【摘要】 背景与目的:人表皮生长因子(human epidermal growth factor,EGF)是受体起作用刺激细胞增殖和分化的重要生长因子。正常细胞的表面有,但很多肿瘤尤其是实体瘤细胞表面则有异常高水平的EGF受体的表毒早期区4第4编码蛋白,即腺病毒E4orf4蛋白(adenovirus early region ding frame 4 protein)可以特异地诱导肿瘤细胞发生不依赖p53表达的种新型的细胞毒因子。本研究旨在利用EGF的靶向性和E4orf4蛋白的,在分子水平设计合成一个融合蛋白,使其具有组成部分各自的生物学更多还原

【Abstract】 BACKGROUND & OBJECTIVE: Human epidermal growth factor (EGF), an important growth factor, may stimulate cell growth and proliferation. EGF receptor (EGFR) expresses on the surface of normal cells, and abnormally over-expresses on many kinds of tumor cells, especially on solid tumor cells. Adenovirus early region 4 open reading frame 4 protein (E4orf4) is a novel cytotoxin that can specifically induce p53-independent apoptosis in tumor cells. Based on the targeting of EGF and cytotoxicity of E4orf4, we proposed to design a novel fusion protein at molecular level by recombining EGF and E4orf4 to target and then kill tumor cells. METHODS: EGF and E4orf4 coding sequences were amplified by polymerase chain reaction (PCR), and then genetically fused by overlapping PCR. EGF-E4orf4 fragment was cloned into the yeast expression vector. Recombinant plasmid DNA was transformed into the yeast Pichia pastoris. Fusion proteins were purified by SP Sepharose ion exchange chromatography. Cytotoxicity of EGF-E4orf4 on cultured BT325 and MDA-MB-231 cells was detected by MTT assay, and cell apoptosis was measured by flow cytometry. RESULTS: The fusion fragment has 805 base pairs, which consists of Kozak consensus sequence, and the sequences encoding ?琢-factor signal peptide, EGF, flexible linker, and E4orf4. Recombinant plasmids pAO-EGF-E4orf4, and pAO-3EGF-E4orf4 were obtained, the latter contained 3 expression cassettes. Apparent molecular weight of fusion protein was 20 ku. Immunoblot analysis showed that the fusion protein was immunoreactive with rabbit-anti-human EGF polyclonal antibody. EGF-E4orf4 in high concentrations (5, and 0.5 ?滋g/ml) inhibited growth of BT325 and MDA-MB-231 tumor cells as compared with controls. Apoptosis was induced in 15.4%-28.2% of MDA-MB-231 cells by EGF-E4orf4 at the dosage of 10-25 ?滋g/3×105 cells. CONCLUSIONS: Fusion protein EGF-E4orf4 may enter cells mediated by EGFR, and thus inhibit growth of tumor cells.更多还原