Frequent hypermethylation of RASSF1A and TSLC1, and high viral load of Epstein-Barr Virus DNA in nasopharyngeal carcinoma and matched tumor-adjacent tissues

Shifted-excitation Raman difference spectroscopy for improving in vivo detection of nasopharyngeal carcinoma

A strong fluorescence background is one of the common interference factors of Raman spectroscopic analysis in biological tissue. This study developed an endoscopic shifted-excitation Raman difference spectroscopy (SERDS) system for real-time in vivo detection of nasopharyngeal carcinoma (NPC) for the first time. Owing to the use of the SERDS method, the high-quality Raman signals of nasopharyngeal tissue could be well extracted and characterized from the complex raw spectra by removing the fluorescence interference signals. Significant spectral differences relating to proteins, phospholipids, glucose, and DNA were found between 42 NPC and 42 normal tissue sites. Using linear discriminant analysis, the diagnostic accuracy of SERDS for NPC detection was 100%, which was much higher than that of raw Raman spectroscopy (75.0%), showing the great potential of SERDS for improving the accurate in vivo detection of NPC.

Hypermethylation of the RASSF1A gene promoter as the tumor DNA marker for nasopharyngeal carcinoma

BACKGROUND

RASSF1A is a tumor suppressor gene. The methylation of RASSF1A has been reported to be associated with nasopharyngeal tumorigenesis. However, the heterogeneity was high among different studies. A meta-analysis was performed to evaluate the value of RASSF1A methylation for the diagnosis and early screening of nasopharyngeal carcinoma.

METHODS

Relevant articles were identified by searching the MEDLINE database. Frequency and odds ratio (OR) were applied to estimate the effect of CDH-1 methylation based on random-/fixed-effect models. The meta-analysis was performed by using MedCalc^® software. Subgroup analyses were performed by test method, ethnicity, and source of nasopharyngeal carcinoma samples to determine likely sources of heterogeneity.

RESULTS

A total of 17 studies, including 1688 samples (1165 nasopharyngeal carcinoma samples, and 523 from non-cancerous samples) were used for the meta-analysis. The overall frequencies of RASSF1A methylation were 59.68% and 2.65% in case-group and control-group, respectively. By removing the poor relative studies, the heterogeneity was not observed among the studies included. The association between RASSF1A gene methylation and the risk of nasopharyngeal carcinoma was also confirmed by calculating the OR value of 30.32 (95%CI  = 18.22-50.47) in the fixed-effect model (Q = 16.41, p = 0.36,I² = 8.62, 95% CI = 0.00-45.27). Additionally, the significant association was also found between the methylation of the RASSF1A gene and the subgroups.

CONCLUSIONS

This is the first meta-analysis that has provided scientific evidence that the methylation of RASSF1A is the potential diagnosis, prognosis, and early screening biomarker for nasopharyngeal carcinoma.

High throughput sequencing of whole transcriptome and construct of ceRNA regulatory network in RD cells infected with enterovirus D68

Background

With the advancement of sequencing technologies, a plethora of noncoding RNA (ncRNA) species have been widely discovered, including microRNAs (miRNAs), circular RNAs (circRNAs), and long ncRNAs (lncRNAs). However, the mechanism of these non-coding RNAs in diseases caused by enterovirus d68 (EV-D68) remains unclear. The goal of this research was to identify significantly altered circRNAs, lncRNAs, miRNAs, and mRNAs pathways in RD cells infected with EV-D68, analyze their target relationships, demonstrate the competing endogenous RNA (ceRNA) regulatory network, and evaluate their biological functions.

Methods

The total RNAs were sequenced by high-throughput sequencing technology, and differentially expressed genes between control and infection groups were screened using bioinformatics method. We discovered the targeting relationship between three ncRNAs and mRNA using bioinformatics methods, and then built a ceRNA regulatory network centered on miRNA. The biological functions of differentially expressed mRNAs (DEmRNAs) were discovered through GO and KEGG enrichment analysis. Create a protein interaction network (PPI) to seek for hub mRNAs and learn more about protein–protein interactions. The relative expression was verified using RT-qPCR. The effects of Fos and ARRDC3 on virus replication were confirmed using RT-qPCR, virus titer (TCID₅₀/ml), Western blotting.

Results

375 lncRNAs (154 upregulated and 221 downregulated), 33 circRNAs (32 upregulated and 1 downregulated), 96 miRNAs (49 upregulated and 47 downregulated), and 239 mRNAs (135 upregulated and 104 downregulated) were identified as differently in infected group compare to no-infected group. A single lncRNA or circRNA can be connected with numerous miRNAs, which subsequently coregulate additional mRNAs, according to the ceRNA regulatory network. The majority of DEmRNAs were shown to be connected to DNA binding, transcription regulation by RNA polymerase II, transcription factor, MAPK signaling pathways, Hippo signal pathway, and apoptosis pathway, according to GO and KEGG pathway enrichment analysis. The hub mRNAs with EGR1, Fos and Jun as the core were screened through PPI interaction network. We preliminarily demonstrated that the Fos and ARRDC3 genes can suppress EV-D68 viral replication in order to further verify the results of full transcriptome sequencing.

Conclusion

The results of whole transcriptome analysis after EV-D68 infection of RD cells were first reported in this study, and for the first time, a ceRNA regulation network containing miRNA at its center was established for the first time. The Fos and ARRDC3 genes were found to hinder viral in RD cells. This study establishes a novel insight host response during EV-D68 infection and further investigated potential drug targets.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12985-021-01686-x.

Promoter Hypermethylation of Tumor Suppressor Genes Located on Short Arm of the Chromosome 3 as Potential Biomarker for the Diagnosis of Nasopharyngeal Carcinoma

DNA methylation, the most common epigenetic alteration, has been proven to play important roles in nasopharyngeal carcinoma (NPC). Numerous tumor suppressor genes located on the chromosome 3p, particularly in the region of 3p21, are frequently methylated in NPC, thus suggesting great potential for diagnosis of NPC. In this review, we summarize recent findings of tumor suppressor genes on chromosome 3 that likely drive nasopharyngeal tumor development and progression, based on previous studies related to the hypermethylation of these target genes. Better understanding will allow us to design further experiments to establish a potential test for diagnosis of NPC, as well as bring about methylated therapies to improve the treatment of NPC.

Targeting the signaling in Epstein-Barr virus-associated diseases: mechanism, regulation, and clinical study

Epstein–Barr virus-associated diseases are important global health concerns. As a group I carcinogen, EBV accounts for 1.5% of human malignances, including both epithelial- and lymphatic-originated tumors. Moreover, EBV plays an etiological and pathogenic role in a number of non-neoplastic diseases, and is even involved in multiple autoimmune diseases (SADs). In this review, we summarize and discuss some recent exciting discoveries in EBV research area, which including DNA methylation alterations, metabolic reprogramming, the changes of mitochondria and ubiquitin-proteasome system (UPS), oxidative stress and EBV lytic reactivation, variations in non-coding RNA (ncRNA), radiochemotherapy and immunotherapy. Understanding and learning from this advancement will further confirm the far-reaching and future value of therapeutic strategies in EBV-associated diseases.

