MEADA Akihiko Kochi University, Department of Pediatrics, Instructor (50335931)
IMAI Shosuke Kochi University, Department of Microbiology and Infection, Professor (60232592)
FUJIEDA Mikiya Kochi University, Department of Pediatrics, Associate Professor (60209020)
黒田 正幸 高知大学, 医学部, 助手 (00253005)
|Budget Amount *help
¥3,820,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥420,000)
Fiscal Year 2007: ¥1,820,000 (Direct Cost: ¥1,400,000、Indirect Cost: ¥420,000)
Fiscal Year 2006: ¥2,000,000 (Direct Cost: ¥2,000,000)
The aim of this study was to identify the cellular genes associated with or responsible for the oncogenesisi of Epstein-Barr virus (EBV) in EBV-positive T, MC and epithelial tumor cells, by utilizing dominant-negative EBNA1 (DNE1; Mal. Ther., 11(4): 578-90, 2005)that can eradicate EBV episomes from cells. We prepared isogenic pairs of EBV-positive and -negative NK- and T-cell lines by DNE1 transduction and compared their malignant grade. Concomitantly alterations of cellular gene expression in those cell pairs were comprehensively assessed with the multi-cytokine assay system, thereby elucidating the role(s)of EBV in malignant conversion. Further, we analysed EBV-specific cytotoxic T-cells (EBV-CTL) by a tetramer assay using 3 EBV-antigens, i.e., BRLF1, BMLF1 and EBNA3. The results obtained are as follows.
1. Adenovirus vector-mediated transduction of our DNE1 successfully eradicated EBV episomes from the majority of naturally EBV-positive T-cell and NK-cell lymphoma and epithelial tumo
r cell lines in a few days.
2. The DNE1-induced EBV-lost T-cells and NK-cells showed a striking suppression of their malignant phenotypes, such as prolongation of doubling time and loss of anchorage-independent growth potential, compared with parental EBV-positive T-cell and NK-cell tumors. In a part of the EBV-lost T-cells and NK-cells, loss of viral genome also brought about cell death.
3. The EBV-lost T-cells and NK-cells showed significantly decreased production of some cytokines, such as interleukin-9, compared with the parental EBV-positive T-cell and NK-cell tumors. Conversely, the production levels of another cytokine was also found to be upregulated in the EBV-lost T-cells.
These results indicate that the EBV-dependent malignant phenotypes in T- and NK-cells and perhaps also in epithelial cells, as in B-cell lymphomas, are associated, at least partly, with upregulation (i.e., the autocrine mechanism) and/or down regulation of certain cytokines. We are planning to explore precisely the mechanisms of cytokine gene control and specific effects on EBV oncogenesis. Less