Enhanced synergistic anti‐Lewis lung carcinoma effect of a DNA vaccine harboring a MUC1‐VEGFR2 fusion gene used with GM‐CSF as an adjuvant

In order to achieve a synergistic effect on anti‐tumour and anti‐angiogenesis activity, we designed and constructed a DNA vaccine that expresses MUC1and VEGFR2 in the same reading frame. The aim of this study was to investigate the anti‐tumour activity of this DNA vaccine. Furthermore, we also investigated the enhanced synergistic anti‐Lewis lung carcinoma effect of this DNA vaccine by using GM‐CSF as an adjuvant. A series of DNA plasmids encoding MUC1, VEGFR2, GM‐CSF, and their conjugates were constructed and injected into mice intramuscularly (i.m.) followed by an electric pulse. The humoral and cellular immune responses after immunization were detected by enzyme‐linked immunosorbent assay (ELISA) and enzyme‐linked immunospot (ELISPOT), respectively. To evaluate the anti‐tumour efficacy of these plasmids, murine models with MUC1‐expressing tumours were generated. After injection into the tumour‐bearing mouse model, the plasmid carrying the fusion gene of MUC1 and VEGFR2 showed stronger inhibition of tumour growth than the plasmid expressing MUC1 or VEGFR2 alone, which indicated that MUC1 and VEGFR2 could exert a synergistic anti‐tumour effect. Furthermore, mice vaccinated with the combination of the GM‐CSF expressing plasmid and the plasmid carrying the fusion gene of MUC1 and VEGFR2 showed an increased inhibition in the growth of MUC1‐expressing tumours and prolonged mouse survival. These observations emphasize the potential of the synergistic anti‐tumour and anti‐angiogenesis strategy used in DNA vaccines, and the potential of the GM‐CSF gene as an adjuvant for DNA vaccines, which could represent a promising approach for tumour immunotherapy.