Synthesis of targeted probes for chemical proteomics studies of the EGFR signaling network

The epidermal growth factor receptor (EGFR) kinase is a prototypical receptor kinase with critical function in normal homeostasis and disease progression. Eight EGFR inhibitors spanning three generations are FDA-approved for a few types of cancers and ultimately limited by resistance. Drug resistance has recently been associated to EGFR roles beyond its kinase activity and dependent on subcellular localization. Elucidating endogenous EGFR signaling characteristics may lead to more efficacious therapies. In this thesis work we report the design and synthesis of EGFR-directed probes for taking a chemical proteomics approach to finding potential protein partners of EGFR in the cell. The probes were based on selective EGFR inhibitors and designed to covalently label a lysine residue in the solvent-exposed region of EGFR. Several trifunctional linkers for the modification of other drugs were also obtained. In reverse chemical proteomics using human cDNA libraries from various cancer cells, DNA topoisomerase I was identified as a potential target of the EGFR inhibitor Gefitinib, supporting recent hypothesis of EGFR-topoisomerase crosstalk in drug resistance. In forward chemical proteomics studies in MDA-MB-468 cells, several ATP-utilizing enzymes were identified as potential EGFR interactors. These proteins may in the future be further investigated to validate their interactions with EGFR and understand the biological roles of these interactions to assist the development of new combination therapies.