University of Kansas Medical Center
Rational design of SPRY2-Cbl inhibitors as potential anticancer drugs (2014-15)
This proposal seeks to discover and develop compounds to restore function of SPRY2, a protein that normally suppresses cancers and is inactivated in many common cancer types. Successful completion of this project is an essential first step toward development of a new class of therapies with potential application for treatment of a great many human cancers.
Signaling via receptor tyrosine kinases (RTK) through the mitogen activated kinase ERK drives up to 85% of human cancers. SPRY2, an endogenous feedback inhibitor of RTK-ERK signaling, is a tumor suppressor sequestered by a protein partner, Cbl. Truncation and site-mutagenesis studies map SPRY2-Cbl interactions to two discrete domains, RING and TKB. SPRY2 suppressor function is inactivated epigenetically, rather than by deletion or mutation. So SPRY2 is present at reduced levels in most cancer cells. Our preliminary data show that disrupting SPRY2-Cbl complexes with a peptide targeting the RING interaction inhibits cell proliferation and induces apoptosis.
These observations suggest a testable, novel therapeutic hypothesis: SPRY2 suppressor activity can be restored by inhibiting its interaction with Cbl. Two specific aims are proposed as initial tests of this hypothesis: First, to discover and rationally design small molecules that disrupt SPRY2-Cbl interaction; and second, to confirm that optimized hits from aim 1 disrupt endogenous SPRY2-Cbl complexes, inhibit RTK-ERK signaling and cancer cell proliferation, and induce apoptosis. In aim 1, SPRY2-Cbl TKB and RING interactions will be defined by x-ray crystallography, bio-molecular NMR, and computational modeling. Screening of a commercial (Zenobia) fragment library by Surface Plasmon Resonance spectroscopy (SPR) and of a ~5200 compound library (from the KU Center of Excellence in Chemical Methodologies and Library Development) by Fluorescence Polarization will proceed in parallel. Binding affinity and kinetics of hits will be quantified by SPR; when feasible, structural interactions of hits with Cbl will be defined by x-ray crystallography and/or NMR. These data will inform iterative optimization of fragments and compounds in collaboration with medicinal chemistry. In aim 2, the ability of optimized hits to disrupt SPRY2-Cbl complexes, inhibit RTK-ERK signaling, inhibit proliferation, and induce apoptosis will be confirmed in human carcinoma cell lines. This project engages collaborators and core facilities across two NIH Centers of Biomedical Research Excellence (COBREs) and a NCI-designated Cancer Center at the University of Kansas, to develop novel therapeutics with potential to treat a wide variety of human cancers.