Molecular cytogenetic characterization of nasopharyngeal carcinoma cell lines and xenografts by comparative genomic hybridization and spectral karyotyping

Nonkeratinizing Nasopharyngeal Carcinoma, Undifferentiated Type With Trisomy 2: A Case Report and Short Review of Cytogenetic and Molecular Literature

Carcinoma originating from the surface epithelium of the nasopharynx is classified by the World Health Organization (WHO) as nasopharyngeal carcinoma (NPC) and has 3 main types: keratinizing squamous cell carcinoma (WHO type 1) and nonkeratinizing carcinoma, differentiated (WHO type II), and undifferentiated (WHO type III). Nonkeratinizing NPC is strongly associated with prior Epstein-Barr virus (EBV) infection. These tumors may be divided into differentiated and undifferentiated carcinoma. Histologically, the tumor is characterized by syncytia of large malignant cells with vesicular nuclei, conspicuous nucleoli, and easily observed mitotic figures. We report a case of a 14-year-old boy diagnosed with EBV and human papillomavirus (HPV)-positive NPC (WHO type 3) with cytogenetics showing the presence of mosaic trisomy 2. This case report brings to light a rare cytogenetic aberration to our knowledge only reported once before in the literature in a xenograft model.

Advances in targeted therapy mainly based on signal pathways for nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a malignant epithelial carcinoma of the head and neck region which mainly distributes in southern China and Southeast Asia and has a crucial association with the Epstein-Barr virus. Based on epidemiological data, both incidence and mortality of NPC have significantly declined in recent decades grounded on the improvement of living standard and medical level in an endemic region, in particular, with the clinical use of individualized chemotherapy and intensity-modulated radiotherapy (IMRT) which profoundly contributes to the cure rate of NPC patients. To tackle the challenges including local recurrence and distant metastasis in the current NPC treatment, we discussed the implication of using targeted therapy against critical molecules in various signal pathways, and how they synergize with chemoradiotherapy in the NPC treatment. Combination treatment including targeted therapy and IMRT or concurrent chemoradiotherapy is presumably to be future options, which may reduce radiation or chemotherapy toxicities and open new avenues for the improvement of the expected functional outcome for patients with advanced NPC.

Epstein-Barr virus particles induce centrosome amplification and chromosomal instability

Infections with Epstein–Barr virus (EBV) are associated with cancer development, and EBV lytic replication (the process that generates virus progeny) is a strong risk factor for some cancer types. Here we report that EBV infection of B-lymphocytes (in vitro and in a mouse model) leads to an increased rate of centrosome amplification, associated with chromosomal instability. This effect can be reproduced with virus-like particles devoid of EBV DNA, but not with defective virus-like particles that cannot infect host cells. Viral protein BNRF1 induces centrosome amplification, and BNRF1-deficient viruses largely lose this property. These findings identify a new mechanism by which EBV particles can induce chromosomal instability without establishing a chronic infection, thereby conferring a risk for development of tumours that do not necessarily carry the viral genome.

Infection with Epstein–Barr virus (EBV) is associated with increased risk of cancer development. Here the authors show that EBV particles, and more specifically the viral protein BNRF1, induce centrosome amplification and chromosomal instability in host cells in the absence of chronic infection.

Epstein-Barr virus-positive T/NK-cell lymphoproliferative disorders

Epstein–Barr virus, a ubiquitous human herpesvirus, can induce both lytic and latent infections that result in a variety of human diseases, including lymphoproliferative disorders. The oncogenic potential of Epstein–Barr virus is related to its ability to infect and transform B lymphocytes into continuously proliferating lymphoblastoid cells. However, Epstein–Barr virus has also been implicated in the development of T/natural killer cell lymphoproliferative diseases. Epstein–Barr virus encodes a series of products that mimic several growth, transcription and anti-apoptotic factors, thus usurping control of pathways that regulate diverse homeostatic cellular functions and the microenvironment. However, the exact mechanism by which Epstein–Barr virus promotes oncogenesis and inflammatory lesion development remains unclear. Epstein–Barr virus-associated T/natural killer cell lymphoproliferative diseases often have overlapping clinical symptoms as well as histologic and immunophenotypic features because both lymphoid cell types derive from a common precursor. Accurate classification of Epstein–Barr virus-associated T/natural killer cell lymphoproliferative diseases is a prerequisite for appropriate clinical management. Currently, the treatment of most T/natural killer cell lymphoproliferative diseases is less than satisfactory. Novel and targeted therapies are strongly required to satisfy clinical demands. This review describes our current knowledge of the genetics, oncogenesis, biology, diagnosis and treatment of Epstein–Barr virus-associated T/natural killer cell lymphoproliferative diseases.

