Nasopharyngeal Cell Line Research Articles

Promoter Methylation of Dual Specificity Phosphatase-6 Gene effect on Invasion and Metastasis of Nasopharyngeal Carcinoma

Objective: The dual-specificity phosphatase-6 (DUSP-6) is a member of dual-specificity protein phosphatase (DUSP) family, it can make residues of threonine and tyrosine dephosphorylate. In recent years, it was found that DUSP-6 is correlated with tumour generation and progress. In this study we have detected the effect of DUSP-6 gene methylation on invasion and metastasis of nasopharyngeal carcinoma. Methods: RT-PCR and methylation-specific PCR are used to detect mRNA expression and methylation state of DUSP-6 gene in nasopharyngeal carcinoma tissues and CNE2 cell line. The changes of mRNA expression and methylation state of DUSP-6 gene, proliferation and invasion of cells were detected after 5-aza- 2’-deoxycytidine (5-aza-cdR) treated CNE2 cell line. Results: These results showed that DUSP-6 gene expression is related to its promoter methylation state, cervical lymph node metastasis is related to DUSP-6 gene promoter methylation state in patients with nasopharyngeal carcinoma, 5-aza-cdR can inhibit invasion of CNE2 cells, and make re-expression of DUSP-6 gene by promoter demethylation in CNE2 cells. Conclusion: DUSP-6 gene promoter methylation state is possibly an important factor that effected invasion and metastasis of nasopharyngeal carcinoma. DUSP-6 gene may make a novel marker for prognostic evaluation in nasopharyngeal carcinoma.

Extracellular serglycin upregulates the CD44 receptor in an autocrine manner to maintain self-renewal in nasopharyngeal carcinoma cells by reciprocally activating the MAPK/β-catenin axis.

Serglycin is a proteoglycan that was first found to be secreted by hematopoietic cells. As an extracellular matrix (ECM) component, serglycin promotes nasopharyngeal carcinoma (NPC) metastasis and serves as an independent, unfavorable NPC prognostic indicator. The detailed mechanism underlying the roles of serglycin in cancer progression remains to be clarified. Here, we report that serglycin knockdown in NPC cells inhibited cell sphere formation and tumor seeding abilities. Serglycin downregulation enhanced high-metastasis NPC cell sensitivity to chemotherapy. It has been reported that serglycin is a novel ligand for the stem cell marker CD44. Interestingly, we found a positive correlation between serglycin expression and CD44 in nasopharyngeal tissues and NPC cell lines. Further study revealed that CD44 was an ERK-dependent downstream effector of serglycin signaling, and serglycin activated the MAPK/β-catenin axis to induce CD44 receptor expression in a positive feedback loop. Taken together, our novel findings suggest that ECM serglycin upregulated CD44 receptor expression to maintain NPC stemness by interacting with CD44 and activating the MAPK/β-catenin pathway, resulting in NPC cell chemoresistance. These findings suggest that the intervention of serglycin/CD44 axis and downstream signaling pathway is a rational strategy for targeting NPC cancer stem cell therapy.

KAI1 overexpression promotes apoptosis and inhibits proliferation, cell cycle, migration, and invasion in nasopharyngeal carcinoma cells

ObjectivesThe purpose of this study is to characterize the effect of KAI1 overexpression on the biological behavior of nasopharyngeal carcinoma (NPC) cells. BackgroundNasopharyngeal carcinoma is a highly malignant tumor with a high rate of incidence in China. Currently, there are no ideal therapeutic options for patients with NPC, but a targeted therapy would have great potential for treating it. Therefore, there is an urgent need for novel therapeutic targets to provide new options for treating NPC. The KAI1 gene was originally identified as a metastasis suppressor gene for advanced human cancer. In NPC cell lines and tissues, the expression of KAI1 decreased as the metastatic potential of cells increased, but its potential as a therapeutic target has not been elucidated. MethodsNon-transformed nasopharyngeal epithelium cell NP69 and NPC cell line C666-1 were cultured and KAI1 expression in these cells was detected by qRT-PCR and Western blot. After the transfection of KAI1-pCDNA3.1 to NP69 and C666-1, the KAI1 expression in these cells was detected by qRT-PCR and Western blot, the proliferation was performed by MTS, the cell cycle and apoptosis were performed by flow cytometry, the migration and invasion were examined by transwell. ResultsOur results showed that KAI1 was significantly upregulated in C666-1 cells compared to that in NP69 cells. In addition, KAI1 overexpression significantly inhibited the proliferation, cell cycle, migration, and invasion, and promoted apoptosis of C666-1 cells, but had no significant effect on NP69 cells. ConclusionOur findings suggest that KAI1 overexpression promotes apoptosis and inhibits proliferation, cell cycle, migration, and invasion in NPC cells. We hypothesize that KAI1 overexpression could be a potential therapeutic target for NPC.

