Bicyclic Imidazolium Inhibitors of Gli Transcription Factor Activity

Abstract

Gli transcription factors within the Hedgehog (Hh) signaling pathway direct key events in mammalian development and promote a number of human cancers. Current therapies for Glidriven tumors target Smoothened (SMO), a G protein-coupled receptor-like protein that functions upstream in the Hh pathway. Although these drugs can have remarkable clinical efficacy, mutations in SMO and downstream Hh pathway components frequently lead to chemoresistance. In principle, therapies that act at the level of Gli proteins, through direct or indirect mechanisms, would be more efficacious. We therefore conducted a screen of 325,120 compounds for their ability to block the constitutive Gli activity induced by loss of Suppressor of Fused (SUFU), a scaffolding protein that directly inhibits Gli function. Our studies reveal a family of bicyclic imidazolium derivatives that can inhibit Gli-dependent transcription without affecting the ciliary trafficking or proteolytic processing of these transcription factors. We anticipate that these chemical antagonists will be valuable tools for investigating the mechanisms of Gli regulation and developing new strategies for targeting Gli-driven cancers.

Targeted protein degradation reveals BET bromodomains as the cellular target of Hedgehog Pathway Inhibitor-1

“…In contrast to the full Hh pathway inhibition that was obtained for the parent molecule HPI-1, inhibition by the PROTACs plateaued at 10-20% in SHH-LIGHT2 cells (Fig. 1e) and at 30-40% in constitutively activated SUFU-KO-LIGHT cells 35 (Fig. 1f), which could point to a differential mode of action of the HPPs compared to the parent molecule.…”

Concatenating Suzuki Arylation and Buchwald–Hartwig Amination by A Sequentially Pd‐Catalyzed One‐Pot Process—Consecutive Three‐Component Synthesis of C,N‐Diarylated Heterocycles

“…[2] Among numerous C,N-bis(hetero)-arylated heterocycles, di(hetero)arylatedi ndoles andc arbazoles are interesting targets as privileged scaffolds in anticancer research (Figure 1). While 2,3-bisarylmaleimidesb earing N-aryl indole moieties were identified as potent and selectivei nhibitors of protein kinases C( PKC), [3] as imple N-(ortho-anisyl)-3-biphenylindole shows lower micromolari nhibition of the hedgehog signaling pathway, [4] which represents an ovel therapeutic principle in the treatment of certain cancers.I na ddition, N-phenylindolylanilines were found to inhibitt he proliferation of HCT-116h uman colon carcinoma cells at nanomolar concentra-tions. [5] Non-canonicalD NA i-motif selectivel igandsb ased on N-aryl-3-triazolyl carbazole have just recently been shown to modulate the transcription of cellularo ncogenes.…”

Small Molecule Intervention in a Protein Kinase C–Gli Transcription Factor Axis

“…27 To examine the potential for PKC modulators to influence Smo-independent Gli-driven luciferase activity, we evaluated our five most potent inhibitors in Sufu-KO-LIGHT cells. 53,54 Sufu-KO-LIGHT cells lack the Hh pathway component Sufu, a direct negative regulator of the Gli transcription factors, and thus exhibit constitutive Gli activity arising downstream of Smo.…”

“…27 To examine the potential for PKC modulators to influence Smo-independent Gli-driven luciferase activity, we evaluated our five most potent inhibitors in Sufu-KO-LIGHT cells. 53,54 Sufu-KO-LIGHT cells lack the Hh pathway component Sufu, a direct negative regulator of the Gli transcription factors, and thus exhibit constitutive Gli activity arising downstream of Smo. As in Shh-LIGHT2 cells, Sufu-KO-LIGHT cells express a stably integrated Gli-driven firefly luciferase reporter; in this assay, Gli-driven luciferase signal is normalized to cell viability.…”

“…While clinical inhibitors have been successful at treating Gli-driven cancers initiated at or upstream of Smo, an increasing number of human cancers are recognized as originating from Smo-independent Gli activity. , An elegant report by Toftgård and co-workers has demonstrated that the effector 3 can block Gli activity initiated downstream of Smo in MEFs . To examine the potential for PKC modulators to influence Smo-independent Gli-driven luciferase activity, we evaluated our five most potent inhibitors in Sufu-KO-LIGHT cells. , Sufu-KO-LIGHT cells lack the Hh pathway component Sufu, a direct negative regulator of the Gli transcription factors, and thus exhibit constitutive Gli activity arising downstream of Smo. As in Shh-LIGHT2 cells, Sufu-KO-LIGHT cells express a stably integrated Gli-driven firefly luciferase reporter; in this assay, Gli-driven luciferase signal is normalized to cell viability.…”