DNA Tumor Virus Regulation of Host DNA Methylation and Its Implications for Immune Evasion and Oncogenesis

Viruses have evolved various mechanisms to evade host immunity and ensure efficient viral replication and persistence. Several DNA tumor viruses modulate host DNA methyltransferases for epigenetic dysregulation of immune-related gene expression in host cells. The host immune responses suppressed by virus-induced aberrant DNA methylation are also frequently involved in antitumor immune responses. Here, we describe viral mechanisms and virus–host interactions by which DNA tumor viruses regulate host DNA methylation to evade antiviral immunity, which may contribute to the generation of an immunosuppressive microenvironment during cancer development. Recent trials of immunotherapies have shown promising results to treat multiple cancers; however, a significant number of non-responders necessitate identifying additional targets for cancer immunotherapies. Thus, understanding immune evasion mechanisms of cancer-causing viruses may provide great insights for reversing immune suppression to prevent and treat associated cancers.

Metabolic Phase I (CYPs) and Phase II (GSTs) Gene Polymorphisms and Their Interaction with Environmental Factors in Nasopharyngeal Cancer from the Ethnic Population of Northeast India

Multiple genetic and environmental factors and their interaction are believed to contribute in the pathogenesis of Nasopharyngeal Cancer (NPC). We investigate the role of Metabolic Phase I (CYPs) and Phase II (GSTs) gene polymorphisms, gene-gene and gene-environmental interaction in modulating the susceptibility to NPC in Northeast India. To determine the association of metabolic gene polymorphisms and environmental habits, 123 cases and 189 controls blood/swab samples were used for PCR and confirmed by Sanger sequencing. Analysis for GSTM1 and GSTT1 gene polymorphism was done by multiplex PCR. The T3801C in the 3'- flanking region of CYP1A1 gene was detected by PCR-RFLP method. The Logistic regression analysis was used to estimate odds ratios (OR) and 95% confidence intervals (95% CI). The GSTM1 null genotype alone (OR = 2.76) was significantly associated with NPC risk (P < 0.0001). The combinations of GSTM1 null and GSTT1 null genotypes also higher, 3.77 fold (P < 0.0001), risk of NPC, while GSTM1 null genotype along with CYP1A1 T3801C TC + CC genotype had 3.22 (P = 0.001) fold risk. The most remarkable risk was seen among individual carrying GSTM1 null, GSTT1 null genotypes and CYP1A1 T3801C TC + CC genotypes (OR = 5.71, P = 0.001). Further; analyses demonstrate an enhanced risk of NPC in smoked meat (OR = 5.56, P < 0.0001) and fermented fish consumers (OR = 5.73, P < 0.0001) carrying GSTM1 null genotype. An elevated risk of NPC was noted in smokers (OR = 12.67, P < 0.0001) and chewers (OR = 5.68, P < 0.0001) with GSTM1 null genotype. However, smokers had the highest risk of NPC among individuals carrying GSTT1 null genotype (OR = 4.46, P = 0.001) or CYP1A1 T3801C TC + CC genotype (OR = 7.13, P < 0.0001). The association of null genotypes and mutations of metabolic neutralizing genes along with the environmental habits (tobacco smokers and chewers, smoke meat, fermented fishes) can be used as a possible biomarker for early detection and preventive measure of NPC.

Molecular profile of nasopharyngeal carcinoma: analysing tumour suppressor gene promoter hypermethylation by multiplex ligation-dependent probe amplification

Aims

To assess differences in methylation profiles, and thus pathogenesis, between Epstein-Barr virus (EBV)-positive and negative nasopharyngeal carcinomas (NPCs). Also, promoter hypermethylation is a common phenomenon in early carcinogenesis to inactivate tumour suppressor genes. Since epigenetic changes are reversible, the therapeutic application of methylation inhibitors could provide treatment options.

Methods

We evaluated promoter hypermethylation profiles of 22 common tumour suppressor genes in 108 NPCs using methylation-specific multiplex ligation-dependent probe amplification. Correlation between methylation, clinicopathological features (including EBV) and survival was examined. Cluster analysis was also performed.

Results

Hypermethylation of RASSF1A and ESR1 was significantly more frequent in EBV-positive NPC, while hypermethylation of DAPK1 was more frequent in EBV-negative NPC. In logistic regression, age, with EBV-positive NPC occurring at earlier age, and RASSF1, with RASSF1 hypermethylation being more frequent in EBV-positive NPC, remained significant. In EBV-positive NPC, hypermethylation of RASSF1A predicted worse overall survival (OS) (HR 3.058,95% CI 1.027 to 9.107). In EBV-negative NPC, hypermethylated adenomatous polyposis coli (APC) was a predictor of poor disease-free survival (DFS) (HR 6.868, 95% CI 2.142 to 22.022).

Conclusion

There are important epigenetic differences between EBV-negative and EBV-positive NPCs, with EBV-negative NPC having a more similar hypermethylation profile to other head and neck squamous cell carcinomas than EBV-positive NPC. Hypermethylation of RASSF1A might contribute to worse OS in EBV-positive NPC, and may be an important event in the pathogenesis of EBV-infected NPC. Hypermethylation of APC might contribute to worse DFS in EBV-negative NPC.

Epstein-Barr virus: a master epigenetic manipulator

Like all herpesviruses, the ability of Epstein-Barr virus (EBV) to establish life-long persistent infections is related to a biphasic viral lifecycle that involves latency and reactivation/lytic replication. Memory B cells serve as the EBV latency compartment where silencing of viral gene expression allows maintenance of the viral genome, avoidance of immune surveillance, and life-long carriage. Upon viral reactivation, viral gene expression is induced for replication, progeny virion production, and viral spread. EBV uses the host epigenetic machinery to regulate its distinct viral gene expression states. However, epigenetic manipulation by EBV affects the host epigenome by reprogramming cells in ways that leave long-lasting, oncogenic phenotypes. Such virally-induced epigenetic alterations are evident in EBV-associated cancers.

DNA Oncogenic Virus-Induced Oxidative Stress, Genomic Damage, and Aberrant Epigenetic Alterations

Approximately 20% of human cancers is attributable to DNA oncogenic viruses such as human papillomavirus (HPV), hepatitis B virus (HBV), and Epstein-Barr virus (EBV). Unrepaired DNA damage is the most common and overlapping feature of these DNA oncogenic viruses and a source of genomic instability and tumour development. Sustained DNA damage results from unceasing production of reactive oxygen species and activation of inflammasome cascades that trigger genomic changes and increased propensity of epigenetic alterations. Accumulation of epigenetic alterations may interfere with genome-wide cellular signalling machineries and promote malignant transformation leading to cancer development. Untangling and understanding the underlying mechanisms that promote these detrimental effects remain the major objectives for ongoing research and hope for effective virus-induced cancer therapy. Here, we review current literature with an emphasis on how DNA damage influences HPV, HVB, and EBV replication and epigenetic alterations that are associated with carcinogenesis.

