Search Results (56)

Defects in lysosomal cholesterol handling provoke fatal disorders presenting neurovisceral symptoms with variable onset and life spans. A prime example is Niemann–Pick type C disease (NPCD), where cholesterol export from the endosomal–lysosomal system is impaired due to variants of either NPC intracellular cholesterol transporter 1 (NPC1) or NPC intracellular cholesterol transporter 2 (NPC2). Therapeutic options for NPCD are limited to palliative care and disease-modifying drugs, and there is a need for new treatments. Here, we explored bromodomain and extra-terminal domain (BET) proteins as new drug targets for NPCD using patient-derived skin fibroblasts. Treatment with JQ1, a prototype BET protein inhibitor, raised the level of NPC1 protein, diminished lysosomal expansion and cholesterol accumulation, and induced extracellular release of lysosomal components in a dose-, time-, and patient-dependent manner. Lastly, JQ1 enhanced and reduced cholesterol accumulation induced by pharmacologic inhibition of NPC1 and of histone deacetylase (HDAC) activity, respectively. Taken together, bromodomain proteins should be further explored as therapeutic drug targets for lysosomal diseases like NPCD, and as new components regulating lysosomal function and cholesterol metabolism. Full article

Background: Myeloid-derived suppressor cells (MDSCs) contribute to immune suppression observed in chronic lymphocytic leukemia (CLL). MDSCs are immature myeloid cells that are hijacked during development and further reprogrammed by the tumor microenvironment (TME) to harbor immune-suppressive properties and inhibit T-cell functions. Bromodomain and extraterminal domain (BET) proteins, including BRD4, are epigenetic modulators that regulate genes implicated in CLL pathogenesis and TME interactions. Previously, we investigated how the novel BET inhibitor OPN-51107 (OPN5) prevents CLL disease expansion, modulates T-cell immune function, and alters gene expression related to MDSCs. In turn, we hypothesize that BET proteins such as BRD4 regulate MDSC functions, and subsequent pharmacological inhibition of BRD4 will alleviate MDSC-mediated immune suppression in CLL. Methods: Utilizing the Eµ-TCL1 mouse model of CLL, we evaluated BRD4 protein expression in MDSCs derived from the bone marrow of transgenic and age-matched wild-type (WT) mice. We then investigated the ex vivo functionality of OPN5-treated MDSCs, expanded from Eµ-TCL1 and WT bone marrow in MDSC-supportive medium. Finally, we conducted an in vivo study utilizing the Eµ-TCL1 adoptive transfer mouse model to determine the in vivo effects of OPN5 on MDSCs and other immune populations. Results: Through the course of this study, we found that MDSCs isolated from Eμ-TCL1 mice upregulate BRD4 expression and are more immune-suppressive than their WT counterparts. Furthermore, we demonstrated ex vivo OPN5 treatment reverses the immune-suppressive capacity of MDSCs isolated from leukemic mice, evident via enhanced T-cell proliferation and IFNγ production. Finally, we showed in vivo OPN5 treatment slows CLL disease progression and modulates immune cell populations, including MDSCs. Conclusions: Altogether, these data support BET inhibition as a useful therapeutic approach to reverse MDSC-mediated immune suppression in CLL. Full article

Neuroinflammation is a key feature of all neurodegenerative disorders, including Alzheimer’s disease, and is tightly regulated by epigenetic mechanisms. Among them, bromodomain and extraterminal domain (BET) proteins play a crucial role by recognizing acetylated histones and acting as transcriptional co-regulators to modulate gene expression. This study investigates the potential of inhibiting BET proteins in preventing microglia-mediated neuronal damage in vitro. Murine BV2 microglial cells were exposed to lipopolysaccharide (LPS) or amyloid-β (Aβ) to induce an inflammatory response, and the subsequent effects on murine HT22 neuronal cells were examined. Among the BET proteins tested, only Brd4 was significantly upregulated in BV2 cells upon pro-inflammatory stimulation. JQ1, a potent pan-inhibitor of BET proteins, suppressed LPS-induced upregulation of pro-inflammatory cytokine mRNA levels, including Il1b, Il6, and Tnf, in BV2 microglia. Pre-treatment with JQ1 attenuated the cytotoxicity of LPS-activated BV2 cells toward neurons. Additionally, conditioned media from Aβ fibril-stimulated BV2 cells induced neuronal cell death, which was partially prevented by pre-treatment with JQ1. Co-culture assays further demonstrated the beneficial effect of BET inhibition. Our findings suggest that targeting BET proteins may offer a neuroprotective strategy by modulating microglial activation, potentially providing therapeutic benefits in neurodegenerative diseases. Full article

