Identification of a new inhibitor of Ran GTPase with therapeutic value in epithelial ovarian cancer

Accumulated studies suggest that the small GTPase Ran is critical in cancer initiation and progression. Compounds that block Ran activity would be valuable for cancer treatment. Here, by learning lessons from the discovery of KRAS G12C inhibitors, we generated a structural model of the switch II pocket of GDP-bound Ran to identify potential inhibitors of Ran by virtual screening. After in vitro verification and hit optimization, we identified chemical compound M36 as an efficient inhibitor of Ran with a therapeutic value. Binding of M36 to Ran was confirmed by cellular thermal shift assay. The specificity of M36 towards Ran was demonstrated by the evaluation of the active GTP-bound forms of a range of GTPases including Ran, RhoA, Cdc42 and Rac1; and by the expression of a dominant active mutant of Ran. Remarkably, similar to depletion of Ran by siRNA, M36 exhibits a specific toxicity in aneuploid ovarian cancer cells and represses DNA repair systems. In accordance with this, we established a synergistic relationship between M36 and the FDA approved PARP inhibitor olaparib. In vivo, M36 presents acceptable pharmacokinetic properties and, more importantly, inhibits the tumor growth of an aggressive ovarian xenograft model. Clinically relevant, M36 was able to induce cell death in ex vivo EOC patient derived micro-dissected tumors. Overall, our study is the first to provide a small-molecule compound inhibitor of Ran with a therapeutic potential.