The Wnt/β-catenin pathway, which signals through the Frizzled (Fzd) receptor family and several coreceptors, has long been implicated in cancer. Here we demonstrate a therapeutic approach to targeting the Wnt pathway with a monoclonal antibody, OMP-18R5. This antibody, initially identified by binding to Frizzled 7, interacts with five Fzd receptors through a conserved epitope within the extracellular domain and blocks canonical Wnt signaling induced by multiple Wnt family members. In xenograft studies with minimally passaged human tumors, this antibody inhibits the growth of a range of tumor types, reduces tumor-initiating cell frequency, and exhibits synergistic activity with standard-of-care chemotherapeutic agents.differentiation | cancer stem cell | pancreatic | breast | lung

Previous studies have shown that blocking DLL4 signaling reduced tumor growth by disrupting productive angiogenesis. We developed selective anti-human and anti-mouse DLL4 antibodies to dissect the mechanisms involved by analyzing the contributions of selectively targeting DLL4 in the tumor or in the host vasculature and stroma in xenograft models derived from primary human tumors. We found that each antibody inhibited tumor growth and that the combination of the two antibodies was more effective than either alone. Treatment with anti-human DLL4 inhibited the expression of Notch target genes and reduced proliferation of tumor cells. Furthermore, we found that specifically inhibiting human DLL4 in the tumor, either alone or in combination with the chemotherapeutic agent irinotecan, reduced cancer stem cell frequency, as shown by flow cytometric and in vivo tumorigenicity studies.

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