Diagnostic Capacity of RASSF1A Promoter Methylation as a Biomarker in Tissue, Brushing, and Blood Samples of Nasopharyngeal Carcinoma

Methylation of the RAS association domain family protein 1A (RASSF1A) promoter has been observed in nasopharyngeal carcinoma (NPC). This study investigated the correlation of RASSF1A promoter methylation with clinicopathological features and its utility as a diagnostic biomarker in NPC. A total of 926 patients with NPC and 495 non-tumor controls were analyzed in this study. RASSF1A promoter methylation was notably higher in NPC compared with non-tumor tissue, brushing and blood samples. RASSF1A promoter methylation was associated with clinical stage, lymph node status, distant metastasis, and T classification of patients with NPC, although it was not linked to age and sex. The pooled sensitivity, specificity, and AUC (area under the curve) of RASSF1A promoter methylation were determined in NPC samples vs. non-tumor samples (tissue: sensitivity=0.72, specificity=0.99, AUC=0.98; brushing: sensitivity=0.56, specificity=1.00, AUC=0.94; blood: sensitivity=0.11, specificity=0.98, AUC=0.97). Our findings show that RASSF1A promoter methylation may be correlated with the development, progression and metastasis of NPC. RASSF1A promoter methylation is a promising noninvasive biomarker for the diagnosis of NPC from tissue and brushing samples.

Folate deficiency and aberrant expression of cell adhesion molecule 1 are potential indicators of prognosis in laryngeal squamous cell carcinoma

The etiology of laryngeal squamous cell carcinoma (LSCC) has not yet been adequately examined. Therefore, the present study aimed to investigate the association between serum folate deficiency and abnormal expression of the cell adhesion molecule 1 (CADM1) protein in the progression of LSCC. Samples were collected from 60 patients with LSCC and 30 healthy people. Radioimmunoassays and immunohistochemical staining were performed to measure serum folate levels and CADM1 protein expression, respectively. The results demonstrated that CADM1 expression in LSCC specimens was significantly lower than in adjacent normal tissues (χ²=28.229, P<0.001), which was associated with histological differentiation and clinical stage (P=0.010 and 0.020, respectively). Levels of serum folate in patients with LSCC were significantly lower than those observed in healthy individuals (P=0.002). Furthermore, TSLCl expression and serum folate levels were positively correlated in LSCC (r=0.642, P=0.001). Thus, the present study determined that decreased CADM1 protein expression and low levels of serum folate were correlated with an increased severity of LSCC.

Identification of genes involved in Epstein-Barr virus-associated nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is the most common cancer originating from the nasopharynx, and can be induced by infection with Epstein-Barr virus (EBV). To study the mechanisms of EBV-associated NPC, a microarray of the GSE12452 dataset was analyzed. GSE12452 was downloaded from Gene Expression Omnibus and consisted of 31 NPC samples and 10 normal healthy nasopharyngeal tissue samples. The differentially-expressed genes (DEGs) were screened using the linear models for microarray data package in R. Using Database for Annotation, Visualization and Integrated Discovery software, potential functions of the DEGs were predicted by Gene Ontology and pathway enrichment analyses. With the information from the Search Tool for the Retrieval of Interacting Genes/Proteins database, the protein-protein interaction (PPI) network was visualized by Cytoscape. Furthermore, modules of the PPI network were searched using ClusterONE in Cytoscape. A total of 951 DEGs were screened in the NPC samples compared with the normal healthy nasopharyngeal tissue samples. Function enrichment indicated that the upregulated genes were associated with the cell cycle, cytoskeleton organization and DNA metabolism. Meanwhile, the downregulated genes were mainly associated with cell differentiation, hormone metabolism, inflammatory response and immune response. PPI networks for the DEGs suggested that upregulated mitotic arrest deficient 2-like 1 (MAD2L1; degree=133), proliferating cell nuclear antigen (PCNA; degree=125) and cyclin B1 (CCNB1; degree=115), and downregulated member A1 of aldehyde dehydrogenase 1 (ALDH1A1; degree=15) may be of great importance as they exhibited higher degrees on interaction. Mucin 1 (MUC1) was a key node of module 4. Overall, the study indicated that MAD2L1, CCNB1, PCNA, ALDH1A1 and MUC1 may have a correlation with EBV-associated NPC.

Epigenetic impact of infection on carcinogenesis: mechanisms and applications

Viral and bacterial infections are involved in the development of human cancers, such as liver, nasopharyngeal, cervical, head and neck, and gastric cancers. Aberrant DNA methylation is frequently present in these cancers, and some of the aberrantly methylated genes are causally involved in cancer development and progression. Notably, aberrant DNA methylation can be present even in non-cancerous or precancerous tissues, and its levels correlate with the risk of cancer development, producing a so-called 'epigenetic field for cancerization'. Mechanistically, most viral or bacterial infections induce DNA methylation indirectly via chronic inflammation, but recent studies have indicated that some viruses have direct effects on the epigenetic machinery of host cells. From a translational viewpoint, a recent multicenter prospective cohort study demonstrated that assessment of the extent of alterations in DNA methylation in non-cancerous tissues can be used to predict cancer risk. Furthermore, suppression of aberrant DNA methylation was shown to be a useful strategy for cancer prevention in an animal model. Here, we review the involvement of aberrant DNA methylation in various types of infection-associated cancers, along with individual induction mechanisms, and we discuss the application of these findings for cancer prevention, diagnosis, and therapy.

Epigenetic silencing of tumor suppressor genes during in vitro Epstein-Barr virus infection

DNA-methylation at CpG islands is one of the prevalent epigenetic alterations regulating gene-expression patterns in mammalian cells. Hypo- or hypermethylation-mediated oncogene activation, or tumor suppressor gene (TSG) silencing mechanisms, widely contribute to the development of multiple human cancers. Furthermore, oncogenic viruses, including Epstein-Barr virus (EBV)-associated human cancers, were also shown to be influenced by epigenetic modifications on the viral and cellular genomes in the infected cells. We investigated EBV infection of resting B lymphocytes, which leads to continuously proliferating lymphoblastoid cell lines through examination of the expression pattern of a comprehensive panel of TSGs and the epigenetic modifications, particularly methylation of their regulatory sequences. EBV infection of primary B lymphocytes resulted in global transcriptional repression of TSGs through engagement of hypermethylation. Therefore, CpG methylation profiles of TSGs may be used as a prognostic marker as well as development of potential therapeutic strategies for controlling acute infection and EBV-associated B-cell lymphomas.

Novel roles and therapeutic targets of Epstein-Barr virus-encoded latent membrane protein 1-induced oncogenesis in nasopharyngeal carcinoma

Epstein-Barr virus (EBV) was first discovered 50 years ago as an oncogenic gamma-1 herpesvirus and infects more than 90% of the worldwide adult population. Nasopharyngeal carcinoma (NPC) poses a serious health problem in southern China and is one of the most common cancers among the Chinese. There is now strong evidence supporting a role for EBV in the pathogenesis of NPC. Latent membrane protein 1 (LMP1), a primary oncoprotein encoded by EBV, alters several functional and oncogenic properties, including transformation, cell death and survival in epithelial cells in NPC. LMP1 may increase protein modification, such as phosphorylation, and initiate aberrant signalling via derailed activation of host adaptor molecules and transcription factors. Here, we summarise the novel features of different domains of LMP1 and several new LMP1-mediated signalling pathways in NPC. When then focus on the potential roles of LMP1 in cancer stem cells, metabolism reprogramming, epigenetic modifications and therapy strategies in NPC.

Tumor Suppressor in Lung Cancer-1 Is a Prognostic Predictor for the Recurrence and Progression of Non-Muscle-Invasive Bladder Cancer

OBJECTIVE

To investigate the relationship between the expression of tumor suppressor in lung cancer-1 (TSLC1) and clinicopathological characteristics of patients with non-muscle-invasive bladder cancer (NMIBC) and evaluate the prognostic significance of TSLC1.

