Abstract 1286: Oral administration of poly gamma glutamic acid significantly enhances the antitumor immune response of doxorubicin in a murine cancer model through regulating tumor microenvironment

Abstract Immunogenic cell death (ICD) is a type of cancer cell death triggered by certain chemotherapeutic drugs, oncolytic viruses, and other therapies. In particular, doxorubicin (DOX), one of the chemo-drugs, is well known to induce ICD, which involves the activation of the immune system against cancer in immunocompetent hosts. ICD comprises the release of damage-associated molecular patterns (DAMPs) from dying tumor cells that result in the activation of tumor-specific immune responses, thus eliciting long-term efficacy of anticancer drugs by combining direct cancer cell killing and antitumor immunity. However, the antitumor immunity can be achieved by overcoming the immunosuppressive tumor microenvironment (TME). Most current treatment strategies harnessing the tumor microenvironment focus on T cell-immune response, either by promoting activating signals or suppressing inhibitory ones.We here present a novel approach to cope with the inhibitory TME, combinatory treatment of DOX with poly gamma glutamic acid (γ-PGA). PGA, a safe edible biomaterial secreted by B. subtillis, has been evaluated in the clinical trials with the patients diagnosed as cervical intraepithelial neoplasia 1 (CIN 1). From the study using murine cancer models, including MC38, we found the combinatory treatment with γ-PGA restored the downregulation of NK cell activity caused by DOX, enhanced ICD and T cell responses, and reduced proinflammatory cytokines in the tumor tissues. Taken together, co-administration of γ-PGA exhibited synergistic anti-cancer effects by favoring the immunosuppressive TME in the combinatory treatment with conventional chemo-drugs. Citation Format: Joungwoo Choi, Solmin Jung, Yena Oh, Jaepyeong Jang, Yeondong Cho, Do young Lee, Youngcheol Park, Kwangil Jeong. Oral administration of poly gamma glutamic acid significantly enhances the antitumor immune response of doxorubicin in a murine cancer model through regulating tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1286.