Bromodomain and extra-terminal domain (BET) proteins are epigenetic readers that recognize the histone acetylation code and play a critical role in regulating gene transcription. Dysregulation of BET proteins is associated with a number of pathologies, including cancer, inflammation-related metabolic disorders, etc. BET proteins can also be hijacked by some viruses and mediate latent viral infections, making BET proteins promising targets for therapeutic intervention. Research in this area has mainly focused on bromodomain inhibition, with less attention paid to other domains. Bromodomain inhibitors have great potential as anticancer and anti-inflammatory drug candidates. However, their broad-spectrum impact on transcription and potential cross-reactivity with non-BET bromodomain-containing proteins raise concerns about unforeseen side effects. Non-bromodomain BET inhibitors hold promise for gaining better control over the expression of host and viral genes by targeting different stages of BET-dependent transcriptional regulation. In this review, we discuss recent advances in the development of non-bromodomain BET inhibitors, as well as their potential applications, advantages, and perspectives. Full article

Background: Bromodomain and extra-terminal (BET) proteins are critical regulators of gene transcription, as they recognize acetylated lysine residues. The BD1 bromodomain of BRD4, a member of the BET family, has emerged as a promising therapeutic target for various diseases. This study aimed to develop and evaluate a novel C-11 labeled PET radiotracer, [¹¹C]YL10, for imaging the BD1 bromodomain of BRD4 in vivo. Methods: [¹¹C]YL10 was synthesized and evaluated for its ability to bind to the BD1 bromodomain selectively. PET imaging studies were conducted in mice to assess brain penetration, pharmacokinetics, and selectivity. In vitro autoradiography and blocking experiments were performed to confirm the tracer’s specificity for the BD1 domain. Results: [¹¹C]YL10 demonstrated good brain penetration, high selectivity for the BD1 bromodomain, and favorable pharmacokinetics in initial PET imaging studies. In vitro autoradiography and blocking experiments confirmed the specific binding of [¹¹C]YL10 to the BD1 domain of BRD4, further validating its potential as a targeted radiotracer. Conclusions: The development of [¹¹C]YL10 provides a new tool for studying BRD4 bromodomains using PET imaging technology. This radiotracer offers potential advancement in the diagnosis and research of neurodegenerative diseases and related disorders involving BRD4 dysregulation. Full article

Bromodomain and extra-terminal domain (BET) family proteins regulate transcription and recognize lysine residues in histones. Selective BET inhibitors targeting one domain have attracted attention because they maintain normal physiological activities, whereas pan (nonselective) BET inhibitors do not. Osteoarthritis (OA) is a joint disorder characterized by cartilage degeneration for which no treatment currently exists. Here, we investigated whether the selective inhibition of BET proteins is an appropriate therapeutic strategy for OA. We focused on the development and characterization of 2-(4-(2-(dimethylamino)ethoxy)-3,5-dimethylphenyl)-5,7-dimethoxyquinazolin-4(3H)-one (BBC0906), a novel bromodomain 2 (BD2)-specific inhibitor designed to suppress OA progression. Using a DNA-encoded chemical library (DEL) screening approach, BBC0906 was identified because of its high affinity with the BD2 domain of BET proteins. BBC0906 effectively reduced reactive oxygen species (ROS) production and suppressed catabolic factor expression in chondrocytes in vitro. Moreover, in an OA mouse model induced by the destabilization of the medial meniscus (DMM), BBC0906 intra-articular injection attenuated cartilage degradation and alleviated OA. Importantly, BBC0906 selectively inhibits the BD2 domain, thus minimizing its potential side effects. We highlighted the therapeutic potential of targeting BET proteins to modulate oxidative stress and suppress cartilage degradation in OA. BBC0906 is a promising candidate for OA treatment, offering improved safety and efficacy. Full article

