Dataset Information

Epstein-Barr virus-encoded latent membrane protein 1 impairs G2 checkpoint in human nasopharyngeal epithelial cells through defective Chk1 activation.

ABSTRACT: Nasopharyngeal carcinoma (NPC) is a common cancer in Southeast Asia, particularly in southern regions of China. EBV infection is closely associated with NPC and has long been postulated to play an etiological role in the development of NPC. However, the role of EBV in malignant transformation of nasopharyngeal epithelial cells remains enigmatic. The current hypothesis of NPC development is that premalignant nasopharyngeal epithelial cells harboring genetic alterations support EBV infection and expression of EBV genes induces further genomic instability to facilitate the development of NPC. The latent membrane protein 1 (LMP1) is a well-documented EBV-encoded oncogene. The involvement of LMP1 in human epithelial malignancies has been implicated, but the mechanisms of oncogenic actions of LMP1, particularly in nasopharyngeal cells, are unclear. Here we observed that LMP1 expression in nasopharyngeal epithelial cells impaired G2 checkpoint, leading to formation of unrepaired chromatid breaks in metaphases after ?-ray irradiation. We further found that defective Chk1 activation was involved in the induction of G2 checkpoint defect in LMP1-expressing nasopharyngeal epithelial cells. Impairment of G2 checkpoint could result in loss of the acentrically broken chromatids and propagation of broken centric chromatids in daughter cells exiting mitosis, which facilitates chromosome instability. Our findings suggest that LMP1 expression facilitates genomic instability in cells under genotoxic stress. Elucidation of the mechanisms involved in LMP1-induced genomic instability in nasopharyngeal epithelial cells will shed lights on the understanding of role of EBV infection in NPC development.

SUBMITTER: Deng W

PROVIDER: S-EPMC3382577 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Epstein-Barr virus-encoded latent membrane protein 1 impairs G2 checkpoint in human nasopharyngeal epithelial cells through defective Chk1 activation.

Deng Wen W Pang Pei Shin PS Tsang Chi Man CM Hau Pok Man PM Yip Yim Ling YL Cheung Annie L M AL Tsao Sai Wah SW

PloS one 20120625 6

Nasopharyngeal carcinoma (NPC) is a common cancer in Southeast Asia, particularly in southern regions of China. EBV infection is closely associated with NPC and has long been postulated to play an etiological role in the development of NPC. However, the role of EBV in malignant transformation of nasopharyngeal epithelial cells remains enigmatic. The current hypothesis of NPC development is that premalignant nasopharyngeal epithelial cells harboring genetic alterations support EBV infection and e ...[more]

PMID: 22761726

Similar Datasets

Project description:Comprehensive Profiling of Epstein-Barr Virus-Encoded miRNAome Associated with Specific Latent Type in Tumor Cells Epstein-Barr virus (EBV) is an etiological cause of many human lymphocytic and epithelial malignancies. EBV expressed different genes associated with three latent types. So far as many as 44 EBV-encoded miRNA species have been found but their comprehensive and comparative profiling is not well documented in three latent infection states linked to various tumor cells. In this study, we utilized the polyA-tailed quantitative real time RT-PCR procedure to measure the relative abundance of viral miRNA species that linked to individual viral genome locations in combination with microarray evaluation in a subset of representative lymphoid and epithelial tumor cells undergoing various types of EBV latent infection. The results showed that miR-BHRF1 family and miR-BART family are expressed differentially in a tissue-dependent and latency-dependent manner. In particular, in NPC tissue and the only EBV consistently harboring cell line C666-1 with latency type II, there were highly abundant miR-BART family but not miR-BHRF1 family members that accounted for more than 10% of the whole known human miRNA library, implicating their important roles in maintaining EBV latent infection and driving NPC tumorigenesis. In addition, EBV miRNAome-based clustering analysis could classify three distinct EBV latency types, meanwhile, for the first time, we found and subsequently evaluated a novel secret latent switch in BL cell line Daudi from type I to III, which was unable to be identified by traditional latent biomarkers. Together, our data provided an in-depth and comparative profiling of EBV miRNA transcriptome in correspondence with three EBV latent infections, suggesting that different viral miRNA species were involved in divergent host cell carcinogenesis. Finally, EBV miRNAome, as a cluster of novel latency biomarkers expressed variedly in tumor cells, greatly complements and improves the classical typing criteria in conjunction with other latently expressed marker genes. 2 NPC tissue samples and 2 NPC cell lines and 5 lymphocytic cell lines

