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The bromodomain and extraterminal domain (Bet) family are the regulators of the epigenome and also the pivotal driving factors for the expression of tumor related genes that tumor cells depend on for survival and proliferation. Bromodomain-containing protein 4 (Brd4) is a member of the Bet protein family. Generally, Brd4 identifies acetylated histones and binds to the promoter or enhancer region of target genes to initiate and maintain expression of tumor related genes. Brd4 is closely related to the regulation of multiple transcription factors and chromatin modification and is involved in DNA damage repair and maintenance of telomere function, thus maintaining the survival of tumor cells. This review summarizes the structure and function of Brd4 protein and the application of its inhibitors in tumor research.
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Humans , Transcription Factors/metabolism , Nuclear Proteins/metabolism , Histones , Cell Cycle Proteins/metabolism , Neoplasms/metabolism , Protein DomainsABSTRACT
Objective:To investigate the effects of bromodomain and extraterminal domain (BET) inhibitor JQ1 combined with siPD-L1 on the proliferation and apoptosis of oral squamous cell carcinoma (OSCC) Scc-25 cells and its mechanism.Methods:Scc-25 cells were cultured in vitro and treated with different concentrations of JQ1 (0, 0.2, 1, 5 μmol/L). Cell proliferation was detected by cell count kit-8 (CCK-8) assay; the expression levels of programmed cell death ligand 1(PD-L1) and forkhead box M1(FoxM1) protein were detected by Western blot. Appropriate concentration of JQ1 was selected for subsequent experiments. Scc-25 cells were divided into four groups: control group (without any treatment), siPD-L1 group (transfected with siPD-L1), JQ1 group (added JQ1 after transfected with non-specific siRNA), and combined treatment group (added JQ1 after transfected with siPD-L1). CCK-8 assay was used to detect the proliferation ability of Scc-25 cells in each group. Western blot was used to detect the expression levels of cleaved caspase-3, PD-L1 and FoxM1, and flow cytometry was used to detect the apoptosis rate of cells in each group. Results:With the increase of JQ1 concentration, the proliferation ability of SCC-25 cells and the expression levels of PD-L1 and FoxM1 decreased gradually (all P<0.01). JQ1 concentration of 1 μmol/L had obvious inhibitory effect on cell proliferation and the expression levels of PD-L1 and FoxM1, so JQ1 concentration of 1 μmol/L was selected for subsequent experiments. The proliferation ability of Scc-25 cells, the expression of PD-L1 and FoxM1 proteins in JQ1 group, siPD-L1 group and combination treatment group were significantly lower than those in the control group (all P<0.01), and the expression of cleaved caspase-3 protein and the rate of apoptosis were significantly higher than those in the control group (all P<0.01); Moreover, the effect of the combination treatment group was more significant than that of siPD-L1 group, JQ1 group (all P<0.01). Conclusions:The combination of JQ1 and siPD-L1 could effectively inhibit the proliferation and promotes the apoptosis of OSCC Scc-25 cells, and its mechanism may be related to the suppression of PD-L1 and FoxM1 signaling pathways.
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Objective To explore the expression and role of bromodomain-containing protein 4(BRD4) in spinal cord of mice which suffered inflammatory pain induced by formaldelryde solution. Methods Thirty-two ICR mice were randomly divided into normal saline group and formaldehyde injection 5 minutes, 30 minutes and 60 minutes groups, with 8 mice in each group. The expression of BRD4 protein and mRNA in spinal cord of mice in each group were detected by Western blotting (n = 4/group) and Real-time PCR (n = 4/group); 66 mice were randomly divided into formaldelryde injection group, vehicle (DMSO) plus formaldelryde injection group and 6. 25, 12. 5, 25 and 50 mg/kg JQl injection plus formaldelryde solution group, with 11 mice in each group. The effect of BRD4 inhibitor JQl on spontaneous pain in each group was observed (n= 11/group); Immunohistochemistry (n= 3/group), Real-time PCR (n = 4/group) or Western blotting (n= 4/group) were used to detect the effects of 25 mg/kg JQ1 on the expression of c-fos and glutamate receptor 2 (GluR2) in the spinal cord of model mice. Results The result showed that levels of BRD4 protein (P<0. 01) and mRNA in spinal cord increased significantly 30 min and 60 min after formaldehyde solution injection (P<0. 05). The behavioral test showed that both 25 mg/kg and 50 mg/kg JQf administration could reduce the second phase spontaneous pain compared with the solvent (DMSO) group (P < 0 . 05). Furthennore, immunohistochemistry and Real-time PCR result showed that 25 mg/kg JQf injection could significantly reduce positive numbers (P<0. 01) and high mRNA expression of c-fos in mouse spinal cord induced by formaldehyde solution (P < 0 . 05), and the Western blotting result showed that 25 mg/kg JQf administration could significantly reduce the expression of glutamate receptor GluR2 (P < 0. OOf). Conclusion BRD4 may play an important role in the induction of central sensitization of inflammatory pain, and JQf may alleviate inflammatory pain behavior by inhibiting the formation of central sensitization of pain.
