-
Sufang Liu,
Hongde Li,
Lin Chen,
Lifang Yang,
Lili Li,
Yongguang Tao, Wei Li,
Zijian Li,
Haidan Liu,
Min Tang,
Ann M Bode,
Zigang Dong,
Ya Cao
[show abstract]
[hide abstract]
ABSTRACT: Epstein-Barr virus (EBV) reactivation into the lytic cycle plays certain roles in the development of EBV-associated diseases, including nasopharyngeal carcinoma and lymphoma. In the present study, we investigated the effects of the tea polyphenol (-)-epigallocatechin-3-gallate on EBV spontaneous lytic infection and the mechanism(s) involved in EBV-positive cells. We found that EGCG could effectively inhibit the constitutive lytic infection of EBV at the DNA, gene transcription, and protein levels by decreasing the phosphorylation and activation of ERK1/2 and Akt. By using cellular signaling pathway-specific inhibitors, we also explored the signaling mechanisms underlying the inhibitory effects of EGCG on EBV spontaneous lytic infection in cell models. Results show that specific inhibitors of MEK (PD98059) and PI3-K (LY294002) markedly down regulated gene transcription and expression of BZLF1 and BMRF1 indicating that the MEK/ERK1/2 and PI3-K/Akt pathways are involved in the EBV spontaneous lytic cycle cascade. Therefore, one of the mechanisms by which EGCG inhibits EBV spontaneous lytic infection appears to involve the suppression of the activation of MEK/ERK1/2 and PI3-K/Akt signaling.
Carcinogenesis 11/2012; · 5.70 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Disruption of the gatekeeper p53 tumor suppressor is involved in various virus-associated tumorigeneses, with aberrant ubiquitination as the major cause of p53 abnormalities in virus-associated tumors. Of note, wild-type p53 is accumulated in Epstein-Barr virus (EBV)-associated tumors, especially in nasopharyngeal carcinoma (NPC). We have previously identified that p53 is accumulated and phosphorylated by EBV oncoprotein latent membrane protein 1 (LMP1) in NPC. Here, we further found that LMP1 promoted p53 accumulation via two distinct ubiquitin modifications. LMP1 promoted p53 stability and accumulation by suppressing K48-linked ubiquitination of p53 mediated by E3 ligase MDM2, which is associated with its phosphorylation at Ser20, while increasing the levels of total cellular ubiquitinated p53. LMP1 also induced K63-linked ubiquitination of p53 by interacting with tumor necrosis factor receptor-associated factor 2 (TRAF2), thus contributing to p53 accumulation. Furthermore, LMP1 rescued tumor cell apoptosis and cell cycle arrest mediated by K63-linked ubiquitination of p53. Collectively, these results demonstrate aberrant ubiquitin modifications of p53 and its biological functions by viral protein LMP1, which has broad implications to the pathogenesis of multiple EBV-associated tumors.
Cell cycle (Georgetown, Tex.) 06/2012; 11(12):2327-36. · 5.36 Impact Factor
-
Bing du xue bao = Chinese journal of virology / [bian ji, Bing du xue bao bian ji wei yuan hui] 11/2011; 27(6):619-23.
