A novel recombinant human Frizzled-7 protein exhibits anti-tumor activity against triple negative breast cancer via abating Wnt/β-catenin pathway

Triple negative breast cancer (TNBC) is one of the most difficult malignancy to treat due to a lack of targeted therapy. Studies have demonstrated that the activation of Wnt/β-catenin signaling was preferentially found in TNBC. Frizzled-7 (Fzd7), one of the Wnt receptors, was significantly up-regulated in TNBC and modulated TNBC tumorigenesis through the Wnt signaling pathway, indicating Fzd7 is a biomarker and a potential therapeutic target for TNBC. Here, we designed a recombinant soluble peptide fragment (rhFzd7) to antagonize Fzd7 by competitively binding with Wnt ligands. We demonstrated the ability of rhFzd7 to bind to its ligand, Wnt3a, and monitored the kinetic process using a Biacore X100 system. In addition, the anti-tumor and anti-angiogenic activity of rhFzd7 were studied in vitro and in vivo. Results showed that the purified rhFzd7 pulled down Wnt3a from MDA-MB-231 cells and exhibited high affinity with Wnt3a (KD: 3.41 × 10−8 M). The data in vitro revealed that rhFzd7 inhibited proliferation and invasion of TNBC cells, and induced apoptosis of TNBC cells effectively. The anti-angiogenic assay indicated that rhFzd7 repressed TNBC angiogenesis in vitro and in vivo. Furthermore, the study in vivo showed that rhFzd7 could sensitize TNBC cells to the anti-tumor effect of Docetaxel. In conclusion, the generation of rhFzd7 lays foundation for the screening of anti-Fzd7 antibody, and this novel design provides an effective candidate for the clinical treatment of TNBC.