Chromosomal abnormalities of a new nasopharyngeal carcinoma cell line (NPC-BM1) derived from a bone marrow metastatic lesion

Nasopharyngeal Carcinoma Cell Lines: Reliable Alternatives to Primary Nasopharyngeal Cells?

Nasopharyngeal carcinoma (NPC) is a type of cancer that originates from the mucosal lining of the nasopharynx and can invade and spread. Although contemporary chemoradiotherapy effectively manages the disease locally, there are still challenges with locoregional recurrence and distant failure. Therefore, it is crucial to have a deeper understanding of the molecular basis of NPC cell movement in order to develop a more effective treatment and to improve patient survival rates. Cancer cell line models are invaluable in studying health and disease and it is not surprising that they play a critical role in NPC research. Consequently, scientists have established around 80 immortalized human NPC lines that are commonly used as in vitro models. However, over the years, it has been observed that many cell lines are misidentified or contaminated by other cells. This cross-contamination leads to the creation of false cell lines that no longer match the original donor. In this commentary, we discuss the impact of misidentified NPC cell lines on the scientific literature. We found 1159 articles from 2000 to 2023 that used NPC cell lines contaminated with HeLa cells. Alarmingly, the number of publications and citations using these contaminated cell lines continued to increase, even after information about the contamination was officially published. These articles were most commonly published in the fields of oncology, pharmacology, and experimental medicine research. These findings highlight the importance of science policy and support the need for journals to require authentication testing before publication.

Molecular Signature of Long Non-Coding RNA Associated with Areca Nut-Induced Head and Neck Cancer

The areca nut is a high-risk carcinogen for head and neck cancer (HNC) patients in Southeast Asia. The underlying molecular mechanism of areca nut-induced HNC remains unclear, especially regarding the role of long non-coding RNA (lncRNA). This study employed a systemic strategy to identify lncRNA signatures related to areca nut-induced HNC. In total, 84 cancer-related lncRNAs were identified. Using a PCR array method, 28 lncRNAs were identified as being dysregulated in HNC cells treated with areca nut (17 upregulated and 11 downregulated). Using bioinformatics analysis of The Cancer Genome Atlas Head-Neck Squamous Cell Carcinoma (TCGA-HNSC) dataset, 45 lncRNAs were differentially expressed in tumor tissues from HNC patients (39 over- and 6 under-expressions). The integrated evaluation showed 10 lncRNAs dysregulated by the areca nut and altered expression in patients, suggesting that these panel molecules participate in areca nut-induced HNC. Five oncogenic (LUCAT1, MIR31HG, UCA1, HIF1A-AS2, and SUMO1P3) and tumor-suppressive (LINC00312) lncRNAs were independently validated, and three key molecules were further examined. Pathway prediction revealed that LUCAT1, UCA1, and MIR31HG modulate multiple oncogenic mechanisms, including stress response and cellular motility. Clinical assessment showed that these lncRNAs exhibited biomarker potentials in diagnosis (area under the curve = 0.815 for LUCAT1) and a worse prognosis (both p < 0.05, survival analysis). Cellular studies further demonstrated that MIR31HG facilitates areca nut-induced cancer progression, as silencing this molecule attenuated arecoline-induced invasion ability in HNC cells. This study identified lncRNA signatures that play a role in areca nut-induced HNC. These molecules may be further applied in risk assessment, diagnosis, prognosis, and therapeutics for areca nut-associated malignancies.

EF-24, a Curcumin Analog, Inhibits Cancer Cell Invasion in Human Nasopharyngeal Carcinoma through Transcriptional Suppression of Matrix Metalloproteinase-9 Gene Expression

Cancer metastasis is a main cause of failure in treating subjects with nasopharyngeal carcinoma (NPC) and is frequently linked to high death rates. EF-24, an analog of curcumin, has exhibited many anti-cancer properties and enhanced bioavailability over curcumin. Nevertheless, the effects of EF-24 on the invasiveness of NPC are poorly understood. In this study, we demonstrated that EF-24 effectively inhibited TPA-induced motility and invasion responses of human NPC cells but elicited very limited cytotoxicity. In addition, the TPA-induced activity and expression of matrix metalloproteinase-9 (MMP-9), a crucial mediator of cancer dissemination, were found to be reduced in EF-24-treated cells. Our reporter assays revealed that such a reduction in MMP-9 expression by EF-24 was transcriptionally mediated by NF-κB via impeding its nuclear translocation. Further chromatin immunoprecipitation assays displayed that the EF-24 treatment decreased the TPA-induced interaction of NF-κB with the MMP-9 promoter in NPC cells. Moreover, EF-24 inhibited the activation of JNK in TPA-treated NPC cells, and the treatment of EF-24 together with a JNK inhibitor showed a synergistic effect on suppressing TPA-induced invasion responses and MMP-9 activities in NPC cells. Taken together, our data demonstrated that EF-24 restrained the invasiveness of NPC cells through the transcriptional suppression of MMP-9 gene expression, implicating the usefulness of curcumin or its analogs in controlling the spread of NPC.

Antipsychotic drug trifluoperazine as a potential therapeutic agent against nasopharyngeal carcinoma

BACKGROUND

Trifluoperazine (TFP) is a typical antipsychotic primarily used to treat schizophrenia. In this study, we aimed to evaluate whether TFP can be used as a therapeutic agent against nasopharyngeal carcinoma (NPC) and identify its underlying molecular mechanisms.

METHODS

We used NPC-TW01, TW03, TW04, and BM to assess the anticancer effects of TFP by using cytotoxicity, wound healing, colony formation, and cell invasion assays. An in vivo animal study was conducted. RNA sequencing combined with Ingenuity Pathways Analysis was performed to identify the mechanism by which TFP influences NPC cells.

RESULTS

Our data revealed that TFP decreased NPC cell viability in a dose-dependent manner. The invasion and migration of NPC tumor cells were inhibited by TFP. An in vivo study also demonstrated the anticancer effects of TFP. RNA sequencing revealed several anticancer molecular mechanisms following TFP administration.

CONCLUSIONS

The antipsychotic drug TFP could be a potential therapeutic regimen for NPC treatment.

Lipocalin 2 Reduces MET Levels by Inhibiting MEK/ERK Signaling to Inhibit Nasopharyngeal Carcinoma Cell Migration

Nasopharyngeal carcinoma (NPC) is the most common cancer that occurs in the nasopharynx, and it is difficult to detect early. The main cause of death of NPC patients is cancer metastasis. Lipocalin 2 (LCN2) has been shown to be involved in a variety of carcinogenesis processes. Here, we aimed to study the role of LCN2 in NPC cells and determine its underlying mechanism. We found that LCN2 was expressed differently in NPC cell lines, namely HONE-1, NPC-39, and NPC-BM. The down-regulation of LCN2 levels by siRNA targeting LCN2 (siLCN2) increased cell migration and invasion in HONE-1 cells, while the up-regulation of LCN2 levels by transfection with the LCN2 expression plasmid decreased cell migration and invasion in NPC-BM cells. Furthermore, LCN2 levels negatively regulated the phosphorylation of MEK/ERK pathways. The treatment of the specific MEK/ERK inhibitor, U0126, reduced cell migration in HONE-1 cells, whereas the treatment of tBHQ, an ERK activator, enhanced cell migration in NPC-BM cells. Based on the bioinformatics data, there was a moderately negative correlation between LCN2 and MET in metastatic NPC tissues (r = -0.5946, p = 0.0022). Indeed, the manipulation of LCN2 levels negatively regulated MET levels in these NPC cells. The treatment of U0126 reduced siLCN2-increased MET levels, while the treatment of tBHQ enhanced LCN2-enhanced MET levels. Interestingly, the down-regulation of MET levels by siMET further decreased siLCN2-enhanced MET levels and cell migration. Therefore, LCN2 inhibits NPC cell migration by reducing MET levels through MEK/ERK signaling.

