Identification and functional validation of FZD8-specific antibodies.

The Wnt pathway is an evolutionarily conserved pathway involved in stem cell homeostasis and tissue regeneration. Aberrant signaling in the Wnt pathway is highly associated with cancer. Developing antibodies to block overactivation of Frizzled receptors (FZDs), the main receptors in the Wnt pathway, is one of the viable options for treating cancer. However, obtaining isoform-specific antibodies is often challenging due to the high degree of homology among the ten FZDs. In this study, by using a synthetic library, we identified an antibody named pF8_AC3 that preferentially binds to FZD8. Guided by the structure of the complex of pF8_AC3 and FZD8, a second-generation targeted library was further constructed, and finally, the FZD8-specific antibody sF8_AG6 was obtained. Cell-based assays showed that these antibodies could selectively block FZD8-mediated signaling activation. Taken together, these antibodies have the potential to be developed into therapeutic drugs in the future.