The BET (bromodomain and extraterminal domain) family of proteins, particularly BRD4 (bromodomain-containing protein 4), plays a crucial role in transcription regulation and epigenetic mechanisms, impacting key cellular processes such as proliferation, differentiation, and the DNA damage response. BRD4, the most studied member of this family, binds to acetylated lysines on both histones and non-histone proteins, thereby regulating gene expression and influencing diverse cellular functions such as the cell cycle, tumorigenesis, and immune responses to viral infections. Given BRD4’s involvement in these fundamental processes, it is implicated in various diseases, including cancer and inflammation, making it a promising target for therapeutic development. This review comprehensively explores the roles of the BET family in gene transcription, DNA damage response, and viral infection, discussing the potential of targeted small-molecule compounds and highlighting BET proteins as promising candidates for anticancer therapy. Full article

Background: Bromodomain and extra-terminal (BET) domain proteins that bind to acetylated lysine residues of histones serve as the “readers” of DNA acetylation. BRD4 is the most thoroughly studied member of the BET family and regulates the expression of key oncogenes. BRD4 gene amplification has been identified in ovarian cancer (~18–19%) according to The Cancer Genome Atlas (TCGA) analysis. BET inhibitors are novel small molecules that displace BET proteins from acetylated histones and are currently tested in Phase I/II trials. We here aim to explore the prognostic role of the BRD4 gene and protein expression in the ascitic fluid of patients with advanced FIGO III/IV high-grade serous ovarian carcinoma (HGSC). Methods: Ascitic fluid was obtained from 28 patients with advanced stage (FIGO III/IV) HGSC through diagnostic/therapeutic paracentesis or laparoscopy before the initiation of chemotherapy. An amount of ~200 mL of ascitic fluid was collected from each patient and peripheral blood mononuclear cells (PBMCs) were isolated. Each sample was evaluated for BRD4 and GAPDH gene expression through RT-qPCR and BRD4 protein levels through enzyme-linked immunosorbent assay (ELISA). The study protocol was approved by the Institutional Review Board of Alexandra University Hospital and the Committee on Ethics and Good Practice (CEGP) of the National and Kapodistrian University of Athens (NKUA). Results: Low BRD4 gene expression was associated with worse prognosis at 12 months compared to intermediate/high expression (95% CI; 1.75–30.49; p = 0.008). The same association was observed at 24 months although this association was not statistically significant (95% CI; 0.96–9.2; p = 0.065). Progression-free survival was shorter in patients with low BRD4 gene expression at 12 months (5.6 months; 95% CI; 2.6–8.6) compared to intermediate/high expression (9.8 months; 95% CI; 8.3–11.3) (95% CI; 1.2–16.5; p = 0.03). The same association was confirmed at 24 months (6.9 months vs. 13.1 months) (95% CI; 1.1–8.6; p = 0.048). There was a trend for worse prognosis in patients with high BRD4 protein levels versus intermediate/low BRD4 protein expression both at 12 months (9.8 months vs. 7.6 months; p = 0.3) and at 24 months (14.2 months vs. 16.6 months; p = 0.56) although not statistically significant. Again, there was a trend for shorter PFS in patients with high BRD4 protein expression although not statistically significant both at 12 months (p = 0.29) and at 24 months (p = 0.47). Conclusions: There are contradictory data in the literature over the prognostic role of BRD4 gene expression in solid tumors. In our study, intermediate/high BRD4 gene expression was associated with a favorable prognosis in terms of overall survival and progression-free survival compared to low BRD4 gene expression. Full article

Synovial sarcoma (SS), a rare subtype of soft-tissue sarcoma distinguished by expression of the fusion gene SS18-SSX, predominantly affects the extremities of young patients. Existing anticancer drugs have limited efficacy against this malignancy, necessitating the development of innovative therapeutic approaches. Given the established role of SS18-SSX in epigenetic regulation, we focused on bromodomain and extra-terminal domain protein (BET) inhibitors and epigenetic agents. Our investigation of the BET inhibitor ABBV-075 revealed its pronounced antitumor effects, inducing G1-phase cell-cycle arrest and apoptosis, in four SS cell lines. Notably, BET inhibitors exhibited regulatory control over crucial cell-cycle regulators, such as MYC, p21, CDK4, and CDK6. Additionally, RNA sequencing findings across the four cell lines revealed the significance of fluctuating BCL2 family protein expression during apoptotic induction. Notably, variations in the expression ratio of the anti-apoptotic factor BCLxL and the pro-apoptotic factor BIM may underlie susceptibility to ABBV-075. Additionally, knockdown of SS18-SSX, which upregulates BCL2, reduced the sensitivity to ABBV-075. These findings suggest the potential utility of BET inhibitors targeting the SS18-SSX-regulated intrinsic apoptotic pathway as a promising therapeutic strategy for SS. Full article

