Abstract 2512: Novel immunotherapy using a tumor lysate vaccine with α-gal epitopes against pancreatic cancer

Abstract

Abstract Pancreatic cancer (PC) is a lethal disease that remains one of the most resistant to traditional therapies, so we are in urgent need of other therapies. Immunotherapies act differently than chemotherapy or radiotherapy and might be an alternative treatment modality to this deadly disease with significantly less toxicity. 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 showed effectiveness of tumor lysate vaccine engineered to α-gal epitopes (Int J Oncol, 2015). For clinical development of more effective immunotherapy, we proposed that human tumor lysate originated from resected PC is more suitable because it contains several TAAs that could elicit a marked anti-tumor response. The present study addresses the effectiveness of elicitation of both antibody production and in vivo destruction against PC by vaccination with human tumor lysate with α-gal epitopes enzymatically. Tumor specimens were obtained from 11 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 mice were vaccinated intraperitoneally by either unsynthesized (control group; group C) or α-gal tumor lysate (α-gal group; group A). Production of anti-PC cell Ab in group A was 8∼16-fold higher than that of group C. Also production of anti-TAA Ab in group A was 8∼16-fold higher than that of group C. Expansion of TAAs-specific B cells was significantly higher [number of spots at 1×106 splenocytes: MUC1: group A vs. C; 151±33 vs. 28±13 (p<0.001), Mesothelin: 97±26 vs. 36±19 (p = 0.03)]. In group A, we detected 828±180 spots of IFN-γ secreting T cells in the presence of the MUC1, and 988±232 spots were detected in the presence of the Mesothelin. In group C, 146±59 spots by the MUC1 and 384±219 spots by the Mesothelin were detected. The number of spots in the presence of TAA stimulation was significantly higher in group A than in group C. To demonstrate in vivo tumor destruction, an animal experiment was performed. Splenocytes from vaccinated KO mice were prepared, and then transferred intraperitoneally (90×106 cells) 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: 91.5 vs. 47.0 days (p<0.01)]. We conclude that immunotherapy with α-gal tumor lysate obtained from PC patients with enzymatic engineering could be more effective and practicable methods for PC treatment. Citation Format: Kenta Furukawa, Masahiro Tanemura, Eiji Miyoshi, Hiroaki Nagano, Masaki Wakasugi, Toru Masuzawa, Mitsuyoshi Tei, Kentaro Kishi, Hiroki Akamatsu, Hidetoshi Eguchi, Katsuyoshi Matsunami, Masaki Mori, Yuichiro Doki. Novel immunotherapy using a tumor lysate vaccine with α-gal epitopes against pancreatic cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2512. doi:10.1158/1538-7445.AM2015-2512