Dataset Information

Therapeutic targeting of BRD4 in head neck squamous cell carcinoma

ABSTRACT: The bromodomain and extraterminal family members are epigenetic readers and transcriptional coactivators which are critically involved in various biological processes including tumorigenesis. BRD4 has been increasingly appreciated as a key oncogene and promising anticancer target. Here, we sought to characterize the expression of BRD4 and its tumorigenic roles as well as therapeutic targeting in HNSCC. Expression of BRD4 mRNA and protein was determined by bioinformatics interrogation of public available databases, primary HNSCC samples and 4NQO-induced HNSCC animal model. The tumorigenic roles of BRD4 in HNSCC were evaluated by genetic and pharmacological approach in vitro and in vivo. Therapeutic efficiency of BRD4 targeting by JQ1 was assessed in three preclinical models including xenograft model, 4NQO-induced model and patients-derived xenograft model. Gene candidates responsible for therapeutic effects of JQ1 were identified by transcriptional profiling in HNSCC cells after JQ1 exposure. Significant upregulation of BRD4 was found in primary HNSCC samples and 4NQO-induced HNSCC model. Its overexpression associated with aggressive clinicopathological features and inferior overall and disease-free survival. BRD4 depletion by genetic silencing or pharmacological inhibition impaired cell proliferation, migration and invasion and reduced tumor growth and metastasis in vivo. Transcriptional profiling of HNSCC cells following JQ1 exposure identified hundreds of genes which might mediated its antitumor effects and enriched in cancer-relevant pathways. A novel prognostic risk score derived from JQ1-regualted genes was developed to stratify patients into subgroups with favorable or inferior prognosis. Our findings reveal that BRD4 serves as a novel oncogene driving cancer progression and a robust prognostic biomarker in HNSCC. Therapeutic targeting of BRD4 represents a potent and promising strategy against HNSCC.

ORGANISM(S): Homo sapiens

PROVIDER: GSE122522 | GEO | 2019/05/09

REPOSITORIES: GEO

ACCESS DATA

Dataset's files

Source:

			Action	DRS
		Other

Items per page:

1 - 1 of 1

Similar Datasets

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.

Project description:Targeting the epigenome to modulate gene expression programs driving cancer development has emerged as an exciting avenue for therapeutic intervention. Pharmacological inhibition of the bromodomain and extraterminal (BET) family of chromatin adapter proteins has proven effective in this regard, suppressing growth of diverse cancer types mainly through downregulation of the c-MYC oncogene and its downstream transcriptional program. While initially effective, resistance to BET inhibitors (BETi) typically occurs through mechanisms that reactivate MYC expression. We have previously shown that lung adenocarcinoma (LAC) is inhibited by JQ1 through suppression of FOSL1, suggesting that the epigenetic landscape of tumor cells from different origins and differentiation states influences BETi response. Here, we assessed how these differences affect mechanisms of BETi resistance through the establishment of isogenic pairs of JQ1 sensitive and resistant LAC cell lines. We found that resistance to JQ1 in LAC occurs independent of FOSL1 while MYC levels remain unchanged between resistant cells and their JQ1 treated parental counterparts. Furthermore, while epithelial-mesenchymal transition (EMT) is observed upon resistance, TGF- induced EMT did not confer resistance in JQ1 sensitive LAC lines, suggesting this is a consequence, rather than a driver of BETi resistance in our model systems. Importantly, siRNA knockdown demonstrated that JQ1 resistant cell lines are still dependent on BRD4 expression and we found that phosphorylation of BRD4 is elevated in resistant LACs, identifying casein kinase 2 (CK2) as a candidate protein mediating this effect. Inhibition of CK2, as well as downstream transcriptional targets of phosphorylated BRD4 - including AXL and activators of the PI3K pathway - synergize with JQ1 to inhibit BETi resistant LAC. Overall, this demonstrates that the mechanism of resistance to BETi varies depending on cancer type, with LAC cells developing JQ1 resistance independent of MYC re-activation, and identifying CK2 phosphorylation of BRD4 as a potential target to overcome resistance in this cancer.

Project description:The pathognomonic EWS/ETS fusion transcription factors drive Ewing sarcoma (EWS) by orchestrating an oncogenic transcription program. Therapeutic targeting of EWS/ETS has not been successful; therefore identifying mediators of the EWS/ETS function could offer new therapeutic targets. Here we describe the dependency of chromatin reader BET bromodomain proteins in EWS/ETS driven transcription and investigate the potential of BET inhibitors in treating this lethal cancer. Similar to EWS/ETS fusions, knockdown of BET proteins BRD2/3/4 severely impaired the oncogenic phenotype of EWS cells. Notably, EWS/FLI1 and EWS/ERG was found to be in a transcriptional complex consisting of BRD4. RNA-Seq analysis upon BRD4 knockdown or its pharmacologic inhibition by the BET inhibitor JQ1 revealed an attenuated EWS/ETS transcriptional signature. In contrast to other reports, JQ1 reduced proliferation, and induced apoptosis through MYC-independent mechanism without affecting EWS/ETS protein levels, which was further confirmed by depleting BET proteins using PROTAC-BET degrader (BETd). Interestingly, polycomb repressive complex 2 (PRC2) associated factor PHF19 was downregulated by JQ1/BETd or BRD4 knockdown in multiple EWS cells. ChIP-seq analysis revealed occupancy of EWS/FLI1 at a distal regulatory element of PHF19 and its subsequent knockdown resulted in downregulation of PHF19 expression. Furthermore, deletion of PHF19 by CRISPR-Cas9 system lead to a decreased tumorigenic phenotype and increased sensitivity to JQ1. Importantly, PHF19 expression was associated with worse prognosis of Ewing sarcoma patients. In vivo, JQ1 demonstrated anti-tumor efficacy in multiple mouse xenograft models of EWS. Together, these results indicate that EWS/ETS require BET epigenetic reader proteins for its transcriptional program including PHF19 expression, which can be mitigated by BET inhibitors. Moreover, this study provides a clear rationale for the clinical utility of BET inhibitors in treating Ewing sarcoma.

Dataset Information

Therapeutic targeting of BRD4 in head neck squamous cell carcinoma

Dataset's files

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets