The anti-tumour effect of a DNA vaccine carrying a fusion gene of human VEGFR2 and IL-12

Because of tumour dependence on angiogenesis, anti-angiogenic therapy has become the most attractive area of basic and clinical study in the field of cancer research. In order to create a synergistic effect on angiogenesis and immune regulation, we designed and constructed a new type of DNA vaccine that can express VEGFR2 (vascular endothelial growth factor receptor 2) and the prostate cancer antigen IL-12 (interleukin 12) in the same reading frame. The aim of this study was to investigate the anti-tumour activity of a eukaryotic expression plasmid carrying a fusion gene of human VEGFR2 and IL-12. According to the gene sequences in GenBank, we synthesized the human VEGFR2 and IL-12 genes. VEGFR2 and IL-12 were joined by a sequence encoding a Furin recognition site and a 2A cleavage site, and the resulting fusion gene was cloned into the eukaryotic expression vector pVAX1 to construct the expression plasmid pVAX1-VEGFR2-F2A-IL-12. The expression of VEGFR2 and IL-12 could be detected in 293T cells transfected with pVAX1-VEGFR2-F2A-IL-12 by enzyme-linked immunosorbent assay. Each of these proteins, and in particular co-expression of both proteins, can result in humoral and cellular immune responses in C57BL/6 mice. After injection into the tumour-bearing mouse model, the plasmid showed stronger inhibition of tumour growth than a plasmid expressing VEGFR2 alone. Our results demonstrate that a DNA vaccine carrying a fusion gene of human VEGFR2 and IL-12 could represent a promising approach for tumour immunotherapy.