Abstract 5038: The repression of the extracellular matrix protein TGFBI induces chemoresistance in nasopharyngeal carcinoma

Abstract Introduction: Nasopharyngeal carcinoma (NPC) is a malignancy that is strongly associated with Epstein-Barr virus (EBV). The five-year overall survival (OS) rate of locally-advanced NPC patients is ∼65%. Therapeutic options for such patients are limited; ionizing radiation is the primary mode of therapy for early-stage NPC, while chemoradiotherapy is used for more advanced stages. The use of chemotherapy (combined with radiation) provides a modest benefit in OS, but causes significant toxicities. The major cause of death in NPC is distant metastasis (DM), which remains a clinical challenge. In order to identify novel mechanisms underlying this process, our laboratory has recently completed global RNA sequencing of NPC samples which were fully clinically annotated. The extracellular matrix protein TGFBI (Transforming Growth Factor, Beta-Induced) was identified as a potential marker for chemoresistance. The objective of this study was to elucidate the role of TGFBI, and acquire greater insight into the biological pathways leading to chemoresistance and contributing to DM in NPC. Methods: Nasopharyngeal cell lines including NP69 (normal nasopharyngeal, SV-40 immortalized), and C666-1 (NPC, EBV positive) were used to assess the differential expression of TGFBI between normal and malignant cells. TGFBI under-expressing NP69 cells were engineered using shRNA vectors, and the impact of the loss of TGFBI expression was assessed by cell death, clonogenic, and migration assays. Downstream target gene expression was evaluated by quantitative real-time PCR (qRT-PCR) and Western blot. C666-1 cells, which had no expression of TGFBI (RNA or protein), were used as controls. Results: RNA-seq data identified poorer distant relapse-free survival in chemoradiotherapy-treated patients with low TGFBI expression vs. those with high TGFBI expression. In concordance with this observation, in vitro down-regulation of TGFBI induced cisplatin resistance via the phosphorylation of Akt and PTEN. TGFBI downregulation also increased cellular migration in spheroid cultures. Furthermore, TGFBI was identified to be a target of miR-449b, one of the 4 microRNAs in a DM prognostic signature that was previously identified by our group (Oncotarget 6:4537, 2015). In turn, over-expression of miR-449b in nasopharyngeal cells increased phospho-Akt expression, phenocopying the results observed in the TGFBI experiments. Conclusion: Together, these data suggest that the miR-449∼TGFBI-Akt axis plays a significant role in both treatment resistance and metastasis in NPC. Further studies will allow us to elucidate additional components of this pathway, and identify novel therapeutic targets which can benefit future patients with NPC. Citation Format: Pierre-Antoine Bissey, Jeff W. Bruce, Jacqueline Law, Kenneth W. Yip, Fei-Fei Liu. The repression of the extracellular matrix protein TGFBI induces chemoresistance in nasopharyngeal carcinoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5038.

In vitro cytotoxic activity of isolated compounds from Malaysian Calophyllum species

Cancer is a leading cause of death worldwide. In our continuing search for new anticancer agents, four Malaysian Calophyllum species, namely C. castaneum, C. teysmannii, C. canum, and C. sclerophyllum, had been phytochemically studied to give compounds 1–12. All the isolated compounds were evaluated for their antiproliferative activity against nasopharyngeal (SUNE1, TW01, CNE1, HK1) and breast (HCC38, MDA-MB-231, MDA-MB-468, SKBR3) cancer cell lines via methyl thiazolyl tetrazolium cell viability assay. Among the tested compounds, isodispar B (1) showed a promising dose-dependent and a broad spectrum of cytotoxic effects on all the tested cancer cell lines; in particular, potent inhibitory activities were observed on nasopharyngeal cancer cell lines (SUNE1, TW01, CNE1, HK1), with IC50 values ranging from 3.8 to 11.5 µM. In comparison with 5-fluorouracil as positive control, compound 1 was found to exhibit at least sixfold much higher activity than the standard drug used against the nasopharyngeal cell lines. Compound 1 was later found to induce apoptotic cell death in nasopharyngeal cancer cells, as evidenced by ‘Cell Death Detection’ ELISAPLUS kit, and exhibited good cancer-specific cytotoxicity when tested with noncancerous NP460 cells. Meanwhile, compounds 2–12 displayed moderate to weak activities against the tested cancer cell lines. The findings have highlighted the therapeutic potential of compound 1 against nasopharyngeal cancer.

