Covalent inhibitor of the Rho family inhibits the migration of breast cancer cells

Small GTPase proteins usually serve as molecular switches in various biological process, such as the proliferation, survival, and migration of cells. Mutations or aberrant activations of small GTPase proteins, such as Ras, are frequently observed in various kinds of cancers. Drug discovery efforts that target the Ras family proteins are making breakthroughs, while the discovery of efficient inhibitors that target the Rho family proteins is still stagnant. Protein members from the Rho family, such as RhoA and Cdc42, are key regulators of the migration and invasion of cancer cells. Thus inhibitors of the Rho family proteins are promising to become drug candidates that target cancer metastasis, which is a principal cause of cancer recurrence and chemotherapy failure. Here we show the discovery and characterization of a novel covalent inhibitor named DC-RC-063 that targets the Rho family proteins, using a combined approach of computations and experiments. Revealed by solved crystal structures, compound DC-RC-063 inhibited the activation of RhoA, by disrupting protein-protein interactions, in an allosteric manner. As compound DC-RC-063 inhibited the migration and invasion of breast cancer MDA-MB-231 cells, our findings proved that the Rho family proteins are targetable for covalent inhibitors via an allosteric mechanism. The novel binding site revealed by this inhibitor can be exploited for further development of anti-cancer drugs that target cancer metastasis. Overall design: RNA-Seq in breast cancer MDA-MB-231 cells in the presence or absence of Rho family covalent inhibitor