Type 1 diabetes (T1D) is a metabolic disease resulting from progressive autoimmune destruction of insulin-producing pancreatic beta cells. Although the majority of beta cells are lost in T1D, a small subset undergoes senescence, a stress response involving growth arrest, DNA damage response, and activation of a senescence-associated secretory phenotype (SASP). SASP in beta cells of the nonobese diabetic (NOD) mouse model of T1D and primary human islets is regulated at the level of transcription by bromodomain extra-terminal (BET) proteins, but the mechanisms remain unclear. To explore how SASP is transcriptionally regulated in beta cells, we used the NOD beta cell line NIT-1 to model beta cell SASP and identified binding partners of BET protein Brd4 and explored the role of the cyclin-dependent kinase inhibitor p21. Brd4 interacted with a variety of proteins in senescent NIT-1 cells including subunits of the Ino80 chromatin remodeling complex, which was expressed in beta cells during T1D progression in NOD mice and in human beta cells of control, autoantibody-positive, and T1D donors as determined from single-cell RNA-seq data. RNAi knockdown of p21 during senescence in NIT-1 cells did not significantly impact viability or SASP. Taken together, these results suggest that Brd4 interacts with several protein partners during senescence in NIT-1 cells, some of which may play roles in SASP gene activation and that p21 is dispensable for the SASP in this beta cell model. Full article

Peritoneal dialysis (PD) is a current replacement therapy for end-stage kidney diseases (ESKDs). However, long-term exposure to PD fluids may lead to damage of the peritoneal membrane (PM) through mechanisms involving the activation of the inflammatory response and mesothelial-to-mesenchymal transition (MMT), leading to filtration failure. Peritoneal damage depends on a complex interaction among external stimuli, intrinsic properties of the PM, and subsequent activities of the local innate–adaptive immune system. Epigenetic drugs targeting bromodomain and extra-terminal domain (BET) proteins have shown beneficial effects on different experimental preclinical diseases, mainly by inhibiting proliferative and inflammatory responses. However the effect of BET inhibition on peritoneal damage has not been studied. To this aim, we have evaluated the effects of treatment with the BET inhibitor JQ1 in a mouse model of peritoneal damage induced by chlorhexidine gluconate (CHX). We found that JQ1 ameliorated the CHX-induced PM thickness and inflammatory cell infiltration. Moreover, JQ1 decreased gene overexpression of proinflammatory and profibrotic markers, together with an inhibition of the nuclear factor-κB (NF-κB) pathway. Additionally, JQ1 blocked the activation of nuclear factor erythroid 2-related factor 2 (NRF2) and restored changes in the mRNA expression levels of NADPH oxidases (NOX1 and NOX4) and NRF2/target antioxidant response genes. To corroborate the in vivo findings, we evaluated the effects of the BET inhibitor JQ1 on PD patients’ effluent-derived primary mesothelial cells and on the MeT-5A cell line. JQ1 inhibited tumor necrosis factor-α (TNF-α)-induced proinflammatory gene upregulation and restored MMT phenotype changes, together with the downmodulation of oxidative stress. Taken together, these results suggest that BET inhibitors may be a potential therapeutic option to ameliorate peritoneal damage. Full article

