Bromodomain-Containing Protein 4: A Druggable Target

Inhibition of spinal BRD4 alleviates pyroptosis and M1 microglia polarization via STING-IRF3 pathway in morphine-tolerant rats

BACKGROUND

Morphine tolerance has been a challenging medical issue. Neuroinflammation is considered as a critical mechanism for the development of morphine tolerance. Bromodomain-containing protein 4 (BRD4), a key regulator in cell damage and inflammation, participates in the development of chronic pain. However, whether BRD4 is involved in morphine tolerance and the underlying mechanisms remain unknown.

METHODS

The morphine-tolerant rat model was established by intrathecal administration of morphine twice daily for 7 days. Behavior test was assessed by a tail-flick latency test. The roles of BRD4, pyroptosis, microglia polarization and related signaling pathways in morphine tolerance were elucidated by Western blot, real-time quantitative polymerase chain reaction, and immunofluorescence.

RESULTS

Repeated morphine administration upregulated BRD4 level, induced pyroptosis, and promoted microglia M1-polarization in spinal cord, accompanied by the release of proinflammatory cytokines, such as TNF-α and IL-1β. JQ-1, a BRD4 antagonist, alleviated the development of morphine tolerance, diminished pyroptosis and induced the switch of microglia from M1 to M2 phenotype. Mechanistically, stimulator of interferon gene (STING)- interferon regulatory factor 3 (IRF3) pathway was activated and the protective effect of JQ-1 against morphine tolerance was at least partially mediated by inhibition of STING-IRF3 pathway.

CONCLUSION

This study demonstrated for the first time that spinal BRD4 contributes to pyroptosis and switch of microglia polarization via STING-IRF3 signaling pathway during the development of morphine tolerance, which extend the understanding of the neuroinflammation mechanism of morphine tolerance and provide an alternative strategy for the precaution against of this medical condition.

Hydrogen Peroxide-Inducible PROTACs for Targeted Protein Degradation in Cancer Cells

Proteolysis-targeting chimeras (PROTACs) provide a powerful technique to degrade targeted proteins utilizing the cellular ubiquitin-proteasome system. The major concern is the host toxicity resulting from their poor selectivity. Inducible PROTACs responding to exogenous stimulus, such as light, improve their specificity, but it is difficult for photo-activation in deep tissues. Herein, we develop H2 O2 -inducible PROTAC precursors 2/5, which can be activated by endogenous H2 O2 in cancer cells to release the active PROTACs 1/4 to effectively degrade targeted proteins. This results in the intended cytotoxicity towards cancer cells while targeted protein in normal cells remains almost unaffected. The higher Bromodomain-containing protein 4 (BRD4) degradation activity and cytotoxicity of 2 towards cancer cells is mainly due to the higher endogenous concentration of H2 O2 in cancer cells (A549 and H1299), characterized by H2 O2 -responsive fluorescence probe 3. Western blot assays and cytotoxicity experiments demonstrate that 2 degrades BRD4 more effectively and is more cytotoxic in H2 O2 -rich cancer cells than in H2 O2 -deficient normal cells. This method is also extended to estrogen receptor (ER)-PROTAC precursor 5, showing H2 O2 -dependent ER degradation ability. Thus, we establish a novel strategy to induce targeted protein degradation in a H2 O2 -dependent way, which has the potential to improve the selectivity of PROTACs.

Pursuing functional biomarkers in complex disease: Focus on pulmonary arterial hypertension

A major gap in diagnosis, classification, risk stratification, and prediction of therapeutic response exists in pulmonary arterial hypertension (PAH), driven in part by a lack of functional biomarkers that are also disease-specific. In this regard, leveraging big data-omics analyses using innovative approaches that integrate network medicine and machine learning correlated with clinically useful indices or risk stratification scores is an approach well-positioned to advance PAH precision medicine. For example, machine learning applied to a panel of 48 cytokines, chemokines, and growth factors could prognosticate PAH patients with immune-dominant subphenotypes at elevated or low-risk for mortality. Here, we discuss strengths and weaknesses of the most current studies evaluating omics-derived biomarkers in PAH. Progress in this field is offset by studies with small sample size, pervasive limitations in bioinformatics, and lack of standardized methods for data processing and interpretation. Future success in this field, in turn, is likely to hinge on mechanistic validation of data outputs in order to couple functional biomarker data with target-specific therapeutics in clinical practice.

High Expression Level of BRD4 Is Associated with a Poor Prognosis and Immune Infiltration in Esophageal Squamous Cell Carcinoma

BACKGROUND

Bromodomain-containing protein 4 (BRD4) is a reader of histone acetylation and is associated with a variety of diseases.

AIM

To investigate the expression level of BRD4 in esophageal squamous cell carcinoma (ESCC), its prognostic value and its relationship with immune infiltration.