Nasopharyngeal Carcinoma: An Evolving Role for the Epstein-Barr Virus

The Epstein-Barr herpesvirus (EBV) is an important human pathogen that is closely linked to several major malignancies including the major epithelial tumor, undifferentiated nasopharyngeal carcinoma (NPC). This important tumor occurs with elevated incidence in specific areas, particularly in southern China but also in Mediterranean Africa and some regions of the Middle East. Regardless of tumor prevalence, undifferentiated NPC is consistently associated with EBV. The consistent detection of EBV in all cases of NPC, the maintenance of the viral genome in every cell, and the continued expression of viral gene products suggest that EBV is a necessary factor for the malignant growth in vivo. However, the molecular characterization of the infection and identification of critical events have been hampered by the difficulty in developing in vitro models of NPC. Epithelial cell infection is difficult in vitro and in contrast to B-cell infection does not result in immortalization and transformation. Cell lines established from NPC usually do not retain the genome, and the successful establishment of tumor xenografts is difficult. However, critical genetic changes that contribute to the onset and progression of NPC and key molecular properties of the viral genes expressed in NPC have been identified. In some cases, viral expression becomes increasingly restricted during tumor progression and tumor cells may express only the viral nuclear antigen EBNA1 and viral noncoding RNAs. As NPC develops in the immunocompetent, the continued progression of deregulated growth likely reflects the combination of expression of viral oncogenes in some cells and viral noncoding RNAs that likely function synergistically with changes in cellular RNA and miRNA expression.

Identification of a recurrent transforming UBR5-ZNF423 fusion gene in EBV-associated nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a distinct type of head and neck cancer which is prevalent in southern China, south-east Asia and northern Africa. The development and stepwise progression of NPC involves accumulation of multiple gross genetic changes during the clonal expansion of Epstein–Barr virus (EBV)-infected nasopharyngeal epithelial cell population. Here, using paired-end whole-transcriptome sequencing, we discovered a number of chimeric fusion transcripts in a panel of EBV-positive tumour lines. Among these transcripts, a novel fusion of ubiquitin protein ligase E3 component n-recognin 5 (UBR5) on 8q22.3 and zinc finger protein 423 (ZNF423) on 16q12.1, identified from the NPC cell line C666-1, was recurrently detected in 12/144 (8.3%) of primary tumours. The fusion gene contains exon 1 of UBR5 and exons 7–9 of ZNF423 and produces a 94 amino acid chimeric protein including the original C-terminal EBF binding domain (ZF29-30) of ZNF423. Notably, the growth of NPC cells with UBR5–ZNF423 rearrangement is dependent on expression of this fusion protein. Knock-down of UBR5–ZNF423 by fusion-specific siRNA significantly inhibited the cell proliferation and colony-forming ability of C666-1 cells. The transforming ability of UBR5–ZNF423 fusion was also confirmed in NIH3T3 fibroblasts. Constitutive expression of UBR5–ZNF423 in NIH3T3 fibroblasts significantly enhanced its anchorage-independent growth in soft agar and induced tumour formation in a nude mouse model. These findings suggest that expression of UBR5–ZNF423 protein might contribute to the transformation of a subset of NPCs, possibly by altering the activity of EBFs (early B cell factors). Identification of the oncogenic UBR5–ZNF423 provides new potential opportunities for therapeutic intervention in NPC. © 2013 The Authors. Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

MicroRNA-550a acts as a pro-metastatic gene and directly targets cytoplasmic polyadenylation element-binding protein 4 in hepatocellular carcinoma