Xanthohumol targets the JNK1/2 signaling pathway in apoptosis of human nasopharyngeal carcinoma cells

Nasopharyngeal carcinoma (NPC) is one of the most aggressive malignant tumors of the head and neck. Xanthohumol (Xn) is a compound extracted in a high concentration from the hard resin of hops (Humulus lupulus L.), the basic raw material of beer. This study investigated the apoptotic effect and anticancer properties of Xn in human NPC cell lines. Our study demonstrated that at the concentration 40 μM, Xn significantly reduced cell viability and promoted cell cycle arrest in the G2/M phase in two cell lines. The results indicated that Xn induced apoptosis in NPC cell lines through annexin V/propidium iodide staining, chromatin condensation, and apoptosis-related pathways. Xn upregulated the expression of apoptosis-related proteins, namely DR5, cleaved RIP, caspase-3, caspase-8, caspase-9, PARP, Bim, and Bak, and it downregulated the expression of Bcl-2. Xn upregulated the c-Jun N-terminal kinase (JNK) in the mitogen-activated protein kinase (MAPK), and the inhibition of JNK clearly resulted in decreasing expression of Xn-activated cleaved caspase-3 and PARP. Our research provides sufficient evidence to confirm that Xn induces the MAPK JNK pathway to promote apoptosis of NPC and is expected to become a safe and acceptable treatment option for human NPC.

Picrasidine I Triggers Heme Oxygenase-1-Induced Apoptosis in Nasopharyngeal Carcinoma Cells via ERK and Akt Signaling Pathways

Nasopharyngeal carcinoma (NPC) has a higher incidence in Taiwan than worldwide. Although it is a radiosensitive malignancy, cancer recurrence is still high in the advanced stages because of its ability to induce lymph node metastasis. Picrasidine I from Picrasma quassioides has been reported as a potential drug for targeting multiple signaling pathways. The present study aimed to explore the role of picrasidine I in the apoptosis of NPC cells. Our results show that picrasidine I induced cytotoxic effects in NPC cells and caused cell cycle arrest in the sub-G1, S, and G2/M phases. Western blot analysis further demonstrated that the modulation of apoptosis through the extrinsic and intrinsic pathways was involved in picrasidine I-induced cell death. Downregulation of the ERK1/2 and Akt signaling pathways was also found in picrasidine I-induced apoptosis. Additionally, the apoptosis array showed that picrasidine I significantly increased heme oxygenase-1 (HO-1) expression, which could act as a critical molecule in picrasidine I-induced apoptosis in NPC cells. The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) datasets also revealed that the HMOX1 mRNA level (HO-1) is lower in patients with head and neck squamous carcinoma (HNSCC) and NPC than in patients without cancer. Our study indicated that picrasidine I exerts anticancer effects in NPC by modulating HO-1 via the ERK and Akt signaling pathways.

Dehydrocrenatidine extracted from Picrasma quassioides induces the apoptosis of nasopharyngeal carcinoma cells through the JNK and ERK signaling pathways

Nasopharyngeal carcinoma (NPC) is an indicator disease in Asia due to its unique geographical and ethnic distribution. Dehydrocrenatidine (DC) is a β-carboline alkaloid abundantly present in Picrasma quassioides (D. Don) Benn, a deciduous shrub or small tree native to temperate regions of southern Asia, and β-carboline alkaloids play anti-inflammatory and antiproliferative roles in various cancers. However, the mechanism and function of DC in human NPC cells remain only partially explored. The present study aimed to examine the cytotoxicity and biochemical role of DC in human NPC cells. The MTT method, cell cycle analysis, DAPI determination, Annexin V/PI double staining, and mitochondrial membrane potential examination were performed to evaluate the effects of DC treatment on human NPC cell lines. In addition, western blotting analysis was used to explore the effect of DC on apoptosis and signaling pathways in related proteins. The analysis results confirmed that DC significantly reduced the viability of NPC cell lines in a dose- and time-dependent manner and induced apoptosis through internal and external apoptotic pathways (including cell cycle arrest, altered mitochondrial membrane potential, and activated death receptors). Western blot analysis illustrated that DC's effect on related proteins in the mitogen-activated protein kinase pathway can induce apoptosis by enhancing ERK phosphorylation and inhibiting Janus kinase (JNK) phosphorylation. Notably, DC induced apoptosis by affecting the phosphorylation of JNK and ERK, and DC and inhibitors (SP600125 and U0126) in combination restored the overexpression of p-JNK and p-ERK. To date, this is the first study to confirm the apoptosis pathway induced by DC phosphorylation of p-JNK and p-REK in human NPC. On the basis of evidence obtained from this study, DC targeting the inhibition of NPC cell lines may be a promising future strategy for NPC treatment.

Tricetin Suppresses Migration and Presenilin-1 Expression of Nasopharyngeal Carcinoma through Akt/GSK-3β Pathway

Lymph node migration results in poor prognoses for nasopharyngeal carcinoma (NPC) patients. Tricetin, a flavonoid derivative, regulates tumorigenesis activity through its antiproliferative and antimetastatic properties. However, the molecular mechanism of tricetin affecting the migration and invasion of NPC cells remains poorly understood. In this paper, we examined the antimetastatic properties of tricetin in human NPC cells. Our results demonstrated that tricetin at noncytotoxic concentrations (0-80 3M) noticeably reduced the migration and invasion of NPC cells (HONE-1, NPC-39, and NPC-BM). Moreover, tricetin suppressed the indicative protease, presenilin-1 (PS-1), as indicated by protease array. PS-1 was transcriptionally inhibited via the Akt signaling pathway but not mitogen-activated protein kinase pathways, such as the JNK, p38, and ERK1/2 pathways. In addition to upregulating GSK-3[Formula: see text] phosphorylation through Akt suppression, tricetin may downregulate the activity of PS-1. Overall, our study provides new insight into the role of tricetin-induced molecular regulation in the suppression of NPC metastasis and suggests that tricetin has prospective therapeutic applications for patients with NPC.

Salvianolic acid A suppresses MMP-2 expression and restrains cancer cell invasion through ERK signaling in human nasopharyngeal carcinoma

ETHNOPHARMACOLOGICAL RELEVANCE

Salvia miltiorrhiza Bunge, as known as Danshen, has used for the prevention and treatment of cardiovascular diseases clinically and anti-cancer activities. Salvianolic acid A (SAA), one of the most abundant ingredients, hydrophilic derivatives of Salvia miltiorrhiza Bunge, exerts a variety of pharmacological actions, such as anti-oxidative, anti-inflammatory and anti-cancer activities. However, the impact of SAA on nasopharyngeal carcinoma (NPC) invasion and metastasis remains unexplored.

AIM OF THE STUDY

To investigate the potential of SAA to prevent migration and invasion on NPC cell.

MATERIALS AND METHODS

MTT assay and Boyden chamber assay were performed to determine cell proliferation, migration and invasion abilities, respectively. The activity and protein expression of matrix metalloproteinase-2 (MMP-2) were determined by gelatin zymography and western blotting.

RESULTS

Here, we showed that SAA considerably suppressed the migrative and invasive activity of human NPC cells but not rendered cytotoxicity. In SAA-treated NPC cells, the activity and expression of matrix metalloproteinase-2 (MMP-2), a key regulator of cancer cell invasion, were reduced. Additionally, the presence of high concentrations of SAA dramatically abolished the activation of focal adhesion kinase (FAK) and moderately inhibited the phosphorylation of Src and ERK in NPC cells.

CONCLUSIONS

Our results demonstrated that SAA inhibited the migration and invasion of NPC cells, accompanied by downregulation of MMP-2 and inactivation of FAK, Src, and ERK pathways. These findings indicate a usefulness of SAA on restraining NPC invasion and metastasis.

