Targeting MYCN in neuroblastoma by BET bromodomain inhibition.
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ABSTRACT:
SUBMITTER: Puissant A
PROVIDER: S-EPMC3672953 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Bromodomain inhibition comprises a promising therapeutic strategy in cancer, particularly for hematologic malignancies. To date, however, genomic biomarkers to direct clinical translation have been lacking. We conducted a cell-based screen of genetically-defined cancer cell lines using a prototypical inhibitor of BET bromodomains. Integration of genetic features with chemosensitivity data revealed a robust correlation between MYCN amplification and sensitivity to bromodomain inhibition. We characterized the mechanistic and translational significance of this finding in neuroblastoma, a childhood cancer with frequent amplification of MYCN. Genome-wide expression analysis demonstrated downregulation of the MYCN transcriptional program accompanied by suppression of MYCN transcription. Functionally, bromodomain-mediated inhibition of MYCN impaired growth and induced apoptosis in neuroblastoma. BRD4 knock-down phenocopied these effects, establishing BET bromodomains as transcriptional regulators of MYCN. BET inhibition conferred a significant survival advantage in three in vivo neuroblastoma models, providing a compelling rationale for developing BET bromodomain inhibitors in patients with neuroblastoma. Significance: Biomarkers of response to small-molecule inhibitors of BET bromodomains, a new compound class with promising anti-cancer activity, have been lacking. Here, we reveal MYCN amplification as a strong genetic predictor of sensitivity to BET bromodomain inhibitors, demonstrate a mechanistic rationale for this finding, and provide a translational framework for clinical trial development of BET bromodomain inhibitors for pediatric patients with MYCN-amplified neuroblastoma. JQ1 is a novel thieno-triazolo-1,4-diazepine, which displaces BET bromodomains from chromatin by competitively binding to the acetyl lysine recognition pocket. BE(2)-C and Kelly cells were treated in triplicate with 1 µM JQ1 or DMSO for 24 hours. RNA was extracted and a decrease in MYCN transcript was confirmed by real time RT-PCR as described above. The samples were profiled using the Affymetrix PrimeView Human Gene Expression Array (Affymetrix) at Beth Israel Deaconess Medical Center (Boston, MA, USA).
2013-02-25 | E-GEOD-43392 | biostudies-arrayexpress
Project description:Bromodomain inhibition comprises a promising therapeutic strategy in cancer, particularly for hematologic malignancies. To date, however, genomic biomarkers to direct clinical translation have been lacking. We conducted a cell-based screen of genetically-defined cancer cell lines using a prototypical inhibitor of BET bromodomains. Integration of genetic features with chemosensitivity data revealed a robust correlation between MYCN amplification and sensitivity to bromodomain inhibition. We characterized the mechanistic and translational significance of this finding in neuroblastoma, a childhood cancer with frequent amplification of MYCN. Genome-wide expression analysis demonstrated downregulation of the MYCN transcriptional program accompanied by suppression of MYCN transcription. Functionally, bromodomain-mediated inhibition of MYCN impaired growth and induced apoptosis in neuroblastoma. BRD4 knock-down phenocopied these effects, establishing BET bromodomains as transcriptional regulators of MYCN. BET inhibition conferred a significant survival advantage in three in vivo neuroblastoma models, providing a compelling rationale for developing BET bromodomain inhibitors in patients with neuroblastoma. Significance: Biomarkers of response to small-molecule inhibitors of BET bromodomains, a new compound class with promising anti-cancer activity, have been lacking. Here, we reveal MYCN amplification as a strong genetic predictor of sensitivity to BET bromodomain inhibitors, demonstrate a mechanistic rationale for this finding, and provide a translational framework for clinical trial development of BET bromodomain inhibitors for pediatric patients with MYCN-amplified neuroblastoma.
2013-02-25 | GSE43392 | GEO
Project description:Direct targeting of oncogenic MYC proteins has been an elusive goal of many cancer drug development efforts. In this issue of Cancer Discovery, Stegmaier and colleagues demonstrate that pharmacologically interfering with the bromodomain and extraterminal (BET) class of proteins potently depletes MYCN in neuroblastoma cells, resulting in cellular cytotoxicity and thus providing a novel approach with a potential impact on a previously undruggable major oncogene.