MicroRNAs (miRNAs) are a class of small, non-coding RNA molecules that are often found at chromosomal breakpoints and play a vital role in human cancer. Our previous study found that miR-550a, a frequently amplified miRNA on 7p14.3, was upregulated in hepatocellular carcinoma (HCC). However, the possible functions and molecular mechanisms of miR-550a in HCC remain unknown. In this study, gain-of-function and loss-of-function assays revealed that miR-550a markedly promoted HCC cell migration and invasion. In addition, we discovered that cytoplasmic polyadenylation element binding protein 4 (CPEB4) was a potential target of miR-550a in HCC. Further analyses showed that knockdown of CPEB4 expression significantly facilitated HCC cell migration and invasion, which phenocopied the effects of miR-550a on HCC cells. Moreover, a decrease in CPEB4 expression mediated miR-550a-induced liver cancer cell migration and invasion. Interestingly, CPEB4 is frequently downregulated in HCC, and its expression levels correlate with the overall survival of HCC patients. Together, these results suggested that this newly identified miR-550a-CPEB4 axis may be involved in HCC cell metastasis. Moreover, the expression levels of CPEB4 could be used to predict outcomes in HCC patients. Our findings provide novel potential targets for HCC therapy and prognosis.

miR-145 is differentially regulated by TGF-β1 and ischaemia and targets Disabled-2 expression and wnt/β-catenin activity

The effect of wnt/β-catenin signalling in the response to acute myocardial infarction (AMI) remains controversial. The membrane receptor adaptor protein Disabled-2 (Dab2) is a tumour suppressor protein and has a critical role in stem cell specification. We recently demonstrated that down-regulation of Dab2 regulates cardiac protein expression and wnt/β-catenin activity in mesenchymal stem cells (MSC) in response to transforming growth factor-β(1) (TGF-β(1)). Although Dab2 expression has been shown to have effects in stem cells and tumour suppression, the molecular mechanisms regulating this expression are still undefined. We identified putative binding sites for miR-145 in the 3'-UTR of Dab2. In MSC in culture, we observed that TGF-β(1) treatment led to rapid and sustained up-regulation of pri-miR-145. Through gain and loss of function studies we demonstrate that miR-145 up-regulation was required for the down-regulation of Dab2 and increased β-catenin activity in response to TGF-β(1). To begin to define how Dab2 might regulate wnt/β-catenin in the heart following AMI, we quantified myocardial Dab2 as a function of time after left anterior descending ligation. There was no significant Dab2 expression in sham-operated myocardium. Following AMI, Dab2 levels were rapidly up-regulated in cardiac myocytes in the infarct border zone. The increase in cardiac myocyte Dab2 expression correlated with the rapid and sustained down-regulation of myocardial pri-miR-145 expression following AMI. Our data demonstrate a novel and critical role for miR-145 expression as a regulator of Dab2 expression and β-catenin activity in response to TGF-β(1) and hypoxia.

Deciphering the molecular genetic basis of NPC through molecular, cytogenetic, and epigenetic approaches

Nasopharyngeal carcinoma (NPC) is consistently associated with EBV infection and prevalence in southern China and Southeast Asia. In addition to EBV, the development of NPC involves cumulative genetic and epigenetic changes influenced by predisposing genetic factors and environmental carcinogens. Over the past two decades, knowledge of genetic and epigenetic alterations of NPC has rapidly accumulated. Multiple chromosomal abnormalities (e.g. copy number changes on chromosomes 3p, 9p, 11q, 12p, and 14q), gene alterations (e.g. p16 deletion and LTBR amplification), and epigenetic changes (e.g. RASSF1A and TSLC1 methylation) have been identified by various genome-wide approaches, such as allelotyping, CGH, and microarray analysis. In this review, we will discuss the critical genetic events that contribute to the initiation and progression of NPC. Studies on the precancerous lesions and in vitro immortalized nasopharyngeal epithelial cell models provide important evidence for the involvement of genetic alterations and EBV infection in early development of this cancer. A hypothetical model describing the role of EBV latent infection and multiple genetic changes in NPC tumorigenesis is proposed.

The progress on genetic analysis of nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a rare malignancy in most parts of the world, but is one of the most common cancers in Southeast Asia. Both genetic and environmental factors contribute to the tumorigenesis of NPC, most notably the consumption of certain salted food items and Epstein-Barr virus infection. This review will focus on the current progress of the genetic analysis of NPC (genetic susceptibilities and somatic alterations). We will review the current advances in genomic technologies and their shaping of the future direction of NPC research.