EZH2 suppresses the nucleotide excision repair in nasopharyngeal carcinoma by silencing XPA gene

The enhancer of zeste homolog 2 (EZH2) is involved in a number of fundamental pathological processes of cancer. However, its role in DNA repair pathway is still unclear. Here, we have identified XPA as a novel target gene of EZH2 via a DNA repair pathway PCR array. XPA plays a pivot role in nucleotide excision repair (NER). The expression of XPA was significantly increased by EZH2 specific inhibitor GSK126 or lentiviral shEZH2 in nasopharyngeal carcinoma (NPC) CNE and 8F cell lines. Chromatin immunoprecipitation assay demonstrated that EZH2 catalyzes H3K27 trimethylation at the XPA promoters. Furthermore, we validated the negative correlation of EZH2 and XPA in a NPC tissue microarray by immunohistochemistry staining. We also found that high expression of EZH2 was positively correlated with advanced T, N, and AJCC stage of NPC; and low expression of XPA was positively correlated with advanced T and N stage. In NPC cell lines, increased XPA expression by EZH2 inhibition resulted in a more rapid removal of UVC induced 6-4PP- and CPD-DNA adducts, as well as enhanced efficiency of DNA repair after UVC irradiation as detected by the Comet assay and immunofluorescence staining of γH2Ax. Consistently, increased cell clonogenic survival, decreased apoptosis, and necrosis after UVC irradiation, and increased resistance to DNA damaging agent cisplatin was also observed in EZH2 inhibited cells. These results illustrate that EZH2 may promote carcinogenesis and cancer development of NPC by transcriptional repression of XPA gene and inactivation of NER pathway. © 2016 Wiley Periodicals, Inc.

Synthesis and anticancer activity of some 5-fluoro-2′-deoxyuridine phosphoramidates

Two series of novel 4-chlorophenyl N-alkyl phosphoramidates of 3′-O-(t-butoxycarbonyl)-5-fluoro-2′-deoxyuridine (3′-BOC-FdU) (9a–9j) and 5-fluoro-2′-deoxyuridine (FdU) (10a–10j) were synthesized by means of phosphorylation of 3′-BOC-FdU (4) with 4-chlorophenyl phosphoroditriazolide (7), followed by a reaction with the appropriate amine. Phosphoramidates 9a–9j were converted to the corresponding 10a–10j by removal of the 3′-t-butoxycarbonyl protecting group (BOC) under acidic conditions. The synthesized phosphoramidates 9a–9j and 10a–10j were evaluated for their cytotoxic activity in five human cancer cell lines: cervical (HeLa), nasopharyngeal (KB), breast (MCF-7), liver (HepG2), osteosarcoma (143B) and normal human dermal fibroblast cell line (HDF) using the sulforhodamine B (SRB) assay. Two phosphoramidates 9b and 9j with the N-ethyl and N-(methoxy-(S)-alaninyl) substituents, respectively, displayed remarkable activity in all the investigated cancer cells, and the activity was considerably higher than that of the parent nucleoside 4 and FdU. Among phosphoramidates 10a–10j compound 10c with the N-(2,2,2-trifluoroethyl) substituent showed the highest activity. Phosphoramidate 10c was more active than the FdU in all the cancer cell lines tested.

Angiotensin-(1-7) Decreases Cell Growth and Angiogenesis of Human Nasopharyngeal Carcinoma Xenografts.

