| Summary: | 碩士 === 國防醫學院 === 生物化學研究所 === 87 === The HER-2/neu protooncogene was known to overexpressed in approximately 30% of breast cancer patients and correlated with poor survival. Repression of HER-2/neu overexpression suppressed the malignant phenotype of HER-2/neu-overexpressing cancers. In our previous study, we found that the N-terminal 86-amino-acid only of the Epstein-Barr virus nuclear antigen-1(EBNA1-NT) could act as a transforming suppressor of the HER-2/neu oncogene. However, the EBNA1-NT peptide is rather small and difficult to be analyzed by Western blot. Therefore, we established in this study a EBNA1-NT-T7Tag construct by adding a T7Tag, which is easily detected by a commercial available anti-T7Tag antibody, to the N-terminal end of the EBNA1-NT. This EBNA1-NT-T7Tag clone was found to reserve the same repressing effect as that of EBNA1-NT on the HER-2/neu promoter in the transfection experiment using NIH3T3 as recepient cells. Furthermore, the endogenous modulation of the HER-2/neu by EBNA1-NT-T7Tag was investigated by stable transfecting EBNA1-NT-T7Tag into the HER-2/neu-overexpressing human breast cancer MDA-MB453 cells and the low HER-2/neu-expressing human breast cancer MDA-MB231 cells. Although the level of p185 HER-2/neu was not dramatically reduced in MDA-MB453 cells with EBNA1-NT-T7Tag, the phosphorylated from of p185 HER-2/neuwas apparently decreased. In addition, the morphology of MDA-MB453 cells were reversed by the EBNA1-NT-T7Tag. The data shown that the EBNA1-NT-T7Tag could downregulate HER-2/neu oncogne. Taken together, these results may provide a therapeutic benefit for HER-2/neu-overexpressing human cancers.
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