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[Construction of energized fusion protein consisting of epidermal growth factor receptor oligopeptide ligand and lidamycin and its antitumor activity].

BACKGROUND AND OBJECTIVE
Epidermal growth factor receptor (EGFR) is abnormally overexpressed on many kinds of tumor cells. Lidamycin is an enediyne antibiotic with highly potent antitumor activity. This study was to construct a novel fusion protein by recombining EGFR specific oligopeptide ligand and lidamycin, and investigate its antitumor efficacy.


METHODS
The fusion protein (Ec-LDP) was expressed in E.coli and purified by affinity chromatography. The purity of Ec-LDP was analyzed by high performance liquid chromatography (HPLC). ELISA, flow cytometry (FCM) and immunofluorescence assay were used to analyze the binding activity of Ec-LDP to different cancer cell lines. The energized fusion protein Ec-LDP-AE was prepared by integrating the active enediyne chromophore (AE) of lidamycin into the Ec-LDP protein. The cytotoxicity of Ec-LDP-AE was measured by MTT assay.


RESULTS
Ec-LDP fusion protein was successfully constructed and secretorily expressed in E.coli, and the production of Ec-LDP protein was 18 mg per liter fermentation broth. The purity of Ec-LDP protein was 95.3%. Ec-LDP protein had strong binding activity to cancer cell lines highly expressing EGFR, such as MCF-7 and A431 cells. However, Ec-LDP had no binding activity to EGFR negative NIH 3T3 cells. The energized fusion protein Ec-LDP-AE showed potent cytotoxicity to MCF-7 and A431 cells with the half maximal inhibitory concentration (IC50) values of 3.06 x 10(-11) mol/L and 9.38 x 10(-13) mol/L, respectively.


CONCLUSION
The energized fusion protein Ec-LDP-AE binds to EGFR specifically and kills cancer cells efficiently.