RECK is a target of Epstein-Barr virus latent membrane protein 1

LMP1 Induces p53 Protein Expression via the H19/miR-675-5p Axis

Epstein-Barr virus (EBV), a ubiquitous oncogenic herpesvirus, infects more than 90% of the adult population worldwide. The long noncoding RNA H19 is downregulated in EBV-positive gastric cancer (EBVaGC) and nasopharyngeal cancer (NPC). In this study, we found that loss of H19 is caused by hypermethylation status of the H19 promoter in EBV-positive GC and NPC cell lines. Furthermore, latent membrane protein 1 (LMP1), encoded by EBV, induced H19 promoter hypermethylation and deregulated the expression of H19 by upregulating DNMT1 expression. Transwell assays showed that H19 promoted cell migration. Furthermore, H19 promoted cell proliferation and inhibited apoptosis in CCK-8 and flow cytometry assays, respectively. p53, a well-known tumor suppressor, was upregulated in EBVaGC and NPC cell lines. miR-675-5p derived from H19 inhibited p53 protein expression by targeting the 3' untranslated region of the gene. Overall, we found that LMP1 induced p53 protein expression via the H19/miR-675-5p axis in EBVaGC and NPC. LMP1 induced H19 promoter hypermethylation, which repressed the expression of H19 and miR-675-5p and caused p53 protein overexpression in EBVaGC and NPC cells. IMPORTANCE Epstein-Barr virus (EBV) is the first virus to be known to have direct association with human cancer and to be considered as an important DNA tumor virus. The EBV life cycle consists of both latent and lytic modes of infection in B lymphocytes and epithelial cells. The persistence of EBV genomes in malignant cells promoted cell growth. p53, acting as a critical gatekeeper tumor suppressor, is involved in multiple virus-mediated tumorigeneses. Overexpression of p53 inhibits the ability of BZLF1 (EBV-encoded immediate early gene) to disrupt viral latency. In our study, we found LMP1 induces H19 promoter hypermethylation, which represses the expression of H19 and miR-675-5p and results in p53 protein overexpression in EBVaGC and NPC cells. These observations suggest a new mechanism of aberrant expression of p53 by LMP1, which facilitates EBV latency.

EBV down-regulates COX-2 expression via TRAF2 and ERK signal pathway in EBV-associated gastric cancer

Epstein-Barr virus-associated gastric cancer (EBVaGC) accounts for nearly 10% of gastric cancer. Cyclooxygenase-2 (COX-2) plays a crucial role in cancer progression. However, there is no experimental study on the regulation mechanism of EBV on COX-2 in EBVaGC. To understand more about the tumorigenic mechanism of EBVaGC, the study investigated the role of EBV encode latent membrane protein LMP1 and LMP2A in the regulation of COX-2. The expression of COX-2 was examined in EBVaGC and EBV negative gastric cancer (EBVnGC) cell lines. The plasmids were transfected in SGC7901 to overexpress LMP1/2A. Small interfering RNA (si-RNA) targeting LMP1/2A in GT38 and targeting TRAF2 in SGC7901 were used to detect the expression of COX-2. Furthermore, si-ERK1/2 and the MEK inhibitor PD0325901 were used to investigate whether p-ERK participate in the regulation of COX-2 in SGC7901. The overexpression of LMP1 or LMP2A in SGC7901 down-regulates both COX-2 and TRAF2 expression, and knockdown of LMP1 or LMP2A in GT38 resulted in a certain recovery of COX-2 and TRAF2 expression. Moreover, si-TRAF2 indicated that a sharp down-regulation of COX-2. And the decrease of p-ERK also mediates the inhibitory effect of LMP1 on COX-2. In summary, overexpression of LMP1 and LMP2A inhibits COX-2, which is mediated by a decrease of TRAF2, and p-ERK is involved in the inhibition of COX-2 by LMP1 in gastric cancer.

The EBV-Encoded Oncoprotein, LMP1, Induces an Epithelial-to-Mesenchymal Transition (EMT) via Its CTAR1 Domain through Integrin-Mediated ERK-MAPK Signalling

The Epstein–Barr virus (EBV)-encoded latent membrane protein 1 (LMP1) oncogene can induce profound effects on epithelial growth and differentiation including many of the features of the epithelial-to-mesenchymal transition (EMT). To better characterise these effects, we used the well-defined Madin Darby Canine Kidney (MDCK) epithelial cell model and found that LMP1 expression in these cells induces EMT as defined by characteristic morphological changes accompanied by loss of E-cadherin, desmosomal cadherin and tight junction protein expression. The induction of the EMT phenotype required a functional CTAR1 domain of LMP1 and studies using pharmacological inhibitors revealed contributions from signalling pathways commonly induced by integrin–ligand interactions: extracellular signal-regulated kinases/mitogen-activated protein kinases (ERK-MAPK), PI3-Kinase and tyrosine kinases, but not transforming growth factor beta (TGFβ). More detailed analysis implicated the CTAR1-mediated induction of Slug and Twist in LMP1-induced EMT. A key role for β1 integrin signalling in LMP1-mediated ERK-MAPK and focal adhesion kianse (FAK) phosphorylation was observed, and β1 integrin activation was found to enhance LMP1-induced cell viability and survival. These findings support an important role for LMP1 in disease pathogenesis through transcriptional reprogramming that enhances tumour cell survival and leads to a more invasive, metastatic phenotype.

Progression of understanding for the role of Epstein-Barr virus and management of nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is very common in southern China and Southeast Asia. In regions where NPC is endemic, undifferentiated subtypes constitute most cases and are invariably associated with Epstein-Barr virus (EBV) infection, whereas the differentiated subtype is more common in other parts of the world. Undifferentiated NPC is a unique malignancy with regard to its epidemiology, etiology, and clinical presentation. Clinically, NPC is highly invasive and metastatic, but sensitive to both chemotherapy and radiotherapy (RT). Overall prognosis has dramatically improved over the past three decades because of advances in management, including the improvement of RT technology, the broader application of chemotherapy, and more accurate disease staging. Despite the excellent local control with modern RT, distant failure remains a challenging problem. Advances in molecular technology have helped to elucidate the molecular pathogenesis of NPC. This article reviews the contribution of EBV gene products to NPC pathogenesis and the current management of NPC.

Reversion-inducing cysteine-rich protein with Kazal motifs and its regulation by glycogen synthase kinase 3 signaling in oral cancer

The reversion-inducing cysteine-rich protein with Kazal motifs (RECK) and glycogen synthase kinase (GSK3) are novel tumor suppressors, and emerging evidence has suggested their active role in oral cancer pathogenesis. In the present study, 112 human samples, including 55 fresh samples of 14 adjacent normal tissues, 25 noninvasive oral tumors, and 18 invasive tumors, were included. The messenger RNA (mRNA) expression, protein expression, and promoter methylation of the RECK gene, as well as the expression of GSK3β, phospho/total β-catenin, and c-myc, were measured by RT-PCR, bisulphate modification-PCR, immunohistochemistry, and Western blot analysis. Additionally, ectopic expression of in/active GSK3β was performed in cell culture experiments. This study provided information on the progressive silencing of RECK gene expression at the protein and mRNA levels paralleled with promoter hypermethylation at various stages of oral tumor invasion. RECK expression and the hypermethylation of the RECK gene promoter were negatively and positively correlated with pS⁹GSK3β/c-myc expression, respectively. Further, a negative trend of RECK protein expression with nuclear β-catenin expression was observed. Induced expression of active GSK3β reversed the RECK silencing in SCC9 cells. Collectively, our results demonstrated that the silencing of the RECK gene, possibly regulated by the GSK3β pathway, is an important event in oral cancer invasion and this pathway could be exploited for therapeutic interventions.

