Regulation of Nm23-H1 and cell invasiveness by Kaposi's sarcoma-associated herpesvirus

Nuclear NME1 enhances the malignant behavior of A549 cells and impacts lung adenocarcinoma patient prognosis

NME1 is a metastatic suppressor inconsistently reported to have multiple roles as both a promoter and inhibitor of cancer metastasis. Nevertheless, the specific mechanism behind these results is still unclear. We observed that A549 cells with stable transfer of NME1 into the nucleus (A549-nNm23-H1) exhibited significantly increased migration and invasion activity compared to vector control cells, which was further enhanced by over-expressing CYP24A1 (p < 0.001). NME1 demonstrated the ability to safely attach to and amplify the transcription activation of JUN, consequently leading to the up-regulation of CYP24A1. Analysis of clinical data showed a positive relationship between nuclear NME1 levels and CYP24A1 expression. Furthermore, they were positively associated with postoperative distant metastasis and negatively correlated with prognosis in those with early stage lung adenocarcinoma. In conclusion, the data presented provides a new understanding of the probable pathways by which nuclear NME1 facilitates tumor metastasis, establishing the groundwork for future prediction and treatment of tumor metastasis.

The multiple regulation of metastasis suppressor NM23-H1 in cancer

Metastasis is one of the leading causes of mortality in cancer patients. As the firstly identified metastasis suppressor, NM23-H1 has been endowed with expectation as a potent target in metastatic cancer therapy during the past decades. However, many challenges impede its clinical use. Accumulating evidence shows that NM23-H1 has a dichotomous role in tumor metastasis as a suppressor and promoter. It has potentially attributed to its versatile biochemical characteristics such as nucleoside diphosphate kinase (NDPK) activity, histidine kinase activity (HPK), exonuclease activity, and protein scaffold, which further augment the complexity and uncertainty of its physiological function. Simultaneously, tumor cells have evolved multiple ways to regulate the expression and function of NM23-H1 during tumorigenesis and metastasis. This review summarized and discussed the regulatory mechanisms of NM23-H1 in cancer including transcriptional activation, subcellular location, enzymatic activity, and protein degradation, which significantly modulate its anti-metastatic function.

Hepatitis C virus core protein interacts with cellular metastasis suppressor Nm23-H1 and promotes cell migration and invasion

Hepatitis C virus (HCV) is the major etiological agent of hepatocellular carcinoma (HCC), which is the fourth most common cause of cancer-related deaths worldwide and second in terms of deaths of males (Bray et al. in CA Cancer J Clin 68(6):394-424, 2018). HCV-induced HCC is a multi-step process that involves alteration of several host regulatory pathways. One of the key features of HCV-associated hepatocellular carcinoma is the metastasis of cancer cells to different organs. Human Nm23-H1 is one of the best-studied metastasis suppressor proteins, and it has been shown to be modulated in many human cancers. Our study shows that the core protein of HCV genotype 2a can co-localize and interact directly with Nm23-H1 within cancer cells, resulting in modulation of the anti-metastasis properties of Nm23-H1. The HCV core protein promotes SUMOylation and degradation of the Nm23-H1 protein, as well as transcriptional downregulation. This study provides evidence that the HCV core protein is a pro-metastatic protein that can interact directly with and modulate the functions of cellular metastasis suppressor Nm23-H1.

An endothelial cell line infected by Kaposi's sarcoma-associated herpes virus (KSHV) allows the investigation of Kaposi's sarcoma and the validation of novel viral inhibitors in vitro and in vivo

Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiological agent of Kaposi's sarcoma (KS), a tumor of endothelial origin predominantly affecting immunosuppressed individuals. Up to date, vaccines and targeted therapies are not available. Screening and identification of anti-viral compounds are compromised by the lack of scalable cell culture systems reflecting properties of virus-transformed cells in patients. Further, the strict specificity of the virus for humans limits the development of in vivo models. In this study, we exploited a conditionally immortalized human endothelial cell line for establishment of in vitro 2D and 3D KSHV latency models and the generation of KS-like xenograft tumors in mice. Importantly, the invasive properties and tumor formation could be completely reverted by purging KSHV from the cells, confirming that tumor formation is dependent on the continued presence of KSHV, rather than being a consequence of irreversible transformation of the infected cells. Upon testing a library of 260 natural metabolites, we selected the compounds that induced viral loss or reduced the invasiveness of infected cells in 2D and 3D endothelial cell culture systems. The efficacy of selected compounds against KSHV-induced tumor formation was verified in the xenograft model. Together, this study shows that the combined use of anti-viral and anti-tumor assays based on the same cell line is predictive for tumor reduction in vivo and therefore allows faithful selection of novel drug candidates against Kaposi's sarcoma. KEY MESSAGES: Novel 2D, 3D, and xenograft mouse models mimic the consequences of KSHV infection. KSHV-induced tumorigenesis can be reverted upon purging the cells from the virus. A 3D invasiveness assay is predictive for tumor reduction in vivo. Chondramid B, epothilone B, and pretubulysin D diminish KS-like lesions in vivo.

Clinical Implication and the Hereditary Factors of NM23 in Hepatocellular Carcinoma Based on Bioinformatics Analysis and Genome-Wide Association Study

NM23 expression is closely associated with hepatocellular carcinoma (HCC) recurrence, but the hereditary factors influencing NM23 levels are unknown. Using public database, the diagnostic value of NM23 in HCC was investigated. A total of 424 hepatitis B virus- (HBV-) related HCC patients were enrolled to perform a genome–wide association study for identifying candidate variants associated with NM23 expression level. Additionally, a logistic regression model, haplotypes, and survival analysis were performed in the subsequent analysis. We identified high NM23 expression levels that have a diagnostic accuracy in HCC tissues and had a poor recurrence-free survival in HBV-related HCC patients. Variants near Psoriasis susceptibility 1 candidate 1 (PSORS1C1) and StAR related lipid transdomain containing 3 (STARD3) are associated with NM23 expression. The PSORS1C1 haplotype TGCACA and the STARD3 haplotype GG have favorable cumulative effects on NM23 expression. Further, variants in PSORS1C1 were associated with either overall survival (rs556285588, rs3095301, and rs3131003) only or overall survival and recurrence-free survival (rs560052000 and rs541820233) both in HCC patients. Our findings suggested that variants at the PSORS1C1 and STARD3 loci play an important role in NM23 regulation. Moreover, variants in PSORS1C1 are potential biomarkers for the prediction of postoperative clinical outcomes in HBV-related HCC patients. Thus, variants in PSORS1C1 and STARD3 are associated with NM23 expression and clinical outcomes of HBV-related HCC patients, which may be regarded as potential biomarkers for this disease.

KSHV co-infection regulates HPV16+ cervical cancer cells pathogenesis in vitro and in vivo

High-risk human papillomavirus (HPV) infection is the etiological agent of cervical, oral and oropharyngeal cancers. Another oncogenic virus, Kaposi sarcoma-associated herpesvirus (KSHV) can cause several human cancers arising in those immunocompromised patients. KSHV DNA has been detected in the oral cavity and the female genital tract, although its detection rate in cervical samples is relatively low. Therefore, it remains unclear about the role of KSHV co-infection in the development of HPV-related neoplasia. We recently report that KSHV infection of HPV16+ cervical cancer cell line SiHa induces several pro-inflammatory factors production while reducing HPV16 E6 and E7 expression through the manipulation of cellular microRNA function. In the current study, we focus on determining the influence of KSHV co-infection on cervical cancer cells pathogenesis in vitro and in vivo. We found that KSHV co-infection is able to maintain SiHa and/or CaSki cells pathogenesis and tumorigenesis, although hijacking HPV oncogenic proteins expression. In mechanisms, KSHV co-infection is capable of increasing Macrophage migration inhibitory factor (MIF) and its receptor CXCR2 expression from cervical cancer cells, which may contribute to cervical cancer development. Our data indicate that KSHV co-infection may act as a potential co-factor to promote HPV-related neoplasia development.