Mitochondrial Oxidative Phosphorylation Complex Regulates NLRP3 Inflammasome Activation and Predicts Patient Survival in Nasopharyngeal Carcinoma

We previously reported that tumor inflammasomes play a key role in tumor control and act as favorable prognostic markers in nasopharyngeal carcinoma (NPC). Activated inflammasomes frequently form distinguishable specks and govern the cellular secretion of IL-1β. However, we know little about the biological and biochemical differences between cells with and without apoptosis-associated speck-like protein containing a caspase-recruitment domain (ASC) speck formation. In this study, we used proteomic iTRAQ analysis to analyze the proteomes of NPC cells that differ in their ASC speck formation upon cisplatin treatment. We identified proteins that were differentially over-expressed in cells with specks, and found that they fell into two Gene ontology (GO) pathways: mitochondrial oxidative phosphorylation (OxPhos) and ubiquinone metabolism. We observed up-regulation of various components of the OxPhos machinery (including NDUFB3, NDUFB8 and ATP5B), and subsequently found that these changes lead to mitochondrial ROS (mtROS) production, which promotes the formation and activation of NLRP3 inflammasomes and subsequent pyroptosis. In NPC patients, better local recurrence-free survival was significantly associated with high-level expression of NDUFB8 (p = 0.037) and ATP5B (p = 0.029), as examined using immunohistochemistry. However, there were no significant associations between the expression of NDUFB8 and ATP5B with overall survival of NPC patients. Together, our results demonstrate that up-regulated mitochondrial OxPhos components are strongly associated with NLRP3 inflammasome activation in NPC. Our findings further suggest that high-level expression of OxPhos components could be markers for local recurrence and/or promising therapeutic targets in patients with NPC.

Association Between Dose and Duration of Cisplatin Exposure with Cytotoxicity Effect on Nasopharyngeal Carcinoma Stem Cell

Nasopharyngeal carcinoma (NPC) is ranked 6th of malignant tumors in Indonesia. To analyze the correlation of dose and duration of cisplatin exposure with cytotoxic effects on nasopharyngeal carcinoma stem cells. The biopsy NPC tissue was cultured and processed to obtain NPC stem cells to be treated with cisplatin different doses and durations (24 and 48 h). The number of dead cells after exposure will be calculated using a hemocytometer. Death stem cell density of NPC at exposure of 2 μg/ml cisplatin dose was 81.37%, while the smallest death cell density a dose of 0.05 μg/ml after a 72-h observation was 21.3%. The coefficient correlation 0.827 and value p = 0.000 (p < 0.05). The analysis of the correlation between cisplatin exposure duration and death cell was also significant with the correlation coefficient - 0.357 and the value p = 0.001 (p < 0.05). There was a correlation between the increased dose of cisplatin with the cytotoxicity effects on NPC stem cell.

Ovatodiolide suppresses nasopharyngeal cancer by targeting stem cell-like population, inducing apoptosis, inhibiting EMT and dysregulating JAK/STAT signaling pathway

BACKGROUND

Treatment for metastatic nasopharyngeal carcinoma (NPC) is challenging. Till now, a truly effective chemotherapy regimen for NPC has not yet been identified. These clinical observations prompted us to investigate a potential drug as alternative option for treating.

PURPOSE

This study evaluated the inhibitory effects of Ovatodiolide (Ova), on tumorigenic and cancer stem cell characteristics of NPC cells.

METHODS

Two NPC cell lines (NPC-BM1 and NPC-BM2) were used to examine the anticancer effects of Ova and the molecular mechanism underlying these activities by using sulforhodamine B cytotoxicity assay, western blot, immunofluorescence, migration, colony and tumorsphere formation assays.

RESULTS

Ova significantly inhibited the viability of BM1 and BM2 cells, downregulated Bcl-xL and Puma, and upregulated Bax/Bad expression levels. Ova dose-dependent suppressed migratory/invasive potential of NPC cells, and reduced ability to form colonies. Ova-induced apoptosis correlated with increased Bax/Bcl-xL ratio while NPC motility and colony formation inhibition were associated with reduced expression of p-FAK, p-PXN, F-actin, and Slug proteins and increased E-cadherin. Furthermore, ova inhibited NPC tumorsphere formation, associated with decreased SOX2, OCT4 and JAK-STAT signaling pathway. Ova also attenuated NPC stem cell tumorigenicity, inhibited tumor growth, and enhanced the sensitivity of NPC cells to cisplatin treatment, in vivo.

CONCLUSIONS

Our results demonstrated the anticancer efficacy of Ova in NPC and its potential as a putative inhibitor of JAK2 and STAT3, which are essential in tumorigenesis of NPC. Further development of Ova is encouraged.

Fibronectin promotes nasopharyngeal cancer cell motility and proliferation

Nasopharyngeal cancer (NPC) is an Epstein-Barr virus (EBV)-associated carcinoma. Fibronectin is regarded as a prognosticator in NPC and its involvement in cell motility has been reported in EBV infection and viral latent membrane protein 1 (LMP1) overexpression NPC cell lines. However, its malignant potential in NPC cell lines without harbouring the EBV genome has not been investigated. We investigatd and compared among four NPC cell lines, and the results revealed a positive association between fibronectin levels and NPC cell motility as well as proliferation. Studies of antibody neutralization, exogenous addition, overexpression, and RNA interference confirmed a migration role of fibronectin in NPC cells involving integrin α5, Src, Rac1, and Cdc42, implying a mesenchymal-like cell movement. Furthermore, hypoxia-inducible factor-1α (HIF-1α) and transforming growth factor-β1 (TGF-β1) were identified as alternative activators of fibronectin expression and NPC cell migration. Besides cell migration, studies of RNA interference also showed a stimulatory effect of fibronectin in NPC cell proliferation. Mechanistic studies further revealed a subsequent reduction of HIF-1α, TGF-β1, cyclin D1, β-catenin, vimentin, and Slug together with decreased Src and Akt phosphorylation after fibronectin knockdown. Parallel studies in a xenograft tumor mice model further showed that tumor growth correlated well with elevation of circulating fibronectin and activation of the identified intracellular signaling molecules. The results of our study highlight a role of fibronectin in NPC cell motility and proliferation in concerted action with HIF-1α and TGF-β1 possibly through linking molecules Src and Akt. Fibronectin overexpression and autoantibody are known to have potential prognostic value in patients with NPC. Our findings shed light on the biochemical and molecular mechanisms underlying the pathogenic role of fibronectin in this disease.

Rubus idaeusInhibits Migration and Invasion of Human Nasopharyngeal Carcinoma Cells by Suppression of MMP-2 through Modulation of the ERK1/2 Pathway

Nasopharyngeal carcinoma (NPC) is characterized by a high incidence of metastasis in the neck lymph nodes, resulting in a poor prognosis and posing challenges for treatment. In this study, we investigated the in vitro antimetastatic properties of Rubus idaeus extract (RIE) on human nasopharyngeal carcinoma cells. HONE-1, NPC-39 and NPC-BM cells were subjected to RIE treatment, and effects on the migration and invasion of tumor cells were analyzed. The results showed that RIE suppressed the migration and invasion of NPC cells. Gelatin zymography assay, Western blotting and real-time PCR showed that matrix metalloproteinases-2 (MMP-2) enzyme activity, protein expression and mRNA levels were down-regulated by RIE treatment. To identify the signaling pathway, mitogen-activated protein kinase proteins were examined, which showed that phosphorylation of ERK1/2 was inhibited after the treatment of RIE. In summary, our data showed that RIE inhibited the migration and invasion of NPC cells by suppressing the expression of MMP-2 by down-regulating the ERK1/2 signaling pathway, suggesting that Rubus idaeus may serve as chemotherapeutic and chemopreventive agent for NPC.

Hispolon suppresses migration and invasion of human nasopharyngeal carcinoma cells by inhibiting the urokinase-plasminogen activator through modulation of the Akt signaling pathway

Hispolon has been reported to possess antioxidant, antiinflammatory, and antitumor activities. However, the effect of hispolon on the metastasis of nasopharyngeal carcinoma (NPC) remains unclear. In this study, we investigated how the antimetastatic activity and relevant signaling pathways of hispolon affected three NPC cell lines. The results revealed that hispolon significantly reduced the migration and invasion of three NPC cells in a dose-dependent manner from 0 to 50 µM. Hispolon also significantly inhibited the activity and expression of urokinase-plasminogen activator (uPA) as well as the phosphorylation of Akt. Moreover, blocking the Akt pathway also enhanced the antimetastatic ability of hispolon in the NPC cells. In conclusion, hispolon inhibited uPA expression and NPC cell metastasis by downregulating Akt signal pathways; therefore, hispolon exerts beneficial effects in chemoprevention. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 645-655, 2017.

