein-coding Dickkopf-3 gene (DKK3) was a direct target of miR-92b. Furthermore, miR-92b could regulate the expression of downstream genes of the Wnt/beta-catenin signaling pathway, such as Bcl2, c-myc and p-c-Jun, in glioma cells. Finally, the increased level of miR-92b expression in high-grade gliomas confers poorer overall survival.
CONCLUSIONS: The present data indicates that miR-92b directly regulate cell proliferation and apoptosis by targeting DKK3 and act as prognostic factors for glioma patients.

Qu J, Hou Z, Han Q, et al.
Poly(I:C) exhibits an anti-cancer effect in human gastric adenocarcinoma cells which is dependent on RLRs.
Int Immunopharmacol. 2013; 17(3):814-20 [PubMed] Related Publications
Poly(I:C), an agonist of TLR3 and RLRs, has been used as an immune adjuvant in clinical trials for many years. Although it has been found to trigger apoptosis in a variety of cancers, its mechanisms in human gastric adenocarcinoma is unclear. The purpose of this study was to assess the effect of poly(I:C) on human gastric adenocarcinoma cells. Our observations showed that intracellular delivery of poly(I:C) by liposomes had a pro-apoptotic effect in vitro, and significantly inhibited xenograft growth of human gastric adenocarcinoma in nude mice. Further investigations indicated that RLRs, as intrinsic RNA sensors, contributed to the poly(I:C)-triggered apoptotic effect through upregulation of RIG-I, MDA-5, and most significantly, LGP2, accompanied by increased expression of Bcl-2 family members. Conversely, this apoptotic effect was greatly reduced by silencing RIG-I, MDA-5, or LGP2. Although LGP2 is considered an innate immune negative regulator of RIG-I and MDA-5, it exhibited a positive regulatory effect on poly(I:C)-induced apoptosis in human gastric adenocarcinoma cells. These findings suggested that poly(I:C) may be a promising chemotherapeutic agent against human gastric adenocarcinoma.

Konac E, Varol N, Yilmaz A, et al.
DNA methyltransferase inhibitor-mediated apoptosis in the Wnt/β-catenin signal pathway in a renal cell carcinoma cell line.
Exp Biol Med (Maywood). 2013; 238(9):1009-16 [PubMed] Related Publications
The Wnt signaling pathway is activated in most cancer types when Wnt antagonist genes are inactivated. Glycogen synthase kinase 3 (GSK3β) is an important regulator of the Wnt/β-catenin signaling pathway. The mechanisms underlying GSK3β regulation of neoplastic transformation and tumor development are unclear. Studies have raised the possibility that the Wnt signaling pathway may be implicated in renal cell carcinoma (RCC). Therefore, in the present study, we hypothesize that the expression and methylation status of the secreted frizzled-related protein 2 (sFRP2) gene, one of the secreted antagonists that bind Wnt protein, and re-expression of this gene with the demethylation agent (5-aza-2'-deoxycytidine; DAC) may induce apoptosis in RCC cells. To test this hypothesis, we investigated the relationship among epigenetic inactivation of sFRP2 and p-GSK3β (Ser9) and other Wnt antagonists (sFRP1, DKK3, WIF-1) and apoptotic factors (Bax and Caspase3) as well as the anti-apoptotic factor BCL2. Our results indicate that DAC-mediated inhibition of DNA methylation led to a re-activation of sFRP2 expression and increased expression levels of the Wnt antagonists and apoptotic factors. In contrast, the level of β-catenin (CTNNB1) expression decreased. The p-GSK3β (Ser9) protein level in Caki-2 cells was significantly down-regulated, while the DNA fragmentation rate increased after treatment with 5 μM DAC at 96 h. Our data show that sFRP2 functions as a tumor suppressor gene in RCC and that its restoration may offer a new therapeutic approach for the treatment of RCC. Moreover, our study draws attention to the regulatory features of epigenetic molecules and analyses their underlying molecular mechanisms of action and their potential use in clinical practice.

