Chromatin Landscape of the IRF Genes and Role of the Epigenetic Reader BRD4

A BET inhibitor, NHWD-870, can downregulate dendritic cells maturation via the IRF7-mediated signaling pathway to ameliorate imiquimod-induced psoriasis-like murine skin inflammation

Psoriasis is a chronic, recurrent, inflammatory dermatosis accompanied by excessive activation of dendritic cells (DCs), which are primarily responsible for initiating an immune response. The bromodomain and extraterminal domain (BET) family plays a pivotal role in the transcriptional regulation of inflammation and its inhibitors can downregulate DCs maturation and activation. Here we investigated the effect of NHWD-870, a potent BET inhibitor, on inflammation in an imiquimod (IMQ)-induced psoriasis-like mouse model and murine bone marrow-derived dendritic cells (BMDCs) stimulated by lipopolysaccharide (LPS) and IMQ. Application of NHWD-870 significantly ameliorated IMQ-triggered skin inflammation in mice, and markers associated with DC maturation (CD40, CD80 and CD86) were decreased in skin lesions, spleen and lymph nodes. Additionally, NHWD-870 reduced LPS or IMQ induced DCs maturation and activation in vitro, with lower expression of inflammatory cytokines [interleukin (IL)-12, IL-23, tumor necrosis factor-α, IL-6, IL-1β, chemokine (C-X-C motif) ligand (CXCL)9 and CXCL10]. In addition, we found that interferon regulatory factor 7 (IRF7) significantly increased during DCs maturation, and inhibition of IRF7 could impair BMDCs maturation and activation. What's more, IRF7 was highly expressed in both psoriatic patients and IMQ-induced psoriasis-like mice. Single-cell RNA sequencing of normal and psoriatic skin demonstrated that IRF7 expression was increased in DCs of psoriatic skin. While NHWD-870 could inhibit IRF7 and phosphorylated-IRF7 expression in vivo and in vitro. These results indicate that NHWD-870 suppresses the maturation and activation of DCs by decreasing IRF7 proteins which finally alleviates psoriasis-like skin lesions, and NHWD-870 may be a potent therapeutic drug for psoriasis.

Cell Death Pathway Regulation by Functional Nanomedicines for Robust Antitumor Immunity

Cancer immunotherapy has become a mainstream cancer treatment over traditional therapeutic modes. Cancer cells can undergo programmed cell death including ferroptosis, pyroptosis, autophagy, necroptosis, apoptosis and cuproptosis which are find to have intrinsic relationships with host antitumor immune response. However, direct use of cell death inducers or regulators may bring about severe side effects that can also be rapidly excreted and degraded with low therapeutic efficacy. Nanomaterials are able to carry them for long circulation time, high tumor accumulation and controlled release to achieve satisfactory therapeutic effect. Nowadays, a large number of studies have focused on nanomedicines-based strategies through modulating cell death modalities to potentiate antitumor immunity. Herein, immune cell types and their function are first summarized, and state-of-the-art research progresses in nanomedicines mediated cell death pathways (e.g., ferroptosis, pyroptosis, autophagy, necroptosis, apoptosis and cuproptosis) with immune response provocation are highlighted. Subsequently, the conclusion and outlook of potential research focus are discussed.

Short-Term UVB Irradiation Leads to Persistent DNA Damage in Limbal Epithelial Stem Cells, Partially Reversed by DNA Repairing Enzymes

The cornea is frequently exposed to ultraviolet (UV) radiation and absorbs a portion of this radiation. UVB in particular is absorbed by the cornea and will principally damage the topmost layer of the cornea, the epithelium. Epidemiological research shows that the UV damage of DNA is a contributing factor to corneal diseases such as pterygium. There are two main DNA photolesions of UV: cyclobutane pyrimidine dimers (CPDs) and pyrimidine-pyrimidone (6-4) photoproducts (6-4PPs). Both involve the abnormal linking of adjacent pyrimide bases. In particular, CPD lesions, which account for the vast majority of UV-induced lesions, are inefficiently repaired by nucleotide excision repair (NER) and are thus mutagenic and linked to cancer development in humans. Here, we apply two exogenous enzymes: CPD photolyase (CPDPL) and T4 endonuclease V (T4N5). The efficacy of these enzymes was assayed by the proteomic and immunofluorescence measurements of UVB-induced CPDs before and after treatment. The results showed that CPDs can be rapidly repaired by T4N5 in cell cultures. The usage of CPDPL and T4N5 in ex vivo eyes revealed that CPD lesions persist in the corneal limbus. The proteomic analysis of the T4N5-treated cells shows increases in the components of the angiogenic and inflammatory systems. We conclude that T4N5 and CPDPL show great promise in the treatment of CPD lesions, but the complete clearance of CPDs from the limbus remains a challenge.

