7-Chloro-6-piperidin-1-yl-quinoline-5,8-dione (PT-262), a novel ROCK inhibitor blocks cytoskeleton function and cell migration

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The 5,8-quinolinediones are precursors for producing multiple types of bioactive products. In this study, we investigated a new compound derived from 5,8-quinolinediones, 7-chloro-6-piperidin-1-yl-quinoline-5,8-dione (designated as PT-262), which markedly induced cytoskeleton remodeling and migration inhibition in lung carcinoma cells. Comparison with various cytoskeleton inhibitors, including paclitaxel, colchicine and phallacidin, the cell morphology following treatment with PT-262 was similar to phallacidin on the cell elongation and abnormal actin polymerization. However, PT-262 did not directly bind to actin filaments. ROCK (Rho-associated coiled-coil forming protein kinase) is a downstream effector of RhoA to mediate the phosphorylation of myosin light chain (MLC) and cytoskeleton reorganization. The RhoA–ROCK–MLC pathway has been shown to promote cancer cell migration and metastasis. Interestingly, PT-262 was more effective on inhibiting ROCK kinase activities than specific ROCK inhibitors Y-27632 and H-1152. PT-262 induced cytoskeleton remodeling and migration inhibition in A549 lung carcinoma cells. The total MLC and phosphorylated MLC proteins and stress fibers were blocked after treatment with PT-262. Nonetheless, the RhoA protein and GTPase activity were not altered by PT-262. A computational model suggests that PT-262 interacts with the ATP-binding site of ROCK protein. Together, these findings demonstrate that PT-262 is a new ROCK inhibitor.

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