Meng G, Xia M, Xu C, et al.
Multifunctional antitumor molecule 5'-triphosphate siRNA combining glutaminase silencing and RIG-I activation.
Int J Cancer. 2014; 134(8):1958-71 [PubMed] Related Publications
Resisting cell death, reprogrammed metabolism and immune escape are fundamental traits of hard-to-treat cancers. Therapeutic improvement can be expected by designing drugs targeting all three aspects. 5'-Triphosphate RNA (ppp-RNA), a specific ligand of the pattern recognition receptor retinoic acid-inducible gene I (RIG-I), has been shown to trigger intrinsic apoptosis of malignant cells and to activate antitumor immune responses via type I interferons (IFNs). In our study, we designed a ppp-modified siRNA specifically silencing glutaminase (ppp-GLS), a key enzyme of glutaminolysis that is indispensable for many cancer types. Bifunctional ppp-GLS induced more prominent antitumor responses than RNA molecules that contained either the RIG-I ligand motif or GLS silencing capability alone. The cytopathic effect was constrained to tumor cells as nonmalignant cells were not affected. We then analyzed the mechanisms leading to the profound antitumor efficacy. First, ppp-GLS effectively induced intrinsic proapoptotic signaling. In addition, GLS silencing sensitized malignant cells to RIG-I-induced apoptosis. Moreover, disturbed glutaminolysis by GLS silencing contributed to enhanced cytotoxicity. Finally, RIG-I activation blocked autophagic degradation leading to dysfunctional mitochondria and reactive oxygen species (ROS) generation, whereas GLS silencing severely impaired ROS scavenging systems, leading to a vicious circle of ROS-mediated cytotoxicity. Taken together, ppp-GLS combines cell death induction, immune activation and glutaminase inhibition in a single molecule and has high therapeutic efficacy against cancer cells.

Xiang T, Li L, Yin X, et al.
Epigenetic silencing of the WNT antagonist Dickkopf 3 disrupts normal Wnt/β-catenin signalling and apoptosis regulation in breast cancer cells.
J Cell Mol Med. 2013; 17(10):1236-46 [PubMed] Article available free on PMC after 01/11/2015 Related Publications
Dickkopf-related protein 3 (DKK3) is an antagonist of Wnt ligand activity. Reduced DKK3 expression has been reported in various types of cancers, but its functions and related molecular mechanisms in breast tumorigenesis remain unclear. We examined the expression and promoter methylation of DKK3 in 10 breast cancer cell lines, 96 primary breast tumours, 43 paired surgical margin tissues and 16 normal breast tissues. DKK3 was frequently silenced in breast cell lines (5/10) by promoter methylation, compared with human normal mammary epithelial cells and tissues. DKK3 methylation was detected in 78% of breast tumour samples, whereas only rarely methylated in normal breast and surgical margin tissues, suggesting tumour-specific methylation of DKK3 in breast cancer. Ectopic expression of DKK3 suppressed cell colony formation through inducing G0/G1 cell cycle arrest and apoptosis of breast tumour cells. DKK3 also induced changes of cell morphology, and inhibited breast tumour cell migration through reversing epithelial-mesenchymal transition (EMT) and down-regulating stem cell markers. DKK3 inhibited canonical Wnt/β-catenin signalling through mediating β-catenin translocation from nucleus to cytoplasm and membrane, along with reduced active-β-catenin, further activating non-canonical JNK signalling. Thus, our findings demonstrate that DKK3 could function as a tumour suppressor through inducing apoptosis and regulating Wnt signalling during breast tumorigenesis.

Takahashi M, Wolf AM, Watari E, et al.
Increased mitochondrial functions in human glioblastoma cells persistently infected with measles virus.
Antiviral Res. 2013; 99(3):238-44 [PubMed] Related Publications
Measles virus (MV) is known for its ability to cause an acute infection with a potential of development of persistent infection. However, knowledge of how viral genes and cellular factors interact to cause or maintain the persistent infection has remained unclear. We have previously reported the possible involvement of mitochondrial short chain enoyl-CoA hydratase (ECHS), which is localized at mitochondria, in the regulation of MV replication. In this study we found increased functions of mitochondria in MV-persistently infected cells compared with uninfected or acutely infected cells. Furthermore, impairment of mitochondrial functions by treatment with mitochondrial inhibitors such as ethidium bromide (EtBr) or carbonyl cyanide-p-trifluoromethoxyphenylhydrazone (FCCP) induced the cytopathic effects of extensive syncytial formation in persistently infected cells. These findings suggest that mitochondria are one of the subcellular organelles contributing to regulate persistent infection of MV. Recent studies showed mitochondria provide an integral platform for retinoic acid-inducible protein (RIG-I)-like cytosolic receptors (RLRs) signaling and participate in cellular innate antiviral immunity. Our findings not only reveal a role of mitochondria in RLR mediated antiviral signaling but also suggest that mitochondria contribute to the regulation of persistent viral infection.

Páez D, Gerger A, Zhang W, et al.
Association of common gene variants in the WNT/β-catenin pathway with colon cancer recurrence.
Pharmacogenomics J. 2014; 14(2):142-50 [PubMed] Related Publications
Wnt/β-catenin signaling has a central role in the development and progression of most colon cancers (CCs). Germline variants in Wnt/β-catenin pathway genes may result in altered gene function and/or activity, thereby causing inter-individual differences in relation to tumor recurrence capacity and chemoresistance. We investigated germline polymorphisms in a comprehensive panel of Wnt/β-catenin pathway genes to predict time to tumor recurrence (TTR) in patients with stage III and high-risk stage II CC. A total of 234 patients treated with 5-fluorouracil-based chemotherapy were included in this study. Whole-blood samples were analyzed for putative functional germline polymorphisms in SFRP3, SFRP4, DKK2, DKK3, Axin2, APC, TCF7L2, WNT5B, CXXC4, NOTCH2 and GLI1 genes by PCR-based restriction fragment-length polymorphism or direct DNA sequencing. Polymorphisms with statistical significance were validated in an independent study cohort. The minor allele of WNT5B rs2010851 T>G was significantly associated with a shorter TTR (10.7 vs 4.9 years; hazard ratio: 2.48; 95% CI, 0.96-6.38; P=0.04) in high-risk stage II CC patients. This result remained significant in multivariate Cox's regression analysis. This study shows that the WNT5B germline variant rs2010851 was significantly identified as a stage-dependent prognostic marker for CC patients after 5-fluorouracil-based adjuvant therapy.

Tanaka S, Aida K, Nishida Y, Kobayashi T
Pathophysiological mechanisms involving aggressive islet cell destruction in fulminant type 1 diabetes.
Endocr J. 2013; 60(7):837-45 [PubMed] Related Publications
Fulminant type 1 diabetes is characterized by a rapid onset of severe hyperglycemia and ketoacidosis, with subsequent poor prognosis of diabetic complications. This review summarizes new findings related to the pathophysiology of accelerated β-cell failure in fulminant type 1 diabetes. Immunohistological examination revealed the presence of enterovirus in pancreatic islet cells and exocrine tissues and hyperexpression of pattern recognition receptors (PRRs) including melanoma differentiation-associated antigen 5 (MDA5), retinoic acid-inducible gene-I (RIG-I), Toll-like receptor (TLR)3 and TLR4, essential sensors of innate immunity, in islet cells and mononuclear cells (MNCs) infiltrating islets. Interferon (IFN)-α and IFN-β, products of PRR cascades, were expressed in both islet cells and infiltrating MNCs. Phenotypes of infiltrating cells around and/or into islets were mainly dendritic cells, macrophages and CD8+ T cells. Islet β-cells simultaneously expressed CXC chemokine ligand 10 (CXCL10), IFN-γ and interleukin-18, indicating that these chemokines/ cytotoxic cytokines mutually amplify their cytoplasmic expression in the islet cells. These positive feedback systems might enhance adaptive immunity, leading to rapid and complete loss of β-cells in fulminant type 1 diabetes. In innate and adaptive/autoimmune immune processes, the mechanisms behind bystander activation/killing might further amplify β-cell destruction. In addition to intrinsic pathway of cell apoptosis, the Fas and Fas ligand pathway are also involved as an extrinsic pathway of cell apoptosis. A high prevalence of anti-amylase autoantibodies was recognized in patients with fulminant type 1 diabetes, which suggests that Th2 T-cell reactive immunity against amylase might contribute to β-cell destruction in fulminant type 1 diabetes.