Bromodomain-containing protein 4 (BRD4): a key player in inflammatory bowel disease and potential to inspire epigenetic therapeutics

INTRODUCTION

Inflammatory bowel diseases (IBDs) are debilitating chronic inflammatory disorders with increasing prevalence worldwide. Epigenetic regulator bromodomain-containing protein 4 (BRD4) is critical in controlling gene expression of IBD-associated inflammatory cytokine networks. BRD4 as a promising therapeutic target is also tightly associated with many other diseases, such as airway inflammation and fibrosis, cancers, infectious diseases and central nervous system disorders.

AREAS COVERED

This review briefly summarized the critical role of BRD4 in the pathogenesis of IBDs and the current clinical landscape of developing bromodomain and extra terminal domain (BET) inhibitors. The challenges and opportunities as well as future directions of targeting BRD4 inhibition for potential IBD medications were also discussed.

EXPERT OPINION

Targeting BRD4 with potent and specific inhibitors may offer novel effective therapeutics for IBD patients, particularly those who are refractory to anti-TNFα therapy and IBD-related profibrotic. Developing highly specific BRD4 inhibitors for IBD medications may help erase the drawbacks of most current pan-BET/BRD4 inhibitors, such as off-target effects, poor oral bioavailability, and low gut mucosal absorbance. Novel strategies such as combinatorial therapy, BRD4-based dual inhibitors and proteolysis targeting chimeras (PROTACs) may also have great potential to mitigate side effects and overcome drug resistance during IBD treatment.

Versatile Nano-PROTAC-Induced Epigenetic Reader Degradation for Efficient Lung Cancer Therapy

Recent evidence has indicated that overexpression of the epigenetic reader bromodomain-containing protein 4 (BRD4) contributes to a poor prognosis of lung cancers, and the suppression of its expression promotes cell apoptosis and leads to tumor shrinkage. Proteolysis targeting chimera (PROTAC) has recently emerged as a promising therapeutic strategy with the capability to precisely degrade targeted proteins. Herein, a novel style of versatile nano-PROTAC (CREATE (CRV-LLC membrane/DS-PLGA/dBET6)) is developed, which is constructed by using a pH/GSH (glutathione)-responsive polymer (disulfide bond-linked poly(lactic-co-glycolic acid), DS-PLGA) to load BRD4-targeted PROTAC (dBET6), followed by the camouflage with engineered lung cancer cell membranes with dual targeting capability. Notably, CREATE remarkably confers simultaneous targeting ability to lung cancer cells and tumor-associated macrophages (TAMs). The pH/GSH-responsive design improves the release of dBET6 payload from nanoparticles to induce pronounced apoptosis of both cells, which synergistically inhibits tumor growth in both subcutaneous and orthotopic tumor-bearing mouse model. Furthermore, the efficient tumor inhibition is due to the direct elimination of lung cancer cells and TAMs, which remodels the tumor microenvironment. Taken together, the results elucidate the construction of a versatile nano-PROTAC enables to eliminate both lung cancer cells and TAMs, which opens a new avenue for efficient lung cancer therapy via PROTAC.

Clinical Significance of MAP-7 and FOXC1 in Egyptian Acute Myeloid Leukemia Patients

PURPOSE

The present study aimed to report the clinical correlations and prognostic significance of microtubule-associated protein-1 (MAP-7) and forkhead box transcription factor-C1 (FOXC1) expression in Egyptian patients with newly diagnosed acute myeloid leukemia (AML).

