Abstract 2833: Significant protection against gemcitabine-resistant pancreatic cancer cells with tumor lysate vaccine, engineered to express α-gal epitopes.

Abstract

Abstract Gemcitabine(Gem)-based chemotherapy is typically offered as a standard care of pancreatic cancer (PC) patients. However most of patients do not survive longer than 6 months, as the PC cells are naturally resistant to current chemotherapy. New therapeutic approaches need to be encouraged. Human natural anti-Gal is an IgG known to be presented in large amounts (∼1% of circulating IgG) in normal subjects and cancer patients. Anti-Gal specifically interacts with α-gal epitopes (Galα1, 3Galβ1, 4GlcNAc-R), synthesized by α1, 3 galactosyltransferase (α1, 3GT) on cell surface glycolipids and glycoproteins. We previously showed the in vitro and in vivo effectiveness of new immunotherapy by vaccination with whole PC cells, expressing α-gal epitopes (Cancer Res; 70(13); 5259-69, 2010). For the clinical development, we proposed that tumor lysate is a suitable source of tumor-associated antigens (TAAs), because it contains several known as well as unknown TAAs that could elicit an anti-tumor immune response against heterogeneous PC cell populations, including Gem-resistant PC cells (Gem-resi cells). In this study, we investigate whether vaccination by PC tumor lysate, expressingα-gal epitopes can efficiently induce anti-tumor response against both PC cells and gem-resi cells. A human PC cell line, PANC1 was transfected by 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 and homogenized. α1,3GT KO mice were pre-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 expressed ∼40 × 106 of these epitopes per 1mg of lysate. To demonstrate in vivo tumor destruction, an animal model was performed. Splenocytes from vaccinated KO mice were prepared, and these cells were transferred ip (30×106 cells/ip ×3 times) into NOD/SCID mice. Transferred mice were challenged with S.C. injection by either 1×107 of live PANC1 or gem-resi PANC1. PANC1 tumors in mice transferred from parental group reached the size of 100 mm2 at 40.3 days after injection. For tumors in mice from α-gal group, regrowth of tumor was completely prevented. Survival of α-gal transferred mice was prolonged [α-gal vs. parental: 82.5±21.9 vs. 48.0±6.7 days, p<0.0001]. For gem-resi tumors in mice from α-gal group, regrowth of them was markedly protected [size of 100 mm2; α-gal vs. parental: 74.3 vs. 37.4 days]. Survival was prolonged [α-gal vs. parental: 93.6±17.7 vs.46.2±7.3 days, p=0.0018]. In conclusion, immunotherapy with tumor lysate vaccine, expressing α-gal epitopes effectively targets both PC cells and gem-resi cells and may provide PC cure by the elimination of the replenishing pool of all PC cells. Citation Format: Masahiro Tanemura, Eiji Miyoshi, Tsukasa Tanida, Hiroaki Nagano, Hidetoshi Eguchi, Kenta Furukawa, Yuji Nonaka, Hirofumi Akita, Naoki Hama, Hiroshi Wada, Koichi Kawamoto, Shyogo Kobayashi, Kiyomi Taniyama, Wataru Kamiike, Masaki Mori, Yuichiro Doki. Significant protection against gemcitabine-resistant pancreatic cancer cells with tumor lysate vaccine, engineered to express α-gal epitopes. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2833. doi:10.1158/1538-7445.AM2013-2833