Angiotensin-(1-7) [Ang-(1-7)] is an endogenous, heptapeptide hormone acting through the Mas receptor (MasR), with antiproliferative and antiangiogenic properties. Recent studies have shown that Ang-(1-7) has an antiproliferative action on lung adenocarcinoma cells and prostate cancer cells. In this study, we report that MasR levels were significantly upregulated in nasopharyngeal carcinoma (NPC) specimens and NPC cell lines. Viral vector-mediated expression of Ang-(1-7) dramatically suppressed NPC cell proliferation and migration in vitro. These effects were completely blocked by the specific Ang-(1-7) receptor antagonist A-779, suggesting that they are mediated by the Ang-(1-7) receptor Mas. In this study, Ang-(1-7) not only caused a significant reduction in the growth of human nasopharyngeal xenografts, but also markedly decreased vessel density, suggesting that the heptapeptide inhibits angiogenesis to reduce tumor size. Mechanistic investigations revealed that Ang-(1-7) inhibited the expression of the proangiogenic factors VEGF and PlGF. Taken together, the data suggest that upregulation of MasR could be used as a diagnostic marker of NPC and Ang-(1-7) may be a novel therapeutic agent for nasopharyngeal cancer therapy because it exerts significant antiangiogenic activity.

Lectin from green speckled lentil seeds (Lens culinaris) triggered apoptosis in nasopharyngeal carcinoma cell lines.

BackgroundThe green speckled lentil seed (Lens culinaris) lectin (GSLL) exhibits hemagglutinating activity, and possesses some properties distinct from those of other lentil lectins (e.g., molecular size, biological activities) that deserve further investigation. This study aims to investigate the basic properties (e.g., molecular size, amino acid sequence, sugar specificity) and biological activities (e.g., antiproliferative activity) of GSLL.MethodsGSLL was purified by successive fractionation on SP-Sepharose, Affi-gel blue gel, Mono Q, and Superdex 75. The biochemical properties of GSLL were investigated by SDS-PAGE, mass spectrometry, N-terminal amino acid sequencing, and sugar inhibition tests. For the biological activities, purified lyophilized GSLL was sterilized, adjusted to concentrations from 1 to 0 mg/mL (by twofold serial dilution) in Dulbecco’s modified Eagle’s medium with fetal bovine serum, and examined by using the MTT assay, flow cytometry, and western blotting after treatment of nasopharyngeal carcinoma CNE1 and CNE2 cell lines with the lectin.ResultsGSLL appeared as a 21-kDa band in non-reducing SDS-PAGE. It was composed of two subunits with molecular sizes of 17 and ~4 kDa. It exhibited specificity in binding to glucose and mannose, as well as glucosides and mannosides. Mass spectrometry and N-terminal amino acid sequencing revealed similarity of GSLL to L. culinaris lectin (LcL), especially higher coverage of the β-chain of LcL. A 48-h treatment with GSLL exerted antiproliferative effects on nasopharyngeal carcinoma CNE1 and CNE2 cell lines with significant inhibition at 0.125 mg/mL (P < 0.001) and 1 mg/mL (P = 0.004), respectively, and these effects were attenuated in the presence of glucose and mannose. GSLL induced apoptosis in nasopharyngeal carcinoma CNE1 cells, with detectable phosphatidylserine externalization, mitochondrial depolarization, and cell cycle arrest. Western blot analysis suggested that GSLL triggered the extrinsic apoptotic pathway involving caspase 3, 8, and 9 in CNE1 cells.ConclusionGSLL possessed some different properties from LcL (e.g., lower pI), and increased caspase 3, 8, and 9 activity in CNE1 cells.

Protocadherin20 Acts as a Tumor Suppressor Gene: Epigenetic Inactivation in Nasopharyngeal Carcinoma.

Genetic alterations of 13q21 (PCDH 8,9,17, and 20) are frequently observed in multiple tumors, suggesting the presence of critical tumor suppressor genes (TSGs). Protocadherin20 (PCDH20), located at 13q21.2, belongs to the δ1-protocadherins, which constitutes one of the largest subgroup within the adherin superfamily. Frequent downregulation/silencing of PCDH20 was found in NPC cell lines using semiquantitative PCR. PCDH20 mRNA was broadly expressed in normal nasopharyngeal tissues and cell lines. Promoter methylation of PCDH20 was observed in 80% (4/5) of NPC cell lines and 78.4% (40 of 51) of primary tumors by methylation-specific PCR, but rarely in normal nasopharygeal tissues and nasopharyngeal epithelial cell line (NP69). The silencing of PCDH20 can be reversed by pharmacological demethylation, indicating an epigenetic mechanism. Restoration of PCDH20 expression in NPC cells strongly suppressed cell numbers and colony formation. Overexpression of PCDH20 antagonized Wnt/β-catenin signaling pathway and promoted β-catenin to translocate from nucleus to cytoplasm and membrane. PCDH20 significantly inhibited the migration and invasion ability of NPC cells. PCDH20 also inhibited epithelial-mesenchymal transition (EMT) through enhanced expression of E-cadherin. Our study identified PCDH20 as a functional tumor suppressor and an important antagonist of Wnt/β-catenin signaling and EMT, with frequent epigenetic inactivation in NPC.