METHODS

The study included 80 adults with newly diagnosed AML. Laboratory investigations included complete blood count, morphological examination of bone marrow aspirate, immunophenotyping, conventional karyotyping and molecular study for fms-like tyrosine kinase 3 (FLT3), nucleophosmin-1 (NPM1) and CCAAT/enhancer binding protein α (CEBPA) mutations. MAP-7 and FOXC1 expressions in bone marrow were determined using RT-PCR. Patients were followed for a median (range) period of 6.4 (1.0-35) months. The study outcomes included treatment response, progression-free survival (PFS) and overall survival (OS).

RESULTS

Patients with low FOXC1 expression had significantly lower mortality rate (60.0 % versus 84.6 %, p=0.021), significantly longer PFS duration and significantly longer OS. No significant differences were noted between MAP7 expression groups regarding treatment response, mortality rate, PFS duration and OS duration. Interestingly, a significant direct correlation was noted between FOXC1 and MAP7 expressions (r=0.25, p=0.027).

CONCLUSIONS

FOXC1 and MAP7 expressions are significantly correlated. High expression of FOXC1 in Egyptian population may be related to shorter OS and PFS.

N-terminal BET bromodomain inhibitors disrupt a BRD4-p65 interaction and reduce inducible nitric oxide synthase transcription in pancreatic β-cells

Chronic inflammation of pancreatic islets is a key driver of β-cell damage that can lead to autoreactivity and the eventual onset of autoimmune diabetes (T1D). In the islet, elevated levels of proinflammatory cytokines induce the transcription of the inducible nitric oxide synthase (iNOS) gene, NOS2, ultimately resulting in increased nitric oxide (NO). Excessive or prolonged exposure to NO causes β-cell dysfunction and failure associated with defects in mitochondrial respiration. Recent studies showed that inhibition of the bromodomain and extraterminal domain (BET) family of proteins, a druggable class of epigenetic reader proteins, prevents the onset and progression of T1D in the non-obese diabetic mouse model. We hypothesized that BET proteins co-activate transcription of cytokine-induced inflammatory gene targets in β-cells and that selective, chemotherapeutic inhibition of BET bromodomains could reduce such transcription. Here, we investigated the ability of BET bromodomain small molecule inhibitors to reduce the β-cell response to the proinflammatory cytokine interleukin 1 beta (IL-1β). BET bromodomain inhibition attenuated IL-1β-induced transcription of the inflammatory mediator NOS2 and consequent iNOS protein and NO production. Reduced NOS2 transcription is consistent with inhibition of NF-κB facilitated by disrupting the interaction of a single BET family member, BRD4, with the NF-κB subunit, p65. Using recently reported selective inhibitors of the first and second BET bromodomains, inhibition of only the first bromodomain was necessary to reduce the interaction of BRD4 with p65 in β-cells. Moreover, inhibition of the first bromodomain was sufficient to mitigate IL-1β-driven decreases in mitochondrial oxygen consumption rates and β-cell viability. By identifying a role for the interaction between BRD4 and p65 in controlling the response of β-cells to proinflammatory cytokines, we provide mechanistic information on how BET bromodomain inhibition can decrease inflammation. These studies also support the potential therapeutic application of more selective BET bromodomain inhibitors in attenuating β-cell inflammation.

In Vivo Delivery of siRNAs Targeting EGFR and BRD4 Expression by Peptide-Modified Redox Responsive PEG-PEI Nanoparticles for the Treatment of Triple-Negative Breast Cancer

