Functional DKK1 antibodies demonstrate antagonistic and tumor suppression activities

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 1e10, and utilized machine learning model for optimal discovery. In this study, we discovered anti-DKK1 antibodies blocking the binding of DKK1 to the receptor. The in vitro functional assays showed that the interaction of Wnt to its receptor was restored in the presence of anti-DKK1 antibodies, resulting in TCF/LEF signaling upregulation. Moreover, anti-DKK1 antibodies induced immune cell activation, and led to tumor cell cytotoxicity. In addition, anti-DKK1 antibodies binding to different domains of DKK1 led to different functional effect. In vivo study indicated anti-DKK1 antibodies is potent in tumor regression. Our anti-DKK1 leads shows promising efficacy in cancer immunotherapy.