Abstract 4737: IL-4 and CpG therapy suppresses the outgrowth of tumors by activating tumor-specific Th1-type immune responses.

Abstract

Abstract Although interleukin (IL) -4 is often regarded as a type-2 response inducer, recent studies have demonstrated that local IL-4 delivery at the site of vaccination activates local dendritic cells (DCs) and promote type-1 T cell responses. In particular, IL-4 supports DC maturation and enhances IL-12p70 secretion from DCs. Microbial molecules such as lipopolysaccharides, bacteriaderived RNA, and DNA are recognized by host cells through the TLR family, which belongs to the family of pattern-recognition receptors and stimulates immune responses. It has been reported that DNA vaccines and synthetic oligodeoxynucleotides (ODN) containing an unmethylated cytidine-phosphate-guanosine (CpG) motif promote Th1-type immune responses. CpG stimulates DCs through TLR9 and enhances DC maturation, which may improve the therapeutic effects on established tumors. In this study, we evaluated the antitumor effects of IL-4 gene therapy and CpG-ODN treatment in a poorly immunogenic murine cancer model. We used the IL-4 gene-overexpressing murine colorectal cancer MC38 cell line (MC38-IL4). Incubation with MC38-IL4 and CpG-ODN enhanced bone marrow-derived dendritic cell (DC) maturation in vitro. In addition, interferon (IFN)-γ production was significantly increased in naïve splenocytes after they were coincubated with MC38-IL4 and CpG-ODN. When mice bearing MC38 wild-type tumors were inoculated subcutaneously with MC38-IL4 cells and CpG-ODN, the outgrowth of established parental tumors was significantly suppressed compared to those in the MC38-IL4-treated group (IL-4 vs IL-4 + CpG-ODN, p= 0.015). A marked infiltration of CD8+ cells in the established parental tumors of mice treated with MC38-IL4 and CpG-ODN was confirmed by immunohistochemical analyses (MC38-IL4: 2.8 ± 1.9 cells/field vs MC38-IL4 + CpG-ODN: 20.7 ± 15.3 cells/field, p=0.027). Obvious tumor-specific cytolysis was detected when splenocytes of MC38-IL4 + CpG-ODN-treated mice were stimulated by γ-irradiated MC38-IL4 cells and CpG-ODN twice weekly in vitro and used as effector cells in a chromium-release assay (32.2% ± 3.5% for MC38 cells vs 3.2% ± 1.1% for YAC-1 cells; at an effector to target ratio of 40). These results suggest that IL-4 and CpG-ODN treatment promotes potent Th1-type antitumor immune responses. Therefore, the combination of IL-4 gene therapy and CpG-ODN treatment for cancer should be evaluated in clinical trials. Citation Format: Atsushi Kajiwara, Hiroyoshi Doi, Junichi Eguchi, Shigeaki Ishii, Ayako Sasagawa, Masaki Sakaki, Risa Omori, Eiichi Hayashi, Reiko Makino, Jin Yoshida, Kazumasa Hiroishi, Michio Imawari. IL-4 and CpG therapy suppresses the outgrowth of tumors by activating tumor-specific Th1-type immune responses. [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 4737. doi:10.1158/1538-7445.AM2013-4737