Epstein-Barr virus-encoded LMP1 promotes cisplatin-induced caspase activation through JNK and NF-kappaB signaling pathways

DUSP16 promotes cancer chemoresistance through regulation of mitochondria-mediated cell death

Drug resistance is a major obstacle to the treatment of most human tumors. In this study, we find that dual-specificity phosphatase 16 (DUSP16) regulates resistance to chemotherapy in nasopharyngeal carcinoma, colorectal cancer, gastric and breast cancer. Cancer cells expressing higher DUSP16 are intrinsically more resistant to chemotherapy-induced cell death than cells with lower DUSP16 expression. Overexpression of DUSP16 in cancer cells leads to increased resistance to cell death upon chemotherapy treatment. In contrast, knockdown of DUSP16 in cancer cells increases their sensitivity to treatment. Mechanistically, DUSP16 inhibits JNK and p38 activation, thereby reducing BAX accumulation in mitochondria to reduce apoptosis. Analysis of patient survival in head & neck cancer and breast cancer patient cohorts supports DUSP16 as a marker for sensitivity to chemotherapy and therapeutic outcome. This study therefore identifies DUSP16 as a prognostic marker for the efficacy of chemotherapy, and as a therapeutic target for overcoming chemoresistance in cancer.

Designing an effective vaccine to prevent Epstein-Barr virus-associated diseases: challenges and opportunities

INTRODUCTION

Epstein-Barr virus (EBV) is a ubiquitous herpesvirus associated with a number of clinical manifestations. Primary EBV infection in young adolescents often manifests as acute infectious mononucleosis and latent infection is associated with multiple lymphoid and epithelial cancers and autoimmune disorders, particularly multiple sclerosis. Areas covered: Over the last decade, our understanding of pathogenesis and immune regulation of EBV-associated diseases has provided an important platform for the development of novel vaccine formulations. In this review, we discuss developmental strategies for prophylactic and therapeutic EBV vaccines which have been assessed in preclinical and clinical settings. Expert commentary: Major roadblocks in EBV vaccine development include no precise understanding of the clinical correlates of protection, uncertainty about adjuvant selection and the unavailability of appropriate animal models. Recent development of new EBV vaccine formulations provides exciting opportunities for the formal clinical assessment of novel formulations.

Embelin prevents LMP1-induced TRAIL resistance via inhibition of XIAP in nasopharyngeal carcinoma cells

The tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) selectively induces apoptosis in the majority of tumor cells, whilst sparing normal cells. However, the potential use of TRAIL in the treatment of cancer is limited by the inevitable emergence of drug resistance. The present study reports the upregulation of latent membrane protein 1 (LMP1)-induced TRAIL resistance via the enhanced expression of X-linked inhibitor of apoptosis protein (XIAP) in nasopharyngeal carcinoma (NPC) cells. LMP1-positive NPC cells were indicated to be more sensitive to TRAIL compared with LMP1-negative NPC cells in three NPC cell lines. CNE-1 is a LMP1-negative NPC cell line that was transfected with pGL6-LMP1; following which, sensitivity to TRAIL decreased. LMP1-induced TRAIL resistance was associated with the decreased cleavage of caspase-8,-3 and -9, BH3 interacting domain death agonist (Bid) and mitochondrial depolarization, without any effects on the expression of the death receptors, B-cell lymphoma (Bcl)-2 and Bcl-extra long. Knockdown of XIAP with small interfering RNA increased caspase-3 and -9 and Bid cleavage, and prevented LMP1-induced TRAIL resistance. Furthermore, embelin, the inhibitor of XIAP, prevented LMP1-induced TRAIL resistance in the Epstein-Barr virus (EBV)-positive CNE-1-LMP1 and C666-1 NPC cell lines. However, embelin did not enhance TRAIL-induced apoptosis in NP-69, which was used as a benign nasopharyngeal epithelial cell line. These data show that LMP1 inhibits TRAIL-mediated apoptosis by upregulation of XIAP. Embelin may be used in an efficacious and safe manner to prevent LMP1-induced TRAIL resistance. The present study may have implications for the development and validation of novel strategies to prevent TRAIL resistance in EBV-positive NPC.

