Abstract 2572: CpG oligodeoxynucleotide enhances the efficacy of anticancer monoclonal antibody in an in vivo xenograft model using human endometrial cancer cell

Abstract

Abstract Background: CpG oligodeoxynucleotides (ODN) has been shown to exhibit a potent immunostimulatory activity. Therefore, CpG ODN has been considered to be a promising material for enhancing the therapeutic effect of anticancer monoclonal antibody. We have previously identified bone marrow stromal antigen 2 (BST2) as a therapeutic target of endometrial cancer cells and also demonstrated that an anti-BST2 antibody showed a potent anti-tumor effect by antibody-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) against BST2 positive cells. The aim of this study was to evaluate the synergistic anti-tumor effect by combination of anti-BST-2 antibody and CpG ODN, and to clarify the mechanisms of its anti-tumor effect, using xenograft model of anti-BST2 positive endometrial cancer cells. Material and Method: We implanted 7-8 week-old female SCID mice with 5×106 HEC-88 nu endometrial cancer cells subcutaneously. Mice with tumor were treated by intra-peritoneal injection of an anti-BST2 antibody alone (0 - 200 μg/mouse, twice a week for four weeks), intra-tumoral injection of CpG ODN alone (0 - 30 μg/mouse, twice a week for four weeks) or combination therapy (anti-BST2 antibody and CpG ODN). Anti-tumor effect was evaluated by monitoring the changes of tumor volume and also pathological analysis. In addition, activation of NK cells was evaluated. Results: Intraperitoneal treatment of anti-BST2 antibody showed a significant anti-tumor effect, dose dependently. Similarly, intratumoral injection of CpG ODN showed a significant anti-tumor effect, in a dose dependent manner. Interestingly, the combination therapy was more effective than the single-agent therapy. In addition, the combination therapy also resulted in a high activity of NK cells. Conclusion: We showed that CpG ODN increases the efficacy of anti-tumor effect of anti-BST2 antibody induced ADCC activity via potentiating NK cells mediated cancer cell injury. Combination of CpG ODN and anti-tumor monoclonal antibody is useful cancer therapy. Citation Format: Kosuke Hiramatsu, Satoshi Serada, Kouji Kobiyama, Akiko Morimoto, Toshihiro Kimura, Kiyoshi Yoshino, Minoru Fujimoto, Ken J. Ishii, Masami Fujita, Tetsuji Naka. CpG oligodeoxynucleotide enhances the efficacy of anticancer monoclonal antibody in an in vivo xenograft model using human endometrial cancer cell. [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 2572. doi:10.1158/1538-7445.AM2014-2572