Zenzmaier C, Sampson N, Plas E, Berger P
Dickkopf-related protein 3 promotes pathogenic stromal remodeling in benign prostatic hyperplasia and prostate cancer.
Prostate. 2013; 73(13):1441-52 [PubMed] Article available free on PMC after 01/11/2015 Related Publications
BACKGROUND: Compartment-specific epithelial and stromal expression of the secreted glycoprotein Dickkopf-related protein (Dkk)-3 is altered in age-related proliferative disorders of the human prostate. This study aimed to determine the effect of Dkk-3 on prostate stromal remodeling that is stromal proliferation, fibroblast-to-myofibroblast differentiation and expression of angiogenic factors in vitro.
METHODS: Lentiviral-delivered overexpression and shRNA-mediated knockdown of DKK3 were applied to primary human prostatic stromal cells (PrSCs). Cellular proliferation was analyzed by BrdU incorporation ELISA. Expression of Dkk-3, apoptosis-related genes, cyclin-dependent kinase inhibitors and angiogenic factors were analyzed by qPCR, Western blot analysis or ELISA. Fibroblast-to-myofibroblast differentiation was monitored by smooth muscle cell actin and insulin-like growth factor binding protein 3 mRNA and protein levels. The relevance of Wnt/β-catenin and PI3K/AKT signaling pathways was assessed by cytoplasmic/nuclear β-catenin levels and phosphorylation of AKT.
RESULTS: Knockdown of DKK3 significantly attenuated PrSC proliferation as well as fibroblast-to-myofibroblast differentiation and increased the expression of the vessel stabilizing factor angiopoietin-1. DKK3 knockdown did not affect subcellular localization or levels of β-catenin but attenuated AKT phosphorylation in PrSCs. Consistently the PI3K/AKT inhibitor LY294002 mimicked the effects of DKK3 knockdown.
CONCLUSIONS: Dkk-3 promotes fibroblast proliferation and myofibroblast differentiation and regulates expression of angiopoietin-1 in prostatic stroma potentially via enhancing PI3K/AKT signaling. Thus, elevated Dkk-3 in the stroma of the diseased prostate presumably regulates stromal remodeling by enhancing proliferation and differentiation of stromal cells and contributing to the angiogenic switch observed in BPH and PCa. Therefore, Dkk-3 represents a potential therapeutic target for stromal remodeling in BPH and PCa.

Yin DT, Wu W, Li M, et al.
DKK3 is a potential tumor suppressor gene in papillary thyroid carcinoma.
Endocr Relat Cancer. 2013; 20(4):507-14 [PubMed] Related Publications
The expression of the Dickkopf homolog 3 (DKK3) gene is downregulated in some human cancers, suggesting a possible tumor suppressor role of this gene. The role and regulation of DKK3 in thyroid cancer have not been examined. In this study, we explored the relationship of promoter methylation with the inactivation of DKK3 and tumor behaviors in papillary thyroid carcinoma (PTC). We used methylation-specific PCR and RT-PCR to examine the promoter methylation and expression of DKK3 and tumor characteristics. We found mRNA expression of DKK3 in 44.9% of the PTC tissue samples vs 100% of the matched normal thyroid tissue samples (P<0.01). In contrast, an opposite distribution pattern of DKK3 gene methylation was observed; specifically, 38.8% of the PTC tissue samples vs 0% of the matched normal thyroid tissue samples harbored DKK3 methylation. An inverse correlation between the promoter methylation and mRNA expression of DKK3 in PTC tissue samples was also observed. Moreover, we also found an inverse correlation between DKK3 expression and some aggressive pathological characteristics of PTC, including high TNM stages and lymph node metastasis, but a positive correlation between DKK3 promoter hypermethylation and pathological aggressiveness of the tumor. Treatment of the PTC cell line TPC-1 with the demethylating agent 5-azaC reduced DKK3 promoter methylation and enhanced its expression, establishing functionally the impact of DKK3 methylation on its expression. Our data thus for the first time demonstrate that the DKK3 gene is a potential tumor suppressor gene in thyroid cancer and that aberrant promoter methylation is an important mechanism for its downregulation, which may play a role in the tumorigenesis and aggressiveness of PTC.

Imaizumi T, Murakami K, Ohta K, et al.
MDA5 and ISG56 mediate CXCL10 expression induced by toll-like receptor 4 activation in U373MG human astrocytoma cells.
Neurosci Res. 2013; 76(4):195-206 [PubMed] Related Publications
Toll-like receptor (TLR) 4 is a pattern recognition receptor, and recognizes not only bacterial lipopolysaccharide (LPS) but also endogenous danger-associated molecular patterns released from dying or injured cells. It has been reported that TLR4 signaling in astrocytes plays an important role in various neurological diseases. However, details of TLR4 signaling in astrocytes are not fully elucidated. In the present study, we demonstrated that TLR4 signaling, induced by LPS, increases the expression of melanoma differentiation-associated gene 5 (MDA5) and interferon (IFN)-stimulated gene 56 (ISG56) in U373MG human astrocytoma cells. We also found that nuclear factor-κB, p38 mitogen-activated protein kinase and IFN-β are involved in the expression of MDA5 and ISG56 induced by LPS. RNA interference experiments revealed that MDA5 and ISG56 positively regulate the LPS-induced expression of a chemokine CXCL10, but not CCL2. In addition, it was suggested that MDA5 and ISG56 constitute a positive feedback loop. These results suggest that MDA5 and ISG56 may contribute not only to physiological inflammatory reactions but also to the pathogenesis of various neurological diseases elicited by TLR4 in astrocytes, at least in part, by regulating the expression of CXCL10.