METHODS

TSLC1 expression in 241 specimens of NMIBC was examined by immunohistochemistry. The correlation between TSLC1 expression and clinicopathological characteristics was evaluated using the chi-square test. The prognostic significance of TSLC1 was analyzed by univariate, multivariate analysis and Kaplan-Meier survival curves.

RESULTS

The total negative rate of TSLC1 expression was 47.3% in NMIBC. Decreased expression of TSLC1 was correlated with a higher clinical stage, higher pathological grade, the number of tumors, lager tumor size, tumor recurrence and progression. TSLC1 expression was an independent risk factor for predicting tumor recurrence (p = 0.005) and progression (p < 0.001).

CONCLUSION

Decreased expression of TSLC1 is correlated with the malignancy of NMIBC tissues and low TSLC1 expression may serve as a predictor for bladder cancer recurrence and progression.

Quantification of Epstein-Barr virus DNA load in nasopharyngeal brushing samples in the diagnosis of nasopharyngeal carcinoma in southern China

Nasopharyngeal carcinoma (NPC) is highly incident in southern China, where 40% of world's new cases arise each year. Detection of Epstein–Barr virus (EBV) DNA load in nasopharyngeal (NP) brush/swab samples has gradually been established as a method for diagnosis of NPC. However, its applicable value in NPC diagnosis has never been investigated in southern China. It is important to explore whether such a test could be applicable to our local population. A total of 245 consecutive participants undergoing NP brushing examination were recruited to obtain the NP brushing samples in this study. Quantitative PCR assays were used to obtain the EBV DNA load. Mann–Whitney, ANOVA and receiver operating characteristic tests were used to analyze its diagnostic value. NP brushing samples from NPC patients showed extremely high levels of EBV DNA load (mean = 46360 copy/ng DNA) compared to its expression from non-NPC control (mean = 28 copy/ng DNA) and high-risk control (mean = 50 copy/ng DNA) groups. It produced 96% sensitivity and 97% specificity, at the COV = 225 copy/ng DNA. Furthermore, EBV DNA load could reflect disease progress. Our data showed a better performance of EBV DNA load in NP brushing samples compared with an initial biopsy, immunoglobulin A (IgA) antibody titers to viral capsid antigen in serum and EBV DNA load in plasma. Detection of EBV DNA load in NP brushing samples could be an effective supplement for NPC diagnosis. Being minimally invasive and low cost, NP brush sampling combined with EBV DNA detection demonstrates great potential for screening high-risk populations for NPC.

Characterization of the nasopharyngeal carcinoma methylome identifies aberrant disruption of key signaling pathways and methylated tumor suppressor genes

AIMS

Nasopharyngeal carcinoma (NPC) is a common tumor consistently associated with Epstein-Barr virus infection and prevalent in South China, including Hong Kong, and southeast Asia. Current genomic sequencing studies found only rare mutations in NPC, indicating its critical epigenetic etiology, while no epigenome exists for NPC as yet.

MATERIALS & METHODS

We profiled the methylomes of NPC cell lines and primary tumors, together with normal nasopharyngeal epithelial cells, using methylated DNA immunoprecipitation (MeDIP).

RESULTS

We observed extensive, genome-wide methylation of cellular genes. Epigenetic disruption of Wnt, MAPK, TGF-β and Hedgehog signaling pathways was detected. Methylation of Wnt signaling regulators (SFRP1, 2, 4 and 5, DACT2, DKK2 and DKK3) was frequently detected in tumor and nasal swab samples from NPC patients. Functional studies showed that these genes are bona fide tumor-suppressor genes for NPC.

CONCLUSION

The NPC methylome shows a special high-degree CpG methylation epigenotype, similar to the Epstein-Barr virus-infected gastric cancer, indicating a critical epigenetic etiology for NPC pathogenesis.

Therapeutic implications of Epstein-Barr virus infection for the treatment of nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is highly endemic in certain regions including the People’s Republic of China and Southeast Asia. Its etiology is unique and multifactorial, involving genetic background, epigenetic, and environment factors, including Epstein–Barr virus (EBV) infection. The presence of EBV in all tumor cells, aberrant pattern of antibodies against EBV antigens in patient sera, and elevated viral DNA in patient circulation as well as nasopharyngeal site underline the role of EBV during NPC development. In NPC tumors, EBV expresses latency type II, where three EBV-encoded proteins, Epstein–Barr nuclear antigen 1, latent membrane protein 1 and 2 (LMP1, 2), are expressed along with BamH1-A rightward reading frame 1, Epstein–Barr virus-encoded small nuclear RNAs, and BamH1-A rightward transcripts. Among all encoded proteins, LMP1 plays a central role in the propagation of NPC. Standard treatment of NPC consists of radiotherapy with or without chemotherapy for early stage, concurrent chemoradiotherapy in locally advanced tumors, and palliative systemic chemotherapy in metastatic disease. However, this standard care has limitations, allowing recurrences and disease progression in a certain proportion of cases. Although the pathophysiological link and molecular process of EBV-induced oncogenesis are not fully understood, therapeutic approaches targeting the virus may increase the cure rate and add clinical benefit. The promising results of early phase clinical trials on EBV-specific immunotherapy, epigenetic therapy, and treatment with viral lytic induction offer new options for treating NPC.

Tumor suppressor in lung cancer 1 (TSLC1), a novel tumor suppressor gene, is implicated in the regulation of proliferation, invasion, cell cycle, apoptosis, and tumorigenicity in cutaneous squamous cell carcinoma

Tumor suppressor in lung cancer 1 (TSLC1) is tightly implicated in a variety of biological processes and plays critical roles in tumor development and progression. However, the roles of TSLC1 in cutaneous squamous cell carcinoma (CSCC) remain to be unraveled. Here, we reported the TSLC1 gene that was significantly downregulated in CSCC tissues and cells, and survival times of patients with TSLC1 at a low level were markedly lower than that at a high level (P = 0.0070). A stepwise investigation demonstrated that an elevated TSLC1 level evoked obvious proliferation and invasion inhibitions and arrested cell cycle at G0/G1 phase in A431 cells. Moreover, increase of caspase-3 activity mediated by elevated TSLC1 level induced cell apoptosis in A431 cells. Most notably, upregulation of TSLC1 expression reduced the numbers of colony formation and tumorigenicity. Collectively, our results presented herein suggest that TSLC1 as tumor suppressor may play prominent roles in development and progression of CSCC via regulation of different biological processes.

Over-expression of BCAT1, a c-Myc target gene, induces cell proliferation, migration and invasion in nasopharyngeal carcinoma

BACKGROUND

Nasopharyngeal carcinoma (NPC) is a common malignant tumor in southern China and Southeast Asia, but its molecular mechanisms of pathogenesis are poorly understood. Our previous work has demonstrated that BCAT1 mRNA is over expressed in NPC and knocking down its expression in 5-8F NPC cell line can potently inhibit cell cycle progression and cell proliferation. However, the mechanism of BCAT1 up-regulation and its functional role in NPC development remain to be elucidated yet.

METHODS

Immunohistochemistry (IHC) method was utilized to detect the expression of BCAT1 protein in NPC at different pathological stages. The roles of gene mutation, DNA amplification and transcription factor c-Myc in regulating BCAT1 expression were analyzed using PCR-sequencing, quantitative polymerase chain reaction (qPCR), IHC, ChIP and luciferase reporter system, respectively. The functions of BCAT1 in colony formation, cell migration and invasion properties were evaluated by RNA interference (RNAi).