Melatonin suppresses TPA-induced metastasis by downregulating matrix metalloproteinase-9 expression through JNK/SP-1 signaling in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC), a disease common in the South-East Asian population, has high lymph node metastatic ability. Melatonin, an endogenously produced substance present in animals, plants, fungi, and bacteria, has oncostatic activity via several mechanisms. The molecular mechanisms involved in melatonin-mediated tumor inhibitory potential are not completely defined. Here, we show that melatonin treatment inhibits TPA-induced cell motility by regulating the matrix metalloproteinase-9 (MMP-9) expression in NPC. We also identified the signaling cascade through which melatonin inhibits MMP-9 expression; this involves melatonin regulating the binding activity of the transcription factor specificity protein-1 (SP-1)-DNA. Our mechanistic analysis further reveals that the c-Jun N-terminal kinase/mitogen-activated protein kinase pathway is involved in the melatonin-mediated tumor suppressor activity. Furthermore, the findings indicate a functional link between melatonin-mediated MMP-9 regulation and tumor suppressing ability and provide new insights into the role of melatonin-induced molecular and epigenetic regulation of tumor growth. Thus, we conclude that melatonin suppresses the motility of NPC by regulating TPA-induced MMP-9 gene expression via inhibiting SP-1-DNA binding ability. The results provide a functional link between melatonin-mediated SP-1 regulation and the antimetastatic actions of melatonin on nasopharyngeal carcinoma.

Targeting annexin A2 reduces tumorigenesis and therapeutic resistance of nasopharyngeal carcinoma

The expression of annexin A2 (ANXA2) in nasopharyngeal carcinoma (NPC) cells induces the immunosuppressive response in dendritic cells; however, the oncogenic effect and clinical significance of ANXA2 have not been fully investigated in NPC cells. Immunohistochemical staining for ANXA2 was performed in 61 patients and the association with clinicopathological status was determined. Short hairpin (sh)RNA knockdown of ANXA2 was used to examine cellular effects of ANXA2, by investigating alterations in cell proliferation, migration, invasion, adhesion, tube-formation assay, and chemo- and radiosensitivity assays were performed. RT-qPCR, Western blotting, and immunofluorescence were applied to determine molecular expression levels. Clinical association studies showed that the expression of ANXA2 was significantly correlated with metastasis (p = 0.0326) and poor survival (p = 0.0256). Silencing of ANXA2 suppressed the abilities of cell proliferation, adhesion, migration, invasion, and vascular formation in NPC cell. ANXA2 up-regulated epithelial-mesenchymal transition associated signal proteins. Moreover, ANXA2 reduced sensitivities to irradiation and chemotherapeutic drugs. These results define ANXA2 as a novel prognostic factor for malignant processes, and it can serve as a molecular target of therapeutic interventions for NPC.

Characterization of NOL7 gene point mutations, promoter methylation, and protein expression in cervical cancer

NOL7 is a putative tumor suppressor gene localized to 6p23, a region with frequent loss of heterozygosity in a number of cancers, including cervical cancer (CC). We have previously demonstrated that reintroduction of NOL7 into CC cells altered the angiogenic phenotype and suppressed tumor growth in vivo by 95%. Therefore, to understand its mechanism of inactivation in CC, we investigated the genetic and epigenetic regulation of NOL7. NOL7 mRNA and protein levels were assessed in 13 CC cell lines and 23 consecutive CC specimens by real-time quantitative polymerase chain reaction, western blotting, and immunohistochemistry. Methylation of the NOL7 promoter was analyzed by bisulfite sequencing and mutations were identified through direct sequencing. A CpG island with multiple CpG dinucleotides spanned the 5' untranslated region and first exon of NOL7. However, bisulfite sequencing failed to identify persistent sites of methylation. Mutational sequencing revealed that 40% of the CC specimens and 31% of the CC cell lines harbored somatic mutations that may affect the in vivo function of NOL7. Endogenous NOL7 mRNA and protein expression in CC cell lines were significantly decreased in 46% of the CC cell lines. Finally, immunohistochemistry demonstrated strong NOL7 nucleolar staining in normal tissues that decreased with histologic progression toward CC. NOL7 is inactivated in CC in accordance with the Knudson 2-hit hypothesis through loss of heterozygosity and mutation. Together with evidence of its in vivo tumor suppression, these data support the hypothesis that NOL7 is the legitimate tumor suppressor gene located on 6p23.

The Epstein-Barr virus-encoded microRNA MiR-BART9 promotes tumor metastasis by targeting E-cadherin in nasopharyngeal carcinoma

MicroRNAs (miRNAs) are a family of small RNA molecules that negatively regulate the expression of protein-coding genes and play critical roles in orchestrating diverse cellular processes. This regulatory mechanism is also exploited by viruses to direct their life cycle and evade the host immune system. Epstein-Barr virus (EBV) is an oncogenic virus that is closely associated with multiple human diseases, including nasopharyngeal carcinoma (NPC), which is a highly metastatic type of tumor and is frequently reported in South Asia. Several viral proteins have been found to promote the migration and invasiveness of NPC cells. However, not all tumor tissues express these viral oncoproteins, suggesting that other mechanisms may contribute to the aggressive behavior of NPC tumor cells. A previous sequencing study by our group revealed that the EBV miRNA miR-BART9 was expressed at high levels in all EBV-positive NPC tissues. In the present study, we used gain- and loss-of-function approaches to investigate the effect of miR-BART9 in EBV-negative and EBV-positive NPC cells. We discovered that miR-BART9 promotes the migration and invasiveness of cultured NPC cells. The promigratory activity observed in vitro was manifested as an enhanced metastatic ability in vivo. Computational analysis revealed that miR-BART9 may target E-cadherin, a membrane protein that is pivotal in preserving cell-cell junctions and the epithelial phenotype. Through biochemical assays and functional rescue analysis, we confirmed that miR-BART9 specifically inhibits E-cadherin to induce a mesenchymal-like phenotype and promote the migration of NPC cells. These results indicated that miR-BART9 is a prometastatic viral miRNA and suggested that high levels of miR-BART9 in EBV-positive NPC cells may contribute to the aggressiveness of tumor cells.

MicroRNAs (miRNAs) are a family of small RNA molecules that negatively regulate the expression of protein-coding genes and orchestrate diverse cellular processes. This regulatory mechanism is also exploited by viruses to manage their life cycle and to evade the host immune system. Epstein-Barr virus (EBV) is closely associated with nasopharyngeal carcinoma (NPC), which is a highly metastatic type of tumor. A previous by our group study discovered that the EBV miRNA miR-BART9 is expressed at high levels in all EBV-positive NPC tissues. In the present study, we used gain- and loss-of-function approaches to investigate the function of miR-BART9 in EBV-negative and EBV-positive NPC cells. We showed that miR-BART9 promotes the migration and invasiveness of cultured NPC cells and enhances the metastatic ability of NPC tumors in vivo. Through computational analysis, we discovered that E-cadherin, a membrane protein that is critical for maintaining cell-cell contact and suppressing tumor metastasis, is a potential target for miR-BART9. Through biochemical assays and a functional rescue analysis, we confirmed that miR-BART9 specifically inhibits E-cadherin to enhance the motility of NPC cells. Our results show that miR-BART9 is a prometastatic viral miRNA and suggest that miR-BART9 may contribute to the aggressiveness of EBV-positive NPC tumors.