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AIM:To investigate the effect of bromodomain-containing protein 4(BRD4)inhibitors on the via-bility and apoptosis of activated B cell-like diffuse large B-cell lymphoma(ABC-DLBCL)cells and the molecular mecha-nism. METHODS:The ABC-DLBCL cells were treated with BRD4 inhibitors JQ1 and I-BET-762,and Bruton tyrosine kinase(BTK)inhibitor ibrutinib. The viability and death of the cells were determined by CCK-8 assay and PI staining,re-spectively. The mRNA levels of BTK,phospholipase Cγ(PLCγ),LYN,SYK,interleukin-6(IL-6),MYC,protein ki-nase Cβ(PKCβ),mucosa-associated lymphoid tissue lymphoma translocation protein 1(MALT1),MYC and RELA were detected by real-time PCR. The protein levels of BTK,PLCγ,MYC and RELA were determined by Western blot. Super-enhancer around BTK gene was revealed by bioinformatics analysis. RESULTS:The ABC-DLBCL cells were sensitive to BRD4/super-enhancer inhibitors such as JQ1 and I-BET-762. Both JQ1 and I-BET-762 inhibited the chronic active B-cell receptor(BCR)/nuclear factorκB(NFκB)signaling through reducing the transcription of BTK,but they had minimal ef-fect on other components in BCR/NFκB signaling. Interestingly,there was no super-enhancer around BTK gene,and the inhibitory effect of JQ1 was likely due to disruption of BRD4 binding within BTK gene. Inhibition of BRD4 had synergic ef-fect with BTK inhibitor ibrutinib. Moreover,inhibition of BRD4 induced significant cell death in ibrutinib-resistant ABC-DLBCL cells. CONCLUSION:Inhibitors of BRD4 induce ABC-DLBCL cell death via blocking BCR/NFκB signaling and has synergic effect with BTK inhibitor. Inhibition of BRD4 might be a promising strategy for treatment of ABC-DLBCL,es-pecially ibrutinib-resistant ABC-DLBCL.
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ObjectiveTo study the effect of Xianlian Jiedu prescription （XLJDP） on the activation of nuclear transcription factor-κB （NF-κB） signaling pathway induced by bromodomain-containing protein 4 （Brd4） in hypoxic microenvironment and to explore its mechanism in inhibiting the proliferation of colorectal cancer HT-29 cells. MethodThe human colorectal cancer HT-29 cells were cultured in a hypoxic incubator or normoxia incubator and treated with XLJDP at 0.8，1，1.2，1.6，3.2，6.4，and 12.8 g·L-1 for 48 h， respectively. Following the detection of cell vitality using methyl thiazolyl tetrazolium （MTT） colorimetry， the effects of XLJDP （1.25，2.5，and 5 g·L-1） on the cell mitochondrial membrane potential were determined using a fluorescent probe （JC-1）， and the apoptosis of colorectal cancer HT-29 cells was detected by flow cytometry. The cell colony formation assay and 5-ethynyl-2'-deoxyuridine （EDU） staining were conducted to test the proliferation of colorectal cancer HT-29 cells. The Western blot was carried out to measure the expression levels of Brd4 and its downstream relevant proteins such as c-Myc and hexamethylene bisacetamide-inducible protein 1 （HEXIM1）， as well as the effects of XLJDP on related proteins in the NF-κB signaling pathway. ResultCompared with the blank control group， XLJDP at 0.8，1，1.2，1.6，3.2，6.4，and 12.8 g·L-1 inhibited the vitality of colorectal cancer HT-29 cells （P<0.05 ， P<0.01）， with the median inhibitory concentration （IC50） under the hypoxic condition higher than that under the normoxia condition. Compared with the blank control group， XLJDP at 1.25，2.5，and 5 g·L-1 significantly decreased the mitochondria membrane potential， enhanced the apoptosis （P<0.05，P<0.01）， and lowered the number of cell colonies and also the EDU-positive cells （P<0.05， P<0.01）. The results of Western blot showed that compared with the blank control group， XLJDP at 1.25，2.5，and 5 g·L-1 down-regulated Brd4， c-Myc， p-NF-κB p65， and p-IκBα protein expression to varying degrees and up-regulated the expression of HEXIM1 （P<0.05， P<0.01）. ConclusionIn the hypoxic microenvironment， XLJDP inhibits the proliferation of colorectal cancer HT-29 cells regulated by Brd4， which may be related to its inhibition of the activation of NF-κB signaling pathway.