Epstein-Barr Virus Oncoprotein LMP1 Mediates Epigenetic Changes in Host Gene Expression through PARP1

The latent infection of Epstein-Barr virus (EBV) is associated with 1% of human cancer incidence. Poly(ADP-ribosyl)ation (PARylation) is a posttranslational modification catalyzed by poly(ADP-ribose) polymerases (PARPs) that mediate EBV replication during latency. In this study, we detail the mechanisms that drive cellular PARylation during latent EBV infection and the effects of PARylation on host gene expression and cellular function. EBV-infected B cells had higher PAR levels than EBV-negative B cells. Moreover, cellular PAR levels were up to 2-fold greater in type III than type I latently infected EBV B cells. We identified a positive association between expression of the EBV genome-encoded latency membrane protein 1 (LMP1) and PAR levels that was dependent upon PARP1. PARP1 regulates gene expression by numerous mechanisms, including modifying chromatin structure and altering the function of chromatin-modifying enzymes. Since LMP1 is essential in establishing EBV latency and promoting tumorigenesis, we explored the model that disruption in cellular PARylation, driven by LMP1 expression, subsequently promotes epigenetic alterations to elicit changes in host gene expression. PARP1 inhibition resulted in the accumulation of the repressive histone mark H3K27me3 at a subset of LMP1-regulated genes. Inhibition of PARP1, or abrogation of PARP1 expression, also suppressed the expression of LMP1-activated genes and LMP1-mediated cellular transformation, demonstrating an essential role for PARP1 activity in LMP1-induced gene expression and cellular transformation associated with LMP1. In summary, we identified a novel mechanism by which LMP1 drives expression of host tumor-promoting genes by blocking generation of the inhibitory histone modification H3K27me3 through PARP1 activation.

IMPORTANCE

EBV is causally linked to several malignancies and is responsible for 1% of cancer incidence worldwide. The EBV-encoded protein LMP1 is essential for promoting viral tumorigenesis by aberrant activation of several well-known intracellular signaling pathways. We have identified and defined an additional novel molecular mechanism by which LMP1 regulates the expression of tumor-promoting host genes. We found that LMP1 activates the cellular protein PARP1, leading to a decrease in a repressive histone modification, accompanied by induction in expression of multiple cancer-related genes. PARP1 inhibition or depletion led to a decrease in LMP1-induced cellular transformation. Therefore, targeting PARP1 activity may be an effective treatment for EBV-associated malignancies.

MicroRNA-135b, a HSF1 target, promotes tumor invasion and metastasis by regulating RECK and EVI5 in hepatocellular carcinoma

MicroRNAs (miRNAs) often localize to chromosomal fragile sites and are associated with cancer. In this study, we screened for the aberrant and functional miRNAs in the regions of copy number alterations (CNAs) in hepatocellular carcinoma (HCC), and found that miR-135b was frequently amplified and upregulated in HCC tissues. The expression level of miR-135b was inversely correlated with the occurrence of tumor capsules. In addition, miR-135b promoted HCC cell migration and invasion in vitro and metastasis in vivo. The reversion-inducing-cysteine-rich protein with kazal motifs (RECK) and ecotropic viral integration site 5 (EVI5) were identified as the direct and functional targets of miR-135b in HCC. Furthermore, we observed that heat shock transcription factor 1 (HSF1) directly activated miR-135b expression, consequently enhancing HCC cell motility and invasiveness. The newly identified HSF1/miR-135b/RECK&EVI5 axis provides novel insight into the mechanisms of HCC metastasis, which may facilitate the development of new therapeutics against HCC.

The Latent Membrane Protein 1 (LMP1)

Almost exactly twenty years after the discovery of Epstein-Barr virus (EBV), the latent membrane protein 1 (LMP1) entered the EBV stage, and soon thereafter, it was recognized as the primary transforming gene product of the virus. LMP1 is expressed in most EBV-associated lymphoproliferative diseases and malignancies, and it critically contributes to pathogenesis and disease phenotypes. Thirty years of LMP1 research revealed its high potential as a deregulator of cellular signal transduction pathways leading to target cell proliferation and the simultaneous subversion of cell death programs. However, LMP1 has multiple roles beyond cell transformation and immortalization, ranging from cytokine and chemokine induction, immune modulation, the global alteration of gene and microRNA expression patterns to the regulation of tumor angiogenesis, cell-cell contact, cell migration, and invasive growth of tumor cells. By acting like a constitutively active receptor, LMP1 recruits cellular signaling molecules associated with tumor necrosis factor receptors such as tumor necrosis factor receptor-associated factor (TRAF) proteins and TRADD to mimic signals of the costimulatory CD40 receptor in the EBV-infected B lymphocyte. LMP1 activates NF-κB, mitogen-activated protein kinase (MAPK), phosphatidylinositol 3-kinase (PI3-K), IRF7, and STAT pathways. Here, we review LMP1's molecular and biological functions, highlighting the interface between LMP1 and the cellular signal transduction network as an important factor of virus-host interaction and a potential therapeutic target.

TMPRSS4 facilitates epithelial-mesenchymal transition of hepatocellular carcinoma and is a predictive marker for poor prognosis of patients after curative resection

TMPRSS4 (Transmembrane protease serine 4) is up-regulated in a broad spectrum of cancers. However, little is known about the biological effects of TMPRSS4 on hepatocellular carcinoma (HCC) and the related mechanisms. In the present study, we found that overexpression of TMPRSS4 significantly promoted the invasion, migration, adhesion and metastasis of HCC. Further more, TMPRSS4 induced EMT of HCC, which was mediated via snail and slug as a result of Raf/MEK/ERK1/2 activation, and inhibition of ERK1/2 activation by its inhibitor was associated with reduced cell invasion and reversion of EMT. In addition, we demonstrated that TMPRSS4 remarkably suppressed the expression of RECK, an inhibitor of angiogenesis, and drastically induced tumor angiogenesis and growth. More important, in clinical HCC specimens, TMPRSS4 expression was significantly correlated with tumor staging and was inversely correlated with E-cadherin and RECKS expression. Expression of TMPRSS4 is significantly associated with HCC progression and is an independent prognostic factor for postoperative worse survival and recurrence. In conclusion, TMPRSS4 functions as a positive regulator of Raf/MEK/ERK1/2 pathway and promotes HCC progression by inducing EMT and angiogenesis. The increase of TMPRSS4 expression may be a key event for HCC progression and may be regarded as a potential prognostic marker for HCC.

