Patients reporting persistent olfactory impairment after previously documented olfactory loss indicate a higher level of disability and lower quality of life than those with perceived resolution of olfactory compromise.

The transmembrane heparan sulfate proteoglycan syndecan-1 was identified from a human placenta cDNA library by the expression cloning method as a gene product that interacts with membrane type matrix metalloproteinase-1 (MT1- Syndecans are transmembrane heparan sulfate proteoglycans expressed on all adherent cells (1, 2) and have been proposed to play an important role in tissue morphogenesis by virtue of their ability to bind, via their covalently attached glycosaminoglycan chains, to a variety of extracellular adhesive molecules including fibronectin, thrombospondin, various collagens, and heparin-binding growth-associated molecules and growth factors such as basic fibroblast growth factor (3-8).MMPSince the expression of syndecans appears to be controlled during both development and the progression of tumor cells to the metastatic phenotype, it has been proposed that syndecans are important regulators of the migratory and invasive behaviors of both normal and transformed cells (9, 10). The syndecan family is composed of four closely related proteins (syndecan-1, -2, -3, and -4) encoded by four different genes. Syndecan-1 is abundant in normal epithelial cells and tissues, localizing to both basal and suprabasal cell layers (1). Disruption of syndecan-1 expression in cultured cells leads to an epithelial mesenchymal transformation, with associated changes in cell polarity and cell-cell adhesion and altered epithelium-specific gene expression (7, 11).The intact ectodomain of each syndecan is constitutively shed from cultured cells (12, 13) as part of normal cell surface heparan sulfate proteoglycan turnover (14). Ectodomain shedding appears to contribute to diverse pathophysiological events such as host defense, wound healing, arthritis, and Alzheimer's disease, but how shedding is regulated remains largely unknown (15-17).Matrix metalloproteinases (MMPs) 1 are a family of Zn 2ϩ -dependent enzymes that are known to cleave extracellular matrix proteins in normal and pathological conditions (18 -20). To date, more than 20 mammalian MMPs have been identified by cDNA cloning, and they can be subgrouped into soluble type and membrane type MMPs (MT-MMPs) (20,21). MMPs are overexpressed in various human malignancies and have been thought to contribute to tumor invasion and metastasis by degrading extracellular matrix components (18,22). Thus, the level of MMP expression correlates with the invasiveness or malignancy of tumors (23,24). Particularly, MT1-MMP, MMP-2, MMP-7, and MMP-9 have been reported to be most closely associated with tumor invasion and metastasis. Whereas degradation of extracellular matrix is an important aspect of MMP biology, growing evidence has demonstrated specific processing/activation or degradation of cell surface receptors and ligands. Fas ligand (25), tumor necrosis factor-␣ (26), the ectodomain of the fibroblast growth factor receptor-1 (27), the heparin-binding epidermal growth factor (28), and interleukin-8 (29) were reported to be released or activated by MMPs. MMPs also cleave and inac...

. Moreover, LMP1 induces HIF-1 DNA binding activity and upregulates HRE and VEGF promoter transcriptional activity. Finally, LMP1 increases the appearance of VEGF protein in extracellular fluids; induction of VEGF is suppressed by PD98059 or catalase. These results suggest that LMP1 increases HIF-1 activity through induction of HIF-1␣ protein expression, which is controlled by p42/p44 MAPK activity and H 2 O 2 . The ability of EBV, and specifically its major oncoprotein, LMP1, to induce HIF-1␣ along with other invasiveness and angiogenic factors reported previously discloses additional oncogenic properties of this tumor virus.

Cyclooxygenase-2 (COX-2) is an inducible form of COX and is overexpressed in diverse tumors, raising the possibility of a role for COX-2 in carcinogenesis. In addition, COX-2 contributes to angiogenesis. The Epstein–Barr virus (EBV) oncoprotein, latent membrane protein 1 (LMP1), is detected in at least 70% of nasopharyngeal carcinoma (NPC) and all EBV-infected preinvasive nasopharyngeal lesions. We found that in specimens of LMP1-positive NPC, COX-2 is frequently expressed, whereas LMP1-negative NPC rarely express the enzyme. We next found that expression of LMP1 in EBV-negative nasopharyngeal epithelial cells induced COX-2 expression. Coexpression of IκBα(S32A/S36A), which is not phosphorylated and prevents NF-κB activation, with LMP1 showed that NF-κB is essential for induction of COX-2 by LMP1. We also demonstrate that NF-κB is involved in LMP1-induced cox-2 promoter activity with the use of reporter assays. Two major regions of LMP1, designated CTAR1 and CTAR2, are signal-transducing domains of LMP1. Constructs expressing either CTAR1 or CTAR2 induce COX-2 but to a lesser extent than wild-type LMP1, consistent with the ability of both regions to activate NF-κB. Furthermore, we demonstrate that LMP1-induced COX-2 is functional because LMP1 increased production of prostaglandin E 2 in a COX-2-dependent manner. Finally, we demonstrate that LMP1 increased production of vascular endothelial growth factor (VEGF). Treatment of LMP1-expressing cells with the COX-2-specific inhibitor (NS-398) dramatically decreased production of VEGF, suggesting that LMP1-induced VEGF production is mediated, at least in part, by COX-2. These results suggest that COX-2 induction by LMP1 may play a role in angiogenesis in NPC.