RESULTS

The positive rates of BCAT1 protein expression in normal epithelia, low-to-moderate grade atypical hyperplasia tissues, high-grade atypical hyperplasia tissues and NPC tissues were 23.6% (17/72), 75% (18/24), 88.9% (8/9) and 88.8% (71/80), respectively. Only one SNP site in exon1 was detected, and 42.4% (12/28) of the NPC tissues displayed the amplification of microsatellite loci in BCAT1. C-Myc could directly bind to the c-Myc binding site in promoter region of BCAT1 and up-regulate its expression. The mRNA and protein of c-Myc and BCAT1 were co-expressed in 53.6% (15/28) and 59.1% (13/22) of NPC tissues, respectively, and BCAT1 mRNA expression was also down-regulated in c-Myc knockdown cell lines. In addition, BCAT1 knockdown cells demonstrated reduced proliferation and decreased cell migration and invasion abilities.

CONCLUSIONS

Our study indicates that gene amplification and c-Myc up-regulation are responsible for BCAT1 overexpression in primary NPC, and overexpression of BCAT1 induces cell proliferation, migration and invasion. The results suggest that BCAT1 may be a novel molecular target for the diagnosis and treatment of NPC.

Detection of cancer-specific epigenomic changes in biofluids: powerful tools in biomarker discovery and application

The genetic and epigenetic material originating from tumour that can be found in body fluids of individuals with cancer harbours tumour-specific alterations and represents an attractive target for biomarker discovery. Epigenetic changes (DNA methylation, histone modifications and non-coding RNAs) are present ubiquitously in virtually all types of human malignancies and may appear in early cancer development, and thus they provide particularly attractive markers with broad applications in diagnostics. In addition, because changes in the epigenome may constitute a signature of specific exposure to certain risk factors, they have the potential to serve as highly specific biomarkers for risk assessment. While reliable detection of cancer-specific epigenetic changes has proven to be technically challenging, a substantial progress has been made in developing the methodologies that allow an efficient and sensitive detection of epigenomic changes using the material originating from body fluids. In this review we discuss the application of epigenomics as a tool for biomarker research, with the focus on the analysis of DNA methylation in biofluids.

Tumor suppressor genes on frequently deleted chromosome 3p in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is among the most common malignancies in southern China. Deletion of genomic DNA, which occurs during the complex pathogenesis process for NPC, represents a pivotal mechanism in the inactivation of tumor suppressor genes (TSGs). In many circumstances, loss of TSGs can be detected as diagnostic and prognostic markers in cancer. The short arm of chromosome 3 (3p) is a frequently deleted chromosomal region in NPC, with 3p21.1-21.2 and 3p25.2-26.1 being the most frequently deleted minimal regions. In recent years, our research group and others have focused on the identification and characterization of novel target TSGs at 3p, such as RASSF1A, BLU, RBMS3, and CHL1, in the development and progression of NPC. In this review, we summarize recent findings of TSGs at 3p and discuss some of these genes in detail. A better understanding of TSGs at 3p will significantly improve our understanding of NPC pathogenesis, diagnosis, and treatment.

Integrated analysis of genetic and epigenetic alterations in cancer

A proposed genetic model describing the transition from normal colonic epithelium to malignant cancer involves mutation of a number of key oncogenes and tumor suppressor genes. However, only subsets of colorectal cancers contain such mutations. Moreover, the heterogeneous pattern of tumor mutations suggests there are multiple alternative pathways leading to colonic tumorigenesis. These alternative pathways involve epigenetic alterations such as the methylation of multiple CpG islands, termed the CpG island methylator phenotype, and cancers with CpG island methylator phenotype show distinct genetic and clinicopathological features. The causes of these epigenetic alterations are still not fully understood, but exogenous pathogens such as Helicobacter pylori and Epstein-Barr virus, and the chromosomal translocations seen in leukemia, have all been shown to induce epigenetic alterations of genes.

Underlying mechanisms for LTF inactivation and its functional analysis in nasopharyngeal carcinoma cell lines

The lactoferrin (LTF) gene, located at 3p21.3, behaves like a tumor suppressor gene in diverse tumors. To elucidate the exact role of LTF in NPC, we first detected its expression level in seven NPC cell lines by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR). The results showed the mRNA level of LTF was nearly undetectable in all the seven NPC cell lines, while it could be detected in chronic nasopharyngitis tissues. Subsequently, we used methylation-specific PCR (MSP), microsatellite assay, PCR-single-strand conformation polymorphism (PCR-SSCP) and sequencing methods to examine the promoter methylation, loss of heterozygosity (LOH) and gene mutation of LTF in NPC cell lines respectively. Consequently, we found that 100% (7 of 7) of NPC cell lines were methylated in LTF promoter, only one cell line (14%, 1 of 7) had LOH and gene mutation of LTF, respectively, while LTF exhibited re-expression in all cell lines after 5-aza-dC treatment, indicating promoter methylation should be the key mechanism causing LTF downregulation in NPC cell lines. Furthermore, patched methylation assay confirmed that promoter methylation could down-regulate LTF gene expression in NPC cells. Finally, we investigated the function of LTF in NPC cell lines by gene transfection. Restoration of LTF expression in NPC cells resulted in blockage of cell cycle progression, significant inhibition of cell growth and a reduced colony-formation capacity in vitro and obviously weaker tumor formation potential in vivo. In conclusion, our data indicate LTF may participate in NPC carcinogenesis as a negative effector, that is, a tumor suppressor gene.

Signaling Transduction Network Mediated by Tumor Suppressor/Susceptibility Genes in NPC

Nasopharyngeal carcinoma (NPC) is a polygenetic disease. SPLUNC1, UBAP1, BRD7, NAG7, NOR1, NGX6 and LTF genes were found to be tumor suppressor/susceptibility genes in different stages of NPC. SPLUNC1, an early warning molecular diagnosis marker, inhibits the bacteria clone formation, and is an innated immune molecule. SPLUNC1 can negatively regulate the ERK/MAPK signaling transduction pathway to inhibit NPC cell proliferation and induce apoptosis. BRD7, a transcript regulation factor, interacts with BRD2, and promotes apoptosis induced by BRD2. Its promoter is regulated by c-Myc and SP1. BRD7 inhibits NPC cell cycle progression, preventing passage through G0/G1 by suppressing ras/MEK/ERK, Rb/E2F and Wnt signaling pathways. Abnormal activation of BRD7 is crucial to cell cycle turbulence in NPC. NGX6, a metastasis-associated protein, can negative-regulate the EGF/Ras/MAPK signaling transduction pathway, and interacts with ezrin protein to inhibit NPC cell invasion and metastasis. LTF, also a metastasis-associated protein, can negatively regulate MAPK signal transduction pathways, such as JNK2 and ERK, to inhibit NPC cell proliferation and growth. Taken together, it was found that these tumor suppressor/susceptibility genes can regulate key molecules involved in cell signal pathways such as ras/MEK/ERK, Rb/E2F and EGFR ras/MEK/MAPK, and can regulate the expression of some adhesion molecules such as ezrin, nm23 and α-catenin. According to functional genomics and signaling transduction pathways, we have described a signaling cross-talk network between the tumor suppressor/susceptibility genes involved in NPC. These tumor suppressor/susceptibility genes may be potential treatment targets for NPC in the future.