| S-EPMC3709873 | biostudies-literature
Project description:Hippo/YAP1 signaling is a major regulator of organ size, cancer stemness, and aggressive phenotype. Thus, targeting YAP1 may provide a novel therapeutic strategy for tumors with high YAP1 expression in esophageal cancer (EC). Chromatin immunoprecipitation (ChiP) and quantitative ChiP-PCR were used to determine the regulation of the chromatin remodeling protein bromodomain-containing protein 4 (BRD4) on YAP1. The role of the bromodomain and extraterminal motif (BET) inhibitor JQ1, an established BRD4 inhibitor, on inhibition of YAP1 in EC cells was dissected using western blot, immunofluorescence, qPCR, and transient transfection. The antitumor activities of BET inhibitor were further examined by variety of functional assays, cell proliferation (MTS), tumorsphere, and ALDH1+ labeling in vitro and in vivo. Here, we show that BRD4 regulates YAP1 expression and transcription. ChiP assays revealed that BRD4 directly occupies YAP1 promoter and that JQ1 robustly blocks BRD4 binding to the YAP1 promoter. Consequently, JQ1 strongly suppresses constitutive or induced YAP1 expression and transcription in EC cells and YAP1/Tead downstream transcriptional activity. Intriguingly, radiation-resistant cells that acquire strong cancer stem cell traits and an aggressive phenotype can be effectively suppressed by JQ1 as assessed by cell proliferation, tumorsphere formation, and reduction in the ALDH1+ cells. Moreover, effects of JQ1 are synergistically amplified by the addition of docetaxel in vitro and in vivo. Our results demonstrate that BRD4 is a critical regulator of Hippo/YAP1 signaling and that BRD4 inhibitor JQ1 represents a new class of inhibitor of Hippo/YAP1 signaling, primarily targeting YAP1 high and therapy-resistant cancer cells enriched with cancer stem cell properties.
| S-EPMC7266288 | biostudies-literature
Project description:Hedgehog signaling drives oncogenesis in several cancers, and strategies targeting this pathway have been developed, most notably through inhibition of Smoothened (SMO). However, resistance to Smoothened inhibitors occurs by genetic changes of Smoothened or other downstream Hedgehog components. Here we overcome these resistance mechanisms by modulating GLI transcription through inhibition of bromo and extra C-terminal (BET) bromodomain proteins. We show that BRD4 and other BET bromodomain proteins regulate GLI transcription downstream of SMO and suppressor of fused (SUFU), and chromatin immunoprecipitation studies reveal that BRD4 directly occupies GLI1 and GLI2 promoters, with a substantial decrease in engagement of these sites after treatment with JQ1, a small-molecule inhibitor targeting BRD4. Globally, genes associated with medulloblastoma-specific GLI1 binding sites are downregulated in response to JQ1 treatment, supporting direct regulation of GLI activity by BRD4. Notably, patient- and GEMM (genetically engineered mouse model)-derived Hedgehog-driven tumors (basal cell carcinoma, medulloblastoma and atypical teratoid rhabdoid tumor) respond to JQ1 even when harboring genetic lesions rendering them resistant to Smoothened antagonists. Altogether, our results reveal BET proteins as critical regulators of Hedgehog pathway transcriptional output and nominate BET bromodomain inhibitors as a strategy for treating Hedgehog-driven tumors with emerged or a priori resistance to Smoothened antagonists.
| S-EPMC4108909 | biostudies-literature
Project description:BET family proteins are epigenetic regulators known to control expression of genes involved in cell growth and oncogenesis. Selective inhibitors of BET proteins exhibit potent anti-proliferative activity in a number of hematologic cancer models, in part through suppression of the MYC oncogene and downstream Myc-driven pathways. However, little is currently known about the activity of BET inhibitors in solid tumor models, and whether down-regulation of MYC family genes contributes to sensitivity. Here we provide evidence for potent BET inhibitor activity in neuroblastoma, a pediatric solid tumor associated with a high frequency of MYCN amplifications. We treated a panel of neuroblastoma cell lines with a novel small molecule inhibitor of BET proteins, GSK1324726A (I-BET726), and observed potent growth inhibition and cytotoxicity in most cell lines irrespective of MYCN copy number or expression level. Gene expression analyses in neuroblastoma cell lines suggest a role of BET inhibition in apoptosis, signaling, and N-Myc-driven pathways, including the direct suppression of BCL2 and MYCN. Reversal of MYCN or BCL2 suppression reduces the potency of I-BET726-induced cytotoxicity in a cell line-specific manner; however, neither factor fully accounts for I-BET726 sensitivity. Oral administration of I-BET726 to mouse xenograft models of human neuroblastoma results in tumor growth inhibition and down-regulation MYCN and BCL2 expression, suggesting a potential role for these genes in tumor growth. Taken together, our data highlight the potential of BET inhibitors as novel therapeutics for neuroblastoma, and suggest that sensitivity is driven by pleiotropic effects on cell growth and apoptotic pathways in a context-specific manner.
