ABSTRACT
Wnt-induced ß-catenin-mediated transcription is a driving force for stem cell self-renewal during adult tissue homeostasis. Enhanced Wnt receptor expression due to mutational inactivation of the ubiquitin ligases RNF43/ZNRF3 recently emerged as a leading cause for cancer development. Consequently, targeting canonical Wnt receptors such as LRP5/6 holds great promise for treatment of such cancer subsets. Here, we employ CIS display technology to identify single-domain antibody fragments (VHH) that bind the LRP6 P3E3P4E4 region with nanomolar affinity and strongly inhibit Wnt3/3a-induced ß-catenin-mediated transcription in cells, while leaving Wnt1 responses unaffected. Structural analysis reveal that individual VHHs variably employ divergent antigen-binding regions to bind a similar surface in the third ß-propeller of LRP5/6, sterically interfering with Wnt3/3a binding. Importantly, anti-LRP5/6 VHHs block the growth of Wnt-hypersensitive Rnf43/Znrf3-mutant intestinal organoids through stem cell exhaustion and collective terminal differentiation. Thus, VHH-mediated targeting of LRP5/6 provides a promising differentiation-inducing strategy for treatment of Wnt-hypersensitive tumors.
Subject(s)
Low Density Lipoprotein Receptor-Related Protein-5/chemistry , Low Density Lipoprotein Receptor-Related Protein-6/chemistry , Organoids/drug effects , Single-Domain Antibodies/chemistry , Stem Cells/drug effects , Wnt3A Protein/genetics , Animals , Binding Sites , Cell Differentiation , Cell Line, Tumor , Cell Proliferation , Crystallography, X-Ray , Fibroblasts/cytology , Fibroblasts/drug effects , Fibroblasts/metabolism , Gene Expression Regulation , HEK293 Cells , Humans , Intestine, Small/cytology , Intestine, Small/drug effects , Intestine, Small/metabolism , Low Density Lipoprotein Receptor-Related Protein-5/antagonists & inhibitors , Low Density Lipoprotein Receptor-Related Protein-5/genetics , Low Density Lipoprotein Receptor-Related Protein-5/metabolism , Low Density Lipoprotein Receptor-Related Protein-6/antagonists & inhibitors , Low Density Lipoprotein Receptor-Related Protein-6/genetics , Low Density Lipoprotein Receptor-Related Protein-6/metabolism , Mice , Models, Molecular , Organoids/cytology , Organoids/metabolism , Protein Binding , Protein Conformation, beta-Strand , Protein Interaction Domains and Motifs , Single-Domain Antibodies/genetics , Single-Domain Antibodies/metabolism , Stem Cells/cytology , Stem Cells/metabolism , Transcription, Genetic , Ubiquitin-Protein Ligases/genetics , Ubiquitin-Protein Ligases/metabolism , Wnt3A Protein/metabolism , beta Catenin/genetics , beta Catenin/metabolismABSTRACT
Microarray analysis of multiple sclerosis (MS) lesions obtained at autopsy revealed increased transcripts of genes encoding inflammatory cytokines, particularly interleukin-6 and -17, interferon-gamma and associated downstream pathways. Comparison of two poles of MS pathology--acute lesions with inflammation versus 'silent' lesions without inflammation--revealed differentially transcribed genes. Some products of these genes were chosen as targets for therapy of experimental autoimmune encephalomyelitis (EAE) in mice. Granulocyte colony-stimulating factor is upregulated in acute, but not in chronic, MS lesions, and the effect on ameliorating EAE is more pronounced in the acute phase, in contrast to knocking out the immunoglobulin Fc receptor common gamma chain where the effect is greatest on chronic disease. These results in EAE corroborate the microarray studies on MS lesions. Large-scale analysis of transcripts in MS lesions elucidates new aspects of pathology and opens possibilities for therapy.
