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

Deregulation of the b-catenin signaling has long been associated with cancer. Intracellular components of this pathway, including axin, APC, and b-catenin, are frequently mutated in a range of human tumors, but the contribution of specific extracellular ligands that promote cancer development through this signaling axis remains unclear. We conducted a reporter-based screen in a panel of human tumors to identify secreted factors that stimulate b-catenin signaling. Through this screen and further molecular characterization, we found that R-spondin (RSPO) proteins collaborate with Wnt proteins to activate b-catenin. RSPO family members were expressed in several human tumors representing multiple malignancies, including ovarian, pancreatic, colon, breast, and lung cancer. We generated specific monoclonal antibody antagonists of RSPO family members and found that anti-RSPO treatment markedly inhibited tumor growth in human patient-derived tumor xenograft models, either as single agents or in combination with chemotherapy. Furthermore, blocking RSPO signaling reduced the tumorigenicity of cancer cells based on serial transplantation studies. Moreover, geneexpression analyses revealed that anti-RSPO treatment in responsive tumors strongly inhibited b-catenin target genes known to be associated with cancer and normal stem cells. Collectively, our results suggest that the RSPO family is an important stimulator of b-catenin activity in many human tumors and highlight a new effective approach for therapeutically modulating this fundamental signaling axis. Cancer Res; 76(3); 713-23. Ó2015 AACR.

The receptor tyrosine kinase MET is a major component controlling the invasive growth program in embryonic development and in invasive malignancies. The discovery of therapeutic antibodies against MET has been difficult, and antibodies that compete with hepatocyte growth factor (HGF) act as agonists. By applying phage technology and cell-based panning strategies, we discovered two fully human antibodies against MET (R13 and R28), which synergistically inhibit HGF binding to MET and elicit antibody-dependent cellular cytotoxicity. Cell-based phosphorylation assays demonstrate that R13 and R28 abrogate HGF-induced activation of MET, AKT1, ERK1/2, and HGF-induced migration and proliferation. FACS experiments suggest that the inhibitory effect is mediated by "locking" MET receptor in a state with R13, which then increases avidity of R28 for the extracellular domain of MET, thus blocking HGF binding without activating the receptor. In vivo studies demonstrate that the combination of R13/28 significantly inhibited tumor growth in various colon tumor xenograft models. Inhibition of tumor growth was associated with induction of hypoxia. Global gene expression analysis shows that inhibition of HGF/MET pathway significantly upregulated the tumor suppressors KLF6, CEACAM1, and BMP2, the negative regulator of phosphatidylinositol-3-OH-kinase PIK3IP1, and significantly suppressed SCF and SERPINE2, both enhancers of proliferation and invasiveness. Moreover, in an experimental metastasis model, R13/28 increased survival by preventing the recurrence of otherwise lethal lung metastases. Taken together, these results underscore the utility of a dual-antibody approach for targeting MET and possibly other receptor tyrosine kinases. Our approach could be expanded to drug discovery efforts against other cell surface proteins.

Resting and activated subpopulations of CD4+CD25+CD127loT regulatory cells (Treg) and CD4+CD25+CD127+ effector T cells in MS patients and in healthy individuals were compared. Peripheral blood mononuclear cells isolated using Ficoll Hypaque were stained with monoclonal antibodies and analysed by flow cytometer. CD45RA and Foxp3 expression within CD4+ cells and in CD4+CD25+CD127loT cells identified Population I; CD45RA+Foxp3+, Population II; CD45RA−Foxp3hi and Population III; CD45RA−Foxp3+ cells. Effector CD4+CD127+ T cells were subdivided into Population IV; memory /effector CD45RA− CD25−Foxp3− and Population V; effector naïve CD45RA+CD25−Foxp3−CCR7+ and terminally differentiated RA+ (TEMRA) effector memory cells. Chemokine receptor staining identified CXCR3+Th1-like Treg, CCR6+Th17-like Treg and CCR7+ resting Treg. Resting Treg (Population I) were reduced in MS patients, both in untreated and treated MS compared to healthy donors. Activated/memory Treg (Population II) were significantly increased in MS patients compared to healthy donors. Activated effector CD4+ (Population IV) were increased and the naïve/ TEMRA CD4+ (Population V) were decreased in MS compared to HD. Expression of CCR7 was mainly in Population I, whereas expression of CCR6 and CXCR3 was greatest in Populations II and intermediate in Population III. In MS, CCR6+Treg were lower in Population III. This study found MS is associated with significant shifts in CD4+T cells subpopulations. MS patients had lower resting CD4+CD25+CD45RA+CCR7+ Treg than healthy donors while activated CD4+CD25hiCD45RA−Foxp3hiTreg were increased in MS patients even before treatment. Some MS patients had reduced CCR6+Th17-like Treg, which may contribute to the activity of MS.