Abstract 1560: Immune-based therapy with tumor lysate remodeled to express α-gal epitopes induce significant B- and T-cell responses against pancreatic cancer

Current strategies in the treatment of pancreatic cancer (PC) offer little hope for a cure. New treatment modalities, including immunotherapy are warranted for this type of cancer. In our previous study, we showed the in vitro and in vivo effectiveness of immunotherapy through vaccination with whole PC cells, remodeled to express α-gal epitopes (Cancer Res; 70(13); 5259-69, 2010). It was thought that the immunogenicity of well-characterized as well as uncharacterized multiple TAAs contained in cancer cells was upregulated by α-gal epitopes and these TAAs ultimately leaded to polyclonal expansion of both B and T cells. For the clinical development of more effective immunotherapy, we proposed that tumor lysate is a suitable source of TAAs, because it contains several known as well as unknown TAAs that could elicit an anti-tumor immune response. In this study, we investigated whether vaccination with PC tumor lysate, expressing α-gal epitopes can efficiently induce T cell response and antibody production against multiple TAAs. A human PC cell line, PANC1, which expresses MUC1 was employed and transfected with α1,3GT gene (α-gal PANC1), 2 × 106 of either parental or α-gal PANC1 were injected s.c. into NOD/SCID mice. The grown PANC1 tumors were enucleated for generating tumor lysate. α1,3GT KO mice were immunized with pig tissues to produce anti-Gal in their sera like human. These mice were vaccinated intraperitoneally by 10 mg of either parental (control group) or α-gal PANC1 tumor lysate (α-gal group). Tumor lysate of parental PANC1 lacked of α-gal epitopes and it of α-gal PANC1 clearly expressed ∼40 × 106 of these epitopes per 1mg of lysate. These tumor lysates express MUC1 at similar level. Specific proliferation, assessed by CFSE assay of both CD4+ and CD8+ T cells responses to either MUC1 peptide or PANC1 tumor lysate in α-gal group were significantly higher in comparison with these in control group [MUC1; CD4+ T cell: α-gal vs control; 12.1±3.7 vs 2.0±0.7% (p=0.0058), MUC1; CD8+ T cell: α-gal vs control; 8.2±1.4 vs 3.8±0.9% (p=0.036), Tumor lysate; CD4+ T cell: α-gal vs control; 71.3±7.0 vs 7.9±1.0% (p=0.0005), tumor lysate; CD8+ T cell: α-gal vs control; 20.2±2.8 vs 7.1±0.7% (p=0.0054)]. To prove the antibody production response to multiple TAAs, the presence of immunostained PANC1 proteins was investigated by Western blots, using mice sera before/after vaccination. The sera from control group did not display obvious bands that were recognized by anti-M