Low-molecular-mass secretome profiling identifies C-C motif chemokine 5 as a potential plasma biomarker and therapeutic target for nasopharyngeal carcinoma

Cancer cell secretome profiling has been shown to be a promising strategy for identifying potential body fluid-accessible cancer biomarkers and therapeutic targets. However, very few reports have investigated low-molecular-mass (LMr) proteins (<15kDa) in the cancer cell secretome. In the present study, we applied tricine-SDS-gel-assisted fractionation in conjunction with LC-MS/MS to systemically identify LMr proteins in the secretomes of three nasopharyngeal carcinoma (NPC) cell lines. We examined two NPC tissue transcriptome datasets to identify LMr genes/proteins that are highly upregulated in NPC tissues and also secreted/released from NPC cells, obtaining 35 candidates. We verified the overexpression of four targets (LSM2, SUMO1, RPL22, and CCL5) in NPC tissues by immunohistochemistry and demonstrated elevated plasma levels of two targets (S100A2 and CCL5) in NPC patients by ELISA. Notably, plasma CCL5 showed good power (AUC 0.801) for discriminating NPC patients from healthy controls. Additionally, functional assays revealed that CCL5 promoted migration of NPC cells, an effect that was effectively blocked by CCL5-neutralizing antibodies and maraviroc, a CCL5 receptor antagonist. Collectively, our data indicate the feasibility of the tricine-SDS-gel/LC-MS/MS approach for efficient identification of LMr proteins from cancer cell secretomes, and suggest that CCL5 is a potential plasma biomarker and therapeutic target for NPC.

BIOLOGICAL SIGNIFICANCE

Both LMr proteome and cancer cell secretome represent attractive reservoirs for discovery of cancer biomarkers and therapeutic targets. Our present study provides evidence for the practicality of using the tricine-SDS-PAGE/LC-MS/MS approach for in-depth identification of LMr proteins from the NPC cell secretomes, leading to the discovery of CCL5 as a potential plasma biomarker and therapeutic target for NPC. We believe that the modified GeLC-MS/MS approach used here can be further applied to explore extremely low-abundance, extracellular LMr proteins with important biological functions in other cell lines and biospecimens.

Induction of metastatic cancer stem cells from the NK/LAK-resistant floating, but not adherent, subset of the UP-LN1 carcinoma cell line by IFN-γ

As an advanced status of cancer stem cells (CSCs), metastatic CSCs (mCSCs) have been proposed to be the essential seeds that initiate tumor metastasis. However, the biology of mCSCs is poorly understood. In this study, we used a lymph node (LN) metastatic CEA-producing carcinoma cell line, UP-LN1, characterized by the persistent appearance of adherent (A) and floating (F) cells in culture, to determine the distribution of CSCs and mechanisms for the induction of mCSCs. F and A cells displayed distinct phenotypes, CD44(high)/CD24(low) and CD44(low)/CD24(high), respectively. The CSC-rich nature of F cells was typified by stronger expression of multiple drug resistance genes and a 7.8-fold higher frequency of tumor-initiating cells in NOD/SCID mice when compared with A cells. F cells showed a greater depression in HLA class I expression and an extreme resistance to NK/LAK-mediated cytolysis. Moreover, the NK/LAK-resistant F cells were highly susceptible to IFN-γ-mediated induction of surface CXCR4, with concomitant downregulation of cytoplasmic CXCL12 expression, whereas these two parameters remained essentially unchanged in NK/LAK-sensitive A cells. Following the induction of surface CXCR4, enhanced migratory/invasive potential of F cells was demonstrated by in vitro assays. Confocal immunofluorescence microscopy showed the two distinct phenotypes of F and A cells could be correspondingly identified in monodispersed and compact tumor cell areas within the patient's LN tumor lesion. In response to IFN-γ or activated NK/LAK cells, the CXCR4(+) mCSCs could be only induced from the CSCs, which were harbored in the highly tumorigenic CD44(high)/CD24(low) F subset. Our results revealed the complexity and heterogeneity of the CSC of this cell line/tumor and the differential immunomodulatory roles of F and A cells. A better understanding of the interactions among different classes of CSCs and their niches may assist us in eradicating the CSCs/mCSCs through targeted immunotherapy, chemotherapy, or both.

Identification of candidate nasopharyngeal carcinoma serum biomarkers by cancer cell secretome and tissue transcriptome analysis: potential usage of cystatin A for predicting nodal stage and poor prognosis

Nasopharyngeal carcinoma (NPC) is usually diagnosed at advanced clinical stages, resulting in poor outcomes. To discover serum biomarkers for improved NPC diagnosis and/or management, we simultaneously analyzed the NPC cell secretome and tissue transcriptome to identify candidate genes/proteins that are highly upregulated in NPC tissues and also secreted/released from NPC cells. Among the 30 candidates identified, 11 proteins were chosen for further validation using the serum samples from NPC patients and healthy controls, including cystatin A, cathepsin B, manganese superoxide dismutase and matrix metalloproteinase 2. The results showed that serum levels of all the four proteins were indeed higher in NPC patients versus healthy controls and that the use of a three-marker panel (cystatin A, manganese superoxide dismutase and matrix metalloproteinase 2) can contribute to a better NPC detection than each marker alone. In addition, a higher pretreated serum level of cystatin A was found to be associated with a higher nodal stage and poorer prognosis of NPC patients and cystatin A could modulate the migration and invasion of NPC cells in vitro. Altogether, our results indicate that analysis of both the cancer cell secretome and tissue transcriptome is a feasible strategy for efficient identification of novel NPC serum marker panel.

Identification and functional analysis of NOL7 nuclear and nucleolar localization signals

BACKGROUND

NOL7 is a candidate tumor suppressor that localizes to a chromosomal region 6p23. This locus is frequently lost in a number of malignancies, and consistent loss of NOL7 through loss of heterozygosity and decreased mRNA and protein expression has been observed in tumors and cell lines. Reintroduction of NOL7 into cells resulted in significant suppression of in vivo tumor growth and modulation of the angiogenic phenotype. Further, NOL7 was observed to localize to the nucleus and nucleolus of cells. However, the mechanisms regulating its subcellular localization have not been elucidated.

RESULTS

An in vitro import assay demonstrated that NOL7 requires cytosolic machinery for active nuclear transport. Using sequence homology and prediction algorithms, four putative nuclear localization signals (NLSs) were identified. NOL7 deletion constructs and cytoplasmic pyruvate kinase (PK) fusion proteins confirmed the functionality of three of these NLSs. Site-directed mutagenesis of PK fusions and full-length NOL7 defined the minimal functional regions within each NLS. Further characterization revealed that NLS2 and NLS3 were critical for both the rate and efficiency of nuclear targeting. In addition, four basic clusters within NLS2 and NLS3 were independently capable of nucleolar targeting. The nucleolar occupancy of NOL7 revealed a complex balance of rapid nucleoplasmic shuttling but low nucleolar mobility, suggesting NOL7 may play functional roles in both compartments. In support, targeting to the nucleolar compartment was dependent on the presence of RNA, as depletion of total RNA or rRNA resulted in a nucleoplasmic shift of NOL7.

CONCLUSIONS

These results identify the minimal sequences required for the active targeting of NOL7 to the nucleus and nucleolus. Further, this work characterizes the relative contribution of each sequence to NOL7 nuclear and nucleolar dynamics, the subnuclear constituents that participate in this targeting, and suggests a functional role for NOL7 in both compartments. Taken together, these results identify the requisite protein domains for NOL7 localization, the kinetics that drive this targeting, and suggest NOL7 may function in both the nucleus and nucleolus.

Tumor growth inhibition of metastatic nasopharyngeal carcinoma cell lines by low dose of arsenic trioxide via alteration of cell cycle progression and induction of apoptosis

BACKGROUND

Although arsenic trioxide (ATO) has displayed anticancer activity against primary nasopharyngeal carcinoma (NPC), its efficacy in metastatic NPC deserved further investigation because the biological/therapeutic difference in cancer cells probably exists between primary and distant sites.

METHODS

Two human metastatic NPC cell lines (NPC-BM1 and NPC-BM2) were investigated. We measured cellular proliferation, cell cycle, and apoptotic extent of BM1 and BM2 cells treated with ATO in vitro. Furthermore, we evaluated the tumor growth after ATO treatment in vivo.