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Medulloblastoma (MB) is a common yet highly heterogeneous childhood malignant brain tumor, however, clinically effective molecular targeted therapy is lacking. Modulation of hedgehog (HH) signaling by epigenetically targeting the transcriptional factors GLI through bromodomain-containing protein 4 (BRD4) has recently spurred new interest as potential treatment of HH-driven MB. Through screening of current clinical BRD4 inhibitors for their inhibitory potency against glioma-associated oncogene homolog (GLI) protein, the BRD4 inhibitor
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Objective: To investigate the effects of bromodomain-containing protein 4 (BRD4) inhibitor I-BET762 on histone crotonylation, proliferation and migration of prostate cancer cells. Methods: Three human prostate cancer cell lines, i.e., LNCaP, C4-2B and PC-3, were respectively treated with I-BET762 of half maximal inhibitory concentration. Histone crotonylation modification and acetylase expression were detected by Western blotting. CCK-8, transwell migration test and scratch test were used to detect the effects of I-BET762 on proliferation and migration of LNCaP, C4-2B and PC-3 cells. Results: I-BET762 inhibited the expression of histone acetylase P300 and GCN5, and reduced the histone crotonylation modification. Transwell migration test and scratch test showed that I-BET762 could inhibit the migration of prostate cancer cell lines LNCaP, C4-2B and PC-3 (all P<0.01); CCK-8 test showed that the proliferation of three prostate cancer cell lines was inhibited by I-BET762. Conclusion: In prostate cancer cells, I-BET762 can reduce the histone crotonylation and also inhibit cell proliferation and migration.
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Objective To investigate the expression of BRD 4 in the spinal cord and its relationship with acute in-flammation pain induced by formaldehyde in mice.Methods Thirty-six mice were randomly divided into three groups:control group,formaldehyde group and indomethacin+formaldehyde group;25 μL 1%formaldehyde was injected into the right plantar to establish the acute inflammationpain model,while the indomethacin(20 mg/kg) was injected intraperitoneally 1 hour before formaldehyde injection.Then,all the mice were video recored for 1h to observe the spontaneous pain.Then,cell localization of BRD4 in the spinal cord of normal mice was determined by immunofluorescence assasy.The expression of BRD4 in spinal cord was detected by immunohistochemistry and Western blot.Results Immunofluorescence showed that BRD 4 was mainly co-locolized with the neuronal marker NeuN in the spinal cord of normal mice.Formaldehyde injection could induce two-phase spontaneous pain, while indomethacin intervention could only decrease the second phase pain(P<0.05).Furthermore,formaldehyde injec-tion led to significantly enhanced expression of BRD 4 in bilateral spinal cord,which was remarkbly inhibited by in-domethacin(P<0.05).Conclusions Up-regulation of BRD4 in spinal dorsal horn may be involved in the acute in-flammatory pain.
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In the last several year, the bromodomain and extra-terminal domain(BET) subfamily has been an extensively researched target. The bromodomain-containing protein 4(BRD4) belongs to this subfamily. It can regulate transcription, mark the mitosis of mammals, and regulate cell cycle so that it plays a quite significant role in the development and progression of cancer as well as the production of fibrosis and inflammation. Therefore BRD4 inhibitors have been widely studied for the treatment of solid tumors, leukemia, and fibrosis. Based on vast literature, this paper mainly described the structure and function of BRD4 as well as the latest progress in the research of the structure-activity relationship of BRD4 inhibitors.