Role of DNA methylation in head and neck cancer

Head and neck cancer (HNC) is a heterogenous and complex entity including diverse anatomical sites and a variety of tumor types displaying unique characteristics and different etilogies. Both environmental and genetic factors play a role in the development of the disease, but the underlying mechanism is still far from clear. Previous studies suggest that alterations in the genes acting in cellular signal pathways may contribute to head and neck carcinogenesis. In cancer, DNA methylation patterns display specific aberrations even in the early and precancerous stages and may confer susceptibility to further genetic or epigenetic changes. Silencing of the genes by hypermethylation or induction of oncogenes by promoter hypomethylation are frequent mechanisms in different types of cancer and achieve increasing diagnostic and therapeutic importance since the changes are reversible. Therefore, methylation analysis may provide promising clinical applications, including the development of new biomarkers and prediction of the therapeutic response or prognosis. In this review, we aimed to analyze the available information indicating a role for the epigenetic changes in HNC.

Epigenetic markers for early detection of nasopharyngeal carcinoma in a high risk population

BACKGROUND

Undifferentiated nasopharyngeal carcinoma (NPC) is strongly related to Epstein-Barr virus (EBV) infection, allowing aberrant antibodies against EBV and viral DNA load as screening tools in high risk populations. Methylation analysis in the promoter of tumor suppressor genes (TSGs) may serve as a complementary marker for identifying early cases. This study determined methylation status of multiple TSGs and evaluated whether it may improve early detection.

METHODS

Nasopharyngeal brushings were taken from 53 NPC patients, 22 high risk subjects and 25 healthy EBV carriers. Corresponding NPC paraffin tissue was included. DNA was bisulfite-modified preceding analysis by methylation-specific PCR (MSP). Ten TSGs were studied.

RESULTS

NPC paraffin and brushing DNA revealed an 81.8% concordance so that MSP analysis was done using either one of both specimens. NPC samples showed methylation for individual TSGs (DAPK1 79.2%, CDH13 77.4%, DLC1 76.9%, RASSF1A 75.5%, CADM1 69.8%, p16 66.0%, WIF1 61.2%, CHFR 58.5%, RIZ1 56.6% and RASSF2A 29.2%). High risk individuals, having elevated EBV IgA and viral load, showed high frequency of methylation of CDH13, DAPK1, DLC1 and CADM1, but low frequency of methylation of p16 and WIF1 and undetectable methylation of RASSF1A, CHFR, RIZ1 and RASSF2A. Healthy subjects showed similar patterns as high risk individuals. A combination of RASSF1A and p16 gave good discrimination between NPC and non-NPC, but best results were combined analysis of five methylation markers (RASSF1A, p16, WIF1, CHFR and RIZ1) with detection rate of 98%.

CONCLUSION

Multiple marker MSP is proposed as a complementary test for NPC risk assessment in combination with EBV-based markers.

TSLC1 tumour-suppressor gene expression in canine mast cell tumours

Tumour suppressor in lung cancer-1 (TSLC1) is a tumour-suppressor gene coding for an adhesion molecule that is expressed by mast cells. Reduced TSLC1 expression is associated with a poor prognosis in several human tumours, and this study sought to investigate if TSLC1 expression could be used to predict outcome in dogs with mast cell tumours (MCTs). Sections of MCTs of different tumour grades from 45 dogs (Group 1) were immunohistochemically assessed for TSLC1 and Ki67 expression. In addition, 35 intermediate-grade MCTs (Group 2) from dogs with known clinical follow-up were immunohistochemically stained for TSLC1 and Ki67. The TSLC1 staining intensity was found to strongly inversely correlate with tumour grade for Group 1 (P = 0.002857). For Group 2 there was a trend towards dogs with lower TSLC1 scores being more likely to die from MCT-related disease (P = 0.058). The intensity of TSLC1 staining inversely correlated with Ki67 expression for both groups.

Epigenetic silencing of a proapoptotic cell adhesion molecule, the immunoglobulin superfamily member IGSF4, by promoter CpG methylation protects Hodgkin lymphoma cells from apoptosis

The malignant Hodgkin/Reed-Sternberg (HRS) cells of Hodgkin lymphoma (HL) are believed to derive from germinal center (GC) B cells, but lack expression of a functional B cell receptor. As apoptosis is the normal fate of B-cell receptor-negative GC B cells, mechanisms that abrogate apoptosis are thus critical in HL development, such as epigenetic disruption of certain pro-apoptotic cancer genes including tumor suppressor genes. Identifying methylated genes elucidates oncogenic mechanisms and provides valuable biomarkers; therefore, we performed a chemical epigenetic screening for methylated genes in HL through pharmacological demethylation and expression profiling. IGSF4/CADM1/TSLC1, a pro-apoptotic cell adhesion molecule of the immunoglobulin superfamily, was identified together with other methylated targets. In contrast to its expression in normal GC B cells, IGSF4 was down-regulated and methylated in HL cell lines, most primary HL, and microdissected HRS cells of 3/5 cases, but not in normal peripheral blood mononuclear cells and seldom in normal lymph nodes. We also detected IGSF4 methylation in sera of 14/18 (78%) HL patients but seldom in normal sera. Ectopic IGSF4 expression decreased HL cells survival and increased their sensitivity to apoptosis. IGSF4 induction that normally follows heat shock stress treatment was also abrogated in methylated lymphoma cells. Thus, our data demonstrate that IGSF4 silencing by CpG methylation provides an anti-apoptotic signal to HRS cells important in HL pathogenesis.

Nasopharyngeal carcinoma: the next challenges

Nasopharyngeal carcinoma (NPC) differs from other head and neck cancers in its aetiology, epidemiology and potential therapeutic options. Despite cure for the majority of the patients, challenges still exist in the prevention of disease relapse, treatment of patients with refractory or metastatic NPC and the management of long-term toxicities. This article discusses the specific challenges in pushing the boundaries of NPC treatments further, with an emphasis on prognostic/predictive markers, molecularly targeted therapies, immunotherapies and the areas of interest with regard to long-term toxicities arising from therapeutic interventions.

Nasopharyngeal carcinoma in adults: treatment results after long-term follow-up with special reference to adjuvant interferon-beta in undifferentiated carcinomas

Purpose

Nasopharyngeal carcinomas (NPC) are radiosensitive, and radiotherapy is the standard curative treatment. Furthermore, it has been shown that combined radiochemotherapy improves prognosis in locally advanced stages. Further encouraging results have been obtained with adjuvant interferon-beta after primary radio(chemo)therapy in childhood undifferentiated NPC. Aim of the present study was to evaluate the treatment results after long-term follow-up after radio(chemo)therapy for adult NPC with special reference to patients with undifferentiated carcinomas treated with adjuvant interferon-beta.

Patients and methods

From 02/1992 to 07/2008, 26 adult patients with NPC without distant metastases were treated (17 squamous cell carcinomas, 9 undifferentiated carcinomas). The treatment concepts changed over the years: 13 patients were treated with radiotherapy alone, 13 patients received combined radiochemotherapy. Additionally, six patients with undifferentiated carcinomas were treated with adjuvant interferon-beta after radiochemotherapy for 6 months.

