Discovery Of Rki-18, A Small Molecule That Inhibits Rho Kinases 1 And 2, Migration And Invasion Of Human Tumors

Signal transduction pathways that are mediated by ROCK1 and ROCK2 trigger cell migration, invasion and metastasis. This prompted us to design and synthesize novel Rho-kinase inhibitors (RKIs). Here, we show that one of our most potent RKIs, RKI-18 (IC50 397 nM (ROCK1) and 349 nM (ROCK2)) but not its inactive closely related analogue RKI-11 suppresses potently the phosphorylation of the ROCK substrate MLC2 in intact human cancer cells. Furthermore, RKI-18 is highly selective at inhibiting P-MLC2 over P-Akt, P-S6 and P-Erk ½ levels. RKI-18 suppresses ROCK-mediated actin fiber formation following stimulation with LPA as well as PAK-mediated lamelipodia and filopodia formation following bradykinin or PDGF stimulation. Furthermore, RKI-18 but not RKI-11 inhibits migration, invasion and anchorage-independent growth of human breast cancer cells. The fact that RKI-18, the active ROCK inhibitor, but not RKI-11, its inactive analogue, is effective at suppressing malignant transformation suggests that preventing migration, invasion and anchorage-independent growth with RKI-18 is likely due to inhibition of ROCK. Further advanced preclinical studies are required to determine the potential of RKI-18 as an anti-metastatic agent. Citation Format: Ronil A. Patel, Yan Lui, Binglin Wang, Ronshi Li, Said M. Sebti. Discovery of RKI-18, a small molecule that inhibits Rho kinases 1 and 2, migration and invasion of human tumors. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5556. doi:10.1158/1538-7445.AM2013-5556