Nanoscale Mapping of EGFR and c-MET Protein Environments on Lung Cancer Cell Surfaces via Therapeutic Antibody Photocatalyst Conjugates.

Receptor tyrosine kinases are involved in essential signaling roles that impact cell growth, differentiation, and proliferation. The overexpression or mutation of these proteins can lead to aberrant signaling that has been directly linked to a number of diseases including cancer cell formation and progression. This has led to intense clinical focus on modulating RTK activity through direct targeting of signaling activity or cell types harboring aberrant RTK behavior. In particular, epidermal growth factor receptor (EGFR) has attracted intense clinical attention due to the impact of inhibiting this RTK on tumor growth. However, mutations incurred through targeting EGFR have led to therapeutic resistance that involves not only direct mutations to the EGFR protein but also the involvement of other RTKs, such as c-MET, that can overcome therapeutic-based EGFR inhibition effects. This has, not surprisingly, led to co-targeting strategies of RTKs such as EGFR and c-MET to overcome resistance mechanisms. While the ability to co-target these proteins has led to success in the clinic, a more comprehensive understanding of their proximal environments, particularly in the context of therapeutic modalities, could further enhance both our understanding of their signaling biology and provide additional avenues for targeting these surface proteins. Thus, to investigate EGFR and c-MET protein microenvironments, we utilized our recently developed iridium photocatalyst-based microenvironment mapping technology to catalog EGFR and c-MET surface environments on non-small cell lung cancer cell lines. Through this approach, we enriched EGFR and c-MET from the cell surface and identified known EGFR and c-MET associators as well as previously unidentified proximal proteins.