ZNF488 Enhances the Invasion and Tumorigenesis in Nasopharyngeal Carcinoma Via the Wnt Signaling Pathway Involving Epithelial Mesenchymal Transition.

PurposeThe purpose of this study was to investigate the function of Zinc finger protein 488 (ZNF488) in nasopharyngeal carcinoma (NPC).Materials and MethodsThe endogenous expression of ZNF488 in NPC tissues, normal nasopharyngeal epithelium tissues and NPC cell lines were detected by quantitative reverse transcription polymerase chain reaction. ZNF488 over-expressing and knock-down NPC cell line models were established through retroviral vector pMSCV mediated over-expression and small interfering RNA (siRNA) mediated knock-down. The invasion and migration capacities were evaluated by wound healing and transwell invasion assays in ZNF488 over-expressing and control cell lines. Soft-agar colony formation and a xenograft experiment were performed to study tumorigenic ability in vitro and in vivo. Immunofluorescence and western blotting analysis were used to examine protein changes followed by ZNF488 over-expression. Microarray analysis was performed to explore gene expression profilings, while luciferase reporter assay to evaluate the transcriptive activity of Tcf/Lef.ResultsZNF488 was over-expressed in NPC tissues compared with normal tissues, especially higher in 5-8F and S18, which are well-established high metastatic NPC clones. Functional studies indicate that over-expression of ZNF488 provokes invasion, whereas knock-down of ZNF488 alleviates invasive capability. Moreover, over-expression of ZNF488 promotes NPC tumor growth both in vitro and in vivo. Our data further show that over-expression of ZNF488 induces epithelial mesenchymal transition (EMT) by activating the WNT/β-catenin signaling pathway.ConclusionOur data strongly suggest that ZNF488 acts as an oncogene, promoting invasion and tumorigenesis by activating the Wnt/β-catenin pathway to induce EMT in NPC.

EGCG inhibits proliferation, invasiveness and tumor growth by up-regulation of adhesion molecules, suppression of gelatinases activity, and induction of apoptosis in nasopharyngeal carcinoma cells.

(−)-Epigallocatechin-3-gallate (EGCG), a major green tea polyphenol, has been shown to inhibit the proliferation of a variety of tumor cells. Epidemiological studies have shown that drinking green tea can reduce the incidence of nasopharyngeal carcinoma (NPC), yet the underlying mechanism is not well understood. In this study, the inhibitory effect of EGCG was tested on a set of Epstein Barr virus-negative and -positive NPC cell lines. Treatment with EGCG inhibited the proliferation of NPC cells but did not affect the growth of a non-malignant nasopharyngeal cell line, NP460hTert. Moreover, EGCG treated cells had reduced migration and invasive properties. The expression of the cell adhesion molecules E-cadherin and β-catenin was found to be up-regulated by EGCG treatment, while the down-regulation of matrix metalloproteinases (MMP)-2 and MMP-9 were found to be mediated by suppression of extracellular signal-regulated kinase (ERK) phosphorylation and AP-1 and Sp1 transactivation. Spheroid formation by NPC cells in suspension was significantly inhibited by EGCG. Oral administration of EGCG was capable of suppressing tumor growth in xenografted mice bearing NPC tumors. Treatment with EGCG was found to elevate the expression of p53 and p21, and eventually led to apoptosis of NPC cells via caspase 3 activation. The nuclear translocation of NF-κB and β-catenin was also suppressed by EGCG treatment. These results indicate that EGCG can inhibit the proliferation and invasiveness, and induce apoptosis, of NPC cells, making it a promising agent for chemoprevention or adjuvant therapy of NPC.

Ultrasound-mediated method for rapid delivery of nano-particles into cells for intracellular surface-enhanced Raman spectroscopy and cancer cell screening

Surface-enhanced Raman spectroscopy (SERS) is a powerful technology for providing finger-printing information of cells. A big challenge has been the long time duration and inefficient uptake of metal nano-particles into living cells as substrate for SERS analysis. Herein, a simple method (based on ultrasound) for the rapid transfer of silver nanoparticles (NPs) into living cells for intracellular SERS spectroscopy was presented. In this study, the ultrasound-mediated method for NP delivery overcame the shortcoming of ‘passive uptake’, and achieved quick acquisition of reproducible SERS spectra from living human nasopharyngeal carcinoma cell lines (C666 and CNE1) and normal nasopharyngeal cell line (NP69). Tentative assignment of the Raman bands in the measured SERS spectra showed cancer cell specific biomolecular differences, including significantly lower DNA concentrations and higher protein concentrations in cancerous nasopharyngeal cells as compared to those of normal cells. Combined with PCA–LDA multivariate analysis, ultrasound-mediated cell SERS spectroscopy differentiated the cancerous cells from the normal nasopharyngeal cells with high diagnostic accuracy (98.7%), demonstrating great potential for high-throughput cancer cell screening applications.

Identification and analysis of the promoter region of the STGC3 gene.

IntroductionNasopharyngeal carcinoma (NPC) is a common malignant tumor of the head and neck. The STGC3 gene is related to development of nasopharyngeal cancer. The aim of this study is to explore the promoter region of the STGC3 gene.Material and methodsThe bioinformatic technique was applied to predict its promoter region and construct the gene promoter region luciferase for the gene vector and transfection of the human embryonic kidney epithelial 293T cell line, human nasopharyngeal carcinoma CNE2 cell line and immortalized nasopharyngeal epithelial NP69 cell line. The recombinant plasmid pGL3-en283, pGL3-en281, pGL3-en571, empty plasmid pGL3-control, negative control pGL3-enhance and internal control of marine intestine luciferase expression vector pRL-SV40 were transfected into NP69 cells, 293T cells and CNE2 cells. Dual luciferase activity detection showed luciferase luminescence values and marine intestine luciferase luminescence values. Relative luciferase activity (RLA) in each cell was calculated.ResultsWe observed strong promoter activity of plasmid pGL3-en283, pGL3-en281 and pGL3-en571 in NP69, 293T and CNE2 cells compared with the negative control pGL3-enhance plasmid. Among them, pGL3-en281 showed the strongest promoter activity, and these three kinds of recombinant plasmids showed stronger promoter activity in 293T cells than in CNE2 cells.ConclusionsThe pGL3-en281 plasmid showed stronger promoter activity than pGL3-en571 in the three cells, indicating that –11048 bp to –653 bp might be the core promoter region.

LMP1 promotes expression of insulin-like growth factor 1 (IGF1) to selectively activate IGF1 receptor and drive cell proliferation.

Epstein-Barr Virus (EBV) is a gammaherpesvirus that infects the majority of the human population and is linked to the development of multiple cancers, including nasopharyngeal carcinoma. Latent membrane protein 1 (LMP1) is considered the primary oncoprotein of EBV, and in epithelial cells it induces the expression and activation, or phosphorylation, of the epidermal growth factor receptor kinase. To identify effects on additional kinases, an unbiased screen of receptor tyrosine kinases potentially activated by LMP1 was performed. Using a protein array, it was determined that LMP1 selectively activates insulin-like growth factor 1 receptor (IGF1R). This activation takes place in fibroblast, epithelial, and nasopharyngeal cell lines that express LMP1 stably and transiently. Of note, LMP1 altered the phosphorylation, but not the expression, of IGF1R. The use of LMP1 mutants with defective signaling domains revealed that the C-terminal activating region 2 domain of LMP1 increased the mRNA expression and the secretion of the ligand IGF1, which promoted phosphorylation of IGF1R. IGF1R phosphorylation was dependent upon activation of canonical NF-κB signaling and was suppressed by IκBα and a dominant negative form of TRAF6. Inhibition of IGF1R activation with two small-molecule inhibitors, AG1024 and picropodophyllin (PPP), or with short hairpin RNA (shRNA) directed against IGF1R selectively reduced proliferation, focus formation, and Akt activation in LMP1-positive cells but did not impair LMP1-induced cell migration. Expression of constitutively active Akt rescued cell proliferation in the presence of IGF1R inhibitors. These findings suggest that LMP1-mediated activation of IGF1R contributes to the ability of LMP1 to transform epithelial cells. EBV is linked to the development of multiple cancers in both lymphoid and epithelial cells, including nasopharyngeal carcinoma. Nasopharyngeal carcinoma is a major cancer that develops in specific populations, with nearly 80,000 new cases reported annually. LMP1 is consistently expressed in early lesions and continues to be detected within 50 to 80% of these cancers at later stages. It is therefore of paramount importance to understand the mechanisms through which LMP1 alters cell growth and contributes to tumorigenesis. This study is the first to determine that LMP1 activates the IGF1R tyrosine kinase by regulating expression of the ligand IGF1. Additionally, the data in this paper reveal that specific targeting of IGF1R selectively impacts LMP1-positive cells. These findings suggest that therapies directed against IGF1R may specifically impair the growth of EBV-infected cells.