Prognostic Value of Molecular Markers and Implication for Molecular Targeted Therapies in Nasopharyngeal Carcinoma: An Update in an Era of New Targeted Molecules Development

The aim of the study was to evaluate the prognostic significance of molecular biomarkers which could provide information for more accurate prognostication and development of novel therapeutic strategies for nasopharyngeal carcinoma (NPC). NPC is a unique malignant epithelial carcinoma of head and neck region, with an intimate association with the Epstein-Barr virus (EBV). Currently, the prediction of NPC prognosis is mainly based on the clinical TNM staging; however, NPC patients with the same clinical stage often present different clinical outcomes, suggesting that the TNM stage is insufficient to precisely predict the prognosis of this disease. In this review, we give an overview of the prognostic value of molecular markers in NPC and discuss potential strategies of targeted therapies for treatment of NPC. Molecular biomarkers, which play roles in abnormal proliferation signaling pathways (such as Wnt/β-catenin pathway), intracellular mitogenic signal aberration (such as hypoxia-inducible factor (HIF)-1α), receptor-mediated aberrations (such as vascular endothelial growth factor (VEGF)), tumor suppressors (such as p16 and p27 activity), cell cycle aberrations (such as cyclin D1 and cyclin E), cell adhesion aberrations (such as E-cadherin), apoptosis dysregualtion (such as survivin) and centromere aberration (centromere protein H), are prognostic markers for NPC. Plasma EBV DNA concentrations and EBV-encoded latent membrane proteins are also prognostic markers for NPC. Implication of molecular targeted therapies in NPC was discussed. Such therapies could have potential in combination with different cytotoxic agents to combat and eradicate tumor cells. In order to further improve overall survival for patients with loco-regionally advanced NPC, the development of innovative strategies, including prognostic molecular markers and molecular targeted agents is needed.

STAT3 upregulates miR-92a to inhibit RECK expression and to promote invasiveness of lung cancer cells

Background:

Signal transducer and activator of transcription 3 (STAT3) activation is frequently found in human lung cancer and is associated with increased metastasis and reduced survival. How STAT3 enhances invasiveness is unclear.

Methods:

The expression of microRNAs and target genes was measured by real-time RT–PCR. Protein level was studied by western blotting. Luciferase reporter assay was used to confirm the direct targeting of microRNAs. Gelatin zymography was used to study matrix metalloproteinase (MMP) activity. Transwell assay was used to investigate cell migration and invasion.

Results:

Enforced expression of STAT3 decreases the endogenous MMP inhibitor RECK protein but not mRNA level in H460 cells. Conversely, STAT3 inhibitor S3I-201 increases RECK protein in STAT3-activating H1299 cells. We demonstrate that STAT3 upregulates miR-92a to repress RECK via post-transcriptional inhibition. The RECK 3′-untranslated region (3′UTR) reporter activity assay suggests that RECK is a direct repression target of miR-92a. Delivery of pre-miR-92a reduces RECK protein level whereas transfection of anti-miR-92a restores STAT3-induced downregulation of RECK. Anti-miR-92a attenuates MMP activity, migration and invasion of H1299 cells and STAT3-overexpressing H460 cells, suggesting miR-92a is critical for STAT3-induced invasiveness.

Conclusion:

The STAT3-induced miR-92a promotes cancer invasion by suppressing RECK and targeting of the STAT3/miR-92a axis may be helpful for cancer treatment.

Pathogenic role of Epstein-Barr virus latent membrane protein-1 in the development of nasopharyngeal carcinoma

Undifferentiated nasopharyngeal carcinoma (NPC) is an Epstein-Barr virus-associated malignant tumor. A consistent elevation in EBV antibody titers is a well-established risk factor for the development of NPC. The pathophysiological relationship and molecular mechanisms of EBV-mediated carcinogenesis have not been fully elucidated. While NPC tumors are known to express three EBV-encoded proteins, EBNA1, LMP1, and LMP2, they also express a large number of virus-encoded small RNAs (EBERs) and microRNAs (miRNAs). Among them, LMP1 may be a central player in the development of NPC. LMP1, an EBV-encoded primary oncogene, functions as a viral mimic of the TNFR family member, CD40, and engages in a number of signaling pathways that induce morphological and phenotypic alterations in epithelial cells. LMP1 upregulates EMT, and contributes to the highly metastatic features of NPC. Moreover, LMP1-associated EMT is accompanied by the expression of cancer stem cell (CSC)/cancer progenitor cell (CPC) markers (CD44high/CD24low) and the acquisition of stem cell/progenitor cell-like properties. BART miRNAs, encoded from the BamHI-A region of the viral genome, are the most abundant transcripts. They modulate apoptosis and host innate immune defense mechanisms. Some BART1 miRNAs are considered to negatively regulate LMP1 protein expression. LMP1 is secreted via exosomes, is incorporated into EBV-uninfected cells by endocytosis, and affects the environment surrounding the tumor. Here we reviewed the contribution of EBV gene products to NPC pathogenesis in relation with LMP1.

Up-regulation of miR-182 by β-catenin in breast cancer increases tumorigenicity and invasiveness by targeting the matrix metalloproteinase inhibitor RECK

BACKGROUND

MiR-182 is a member of the miR-183 cluster located at human chromosome 7q32 region and is up-regulated in human cancers. We study the regulation of miR-182 expression and its oncogenic role.

METHODS

MiR-182 level was investigated by real-time reverse transcription-PCR. Chromatin immunoprecipitation assay was used to confirm promoter binding of transcription factors. The correlation between miR-182 and RECK was analyzed by Western blotting, real-time RT-PCR and 3(')-untranslated region reporter assay. Zymography, matrix metalloproteinase activity, invasion and colony formation were used to study the tumorigenic activity.

RESULTS

MiR-182 is over-expressed in human breast tumor tissues and cell lines. Inhibition or knockdown of β-catenin reduced miR-182 level in MDA-MB-231 cells. ChIP assay confirmed the binding of β-catenin on miR-182 promoter. Anti-miR-182 increased the MMP inhibitor RECK protein in MDA-MB-231 cells while pre-miR-182 reduced RECK protein but not mRNA in normal mammary epithelial H184B5F5/M10 cells. Restoration of RECK protein by anti-miR-182 attenuated MMP-9 activity, cell invasion and colony formation. Ectopic expression of miR-182 inhibited restoration of RECK protein by β-catenin inhibitor indicating miR-182 is important for β-catenin-induced down-regulation of RECK. An inverse association between miR-182 and RECK was demonstrated in breast tumor tissues.

CONCLUSIONS

We provide evidence that miR-182 is up-regulated by β-catenin signaling pathway in breast cancer and its up-regulation increases tumorigenicity and invasiveness by repressing RECK.

GENERAL SIGNIFICANCE

Our data demonstrate for the first time that miR-182 expression is controlled by β-catenin. In addition, we identify a new miR-182 target RECK which is important for miR-182-induced tumorigenesis.

Aberrant expression levels of MTA1 and RECK in nasopharyngeal carcinoma: association with metastasis, recurrence, and prognosis

OBJECTIVES

We investigated the expression and clinical value of MTA1 and RECK genes in patients with nasopharyngeal carcinoma (NPC).

METHODS

We examined MTA1 and RECK expression in nasopharyngeal tissue from patients with chronic nasopharyngitis, lymph nodes with metastasis of NPC, and primary NPC tumor tissue by means of in situ hybridization and analyzed their correlation with the clinicopathologic features of NPC.

