A fusion protein targeting the vascular endothelial growth factor receptor I (VEGFR-1)

Diphtheria toxin is an exotoxin secreted by Corynebacterium diphtheriae that has been lysogenized by P bacteriophage that carries the DT gene. It blocks protein synthesis and kills the target eukaryotic cell. The R82A, K84A, H86A mutant of vascular endothelial growth factor (VEGF) specially binds its receptor 1 (VEGFR-1) that is expressed highly on surface of tumor blood vessel. DT genomic DNA was extracted first and then the gene that coding the T domain and C domain of DT (DT391) were amplified. The R82A, K84A, H86A mutant were introduced to VEGF by site-directed mutagenesis. Then a VEGFR-I targeting fusion protein, DT391-mVEGF, was constructed by substituting the receptor binding domain of DT with the VEGF mutant which shows high affinity to a receptor expressed on tumor vascular. With DT391, a protein without the mVEGF domain of DT391-mVEGF, as a negative control in cytotoxicity assay, the hybrid protein DT391-mVEGF showed an inhibition to the growth of VEGFR-1 positive tumor cell.