Colli LM, Saggioro F, Serafini LN, et al.
Components of the canonical and non-canonical Wnt pathways are not mis-expressed in pituitary tumors.
PLoS One. 2013; 8(4):e62424 [PubMed] Article available free on PMC after 01/11/2015 Related Publications
INTRODUCTION: Canonical and non-canonical Wnt pathways are involved in the genesis of multiple tumors; however, their role in pituitary tumorigenesis is mostly unknown.
OBJECTIVE: This study evaluated gene and protein expression of Wnt pathways in pituitary tumors and whether these expression correlate to clinical outcome.
MATERIALS AND METHODS: Genes of the WNT canonical pathway: activating ligands (WNT11, WNT4, WNT5A), binding inhibitors (DKK3, sFRP1), β-catenin (CTNNB1), β-catenin degradation complex (APC, AXIN1, GSK3β), inhibitor of β-catenin degradation complex (AKT1), sequester of β-catenin (CDH1), pathway effectors (TCF7, MAPK8, NFAT5), pathway mediators (DVL-1, DVL-2, DVL-3, PRICKLE, VANGL1), target genes (MYB, MYC, WISP2, SPRY1, TP53, CCND1); calcium dependent pathway (PLCB1, CAMK2A, PRKCA, CHP); and planar cell polarity pathway (PTK7, DAAM1, RHOA) were evaluated by QPCR, in 19 GH-, 18 ACTH-secreting, 21 non-secreting (NS) pituitary tumors, and 5 normal pituitaries. Also, the main effectors of canonical (β-catenin), planar cell polarity (JNK), and calcium dependent (NFAT5) Wnt pathways were evaluated by immunohistochemistry.
RESULTS: There are no differences in gene expression of canonical and non-canonical Wnt pathways between all studied subtypes of pituitary tumors and normal pituitaries, except for WISP2, which was over-expressed in ACTH-secreting tumors compared to normal pituitaries (4.8x; p = 0.02), NS pituitary tumors (7.7x; p = 0.004) and GH-secreting tumors (5.0x; p = 0.05). β-catenin, NFAT5 and JNK proteins showed no expression in normal pituitaries and in any of the pituitary tumor subtypes. Furthermore, no association of the studied gene or protein expression was observed with tumor size, recurrence, and progressive disease. The hierarchical clustering showed a regular pattern of genes of the canonical and non-canonical Wnt pathways randomly distributed throughout the dendrogram.
CONCLUSIONS: Our data reinforce previous reports suggesting no activation of canonical Wnt pathway in pituitary tumorigenesis. Moreover, we describe, for the first time, evidence that non-canonical Wnt pathways are also not mis-expressed in the pituitary tumors.

Wang B, Xi X, Lei X, et al.
Enterovirus 71 protease 2Apro targets MAVS to inhibit anti-viral type I interferon responses.
PLoS Pathog. 2013; 9(3):e1003231 [PubMed] Article available free on PMC after 01/11/2015 Related Publications
Enterovirus 71 (EV71) is the major causative pathogen of hand, foot, and mouth disease (HFMD). Its pathogenicity is not fully understood, but innate immune evasion is likely a key factor. Strategies to circumvent the initiation and effector phases of anti-viral innate immunity are well known; less well known is whether EV71 evades the signal transduction phase regulated by a sophisticated interplay of cellular and viral proteins. Here, we show that EV71 inhibits anti-viral type I interferon (IFN) responses by targeting the mitochondrial anti-viral signaling (MAVS) protein--a unique adaptor molecule activated upon retinoic acid induced gene-I (RIG-I) and melanoma differentiation associated gene (MDA-5) viral recognition receptor signaling--upstream of type I interferon production. MAVS was cleaved and released from mitochondria during EV71 infection. An in vitro cleavage assay demonstrated that the viral 2A protease (2A(pro)), but not the mutant 2A(pro) (2A(pro)-110) containing an inactivated catalytic site, cleaved MAVS. The Protease-Glo assay revealed that MAVS was cleaved at 3 residues between the proline-rich and transmembrane domains, and the resulting fragmentation effectively inactivated downstream signaling. In addition to MAVS cleavage, we found that EV71 infection also induced morphologic and functional changes to the mitochondria. The EV71 structural protein VP1 was detected on purified mitochondria, suggesting not only a novel role for mitochondria in the EV71 replication cycle but also an explanation of how EV71-derived 2A(pro) could approach MAVS. Taken together, our findings reveal a novel strategy employed by EV71 to escape host anti-viral innate immunity that complements the known EV71-mediated immune-evasion mechanisms.

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