Project description:BACKGROUND:EBV-encoded latent membrane protein 1 (EBV-LMP1) is an important oncogenic protein for nasopharyngeal carcinoma (NPC) and has been shown to engage a plethora of signaling pathways. Correspondingly, an LMP1-targeted DNAzyme was found to inhibit the growth of NPC cells both in vivo and in vitro by suppressing cell proliferation and inducing apoptosis. However, it remains unknown whether an LMP1-targeted DNAzyme would affect the vasculature of NPC. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) has been applied in the clinical trials of anti-angiogenic drugs for more than ten years, and Ktrans has been recommended as a primary endpoint. Therefore, the objective of the current study was to use DCE-MRI to longitudinally study the effect of an EBV-LMP1-targeted DNAzyme on the vasculature of patients with NPC. METHODS:Twenty-four patients were randomly divided into two groups: a combined treatment group (radiotherapy?+?LMP1-targeted DNAzyme) and a radiotherapy alone group (radiotherapy?+?normal saline). DCE-MRI scans were conducted 1?~?2 days before radiotherapy (Pre-RT), during radiotherapy (RT 50 Gy), upon completion of radiotherapy (RT 70 Gy), and three months after radiotherapy (3 months post-RT). Parameters of vascular permeability and intra- and extravascular volumes were subsequently obtained (e.g., Ktrans, kep, ve) using nordicICE software. RESULTS:Both Ktrans and kep values for NPC tumor tissues decreased for both groups after treatment. Moreover, a statistically significant difference in Ktrans values at the pre-therapy and post-therapy timepoints emerged earlier for the combined treatment group (RT 50 Gy, P =0.045) compared to the radiotherapy alone group (3 months post-RT, P = 0.032). For the kep values, the downward trend observed for both the combined treatment group and the radiotherapy alone group were similar. In contrast, ve values for all of the tumor tissues increased following therapy. CONCLUSIONS:The EBV-LMP1-targeted DNAzyme that was tested was found to accelerate the decline of Ktrans values for patients with NPC. Correspondingly, the LMP1-targeted DNAzyme treatments were found to affect the angiogenesis and microvascular permeability of NPC. TRIAL REGISTRATION:ClinicalTrials.gov: NCT01449942. Registered 6 October 2011.

Project description:Nasopharyngeal carcinoma (NPC) is consistently associated with Epstein-Barr virus (EBV) infection in regions in which it is endemic, including Southern China and Southeast Asia. The high mortality rates of NPC patients with advanced and recurrent disease highlight the urgent need for effective treatments. While recent genomic studies have revealed few druggable targets, the unique interaction between the EBV infection and host cells in NPC strongly implies that targeting EBV may be an efficient approach to cure this virus-associated cancer. Key features of EBV-associated NPC are the persistence of an episomal EBV genome and the requirement for multiple viral latent gene products to enable malignant transformation. Many translational studies have been conducted to exploit these unique features to develop pharmaceutical agents and therapeutic strategies that target EBV latent proteins and induce lytic reactivation in NPC. In particular, inhibitors of the EBV latent protein EBNA1 have been intensively explored, because of this protein's essential roles in maintaining EBV latency and viral genome replication in NPC cells. In addition, recent advances in chemical bioengineering are driving the development of therapeutic agents targeting the critical functional regions of EBNA1. Promising therapeutic effects of the resulting EBNA1-specific inhibitors have been shown in EBV-positive NPC tumors. The efficacy of multiple classes of EBV lytic inducers for NPC cytolytic therapy has also been long investigated. However, the lytic-induction efficiency of these compounds varies among different EBV-positive NPC models in a cell-context-dependent manner. In each tumor, NPC cells can evolve and acquire somatic changes to maintain EBV latency during cancer progression. Unfortunately, the poor understanding of the cellular mechanisms regulating EBV latency-to-lytic switching in NPC cells limits the clinical application of EBV cytolytic treatment. In this review, we discuss the potential approaches for improvement of the above-mentioned EBV-targeting strategies.

Dataset Information

Epstein-Barr virus-encoded latent membrane protein 1 impairs G2 checkpoint in human nasopharyngeal epithelial cells through defective Chk1 activation.

Publications

Epstein-Barr virus-encoded latent membrane protein 1 impairs G2 checkpoint in human nasopharyngeal epithelial cells through defective Chk1 activation.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets