Stable expression of EBERs in immortalized nasopharyngeal epithelial cells confers resistance to apoptotic stress
Stable expression of EBERs in immortalized nasopharyngeal epithelial cells confers resistance to apoptotic stress
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DOI：
10.1002/mc.20133
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发表时间：
2005-10
影响因子：
4.6
通讯作者：
H. Wong;Xianghong Wang;R. C. Chang;D. Jin;H. Feng;Qi Wang;K. Lo;D. Huang;P. Yuen;K. Takada;Y. Wong;S. Tsao
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文献类型：
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作者：
H. Wong;Xianghong Wang;R. C. Chang;D. Jin;H. Feng;Qi Wang;K. Lo;D. Huang;P. Yuen;K. Takada;Y. Wong;S. Tsao
EB病毒（Epstein-Barr virus，EBV）感染与鼻咽癌（nasopharyngeal carcinoma，NPC）的发生发展密切相关。EBV编码的RNA（EBER）是EBV感染细胞中最丰富的EBV转录物（每个细胞约107个拷贝）。然而，EBER表达的细胞功能，特别是在鼻咽上皮细胞中，仍然知之甚少。EBER获得类似于双链RNA（dsRNA）的二级结构，并可能与双链RNA依赖性蛋白激酶（PKR）结合并干扰其功能。PKR的激活涉及导致蛋白质合成抑制和细胞凋亡的自磷酸化。PKR的激活诱导细胞凋亡可能是病毒感染细胞采取的抗病毒反应。我们已经研究了EBER表达在永生化鼻咽上皮细胞系（NP 69）的功能特性。通过用EBER表达质粒pESK 10转染NP 69细胞实现EBER的表达。与用对照质粒（pcDNA 3）转染的细胞相比，表达EBER的NP 69细胞获得更高的生长速率。然而，表达EBER的NP 69细胞在软琼脂中未形成集落，并且在裸鼠中无致瘤性。为了研究EBER是否可以保护鼻咽上皮细胞免受凋亡损伤，我们用dsRNA类似物poly（I）.poly（C）（pIC）处理表达EBER的NP 69细胞，以激活细胞中的PKR并检查其反应。在表达EBER的NP 69细胞中观察到PKR磷酸化水平较低和Bcl-2升高。此外，在用pIC处理后，发现表达EBER的NP 69细胞中的其他凋亡标志物，包括切割形式的半胱天冬酶-3和聚（ADP）核糖聚合酶（PARP）较低。在表达EBER的NP细胞中也观察到p38 MAPK（丝裂原活化蛋白激酶）和c-jun的磷酸化水平较低。我们的研究结果表明，EBER表达可能赋予永生化鼻咽上皮细胞抗凋亡表型。© 2005 Wiley利斯公司
Epstein–Barr virus (EBV) infection is closely associated with the development of nasopharyngeal carcinoma (NPC). The EBV‐encoded RNAs (EBERs) are the most abundant EBV transcripts (about 107 copies per cell) in EBV infected cells. However, the cellular function of EBER expression, particularly in nasopharyngeal epithelial cells, remains poorly understood. EBERs acquire secondary structures analogous to double‐stranded RNA (dsRNA) and may bind to the double‐stranded RNA‐dependent protein kinase (PKR) and interfere with its function. Activation of PKR involves autophosphorylation resulting in protein synthesis inhibition and cellular apoptosis. Induction of cellular apoptosis by activation of PKR may be an antiviral response adopted by virally infected cells. We have examined the functional properties of EBER expression in an immortalized nasopharyngeal epithelial cell line (NP69). Expression of EBERs was achieved by transfecting the NP69 cells with an EBER‐expressing plasmid, pESK10. The EBER‐expressing NP69 cells attained a higher growth rate compared to cells transfected with control plasmid (pcDNA3). However, the EBER‐expressing NP69 cells did not form colonies in soft agar and were non‐tumorigenic in nude mice. To investigate if EBERs may protect the nasopharyngeal epithelial cells from apoptotic insults, we treated the EBER‐expressing NP69 cells with a dsRNA analogue, poly(I).poly(C) (pIC), to activate PKR in cells and examined for their responses. Lower level of PKR phosphorylation and elevation of Bcl‐2 were observed in EBER‐expressing NP69 cells. In addition, other apoptotic markers including the cleaved forms of caspase‐3 and poly(ADP)ribose polymerase (PARP) were found to be lower in EBER‐expressing NP69 cells after treatment with pIC. Lower phosphorylation levels of p38 MAPK (mitogen‐activated protein kinase) and c‐jun were also observed in EBER‐expressing NP cells. Our results suggest that EBER expression may confer an apoptotic‐resistant phenotype in immortalized nasopharyngeal epithelial cells. © 2005 Wiley‐Liss, Inc.