Aberrant Notch signalling has been implicated in a variety of tumor types, where it is known to play a role in tumorigenisis and angiogenisis. In particular, recent evidence suggests that the Notch pathway is activated by somatic mutations in a significant proportion of human T cell acute lymphoblastic leukaemias (T-ALLs). Therefore targeting of the Notch pathway represents an attractive avenue for anti-cancer drug discovery. However, apart from the potential use of gamma-secratase inhibitors, there are very few known tractable intervention points along this predominantly protein-protein interaction mediated pathway. The structural characteristics of protein-protein contact surfaces present a huge challenge for small molecule drug discovery as these contact surfaces are generally larger than those involved in protein-small molecule interactions and often lack the grooves and pockets on the protein surface that small molecules efficiently bind to. Recent discoveries in our laboratories indicate that the interaction of the HES transcription factor with the TLE co-repressor could provide a tractable point for small molecule inhibitors that would inhibit the Notch signalling pathway. The interaction between HES/TLE is dependent on a highly conserved contiguous tetra-peptide WRPW motif present in the C-terminus of HES family members which binds to the WD domain of TLE. The binding site on TLE is a potentially druggable hydrophobic recess located at the central pore of a 7-bladed β-propeller structure, and the WRPW motif sits on top of the recess contacting all 7 blades of the -propeller. We have established and validated biochemical fluorescence polarisation (FP) and GST-WRPW pull down assays to identify compounds that disrupt HES/TLE binding in vitro and a GAL4-WRPW reporter luciferase assay was developed as an effective way of monitoring the WRPW dependent interactions between HES and TLE proteins in a cell culture model. Using these assays a small library of peptide derivatives, based around the highly conserved WRPW motif, was screened. SAR from the peptide array in conjunction with structural information from a WRPW peptide bound to TLE1 WD domain was used to construct a 3D pharmacophore model which was applied as a search query for in silico virtual screening.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr C126.