Abstract 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.
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.
Human NESG1 (CCDC19) gene was originally isolated in our laboratory from human nasopharynx tissue. However, the biological and clinical significances of this gene remain largely unknown. In this report, two errors in the originally submitted sequence of human NESG1 gene were found, and the open reading frame sequence of NESG1 (Accession number: NM_012337.1) was revised and updated in the NCBI database (Accession number: NM_012337.2). The antibody raised against the revised sequence of NESG1 detected a single band of 66 kD in human nasopharynx tissues. NESG1 transcripts were specifically expressed in the nasopharynx epithelium. Expression of NESG1 transcripts and protein was downregulated or absent in nasopharyngeal carcinoma (NPC) tissues and cell lines in comparison to that in the normal nasopharynx tissues. The levels of NESG1 protein were significantly greater in the low-grade NPC tissues than that in the high-grade NPC tissues. Induced expression of NESG1 in otherwise NESG1-negative 5-8F cells not only significantly decreased cell proliferation, G1-S phase transition, but also markedly inhibited the ability of cell migration and invasion as well as in vivo tumorigenesis. Furthermore, NESG1 also significantly regulated the expression of cell cycle regulator CCNA1 and p21. Our findings first provided evidence that NESG1 may act as a tumor suppressor by inhibiting cell proliferation, invasion and migration of NPC cells.
Phosphatase and tensin homolog (PTEN) is a major tumor suppressor and usually silenced via the deletion, insertion and mutation. We previously discovered its inactivation via aberrant CpG island methylation. Here, we provide further evidence that EBV latent membrane protein 1(LMP1) can induce a higher intensity of DNA methylation at PTEN CpG islands, inactivating PTEN at the cellular and molecular level. Initially, increased methylation intensity of PTEN CpG islands was observed in EBV-infected nasopharyngeal carcinoma (NPC) cells, accompanied by decreased PTEN expression. In NPC tissue samples showing the methylation at PTEN promoter, LMP1 was highly expressed in higher methylation intensity group relative to lower intensity group, and DNA methyltransferase 3b (DNMT3b) expression was positively correlated with LMP1 expression. Moreover, transfection of LMP1 gene into EBV-negative NPC cells demonstrated that LMP1 up-regulated DNMT3b expression, leading to a higher intensity of PTEN CpG island methylation. Mechanistically, computational prediction and luciferase reporter assay identified a functional NF-κB binding site on DNMT3b promoter and the mutated NF-κB binding site abolished LMP1-mediated DNMT3b activation. Chromatin immunoprecipitation displayed that NF-κB p65 subunit constitutively bound to DNMT3b promoter, supporting the activation of DNMT3b by EBV LMP1 via NF-κB signaling. Furthermore, the expression level of DNMT3b was observed to be increased in the nuclei of LMP1-expressing NPC cells, and a NF-κB inhibitor, PDTC, counteracted LMP1-mediated DNMT3b overexpression. Thus, this study first reports that LMP1-mediated NF-κB can up-regulate DNMT3b transcription, thereby leading to relatively higher methylation intensity at PTEN CpG islands, and ultimately silencing major tumor suppressor PTEN.
It is well-known that the broad-bean weevil, Bruchus rufimanus Boheman, is a seriousinsect pest infesting the broad-beans in this country. This weevil can only complete onegeneration each year and overwinters in the adult stage. It has been shown by our ex-periments that adult weevils can be completely controlled by mixing the infested broad-beans with 5 p.p.m. of lindane dust, while such a kind of treatment has failed to kill bothlarvae and pupae in seed beans. Complete kill can be obtained when the infested broad-beans are fumigated with phostoxin at a dosage of three grams to 200 catties of beans.It is proposed that bean vines and other rufuse, and infested beans, left both in the fieldand on the sunning ground should be cleaned out, plowed under, converted into manure,or burned in order to destroy many wintering weevils out of doors. During both flower-ing and podding stages of the bean plants, dusting with 1% 666 powder in the field ata dosage of 2.5 catties per mow can give better control. Owing to the broad-bean weevilsprefering only to attack the broad-beans in the vicinity of Wuchang, therefore, broad-beanand pea rotation in this region may be very effective to control these pests, and probablypea weevil, Bruchus pisorum L. It has also been shown that the javel-green-coloredbroad-beans of larger size are more or less resistant to the weevil's attack than thosegreenish-yellow-colored varieties of smaller size.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)