KSHV co-infection down-regulates HPV16 E6 and E7 from cervical cancer cells

High-risk human papillomavirus (HPV) infection is the etiological agent of some malignancies such as cervical, oral and oropharyngeal cancers. Kaposi sarcoma-associated herpesvirus (KSHV) represents a principal causative agent of several human cancers arising in those immunocompromised patients. Interestingly, KSHV DNA has been detected in the oral cavity and the female genital tract, although its detection rate in cervical samples is very low and few reports are about KSHV/HPV co-infection. Therefore, it remains unclear about the role of KSHV co-infection in the development of HPV-related neoplasias. In the current study, we report that HPV16-integrated cervical cancer cell-line SiHa is susceptible to KSHV latent infection and replication. We also have found that KSHV infection or viral latent proteins are capable of reducing HPV16 E6/E7 expression through the manipulation of cellular microRNA function. Array analysis indicates that KSHV infection induces some inflammatory cytokines/chemokines production as well as up-regulates a series of interferon-induced genes expression, which may facilitate host immune defense system attacking these co-infected cells and clearance of viruses. Together, our data have provided possible explanations for very low detection rate of KSHV shedding as well as of KSHV/HPV co-infection in cervical samples and/or cervical cancer cells.

Oncogenic Epstein-Barr virus recruits Nm23-H1 to regulate chromatin modifiers

In cancer progression, metastasis is a major cause of poor survival of patients and can be targeted for therapeutic interventions. The first discovered metastatic-suppressor Nm23-H1 possesses nucleoside diphosphate kinase, histidine kinase, and DNase activity as a broad-spectrum enzyme. Recent advances in cancer metastasis have opened new ways for the development of therapeutic molecular approaches. In this review, we provide a summary of the current understanding of Nm23/NDPKs in the context of viral oncogenesis. We also focused on Nm23-H1-mediated cellular events with an emphasis on chromatin modifications. How Nm23-H1 modulates the activities of chromatin modifiers through interaction with Epstein-Barr virus-encoded oncogenic antigens and related crosstalks are discussed in the context of other oncogenic viruses. We also described the current understanding of the cellular and viral interactions of Nm23-H1 and their reference to transcription regulation and metastasis. Further, we summarized the recent therapeutic approaches targeting Nm23 and its potential links to pathways that can be exploited by oncogenic viruses.

Correlation between NM23 protein overexpression and prognostic value and clinicopathologic features of ovarian cancer: a meta-analysis

OBJECTIVE

The prognostic value and clinicopathological features of NM23 (non-metastasis 23) have previously been assessed, but the results are controversial. Here, we attempted to clarify the correlation between NM23 expression and its prognostic value and the clinicopathological features in ovarian cancer (OC).

METHODS

The relevant studies were identified using PubMed, Embase, and Web of Science. We calculated the pooled odds ratio (OR) with 95% confidence intervals (CIs) for overall survival (OS), progression-free survival (PFS), and clinicopathological features. We used OS to evaluate the prognostic value of NM23 expression in patients with OC. Subgroup analyses were used to explore the source of heterogeneity.

RESULTS

We included 10 studies involving 894 patients in our assessment of the association between NM23 expression and OS for OC. Our data indicated that NM23 expression was not associated with improved OS (OR 0.83, 95% CI 0.41-1.68, P = 0.61) or PFS (OR 0.7, 95% CI 0.39-1.24, P = 0.22). Elevated NM23 expression was associated with differentiation grade (OR 0.35, 95% CI 0.2-0.6, P = 0.0002) and N status (OR 0.33, 95% CI 0.14-0.78, P = 0.01), whereas there was no significant difference between NM23 expression and tumor stage (OR 1.1, 95% CI 0.45-2.66, P = 0.84). Subgroup analysis did not reveal any potential source of heterogeneity. No obvious publication bias was found.

CONCLUSIONS

In OC, there is poor statistical significance between NM23 expression and OS and PFS, but NM23 expression is related to differentiation grade and N status. This meta-analysis reveals that NM23 expression is a potential factor of poor prognosis in OC. The prognostic role of NM23 in different OC stages in combination with the clinical characteristics suggests a novel approach for developing future therapeutic targets.

