Abstract 2560: Strong cross-reactive responses to pancreatic cancer cells induced by α-gal epitopes-expressing tumor lysate and their implications for a universal cancer vaccine

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA We investigated the effects of whole cell vaccination with α-gal epitopes-expressing pancreatic cancer (PC) cells (Cancer Res; 70 (13); 5259-69, 2010) and examined the usefulness of this vaccine in the induction of specific anti-tumor-responses and improvement of survival. But, these effects were somewhat weak. We hypothesized that tumor lysate (t-ly), which contains many tumor-associated antigens (TAAs) of both PC and stromal cells is a suitable vaccination material and it can elicit a broadly protective anti-tumor responses. In this study, we investigate that vaccination with α-gal epitopes-expressing PC t-ly can induce cross-reactive protections to heterosubtypic PC cells. Human PC cell lines, BxPC3 (Bx), expressing Mesothelin, and MiaPaCa (Mia), expressing MUC1 were employed. PC cell lines were injected s.c. into NOD/SCID mice. The grown tumors were enucleated and homogenized for making t-ly. To synthesize α-gal epitopes on t-ly, we cloned the α1,3 galactosyltransferase (α1,3GT) cDNA from a New World monkey and isolated a soluble form of enzyme in the yeast expression system of Pichia pastoris. These t-lys were incubated with UDP-Gal and α1,3GT. α1,3GT KO mice were immunized with pig tissues to produce anti-Gal Ab. The high anti-Gal KO mice were vaccinated intraperitoneally by either parental (control group; Bx-t-ly or Mia-t-ly) or α-gal-t-ly (α-gal group; α-gal-Bx-t-ly or α-gal-Mia-t-ly). No expression of α-gal epitopes were observed in parental t-lys, whereas high expression levels were clearly detected on α-gal-t-lys. α-gal-Bx-t-ly vaccination elicited strong responses of anti-Bx IgG and anti-Mesothelin IgG, whereas Bx-t-ly vaccination did not induce such Ab responses. For Mia-t-ly vaccination, KO mice of α-gal group clearly induce anti-Mia IgG and anti-MUC1 IgG, but no Ab responses were observed in control group. Productions of either anti-Bx or anti-Mia IgG in α-gal group were 64-fold higher than those in control group. α-gal-Bx-t-ly vaccinated KO mice abundantly produced cross-reactive IgG Abs to Mia cells, whereas no cross-reactive humoral responses to Mia cells were induced by Bx-t-ly vaccine. Vaccinated mice sera from α-gal-Mia-t-ly strongly cross-react to Bx cells. To demonstrate in vivo tumor destruction, splenocytes from vaccinated KO mice were prepared, and these splenocytes were inoculated i.p. into NOD/SCID mice. Either live Bx or Mia cells were challenged with s.c. injection. Both Bx and Mia tumors in mice inoculated from parental group reached the size of 100 mm2 at approximately 22 days after injection. For tumors in mice transferred from α-gal group, no regrowth tumors were identified. We conclude that α-gal epitopes-expressing t-ly vaccine can elicit durable and broadly protective immune response to subtypic PC cells, and that such vaccination may provide implications for a universal cancer vaccine to cure for the patients with PC. Citation Format: Masahiro Tanemura, Eiji Miyoshi, Hiroaki Nagano, Masafumi Inoue, Toshimitsu Irei, Shinya Yamashita, Kenta Furukawa, Katsuyoshi Matsunami, Wataru Kamiike, Masaki Mori, Yuichiro Doki. Strong cross-reactive responses to pancreatic cancer cells induced by α-gal epitopes-expressing tumor lysate and their implications for a universal cancer vaccine. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2560. doi:10.1158/1538-7445.AM2014-2560