Small Molecule Therapeutics Identification, Mechanism of Action, and Antitumor Activity of a Small Molecule Inhibitor of Hippo, TGF-b, and Wnt Signaling Pathways

Embryonic signaling pathways, in particular thosemediated byWnt andTGF-b, are known to play key roles in tumor progression through the induction of epithelial–mesenchymal transition (EMT). Their simultaneous targeting could therefore represent a desirable anticancer strategy.On the basis of recent findings that bothWnt and TGF-b–associated pathways are regulated by Hippo signaling in mammalian cells, we reasoned that targeting the latter would be more effective in inhibiting EMT. In a search for such inhibitors, we identified a small molecule (C19) with remarkable inhibitory activity not only against Hippo, but also against Wnt and TGF-b pathways. C19 inhibited cancer cell migration, proliferation, and resistance to doxorubicin in vitro, and exerted strong antitumor activity in a mouse tumor model. Mechanistically, C19 induced GSK3-b–mediated degradation of the Hippo transducer TAZ, through activation of the Hippo kinases Mst/Lats and the tumor suppressor kinase AMPK upstream of the degradation complex. Overall, this study identified C19 as a multiEMT pathway inhibitor with a unique mechanism of action. The findings that both AMPK and Mst/Lats mediate the antitumor activity of C19 shed light on a potential cross-talk between metabolic and organ size control pathways in regulating cancer progression. By simultaneously targeting these two pathways, C19may represent a new type of agents to suppress cancer progression and/or its recurrence. Mol Cancer Ther; 13(6); 1457–67. 2014 AACR.