METHODS

The study included 94 ESCC patients from The Cancer Genome Atlas (TCGA) database and 179 ESCC patients from Affiliated Hospital 2 of Nantong University. The expression levels of proteins in tissue microarray were detected by immunohistochemistry. The prognostic factors were analyzed by Kaplan-Meier curve and univariate and multivariate cox regression. The ESTIMATE website was used to calculate the stromal, immune and ESTIMATE score. CIBERSORT was used to calculate the abundance of immune infiltrates. Spearman and Phi coefficient were used for correlation analysis. The TIDE algorithm was used to predict treatment response to immune checkpoint blockade.

RESULTS

BRD4 is up-regulated in ESCC, and high BRD4 expression level is associated with poor prognosis and adverse clinicopathological features. In addition, the monocyte count, systemic inflammatory-immunologic index, platelet-lymphocyte ratio, and monocyte-lymphocyte ratio in the BRD4 high expression level group were higher than in the low expression level group. Finally, we found that BRD4 expression level correlated with immune infiltration and that it was inversely correlated with infiltration of CD8 + T cells. Higher TIDE scores in the BRD4 high expression group than in the low expression group.

CONCLUSION

BRD4 is associated with poor prognosis and immune infiltration in ESCC, and may be a potential biomarker for prognosis and immunotherapy application.

Downregulation of BRD4 attenuates high glucose-induced damage of trophoblast cells by inhibiting activation of AKT/mTOR pathway

It was elucidated that bromodomain-containing protein 4 (BRD4) has involvement with diabetic complication. However, the role and molecular mechanism of BRD4 in gestational diabetes mellitus (GDM) are still unclear. In this study, the mRNA and protein contents of BRD4 in placenta tissues of GDM patients and high glucose (HG)-induced HTR8/SVneo cells were detected by qRT-PCR and western blot assay. CCK-8, EdU staining, flow cytometry as well as western blot were applied for the appraisement of cell viability and apoptosis. Wound healing assay and transwell assay were conducted for the assessment of cell migration and invasion. Oxidative stress and inflammatory factors were detected. Additionally, the contents of AKT/mTOR pathway-related proteins were estimated applying western blot. It was discovered that BRD4 expression was ascended in tissues and HG-induced HTR8/SVneo cells. BRD4 downregulation cut down the contents of p-AKT and p-mTOR but had no effects on the total protein levels of AKT or mTOR in HG-induced HTR8/SVneo cells. BRD4 depletion promoted cell viability, enhanced proliferative capability, and reduced cell apoptotic level. Moreover, BRD4 depletion facilitated cell migrative and invasive capabilities, and repressed the oxidative stress as well as inflammatory damage in HG-induced HTR8/SVneo cells. The activation of Akt reversed the protective impacts of BRD4 depletion on HG-induced HTR8/SVneo cells. To sum up, BRD4 silencing may alleviate HG-induced HTR8/SVneo cell damage through the inhibition of the AKT/mTOR pathway.

Discovery of a Novel Aminocyclopropenone Compound That Inhibits BRD4-Driven Nucleoporin NUP210 Expression and Attenuates Colorectal Cancer Growth

Epigenetic deregulation plays an essential role in colorectal cancer progression. Bromodomains are epigenetic “readers” of histone acetylation. Bromodomain-containing protein 4 (BRD4) plays a pivotal role in transcriptional regulation and is a feasible drug target in cancer cells. Disease-specific elevation of nucleoporin, a component of the nuclear pore complex (NPC), is a determinant of cancer malignancy, but BRD4-driven changes of NPC composition remain poorly understood. Here, we developed novel aminocyclopropenones and investigated their biological effects on cancer cell growth and BRD4 functions. Among 21 compounds developed here, we identified aminocyclopropenone 1n (ACP-1n) with the strongest inhibitory effects on the growth of the cancer cell line HCT116. ACP-1n blocked BRD4 functions by preventing its phase separation ability both in vitro and in vivo, attenuating the expression levels of BRD4-driven MYC. Notably, ACP-1n significantly reduced the nuclear size with concomitant suppression of the level of the NPC protein nucleoporin NUP210. Furthermore, NUP210 is in a BRD4-dependent manner and silencing of NUP210 was sufficient to decrease nucleus size and cellular growth. In conclusion, our findings highlighted an aminocyclopropenone compound as a novel therapeutic drug blocking BRD4 assembly, thereby preventing BRD4-driven oncogenic functions in cancer cells. This study facilitates the development of the next generation of effective and potent inhibitors of epigenetic bromodomains and extra-terminal (BET) protein family.

