AlphaScreen selectivity assay for β-catenin/B-cell lymphoma 9 inhibitors

The aberrant formation of the β-catenin/B-cell lymphoma 9 (BCL9) protein-protein complex is the driving force for many diseases, including cancer. Crystallographic analyses demonstrate that the surface area in β-catenin for interacting with BCL9 is overlapped with that for the β-catenin/E-cadherin interaction. In this study, a robust AlphaScreen selectivity assay was developed to quantify inhibitor potency for the β-catenin/BCL9 interaction and selectivity for β-catenin/BCL9 over β-catenin/E-cadherin interactions. A pilot screen was performed to demonstrat the feasibility of this assay. This selectivity assay is highly sensitive and suitable for adaptation to high-throughput screening. The establishment of this assay lays the foundation for the discovery of selective inhibitors specific for β-catenin/BCL9 interactions.