Hepatitis C Virus E1 protein promotes cell migration and invasion by modulating cellular metastasis suppressor Nm23-H1

Hepatocellular carcinoma (HCC) is the most prevalent primary liver cancer and its incidence is on the rise largely attributed to Hepatitis C virus (HCV) related liver cancer. A distinct feature of HCV associated HCC is the substantially increased incidence of metastasis compared to non-viral or HBV associated HCC. Nm23-H1 is the first reported human metastasis suppressor down-regulated in many human metastatic cancers. Nm23-H1 functions are modulated in several virus associated cancers. Our study now shows that HCV E1 protein expression as well as HCV infection induces pro-metastatic effect on cancer cells which is simultaneous to Nm23-H1 transcriptional down-regulation and Nm23-H1 protein degradation. Moreover, Nm23-H1 intracellular localization is significantly altered in cells expressing HCV E1 protein. Importantly, overexpression of Nm23-H1 can rescue the cancer cells from pro-metastatic effects of HCV E1 and HCV infection. Our limited study provides evidence for role for Nm23-H1 in HCV mediated cancer metastasis.

The role of NM23 in patients with colorectal cancer: A systematic review and meta-analysis

This meta-analysis was carried out to evaluate the relationship between NM23 expression and the prognosis of patients with colorectal cancer. We searched PubMed, EMBASE and Web of Science for relevant articles. The pooled odd ratios (ORs) and corresponding 95%CI were calculated to evaluate the prognostic value of NM23 expression in patients with colorectal cancer, and the association between NM23 expression and clinicopathological factors. In total, 2289 patients were pooled from 24 available studies. The incorporative OR combined by 16 studies with overall survival showed that high NM23 expression was associated with better overall survival (OR=0.67, 95%CI: 0.49-0.93, P=0.02, I ²=56%, Ph=0.004). And a new estimate without heterogeneity was produced when only combining high-quality studies (OR=0.70, 95%CI: 0.56-0.86, P=0.0007, I ²=46%). In disease free survival (DFS), we also obtained a good prognosis (OR=0.30, 95%CI: 0.14-0.68, P=0.004). Although we failed to find any significance in N status (P=0.10), elevated NM23 expression was related to well tumor differentiation (OR=0.60, 95%CI: 0.44-0.820, P=0.001) and Dukes' A&B (OR=0.55, 95%CI: 0.32-0.95, P=0.03). These results indicated that over-expressed NM23 might be an indicator of good prognosis, well tumor differentiation and Dukes' A&B of patients with colorectal cancer, but no significance was found in N status.

Metastasis suppressor NM23 limits oxidative stress in mammals by preventing activation of stress-activated protein kinases/JNKs through its nucleoside diphosphate kinase activity

NME1 (nonmetastatic expressed 1) gene, which encodes nucleoside diphosphate kinase (NDPK) A [also known as nonmetastatic clone 23 (NM23)-H1 in humans and NM23-M1 in mice], is a suppressor of metastasis, but several lines of evidence-mostly from plants-also implicate it in the regulation of the oxidative stress response. Here, our aim was to investigate the physiologic relevance of NDPK A with respect to the oxidative stress response in mammals and to study its molecular basis. NME1-knockout mice died sooner, suffered greater hepatocyte injury, and had lower superoxide dismutase activity than did wild-type (WT) mice in response to paraquat-induced acute oxidative stress. Deletion of NME1 reduced total NDPK activity and exacerbated activation of the stress-related MAPK, JNK, in the liver in response to paraquat. In a mouse transformed hepatocyte cell line and in primary cultures of normal human keratinocytes, MAPK activation in response to H₂O₂ and UVB, respectively, was dampened by expression of NM23-M1/NM23-H1, dependent on its NDPK catalytic activity. Furthermore, excess or depletion of NM23-M1/NM23-H1 NDPK activity did not affect the intracellular bulk concentration of nucleoside di- and triphosphates. NME1-deficient mouse embryo fibroblasts grew poorly in culture, were more sensitive to stress than WT fibroblasts, and did not immortalize, which suggested that they senesce earlier than do WT fibroblasts. Collectively, these results indicate that the NDPK activity of NM23-M1/NM23-H1 protects cells from acute oxidative stress by inhibiting activation of JNK in mammal models.-Peuchant, E., Bats, M.-L., Moranvillier, I., Lepoivre, M., Guitton, J., Wendum, D., Lacombe, M.-L., Moreau-Gaudry, F., Boissan, M., Dabernat, S. Metastasis suppressor NM23 limits oxidative stress in mammals by preventing activation of stress-activated protein kinases/JNKs through its nucleoside diphosphate kinase activity.

