A covalently binding OregonFluor-based probe for live-cell imaging of KRAS G12C mutant proteins

Mutations in KRAS, especially at codon 12, are common oncogenic drivers in many cancers. The KRAS G12C variant, a critical target in lung adenocarcinoma and colorectal cancer, currently lacks effective molecular tools for direct visualization in living cells and tissues. To address this gap, we developed a novel covalent OregonFluor-based fluorescent probe that selectively detects KRAS G12C in real time. This probe specifically reacts with the mutant cysteine, forming an irreversible bond, and demonstrates high selectivity over wild-type KRAS and other RAS family proteins. Its excellent brightness and photostability enable dynamic imaging with standard fluorescence microscopy without requiring cell fixation or genetic manipulation. This tool facilitates direct observation of protein localization, trafficking, and drug response, providing insights into RAS-driven oncogenesis and therapeutic resistance. Moreover, it holds promise for fluorescence-guided surgery to precisely delineate tumor margins and improve surgical outcomes. We are expanding this platform to target other KRAS mutants, aiming to accelerate translational research and precision oncology applications.