RESULTS

The positive expression of MTA1 in the NPC tissues and metastatic lymph nodes was significantly higher than that in the chronic nasopharyngitis tissues (p < 0.05). The positive expression of RECK in the NPC tissues and metastatic lymph nodes was significantly lower than that in the chronic nasopharyngitis tissues (p < 0.05). The RECK expression level was inversely correlated with the MTA1 expression level in the NPC tissues (p < 0.05). The increased MTA1 and decreased RECK expressions in the NPC tissues had no association with gender, age, T-stage, or clinical stage (p > 0.05). However, they had a positive correlation with cervical lymph node metastasis, tumor recurrence, and 5-year overall survival rate of the patients with NPC (p < 0.05). Moreover, multivariate analysis showed that MTA1 and RECK expressions were independent prognostic factors for survival (p < 0.05).

CONCLUSIONS

The conversely abnormal expression levels of MTA1 and RECK may be collectively involved in progression of malignancies and may serve as molecular predictors for metastasis, recurrence, and prognosis of NPC.

HPV16 oncoproteins induce MMPs/RECK-TIMP-2 imbalance in primary keratinocytes: possible implications in cervical carcinogenesis

Cervical cancer is the third most common cancer in women worldwide. Persistent infection with high-risk HPV types, principally HPV16 and 18 is the main risk factor for the development of this malignancy. However, the onset of invasive tumor occurs many years after initial exposure in a minority of infected women. This suggests that other factors beyond viral infection are necessary for tumor establishment and progression. Tumor progression is characterized by an increase in secretion and activation of matrix metalloproteinases (MMPs) produced by either the tumor cells themselves or tumor-associated fibroblasts or macrophages. Increased MMPs expression, including MMP-2, MMP-9 and MT1-MMP, has been observed during cervical carcinoma progression. These proteins have been associated with degradation of ECM components, tumor invasion, metastasis and recurrence. However, few studies have evaluated the interplay between HPV infection and the expression and activity of MMPs and their regulators in cervical cancer. We analyzed the effect of HPV16 oncoproteins on the expression and activity of MMP-2, MMP-9, MT1-MMP, and their inhibitors TIMP-2 and RECK in cultures of human keratinocytes. We observed that E7 expression is associated with increased pro-MMP-9 activity in the epithelial component of organotypic cultures, while E6 and E7 oncoproteins co-expression down-regulates RECK and TIMP-2 levels in organotypic and monolayers cultures. Finally, a study conducted in human cervical tissues showed a decrease in RECK expression levels in precancer and cancer lesions. Our results indicate that HPV oncoproteins promote MMPs/RECK-TIMP-2 imbalance which may be involved in HPV-associated lesions outcome.

The metalloproteinase inhibitor Reck is essential for zebrafish DRG development

The neural crest is a migratory, multipotent cell lineage that contributes to myriad tissues, including sensory neurons and glia of the dorsal root ganglia (DRG). To identify genes affecting cell fate specification in neural crest, we performed a forward genetic screen for mutations causing DRG deficiencies in zebrafish. This screen yielded a mutant lacking all DRG, which we named sensory deprived (sdp). We identified a total of four alleles of sdp, all of which possess lesions in the gene coding for reversion-inducing cysteine-rich protein containing Kazal motifs (Reck). Reck is an inhibitor of metalloproteinases previously shown to regulate cell motility. We found reck function to be both necessary for DRG formation and sufficient to rescue the sdp phenotype. reck is expressed in neural crest cells and is required in a cell-autonomous fashion for appropriate sensory neuron formation. In the absence of reck function, sensory neuron precursors fail to migrate to the position of the DRG, suggesting that this molecule is crucial for proper migration and differentiation.

The role of the EBV-encoded latent membrane proteins LMP1 and LMP2 in the pathogenesis of nasopharyngeal carcinoma (NPC)

Although frequently expressed in EBV-positive malignancies, the contribution of the oncogenic latent membrane proteins, LMP1 and LMP2, to the pathogenesis of nasopharyngeal carcinoma (NPC) is not fully defined. As a key effector in EBV-driven B cell transformation and an established "transforming" gene, LMP1 displays oncogenic properties in rodent fibroblasts and induces profound morphological and phenotypic effects in epithelial cells. LMP1 functions as a viral mimic of the TNFR family member, CD40, engaging a number of signalling pathways that induce morphological and phenotypic alterations in epithelial cells. Although LMP2A plays an essential role in maintaining viral latency in EBV infected B cells, its role in epithelial cells is less clear. Unlike LMP1, LMP2A does not display "classical" transforming functions in rodent fibroblasts but its ability to engage a number of potentially oncogenic cell signalling pathways suggests that LMP2A can also participate in EBV-induced epithelial cell growth transformation. Here we review the effects of LMP1 and LMP2 on various aspects of epithelial cell behaviour highlighting key aspects that may contribute to the pathogenesis of NPC.

Epstein - Barr virus Latent Membrane Protein 1 suppresses reporter activity through modulation of promyelocytic leukemia protein-nuclear bodies

The Epstein-Barr virus (EBV) encoded Latent Membrane Protein 1 (LMP1) has been shown to increase the expression of promyelocytic leukemia protein (PML) and the immunofluorescent intensity of promyelocytic leukemia nuclear bodies (PML NBs). PML NBs have been implicated in the modulation of transcription and the association of reporter plasmids with PML NBs has been implicated in repression of reporter activity. Additionally, repression of various reporters in the presence of LMP1 has been noted. This study demonstrates that LMP1 suppresses expression of reporter activity in a dose responsive manner and corresponds with the LMP1 induced increase in PML NB intensity. Disruption of PML NBs with arsenic trioxide or a PML siRNA restores reporter activity. These data offer an explanation for previously conflicting data on LMP1 signaling and calls attention to the possibility of false-positives and false-negatives when using reporter assays as a research tool in cells expressing LMP1.

The Epstein-Barr Virus BART microRNAs target the pro-apoptotic protein Bim

In Epstein-Barr Virus infected epithelial cancers, the alternatively spliced BamHI A rightward transcripts (BARTs) are abundantly expressed and are the template for two large clusters of miRNAs. This study indicates that both of these clusters independently can inhibit apoptosis in response to etoposide in an epithelial cell line. The Bcl-2 interacting mediator of cell death (Bim) was identified using gene expression microarrays and bioinformatic analysis indicated multiple potential binding sites for several BART miRNAs in the Bim 3'UTR. Bim protein was reduced by Cluster I and the individual expression of several miRNAs, while mRNA levels were unaffected. In reporter assays, the Bim 3' untranslated region (UTR) was inhibited by both clusters but not by any individual miRNAs. These results are consistent with the BART miRNAs downregulating Bim post-transcriptionally in part through the 3'UTR and suggest that there are miRNA recognition sites within other areas of the Bim mRNA.

The tumor suppressor RECK interferes with HER-2/Neu dimerization and attenuates its oncogenic signaling

Our previous study demonstrates that HER-2/Neu oncogene inhibits a matrix metalloproteinase inhibitor and tumor metastasis suppressor RECK to promote metastasis. Conversely, the effect of RECK on the oncogenic function of HER-2/Neu is unknown. Ectopic expression of RECK in 293T cells and HER-2/Neu-overexpressing breast cancer cells shows that RECK and HER-2/Neu are co-localized and these two proteins can be co-immunoprecipitated. RECK inhibits HER-2/Neu receptor dimerization and autophosphorylation, which causes reduction of ERK and AKT kinase activity and down-regulation of HER-2/Neu target genes. RECK expression is reduced in 58.8% of breast cancer tissues and is associated with lymph node invasion supporting its anti-metastatic role. Collectively, we provide the first evidence that RECK can negatively regulate oncogenic activity of HER-2/Neu by inhibiting receptor dimerization.