ABSTRACT

Nasopharyngeal carcinoma (NPC), an EBV-associated malignancy, is highly metastatic compared with other head and neck tumors, perhaps because of its viral link. Here, we show that the principal EBV oncoprotein, latent membrane protein 1 (LMP1), induces epithelial-mesenchymal transition (EMT) via Twist, a master transcriptional regulator in embryogenesis and newly implicated in metastasis, which, in turn, are likely to contribute to the highly metastatic character of NPC. LMP1 could induce EMT and its associated cell motility and invasiveness in a cell culture model, whereas expression of Twist small interfering RNA reversed LMP1-induced EMT. In diverse EBV-infected cell lines, expression of Twist correlates with expression of LMP1. Dominant-negative LMP1 could suppress Twist expression in EBV-positive cells, whereas LMP1 could induce Twist in EBV-negative nasopharyngeal cells. LMP1 signals through the nuclear factor-KB pathway, and an IKB superrepressor inhibited induction of Twist by LMP1. Finally, in human NPC tissues, expression of Twist and LMP1 is directly correlated and expression of Twist is associated with metastasis clinically. These results suggest that induction of Twist by a human viral oncoprotein LMP1 directly contributes to the metastatic nature of NPC. [Cancer Res 2007;67(5):1970-8]

Background:Epstein-Barr Virus (EBV)-associated nasopharyngeal carcinoma (NPC) is distinctive among head-and-neck cancers in its undifferentiated histopathology and highly metastatic character. We have recently investigated the involvement of epithelial–mesenchymal transition (EMT) in NPC. In a previous study, we found a close association of expression of LMP1, the principal EBV oncoprotein, with expression of Twist and induction of EMT.Methods:We analysed expression of Snail in 41 NPC tissues by immunohistochemistry. The role of Twist as well as Snail in EMT of NPC was investigated by using NP69SV40T human nasopharyngeal cells.Results:In NPC tissues, overexpression of Snail is associated with expression of LMP1 in carcinomatous cells. In addition, expression of Snail positively correlated with metastasis and independently correlated inversely with expression of E-cadherin. Expression of Twist had no association with expression of E-cadherin. Further, in a human nasopharyngeal cell line, LMP1 induces EMT and its associated cellular motility and invasiveness. Expression of Snail is induced by LMP1 in these cells, and small hairpin RNA (shRNA) to Snail reversed the cellular changes. By contrast, Twist did not produce EMT in these nasopharyngeal cells.Conclusions:This study strengthens the association of EMT with the metastatic behaviour of NPC. These results suggest that induction of Snail by the EBV oncoprotein LMP1 has a pivotal role in EMT in NPC.

Hypoxia-inducible factor 1 (HIF1) is up-regulated in most malignant tumors usually via interruption of ubiquitination and proteasomal degradation of its subunit A. Recently, we have shown that the principal EBV oncoprotein, latent membrane protein 1 (LMP1), activates HIF1A and subsequently expression of HIF1-responsive genes in epithelial cells. Here, we explore the mechanism for HIF1A activation by LMP1 in nasopharyngeal epithelial cells: LMP1 up-regulates the level of Siah1 E3 ubiquitin ligase by enhancing its stability, which subsequently induces proteasomal degradation of prolyl HIF-hydroxylases 1 and 3 that normally mark HIF1A for degradation. As a result, LMP1 prevents formation of von Hippel-Lindau/HIF1A complex, as shown by coimmunoprecipitation analyses. Thus, Siah1 is implicated in the regulation of HIF1A and is involved in a recently appreciated aspect of EBV-mediated tumorigenesis, namely, the angiogenesis process triggered by LMP1. (Cancer Res 2006; 66(20): 9870-7)