Prognostic and clinicopathological value of NM23 expression in patients with breast cancer: A systematic review and meta-analysis

It is hypothesized that, NM23, as a metastasis suppressor gene, may be a good indicator of patients with breast cancer in most reports. The aim of our meta-analysis was to determine the prognostic value of NM23 in patients with breast cancer synthetically, by searching 3 databases, PubMed, EMBASE, and Web of Science, for relevant articles. The inclusion criteria, exclusion criteria, and the standard-of-quality assessment were used according to a previous protocol. The pooled odd ratios (ORs) and corresponding 95% CI were calculated to assess the primary end point, survival data, and the secondary end point, associations between NM23 expression and clinicopathological factors. Finally, funnel plots and Egger׳s linear regression test were used to assess the potential publication bias. Overall, 792 articles were retrieved in the initial search of databases, and 4968 patients were eventually pooled from 26 available studies selected out by 2 independent reviewers. The incorporative OR showed that elevated NM23 expression was associated with better overall survival (OR = 0.62; 95% CI: 0.52-0.74; P < 0.00001; I² = 0%; Ph = 0.46). In disease-free survival, we also obtained a good prognosis (OR = 0.30; 95% CI: 0.18-0.48; P < 0.00001; I² = 46%; Ph = 0.13). In addition, high-NM23 expression was correlated with well or moderate histologic grade, negative lymph node metastasis, and early tumor staging. Furthermore, publication bias was detected in overall survival but not in disease-free survival, and it could also be verified by Egger׳s test (P = 0.009 and P = 0.687, respectively). These results implied that NM23 might be an indicator of good prognosis in patients with breast cancer, although further researches need to be performed to confirm the prognostic value of NM23.

Prognostic Value of NME1 (NM23-H1) in Patients with Digestive System Neoplasms: A Systematic Review and Meta-Analysis

OBJECTIVE

There is a heated debate on whether the prognostic value of NME1 is favorable or unfavorable. Thus, we carried out a meta-analysis to evaluate the relationship between NME1 expression and the prognosis of patients with digestive system neoplasms.

METHODS

We searched PubMed, EMBASE and Web of Science for relevant articles. The pooled odd ratios (ORs) and corresponding 95%CI were calculated to evaluate the prognostic value of NME1 expression in patients with digestive system neoplasms, and the association between NME1 expression and clinicopathological factors. We also performed subgroup analyses to find out the source of heterogeneity.

RESULTS

2904 patients were pooled from 28 available studies in total. Neither the incorporative OR combined by 17 studies with overall survival (OR = 0.65, 95%CI:0.41-1.03, P = 0.07) nor the pooled OR with disease-free survival (OR = 0.75, 95%CI:0.17-3.36, P = 0.71) in statistics showed any significance. Although we couldn't find any significance in TNM stage (OR = 0.78, 95%CI:0.44-1.36, P = 0.38), elevated NME1 expression was related to well tumor differentiation (OR = 0.59, 95%CI:0.47-0.73, P<0.00001), negative N status (OR = 0.54, 95%CI:0.36-0.82, P = 0.003) and Dukes' stage (OR = 0.43, 95%CI:0.24-0.77, P = 0.004). And in the subgroup analyses, we only find the "years" which might be the source of heterogeneity of overall survival in gastric cancer.

CONCLUSIONS

The results showed that statistically significant association was found between NME1 expression and the tumor differentiation, N status and Dukes' stage of patients with digestive system cancers, while no significance was found in overall survival, disease-free survival and TNM stage. More and further researches should be conducted to reveal the prognostic value of NME1.

