Abstract 5793: Functional DKK1 antibodies binding to cysteine-rich domain 1 or 2 of hDKK1 demonstrate antagonistic activities on tumor suppression or TCF/LEF signaling

Abstract Wnt signaling plays an important role in embryonic development and tumorigenesis. These biological effects are exerted by activation of the β-catenin/TCF transcription complex and consequent regulation of a set of downstream genes. DKK1 has been shown to be a potent inhibitor of Wnt signaling via competing Wnt binding to LRP5/6. DKK1 is tumorigenic in multiple cancer types and also immunosuppressive via MDSCs and NK cells. Emerging evidence indicates that DKK1 has been involved in T cell differentiation and induction of cancer evasion of immune surveillance by accumulating MDSCs. Consequently, DKK1 has become a promising target for cancer immunotherapy, and the mechanisms of DKK1 affecting cancers and immune cells have received great attention. With Twist’s precision DNA writing technologies, we have created phage display libraries with diversity greater than 1 × 1010, and utilized machine learning model for optimal discovery. In this study, we discovered anti-DKK1 antibodies bind to different cysteine-rich domain (CRD) of hDKK1 by epitope binning and mapping, and block the binding of DKK1 to the receptor. Binding of the antibodies to different CRDs of hDKK1 lead to different activation effect. The in vitro functional assays showed that the interaction of Wnt to its receptor was restored in the presence of anti-DKK1 antibodies binding to DKK1 CRD2, resulting in TCF/LEF signaling upregulation. Moreover, anti-DKK1 antibodies binding to DKK1 CRD1 induced immune cell activation and led to tumor cell cytotoxicity. In vivo study indicated anti-DKK1 antibody lead is potent in tumor regression. Our anti-DKK1 lead shows promising efficacy in cancer immunotherapy without influencing Wnt canonical pathway. Citation Format: Linya Wang, Zhen Han, Marisa Yang, Ana G. Lujan Hernandez, Vishwas Prabhu, Cameron F. Hu, Tammy Htoy, Mouna Villalta, Tom Z. Yuan, Hoa Giang, Aaron Sato. Functional DKK1 antibodies binding to cysteine-rich domain 1 or 2 of hDKK1 demonstrate antagonistic activities on tumor suppression or TCF/LEF signaling abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 5793.