NGX6a Is Degraded through a Proteasome-dependent Pathway without Ubiquitination Mediated by Ezrin, a Cytoskeleton-Membrane Linker

Our previous study demonstrated that the NGX6b gene acts as a suppressor in the invasion and migration of nasopharyngeal carcinoma (NPC). Recently, we identified the novel isoform NGX6a, which is longer than NGX6b. In this study, we first found that NGX6a was degraded in NPC cells and that this degradation was mediated by ezrin, a linker between membrane proteins and the cytoskeleton. Specific siRNAs against ezrin increase the protein level of NGX6a in these cells. During degradation, NGX6a is not ubiquitinated but is degraded through a proteasome-dependent pathway. The distribution pattern of ezrin was negatively associated with NGX6a in an immunochemistry analysis of a nasopharyngeal carcinoma tissue microarray and fetus multiple organ tissues and Western blot analysis in nasopharyngeal and NPC cell lines, suggesting that ezrin and NGX6a are associated and are involved in the progression and invasion of NPC. By mapping the interacting binding sites, the seven-transmembrane domain of NGX6a was found to be the critical region for the degradation of NGX6a, and the amino terminus of ezrin is required for the induction of NGX6a degradation. The knockdown of ezrin or transfection of the NGX6a mutant CO, which has an EGF-like domain and a transmembrane 1 domain, resulted in no degradation, significantly reducing the ability of invasion and migration of NPC cells. This study provides a novel molecular mechanism for the low expression of NGX6a in NPC cells and an important molecular event in the process of invasion and metastasis of nasopharyngeal carcinoma cells.

Inhibition of protein phosphatase 2A with a small molecule LB100 radiosensitizes nasopharyngeal carcinoma xenografts by inducing mitotic catastrophe and blocking DNA damage repair.

Nasopharyngeal carcinoma (NPC), while uncommon worldwide, is a major health problem in China. Although local radiation and surgery provide good control of NPC, better treatments that permit reductions in radiation dosing are needed. Inhibition of protein phosphatase 2A (PP2A), a ubiquitous multifunctional enzyme with critical roles in cell cycle regulation and DNA-damage response, reportedly sensitizes cancer cells to radiation and chemotherapy. We studied PP2A inhibition with LB100, a small molecule currently in a Phase I clinical trial, on radiosensitization of two human nasopharyngeal cell lines: CNE1, which is reportedly radioresistant, and CNE2. In both cell lines, LB100 exposure increased intracellular p-Plk1, TCTP, and Cdk1 and decreased p53, changes associated with cell cycle arrest, mitotic catastrophe and radio-inhibition of cell proliferation. Mice bearing subcutaneous xenografts of either cell line were administered 1.5 mg/kg LB100 daily for three days and a single dose of 20 Gy radiation (day 3), which produced marked and prolonged tumor mass regression (dose enhancement factors of 2.98 and 2.27 for CNE1 and CNE2 xenografts, respectively). Treatment with either LB100 or radiation alone only transiently inhibited xenograft growth. Our results support further exploration of PP2A inhibition as part of radiotherapy regimens for NPC and potentially other solid tumors.

EMP1 inhibits nasopharyngeal cancer cell growth and metastasis through induction apoptosis and angiogenesis

