EB 病毒存在於B-淋巴細胞可被許多外來的刺激誘發進入分裂期（lyti cycle, 即病毒活化），例如：12-O-tetradecanoylphorbol-13-acetate (TPA), butyric acid, calcium ionophore A23187, transforming growth factor-b, 及anti-immunoglobulin crosslinking 等。因為EB 病毒病毒活化的現象曾見於某些接受化學治療的臨床病例中，本研究希望以體外細胞培養的方式來測試「抗癌藥物可直接導致EB 病毒病毒活化」的假說。
Raji 細胞乃一含EB 病毒之B-淋巴瘤細胞株，TPA 可誘發EB 病毒病毒活化。EB 病毒病毒活化的現象以下述方式加以評估：（1）EB 病毒之BZLF1 基因mRNA之表現，以即時偵測定量PCR (real-time quantitative PCR) 測定；（2）BZLF1 基因
所製造之ZEBRA 蛋白，以流式細胞儀測定；（3）ZEBRA 蛋白之轉錄活性，以EB病毒-DR 促進區控制之冷螢光西每報告基因測定；（4）ZEBRA 蛋白之轉錄活性，以EB病毒內有之EA-D蛋白表現與否測定之（即：EB 病毒BMRF1 基因之產物）。
我們以doxorubicin 與cisplatin 兩個臨床上十分常用的化療藥物進行測試。這兩個藥物都可以誘發BZLF1 mRNA 及
ZEBRA 蛋白的表現，而且呈現一「隨劑量增加而遞增」之趨勢。更者，這兩個藥物也誘導DR 促進區控制之冷螢光西每報告基因、及EB 病毒內有的EA-D 的表現，顯示化療藥物除了增加ZEBRA 蛋白的量外，也使ZEBRA 蛋白的轉錄活性大為提升。
我們的結果指出：抗癌藥物除了細胞毒殺作用外，可以誘發EB 病毒BZLF1 mRNA/蛋白之表現、且增加其轉錄活性，亦即增加了EB 病毒的病毒活化。換言之，化學治療可能是臨床上病患接受化學治療時，發生EB 病毒病毒活化的一項可能的危險因子。Epstein-Barr virus (EBV) can be activated in B lymphoid cells to enter the lytic cycle by various kinds of stimuli, including
12-O-tetradecanoylphorbol-13-acetate (TPA), butyric acid, calcium ionophore A23187, transforming growth factor-b, and
anti-immunoglobulin crosslinking. EBV reactivation has been clinically observed in
patients receiving systemic chemotherapy.
This study sought in vitro evidence to suggest whether anticancer drugs may directly contribute to the EBV reactivation.
Raji cells, an EBV-containing Burkitt’s lymphoma cell line, were used as the experimental model. TPA served as a positive control for chemical induction of EBV reactivation. Expression of the
BZLF1 transcript of EBV and its encoded protein, ZEBRA, were examined by real-time quantitative reverse transcriptionpolymerase chain reaction (qRT-PCR) and flow cytometry, respectively.
Transactivation activity of ZEBRA was further assessed by a luciferase reporter assay of EBV DR-promoter activity and a flow cytometry assay assessing the endogenous expression of EA-D (BMRF1).
Doxorubicin and cisplatin, two commonly used anticancer agents, induced a dose-dependent upregulation of BZLF1 mRNA and ZEBRA protein. The
luciferase reporter activity and the expression of endogenous EA-D protein, also increased by doxorubicin and cisplatin, indicated an upregulation of the transactivating activity of ZEBRA.
These data indicate that cytotoxic anticancer drugs may upregulate the expression and the transactivating activity of BZLF1, and suggest that systemic chemotherapy may be a risk factor for EBV reactivation in patients with EBV-associated malignancies
