| Description |
Several forms of cancer including colorectal cancer, hepatocellular carcinoma, leukemia, and some forms of fibroses have been linked to the hyperactivation of the canonical Wnt signaling pathway. The inhibition of the upstream components of the canonical Wnt signaling pathway, including porcupine, Wnt/Fzd-LRP interactions, LRP6 phosphorylation and Dvl, have all shown undesirable cross-regulatory effects on the -catenin-independent Wnt pathways. The inhibition of the downstream component of the canonical Wnt signaling pathway, such as β-catenin transcriptional activation complex, represents a more promising strategy. There are two key protein-protein interaction interfaces in the β-catenin transcriptional activation complex that are critical for canonical Wnt signaling. One is the interaction between scaffold protein β-catenin and transcriptional factor T-cell factor (Tcf). The second one is the interaction between β-catenin and transcriptional coactivator B-cell lymphoma 9 (BCL9). Tcf shares a common binding site with cadherin, Axin, and adenomatous polysis coli (APC) in the major groove of β-catenin. Conversely, BCL9 binds to a remote hydrophobic pocket containing β-catenin residues L148, A149, A152, L156, L159, L160, M174, and L178. The pocket also contains the charged residues D145, E155, and D164. This site shows promising druggability for small-molecule inhibition. iv Herein, we report our work on the design of small-molecule inhibitors for the disruption of β-catenin/BCL9 interactions. Thirteen compounds were synthesized and assayed by AlphaScreen. The structure-activity relationships (SAR) of these compounds support the proposed mode of binding. The most potent inhibitor, 36, exhibits an inhibition constant (Ki) of 2.09 ± 0.43 μM in the functional protein assays. This compound can also pass the cell membrane and effectively inhibit the transactivation of canonical Wnt signaling, the mRNA and protein expression of Wnt/β-catenin target genes, and the growth of colorectal cancer cells. This study lays the foundation for the further design of small-molecules. |