LMP1-induced cell death may contribute to the emergency of its oncogenic property

BACKGROUND AND OBJECTIVES

Epstein-Barr Virus (EBV) Latent Membrane Protein 1 (LMP1) is linked to a variety of malignancies including Hodgkin's disease, lymphomas, nasopharyngeal and gastric carcinoma. LMP1 exerts its transforming or oncogenic activity mainly through the recruitment of intracellular adapters via LMP1 C-terminal Transformation Effector Sites (TES) 1 and 2. However, LMP1 is also reported to elicit significant cytotoxic effects in some other cell types. This cytotoxic effect is quite intriguing for an oncogenic protein, and it is unclear whether both functional aspects of the protein are related or mutually exclusive.

METHODOLOGY AND PRINCIPAL FINDINGS

Using different ectopic expression systems in both Madin-Darby canine kidney (MDCK) epithelial cells and human embryonic kidney HEK-293 cells, we observe that LMP1 ectopic expression massively induces cell death. Furthermore, we show that LMP1-induced cytotoxicity mainly implies LMP1 C-terminal transformation effector sites and TRADD recruitment. However, stable expression of LMP1 in the same cells, is found to be associated with an increase of cell survival and an acquisition of epithelial mesenchymal transition phenotype as evidenced by morphological modifications, increased cell mobility, increased expression of MMP9 and decreased expression of E-cadherin. Our results demonstrate for the first time that the cytotoxic and oncogenic effects of LMP1 are not mutually exclusive but may operate sequentially. We suggest that in a total cell population, cells resistant to LMP1-induced cytotoxicity are those that could take advantage of LMP1 oncogenic activity by integrating LMP1 signaling into the pre-existent signaling network. Our findings thus reconcile the apparent opposite apoptotic and oncogenic effects described for LMP1 and might reflect what actually happens on LMP1-induced cell transformation after EBV infection in patients.

EBV-associated lymphomas in adults

Epstein-Barr virus (EBV) is a ubiquitous γ-herpes virus that infects most people but results in life-threatening diseases in only a small subset. Persons who are unable to maintain the virus in its latent state can develop uncontrolled EBV-driven lymphoproliferative disorders and lymphomas. EBV-associated lymphomas are well characterized in patients with known defects in cellular immunity as occurs post-transplantation or HIV/AIDS but are increasingly recognized in patients without overt immunodeficiencies. Improved understanding of the biology of these lymphomas and the role EBV plays in lymphomagenesis offer the opportunity for improved therapies targeted at important signaling pathways and immunotherapy specific against EBV viral antigens.

Latent membrane protein 1 of Epstein-Barr virus sensitizes cancer cells to cisplatin by enhancing NF-κB p50 homodimer formation and downregulating NAPA expression

Expression of the oncogenic latent membrane protein 1 (LMP1) of Epstein-Barr virus is involved in the pathogenesis of nasopharyngeal carcinoma (NPC) and lymphoma. In previous studies, we found that expression of LMP1 was sufficient to transform BALB/c-3T3 cells. In contrast, other studies have shown that LMP1 induces apoptosis in a NF-κB-dependent manner and also inhibits the growth of tumors in mice, thereby indicating that LMP1 may produce various biological effects depending on the biological and cellular context. Still, the mechanism underlying the pro-apoptotic activity of LMP1 remains unclear. In the present study, we found that LMP1 inhibits the expression of NAPA, an endoplasmic reticulum SNARE protein that possesses anti-apoptotic properties against the DNA-damaging drug cisplatin. Accordingly, LMP1-transformed BALB/c-3T3 cells were sensitized to cisplatin-induced apoptosis, whereas no sensitization effect was noted following treatment with the mitotic spindle-damaging drugs vincristine and taxol. Knockdown of LMP1 with antisense oligonucleotides restored NAPA protein level and rendered the cells resistant to cisplatin. Similarly, overexpression of NAPA reduced the effect of LMP1 and induced resistance to cisplatin. LMP1 was shown to upregulate the NF-κB subunit p50, leading to formation of p50 homodimers on the NAPA promoter. These findings suggest that the viral protein LMP1 may sensitize cancer cells to cisplatin chemotherapy by downregulating NAPA and by enhancing the formation of p50 homodimers which in turn inhibit the expression of NF-κB regulated anti-apoptotic genes. These findings provide an explanatory mechanism for the pro-apoptotic activity of LMP1 as well as new therapeutic targets to control tumor growth.