Epigenetics play a crucial role in gene regulation and cellular processes. Most importantly, its dysregulation can contribute to the development of tumors. Epigenetic modifications, such as DNA methylation and histone acetylation, are reversible processes that can be utilized as targets for therapeutic intervention. DNA methylation inhibitors disrupt DNA methylation patterns by inhibiting DNA methyltransferases. Such inhibitors can restore normal gene expression patterns, and they can be effective against various forms of cancer. Histone deacetylase inhibitors increase histone acetylation levels, leading to altered gene expressions. Like DNA methylation inhibitors, histone methyltransferase inhibitors target molecules involved in histone methylation. Bromodomain and extra-terminal domain inhibitors target proteins involved in gene expression. They can be effective by inhibiting oncogene expression and inducing anti-proliferative effects seen in cancer. Understanding epigenetic modifications and utilizing epigenetic inhibitors will offer new possibilities for cancer research. Full article

Feline leukemia virus (FeLV) is a cosmopolitan gammaretrovirus that causes lifelong infections and fatal diseases, including leukemias, lymphomas, immunodeficiencies, and anemias, in domestic and wild felids. There is currently no definitive treatment for FeLV, and while existing vaccines reduce the prevalence of progressive infections, they neither provide sterilizing immunity nor prevent regressive infections that result in viral reservoirs with the potential for reactivation, transmission, and the development of associated clinical diseases. Previous studies of murine leukemia virus (MuLV) established that host cell epigenetic reader bromodomain and extra-terminal domain (BET) proteins facilitate MuLV replication by promoting proviral integration. Here, we provide evidence that this facilitatory effect of BET proteins extends to FeLV. Treatment with the archetypal BET protein bromodomain inhibitor (+)-JQ1 and FeLV challenge of two phenotypically disparate feline cell lines, 81C fibroblasts and 3201 lymphoma cells, significantly reduced FeLV proviral load, total FeLV DNA load, and p27 capsid protein expression at nonlethal concentrations. Moreover, significant decreases in FeLV proviral integration were documented in 81C and 3201 cells. These findings elucidate the importance of BET proteins for efficient FeLV replication, including proviral integration, and provide a potential target for treating FeLV infections. Full article

Bromodomain and extra-terminal domain (BET) proteins are epigenetic modulators that regulate gene transcription through interacting with acetylated lysine residues of histone proteins. BET proteins have multiple roles in regulating key cellular functions such as cell proliferation, differentiation, inflammation, oxidative and redox balance, and immune responses. As a result, BET proteins have been found to be actively involved in a broad range of human lung diseases including acute lung inflammation, asthma, pulmonary arterial hypertension, pulmonary fibrosis, and chronic obstructive pulmonary disease (COPD). Due to the identification of specific small molecular inhibitors of BET proteins, targeting BET in these lung diseases has become an area of increasing interest. Emerging evidence has demonstrated the beneficial effects of BET inhibitors in preclinical models of various human lung diseases. This is, in general, largely related to the ability of BET proteins to bind to promoters of genes that are critical for inflammation, differentiation, and beyond. By modulating these critical genes, BET proteins are integrated into the pathogenesis of disease progression. The intrinsic histone acetyltransferase activity of bromodomain-containing protein 4 (BRD4) is of particular interest, seems to act independently of its bromodomain binding activity, and has implication in some contexts. In this review, we provide a brief overview of the research on BET proteins with a focus on BRD4 in several major human lung diseases, the underlying molecular mechanisms, as well as findings of targeting BET proteins using pharmaceutical inhibitors in different lung diseases preclinically. Full article

Aging is a key independent risk factor of various vascular diseases, for which the regulatory mechanisms remain largely unknown. Bromodomain-containing protein 4 (BRD4) is a member of the Bromodomain and Extra-Terminal domain (BET) family and is an epigenetic reader playing diverse roles in regulating transcriptional elongation, chromatin remodeling, DNA damage response, and alternative splicing in various cells and tissues. While BRD4 was initially recognized for its involvement in cancer progression, recent studies have revealed that the aberrant expression and impaired function of BRD4 were highly associated with aging-related vascular pathology, affecting multiple key biological processes in the vascular cells and tissues, providing new insights into the understanding of vascular pathophysiology and pathogenesis of vascular diseases. This review summarizes the recent advances in BRD4 biological function, and the progression of the studies related to BRD4 in aging-associated vascular pathologies and diseases, including atherosclerosis, aortic aneurism vascular neointima formation, pulmonary hypertension, and essential hypertension, providing updated information to advance our understanding of the epigenetic mechanisms in vascular diseases during aging and paving the way for future research and therapeutic approaches. Full article