Decreased expression of updated NESG1 in nasopharyngeal carcinoma: its potential role and preliminarily functional mechanism

Human NESG1 (CCDC19) gene was originally isolated in our laboratory from human nasopharynx tissue. However, the biological and clinical significances of this gene remain largely unknown. In this report, two errors in the originally submitted sequence of human NESG1 gene were found, and the open reading frame sequence of NESG1 (Accession number: NM_012337.1) was revised and updated in the NCBI database (Accession number: NM_012337.2). The antibody raised against the revised sequence of NESG1 detected a single band of 66 kD in human nasopharynx tissues. NESG1 transcripts were specifically expressed in the nasopharynx epithelium. Expression of NESG1 transcripts and protein was downregulated or absent in nasopharyngeal carcinoma (NPC) tissues and cell lines in comparison to that in the normal nasopharynx tissues. The levels of NESG1 protein were significantly greater in the low-grade NPC tissues than that in the high-grade NPC tissues. Induced expression of NESG1 in otherwise NESG1-negative 5-8F cells not only significantly decreased cell proliferation, G1-S phase transition, but also markedly inhibited the ability of cell migration and invasion as well as in vivo tumorigenesis. Furthermore, NESG1 also significantly regulated the expression of cell cycle regulator CCNA1 and p21. Our findings first provided evidence that NESG1 may act as a tumor suppressor by inhibiting cell proliferation, invasion and migration of NPC cells.

Reversion-inducing cysteine-rich protein with Kazal motifs interferes with epidermal growth factor receptor signaling

The reversion-inducing cysteine-rich protein with Kazal motifs (RECK) gene had been isolated as an antagonist to RAS signaling; however, the mechanism of its action is not clear. In this study, the effect of loss of RECK function was assessed in various ways and cell systems. Successive cell cultivation of mouse embryonic fibroblasts (MEFs) according to 3T3 protocol revealed that the germline knockout of RECK confers accelerated cell proliferation and early escape from cellular senescence associated with downregulation of p19(Arf), Trp53 and p21(Cdkn1a). In contrast, short hairpin RNA-mediated depletion of RECK induced irreversible growth arrest along with several features of the Arf, Trp53 and Cdkn1a-dependent cellular senescence. Within 2 days of RECK depletion, we observed a transient increase in protein kinase B (AKT) and extracellular signal-regulated kinase (ERK) phosphorylation associated with an upregulated expression of cyclin D1, p19(Arf), Trp53, p21(Cdkn1a) and Sprouty 2. On further cultivation, RAS, AKT and ERK activities were then downregulated to a level lower than control, indicating that RECK depletion leads to a negative feedback to RAS signaling and subsequent cellular senescence. In addition, we observed that epidermal growth factor receptor (EGFR) activity was transiently upregulated by RECK depletion in MEFs, and continuously downregulated by RECK overexpression in colon cancer cells. These findings indicate that RECK is a novel modulator of EGFR signaling.

The Epstein-Barr virus latent membrane protein 1 and transforming growth factor--β1 synergistically induce epithelial--mesenchymal transition in lung epithelial cells

The histopathology of idiopathic pulmonary fibrosis (IPF) includes the presence of myofibroblasts within so-called fibroblastic foci, and studies suggest that lung myofibroblasts may be derived from epithelial cells through epithelial--mesenchymal transition (EMT). Transforming growth factor (TGF)-β1 is expressed and/or activated in fibrogenesis, and induces EMT in lung epithelial cells in a dose-dependent manner. A higher occurrence of Epstein-Barr virus (EBV) has been reported in the lung tissue of patients with IPF. EBV expresses latent membrane protein (LMP) 1 during the latent phase of infection, and may play a role in the pathogenesis of pulmonary fibrosis inasmuch as LMP-1 may act as a constitutively active TNF-α receptor. Our data show a remarkable increase in mesenchymal cell markers, along with a concurrent reduction in the expression of epithelial cell markers in lung epithelial cells cotreated with LMP-1, and very low doses of TGF-β1. This effect was mirrored in lung epithelial cells infected with EBV expressing LMP1 and cotreated with TGF-β1. LMP1 pro-EMT signaling was identified, and occurs primarily through the nuclear factor-κB pathway and secondarily through the extracellular signal--regulated kinase (ERK) pathway. Activation of the ERK pathway was shown to be critical for aspects of TGF-β1-induced EMT. LMP1 accentuates the TGF-β1 activation of ERK. Together, these data demonstrate that the presence of EBV-LMP1 in lung epithelial cells synergizes with TGF-β1 to induce EMT. Our in vitro data may help to explain the observation that patients with IPF demonstrating positive staining for LMP1 in lung epithelial cells have a more rapid demise than patients in whom LMP1 is not detected.

Over-expression of eukaryotic translation initiation factor 4 gamma 1 correlates with tumor progression and poor prognosis in nasopharyngeal carcinoma

BACKGROUND

The aim of the present study was to analyze the expression of eukaryotic translation initiation factor 4 gamma 1 (EIF4G1) in nasopharyngeal carcinoma (NPC) and its correlation with clinicopathologic features, including patients' survival time.

METHODS

Using real-time PCR, we detected the expression of EIF4G1 in normal nasopharyngeal tissues, immortalized nasopharyngeal epithelial cell lines NP69, NPC tissues and cell lines. EIF4G1 protein expression in NPC tissues was examined using immunohistochemistry. Survival analysis was performed using Kaplan-Meier method. The effect of EIF4G1 on cell invasion and tumorigenesis were investigated.

RESULTS

The expression levels of EIF4G1 mRNA were significantly greater in NPC tissues and cell lines than those in the normal nasopharyngeal tissues and NP69 cells (P < 0.001). Immunohistochemical analysis revealed that the expression of EIF4G1 protein was higher in NPC tissues than that in the nasopharyngeal tissues (P < 0.001). In addition, the levels of EIF4G1 protein in tumors were positively correlated with tumor T classification (P = 0.039), lymph node involvement (N classification, P = 0.008), and the clinical stages (P = 0.003) of NPC patients. Patients with higher EIF4G1 expression had shorter overall survival time (P = 0.019). Multivariate analysis showed that EIF4G1 expression was an independent prognostic indicator for the overall survival of NPC patients. Using shRNA to knock down the expression of EIF4G1 not only markedly inhibited cell cycle progression, proliferation, migration, invasion, and colony formation, but also dramatically suppressed in vivo xenograft tumor growth.

CONCLUSION

Our data suggest that EIF4G1 can serve as a biomarker for the prognosis of NPC patients.

