Abstract 4985: TLR agonists for anticancer immunotherapy

Abstract

Abstract Introduction: Toll-like receptors (TLRs) are important pattern recognition receptors through which innate immune cells recognize invasive microorganisms. The immunostimulatory property of TLR agonists allows for activation of dendritic cells (DCs) and enables their use as anticancer vaccine adjuvants. Because TLR 7 and 8 can be activated by synthetic small molecules, they are of particular interest as a target in vaccine adjuvant discovery. However, a key drawback of these synthetic small molecules is that they also induce immunosuppressive cytokines, resulting in immunosuppression. Methods: We have previously developed a suite of highly substituted imidazoquinolines, which potently activate TLR 7 and/or 8. In this study, we tested some selected TLR7, TLR8 and TLR7/8 dual agonists for their ability to activate DCs without inducing immune suppressive cytokines. Murine bone marrow-derived dendritic cells (BMDCs) were generated from C57BL/6 mice. BMDCs were treated with one of seven TLR agonists for 72 hrs. Cells were collected and stained for flow cytometry analysis, and the culture supernatants were examined for secretion of pro-inflammatory cytokines, IL-12p70 and IFN-γ, and an immunosuppressive cytokine, IL-10, by ELISA. We also investigated activation of T cells by these agonists. Human peripheral blood mononuclear cells (hPBMCs) from healthy donors were incubated with one of seven TLR agonists overnight and cells were analyzed by flow cytometry for the expression of T cell activation marker CD69 and production of IFN-γ. Results: All the TLR agonists investigated activated BMDCs, as evidenced by the upregulation of costimulatory markers CD40, CD80 and CD86 on DCs. In addition, all the agonists examined induced the secretion of IL-12p70 and IFN-γ. TLR 8 agonists showed the least induction of IL-10 secretion. All the TLR agonists activated both CD4 and CD8 T cells. TLR 8 agonists induced higher production of IFN-γ in both type of T cells than other candidates. Conclusion: Both TLR 8 and TLR 7/8 agonists activated BMDCs and stimulated strong pro-inflammatory cytokine production. However, TLR8 activation was associated with less immunosuppression. These results suggest that these new imidazoquinoline esters are promising candidates for use as anti-cancer vaccine adjuvants. Citation Format: Wenqiu Zhang, Hyunjoon Kim, Vidhi Khanna, David M. Ferguson, Thomas Griffith, Jayanth Panyam. TLR agonists for anticancer immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4985.