| S-EPMC3751846 | biostudies-literature
Project description:The transcription factor signal STAT5 is constitutively activated in a wide range of leukemias and lymphomas, and drives the expression of genes necessary for proliferation, survival, and self-renewal. Thus, targeting STAT5 is an appealing therapeutic strategy for hematologic malignancies. Given the importance of bromodomain-containing proteins in transcriptional regulation, we considered the hypothesis that a pharmacologic bromodomain inhibitor could inhibit STAT5-dependent gene expression. We found that the small-molecule bromodomain and extra-terminal (BET) bromodomain inhibitor JQ1 decreases STAT5-dependent (but not STAT3-dependent) transcription of both heterologous reporter genes and endogenous STAT5 target genes. JQ1 reduces STAT5 function in leukemia and lymphoma cells with constitutive STAT5 activation, or inducibly activated by cytokine stimulation. Among the BET bromodomain subfamily of proteins, it seems that BRD2 is the critical mediator for STAT5 activity. In experimental models of acute T-cell lymphoblastic leukemias, where activated STAT5 contributes to leukemia cell survival, Brd2 knockdown or JQ1 treatment shows strong synergy with tyrosine kinase inhibitors (TKI) in inducing apoptosis in leukemia cells. In contrast, mononuclear cells isolated form umbilical cord blood, which is enriched in normal hematopoietic precursor cells, were unaffected by these combinations. These findings indicate a unique functional association between BRD2 and STAT5, and suggest that combinations of JQ1 and TKIs may be an important rational strategy for treating leukemias and lymphomas driven by constitutive STAT5 activation.
| S-EPMC4013223 | biostudies-literature
Project description:Ewing sarcomas (ES) are highly malignant bone or soft tissue tumors. Genetically, ES are defined by balanced chromosomal EWS/ETS translocations, which give rise to chimeric proteins (EWS-ETS) that generate an oncogenic transcriptional program associated with altered epigenetic marks throughout the genome. By use of an inhibitor (JQ1) blocking BET bromodomain binding proteins (BRDs) we strikingly observed a strong down-regulation of the predominant EWS-ETS protein EWS-FLI1 in a dose dependent manner. This was further enhanced by co-treatment with an inhibitor of the PI3K pathway. Microarray analysis further revealed JQ1 treatment to block a typical ES associated expression program. The effect on this expression program was mimicked by RNA interference with BRD3 or BRD4 expression, indicating that the EWS-FLI1 mediated expression profile is at least in part mediated via such epigenetic readers. Consequently, contact dependent and independent proliferation of different ES lines was strongly inhibited. Mechanistically, treatment of ES resulted in a partial arrest of the cell cycle as well as induction of apoptosis. Tumor development was suppressed dose dependently in a xeno-transplant model in immune deficient mice, overall indicating that ES may be susceptible to treatment with epigenetic inhibitors blocking BET bromodomain activity and the associated pathognomonic EWS-ETS transcriptional program.
| S-EPMC4811472 | biostudies-literature
Project description:There is increasing interest in inhibitors targeting BET (bromodomain and extra-terminal) proteins because of the association between this family of proteins and cancer progression. BET inhibitors were initially shown to have efficacy in hematologic malignancies; however, a number of studies have now shown that BET inhibitors can also block progression of non-hematologic malignancies. In this Review, we summarize the efficacy of BET inhibitors in select solid tumors; evaluate the role of BET proteins in mediating resistance to current targeted therapies; and consider potential toxicities of BET inhibitors. We also evaluate recently characterized mechanisms of resistance to BET inhibitors; summarize ongoing clinical trials with these inhibitors; and discuss potential future roles of BET inhibitors in patients with solid tumors.
| S-EPMC5288238 | biostudies-literature
Project description:Cancer cells are often hypersensitive to the targeting of transcriptional regulators, which may reflect the deregulated gene expression programs that underlie malignant transformation. One of the most prominent transcriptional vulnerabilities in human cancer to emerge in recent years is the bromodomain and extraterminal (BET) family of proteins, which are coactivators that link acetylated transcription factors and histones to the activation of RNA polymerase II. Despite unclear mechanisms underlying the gene specificity of BET protein function, small molecules targeting these regulators preferentially suppress the transcription of cancer-promoting genes. As a consequence, BET inhibitors elicit anticancer activity in numerous malignant contexts at doses that can be tolerated by normal tissues, a finding supported by animal studies and by phase I clinical trials in human cancer patients. In this review, we will discuss the remarkable, and often perplexing, therapeutic effects of BET bromodomain inhibition in cancer.
| S-EPMC5495050 | biostudies-literature