Dissecting the contribution of EBNA3C domains important for EBV-induced B-cell growth and proliferation

Epstein-Barr virus (EBV) is an oncogenic gammaherpes virus which is linked to pathogenesis of several human lymphatic malignancies. The EBV essential latent antigen EBNA3C is critical for efficient conversion of primary human B-lymphocytes to lymphoblastic cell lines and for continued LCL growth. EBNA3C, an EBV latent antigen with oncogenic potential can bind and regulate the functions of a wide range of cellular transcription factors. In our current reverse genetics study, we deleted the full length EBNA3C, and independently the RBP-Jκ and Nm23-H1 binding sites within EBNA3C using BACmid recombinant engineering methodology. Our experiments demonstrated that deletion of the EBV EBNA3C open reading frame (ORF) and more specifically the residues 621–675 which binds Nm23H1 and SUMO-1 showed a significant reduction in the ability of the cells to proliferate. Furthermore, they exhibited lower infectivity of human peripheral blood mononuclear cells (PBMCs). We also showed that recombinant EBV with deletions of the EBNA3C ORF, as well as a recombinant with residues 621–675 within EBNA3C ORF deleted had diminished abilities to activate CD40. Our study also revealed that the full length (1–992) and 621–675 aa deletions of EBNA3C when compared to wild type EBV infected PBMCs had differential expression patterns for the phosphorylation of MAP kinases specifically p38, JNK and ERK. Regulation of β-catenin also differed among wild type and EBNA3C deleted mutants. These temporal differences in signaling activities of these recombinant viruses in PBMCs is likely important in defining their functional importance in EBV-mediated B-cell transformation.

Mutation of the nm23-H1 gene has a non-dominant role in colorectal adenocarcinoma

Nm23-H1 is a metastasis suppressor gene, which is has a reduced expression in patients with digestive system cancer. However, the mechanistic basis for the genetic instability remains unknown. To study the expression of the nm23-H1 gene in patients with colorectal cancer, polymerase chain reaction-single strand conformation polymorphism was used to analyze any point mutation, and immunohistochemistry was used to detect the expression of nm23-H1. Results revealed that all 63 specimens of Chinese human colorectal cancer tissues exhibit no point mutation. Among those 63 specimens, 19 (30%) exhibited positive immunostaining for the nm23-H1 protein and 44 (70%) exhibited negative immunostaining. These observations suggested that the protein and gene expression levels of nm23-H1 are reduced in colorectal cancer compared with the adjacent normal tissues, and the point mutation in the nm23-H1 gene is not the dominant cause of metastatic colorectal cancer.

CD147: regulator of hyaluronan signaling in invasiveness and chemoresistance

Major determinants that influence negative outcome in cancer patients are the abilities of cancer cells to resist current therapies and to invade surrounding host tissue, consequently leading to local and metastatic dissemination. Hyaluronan (HA), a prominent constituent of the tumor microenvironment, not only provides structural support but also interacts with cell surface receptors, especially CD44, that influence cooperative signaling pathways leading to chemoresistance and invasiveness. CD147 (emmprin; basigin) is a member of the Ig superfamily that has also been strongly implicated in chemoresistance and invasiveness. CD147 both regulates HA synthesis and interacts with the HA receptors, CD44, and LYVE-1. Increased CD147 expression induces formation of multiprotein complexes containing CD44 (or LYVE-1) as well as members of the membrane-type matrix metalloproteinase, receptor tyrosine kinase, ABC drug transporter, or monocarboxylate transporter families, which become assembled in specialized lipid raft domains along with CD147 itself. In each case, multivalent HA-receptor interactions are essential for formation or stabilization of the lipid raft complexes and for downstream signaling pathways or transporter activities that are driven by these complexes. We conclude that cooperativity between HA, HA receptors, and CD147 may be a major driver of the interconnected pathways of invasiveness and chemoresistance widely critical to malignancy.

Regulation of the metastasis suppressor Nm23-H1 by tumor viruses

Metastasis is the most common cause of cancer mortality. To increase the survival of patients, it is necessary to develop more effective methods for treating as well as preventing metastatic diseases. Recent advancement of knowledge in cancer metastasis provides the basis for development of targeted molecular therapeutics aimed at the tumor cell or its interaction with the host microenvironment. Metastasis suppressor genes (MSGs) are promising targets for inhibition of the metastasis process. During the past decade, functional significance of these genes, their regulatory pathways, and related downstream effector molecules have become a major focus of cancer research. Nm23-H1, first in the family of Nm23 human homologues, is a well-characterized, anti-metastatic factor linked with a large number of human malignancies. Mounting evidence to date suggests an important role for Nm23-H1 in reducing virus-induced tumor cell motility and migration. A detailed understanding of the molecular association between oncogenic viral antigens with Nm23-H1 may reveal the underlying mechanisms for tumor virus-associated malignancies. In this review, we will focus on the recent advances to our understanding of the molecular basis of oncogenic virus-induced progression of tumor metastasis by deregulation of Nm23-H1.

