Title: Mechanistic Pharmacology and Drug Discovery of Hedgehog signaling,Primary Cilium, and Beyond

Speaker: Dr. WANG Yu, University of Wisconsin Madison

Time: 2012-10-17, 10am

Place: IOZ C101

Abstract:

The Hedgehog (Hh) signaling pathway has emerged as a therapeutic target of opportunity given the pathway’s contribution to a variety of diseases, notably several neurodegenerative diseases and a spectrum of cancers. Early drug leads identified Smoothened (Smo), a membrane protein essential for signaling, as an attractive target for drug development. Accumulation of Smo in the primary cilium is a critical regulatory event in vertebrate Hh signaling. Using a novel post-translational labeling technique, we demonstrated that cilial Smo mainly originates from an intracellular source. Surprisingly, cyclopamine, a widely used Hh antagonist, induces a cilial accumulation of Smo similar to that induced by Hh ligand and several Hh agonists. In contrast, other antagonists abrogate Smo cilial accumulation. Cyclopamine’s action of promoting Smo accumulation in the primary cilium correlates with prolonged hypersensitivity to pathway stimulation after drug removal, raising potential concerns in using antagonists that harbor this property in cancer therapy. Therefore, the potential for unfavorable actions of some of the existing clinical candidates argues for the need for understanding pharmacological regulation of Smo translocation to the primary cilium, and further, a focused effort to selectively identify antagonists of Smo cilial accumulation. To this end, we developed a novel high-content screen methodology based on directly observing Smo translocation to the primary cilium.

Using the system, we selectively screened pathway antagonists that block Smo cilial translocation. As we had hoped, novel hits identified in this screen can effectively block Hh response without inducing rebound hyperactivity. While this approach provides an effective new strategy for Hh targeted cancer drug development, a counterpart screen to identify drugs promoting cilial accumulation of Smo revealed potentially dangerous cross-talking of some drugs in clinic with Hh signaling. Most strikingly, we discovered that a large number of anti-inflammatory drugs stimulate Smo translocation to the primary cilium. The use of anti-inflammation treatment in conjunction with cancer therapy is common given that tumor is often surrounded by an inflammatory environment. Our findings of this unforeseen cross-talking raise concerns about ramifications of anti-inflammation drugs and potential drug-drug interactions in Hh-targeted cancer therapy.

Selected publications:

1. Wang Y*, McMahon AP, Allen BL*. (2007) Shifting paradigms in Hedgehog signaling. Current Opinion in Cell Biology. 19(2):159-65 Review. *equal contribution.

2. Zhou Z, Koglin A, Wang Y, McMahon AP, Walsh CT. (2008) An eight residue fragment of anacyl carrier protein suffices for post-translational introduction of fluorescent pantetheinyl arms inprotein modification in vitro and in vivo. Journal of the American Chemical Society.130(30):9925-30.

3. Wang Y, Zhou Z , Walsh CT, McMahon AP. (2009) Selective translocation of intracellular Smoothened to the primary cilium in response to Hedgehog pathway modulation. PNAS. 106(8):2623-8.

4. Wang Y, Arvanites AC, Davidow L, Blanchard J, Lam K, Yoo J, Coy S, Rubin LL, McMahon AP. (2012) Selective identification of Hedgehog pathway antagonists by direct analysis of Smoothened ciliary translocation. ACS Chemical Biology. 7(6):1040-8.

5. Wang Y, Davidow L, Arvanites A, Blanchard J, Lam K, Xu K, Oza V, Yoo J, Ng JM, Curran T, Rubin LL, McMahon AP. (2012) Glucocorticoid Compounds Modify Smoothened Localization and Hedgehog Pathway Activity. Chemistry and Biology. 19:972-982.