The study aims to investigate the in vivo distribution, antitumor effect, and safety of cell membrane-penetrating peptide-modified disulfide bond copolymer nanoparticles loaded with small-interfering RNA (siRNA) targeting epidermal growth factor receptor (EGFR) and bromodomain-containing protein 4 (BRD4) in triple-negative breast cancer (TNBC). Polyethylene glycol disulfide bond-linked polyethylenimine (PEG-SS-PEI) was modified with peptides GALA and CREKA and used as vectors to prepare siRNA nanoparticles. The GALA- and CREKA-modified PEG-SS-PEI nanoparticles (GC-NPs) were prepared by mixing siEGFR and siBRD4 (1:1) with GALA-PEG-SS-PEI and CREKA-PEG-SS-PEI (1:1) in an aqueous solution at an N/P ratio of 30:1. Nanoparticles loaded with scrambled siRNA were prepared with the same method. The gene silencing effect on EGFR and BRD4 in vitro was evaluated by Western blotting analysis. TNBC xenograft models were established by subcutaneous injection of MDA-MB-231 cells into female nude mice. At 1, 3, 6, 12, and 24 h after administration of five formulations of Cy5-siRNA (133 μg/10 g) via the tail vein, the mice were observed and imaged for a biodistribution study using an in vivo imaging system. In the pharmacodynamics experiment, tumor-bearing mice were treated with respective siRNA preparations at a dose of 133 μg/10 g for 18 days, and the body weight and tumor size were recorded every other day. The protein expression levels of EGFR, p-EGFR, PI3K, p-PI3K, Akt, p-Akt, BRD4, and c-Myc were determined using Western blotting analysis. Hematological and serum biochemical parameters, organ indices, and HE staining results for the heart, liver, spleen, lung, and kidney were analyzed to evaluate the safety of the nanoparticles. GC-NPs loaded with siEGFR and siBRD4 significantly inhibited the expression of EGFR and BRD4 in vitro. The strongest fluorescence signals were observed in the GC-NP group, especially in tumors, indicating the excellent tumor-targeted delivery of GC-NPs we constructed. Tumor growth was significantly inhibited in the GC-NP-treated group, and the expression of EGFR, p-EGFR, PI3K, p-PI3K, Akt, p-Akt, BRD4, and c-Myc in the tumors decreased by 71%, 68%, 61%, 68%, 48%, 58%, 59%, and 74% compared to the control group, respectively. There was no significant change in hematological parameters, biochemical indices, or tissue morphology in GC-NP-treated mice. SiRNA cotargeting EGFR and BRD4 delivered by GALA- and CREKA-modified PEG-SS-PEI had favorable antitumor effects in vivo toward TNBC with tumor-targeting efficacy and good biocompatibility.

X chromosome escapee genes are involved in ischemic sexual dimorphism through epigenetic modification of inflammatory signals

BACKGROUND

Stroke is a sexually dimorphic disease. Previous studies have found that young females are protected against ischemia compared to males, partially due to the protective effect of ovarian hormones, particularly estrogen (E2). However, there are also genetic and epigenetic effects of X chromosome dosage that contribute to stroke sensitivity and neuroinflammation after injury, especially in the aged. Genes that escape from X chromosome inactivation (XCI) contribute to sex-specific phenotypes in many disorders. Kdm5c and kdm6a are X escapee genes that demethylate H3K4me3 and H3K27me3, respectively. We hypothesized that the two demethylases play critical roles in mediating the stroke sensitivity.

METHODS

To identify the X escapee genes involved in stroke, we performed RNA-seq in flow-sorted microglia from aged male and female wild type (WT) mice subjected to middle cerebral artery occlusion (MCAO). The expression of these genes (kdm5c/kdm6a) were confirmed in four core genotypes (FCG) mice and in post-mortem human stroke brains by immunohistochemistry (IHC), Western blot, and RT-PCR. Chromatin immunoprecipitation (ChIP) assays were conducted to detect DNA levels of inflammatory interferon regulatory factor (IRF) 4/5 precipitated by histone H3K4 and H3K27 antibodies. Manipulation of kdm5c/kdm6a expression with siRNA or lentivirus was performed in microglial culture, to determine downstream pathways and examine the regulatory roles in inflammatory cytokine production.

RESULTS

Kdm5c and kdm6a mRNA levels were significantly higher in aged WT female vs. male microglia, and the sex difference also existed in ischemic brains from FCG mice and human stroke patients. The ChIP assay showed the IRF 4/5 had higher binding levels to demethylated H3K4 or H3K27, respectively, in female vs. male ischemic microglia. Knockdown or over expression of kdm5c/kdm6a with siRNA or lentivirus altered the methylation of H3K4 or H3K27 at the IRF4/5 genes, which in turn, impacted the production of inflammatory cytokines.

