A plasmid DNA vaccine encoding the extracellular domain of porcine endoglin induces anti-tumour immune response against self-endoglin-related angiogenesis in two liver cancer models.

BACKGROUND: Anti-angiogenesis therapy has showed a promising future in tumour treatment. More and more evidence suggest that endoglin is a powerful marker of angiogenesis in solid malignancies, including liver cancer. AIM: To explore whether a plasmid DNA encoding the porcine endoglin has the ability of breaking immune tolerance against endoglin-related tumour angiogenesis in mice. METHODS: A eukaryotic plasmid encoding the extracellular domain of porcine endoglin was constructed, and then used it as a xenogeneic DNA vaccine. Hepa1-6 and H22 hepatoma models were established to observe the anti-tumour activities. Western blot, enzyme-linked immunoadsorbent assay and enzyme-linked immunospot assay were used to determine the antibody characters. Immunohistochemistry and alginate-encapsulated tumour cell assay were used to observe the anti-angiogenesis effects. RESULTS: Immunotherapy with recombinant plasmid encoding extracellular domain of porcine endoglin was effective at both protective and therapeutic anti-tumour immunity in two hepatoma models. Autoantibodies against murine endoglin were identified. IgG1 and IgG2b were the major subclasses in response to recombinant plasmid encoding extracellular domain of porcine endoglin vaccination. Anti-endoglin antibody-producing B cells were significantly increased in the spleens of mice immunised with recombinant plasmid encoding extracellular domain of porcine endoglin. In addition, mouse self-immunoglobulins were found deposited on the blood vessels of recombinant plasmid encoding extracellular domain of porcine endoglin-immunised tumour tissues. The similar anti-tumour activity was induced by the adoptive transfer of the purified immunoglobulins from the sera of mice immunised with recombinant plasmid encoding extracellular domain of porcine endoglin. Furthermore, angiogenesis was apparently inhibited within the tumour tissues from the recombinant plasmid encoding extracellular domain of porcine endoglin-immunised mice, and the vascularisation of alginate balls was also reduced in recombinant plasmid encoding extracellular domain of porcine endoglin-immunised mice. Most importantly, recombinant plasmid encoding extracellular domain of porcine endoglin could really induce cytotoxic T lymphocyte-mediated cytotoxicity and inhibit cell proliferation against endothelial cells. In addition, both CD4+ and CD8+ T lymphocytes took part in the function of inhibiting tumour growth and were synergistically responsible for induction of the anti-tumour activities. CONCLUSIONS: This approach may provide an alternative strategy for liver cancer immunotherapy.

Correlations of structure and rates of energy transfer for through-bond energy-transfer cassettes.

Fluorescent DNA-labeling cassettes are designed to have a common absorbing chromophore matched to a single exciting laser wavelength, but up to four different emitters. Experiments reported here have examined the energy-transfer rates and fluorescence polarization characteristics for two different types of cassette, involving three distinct relative orientations of the donor and acceptor transition moments and the axis of the rigid linker. Energy-transfer times range from <200 fs to approximately 20 ps, the fastest transfer times occurring when the transition moments of the donor and acceptor species are aligned parallel to the linker axis. Experimental evidence is presented that supports a through-bond energy-transfer mechanism, in contrast with a commercial DNA-labeling agent, which exhibits much slower transfer times controlled by FRET. These rigid cassettes also exhibit polarized fluorescence from the acceptor species, so that this particular type of DNA-labeling probe has some of the advantages of single-molecule probes such as rhodamine and coumarin dyes.