Discovery of a small-molecule bromodomain-containing protein 4 inhibitor that induces AMP-activated protein kinase-modulated autophagy-associated cell death in breast cancer

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 antiproliferative 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,immunocytochemistry,si RNA and GFP-m RFP-LC3 plasmid transfections,as well as immunohistochemistry and immunofluorescence.Potential mechanisms were discovered by i TRAQ-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 autophagyassociated cell death(ACD)by BRD4-AMPK interaction,and thus activating AMPK-m TOR-ULK1-modulated autophagic pathway in breast cancer cells.Interestingly,the i TRAQ-based proteomics analyses revealed that 8f induced ACD pathways,involved in HMGB1,VDAC1/2 and e EF2.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.

Inhibition of bromodomain-containing protein 4 enhances the migration of esophageal squamous cell carcinoma cells by inducing cell autophagy

BACKGROUND Esophageal squamous cell carcinoma(ESCC),the predominant type of esophageal cancer,has a 5-year survival rate less than 20%.Although the cause of poor prognosis is the high incidence and mortality of ESCC,the high rate of metastasis after esophageal cancer surgery is the main cause of death after the surgery.Bromodomain-containing protein 4(BRD4),an epigenetic reader of chromatinacetylated histones in tumorigenesis and development,plays an essential role in regulating oncogene expression.BRD4 inhibition and BRD4 inhibition-based treatment can potentially suppress ESCC growth.However,the effects and mechanisms of action of BRD4 on ESCC cell migration remain unclear.AIM To explore the effect of BRD4 on cell migration of ESCC in vitro and its possible molecular mechanism.METHODS Human ESCC cell lines KYSE-450 and KYSE-150 were used.The 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide assay was performed to examine cell proliferation,and the transwell migration assay was conducted to test ESCC cell migration.JQ1,a BRD4 inhibitor,was applied to cells,and BRD4 siRNA was transfected into ESCC cells to knockdown endogenous BRD4.GFP-RFP-LC3 adenovirus was infected into ESCC cells to evaluate the effect of JQ1 on autophagy.Western blotting was performed to determine the protein levels of BRD4,E-cadherin,vimentin,AMP-activated protein kinase(AMPK),and p-AMPK.RESULTS BRD4 was either downregulated by small interfering RNA or pretreated with JQ1 in ESCC cells,leading to increased tumor migration in ESCC cells in a dose-and time-dependent manner.Inhibition of BRD4 not only significantly suppressed cell proliferation but also strongly increased cell migration by inducing epithelial-mesenchymal transition(EMT).The protein expression of vimentin was increased and E-cadherin decreased in a dose-dependent manner,subsequently promoting autophagy in KYSE-450 and KYSE-150 cells.Pretreatment with JQ1,a BRD4 inhibitor,inhibited BRD4-induced LC3-II activation and upregulated AMPK phosphorylation in a dosedependent manner.Additionally,an increased number of autophagosomes and autolysosomes were observed in JQ1-treated ESCC cells.The autophagy inhibitor 3-methyladenine(3-MA)reversed the effects of BRD4 knockdown on ESCC cell migration and blocked JQ1-induced cell migration.3-MA also downregulated the expression of vimentin and upregulation E-cadherin.CONCLUSION BRD4 inhibition enhances cell migration by inducing EMT and autophagy in ESCC cells via the AMPK-modified pathway.Thus,the facilitating role on ESCC cell migration should be considered for BRD4 inhibitor clinical application to ESCC patients.

Bromodomain-containing subunits BRD1, BRD2, and BRD13 are required for proper functioning of SWI/SNF complexes in Arabidopsis

SWI/SNF chromatin remodelers are evolutionarily conserved multiprotein complexes that use the energy of ATP hydrolysis to change chromatin structure.A characteristic feature of SWI/SNF remodelers is the occurrence in both the catalytic ATPase subunit and some auxiliary subunits,of bromodomains,the protein motifs capable of binding acetylated histones.Here,we report that the Arabidopsis bromodomaincontaining proteins BRD1,BRD2,and BRD13 are likely true SWI/SNF subunits that interact with the core SWI/SNF components SWI3C and SWP73B.Loss of function of each single BRD protein caused early flowering but had a negligible effect on other developmental pathways.By contrast,a brd triple mutation(brdx3)led to more pronounced developmental abnormalities,indicating functional redundancy among the BRD proteins.The brdx3 phenotypes,including hypersensitivity to abscisic acid and the gibberellin biosynthesis inhibitor paclobutrazol,resembled those of swi/snf mutants.Furthermore,the BRM protein level and occupancy at the direct target loci SCL3,ABI5,and SVP were reduced in the brdx3 mutant background.Finally,a brdx3 brm-3 quadruple mutant,in which SWI/SNF complexes were devoid of all constituent bromodomains,phenocopied a loss-of-function mutation in BRM.Taken together,our results demonstrate the relevance of BRDs as SWI/SNF subunits and suggest their cooperation with the bromodomain of BRM ATPase.

Correlation of BRD4 and Skp2 expression levels in ultrasound-guided thyroid nodule fine needle aspiration biopsy tissue with the pathological features of nodules

Objective:To study the correlation of bromodomain-containing protein 4(BRD4)and S-phase kinase-associated protein 2(Skp2)expression levels in ultrasound-guided thyroid nodule fine needle aspiration biopsy tissue with the pathological features of nodules.Methods:The tissues obtained in ultrasound-guided thyroid nodule fine needle aspiration biopsy in our hospital between March 2015 and March 2018 was selected and divided into malignant group and benign group according to the pathological results,and the expression levels of BRD4,Skp2,proliferation genes and angiogenesis genes were detected.Results:The BRD4 and Skp2 mRNA expression in thyroid nodules of the malignant group were significantly higher than those of the benign group,and the BRD4 and Skp2 mRNA expression in the malignant group of thyroid nodules with TNM III-IV,capsular invasion and lymph node metastasis were significantly higher than those in the thyroid nodules with TNM I-II,without capsular invasion and without lymph node metastasis;cyclin D1(CCND1),β-catenin,proliferation cell nuclear antigen(PCNA),vascular endothelial growth factor(VEGF),endothelial cell specific molecule-1(ESM-1),Survivin and cyclooxygenase 2(COX2)mRNA expression in thyroid nodules of the malignant group were obviously higher than those of the benign group and positively correlated with BRD4 and Skp2 while cyclin G2(CCNG2)and endostatin(ES)mRNA expression were significantly lower than those of the benign group and negatively correlated with BRD4 and Skp2.Conclusion:The high expression of BRD4 and Skp2 in malignant thyroid nodules is correlated with the pathological changes and can change the expression of proliferation genes and angiogenesis genes.

Design and Synthesis of Novel Bispecific Molecules for Inducing BRD4 Protein Degradation

Proteolysis targeting chimeras（PROTACs） are bispecific molecules containing a target protein binder and a ubiquitin ligase binder connected by a linker. Recently, some heterobifunctional small molecule bromodomain-containing protein 4（BRD4） degraders based on the concept of PROTACs were designed to induce the degradation of BRD4 protein. Herein, we synthesized a new class of PROTAC BRD4 degraders. One of the most promising compound 22f exhibited robust potency of BRD4 inhibition with IC50 value of （9.4±0.6） nmol/L. Furthermore, com- pound 22f potently inhibited cell proliferation in BRD4-sensitive cell lines RS4;11 with IC50 value of （27.6±1.6） nmol/L and capable of inducing degradation of BRD4 protein at 0.5-1.0 μmol/L in the RS4;11 cells. These data establish that compound 22f is a potent and efficacious BRD4 degrader.