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Objective·To investigate effect and the possible molecular mechanism of JQ1,a specific inhibitor of bromodomain containing protein 4,on human hypertropic scar.Methods·Primary fibroblasts were isolated from human hypertrophic scars and treated with JQ-1 of different concentrations (0.1,0.5,1.0,2.0,2.5,and 12.5μmol/L) for 48 h.Then CCK-8 kit and wound healing assay were used to measure proliferation and migration of the fibroblasts.ELISA was adopted to detect the levels of collagen type Ⅰ (COL Ⅰ) and TGF-β1 after JQ-1 treatment for 24 h.Thirty-six nude mice were used for hypertrophic scar models.Human hypertrophic scars (1.0 cm× 1.0 cm×0.5 cm) were grafted subcutaneously at the backs of nude mice to establish scar animal models.After 4 weeks,the nude mice were averagely divided into two groups,i.e.JQ-1 group and DMSO group,which were respectively injected with 0.5 μmol/L JQ-1 and 0.1％ DMSO each mouse every day.COL Ⅰ / Ⅲ and α-smooth muscle actin (α-SMA) were examined by immunohistochemical method and sirius red staining.Results·Cell experiments showed that JQ-1 with the concentration of 0.5 μmol/L and above significantly inhibited proliferation of fibroblasts (P＜0.01).JQ-1 inhibited migration of fibroblast (P＜0.01).JQ-1 inhibited secretion of COL Ⅰ and TGF-β1 of fibroblasts (P＜0.01).Animal experiments showed that concentration and proportion of COL Ⅰ / Ⅲ in JQ-1 group decreased compared to DMSO group (P＜0.05).α-SMA protein expression in JQ-1 group also decreased (P＜0.05).Conclusion·JQ-1 can inhibit proliferation,migration,secretion of COL Ⅰ,and production of TGF-β1 of human sear fibroblasts in vitro;it can also inhibit secretion of COL Ⅰ /Ⅲ and fibroblast-myofibroblast differentiation in the human hypertrophic scars in nude mice.
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OBJECTIVE To discover a small-molecule bromodomain-containing protein 4 (BRD4) inhibitor that induces AMP- activated protein kinase- modulated autophagy- associated cell death in breast cancer and exploreits potential mechanisms. METHODS BRD4 interactors were analyzed by PPI network prediction and The Cancer Genome Atlas (TCGA) analysis. The interaction between BRD4 and AMPK was confirmed by co- immunoprecipitation assay. Novel BRD4 inhibitors were designed and synthesized based upon pharmacophore analysis of BRD4 (1), then screened by anti-proliferative activity and Alpha Screen of BRD4 (1). The selectivity of the best candidate compound 8f was validated by co-crystallization, FRET assay and co-immuno precipitation assay. The mechanisms of 8f were investigated by fluorescence microscopy, electron microscopy, Western blotting, immunocy?tochemistry, siRNA and GFP-mRFP-LC3 plasmid transfections, as well as immunohistochemistry and immunofluorescence. Potential mechanisms were discovered by iTRAQ- based proteomics analysis and the therapeutic effect of 8f was assessed by xenograft breast cancer mouse and zebrafish models. RESULTS We identified that BRD4 interacted with AMPK, which was remarkably downregulated in breast cancer. We next designed and synthesized 49 candidate compounds, and eventually discovered a selective small-molecule inhibitor of BRD4 (8f). Subsequently, 8f was discovered to induce autophagy-associated cell death (ACD) by BRD4- AMPK interaction, and thus activating AMPK- mTOR- ULK1-modulated autophagic pathway in breast cancer cells. Interestingly, the iTRAQ- based proteomics analyses revealed that 8f induced ACD pathways, involved in HMGB1, VDAC1/2 and eEF2. Moreover, 8f displayed a therapeutic potential on both xenograft breast cancer mouse and zebrafish models. CONCLUSION We discovered a novel small-molecule inhibitor of BRD4 that induces BRD4-AMPK-modulated ACD in breast cancer, which may provide a candidate drug for future cancer therapy.