Abstract B29: High efficacy of α-gal epitopes immune-based therapy against pancreatic cancer using tumor cell lysates.

Abstract

Current strategies in the treatment of metastasized 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 lysates. 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 x 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-MUC1 Ab. In contrast, sera from α-gal group showed positive bands that bound to not only MUC1 but also different TAAs in PANC1 cells. Thus, all immunoractions were much higher in vaccination groups of tumor lysate than that of cell lysates. These results suggested that vaccination with tumor lysate, remodeled to express α-gal epitopes enabled the immune system to generate a multiclonal B- and T-cell responses against a broad spectrum of tumor antigens and can provide a chance to develop the potential immunotherapy for patients with pancreatic cancer. Citation Format: Eiji Miyoshi, Masahiro Tanemura, Tsukasa Tanida, Takahiro Deguchi, Yuji Nonaka, Hiroaki Nagano, Masaki Mori, Yuichiro Doki. High efficacy of α-gal epitopes immune-based therapy against pancreatic cancer using tumor cell lysates. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Progress and Challenges; Jun 18-21, 2012; Lake Tahoe, NV. Philadelphia (PA): AACR; Cancer Res 2012;72(12 Suppl):Abstract nr B29.