CONCLUSIONS

The KDM-Histone-IRF pathways are suggested to mediate sex differences in cerebral ischemia. Epigenetic modification of stroke-related genes constitutes an important mechanism underlying the ischemic sexual dimorphism.

Multi-Modal Characterization of Monocytes in Idiopathic Pulmonary Fibrosis Reveals a Primed Type I Interferon Immune Phenotype

Idiopathic pulmonary fibrosis (IPF) is the most severe form of chronic lung fibrosis. Circulating monocytes have been implicated in immune pathology in IPF but their phenotype is unknown. In this work, we determined the immune phenotype of monocytes in IPF using multi-colour flow cytometry, RNA sequencing and corresponding serum factors, and mapped the main findings to amount of lung fibrosis and single cell transcriptomic landscape of myeloid cells in IPF lungs. We show that monocytes from IPF patients displayed increased expression of CD64 (FcγR1) which correlated with amount of lung fibrosis, and an amplified type I IFN response ex vivo. These were accompanied by markedly raised CSF-1 levels, IL-6, and CCL-2 in serum of IPF patients. Interrogation of single cell transcriptomic data from human IPF lungs revealed increased proportion of CD64hi monocytes and "transitional macrophages" with higher expression of CCL-2 and type I IFN genes. Our study shows that monocytes in IPF patients are phenotypically distinct from age-matched controls, with a primed type I IFN pathway that may contribute to driving chronic inflammation and fibrosis. These findings strengthen the potential role of monocytes in the pathogenesis of IPF.

ARV-825-induced BRD4 protein degradation as a therapy for thyroid carcinoma

Bromodomain-containing protein 4 (BRD4) is overexpressed in thyroid carcinoma, represents as an important therapeutic target. ARV-825 is a novel cereblon-based PROTAC (Proteolysis Targeting Chsimera) compound. It can induce fast and sustained BRD4 protein degradation. Its potential effect in human thyroid carcinoma cells was studied here. In TPC-1 cells and primary human thyroid carcinoma cells, ARV-825 potently inhibited cell viability, proliferation and migration. Furthermore, ARV-825 induced robust apoptosis activation in the thyroid carcinoma cells. ARV-825 induced BRD4 protein degradation and downregulation of its targets, including c-Myc, Bcl-xL and cyclin D1 in thyroid carcinoma cells. It was significantly more potent in inhibiting thyroid carcinoma cells than the known small molecule BRD4 inhibitors. In vivo studies demonstrated that ARV-825 oral administration potently suppressed TPC-1 xenograft tumor growth in severe combined immunodeficient mice. BRD4 protein degradation as well as c-Myc, Bcl-xL and cyclin D1 downregulation were detected in ARV-825-treated TPC-1 tumor tissues. Taken together, ARV-825 induces BRD4 protein degradation and inhibits thyroid carcinoma cell growth in vitro and in vivo.

SF2523 inhibits human chondrosarcoma cell growth in vitro and in vivo

Developing novel therapeutic agents against chondrosarcoma is important. SF2523 is a PI3K-Akt-mTOR and bromodomain-containing protein 4 (BRD4) dual inhibitor. Its activity in human chondrosarcoma cells is tested. Our results show that SF2523 potently inhibited survival, proliferation and migration, and induced apoptosis activation in SW1353 cells and primary human chondrosarcoma cells. The dual inhibitor was yet non-cytotoxic to the primary human osteoblasts and OB-6 osteoblastic cells. SF2523 blocked Akt-mTOR activation and downregulated BRD4-regulated genes (Bcl-2 and c-Myc) in chondrosarcoma cells. It was more efficient in killing chondrosarcoma cells than other established PI3K-Akt-mTOR and BRD4 inhibitors, including JQ1, perifosine and OSI-027. In vivo, intraperitoneal injection of SF2523 (30 mg/kg) potently inhibited subcutaneous SW1353 xenograft tumor growth in severe combined immunodeficient mice. Akt-mTOR inhibition as well as Bcl-2 and c-Myc downregulation were detected in SF2523-treated SW1353 tumor tissues. In conclusion, targeting PI3K-Akt-mTOR and BRD4 by SF2523 potently inhibited chondrosarcoma cell growth in vitro and in vivo.

