Immune-Based Therapy With Human Tumor Lysate, Expressing Alpha-Gal Epitopes Induce Significant B Cell Response And In Vivo Tumor Destruction Against Pancreatic Cancer

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Current strategies in the treatment of advanced pancreatic cancer (PC) offer little hope for a cure. Now treatment modalities, including immunotherapy are warranted for PC, which easily metastasizes in many organs. Although MUC1 and Mesothelin are potential targets for the immunotherapy, vaccination against a single tumor-associated antigen (TAA) seems to be insufficient. In our previous study, we showed the in vitro and in vivo effectiveness of immunotherapy though vaccination with whole PC cells engineered to express α-gal epitopes (Cancer Res; 70(13); 5259-69, 2010). It was thought that the immunogenicity of well-known as well as unknown multiple TAAs in cancer cells was upregulated by addition of α-gal epitopes and these TAAs ultimately lead to polyclonal expansion of both B and T cells. 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 from PC patients, expressing 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. For synthesis of α-gal epitopes, tumor tissues were homogenized in MES buffer, and incubated with MnCl2, UDP-Gal and α1,3GT for 4 hours at 37°C. 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) or α-gal tumor lysate (α-gal group). Production of anti-PC cell Ab in α-gal group was 4∼8-fold higher than that of control group. Anti-TAA Ab production was also markedly increased in comparison with that in control group (anti-MUC1 2-fold, anti-Mesothelin 4-fold). Expansion of TAAs-specific B cells was significantly higher [number of spots at 1×106 splenocytes: MUC1: α-gal vs. control; 414±26 vs. 178±46 (p=0.015), Mesothelin: 401±56 vs. 209±19 (p=0.03)]. 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 α-gal group, regrowth of tumors was significantly prevented and survival period was significantly prolonged [α-gal vs. control: 91.5 vs. 43.3 days (p=0.03)]. 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, Hidetoshi Eguchi, Toshimitsu Irei, Masashi Inoue, Shinya Yamashita, Yoshito Tomimaru, Naoki Hama, Hiroshi Wada, Koichi Kawamoto, Shogo Kobayashi, Katsuyoshi Matsunami, Kiyomi Taniyama, Wataru Kamiike, Masaki Mori, Yuichiro Doki. Immune-based therapy with human tumor lysate, expressing α-gal epitopes induce significant B cell response and in vivo tumor destruction against pancreatic cancer. [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 2884. doi:10.1158/1538-7445.AM2014-2884