The BET bromodomain inhibitor I-BET151 acts downstream of smoothened protein to abrogate the growth of hedgehog protein-driven cancers

Jun Long, Bin Li, Jezabel Rodriguez-Blanco, Chiara Pastori, Claude Henry Volmar, Claes Wahlestedt, Anthony Capobianco, Feng Bai, Xin Hai Pei, Nagi G. Ayad, David J. Robbins

Research output: Contribution to journalArticle

57 Scopus citations


Epigenetic enzymes modulate signal transduction pathways in different biological contexts. We reasoned that epigenetic regulators might modulate the Hedgehog (HH) signaling pathway, a main driver of cell proliferation in various cancers including medulloblastoma. To test this hypothesis, we performed an unbiased small-molecule screen utilizing an HH-dependent reporter cell line (Light2 cells). We incubated Light2 cells with small molecules targeting different epigenetic modulators and identified four histone deacetylase inhibitors and a bromodomain and extra terminal domain (BET) protein inhibitor (I-BET151) that attenuate HH activity. I-BET151 was also able to inhibit the expression of HH target genes in Sufu-/- mouse embryonic fibroblasts, in which constitutive Gli activity is activated in a Smoothened (Smo)-independent fashion, consistent with it acting downstream of Smo. Knockdown of Brd4 (which encodes one of the BET proteins) phenocopies I-BET151 treatment, suggesting that Brd4 is a regulator of the HH signaling pathway. Consistent with this suggestion, Brd4 associates with the proximal promoter region of the Gli1 locus, and does so in a manner that can be reversed by I-BET151. Importantly, I-BET151 also suppressed theHHactivity-dependent growth of medulloblastoma cells, in vitro and in vivo. These studies suggest that BET protein modulation may be an attractive therapeutic strategy for attenuating the growth of HH-dependent cancers, such as medulloblastoma.

Original languageEnglish (US)
Article numberA32
Pages (from-to)35494-35502
Number of pages9
JournalJournal of Biological Chemistry
Issue number51
StatePublished - Dec 19 2014


ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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