Results

After a median follow-up of 96 months, 17 patients remain alive. Collectively, our 5-year overall-survival and loco-regional control rates were 74% (radiochemotherapy 81%, radiotherapy alone 68.5%) and 87% (radiochemotherapy 100%, radiotherapy alone 72.7%), respectively. All treatment regimens used were feasible; especially, adjuvant interferon-beta was applied as provided without high grade toxicity. All patients with undifferentiated carcinomas treated with adjuvant interferon-beta stayed alive until the end of the follow-up.

Conclusion

In summary, our data affirm that NPC in adults are curable by primary radio(chemo)therapy. Furthermore, our data indicate that adjuvant interferon-beta application in undifferentiated NPC in adults is feasible and shows promising results. Further prospective clinical trials are needed to finally establish adjuvant interferon beta in curative treatment of adult NPC.

Epigenetic dysregulation of the host cell genome in Epstein-Barr virus-associated neoplasia

Epstein-Barr virus (EBV), a human herpesvirus, is associated with a wide variety of malignant tumors. The expression of the latent viral RNAs is under strict, host-cell dependent transcriptional control. This results in an almost complete transcriptional silencing of the EBV genome in memory B-cells. In tumor cells, germinal center B-cells and lymphoblastoid cells, distinct viral latency promoters are active. Epigenetic mechanisms contribute to this strict control. In EBV-infected cells, epigenetic mechanisms also alter the expression of cellular genes, including tumor suppressor genes. In Nasopharyngeal Carcinoma, the hypermethylation of certain cellular promoters is attributed to the upregulation of DNA methyltransferases by the viral oncoprotein LMP1 (latent membrane protein 1) via JNK/AP1-signaling. The role of other viral latency products in the epigenetic dysregulation of the cellular genome remains to be established. Analysis of epigenetic alterations in EBV-associated neoplasms may result in a better understanding of their pathogenesis and may facilitate the development of new therapies.

Inactivation of LARS2, located at the commonly deleted region 3p21.3, by both epigenetic and genetic mechanisms in nasopharyngeal carcinoma

Allelic loss of chromosome 3p, including the 3p21.3 region, is found in 95-100% of primary nasopharyngeal carcinoma (NPC) biopsies, suggesting that this region should harbor some tumor suppressor genes (TSGs) closely related to NPC development. Several TSGs located at 3p21.3, such as RASSF1A, LTF and BLU, have been demonstrated to be involved in NPC development. LARS2 (leucyl-tRNA synthetase 2, mitochondrial) is another gene located in the chromosome 3 common eliminated region-1 (C3CER1) at 3p21.3. In this study, we focussed on the epigenetic and genetic alterations of LARS2 in NPC. The mRNA expression of LARS2 was detected in 36 NPC and 8 chronic nasopharyngitis (NP) tissues by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) and real-time RT-PCR. Subsequently, the mutation, allelic loss, and methylation status of LARS2 were analysed by polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP), homozygous deletion (HD) analysis and methylation-specific polymerase chain reaction in primary NPC tissues. No expression or downregulation of LARS2 was observed in 78% of primary NPC tissues. No mutations, assessed by PCR-SSCP and DNA sequencing, were found in the promoter region and exon 1 of LARS2 in NPC tissues, whereas HD was detected in 28% of NPC specimens at the LARS2 locus. In addition, hypermethylation of LARS2 was found in 64% of NPC samples but only in 12.5% of NP biopsies. Our data indicate that inactivation of LARS2 by both genetic and epigenetic mechanisms may be a common and important event in the carcinogenesis of NPC.

The DLC-1 -29A/T polymorphism is not associated with nasopharyngeal carcinoma risk in Chinese population

Deleted in liver cancer-1 (DLC-1), encoding a Rho GTPase-activating protein (GAP), is considered as a promising candidate tumor suppressor gene in nasopharyngeal carcinoma (NPC). The single-nucleotide polymorphism (SNP) -29A/T upstream of ATG start codon was found when gene mutation profile of DLC-1 in NPC was analyzed. To evaluate the correlation between SNP -29A/T in the promoter region of DLC-1 gene and risk of NPC, a total of 521 samples from a Chinese population, including 320 healthy individuals and 201 NPC patients, were collected for SNP analysis by PCR-single-strand conformation polymorphism and sequencing. The differences in allele and genotype frequencies between NPC patients and controls were tested using logistic regression statistical method. No significant differences were found in allele or genotype frequencies between NPC patients and controls or among different NPC clinical stages. Hence, our data indicate that the SNP -29A/T of DLC-1 gene is not associated with NPC susceptibility.

An Epstein-Barr virus-encoded microRNA targets PUMA to promote host cell survival

Epstein-Barr virus (EBV) is a herpesvirus associated with nasopharyngeal carcinoma (NPC), gastric carcinoma (GC), and other malignancies. EBV is the first human virus found to express microRNAs (miRNAs), the functions of which remain largely unknown. We report on the regulation of a cellular protein named p53 up-regulated modulator of apoptosis (PUMA) by an EBV miRNA known as miR-BART5, which is abundantly expressed in NPC and EBV-GC cells. Modulation of PUMA expression by miR-BART5 and anti–miR-BART5 oligonucleotide was demonstrated in EBV-positive cells. In addition, PUMA was found to be significantly underexpressed in ∼60% of human NPC tissues. Although expression of miR-BART5 rendered NPC and EBV-GC cells less sensitive to proapoptotic agents, apoptosis can be triggered by depleting miR-BART5 or inducing the expression of PUMA. Collectively, our findings suggest that EBV encodes an miRNA to facilitate the establishment of latent infection by promoting host cell survival.

Promoter methylation inhibits BRD7 expression in human nasopharyngeal carcinoma cells

BACKGROUND

Nasopharyngeal carcinoma (NPC) is a head and neck malignancy with high occurrence in South-East Asia and Southern China. Recent findings suggest that epigenetic inactivation of multiple tumor suppressor genes plays an important role in the tumourigenesis of NPC. BRD7 is a NPC-associated bromodomain gene that exhibits a much higher-level of mRNA expression in normal than in NPC biopsies and cell lines. In this study, we explored the role of DNA methylation in regulation of BRD7 transcription.

METHODS

The presence of CpG islands within BRD7 promoter was predicted by EMBOSS CpGplot and Softberry CpGFinder, respectively. Nested methylation-specific PCR and RT-PCR were employed to detect the methylation status of BRD7 promoter and the mRNA expression of BRD7 gene in tumor cell lines as well as clinical samples. Electrophoretic mobility shift assays (EMSA) and luciferase assay were used to detect the effects of cytosine methylation on the nuclear protein binding to BRD7 promoter.

RESULTS

We found that DNA methylation suppresses BRD7 expression in NPC cells. In vitro DNA methylation in NPC cells silenced BRD7 promoter activity and inhibited the binding of the nuclear protein (possibly Sp1) to Sp1 binding sites in the BRD7 promoter. In contrast, inhibition of DNA methylation augments induction of endogenous BRD7 mRNA in NPC cells. We also found that methylation frequency of BRD7 promoter is much higher in the tumor and matched blood samples from NPC patients than in the blood samples from normal individuals.

CONCLUSION

BRD7 promoter demethylation is a prerequisite for high level induction of BRD7 gene expression. DNA methylation of BRD7 promoter might serve as a diagnostic marker in NPC.