EphrinA2 regulates clathrin mediated KSHV endocytosis in fibroblast cells by coordinating integrin-associated signaling and c-Cbl directed polyubiquitination

Kaposi's sarcoma-associated herpesvirus (KSHV) interacts with human dermal endothelial cell surface tyrosine kinase EphrinA2 (EphA2) and integrins (α3β1 and αVβ3) in the lipid raft (LR) region, and EphA2 regulates macropinocytic virus entry by coordinating integrin-c-Cbl associated signaling. In contrast, KSHV enters human foreskin fibroblast (HFF) cells by LR-independent clathrin mediated endocytosis. The present studies conducted to identify the key molecules regulating KSHV entry in HFF cells showed that KSHV induces association with integrins (αVβ5, αVβ3 and α3β1) and EphA2 in non-LR regions early during infection and activates EphA2, which in turn associates with phosphorylated c-Cbl, myosin IIA, FAK, Src, and PI3-K, as well as clathrin and its adaptor AP2 and effector Epsin-15 proteins. EphA2 knockdown significantly reduced these signal inductions, virus internalization and gene expression. c-Cbl knockdown ablated the c-Cbl mediated K63 type polyubiquitination of EphA2 and clathrin association with EphA2 and KSHV. Mutations in EphA2's tyrosine kinase domain (TKD) or sterile alpha motif (SAM) abolished its interaction with c-Cbl. Mutations in tyrosine kinase binding (TKB) or RING finger (RF) domains of c-Cbl resulted in very poor association of c-Cbl with EphA2 and decreased EphA2 polyubiquitination. These studies demonstrated the contributions of these domains in EphA2 and c-Cbl association, EphA2 polyubiquitination and virus-EphA2 internalization. Collectively, these results revealed for the first time that EphA2 influences the tyrosine phosphorylation of clathrin, the role of EphA2 in clathrin mediated endocytosis of a virus, and c-Cbl mediated EphA2 polyubiquitination directing KSHV entry in HFF cells via coordinated signal induction and progression of endocytic events, all of which suggest that targeting EphA2 and c-Cbl could block KSHV entry and infection.

Emmprin and KSHV: new partners in viral cancer pathogenesis

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Emmprin regulates pathogenic elements relevant to virus-associated cancer, including drug resistance and cell migration.

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Kaposi's sarcoma-associated herpesvirus (KSHV) regulates emmprin expression and downstream function.

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Targeting emmprin or its interacting proteins at the cell surface suppresses KSHV-induced pathogenesis in vitro.

Emmprin (CD147; basigin) is a multifunctional glycoprotein expressed at higher levels by cancer cells and stromal cells in the tumor microenvironment. Through direct effects within tumor cells and promotion of tumor–stroma interactions, emmprin participates in induction of tumor cell invasiveness, angiogenesis, metastasis and chemoresistance. Although its contribution to cancer progression has been widely studied, the role of emmprin in viral oncogenesis still remains largely unclear, and only a small body of available literature implicates emmprin-associated mechanisms in viral pathogenesis and tumorigenesis. We summarize these data in this review, focusing on the role of emmprin in pathogenesis associated with the Kaposi sarcoma-associated herpesvirus (KSHV), a common etiology for cancers arising in the setting of immune suppression. We also discuss future directions for mechanistic studies exploring roles for emmprin in viral cancer pathogenesis.

