Chem-CRISPR/dCas9FCPF - a platform for chemically induced epigenome editing
Ontology highlight
ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE234491 | GEO | 2023/06/09
REPOSITORIES: GEO
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Project description:Epigenetic aberration is one of the major driving factors in the initiation, promotion, and progression of human cancer and it is also often associated with acquired therapeutic resistance. Several chemical epigenetic modulators have been reported. However, results from animal models and clinical trials have indicated that severe on- and off-target toxicity is one of the leading factors behind failures in epidrug development. CRISPR/dCas9 technology provides a powerful tool for precise epigenetic regulation at the single-gene level. This approach requires ectopic expression of exogenous epigenetic modulatory proteins, which cause side effects and technical challenges for preparation and delivery. Recently, we have shown that Cas9 tagging with the peptide motif (FCPF) was recognized by perfluoro biphenyl derivatives. Here, we introduced the FCPF-tag into dCas9 and report a chemically induced platform for epigenome editing (Chem-CRISPR/dCas9FCPF). By conjugating JQ1, a BRD4 inhibitor, to perfluoro biphenyl (JQ1-FCPF), we demonstrate that JQ1-FCPF covalently binds to CRISPR/dCas9 and specifically inhibits BRD4 in proximity to the promoters/enhancers of c-MYC with the guidance of c-MYC sgRNAs. Thus, we achieved epigenetic modulation of c-MYC with high efficiency and specificity.
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Project description:Triple negative breast cancer (TNBC) is a heterogeneous and clinically aggressive disease for which there is no targeted therapy. Here we report the preferential and high sensitivity of TNBCs to BET bromodomain inhibitors such as JQ1 manifested by cell cycle arrest in early G1, apoptosis, and induction of markers of luminal epithelial differentiation in vitro and in vivo. The sensitivity of TNBC and other tumor types to BET inhibition establishes a rationale for clinical investigation, and a motivation to understand mechanisms of resistance. After engendering acquired resistance to BET inhibition in previously sensitive TNBCs, we utilized integrative approaches to identify a unique mechanism of epigenomic resistance to this epigenetic therapy. Resistant cells remain dependent on BRD4, confirmed by RNA interference. However, TNBC cells adapt to BET bromodomain inhibition by re-recruitment of unmutated BRD4 to super-enhancers, now in a bromodomain-independent manner. Proteomic studies of resistant TNBC identify hyper-phosphorylation of BRD4 and strong association with MED1. Together, these studies provide a rationale for BET inhibition in TNBC and argue for combination strategies to anticipate clinical drug resistance. Chem-Seq in parental and JQ1 resistant triple negative breast cancer (TNBC)
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Project description:Chem-CRISPR/dCas9 -a chemically induced platform for epigenome editing
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Project description:Epigenetic pathways regulate gene expression by controlling and interpreting chromatin modifications. Cancer cells are characterized by altered epigenetic landscapes and commonly exploit the chromatin regulatory machinery to enforce oncogenic gene expression programs. While chromatin alterations are, in principle, reversible and often amendable to drug intervention, the promise of targeting such pathways therapeutically has been hampered by our limited understanding of cancer-specific epigenetic dependencies. Here we describe a non-biased approach to probe epigenetic vulnerabilities in acute myeloid leukemia (AML) – an aggressive hematopoietic malignancy often associated with aberrant chromatin states. By screening a custom shRNA library targeting known chromatin regulators in a genetically defined AML mouse model, we identify the bromodomain-containing protein Brd4 as a critical requirement for disease maintenance. Suppression of Brd4 using shRNAs or the small-molecule inhibitor JQ1 led to robust anti-leukemic effects in vitro and in vivo, accompanied by terminal myeloid differentiation. Extensive evaluation of JQ1-sensitivity in primary human leukemia samples and in established cell lines revealed a broad activity of this compound against diverse AML subtypes. These effects are, at least in part, due to a requirement for Brd4 in maintaining Myc expression and promoting aberrant self-renewal. Together, our results indicate that Brd4 is a promising therapeutic target in AML and identify a small molecule that efficiently targets Myc. These findings also highlight the utility of RNAi screening as a discovery platform for revealing epigenetic vulnerabilities for direct pharmacologic intervention in cancer. In order to understand downstream targets of Brd4, we performed array in murine or human MLL-AF9/NrasG12D cell line under the condition that Brd4 was suppressed by using shRNAs or the small molecule inhibitor JQ1. To test the hypothesis that Myc might be an important target of Brd4, we performed arrary on murine ectopic Myc overexpression MLL-AF9/NrasG12D cell under JQ1 treatment.
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