Abstract 2355: Strong immune responses to pancreatic cancer cells induced by human tumor lysate vaccine remodeled to express α-gal epitopes and their implication for a universal vaccine
Authors: Furukawa Kenta , Tanemura Masahiro , Miyoshi Eiji , Hata Tomoki , Kishi Kentaro , Akamatsu Hiroki , Eguchi Hidetoshi , Mori Masaki , Doki Yuichiro 
Published: July 2016

Pancreatic cancer (PC) is a lethal disease that remains one of the most resistant to traditional therapies. We are in urgent need of other therapies. Immunotherapy designed to target tumor-associated antigens (TAAs) is a promising treatment approach for PC. But vaccination against a single TAA seems to be insufficient. In our previous study, we showed effectiveness vaccination by whole PC cells, engineered to express α-gal epitopes (Cancer Res, 2010). Subsequently we investigated strong immune response of tumor lysate vaccine engineered to express α-gal epitopes (Int J Oncol, 2015). In this study, for developing clinical application of this immunotherapy, we investigated the effects of vaccination with human PC tumor lysate obtained from PC patients, expressing α-gal epitopes.

Tumor specimens were obtained from 11 PC patients at the time of surgical resection. To express α-gal epitopes, we cloned the α1,3galactosyltransferas (α1,3GT) from a New World Monkey and expressed it in a soluble form in the yeast expression system of Pichia pastoris. α1,3GT KO mice were immunized with pig tissue to generate anti-Gal Ab in their sera. These high anti-Gal KO mice were vaccinated intraperitoneally by either unsynthesized (control group; group C) or α-gal tumor lysate (α-gal group; group A).

Vaccination with α-gal PC tumor lysate elicited strong immune responses of anti-PC cell IgG and anti-PC TAAs, including MUC1 and Mesothelin. Productions of anti-PC cell IgG in group A were 8∼32-fold higher than those of group C. Furthermore, productions of anti-MUC1 and of ant-Mesothelin Ab in group A were 4∼8-fold higher than those of group C. Expansion of TAAs (MUC1 and Mesothelin)-specific B cells was significantly higher [MUC1: spots of group A vs. C = 151 vs. 28 (p&lt;0.001), Mesothelin: 97 vs. 36 (p = 0.03)]. The number of spots of IFN-γ secreting T cells in the presence of MUC1 and Mesothelin peptide stimulation was significantly higher in group A than in group C [MUC1: 828 vs. 146 (p&lt;0.001), Mesothelin: 988 vs. 384 (p = 0.02)].

To demonstrate in vivo tumor destruction, an animal experiment was performed. Splenocytes from vaccinated KO mice were prepared, and then transferred intraperitoneally into NOD/SCID mice. Followed by transferring, mice were challenged with 1×107 of live PANC-1 cells. In mice from group A, regrowth of tumors was significantly prevented and survival period was significantly prolonged [group A vs. C = 95.0 vs. 45.0 days (p&lt;0.001)]. In the immunohistochemical analysis, the tumor created in NOD/SCID mice from group A was shown severe central necrosis and strong infiltration of CD4+ and CD8+ T cells and macrophages into the periphery. In contrast, the tumor obtained from NOD/SCID mice of group C indicated no lymphocytic infiltration.

We conclude that the use of human PC tumor lysate vaccine, remodeled to express α-gal epitopes can elicited strong immune responses to pancreatic cancer.

Citation Format: Kenta Furukawa, Masahiro Tanemura, Eiji Miyoshi, Tomoki Hata, Kentaro Kishi, Hiroki Akamatsu, Hidetoshi Eguchi, Masaki Mori, Yuichiro Doki. Strong immune responses to pancreatic cancer cells induced by human tumor lysate vaccine remodeled to express α-gal epitopes and their implication for a universal vaccine. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2355.