Seo J S, Cho N Y, Kim H R, Tsurumi T, Jang Y S, Lee W K, Lee S K
Research Institute of Immunobiology, Catholic University, Seoul 137-701, Japan.
Oncol Rep. 2008 Jan;19(1):93-8.
Latent infection of the Epstein-Barr virus (EBV) is strongly associated with the pathogenesis of several human tumor types. The restricted expression of the latent EBV antigens is critical for EBV-associated tumors to escape from immune surveillance. EBV lytic replication can be triggered by various treatments and the induced lytic genes cause strong cytotoxic T lymphocyte (CTL) responses. Histone acetylation or deacetylation is associated with chromatin remodeling and regulates gene expression. Histone deacetylase (HDAC) inhibitors affect cell cycle progression as well as gene expression in a wide variety of transformed cells. We examined whether an HDAC inhibitor, TSA, can affect cell cycle progression and induce EBV lytic replication in EBV-transformed lymphoblastoid cell lines (LCLs). TSA caused cell cycle arrest at low concentrations and induced apoptosis at higher (>300 nM) concentrations in the LCLs and EBV negative BJAB cells. To clarify the underlying mechanism of TSA-induced cell cycle arrest, expression of cell cycle regulatory factors was examined by RNase protection assay and Western blot analysis. Following TSA treatment, a reduced expression of cyclin D2 and an induction of p21 may have played an essential role for G1 arrest in LCLs, while p21 induction might have arrested BJAB cells in G1 phase. A Cdk inhibitor, p57, was increased by 300 nM TSA in both LCLs and BJAB cells, indicating its role in apoptosis. Moreover, immunofluorescene assay and Western blotting showed that TSA induced EBV lytic replication in LCL cells. These results suggest that TSA may exert an enhanced anti-tumor effect for EBV-associated tumors not only by inducing a cell cycle arrest and apoptosis, but also by triggering an EBV lytic cycle.
爱泼斯坦-巴尔病毒（EBV）的潜伏感染与多种人类肿瘤类型的发病机制密切相关。EBV潜伏抗原的限制性表达对于EBV相关肿瘤逃避免疫监视至关重要。EBV的裂解复制可由多种处理触发，诱导的裂解基因会引发强烈的细胞毒性T淋巴细胞（CTL）反应。组蛋白乙酰化或去乙酰化与染色质重塑相关，并调节基因表达。组蛋白脱乙酰酶（HDAC）抑制剂会影响多种转化细胞的细胞周期进程以及基因表达。我们研究了HDAC抑制剂曲古抑菌素A（TSA）是否会影响EBV转化的淋巴母细胞系（LCL）中的细胞周期进程并诱导EBV的裂解复制。TSA在低浓度时导致LCL以及EBV阴性的BJAB细胞出现细胞周期停滞，在高浓度（>300 nM）时诱导细胞凋亡。为了阐明TSA诱导细胞周期停滞的潜在机制，通过核糖核酸酶保护试验和蛋白质免疫印迹分析检测了细胞周期调节因子的表达。TSA处理后，细胞周期蛋白D2表达降低以及p21的诱导可能在LCL的G1期停滞中起了关键作用，而p21的诱导可能使BJAB细胞停滞在G1期。在LCL和BJAB细胞中，300 nM的TSA均使细胞周期蛋白依赖性激酶（Cdk）抑制剂p57增加，表明其在细胞凋亡中的作用。此外，免疫荧光测定和蛋白质免疫印迹显示TSA在LCL细胞中诱导了EBV的裂解复制。这些结果表明，TSA可能不仅通过诱导细胞周期停滞和细胞凋亡，还通过触发EBV裂解周期，对EBV相关肿瘤发挥增强的抗肿瘤作用。