RECK is up-regulated and involved in chondrocyte cloning in human osteoarthritic cartilage

Reversion-inducing cysteine-rich protein with Kazal motifs (RECK) is a membrane-anchored matrix metalloproteinase regulator, but its functions in cartilage are not fully understood. The aim of the present study was to examine the expression and functions of RECK in human osteoarthritic (OA) cartilage. Quantitative RT-PCR indicated that the expression level of RECK is significantly higher in OA cartilage than in normal cartilage. By immunohistochemical analysis, RECK was localized to chondrocytes in OA cartilage, and the immunoreactivity directly correlated with the Mankin score and degree of chondrocyte cloning and proliferation. In cultured OA chondrocytes, RECK was expressed on the cell surface by glycosylphosphatidylinositol anchoring. The expression was stimulated by insulin-like growth factor-1 and suppressed by interleukin-1 and tumor necrosis factor-alpha. Down-regulation of RECK by small interfering RNA showed reduced spreading and smaller focal adhesions in the chondrocytes. Chondrocyte migration in a monolayer wounding assay was increased by down-regulation of RECK and inhibited by RECK overexpression in an matrix metalloproteinase activity-dependent manner. On the other hand, chondrocyte proliferation was suppressed by RECK silencing, and this was associated with reduced phosphorylation of focal adhesion kinase and extracellular signal-regulated kinase, whereas the proliferation was enhanced by RECK overexpression. These data are the first to demonstrate that RECK is up-regulated in human OA cartilage and suggest that RECK plays a role in chondrocyte cloning probably through suppression and promotion of chondrocyte migration and proliferation, respectively.

Role of the Epstein-Barr virus-encoded latent membrane protein-1, LMP1, in the pathogenesis of nasopharyngeal carcinoma

Although frequently expressed in Epstein-Barr virus (EBV)-positive malignancies, the contribution of the oncogenic latent membrane protein-1 (LMP1) to the pathogenesis of nasopharyngeal carcinoma remains to be fully defined. As a key effector in EBV-driven B-cell transformation in vitro, LMP1 also displays oncogenic properties in rodent fibroblasts, and exhibits similar effects in epithelial cells. LMP1 functions as a viral mimic of the TNFR family member, CD40, engaging a plethora of signaling pathways including: NF-kappaB, JNK/p38 (SAPK), PI3-kinase and ERK-MPK. The constitutive activation of these pathways appears central in the ability of LMP1 to induce multiple morphological and phenotypic alterations. Here we review the effects of LMP1 on epithelial cell growth transformation, and its putative role in the pathogenesis of nasopharyngeal carcinoma, focusing on key areas of proliferation, survival, cell motility and invasion.

Profiling and comparing transcription factors activated in non-metastatic and metastatic nasopharyngeal carcinoma cells

Transcription factors (TFs) are modulators of gene expression that are critically important in the establishment and progression of human cancers. In the current study, the activity profiles of TFs in a normal nasopharyngeal epithelial cell line and in nasopharyngeal carcinoma (NPC) cell lines were studied using oligonucleotide array-based TF assays. Compared to the normal epithelial cell line NP69, nine TFs in the non-metastatic NPC cell line (6-10B) and eight TFs in a metastatic NPC cell line (5-8F) were upregulated. Among upregulated TFs, Sp1, AP2, and ATF/CREB families exhibited relatively high activities in NPC cell lines. Transcription levels of Sp1, ATF-1, ATF-2, AP2alpha, AP2gamma, and CREB1 were higher in 5-8F cells than in 6-10B cells. In addition, higher expression of the Sp1 target genes MMP-9 and VEGF was observed in 5-8F cells. Sp1 silencing reduced VEGF and MMP-9 expression. Inhibition of Sp1 expression and activity in 5-8F cells by mithramycin resulted in downregulated expression and secretion of MMP-9 and VEGF, concomitant with inhibition of cell migration and invasion. These results suggest that dynamic changes in TF activities occur in NPC cells and that these changes may play important roles in regulating the expression of genes associated with the development and progression of NPC.

RECK negatively regulates matrix metalloproteinase-9 transcription

RECK, a glycosylphosphatidylinositol-anchored glycoprotein, inhibits the enzymatic activities of some matrix metalloproteinases (MMP), thereby suppressing tumor cell metastasis; however, the detailed mechanism is still obscure. In this study, we compared the gene expression profiles between mock- and RECK-transfected HT1080 cells and showed that RECK decreases MMP-9 mRNA levels but not other MMP mRNA levels. Moreover, treatment with RECK-specific siRNA increased MMP-9 mRNA in RECK-expressing cells. The promoter assay showed that MMP-9 promoter activity was suppressed by RECK and that RECK-mediated suppression of MMP-9 promoter activity requires 12-O-tetradecanoylphorbol-13-acetate-responsive element (TRE) and kappaB sites. Moreover, the binding ability of Fra-1 and c-Jun to TRE within the MMP-9 promoter region was suppressed by RECK. Thus, these results show that RECK is a negative regulator of MMP-9 transcription.

Tumor-derived variants of Epstein-Barr virus latent membrane protein 1 induce sustained Erk activation and c-Fos

Latent membrane protein 1 (LMP1) of Epstein-Barr virus (EBV) is a proven oncogene that is essential for transformation of human B cells by the virus. LMP1 induces constitutive activation of several signal transduction pathways involving nuclear factor kappaB, phosphatidylinositol 3-kinase/Akt, and the mitogen-activated protein kinases (MAPK) p38, c-Jun N-terminal kinase (JNK), and extracellular signal-regulated kinase (Erk). Sequencing of LMP1 isolated from a panel of EBV+ B cell lymphomas identified three different variants of LMP1, each distinct from the B95.8 prototype isoform. All tumor variants of LMP1 as well as the B95.8 LMP1 isoform were able to induce rapid p38 phosphorylation as well as Akt and JNK activation. Additionally all variants showed similar ability to activate nuclear factor kappaB. In contrast, only tumor-derived LMP1 variants induced prolonged Erk activation and c-Fos expression. Sequence analysis revealed only two amino acids, 212 and 366, shared by the tumor variants but distinct from B95.8. Point mutation of either amino acids 212 (glycine to serine) or 366 (serine to threonine) from the B95.8 isoform to the tumor variant version of LMP1 was sufficient for gain of function characterized by sustained activation of Erk and subsequent c-Fos induction and binding to the AP1 site. Our results indicate that the enhanced ability of tumor-derived LMP1 to induce and stabilize the c-Fos oncogene can be localized to two amino acids in the C terminus of LMP1.

Latent membrane protein 1 of Epstein-Barr virus activates the hTERT promoter and enhances telomerase activity in B lymphocytes

Transformation of primary B lymphocytes by Epstein-Barr virus requires the establishment of a strictly latent infection, the expression of several latent viral proteins, and sustained telomerase activity. Our previous findings indicated that induction of hTERT, the rate-limiting catalytic unit of the telomerase complex, was associated with the expression of the viral latent membrane protein 1 (LMP1). In the present study, we demonstrate that ectopic expression of LMP1 in BJAB and Ramos B cells resulted in an increase of hTERT transcripts, thus suggesting that LMP1 acts at the transcriptional level. This was confirmed by transient expression of a luciferase reporter plasmid containing the hTERT promoter cotransfected with an LMP1-expressing vector or transfected into B cells in which LMP1 expression was inducible. Consistently, silencing of LMP1 by small interfering RNA resulted in a reduction of hTERT transcripts. We also provide evidence indicating that LMP1-induced hTERT activation is independently mediated by NF-kappaB and by mitogen-activated protein kinase and extracellular signal-regulated kinase 1/2 pathways, whereas CD40, Akt, and mTOR signaling has no involvement. Moreover, our results do not support a role for c-Myc in mediating these effects on hTERT, since ectopic expression of LMP1 did not upregulate c-Myc and silencing of this oncogene or E box mutagenesis failed to inhibit LMP1-induced hTERT activation. These findings indicate that LMP1 simultaneously modulates multiple signal transduction pathways in B cells to transactivate the hTERT promoter and enhance telomerase activity, thus confirming the pleiotropic nature of this viral oncoprotein.

Influence of persistent canine distemper virus infection on expression of RECK, matrix-metalloproteinases and their inhibitors in a canine macrophage/monocytic tumour cell line (DH82)

A morbillivirus infection of tumour cells is known to exert oncolytic activity, but the mechanism of this inhibitory action has not been well defined. Matrix metalloproteinases (MMPs) are important enzymes degrading the extracellular matrix and are often upregulated in malignant neoplasms. Recent studies have demonstrated that RECK may potently suppress MMP-2 and -9 activity, thus inhibiting angiogenesis and metastasis. In this study, real time quantitative polymerase chain reaction (RT-qPCR) was used to determine the effect of persistent infection with canine distemper virus (CDV) infection on the expression of MMPs and their inhibitors (TIMPS) in a canine macrophage/monocytic tumour cell line (DH82). The activity of proMMP-2 and proMMP-9 was also verified zymographically. Following CDV infection, MMP-2, TIMP-1 and TIMP-2 were down-regulated, while RECK was upregulated. These findings suggest that CDV infection restores RECK expression in tumour cells and may interfere with the intracellular processing of MMPs and TIMPs, thus possibly influencing tumour cell behaviour beneficially for the host. However, this needs to be verified in in vivo studies.

Nasopharyngeal carcinoma--review of the molecular mechanisms of tumorigenesis

Nasopharyngeal carcinoma (NPC) is a head and neck cancer rare throughout most of the world but common in certain geographic areas, such as southern Asia. While environmental factors and genetic susceptibility play important roles in NPC pathogenesis, the Epstein-Barr virus in particular has been implicated in the molecular abnormalities leading to NPC. There is upregulation of cellular proliferation pathways such as the Akt pathway, mitogen-activated protein kinases, and the Wnt pathway. Cell adhesion is compromised due to abnormal E-cadherin and beta-catenin function. Aberrations in cell cycle are due to dysregulation of factors such as p16, cyclin D1, and cyclin E. Anti-apoptotic mechanisms are also upregulated. There are multiple abnormalities unique to NPC that are potential targets for novel treatments.

Predicting prognosis using molecular profiling in estrogen receptor-positive breast cancer treated with tamoxifen

Background

Estrogen receptor positive (ER+) breast cancers (BC) are heterogeneous with regard to their clinical behavior and response to therapies. The ER is currently the best predictor of response to the anti-estrogen agent tamoxifen, yet up to 30–40% of ER+BC will relapse despite tamoxifen treatment. New prognostic biomarkers and further biological understanding of tamoxifen resistance are required. We used gene expression profiling to develop an outcome-based predictor using a training set of 255 ER+ BC samples from women treated with adjuvant tamoxifen monotherapy. We used clusters of highly correlated genes to develop our predictor to facilitate both signature stability and biological interpretation. Independent validation was performed using 362 tamoxifen-treated ER+ BC samples obtained from multiple institutions and treated with tamoxifen only in the adjuvant and metastatic settings.

Results

We developed a gene classifier consisting of 181 genes belonging to 13 biological clusters. In the independent set of adjuvantly-treated samples, it was able to define two distinct prognostic groups (HR 2.01 95%CI: 1.29–3.13; p = 0.002). Six of the 13 gene clusters represented pathways involved in cell cycle and proliferation. In 112 metastatic breast cancer patients treated with tamoxifen, one of the classifier components suggesting a cellular inflammatory mechanism was significantly predictive of response.

Conclusion

We have developed a gene classifier that can predict clinical outcome in tamoxifen-treated ER+ BC patients. Whilst our study emphasizes the important role of proliferation genes in prognosis, our approach proposes other genes and pathways that may elucidate further mechanisms that influence clinical outcome and prediction of response to tamoxifen.

Epstein-Barr virus-encoded LMP1 regulates epithelial cell motility and invasion via the ERK-MAPK pathway

The Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1) is an oncogenic protein which has previously been shown to engage the NF-kappaB, stress-activated MAP kinase, phosphatidylinositol 3-kinase (PI 3-kinase), and extracellular-regulated kinase (ERK)-MAPK pathways. In this study, we demonstrate that LMP1 activates ERK-MAPK in epithelial cells via the canonical Raf-MEK-ERK-MAPK pathway but in a Ras-independent manner. In agreement with the results of a previous study (B. A. Mainou, D. N. Everly, Jr., and N. Raab-Traub, J. Virol. 81:9680-9692, 2007), we show that the ability of LMP1 to activate ERK-MAPK mapped to its CTAR1 domain, the TRAF binding domain previously implicated in PI 3-kinase activation. A role for ERK-MAPK in LMP1-induced epithelial cell motility was identified, as LMP1-expressing cells displayed increased rates of haptotactic migration compared to those of LMP1-negative cells. These data implicate the ERK-MAPK pathway in LMP1-induced effects associated with transformation, suggesting that this pathway may contribute to the oncogenicity of LMP1 through its ability to promote cell motility and to enhance the invasive properties of epithelial cells.

The Kazal motifs of RECK protein inhibit MMP-9 secretion and activity and reduce metastasis of lung cancer cells in vitro and in vivo

RECK is a membrane-anchored glycoprotein which may negatively regulate matrix metalloproteinase (MMP) activity to suppress tumor invasion and metastasis. In this study, recombinant proteins corresponding to the residues 285–368 (named as CKM which contained cysteine knot motif), 605–799 (named as K123 which contained three Kazal motifs), 676–799 (named as K23 which contained the last two Kazal motifs) and full-length RECK were produced and their anti-cancer effects were tested. Full-length RECK and K23 but not K123 and CKM inhibited MMP9 secretion and activity. In addition, RECK and K23 inhibited invasion but not migration of metastatic lung cancer cells in vitro. Protein binding and kinetic study indicated that K23 physically interacted with MMP-9 and inhibited its activity by a non-competitive manner. Moreover, K23 reduced metastatic tumor growth in lungs of nude mice. Taken together, our results suggest that the K23 motifs of RECK protein can inhibit MMP-9 secretion and activity and attenuate metastasis of lung cancer cells.

RECK--a newly discovered inhibitor of metastasis with prognostic significance in multiple forms of cancer

The RECK (reversion-inducing cysteine rich protein with Kazal motifs) protein was initially discovered by its ability to induce reversion in ras-activated fibroblasts. The key action of RECK is to inhibit matrix metalloproteinases (MMPs) involved in breakdown of the extracellular matrix (ECM), and angiogenesis-namely MMP-2, MMP-9 and MTP-1. To this effect, it plays important physiological roles in embryogenesis and vasculogenesis. Additionally, it has a significant effect on tumorigenesis by limiting angiogenesis and invasion of tumours through the ECM. RECK has been studied in the context of a number of human tumours including colorectal, breast, pancreas, gastric, hepatocellular, prostate, and non-small cell lung carcinoma. In many of these tumours, RECK is down-regulated most likely as a result of inhibition at the Sp1 promoter site. MMP-2 and MMP-9 generally show an inverse association with RECK expression, but there are exceptions to this rule. Likewise, a reduction in tumour microvascular density (MVD) and VEGF have also been correlated with increased RECK levels, although more studies are required to define this effect. The predominant finding across all human tumour studies is a significantly improved prognosis (due to decreased invasion and metastasis) in tumours with preserved RECK expression. Although further research is required, RECK is a promising prognostic marker and potential therapeutic agent in multiple cancers.