The C-Terminal Transactivation Domain of STAT1 Has a Gene-Specific Role in Transactivation and Cofactor Recruitment

STAT1 has a key role in the regulation of innate and adaptive immunity by inducing transcriptional changes in response to cytokines, such as all types of interferons (IFN). STAT1 exist as two splice isoforms, which differ in regard to the C-terminal transactivation domain (TAD). STAT1β lacks the C-terminal TAD and has been previously reported to be a weaker transcriptional activator than STAT1α, although this was strongly dependent on the target gene. The mechanism of this context-dependent effects remained unclear. By using macrophages from mice that only express STAT1β, we investigated the role of the C-terminal TAD during the distinct steps of transcriptional activation of selected target genes in response to IFNγ. We show that the STAT1 C-terminal TAD is absolutely required for the recruitment of RNA polymerase II (Pol II) and for the establishment of active histone marks at the class II major histocompatibility complex transactivator (CIIta) promoter IV, whereas it is dispensable for histone acetylation at the guanylate binding protein 2 (Gbp2) promoter but required for an efficient recruitment of Pol II, which correlated with a strongly reduced, but not absent, transcriptional activity. IFNγ-induced expression of Irf7, which is mediated by STAT1 in complex with STAT2 and IRF9, did not rely on the presence of the C-terminal TAD of STAT1. Moreover, we show for the first time that the STAT1 C-terminal TAD is required for an efficient recruitment of components of the core Mediator complex to the IFN regulatory factor (Irf) 1 and Irf8 promoters, which both harbor an open chromatin state under basal conditions. Our study identified novel functions of the STAT1 C-terminal TAD in transcriptional activation and provides mechanistic explanations for the gene-specific transcriptional activity of STAT1β.

microRNA-608 inhibits human hepatocellular carcinoma cell proliferation via targeting the BET family protein BRD4

Over-expression of the bromodomain and extraterminal (BET) family protein BRD4 is associated with hepatocellular carcinoma (HCC) progression. In the present study, we indentified a novel putative anti-BRD4 microRNA: microRNA-608 ("miR-608"). In HepG2 cells and primary human HCC cells, over-expression of miR-608, using a lentiviral construct, induced BRD4 downregulation and proliferation inhibition. Conversely, transfection of the miR-608 inhibitor increased BRD4 expression to promote HepG2 cell proliferation. Our results suggest that BRD4 is the primary target gene of miR-608 in HepG2 cells. shRNA-mediated knockdown or CRSIPR/Cas9-mediated knockout of BRD4 mimicked and overtook miR-608's actions in HepG2 cells. Furthermore, introduction of a 3'-untranslated region (3'-UTR) mutant BRD4 (UTR-A1718G) blocked miR-608-induced c-Myc downregulation and proliferation inhibition in HepG2 cells. In vivo, HepG2 xenograft tumor growth was significantly inhibited after expressing miR-608 or BRD4 CRSIPR/Cas9-KO construct. Importantly, BRD4 mRNA was upregulated in human HCC tissues, which was correlated with downregulation of miR-608. Together, we conclude that miR-608 inhibits HCC cell proliferation possibly via targeting BET family protein BRD4.

AZD5153, a novel BRD4 inhibitor, suppresses human thyroid carcinoma cell growth in vitro and in vivo

The development of novel anti-papillary thyroid carcinoma agents is urgent. AZD5153 is a novel and specific Bromodomain-containing protein 4 (BRD4) inhibitor. Here, we show that AZD5153 dose-dependently inhibited survival, proliferation and cell cycle progression in TPC-1 cells and primary human thyroid carcinoma cells. Yet, it was non-cytotoxic to the primary thyroid epithelial cells. AZD5153 induced caspase-3/-9 and apoptosis activation in TPC-1 cells and primary cancer cells. Its cytotoxicity in TPC-1 cells was significantly attenuated with co-treatment of the caspase inhibitors. BRD4 expression was elevated in TPC-1 and primary human thyroid carcinoma cells, but was low in the thyroid epithelial cells. BRD4-regulated proteins, including c-Myc, Bcl-2 and cyclin D1, were significantly downregulated following AZD5153 treatment in TPC-1 and primary cancer cells. In vivo, oral administration of AZD5153 at well-tolerated doses significantly inhibited TPC-1 xenograft growth in severe combined immunodeficient (SCID) mice. BRD4-dependent proteins, Myc, Bcl-2 and cyclin D1, were also downregulated in AZD5153-treated tumor tissues. Collectively, the results suggest that targeting BRD4 by AZD5153 inhibits human thyroid carcinoma cell growth in vitro and in vivo.