Putative tumour-suppressor gene DAB2 is frequently down regulated by promoter hypermethylation in nasopharyngeal carcinoma

Background

Human Disabled-2 (DAB2), is a multi-function signalling molecule that it is frequently down-regulated in human cancers. We aimed to investigate the possible tumour suppressor effect of DAB2 in nasopharyngeal carcinoma (NPC).

Methods

We studied the expression of DAB2 in NPC cell lines, xenografts and primary tumour samples. The status of promoter methylation was assessed by methylation specific PCR and bisulfite sequencing. The functional role of DAB2 in NPC was investigated by re-introducing DAB2 expression into NPC cell line C666-1.

Results

Decrease or absent of DAB2 transcript was observed in NPC cell lines and xenografts. Loss of DAB2 protein expression was seen in 72% (33/46) of primary NPC as demonstrated by immunohistochemistry. Aberrant DAB2 promoter methylation was detected in 65.2% (30/46) of primary NPC samples by methylation specific PCR. Treatment of the DAB2 negative NPC cell line C666-1 with 5-aza-2'-deoxycytidine resulted in restoration of DAB2 expression in a dose-dependent manner. Overexpression of DAB2 in NPC cell line C666-1 resulted in reduced growth rate and 35% reduction in anchorage-dependent colony formation, and inhibition of serum-induced c-Fos expression compared to vector-transfected controls. Over expression of DAB2 resulted in alterations of multiple pathways as demonstrated by expression profiling and functional network analysis, which confirmed the role of DAB2 as an adaptor molecule involved in multiple receptor-mediated signalling pathways.

Conclusions

We report the frequent down regulation of DAB2 in NPC and the promoter hypermethylation contributes to the loss of expression of DAB2. This is the first study demonstrating frequent DAB2 promoter hypermethylation in human cancer. Our functional studies support the putative tumour suppressor effect of DAB2 in NPC cells.

Reverse phase protein array identifies novel anti-invasion mechanisms of YC-1

YC-1 has recently been demonstrated to have potent anti-invasion and anti-metastatic activity in several cancer models, in addition to its anti-proliferation activity. However, the mechanism underlying its anti-invasion/anti-metastatic activity is largely unknown. Nasopharyngeal carcinoma (NPC) is a highly metastatic head and neck cancer in Southeast Asia. Here, we demonstrated that YC-1 inhibited invasiveness and proliferation of NPC cells, with the latter being accompanied by PARP cleavage, S-phase arrest and activation of Chk1/Chk2. We aimed at identifying novel anti-invasion mechanisms of YC-1 in NPC by a functional proteomic platform, the reverse phase protein array (RPPA). Our study revealed for the first time that multiple invasion-related signaling proteins (beta-catenin, caveolin, Src and EGFR), as well as several growth-related proteins (AMPKalpha, phospho-acetyl-CoA carboxylase (p-ACC), HER-2 and mTOR), which were previously un-described signaling proteins altered by YC-1, were found to be down-modulated by YC-1 in NPC cells. We hypothesized that YC-1-mediated downregulation of these invasion proteins contributed to its anti-invasion activity in NPC cells. Overexpression of EGFR, activated Src or caveolin, but not beta-catenin reversed the inhibitory effects of YC-1 on NPC cell invasion, with EGFR and activated Src having additional effects on rescuing NPC cells from YC-1-mediated growth inhibition. In summary, we have identified several novel anti-invasion mechanisms of YC-1 that could impact NPC, and possibly other cancers as well.

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.

Nasopharyngeal carcinoma: molecular pathogenesis and therapeutic developments

Nasopharyngeal carcinoma (NPC) is a prevalent tumour in southern China and southeast Asia, particularly in the Cantonese population, where its incidence has remained high for decades. Recent studies have demonstrated that the aetiology of NPC is complex, involving multiple factors including genetic susceptibility, infection with the Epstein-Barr virus (EBV) and exposure to chemical carcinogens. During development of the disease, viral infection and multiple somatic genetic and epigenetic changes synergistically disrupt normal cell function, thus contributing to NPC pathogenesis. NPC is highly radiosensitive and chemosensitive, but treatment of patients with locoregionally advanced disease remains problematic. New biomarkers for NPC, including EBV DNA copy number or methylation of multiple tumour suppressor genes, which can be detected in serum and nasopharyngeal brushings, have been developed for the molecular diagnosis of this tumour. Meanwhile, new therapeutic strategies such as intensity-modulated radiation therapy and immuno- and epigenetic therapies might lead to more specific and effective treatments.