Recklessness as a hallmark of aggressive cancer

Cancer recurrence after surgical treatment is a major concern for patients and doctors. Understanding what makes tumors prone to recurrence would be an important step toward its prevention. Accumulating evidence indicates that the level of membrane-associated protease regulator reversion-inducing cysteine-rich protein with Kazal motifs (RECK) expressed in tumor tissue is a good prognostic indicator in several common cancers. Certain members of the matrix metalloproteinase family are often upregulated in advanced cancers and are known to play important roles in tumor angiogenesis, invasion and metastasis. RECK negatively regulates several matrix metalloproteinases. Therefore, RECK itself may well be considered a promising tool or target molecule to be activated in cancer therapy. Here we review the recent advances in RECK research and discuss some of the important issues to be addressed in future studies.

Clinicopathologic implications of tissue inhibitor of metalloproteinase-1-positive diffuse large B-cell lymphoma

The tissue inhibitor of metalloproteinase-1 (TIMP-1) is a stromal factor that promotes plasmablastic differentiation, and the survival of germinal center B-cells. The expression of TIMP-1 is known to be correlated with a subset of non-Hodgkin lymphoma at the mRNA level, and Epstein-Barr virus infection in vitro. To characterize TIMP-1(+) diffuse large B-cell lymphoma, TIMP-1 expression was investigated in tissue microarrays from 182 cases of de novo diffuse large B-cell lymphoma and compared with prognostic factors, immunophenotypes, and Epstein-Barr virus infection status. TIMP-1 was expressed not only in tumor cells themselves, in 14 of 182 cases (8%), designated as TIMP-1(+) diffuse large B-cell lymphoma, but also in stromal cells like fibroblasts and endothelial cells. In univariate analysis and hierarchical clustering, our findings suggest that TIMP-1 expression may represent a distinct subgroup. In multivariate analysis, TIMP-1(+) diffuse large B-cell lymphoma (n=14) was associated with unfavorable outcomes compared to TIMP-1(-) diffuse large B-cell lymphoma (n=168) (odds ratio=2.5, P=0.049). Together with TIMP-1 expression, age (greater than 60 years), the presence of B-symptoms, abnormal lactate dehydrogenase level, or more advanced stage (III/IV) was correlated with a poor overall survival. However, TIMP-1 expression in diffuse large B-cell lymphoma was not correlated with other prognostic factors including: clinical stage, international prognostic index score, and nongerminal center B-cell phenotype, as well as Epstein-Barr virus infection. Our results suggest that TIMP-1 expression may be an independent negative prognostic factor in patients with diffuse large B-cell lymphoma.

Regulation of intracellular signalling by the terminal membrane proteins of members of the Gammaherpesvirinae

The human gamma(1)-herpesvirus Epstein-Barr virus (EBV) and the gamma(2)-herpesviruses Kaposi's sarcoma-associated herpesvirus (KSHV), rhesus rhadinovirus (RRV), herpesvirus saimiri (HVS) and herpesvirus ateles (HVA) all contain genes located adjacent to the terminal-repeat region of their genomes, encoding membrane proteins involved in signal transduction. Designated 'terminal membrane proteins' (TMPs) because of their localization in the viral genome, they interact with a variety of cellular signalling molecules, such as non-receptor protein tyrosine kinases, tumour-necrosis factor receptor-associated factors, Ras and Janus kinase (JAK), thereby initiating further downstream signalling cascades, such as the MAPK, PI3K/Akt, NF-kappaB and JAK/STAT pathways. In the case of TMPs expressed during latent persistence of EBV and HVS (LMP1, LMP2A, Stp and Tip), their modulation of intracellular signalling pathways has been linked to the provision of survival signals to latently infected cells and, hence, a contribution to occasional cellular transformation. In contrast, activation of similar pathways by TMPs of KSHV (K1 and K15) and RRV (R1), expressed during lytic replication, may extend the lifespan of virus-producing cells, alter their migration and/or modulate antiviral immune responses. Whether R1 and K1 contribute to the oncogenic properties of KSHV and RRV has not been established satisfactorily, despite their transforming qualities in experimental settings.

siRNA targeting LMP1-induced apoptosis in EBV-positive lymphoma cells is associated with inhibition of telomerase activity and expression

Epstein-Barr Virus (EBV) is closely associated with B cell malignancies. However, whether EBV appears to be absolutely required for cell proliferation and survival in lymphoma cells is still unknown. In this study, small interfering RNA (siRNA) targeting LMP1 was employed to investigate the effect of LMP1 on cell proliferation in EBV-positive lymphoblastoid B-cell line. A plasmid stable encoding 21-nt small RNA specifically and efficiently interfering LMP1 was constructed, resulting in a substantial loss of LMP1 mRNA and a significantly decreased LMP1 protein expression. Our data demonstrated that cell proliferation was completely inhibited and apoptosis was induced after knockdown of LMP1 gene in lymphoblastoid B-cell line. Also, we found that suppression of LMP1 caused downregulation of telomerase protein expression and decreased telomerase activity in lymphoma cells. In EBV-negative NPC cell line, transfection of plasmid expressing LMP1 greatly enhanced telomerase protein expression. Our results suggested that siRNA targeting LMP1 can induce apoptosis in EBV-positive lymphoma cells and is associated with inhibition of telomerase activity and expression. siRNA-directed LMP1 silencing may be of the therapeutic value for preventing and treating those EBV-associated tumors.

RECK-Mediated Suppression of Tumor Cell Invasion Is Regulated by Glycosylation in Human Tumor Cell Lines

RECK, a glycosylphosphatidylinositol (GPI)-anchored glycoprotein, negatively regulates matrix metalloproteinases (MMP), such as MMP-9, and inhibits tumor invasion and metastasis. The predicted amino acid sequence of human RECK includes five putative N-glycosylation sites; however, the precise biochemical role of glycosylated RECK remains unknown. In this study, we examined the link between glycosylation and the function of RECK in human tumor cell lines. RECK protein was glycosylated at Asn86, Asn200, Asn297, and Asn352 residues but not at the Asn39 residue in HT1080 cells. Although the glycosylation of these asparagine sites did not play a role in the cell surface localization of RECK as a GPI-anchored protein, the glycosylation of RECK Asn297 residue was involved in the suppression of MMP-9 secretion and Asn352 residue was necessary to inhibit MMP-2 activation. Moreover, RECK-suppressed tumor cell invasion was reversed by inhibiting glycosylation at Asn86, Asn297, and Asn352 residues of RECK. Thus, these findings indicate that glycosylation mediates RECK suppression of tumor cell invasion by multiple mechanisms such as suppressing MMP-9 secretion and inhibiting MMP-2 activation.