Olfactory receptors (ORs) account for 49% of all G protein-coupled receptors (GPCRs), which are important targets for drug discovery, and hence ORs may also be potential drug Headcover targets.Various ORs are expressed in breast cancer cells; however, most of them are orphan receptors, and thus, their functions are unknown.Herein, we present an experimental strategy using a surface plasmon resonance (SPR) system and a cell-based assay that allowed the identification of orphan OR6M1 as a new anticancer target in the MCF-7 breast cancer cell line.After the construction of stable OR6M1-expressing cells, the SPR-based screening of 108 chemicals for ligand activity was performed against OR6M1-expressing whole cells (primary screening) or membrane fragments (secondary screening).
As a result, anthraquinone Mug (AQ) and rutin were discovered to be new OR6M1 ligands.Based on calcium imaging in OR6M1-expressing Hana3A cells, AQ and rutin were classified as an OR6M1 agonist and antagonist, respectively.Cell viability and live/dead assays showed that AQ induced the death of MCF-7 cells, which was inhibited by rutin.Therefore, OR6M1 may be considered an anticancer target, and AQ may be considered a chemotherapeutic agent.
This combined method can be widely used to discover the ligands and functions of other orphan GPCRs.