Upregulation of MiR-155 in nasopharyngeal carcinoma is partly driven by LMP1 and LMP2A and downregulates a negative prognostic marker JMJD1A

The role of microRNA-155 (miR-155) has been associated with oncogenesis of several human tumors. However the expression pattern of miR-155 has not been investigated in nasopharyngeal carcinoma (NPC). The present study was to assess miR-155 expression pattern and its possible function in NPC, to identify its targets and evaluate their clinical applications in NPC. MiR-155 was found to be upregulated in two Epstein-Barr virus (EBV) negative NPC derived cell lines CNE1 and TW03, as well as in NPC clinical samples by quantitative Real-time PCR and in situ hybridization detection. EBV encoded LMP1 and LMP2A could further enhance the expression of miR-155 in NPC CNE1 and TW03 cells. JMJD1A and BACH1 were identified as putative targets of miR-155 in a bioinformatics screen. Overexpression of miR-155 downregulated a luciferase transcript fused to the 3′UTR of JMJD1A and BACH1. MiR-155 mimic could downregulate the expression of JMJD1A and BACH1, while miR-155 inhibitor could upregulate JMJD1A expression in NPC cell lines. Moreover, downregulation of JMJD1A was significantly correlated with N stage in TNM classification (p = 0.023), a lower five-year survival rate (p = 0.021), and a lower five-year disease-free survival rate (p = 0.049) of NPC patients. Taken together, up-regulation of miR-155 in NPC is partly driven by LMP1 and LMP2A, and results in downregulation of JMJD1A, which is associated with N stage and poor prognosis of NPC patients. The potential of miR-155 and JMJD1A as therapeutic targets in NPC should be further investigated.

Tumor viruses and cancer biology: Modulating signaling pathways for therapeutic intervention

Tumor viruses have provided relatively simple genetic systems, which can be manipulated for understanding the molecular mechanisms of the cellular transformation process. A growing body of information in the tumor virology field provides several prospects for rationally targeted therapies. However, further research is needed to better understand the multiple mechanisms utilized by these viruses in cancer progression in order to develop therapeutic strategies. Initially viruses were believed to be associated with cancers as causative agents only in animals. It was almost half a century before the first human tumor virus, Epstein-Barr virus (EBV), was identified in 1964. Subsequently, several human tumor viruses have been identified including Kaposi sarcoma associated herpesvirus (KSHV), human Papillomaviruses (HPV), Hepatitis B virus (HBV), Hepatitis C virus (HCV), Human T lymphotropic virus (HTLV-1) and recently identified Merkel cell Polyomavirus (MCPyV). Tumor viruses are sub-categorized as either DNA viruses, which include EBV, KSHV, HPV, HBV, and MCPyV, or RNA viruses such as HCV and HTLV-1. Tumor-viruses induce oncogenesis through manipulating an array of different cellular pathways. These viruses initiate a series of cellular events, which lead to immortalization and proliferation of the infected cells by disrupting the mitotic checkpoint upon infection of the host cell. This is often accomplished by functional inhibition or proteasomal degradation of many tumor suppressor proteins by virally encoded gene products. The virally infected cells can either be eliminated via cell-mediated apoptosis or persist in a state of chronic infection. Importantly, the chronic persistence of infection by tumor viruses can lead to oncogenesis. This review discusses the major human tumor associated viruses and their ability to modulate numerous cell signaling pathways, which can be targeted for potential therapeutic approaches.

Interleukins, laminin and Epstein - Barr virus latent membrane protein 1 (EBV LMP1) promote metastatic phenotype in nasopharyngeal carcinoma

Background

Nasopharyngeal carcinoma (NPC) is a type of neoplasm that is highly prevalent in East Asia and Africa with Epstein-Barr virus (EBV), genetic, and dietary factors implicated as possible aetiologic factors. Previous studies suggested the association of certain cytokines with the invasion and metastatic properties of NPC. The present study examined the roles of EBV latent membrane protein-1 (LMP1), interleukin-6 (IL-6), interleukin-10 (IL-10), transforming growth factor-beta 1 (TGF-β1) and laminin in the regulation of matrix-metalloproteinases (MMPs) and vascular endothelial growth factor (VEGF) in NPC. The effects of these factors on bmi-1, an oncogene, and ngx6, a tumour suppressor gene, were also investigated.