Spectral karyotyping of human, mouse, rat and ape chromosomes--applications for genetic diagnostics and research

Spectral karyotyping (SKY) is a widely used methodology to identify genetic aberrations. Multicolor fluorescence in situ hybridization using chromosome painting probes in individual colors for all metaphase chromosomes at once is combined with a unique spectral measurement and analysis system to automatically classify normal and aberrant chromosomes. Based on countless studies and investigations in many laboratories worldwide, numerous new chromosome translocations and other aberrations have been identified in clinical and tumor cytogenetics. Thus, gene identification studies have been facilitated resulting in the dissection of tumor development and progression. For example, different translocation partners of the TEL/ETV6 transcription factor that is specially required for hematopoiesis within the bone marrow were identified. Also, the correct classification of complex karyotypes of solid tumors supports the prognostication of cancer patients. Important accomplishments for patients with genetic diseases, leukemias and lymphomas, mesenchymal tumors and solid cancers are summarized and exemplified. Furthermore, studies of disease mechanisms such as centromeric DNA breakage, DNA double strand break repair, telomere shortening and radiation-induced neoplastic transformation have been accompanied by SKY analyses. Besides the hybridization of human chromosomes, mouse karyotyping has also contributed to the comprehensive characterization of mouse models of human disease and for gene therapy studies.

Chromosomal imbalances in nasopharyngeal carcinoma: a meta-analysis of comparative genomic hybridization results

Nasopharyngeal carcinoma (NPC) is a highly prevalent disease in Southeast Asia and its prevalence is clearly affected by genetic background. Various theories have been suggested for its high incidence in this geographical region but to these days no conclusive explanation has been identified. Chromosomal imbalances identifiable through comparative genomic hybridization may shed some light on common genetic alterations that may be of relevance to the onset and progression of NPC. Review of the literature, however, reveals contradictory results among reported findings possibly related to factors associated with patient selection, stage of disease, differences in methodological details etc. To increase the power of the analysis and attempt to identify commonalities among the reported findings, we performed a meta-analysis of results described in NPC tissues based on chromosomal comparative genomic hybridization (CGH). This meta-analysis revealed consistent patters in chromosomal abnormalities that appeared to cluster in specific "hot spots" along the genome following a stage-dependent progression.

Characterization of 3p, 5p, and 3q in two nasopharyngeal carcinoma cell lines, using region-specific multiplex fluorescence in situ hybridization probes

Amplification of chromosome arms 3q and 5p and deletion of 3p were frequently detected in nasopharyngeal carcinoma (NPC) with comparative genomic hybridization and loss of heterozygosity studies. To identify the minimal amplified or deleted regions in these arms, structural aberrations in chromosome arms 3p, 3q, and 5p in two NPC cell lines, CNE1 and SUNE1, were studied with multiplex-color FISH (M-FISH) and chromosome region-specific probes (CRP). All CRPs, which were generated from microdissected DNA, were specific and strong in intensity, and sensitive enough to detect chromosome aberrations including translocations, deletions, and amplifications of target regions. In these two NPC cell lines, minimal regions of deletion and amplification were found at 3p12 and 3q26 approximately q27, respectively. On 5p, most of the regions were amplified as intact copies. Interregion translocations of these three arms were also observed. The amplification on 3q26 approximately q27 provided useful hints for further screening the minimal amplification at RP11-115J24 (3q26.2), containing candidate oncogene eIF-5A2. M-FISH with CRPs is thus not only useful in revealing a comprehensive picture of structural aberrations in target chromosomes, but also in narrowing down the minimal region for screening cancer-related genes.

Les carcinomes du nasopharynx : données actuelles

Nasopharyngeal carcinoma (NPC) represents an interesting model in the field of head and neck cancers. This cancer is rare in occidental countries (<1/100,000) and relatively moderate to highly frequent in the Mediterranean area and south-east Asia. This disease is linked to Epstein-Barr virus with a latent infection starting in the oropharyngeal epithelium and involving not only both epithelial tumor cells but also B lymphocytes. This viral infection represents the early phase of carcinogenesis where Latent Membrane Protein-1 has an important role via the terminal part of the BARF-1 gene. There are also various chromosomal alterations reported in NPC concerning the regions of chromosomes 3p, 9p, 11q, 13q, 14q et 16q detected essentially in areas of suppressors genes. Allelic and antigenic specificities of class II and II HLA seems to be associated to an increased risk of NPC different according to the incidence areas. Anti-EBV serology is suggestive of for NPC with an elevated level of IgA EA (early antigen) and VCA (viral capsid antigen). Cyfra 21 represents a promising serum marker for NPC with a 80% sensitivity. Radiotherapy remains the base of loco-regional treatment with a more frequent and systematic use of systemic chemotherapy (primary or concomitant) for high-risk-patients (T3-4 and N2-3 disease).

NGX6 gene inhibits cell proliferation and plays a negative role in EGFR pathway in nasopharyngeal carcinoma cells

Nasopharyngeal carcinoma (NPC) is a common cancer in South China but is rare in other parts of the world. A novel NPC-related gene was isolated by location candidate cloning strategy, whose expression was down-regulated in NPC. This gene was designated human NGX6 (Genbank accession AF188239) and encoded a predicted protein of 338 amino acids that harbors an EGF-like domain. The effects of NGX6 on cells from human NPC cell line HNE1 were investigated. The cells transfected with NGX6 had a markedly high expression of NGX6, leading to significant decrease in cell proliferation and the capability to form colonies in soft agar, delaying the G0-G1 cell cycle progression. Flow cytometry assay indicated that the expression of cyclin D1 significantly decreased in NGX6-transfected HNE1 cells as well as cyclin A and E. There was a delay in tumor formation and a dramatic reduction in tumor size when cells transfected with NGX6 were injected into nude mice. In another way, we found NGX6 played a negative role in EGFR Ras/Mek/MAPK pathway. We propose that NGX6, as an EGF-like domain gene, could delay cell cycle G0-G1 progression and thus inhibit cell proliferation by negatively regulating EGFR pathway in NPC cells and down-regulating the expression of cyclin D1 and E.

Pathogenesis and treatment of nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC), an endemic tumor in southern China, has three unique etiologic factors, including genetic susceptibility, chemical carcinogens, and association with Epstein-Barr virus (EBV) infection. Recent identification of critical genetic changes in this cancer has allowed the description of a multistep model for the pathogenesis of NPC. NPC is highly radiosensitive and chemosensitive. Attempts have been made to improve treatment results by integrating radiotherapy with some form of chemotherapy. Here, we review the current evidence available on the various chemotherapy-radiotherapy sequencing approaches and seek to define the optimal integration of radiotherapy and chemotherapy. Despite consistently high response rates to platinum-based neoadjuvant chemotherapy, none of six randomized studies of neoadjuvant and/or adjuvant chemotherapy showed any improvement in overall survival, although two did demonstrate significant improvement in local control rates and progression-free survival. However, three randomized studies of concurrent cisplatin-radiotherapy one with, and two without, adjuvant chemotherapy demonstrated significant improvement in progression-free survival and two of these have demonstrated improvement in overall survival. Preliminary data on the use of neoadjuvant chemotherapy followed by concurrent chemoradiation have been highly encouraging. Concurrent cisplatin-radiation with or without adjuvant chemotherapy should be considered as standard practice for locoregionally advanced NPC. The addition of neoadjuvant chemotherapy warrants further investigation and appears to be the most likely approach to further improve treatment results.

Genetic and epigenetic changes in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a malignancy with remarkable racial and geographic distribution. The development of this EBV-associated cancer likely involves cumulative genetic and epigenetic changes in a background of predisposed genetic and environmental factors. Genome-wide studies have unravelled multiple chromosomal abnormalities with involvement of specific oncogenes and tumour suppressor genes. Alterations of genes such as Ras association domain family 1A (RASSF1A), p16/INK4A, p14/ARF suggest that multiple cellular pathways were dysregulated in the NPC cells. Studies on the precancerous lesions revealed early genetic changes and a critical role of EBV latent infection in the development of this cancer. Based on the existing findings, a pathogenetic model for NPC is proposed.