This study aimed to analyze the expression, clinical significance of epithelial membrane protein-1 (EMP1) in nasopharyngeal carcinoma, and the biological effect in its cell line by EMP1 overexpression. Immunohistochemistry and Western blot were used to analyze the EMP1 protein expression in 75 cases of nasopharyngeal cancer and 31 cases of normal tissues to study the relationship between EMP1 expression and clinical factors. Recombinant lentiviral vector was constructed to overexpress EMP1 and then infect nasopharyngeal cancer CNE2 cell line. Quantitative real-time RT-PCR and Western blot were used to detect the mRNA level and protein of EMP1. MTT assay, cell apoptosis, migration, and invasion assays were also conducted to determine the influence of the upregulated expression of EMP1 that might be found on CNE2 cells' biological effect. Immunohistochemistry and Western blot: The level of EMP1 protein expression was found to be significantly lower in nasopharyngeal cancer tissue than in the normal tissues (P < 0.05). Decreased expression of EMP1 was significantly correlated with T stages, lymph node metastasis, clinic stage, and histological grade of patients with nasopharyngeal cancer (P < 0.05). Meanwhile, the loss of EMP1 expression correlated significantly with poor overall survival time by Kaplan-Meier analysis (P < 0.05). The result of biological function has shown that CNE2 cell-transfected EMP1 had a lower survival fraction, higher cell apoptosis, significant decrease in migration and invasion, higher caspase-9, and lower vascular endothelial growth factor C protein expression compared with CNE2 cell-untransfected EMP1 (P < 0.05). EMP1 expression decreased in nasopharyngeal cancer and correlated significantly T stages, lymph node metastasis, clinic stage, histological grade, and poor overall survival, suggesting that EMP1 may play important roles as a negative regulator to nasopharyngeal cancer cell.

Clinical significance of TrkB expression in nasopharyngeal carcinoma

Recent research has demonstrated that tropomyosin‑related kinase B (TrkB) plays an important role in neuronal survival, differentiation and migration; yet, its specific role in human nasopharyngeal carcinoma (NPC) is unclear. To elucidate its role in NPC, we examined TrkB expression in NPC tissues and cell lines, and investigated the correlation between TrkB expression and prognosis in patients with NPC. Immunohistochemical analysis was performed on NPC specimens from 108 patients with follow-up information. Additionally, reverse transcriptase-polymerase chain reaction (RT-PCR) and western blot analyses were used to determine TrkB expression levels in NPC and noncancerous nasopharyngeal tissues. RT-PCR and western blot analyses were also used to determine TrkB expression levels in 7 NPC cell lines and a nasopharyngeal epithelium cell line. High TrkB expression was significantly correlated with T classification, lymph node metastasis and clinical stage, respectively. Patients with NPC who had high TrkB expression had reduced disease-free survival and overall survival when compared with patients who had low TrkB expression. Multivariate Cox regression analysis revealed that TrkB overexpression was an independent prognostic factor for patients with NPC. Furthermore, TrkB was overexpressed in NPC specimens and cell lines. TrkB expression levels were significantly increased in NPC specimens, and enhanced levels were correlated with a poor prognosis in patients with NPC. These findings suggest that TrkB may contribute to NPC progression and represent a novel prognostic indicator for patients with NPC.

Absent expression of FLNA is correlated with poor prognosis of nasopharyngeal cancer

This study aimed to analyze the expression, clinical significance of filamin A (FLNA) in nasopharyngeal carcinoma, and the biological effect in its cell line by FLNA overexpression. Immunohistochemistry and western blot were used to analyze FLNA protein expression in 63 cases of nasopharyngeal cancer and 21 cases of normal tissues to study the relationship between FLNA expression and clinical factors. FLNA lentiviral vector and empty vector were respectively transfected into nasopharyngeal cancer CNE2 cell line. Reverse transcription-polymerase chain reaction (RT-PCR) and western blot were used to detect the mRNA level and protein of FLNA. 3-[4,5-Dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide, migration, and invasion assays were also conducted as to the influence of the upregulated expression of FLNA that might be found on CNE2 cell biological effect. Immunohistochemistry: the level of FLNA protein expression was found to be significantly lower in nasopharyngeal cancer tissue than normal tissues (P < 0.05). Western blot: the relative amount of FLNA protein in nasopharyngeal cancer tissue was found to be significantly lower than in normal tissues (P < 0.05). The level of FLNA protein expression was correlated with T stages, lymph node metastasis, clinic stage, and histological grade (P < 0.05). Loss of FLNA expression correlated significantly with poor overall survival time by Kaplan-Meier analysis (P < 0.05). The result of biological function has shown that CNE2 cell-transfected FLNA had a lower survival fraction, significant decrease in migration and invasion, and lower matrix metallopeptidase 9 (MMP-9) protein expression compared with CNE2 cell-untransfected FLNA (P < 0.05). FLNA expression decreased in nasopharyngeal cancer and correlated significantly lymph node metastasis, clinic stage, histological grade, and poor overall survival, suggesting that FLNA may play important roles as a negative regulator to nasopharyngeal cancer CNE2 cell by promoting degradation of MMP-9.