RESULTS

Low-dose ATO treatment is sufficient to induce an antiproliferative effect, alter the cell cycle, and increase apoptosis in BM1 and BM2 cells. BM1 tumor growth in a xenograft model with low-dose and short-schedule (1 mg/kg/day, intraperitoneal injection for 5 consecutive days) of ATO treatment significantly slowed in vivo.

CONCLUSION

ATO at low dose seems to be an encouraging schedule for palliative treatment of metastatic NPC.

From NPC therapeutic target identification to potential treatment strategy

Nasopharyngeal carcinoma (NPC) is relatively rare in Western countries but is a common cancer in southern Asia. Many differentially expressed genes have been linked to NPC; however, how to prioritize therapeutic targets and potential drugs from unsorted gene lists remains largely unknown. We first collected 558 upregulated and 993 downregulated NPC genes from published microarray data and the primary literatures. We then postulated that conversion of gene signatures into the protein-protein interaction network and analyzing the network topologically could provide insight into key regulators involved in tumorigenesis of NPC. Of particular interest was the presence of cliques, called fully connected subgraphs, in the inferred NPC networks. These clique-based hubs, connecting with more than three queries and ranked higher than other nodes in the NPC protein-protein interaction network, were further narrowed down by pathway analysis to retrieve 24 upregulated and 6 downregulated bottleneck genes for predicting NPC carcinogenesis. Moreover, additional oncogenes, tumor suppressor genes, genes involved in protein complexes, and genes obtained after functional profiling were merged with the bottleneck genes to form the final gene signature of 38 upregulated and 10 downregulated genes. We used the initial and final NPC gene signatures to query the Connectivity Map, respectively, and found that target reduction through our pipeline could efficiently uncover potential drugs with cytotoxicity to NPC cancer cells. An integrative Web site (http://140.109.23.188:8080/NPC) was established to facilitate future NPC research. This in silico approach, from target prioritization to potential drugs identification, might be an effective method for various cancer researches.

Candidate serological biomarkers for cancer identified from the secretomes of 23 cancer cell lines and the human protein atlas

Although cancer cell secretome profiling is a promising strategy used to identify potential body fluid-accessible cancer biomarkers, questions remain regarding the depth to which the cancer cell secretome can be mined and the efficiency with which researchers can select useful candidates from the growing list of identified proteins. Therefore, we analyzed the secretomes of 23 human cancer cell lines derived from 11 cancer types using one-dimensional SDS-PAGE and nano-LC-MS/MS performed on an LTQ-Orbitrap mass spectrometer to generate a more comprehensive cancer cell secretome. A total of 31,180 proteins was detected, accounting for 4,584 non-redundant proteins, with an average of 1,300 proteins identified per cell line. Using protein secretion-predictive algorithms, 55.8% of the proteins appeared to be released or shed from cells. The identified proteins were selected as potential marker candidates according to three strategies: (i) proteins apparently secreted by one cancer type but not by others (cancer type-specific marker candidates), (ii) proteins released by most cancer cell lines (pan-cancer marker candidates), and (iii) proteins putatively linked to cancer-relevant pathways. We then examined protein expression profiles in the Human Protein Atlas to identify biomarker candidates that were simultaneously detected in the secretomes and highly expressed in cancer tissues. This analysis yielded 6-137 marker candidates selective for each tumor type and 94 potential pan-cancer markers. Among these, we selectively validated monocyte differentiation antigen CD14 (for liver cancer), stromal cell-derived factor 1 (for lung cancer), and cathepsin L1 and interferon-induced 17-kDa protein (for nasopharyngeal carcinoma) as potential serological cancer markers. In summary, the proteins identified from the secretomes of 23 cancer cell lines and the Human Protein Atlas represent a focused reservoir of potential cancer biomarkers.

Identification and characterization of the human NOL7 gene promoter

NOL7 is a candidate tumor suppressor gene that localizes to 6p23, a chromosomal region frequently associated with loss of heterozygosity in a number of malignancies including cervical cancer (CC). Re-expression of NOL7 in CC cells suppresses in vivo tumor growth by 95% and alters the angiogenic phenotype by modulating the expression of VEGF and TSP1. Here, we describe the determination of two NOL7 transcriptional start sites (TSS), the cloning of its regulatory promoter region, and the identification of transcription factors that regulate its expression. Using 5' Rapid amplification of complementary DNA ends (RACE), two transcriptional start sites were identified. Deletion analysis determined that the essential elements required for the optimal promoter activity of NOL7 were 560 bp upstream of its translation start site. In silico analysis suggested that the promoter region contained potential binding sites for the SP1, c-Myc and RXRalpha transcription factors as well as an overall GC content of greater than 60%. Chromatin immunoprecipitation (ChIP) confirmed that SP1, c-Myc and RXRalpha bound to the NOL7 promoter region. Finally, we demonstrate that NOL7 expression was positively regulated by c-Myc and RXRalpha. These results demonstrate that the NOL7 promoter region possesses each of the key elements of a TATA-less promoter. In addition, the positive regulation of NOL7 by c-Myc and RXRalpha provides additional mechanistic insights into the potential role of NOL7 in CC and other malignancies.

Molecular events associated with epithelial to mesenchymal transition of nasopharyngeal carcinoma cells in the absence of Epstein-Barr virus genome

Epithelial-mesenchymal transition (EMT) is an important process in tumor metastasis. The EMT-related events associated with metastasis of NPC in the absence of EBV have not been elucidated. We established an EBV-negative NPC cell line from a bone marrow biopsy of an NPC patient. Using a Matrigel system we isolated an invasive and non-invasive sublines, designated NPC-BM29 and NPC-BM00. NPC-BM29 acquired an invasive-like phenotype characterized by EMT, marked by down-regulation of E-cadherin and β-catenin with concomitant increased expression of Ets1. NPC-BM29 cells expressed ≥ 10-fold higher of MMP-9 than NPC-BM00 cells. NPC-BM29 cells grew better in 2% serum than NPC-BM00 cells, with a population doubling-time of 26.8 h and 30.7 h, respectively. A marked reduction in colony-formation ability of NPC-BM00 cells compared to NPC-BM29 was observed. Wound-healing assay revealed that NPC-BM29 cells displayed higher motility than NPC-BM00 and the motility was further enhanced by cell treatment with TPA, a PKC activator. Cell surface markers and tumor-associated molecules, AE3, MAK6 and sialyl-Tn, were up-regulated in NPC-BM29 cells, whereas the expression of HLA-DR and CD54 was significantly increased in NPC-BM00 cells. NPC-BM29 consistently released higher levels of IL-8 and IL-10 than NPC-BM00, with low levels of IL-1α expression in both cell lines. Higher level of VEGF production was detected in NPC-BM00 than NPC-BM29 cells. These data show that EBV is not required for exhibiting multiple metastatic phenotypes associated with EMT. More studies that target right molecules/signalings associated with the EMT may offer new therapeutic intervention options for NPC invasion and metastasis.

NOLC1, an enhancer of nasopharyngeal carcinoma progression, is essential for TP53 to regulate MDM2 expression

Nasopharyngeal carcinoma (NPC) is one of the most common cancers among Chinese living in South China, Singapore, and Taiwan. At present, its etiological factors are not well defined. To identify which genetic alterations might be involved in NPC pathogenesis, we identified genes that were differentially expressed in NPC cell lines and normal nasomucosal cells using subtractive hybridization and microarray analysis. Most NPC cell lines and biopsy specimens were found to have higher expression levels of the gene encoding nucleolar and coiled-body phosphoprotein 1 (NOLC1) as compared with normal cells. Severe combined immunodeficiency mice bearing NPC xenografts derived from NOLC1-short hairpin-RNA-transfected animals were found to have 82% lower levels of tumor growth than control mice as well as marked tumor cell apoptosis. Measuring the expression levels of genes related to cell growth, apoptosis, and angiogenesis, we found that the MDM2 gene was down-regulated in the transfectants. Both co-transfection and chromatin immunoprecipitation experiments showed that tumor protein 53-regulated expression of the MDM2 gene requires co-activation of NOLC1. These findings suggest that NOLC1 plays a role in the regulation of tumorigenesis of NPC and demonstrate that both NOLC1 and tumor protein 53 work together synergistically to activate the MDM2 promoter in NPC cells.

