Abstract 617: Inhibitors of Beta-Catenin Signaling Limit Growth of Vascular Smooth Muscle Cells

Abstract

Smooth muscle cell (SMC) growth is essential for artery formation during development and significantly contributes to neointima formation after vascular injury in adulthood. We recently showed, using a tissue-specific deletion and knock-in of mutant alleles, that beta-catenin (b-ctn) signaling function is essential for SMC growth and artery formation; moreover, protein interactions mediated by its C-terminus domain are required for assembly of the arterial wall, while b-ctn N-terminus interactions are dispensable. Inhibitors of b-ctn have been developed, but their effects on vascular SMC growth have not been fully tested. We hypothesize that inhibitors that disrupt protein interactions mediated by the b-ctn C-terminus domain will impair b-ctn signaling and limit growth of vascular SMCs. We evaluated growth of mouse aortic SMCs and human coronary artery SMCs in culture using AlamarBlue after exposure to increasing concentrations (0.01 to 10 micromolar) of several validated b-ctn inhibitors or vehicle control: PKF118-310 (disrupts the b-ctn/TCF interaction), ICG001 (disrupts the b-ctn C-terminus/CBP interaction), XAV939 (promotes the b-ctn destruction complex), and carnosic acid (disrupts the b-ctn N-terminus/BCL9 interaction). We also evaluated the effect of these inhibitors on b-ctn transcriptional activity in SMCs using a TOPflash reporter system. We found that PKF118-310 (p<0.05 vs. vehicle), ICG001 (p<0.05 vs. vehicle), and XAV939 (p<0.05 vs. vehicle), but not carnosic acid, limit mouse (n=16 independent cultures) and human (n=8 independent cultures) SMC growth in a dose-response manner. PKF118-310 exhibited the most potent inhibitory effect. We also found that PKF118-310, ICG001, and XAV939, but not carnosic acid, inhibit b-ctn transcriptional activity in arterial SMCs in culture. In conclusion, pharmacological inhibition of b-ctn signaling, particularly blocking the b-ctn C-terminus output, inhibits growth of vascular SMCs in culture, providing a rationale to test these inhibitors in models of vascular injury as they hold promise as novel therapies for cardiovascular disease.