Bromodomain-containing proteins in prostate cancer

Several oncogenic factors have been involved in prostate cancer progression. However, therapeutic approaches still focus on suppression of androgen receptor (AR) signaling. In fact, whereas the full-length AR incorporates a ligand-binding domain, which has become a drug target for competitive inhibitors, other transcription factors often do not have tractable binding pockets that aid drug development. Consequently drug development efforts have turned to transcription co-regulators, often chromatin-modifying enzymes or factors that bind to epigenetic modifications to chromatin. Bromodomain (BRD)-containing proteins fall into the latter category and significant progress has been made in developing small molecule inhibitors that target a particular subgroup of BRD-containing proteins known as the Bromodomain and extra-terminal (BET) family proteins. These inhibitors have proven particularly effective in inactivating c-Myc in lymphoma but more recently members of the BET family have also been identified as AR-interacting proteins raising the prospect of using these inhibitors as an alternative strategy for targeting AR-driven cancers. In this review we will provide an overview of BRD-containing proteins and the potential for exploiting them as biomarkers and drug targets in prostate cancer.

Dual inhibition of BRD4 and PI3K by SF2523 suppresses human prostate cancer cell growth in vitro and in vivo

Bromodomain-containing protein 4 (BRD4) and phosphatidylinositol 3-kinase (PI3K) are both key oncogenic proteins in human prostate cancer. In the current study, we examined the anti-prostate cancer cell activity by SF2523, a BRD4 and PI3K dual inhibitor. We showed that SF2523 potently inhibited survival and proliferation of the primary human prostate cancer cells. SF2523 induced profound apoptosis activation in prostate cancer cells. The dual inhibitor was yet non-cytotoxic to the prostate epithelial cells. At the molecular level, SF2523 downregulated BRD4-regulated genes (cyclin D1, c-Myc and androgen receptor) and almost blocked AKT-S6K1 activation in prostate cancer cells. In vivo, SF2523 intraperitoneal administration at the well-tolerated dose inhibited human prostate cancer xenograft growth in severe combined immunodeficient (SCID) mice. BRD4-regulated genes (cyclin D1, c-Myc and androgen receptor) and AKT-S6K1 activation were inhibited in SF2523-treated tumors. Together, dual inhibition of BRD4 and PI3K by SF2523 suppresses human prostate cancer cell growth in vitro and in vivo.

Dual inhibition of BRD4 and PI3K-AKT by SF2523 suppresses human renal cell carcinoma cell growth

Bromodomain-containing protein 4 (BRD4) and PI3K-AKT are both important for renal cell carcinoma (RCC) development and progression. SF2523 is a BRD4 and PI3K-AKT dual inhibitor. The present study demonstrated that SF2523 was cytotoxic and anti-proliferative to established RCC cell lines (786-O and A498) and primary human RCC cells. SF2523 induced activation of caspase and apoptosis in RCC cells. Further, SF2523 disrupted RCC cell cycle progression and inhibited cell migration in vitro. At the signaling level, SF2523 in-activated PI3K-AKT-mTOR, and downregulated BRD4-dependent proteins, Bcl-2 and Myc, in RCC cells. Remarkably, SF2523 was more efficient than Wortmannin (the PI3K inhibitor) and JQ1 (the BRD4 specific inhibitor) in killing RCC cells. In vivo, SF2523 administration at well-tolerated doses suppressed 786-O xenograft tumor growth in severe combined immunodeficient (SCID) mice. Together, our results suggest that concurrent blockage of BRD4 and PI3K-AKT signalings by SF2523 efficiently inhibits RCC cell growth in vitro and in vivo.