Nasopharyngeal carcinoma: the role of the Epstein-Barr virus

Nasopharyngeal carcinoma (NPC) arises from the epithelium of the nasopharynx and is a rare tumor in most parts of the world, including the United States. Neck swelling, nasal obstruction, and epistaxis are the most common presenting symptoms. The etiology of NPC is multifactorial and includes genetic susceptibility, exposure to carcinogens, and prior infection with the Epstein-Barr virus (EBV). We report a case of a 16-year-old African-American male who presented with hemoptysis and a 3-month history of a neck mass. Diagnostic evaluation identified a nasopharyngeal mass that upon biopsy was shown to be an undifferentiated nasopharyngeal carcinoma with immunohistochemical stains markedly positive for EBV. Recent studies have further elucidated the role of EBV in the pathogenesis of NPC and have demonstrated the utility of EBV studies in staging, prognosis, and post-therapeutic monitoring.

Transcriptional patterns, biomarkers and pathways characterizing nasopharyngeal carcinoma of Southern China

BACKGROUND

The pathogenesis of nasopharyngeal carcinoma (NPC) is a complicated process involving genetic predisposition, Epstein-Bar Virus infection, and genetic alterations. Although some oncogenes and tumor suppressor genes have been previously reported in NPC, a complete understanding of the pathogenesis of NPC in the context of global gene expression, transcriptional pathways and biomarker assessment remains to be elucidated.

METHODS

Total RNA from 32 pathologically-confirmed cases of poorly-differentiated NPC was divided into pools inclusive of four consecutive specimens and each pool (T1 to T8) was co-hybridized with pooled RNA from 24 normal non-cancerous nasopharyngeal tissues (NP) to a human 8K cDNA array platform. The reliability of microarray data was validated for selected genes by semi-quantitative RT-PCR and immunohistochemistry.

RESULTS

Stringent statistical filtering parameters identified 435 genes to be up-regulated and 257 genes to be down-regulated in NPC compared to NP. Seven up-regulated genes including CYC1, MIF, LAMB3, TUBB2, UBE2C and TRAP1 had been previously proposed as candidate common cancer biomarkers based on a previous extensive comparison among various cancers and normal tissues which did not, however, include NPC or NP. In addition, nine known oncogenes and tumor suppressor genes, MIF, BIRC5, PTTG1, ATM, FOXO1A, TGFBR2, PRKAR1A, KLF5 and PDCD4 were identified through the microarray literature-based annotation search engine MILANO, suggesting these genes may be specifically involved in the promotion of the malignant conversion of nasopharyngeal epithelium. Finally, we found that these differentially expressed genes were involved in apoptosis, MAPK, VEGF and B cell receptor signaling pathways and other functions associated with cell growth, signal transduction and immune system activation.

CONCLUSION

This study identified potential candidate biomarkers, oncogenes/tumor suppressor genes involved in several pathways relevant to the oncogenesis of NPC. This information may facilitate the determination of diagnostic and therapeutic targets for NPC as well as provide insights about the molecular pathogenesis of NPC.

Epstein-Barr virus latent membrane protein 1 suppresses the growth-inhibitory effect of retinoic acid by inhibiting retinoic acid receptor-beta2 expression via DNA methylation

Epigenetic alteration through DNA methylation in retinoic acid receptor-beta2 (RAR-beta2) is common in human tumors including nasopharyngeal carcinoma (NPC); however, the mechanism and its biological significance are unknown. Here, we report that the Epstein-Barr virus (EBV) oncogene product, latent membrane protein 1 (LMP1), induces promoter hypermethylation of RAR-beta2 via up-regulation of DNA methyltransferases 1, 3a, and 3b, leading to decrease in RAR-beta2 expression in NPC cells. In addition, LMP1 abolished the potentials of retinoic acid (RA) to down-regulate Cdk2 and Cdk4 and to up-regulate p16, p21, and p27, resulting in activation of E2F1 in the presence of RA. As a consequence, LMP1 could abrogate the growth-inhibitory effect of RA by releasing cell cycle arrest at G1 phase. Considering that RAR-beta2 is a major executor of the anti-tumor potentials of retinoids, its down-regulation by LMP1 might play an important role during EBV-mediated tumorigenesis.

Proteomic comparison of nasopharyngeal cancer cell lines C666-1 and NP69 identifies down-regulation of annexin II and beta2-tubulin for nasopharyngeal carcinoma

CONTEXT

Nasopharyngeal carcinoma (NPC), common in southern China and North Africa, has a complex etiology involving interplay between viral, environmental, and hereditary factors and is almost constantly associated with the Epstein-Barr virus. Since the prognosis of locally advanced and metastatic diseases is poor, increased understanding of the pathogenesis of NPC would be important for discovering novel markers for patients' management.

OBJECTIVES

To compare the proteomic expression profile between an Epstein-Barr virus-associated NPC cell line (C666-1) and a normal NP cell line (NP69). The proteins with differential expression were analyzed in 40 undifferentiated NPC paraffin-embedded specimens.

DESIGN

Differentially expressed proteins discovered between the two cell lines were identified by mass spectrometry. After confirmation by immunocytochemical staining, their expression in patient samples was measured using 40 pairs of undifferentiated NPCs together with their adjacent normal epithelia.

RESULTS

Proteomic findings indicated that adenosine triphosphate synthase alpha chain was up-regulated, whereas annexin II, annexin V, beta(2)-tubulin, and profilin 1 were down-regulated. After confirming the results in agar-processed cell lines, annexin II and beta(2)-tubulin expression were found to be lower in tumor cells than in adjacent normal epithelial cells in 100% and 90% of the patients' specimens, respectively. Finally, annexin II down-regulation was positively associated with lymph node metastasis, suggesting that it may be a prognostic factor in NPC.

CONCLUSIONS

The results suggest that annexin II and beta(2)-tubulin down-regulation is important in NPC formation and may represent potential targets for further investigations.

Epigenetic and genetic alterations of the EDNRB gene in nasopharyngeal carcinoma

BACKGROUND

Loss of heterozygosity (LOH) at 13q22 is a common event in nasopharyngeal carcinoma (NPC). EDNRB gene located at 13q22 has been demonstrated to be hypermethylated in some kinds of tumors. In the current study, we focused on the epigenetic and genetic alterations of EDNRB in NPC.

METHODS

The mRNA expression of EDNRB was detected by semiquantitative RT-PCR and real-time quantitative PCR in 49 NPC and 12 chronic nasopharyngitis biopsies. The methylation and LOH status of EDNRB were examined by methylation-specific polymerase chain reaction, microsatellite PCR and sequencing. We also examined the mRNA expression of EDNRB in four NPC cell lines after 5-aza-2'-deoxycytidine treatment.

RESULTS

EDNRB was downregulated in primary NPC tissues and NPC cell lines, and a relatively higher methylation level of EDNRB was found in NPC biopsies (84%) compared to that in chronic nasopharyngitis biopsies (42%). Treatment of NPC cell lines with 5-aza-2'-deoxycytidine activated EDNRB expression. LOH of EDNRB gene was also found at two microsatellite sites with ratios of 6.25 and 16.67% in NPC.

CONCLUSION

Our results suggested that EDNRB expression may be affected by aberrant promoter methylation and gene deletion and may play a role in the development of NPC.