Kaposi's sarcoma-associated herpesvirus suppression of DUSP1 facilitates cellular pathogenesis following de novo infection

Kaposi's sarcoma-associated herpesvirus (KSHV) is the causative agent of Kaposi's sarcoma (KS), and KSHV activation of mitogen-activated protein kinases (MAPKs) initiates a number of key pathogenic determinants of KS. Direct inhibition of signal transduction as a therapeutic approach presents several challenges, and a better understanding of KSHV-induced mechanisms regulating MAPK activation may facilitate the development of new treatment or prevention strategies for KS. MAPK phosphatases, including dual-specificity phosphatase-1 (DUSP1), negatively regulate signal transduction and cytokine activation through MAPK dephosphorylation or interference with effector molecule binding to MAPKs, including the extracellular signal-regulated kinase (ERK). We found that ERK-dependent latent viral gene expression, the induction of promigratory factors, and cell invasiveness following de novo infection of primary human endothelial cells are in part dependent on KSHV suppression of DUSP1 expression during de novo infection. KSHV-encoded miR-K12-11 upregulates the expression of xCT (an amino acid transporter and KSHV fusion/entry receptor), and existing data indicate a role for xCT in the regulation of 14-3-3β, a transcriptional repressor of DUSP1. We found that miR-K12-11 induces endothelial cell secretion of promigratory factors and cell invasiveness through upregulation of xCT-dependent, 14-3-3β-mediated suppression of DUSP1. Finally, proof-of-principle experiments revealed that pharmacologic upregulation of DUSP1 inhibits the induction of promigratory factors and cell invasiveness during de novo KSHV infection. These data reveal an indirect role for miR-K12-11 in the regulation of DUSP1 and downstream pathogenesis.

Nucleoside-diphosphate-kinase: a pleiotropic effector in microbial colonization under interdisciplinary characterization

Emerging evidence identifies multiple roles for nucleoside-diphosphate-kinase in host-microbe interaction. We provide the first synopsis of utilization of this molecule by various microorganisms during colonization of host tissues. Additionally, we propose novel mechanisms this effector may participate in, which could be crucial for microbial adaptation in chronic host infection.

Kaposi sarcoma-associated herpesvirus (KSHV) induces a functional tumor-associated phenotype for oral fibroblasts

The Kaposi sarcoma-associated herpesvirus (KSHV) is the causative agent of Kaposi sarcoma (KS), the most common HIV/AIDS-associated tumor worldwide. Involvement of the oral cavity portends a poor prognosis for patients with KS, but mechanisms for KSHV regulation of the oral tumor microenvironment are largely unknown. Infiltrating fibroblasts are found with KS lesions, and KSHV establishes latent infection within human primary fibroblasts in vitro, but contributions for KSHV-infected fibroblasts to the KS microenvironment have not been previously characterized. Secretion of pro-migratory factors and intratumoral invasion are characteristics of tumor-associated fibroblasts (TAF) found in the microenvironment of non-viral malignancies. In the present study, we show that latent KSHV infection of primary human fibroblasts isolated from the oral cavity enhances their secretion of KS-promoting cytokines and intrinsic invasiveness through VEGF-dependent mechanisms. Moreover, we find that KSHV induces these effects through Sp1- and Egr2-dependent transcriptional activation of the Extracellular Matrix MetalloPRoteinase INducer (emmprin). These data implicate KSHV activation of emmprin in the induction of a "TAF-like" phenotype for oral fibroblasts in the KS microenvironment and support the potential utility of targeting TAFs and/or emmprin in the treatment of oral KS.

Functional modulation of the metastatic suppressor Nm23-H1 by oncogenic viruses

Evidence over the last two decades from a number of disciplines has solidified some fundamental concepts in metastasis, a major contributor to cancer associated deaths. However, significant advances have been made in controlling this critical cellular process by focusing on targeted therapy. A key set of factors associated with this invasive phenotype is the nm23 family of over twenty metastasis-associated genes. Among the eight known isoforms, Nm23-H1 is the most studied potential anti-metastatic factor associated with human cancers. Importantly, a growing body of work has clearly suggested a critical role for Nm23-H1 in limiting tumor cell motility and progression induced by several tumor viruses, including Epstein-Barr virus (EBV), Kaposi's sarcoma associated herpes virus (KSHV) and human papilloma virus (HPV). A more in depth understanding of the interactions between tumor viruses encoded antigens and Nm23-H1 will facilitate the elucidation of underlying mechanism(s) which contribute to virus-associated cancers. Here, we review recent studies to explore the molecular links between human oncogenic viruses and progression of metastasis, in particular the deregulation of Nm23-H1 mediated suppression.