Methods

TW01 cells expressing LMP1 (TW01-LMP1) were established via transfection with the B95.8 EBV LMP1 gene. Both TW01 and TW01-LMP1 cells were treated with 100 pg/ml IL-6, 1000 pg/ml IL-10 and 100 pg/ml TGF-β1, separately and also in combination at their respective concentration for 48 hours. Treated cells were subjected to laminin adherence assay. The cells were also cultured with and without laminin and assayed for MMP-3, MMP-9 and VEGF production using enzyme-linked immunosorbent assay (ELISA). The cellular apoptotic property was analysed using caspase-3 apoptosis assay. The expression of bmi-1 and ngx6 gene was investigated using real time reverse transcriptase polymerase chain reaction.

Results

LMP1 was found to reduce the adherence of NPC cells towards laminin (p < 0.05) as compared to control. Treatment with IL-6 at 100 pg/ml enhanced the production of MMP-9 in both TW01 and TW01-LMP1 cells (p < 0.05). When cultured on laminin, the levels of MMP-3 and VEGF were significantly increased (p < 0.05) in TW01-LMP1 cells. TW01-LMP1 cells had relatively greater resistance to apoptosis as compared to TW01 cells (p < 0.05). Laminin, IL-6 and LMP1 were found to up-regulate the expression of bmi-1 and suppressed the expression of ngx6.

Conclusions

We conclude that IL-6 reduced cell adherence towards laminin and increased MMP-9 production in NPC cells. Our data suggested that EBV LMP1 was able to confer resistance of apoptosis and increased MMP-9 production in NPC cells. When cultured on laminin, TW01 cells expressing the EBV LMP1 (TW0-LMP1) that were treated with IL-6 at 100 pg/ml displayed increased MMP-9 production, up-regulation of bmi-1 oncogene expression and down-regulation of ngx6 tumour suppressor gene expression. These findings implicate the roles of EBV LMP1, laminin and IL-6 in the promotion of invasion and metastasis in NPC.

Cellular responses to Cisplatin-induced DNA damage

Cisplatin is one of the most effective anticancer agents widely used in the treatment of solid tumors. It is generally considered as a cytotoxic drug which kills cancer cells by damaging DNA and inhibiting DNA synthesis. How cells respond to cisplatin-induced DNA damage plays a critical role in deciding cisplatin sensitivity. Cisplatin-induced DNA damage activates various signaling pathways to prevent or promote cell death. This paper summarizes our current understandings regarding the mechanisms by which cisplatin induces cell death and the bases of cisplatin resistance. We have discussed various steps, including the entry of cisplatin inside cells, DNA repair, drug detoxification, DNA damage response, and regulation of cisplatin-induced apoptosis by protein kinases. An understanding of how various signaling pathways regulate cisplatin-induced cell death should aid in the development of more effective therapeutic strategies for the treatment of cancer.

Epstein-Barr virus genetic variation in Vietnamese patients with nasopharyngeal carcinoma: full-length analysis of LMP1

Genetic variation in tumor virus genes and its impact on function might contribute to the understanding of geographic differences in risks for virus-associated tumors. This is particularly true for the genes known to contribute to the biology of the tumor. It is has been proposed that Epstein-Barr virus (EBV) gene variation has a role in the high risk of nasopharyngeal carcinoma (NPC) in South-East Asia. NPC is among the five most common cancers in Vietnam. EBV-NPC cells always express EBV nuclear antigen 1 (EBNA1) and also frequently latent membrane protein 1 and 2 (LMP1 & LMP2). To investigate EBV gene variation in Vietnamese NPC patients we analyzed the full length of LMP1 gene including its promoter region, and the N-termini of both EBNA1 and LMP2A genes from five NPC biopsies. We detected two EBV variants V1 and V2 based on the LMP1 nucleotide sequence pattern compared with the prototype B95-8 and some available sequences including Chinese variants. The V1 variant shows strong similarity to a variant dominant in Southern China (China 1), while the V2 variant is similar to a Thai variant SEA 2 and partly identity with GD1 in the C-terminus. The promoter region and transmembrane domain of the SEA 2-like samples contained some specific differences compared with previously published variants. In contrast, analysis of EBNA1 N- and LMP2A N-termini only revealed minor changes. Our findings reinforces that the polymorphisms of whole LMP1 sequence should be considered in future EBV molecular epidemiology studies in different geographic populations.