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Next-Generation Hedgehog/GLI Pathway Inhibitors for Cancer Therapy

Department of Biosciences, Paris-Lodron University of Salzburg, Cancer Cluster Salzburg, Hellbrunner Strasse 34, 5020 Salzburg, Austria
Author to whom correspondence should be addressed.
Cancers 2019, 11(4), 538;
Received: 19 March 2019 / Revised: 4 April 2019 / Accepted: 9 April 2019 / Published: 15 April 2019
(This article belongs to the Special Issue Advances in Cancer Stem Cell Research)
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The Hedgehog/Glioma-associated oncogene homolog (HH/GLI) signaling pathway regulates self-renewal of rare and highly malignant cancer stem cells (CSC), which have been shown to account for the initiation and maintenance of tumor growth as well as for drug resistance, metastatic spread and relapse. Efficacious therapeutic approaches targeting CSC pathways, such as HH/GLI signaling in combination with chemo, radiation or immunotherapy are, therefore, of high medical need. Pharmacological inhibition of HH/GLI pathway activity represents a promising approach to eliminate malignant CSC. Clinically approved HH/GLI pathway inhibitors target the essential pathway effector Smoothened (SMO) with striking therapeutic efficacy in skin and brain cancer patients. However, multiple genetic and molecular mechanisms resulting in de novo and acquired resistance to SMO inhibitors pose major limitations to anti-HH/GLI therapies and, thus, the eradication of CSC. In this review, we summarize reasons for clinical failure of SMO inhibitors, including mechanisms caused by genetic alterations in HH pathway effectors or triggered by additional oncogenic signals activating GLI transcription factors in a noncanonical manner. We then discuss emerging novel and rationale-based approaches to overcome SMO-inhibitor resistance, focusing on pharmacological perturbations of enzymatic modifiers of GLI activity and on compounds either directly targeting oncogenic GLI factors or interfering with synergistic crosstalk signals known to boost the oncogenicity of HH/GLI signaling. View Full-Text
Keywords: Hedgehog signaling; Smoothened inhibitors; drug resistance; GLI transcription factors; cancer stem cells Hedgehog signaling; Smoothened inhibitors; drug resistance; GLI transcription factors; cancer stem cells

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Peer, E.; Tesanovic, S.; Aberger, F. Next-Generation Hedgehog/GLI Pathway Inhibitors for Cancer Therapy. Cancers 2019, 11, 538.

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