-
Xiang-jian Luo, Wei Li,
Li-fang Yang,
Xin-fang Yu,
Lan-bo Xiao,
Min Tang,
Xin Dong,
Qi-pan Deng,
Ann M Bode,
Ji-kai Liu,
Ya Cao
[show abstract]
[hide abstract]
ABSTRACT: Grifolin, a secondary metabolite isolated from the fresh fruiting bodies of the mushroom Albatrellus confluens, has been shown to induce G1 phase cell-cycle arrest in tumor cells in previous studies of our group. However, the mechanisms of action are not completely understood. Our group further demonstrated that grifolin upregulates death-associated protein kinase 1 (DAPK1) in nasopharyngeal carcinoma cells (NPCs). Here, we found that grifolin induced dephosphorylation of DAPK1 (Ser308) to activate DAPK1 and subsequent phosphorylation of its potential downstream effector p21 (Thr145) in nasopharyngeal carcinoma cell CNE1. Inhibition of DAPK1 by introducing siRNA targeting DAPK1 reversed the grifolin- induced phosphorylation of p21. Furthermore, we confirmed that grifolin increased the half-life of p21 and promoted its stability. Flow cytometry analysis demonstrated that DAPK1 was involved in grifolin-induced G1 phase arrest in CNE1 cells. The similar effects induced by grifolin and mechanism beneath were identified in another nasopharyngeal carcinoma cell HONE1. In addition, we observed that grifolin promoted the protein-protein interaction of DAPK1 and ERK1/2 to prevent ERK1/2 nucleolus translocation. Our findings indicate that DAPK1 plays a crucial role in the induction of cell-cycle arrest at G1 phase by grifolin. Grifolin might represent a promising candidate in the prevention and intervention of cancer by targeting DAPK1 signaling to induce cell cycle G1 phase arrest.
European journal of pharmacology 09/2011; 670(2-3):427-34. · 2.59 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Epstein-Barr virus (EBV) infection in tumor cells is generally restricted to the latent forms of viral infection. Switching the latent form of viral infection into the lytic form may induce tumor cell death. High levels of nuclear factor (NF)-kappaB can inhibit EBV lytic replication, and aspirin has the ability to inhibit NF-kappaB activity. The aims of the current study were to determine the effects of aspirin on inducing EBV lytic infection, and thus to reveal the possibility of targeting EBV-positive cancer cells by aspirin. Our results showed that aspirin depleted NF-kappaB (p65) in the nucleus and reactivated EBV into lytic replication. Cells exhibited decreased viability in a dose- and time-dependent manner when incubated with aspirin. When ganciclovir was used in combination with aspirin to treat EBV-positive B95.8 cells and Raji cells, the cytotoxic effect of aspirin was amplified. We demonstrated that aspirin reduced the viability of EBV-positive B lymphocytes due to its ability to induce EBV lytic replication.
European Journal of Pharmacology 05/2008; 589(1-3):8-13. · 2.52 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Epstein-Barr virus (EBV) infection in tumor cells is generally restricted to the latent forms of viral infection. Switching the latent form of viral infection into the lytic form may induce tumor cell death. An important nuclear factor, nuclear factor (NF)-kappaB, is thought to play an essential role in EBV lytic infection; high levels of NF-kappaB can inhibit EBV lytic replication. In this study, we tested the effect of inducing EBV lytic replication using two NF-kappaB inhibitors: Bay11-7082 and Z-LLF-CHO, to reveal the possibility of targeting EBV-positive cancer therapy with these two NF-kappaB inhibitors. Our results showed that Bay11-7082 and Z-LLF-CHO reactivated EBV in a dose-dependent manner, thus resulting in EBV-positive 5-8F cell death. In contrast, there was no significant effect on EBV-negative HNE3 cells. When ganciclovir was used in combination with either Bay11-7082 or Z-LLF-CHO to treat 5-8F cells, the cytotoxic effect of the NF-kappaB inhibitor was amplified. The finding indicates that inhibiting the NF-kappaB activity of EBV-positive cells can induce lytic replication of EBV and cause lytic cytotoxicity against these cells.
Cell Biology International 05/2008; 32(8):1006-13. · 1.48 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Grifolin, a natural product isolated from the mushroom Albatrellus confluens, has been shown to inhibit the growth of some cancer cell lines and induce significant apoptosis. However, the molecular targets and the signaling mechanism underlying the anticancer effect of this compound are not completely understood. Here, we undertook a gene expression profiling study to identify novel targets of grifolin. We found that the effect of grifolin on the human nasopharyngeal carcinoma cell line CNE1 occurs primarily via the ERK1/2 pathway. At high doses, both the ERK1/2 and the ERK5 pathways may be involved in the inhibition. Because inhibition of the ERK1/2 or the ERK5 pathway has been associated with cell-cycle arrest and growth inhibition, we evaluated the cell cycle distribution after grifolin treatment. We found that grifolin significantly caused cell-cycle arrest in G1 phase. To investigate the underlying mechanisms, G1-related proteins were assayed by Western blotting. Following grifolin treatment, a concomitant inhibition of cyclin D1, cyclin E, CDK4 expression, and subsequent reduction in pRB phosphorylation occurred. Meanwhile, grifolin treatment also resulted in a significant upregulation of CKI (p19INK4D). These results suggest that the inhibition of the ERK1/2 or the ERK5 pathway is responsible for at least part of the induction of cell-cycle arrest in G1 phase by grifolin. These results are significant in that they provide a mechanistic framework for further exploring the use of grifolin as a novel antitumor agent.
Cancer Letters 01/2008; 258(2):199-207. · 4.24 Impact Factor
-
Lili Li,
Zijian Li,
Shanghui Zhou,
Lanbo Xiao,
Lili Guo,
Yongguang Tao,
Min Tang,
Ying Shi, Wei Li,
Wei Yi,
Ya Cao
[show abstract]
[hide abstract]
ABSTRACT: Epstein-Barr virus encoded latent membrane protein 1 (LMP1), an oncogenic protein, plays an important role in the carcinogenesis of nasopharyngeal carcinoma. The MDM2 gene is a cellular pro-oncogene that is abnormally up-regulated in human tumors. MDM2 is overexpressed in nasopharyngeal carcinoma, which is associated with the presence of EBV and cervical lymph node metastasis. Because MDM2 is capable of self-ubiquitination, and the ubiquitin proteasome pathway-dependent degradation is an important mechanism for regulating MDM2 levels in cells. Here we show that LMP1 augment MDM2 protein expression in dose-dependent level, and also lead to a drastic accumulation of ubiquitinated MDM2 species, this effect is associated with the stability of MDM2 modulated by LMP1. This is the first time to explain LMP1-regulated MDM2 through a post-ubiquitination mechanism.
Virus Research 01/2008; 130(1-2):275-80. · 2.94 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Elevated telomerase activity is observed in about 90% of human cancers. This activity correlates strictly with human telomerase reverse transcriptase (hTERT). Previously, it was shown that the Epstein-Barr virus-encoded latent membrane protein 1 (LMP1) induced telomerase activity in nasopharyngeal carcinoma cells. In this study, it was indicated that LMP1 inhibited p16(INK4A) expression, promoted phosphorylation of p105 Rb and upregulated E2F1 expression as well as transactivation, and overexpression of E2F1 alone was sufficient to upregulate telomerase activity. The JNK kinase cascade could also promote telomerase activity modulated by LMP1, that inhibition of JNK by JIP and TAM 67 dominant negative mutant abrogated telomerase activity. The data show that p16(INK4A)/Rb/E2F1 and JNK signaling pathways are involved in the regulation of telomerase activity via LMP1. The present study provides new perspectives on carcinogenesis of nasopharyngeal carcinoma that may be exploited for novel therapeutic strategies.
Journal of Medical Virology 09/2007; 79(8):1153-63. · 2.82 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: This paper presents a novel 3D porous micromixer fabricated using a selective ultrasonic foaming technique. The 3D porous structure can split, stretch, fold and break the mixing flows effectively and thus dramatically improves the mixing efficiency of microfluidic flows. In the paper, we report on the fabrication and performance of the 3D porous micromixer. The effects of flow rate, mixing length and pore size were studied using flow visualization experiments. It is shown that the proposed micromixer performs very well for flows with a wide range of Reynolds numbers. Sufficient mixing results can be achieved with a short mixing length for flows with Reynolds numbers as low as 0.1.
Journal of Micromechanics and Microengineering 08/2007; 17(9):1835. · 2.11 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Grifolin is a natural biologically active substance isolated from the fresh fruiting bodies of the mushroom Albatrellus confluens. Here, for the first time, we describe a novel activity of grifolin, namely its ability to inhibit the growth of tumor cells by the induction of apoptosis. Grifolin strongly inhibited the growth of tumor cell lines: CNE1, HeLa, MCF7, SW480, K562, Raji and B95-8. Analysis of acridine orange (AO)/ethidium bromide (EB) staining and flow cytometry showed that grifolin possessed apoptosis induction activity to CNE1, HeLa, MCF7 and SW480. Furthermore, the cytochrome c release from mitochondria was detected by confocal microscopy in CNE1 cells after a 12h treatment with grifolin. The increase of caspase-8, 9, 3 activities revealed that caspase was a key mediator of the apoptotic pathway induced by grifolin, and the underexpression of Bcl-2 and up-regulation of Bax resulted in the increase of Bax: Bcl-2 ratio, suggesting that Bcl-2 family involved in the control of apoptosis. Owing to the combination of the significant antitumor activity by inducing apoptosis and natural abundance of the compound, grifolin holds the promise of being an interesting antitumor agent that deserves further laboratory and in vivo exploration.
FEBS Letters 07/2005; 579(16):3437-43. · 3.54 Impact Factor
-
Yongguang Tao,
Xing Song,
Xiyun Deng,
Daxin Xie,
Leo M Lee,
Yiping Liu, Wei Li,
Lili Li,
Lin Deng,
Qiao Wu,
Jianping Gong,
Ya Cao
[show abstract]
[hide abstract]
ABSTRACT: Epstein-Barr virus (EBV)-encoded latent membrane protein 1 (LMP1) is considered to be the major oncogenic protein of EBV-encoded proteins and has always been the core of the oncogenic mechanism of EBV. Advanced studies on nuclear translocation of the epidermal growth factor receptor (EGFR) family have greatly improved our knowledge of the biological function of cell surface receptors. In this study, we used the Tet-on LMP1 HNE2 cell line as a cell model, which is a dual-stable LMP1-integrated nasopharyngeal carcinoma (NPC) cell line and the expression of LMP1 which could be regulated by the Tet system. We found that LMP1 could regulate the nuclear accumulation of EGFR in a dose-dependent manner quantitatively and qualitatively. We also demonstrated that the nuclear localization sequence of EGFR played some roles in the location of the protein within the nucleus under LMP1 regulation and EGFR in the nucleus could bind to the promoters of cyclinD1 and cyclinE, respectively. We further demonstrated that EGFR is involved in the acceleration of the G1/S phase transition by LMP1 through binding to cyclinD1 and cyclinE directly. These findings provided a novel view that the acceleration of LMP1 on the G1/S transition via the nuclear accumulation of EGFR was critical in the process of nasopharyngeal carcinoma.
Experimental Cell Research 03/2005; 303(2):240-51. · 3.58 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: To elucidate the expression of tanscription factor Ets-1 mediated by EB virus encoded latent membrane protein 1 (LMP1) in nasopharyngeal carcinoma (NPC) cells.
LMP1-expressing NPC HNE2 cells regulated by Tet-on system (pTet-on-LMP1 HNE2) were used. Expression of LMP1 and Ets-1 was observed after induction with Doxycycline (Dox). Expression of Ets-1 mRNA and protein was detected by RT-PCR and Western blot, respectively. The phosphorylation level of Ets-1 protein was examined by co-immunoprecipitation. The DNA binding activity of Ets-1 was detected by electrophoretic-mobility shift assay (EMSA).
After induction with Dox in pTet-on-LMP1 HNE2 cells, to some extent, the expression of Ets-1 mRNA and protein, its phosphorylation level and DNA binding activity were increased with enhancement of LMP1 expression.
LMP1 induces transcriptional activation and expression of Ets-1 which may contribute to the development of NPC.
Zhonghua zhong liu za zhi [Chinese journal of oncology] 09/2004; 26(8):454-7.
-
[show abstract]
[hide abstract]
ABSTRACT: The Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1) oncoprotein may cause multiple cellular changes, including the induction of epidermal growth factor receptor (EGFR) expression and the activation of the nuclear factor kappa B (NFkappaB) transcription factor. LMP1 increases the levels of both EGFR protein and mRNA but does not stabilize EGFR mRNA. Thus the effects of LMP1 are likely to be mediated by direct activation of the EGFR promoter. In this study, induction of LMP1 increased the EGFR in both protein and promoter levels in a dose dependent manner using tetracycline-regulated LMP1 expression in nasopharyngeal carcinoma (NPC) cell line. Mutational analysis of the LMP1 protein indicated that the C-terminal activation region-1 (CTAR1) domain was mainly involved in the EGFR promoter induction, while CTAR2 was necessary but not sufficient to induce EGFR promoter. Inhibition of LMP1 mediated NFkappaB activation by constitutive repressive inhibitory kappa B alpha (IkappaBalpha) marginally decreased EGFR promoter activity using transiently transfected IkappaBalpha dominant negative mutant. Promoter mutagenesis analysis demonstrated that two putative NFkappaB binding sites of EGFR promoter were very necessary for the transcriptional activity of EGFR induced by LMP1, the proximal NFkappaB binding site was more important than the distal NFkappaB binding site. Taken together, Epstein-Barr virus latent membrane protein 1 modulated the EGFR promoter activity in a NFkappaB dependent manner.
Virus Research 09/2004; 104(1):61-70. · 2.94 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1) oncoprotein may cause multiple cellular changes including the induction of epidermal growth factor receptor (EGFR) expression and activation of the NFkappaB transcription factor. LMP1 increases the levels of both EGFR protein and mRNA, but does not stabilize EGFR mRNA. Thus, the effects of LMP1 are likely to be mediated by the direct activation of the EGFR promoter. In this study, induction of LMP1 increased the EGFR in both protein and promoter levels in a dose-dependent manner using tetracycline-regulated LMP1 expression in nasopharyngeal carcinoma (NPC) cell line. Mutational analysis of the LMP1 protein indicated that the C-terminal activation region-1 (CTAR1) domain was mainly involved in the EGFR promoter induction, while CTAR2 was necessary but not sufficient to induce EGFR promoter. Inhibition of LMP1-mediated NFkappaB activation by constitutive repressive IkappaBalpha marginally decreased EGFR promoter activity using transiently transfected IkappaBalpha dominant negative mutant. Promoter mutagenesis analysis demonstrated that two putative NFkappaB binding sites of EGFR promoter were very necessary for the transcriptional activity of EGFR induced by LMP1, the proximal NFkappaB binding site was more important than the distal NFkappaB binding site, and both NFkappaB binding sites played a cooperative role. Taken together, Epstein-Barr virus latent membrane protein 1 modulated the EGFR promoter activity in a NFkappaB-dependent manner.
Cellular Signalling 08/2004; 16(7):781-90. · 4.06 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Epstein-Barr virus (EBV) encoded latent membrane protein 1 (LMP1) is considered to be the major oncogenic protein of EBV encoded proteins, and also it has always been the core of the oncogenic mechanism of EBV. Traditional receptor theory demonstrates that cell surface receptors exert biological functions on the membrane, which neither enter into the nucleus nor directly affect the transcription of the target genes. But, advanced studies on nuclear translocation of the epidermal growth factor receptor (EGFR) family have greatly developed our knowledge of the biological function of cell surface receptors. In this study, we used Tet-on LMP1 HNE2 cell line as a cell model, which is a dual-stable LMP1 integrated NPC cell line and the expression of LMP1 in which could be regulated by Tet system. We found that LMP1 could regulate the nuclear translocation of EGFR in a dose-dependent manner from both quantitative and qualitative levels through the Western blot analysis and the immunofluorescent analysis with a laser scanning confocal microscope. We further demonstrated that the nuclear localization sequence of EGFR played some roles in the location of the protein within the nucleus under LMP1 regulation, and the nuclear accumulation of EGFR regulated by LMP1 was in a ligand-independent manner. These findings provide a novel view that the regulation of LMP1 on the nuclear translocation of EGFR is critical for the process of nasopharyngeal carcinoma.
Science in China Series C Life Sciences 07/2004; 47(3):258-67. · 1.61 Impact Factor