Differential baseline and response profile to IFN-gamma gene transduction of IL-6/IL-6 receptor-alpha secretion discriminate primary tumors versus bone marrow metastases of nasopharyngeal carcinomas in culture

BACKGROUND

Understanding of immunobiology of bone marrow metastases (designated BM-NPC) versus primary tumors (P-NPC) of the nasopharynx is far from complete. The aim of this study was to determine if there would be differences between cultured P-NPCs and BM-NPCs with respect to (i) constitutive IL-6 and the IL-6 receptor gp80 subunit (IL-6Ralpha) levels in the spent media of nontransduced cells, and (ii) IL-6 and IL-6Ralpha levels in the spent media of cells transduced with a retroviral vector containing the IFN-gamma gene.

METHODS

A panel of NPC cell lines were transduced with the IFN-gamma gene through a retroviral vector. Four clonal sublines were isolated via limiting dilution methods. Cytofluorometric analysis was performed for the detection of cell surface antigens of HLA class I, HLA class II and ICAM-1. ELISA was used to assay for IFN-gamma, IL-6 and IL-6Ralpha in the spent media of cultured cell lines.

RESULTS

Our results showed that in day 3 culture supernatants, low levels of soluble IL-6 were detected in 5/5 cultured tumors derived from P-NPCs, while much higher constitutive levels of IL-6 were detected in 3/3 metastasis-derived NPC cell lines including one originated from ascites; the difference was significant (p = 0.025). An inverse relationship was found between IL-6Ralpha and IL-6 in their release levels in cultured P-NPCs and metastasis-derived NPCs. In IFN-gamma-transduced-P-NPCs, IL-6 production increased and yet IL-6Ralpha decreased substantially, as compared to nontransduced counterparts. At variance with P-NPC cells, the respective ongoing IL-6 and IL-6Ralpha release patterns of BM-NPC cells were not impeded as much following IFN-gamma transduction. These observations were confirmed by extended kinetic studies with representative NPC cell lines and clonal sublines. The latter observation with the clonal sublines also indicates that selection for high IL-6 or low IL-6Ralpha producing subpopulations did not occur as a result of IFN-gamma-transduction process. P-NPCs, which secreted constitutively only marginal levels of IFN-gamma (8.4 ~ 10.5 pg/ml), could be enhanced to produce higher levels of IFN-gamma (6.8- to 10.3-fold increase) after IFN-gamma transduction. Unlike P-NPCs, BM-NPCs spontaneously released IFN-gamma at moderate levels (83.8 ~ 100.7 pg/ml), which were enhanced by 1.3- to 2.2-fold in the spent media of their IFN-gamma-transduced counterparts.

CONCLUSION

Our results showed that cultured P-NPCs and BM-NPCs could be distinguished from one another on the basis of their differential baseline secretion pattern of IFN-gamma, IL-6 and IL-6Ralpha, and their differential response profiles to IFN-gamma gene transfer of the production of these three soluble molecules. These results suggest that the IL-6 and IFN-gamma pathways in a background of genetic instability be involved in the acquisition of metastatic behaviour in BM-NPCs.

Overexpression of delta Np63 in a human nasopharyngeal carcinoma cell line downregulates CKIs and enhances cell proliferation

p63 belongs to a member of the tumor suppressor protein p53 family. Due to alternative promoter usage, two types of p63 proteins are produced. The DeltaNp63 isoform lacks the N-terminal transactivation domain and is thought to antagonize TAp63 and p53 in target gene regulation. DeltaNp63 has been found to be overexpressed in numerous human squamous cell carcinomas, including nasopharyngeal carcinoma (NPC). However, the role of DeltaNp63 overexpression in NPC pathogenesis has not been clear. In this study, we use a DeltaNp63 overexpressing human NPC cell line (NPC-076) to explore the possible roles of DeltaNp63 in cell proliferation and cell-cycle regulation. We found that the proliferation of NPC-076 cell is greatly suppressed when the overexpressed DeltaNp63 is silenced by specific DeltaNp63 siRNA. Further studies show that DeltaNp63 silencing results in the upregulation of CKIs, including p27(kip1) and p57(kip2) in both mRNA and protein levels. Cell-cycle analysis shows that DeltaNp63 silencing also results in an increased G1 phase cell and apoptotic cell population. Our findings indicate that DeltaNp63 plays important roles in the regulation of NPC-076 cell-cycle progression, and may play a role in the maintenance of NPC-076 tumor cell phenotype.

Glucose-regulated protein 78 regulates multiple malignant phenotypes in head and neck cancer and may serve as a molecular target of therapeutic intervention

Glucose-regulated protein 78 (Grp78) is an endoplasmic reticulum chaperone protein and is overexpressed in various cancers. However, it is unclear how significance of this molecule play an active role contributing to the oncogenic effect of head and neck cancer (HNC). To investigate the potential function of Grp78, six HNC cell lines were used. We found that Grp78 is highly expressed in all six cell lines and many of the proteins were localized in the periphery regions, implying other function of this molecule aside from endoplasmic reticulum stress response. Knockdown of Grp78 by small interfering RNA significantly reduced cell growth and colony formation to 53% to 12% compared with that of controls in all six HNC cell lines. Using in vitro wound healing and Matrigel invasion assays, we found that cell migration and invasive ability were also inhibited to 23% to 2% in all these cell lines tested. In vivo xenograft studies showed that administration of Grp78-small interfering RNA plasmid into HNC xenografts significantly inhibited both tumor growth in situ (>60% inhibition at day 34) and liver metastasis (>90% inhibition at day 20). Our study showed that Grp78 actively regulates multiple malignant phenotypes, including cell growth, migration, and invasion. Because knockdown Grp78 expression succeeds in the reduction of tumor growth and metastatic potential, this molecule may serve as a molecular target of therapeutic intervention for HNC.

Association of Epstein-Barr Virus with Nasopharyngeal Carcinoma and Current Status of Development of Cancer-derived Cell Lines

It is well known that the Epstein-Barr virus (EBV) contributes directly to tumourigenesis in nasopharyngeal carcinoma (NPC), primarily in the undifferentiated form of NPC (WHO type III; UNPC or UC), which is commonly found in South East Asia. Unfortunately, research in NPC has been severely hampered by the lack of authentic EBV-positive (EBV+) human NPC cell lines for study. Since 1975, there have been more than 20 reported NPC cell lines. However, many of these NPC-derived cell lines do not express EBV transcripts in long-term culture, and therefore that finding may dispute the fundamental theory of NPC carcinogenesis. In fact, currently only one EBV+ human NPC cell line (C-666) in long-term culture has been reported. Hence, most of the NPC cell lines may not be representative of the disease itself. In order to better understand and treat NPC, there is an urgent need to develop more EBV+ human NPC cell lines. In this review, we discuss the authenticity of existing NPC cell lines and the impact of our understanding of NPC biology on the treatment of the disease and the relationship of EBV to NPC in the context of cell lines. Key words: Carcinogenesis, Cell culture, Epstein-Barr virus, Hayflick’s limit

Differentially expressed genes in radioresistant nasopharyngeal cancer cells: gp96 and GDF15

Radiotherapy is the major treatment modality for nasopharyngeal cancer (NPC), but in some cases, the disease is radioresistant. We designed this study to identify genes that may be involved in this resistance. We first established two radioresistant subclone cell lines derived from NPC parental cell lines (NPC-076 and NPC-BM1) by treating the cells with four rounds of sublethal ionizing radiation. cDNA microarray analysis was then done, comparing the two resistant cell lines with their corresponding parental cell lines. Seven genes were found to be up-regulated in radioresistant subclones, including gp96 and GDF15, which had shown highest overexpressions. We constructed small interfering RNA plasmids (gp96si and GDF15si) and transfected them into NPC cells to knock down these genes and examine whether this changed their response to radiation. Both gp96si and GDF15si transfectants had radiation-induced growth delay and reduction in colonogenic survival compared with control cells. Knockdown of either gp96 or GDF15 increased the proportion of the cells in G(2)-M phase, the most radiosensitive phase of the cell cycle. We have therefore identified at least two genes, gp96 and GDF15, involved in radioresistance of NPC cell lines and showed that knockdown of the genes enhances radiosensitivity.

Chemokine receptor expression profiles in nasopharyngeal carcinoma and their association with metastasis and radiotherapy

Nasopharyngeal carcinoma (NPC) is an epithelial cancer that metastasizes predictably to cervical lymph nodes or distant organs. To assess whether the chemokine receptors of NPC cells play important roles in metastasis and are associated with radiotherapy history, the significance of various chemokine receptors (CCR1-10, CXCR1-6, XCR1, and CX3CR1) in NPC cell lines (TW01, TW04, HONE1, BM1, and AS1) and 52 NPC tumour biopsies from 48 patients with NPC was evaluated by mRNA and cytometric analyses, chemotaxis and actin polymerization assays, and immunohistochemical staining. Quantitative real-time reverse transcription-polymerase chain reaction revealed substantial expression of CCR7, CCR9, CXCR4, and CXCR6 mRNA in all the NPC cell lines. Of these, however, only CCR7, CXCR4, and CXCR6 were functional in NPC cells. Negative immunoreactivity for CCR7, CXCR4, and CXCR6 was demonstrated in almost all nasopharyngeal (NP) specimens from patients with primary NPC (n = 12) and in those with regional metastatic NPC (n = 15). However, expression of two or three of these chemokine receptors was demonstrated in NP specimens from patients with liver metastasis. Strong positivity was demonstrated for all three of these chemokine receptors in almost all of the regional and distant metastasis specimens. Significant differences in the expression of CCR7, CXCR4, and CXCR6 were found between primary tumours and metastases (p < 0.001, p < 0.001, and p < 0.002, respectively). This observation was further confirmed by laser capture microdissection of freshly frozen tumours from primary (n = 5) and metastatic (n = 8) NPC sites (p = 0.04, 0.03, and 0.03 for CCR7, CXCR4, and CXCR6, respectively). Finally, significant differences in CXCR4 expression were demonstrated between de novo and post-radiotherapy groups (1/22 vs. 5/8; p < 0.003). It appears reasonable to conclude, therefore, that CCR7, CXCR4, and CXCR6 are expressed and active in human NPC metastases, while CXCR4 expression is associated with radiotherapy history.

DSG3 is overexpressed in head neck cancer and is a potential molecular target for inhibition of oncogenesis

To identify genes that could potentially serve as molecular therapeutic markers for human head and neck cancer (HNC), we employed differential display analysis to compare the gene expression profiles between HNC and histopathologically normal epithelial tissues. Using reverse transcription-polymerase chain reaction and Western blot analysis, desmoglein 3 (DSG3) was identified as being differentially expressed at both the RNA and protein levels. Of 56 patients assayed, 34 (61%) had overexpression of DSG3, which correlated statistically with T stage (P=0.009), N stage (P=0.047), overall stage (P=0.011), tumor depth (P=0.009) and extracapsular spread in lymph nodes (P=0.044), suggesting that DSG3 participates in carcinogenesis of HNC. Consistent with the clinical findings, inhibition of DSG3 by RNA interference (RNAi) significantly reduced cell growth and colony formation to 57-21% in three HNC cell lines. Use of an in vitro wound healing and Matrigel invasion assays, we found that cell migration and invasive ability were also inhibited to 30-48% in three cell lines tested. An in vivo xenograft study showed that administration of DSG3-RNAi plasmid significantly inhibited tumor growth for 2 months in BALB/C nude mice. In conclusion, DSG3 is identified overexpressed in HNC, with the degree of overexpression associated with clinicopathologic features of the tumor. Inhibition of DSG3 significantly suppresses carcinogenic potential in cellular and in vivo animal studies. These findings suggest that DSG3 is a potential molecular target in the development of adjuvant therapy for HNC.

Prediction of poor survival by cyclooxygenase-2 in patients with T4 nasopharyngeal cancer treated by radiation therapy: clinical and in vitro studies

BACKGROUND

This study was undertaken to determine the status of cyclooxygenase-2 (COX-2) in nasopharyngeal cancer (NPC) in Taiwanese patients and its relationship to survival after radiotherapy (RT). In addition, the effect of NS-398, a potent selective COX-2 inhibitor, was tested in vitro alone and in combination with radiation on NPC-BM1 human NPC cells as a prelude to using this drug along with RT in the treatment of patients with NPC.

METHODS

Thirty-seven patients diagnosed with T4N0-3M0 NPC were enrolled into this study. COX-2 expression was determined by immunohistochemical staining of formalin-fixed, paraffin-embedded tumor tissue. Patient survival was the clinical end point. The effects of COX-2 expression on cell survival and radioresistance was tested in vitro using the selective COX-2 inhibitor NS-398 in conjunction with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazonium bromide (MTT) and clonogenic assays.

RESULTS

COX-2 immunoreactivity was detected in 62% of NPC tumors, and expression levels were high in 43%. Survival analysis showed the 5-year overall survival rates for patients who had high COX-2 expression was 27% compared with 60% for those with low/absent expression (p = .047). Pattern of failure analysis showed no significant difference between high and low COX-2 expression in locoregional failure (27% vs 25%, p = .91). However, patients with N0 to N1 disease and high COX-2 expression had a significantly higher incidence of distant metastasis compared with patients with stage N0 to N1 disease and low COX-2 expression (83% vs 15%, p = .004). This difference was not observed in patients with N2 to N3 disease. This difference contributed to worse survival of patients whose tumors had high COX-2 expression levels. The selective COX-2 inhibitor NS-398 was directly cytotoxic to NPC-BM1 cells in vitro, as judged in an MTT assay (viable cells decreased from 92% to 76%, 52%, and 22%, with increases of NS-398 from 20 to 40, 60, and 80 microM, respectively). Radiation-induced cell death was also increased by treatment with NS-398. At a 10% survival level, 40 microM NS-398 increased radiation cytotoxicity by a factor of 1.37, whereas 60 microM increased it by a factor of 4.9.

CONCLUSIONS

COX-2 overexpression is a predictor for poor survival for advanced stage NPC. In vitro, NS-398 radiosensitizes the NPC-BM1 cell line, providing a basis for testing the combination of COX-2 inhibitors with radiation in the treatment of patients with NPC.

Sequential cytogenetic and molecular cytogenetic characterization of an SV40T-immortalized nasopharyngeal cell line transformed by Epstein-Barr virus latent membrane protein-1 gene

Cytogenetic and molecular cytogenetic analyses were performed on four sublines derived from a newly established, SV40T-immortalized nasopharyngeal (NP) cell line, NP69, with two of the sublines expressing LMP1, an Epstein-Barr virus-encoded gene. A total of seven cytogenetically related subclones were identified, all having highly complex karyotypes with massive numerical and structural rearrangements. Centromeric rearrangements in the form of isochromosomes and whole-arm translocations were prevalent. A cytogenetic sign of gene amplification [i.e., homogeneously staining region (HSR)] was detected at 1q25 in all metaphase cells analyzed. Multicolor combined binary ratio labeling fluorescence in situ hybridization (COBRA-FISH) was used to confirm the karyotypic interpretations. Furthermore, multicolor COBRA-FISH also showed that part of the HSR contained chromosome 20 material. Extensive clonal evolution could be observed by the assessment of karyotypic variation among different subclones and individual metaphase cells. The evaluation of clonal evolution enabled the identification of the temporal order of chromosome aberrations during cell immortalization and malignant transformation. A striking karyotypic similarity was found between sublines expressing LMP1 and an NP carcinoma cell line, with loss of genetic material from chromosome arm 3p being an important recurrent observation. More interestingly, the karyotypic features of NP69 were also similar to those of many epithelial malignancies. Our observations suggest that serial transformation of NP cell lines might provide a useful in vitro model for the study of the multistep neoplastic transformation of NP cells.