Expression of Phosphorylated BRD4 Is Markedly Associated with the Activation Status of the PP2A Pathway and Shows a Strong Prognostic Value in Triple Negative Breast Cancer Patients

Simple Summary

The use of BRD4 inhibitors has emerged as a novel therapeutic approach in a wide variety of tumors including the triple negative breast cancer. Moreover, PP2A has been proposed as the phosphatase involved in regulating BRD4 phosphorylation and stabilization. Our aim was to evaluate for the first time the clinical impact of BRD4 phosphorylation in triple negative breast cancer patients and as well as its potential linking with the PP2A activation status in this disease. Our findings are special relevant since they suggest the prognostic value of BRD4 phosphorylation levels, and the potential clinical usefulness of PP2A inhibition markers to anticipate response to BRD4 inhibitors.

Abstract

The bromodomain-containing protein 4 (BRD4), a member of the bromodomain and extra-terminal domain (BET) protein family, has emerged in the last years as a promising molecular target in many tumors including breast cancer. The triple negative breast cancer (TNBC) represents the molecular subtype with the worst prognosis and a current therapeutic challenge, and TNBC cells have been reported to show a preferential sensitivity to BET inhibitors. Interestingly, BRD4 phosphorylation (pBRD4) was found as an alteration that confers resistance to BET inhibition and PP2A proposed as the phosphatase responsible to regulate pBRD4 levels. However, the potential clinical significance of pBRD4, as well as its potential correlation with the PP2A pathway in TNBC, remains to be investigated. Here, we evaluated the expression levels of pBRD4 in a series of 132 TNBC patients. We found high pBRD4 levels in 34.1% of cases (45/132), and this alteration was found to be associated with the development of patient recurrences (p = 0.007). Interestingly, BRD4 hyperphosphorylation predicted significantly shorter overall (p < 0.001) and event-free survival (p < 0.001). Moreover, multivariate analyses were performed to confirm its independent prognostic impact in our cohort. In conclusion, our findings show that BRD4 hyperphosphorylation is an alteration associated with PP2A inhibition that defines a subgroup of TNBC patients with unfavorable prognosis, suggesting the potential clinical and therapeutic usefulness of the PP2A/BRD4 axis as a novel molecular target to overcome resistance to treatments based on BRD4 inhibition.

PROTACs: A Hope for Breast Cancer Patients?

BACKGROUND

Breast Cancer (BC) is the most widely recognized disease in women. A massive number of women are diagnosed with breast cancer and many lost their lives every year. Cancer is the subsequent driving reason for dying, giving rise to it one of the current medication's most prominent difficulties.

OBJECTIVES

The main objective of the study is to examine and explore novel therapy (PROTAC) and its effectiveness against breast cancer.

METHODS

The literature search was done across Medline, Cochrane, ScienceDirect, Wiley Online, Google Scholar, PubMed, Bentham Sciences from 2001 to 2020. The articles were collected; screened, segregated, and selected papers were included for writing the review article.

RESULTS AND CONCLUSION

A novel innovation emerged around two decades ago that has great potential to not only overcome the limitations but also can provide future direction for the treatment of many diseases which has presently not many therapeutic options available and regarded as incurable with traditional techniques; that innovation is called PROTAC (Proteolysis Targeting Chimera) and able to efficaciously ubiquitinate and debase cancer encouraging proteins by noncovalent interaction. PROTACs are constituted of two active regions isolated by a linker and equipped for eliminating explicit undesirable protein. It is empowering greater sensitivity to "drug-resistant targets" as well as a more prominent opportunity to influence non-enzymatic function. PROTACs have been demonstrated to show better target selectivity contrasted with traditional small-molecule inhibitors. So far, the most investigation into PROTACs possesses particularly concentrated on applications to cancer treatment including breast cancer, the treatment of different ailments may profit from this blossoming innovation.

Targeting Epigenetic 'Readers' with Natural Compounds for Cancer Interception

Natural compounds from diverse sources, including botanicals and commonly consumed foods and beverages, exert beneficial health effects via mechanisms that impact the epigenome and gene expression during disease pathogenesis. By targeting the so-called epigenetic 'readers', 'writers', and 'erasers', dietary phytochemicals can reverse abnormal epigenome signatures in cancer cells and preneoplastic stages. Thus, such agents provide avenues for cancer interception via prevention or treatment/therapeutic strategies. To date, much of the focus on dietary agents has been directed towards writers (e.g., histone acetyltransferases) and erasers (e.g., histone deacetylases), with less attention given to epigenetic readers (e.g., BRD proteins). The drug JQ1 was developed as a prototype epigenetic reader inhibitor, selectively targeting members of the bromodomain and extraterminal domain (BET) family, such as BRD4. Clinical trials with JQ1 as a single agent, or in combination with standard of care therapy, revealed antitumor efficacy but not without toxicity or resistance. In pursuit of second-generation epigenetic reader inhibitors, attention has shifted to natural sources, including dietary agents that might be repurposed as 'JQ1-like' bioactives. This review summarizes the current status of nascent research activity focused on natural compounds as inhibitors of BET and other epigenetic 'reader' proteins, with a perspective on future directions and opportunities.