Safety, pharmacokinetic, pharmacodynamic and clinical activity of molibresib for the treatment of nuclear protein of the testis carcinoma and other cancers: Results of a Phase I/II open-label, dose escalation study

Epigenetics: Mechanisms, potential roles, and therapeutic strategies in cancer progression

Mutations or abnormal expression of oncogenes and tumor suppressor genes are known to cause cancer. Recent studies have shown that epigenetic modifications are key drivers of cancer development and progression. Nevertheless, the mechanistic role of epigenetic dysregulation in the tumor microenvironment is not fully understood. Here, we reviewed the role of epigenetic modifications of cancer cells and non-cancer cells in the tumor microenvironment and recent research advances in cancer epigenetic drugs. In addition, we discussed the great potential of epigenetic combination therapies in the clinical treatment of cancer. However, there are still some challenges in the field of cancer epigenetics, such as epigenetic tumor heterogeneity, epigenetic drug heterogeneity, and crosstalk between epigenetics, proteomics, metabolomics, and other omics, which may be the focus and difficulty of cancer treatment in the future. In conclusion, epigenetic modifications in the tumor microenvironment are essential for future epigenetic drug development and the comprehensive treatment of cancer. Epigenetic combination therapy may be a novel strategy for the future clinical treatment of cancer.

Structure- and Property-Based Optimization of Efficient Pan-Bromodomain and Extra Terminal Inhibitors to Identify Oral and Intravenous Candidate I-BET787

The bromodomain and extra terminal (BET) family of bromodomain-containing proteins are important epigenetic regulators that elicit their effect through binding histone tail N-acetyl lysine (KAc) post-translational modifications. Recognition of such markers has been implicated in a range of oncology and immune diseases and, as such, small-molecule inhibition of the BET family bromodomain-KAc protein-protein interaction has received significant interest as a therapeutic strategy, with several potential medicines under clinical evaluation. This work describes the structure- and property-based optimization of a ligand and lipophilic efficient pan-BET bromodomain inhibitor series to deliver candidate I-BET787 (70) that demonstrates efficacy in a mouse model of inflammation and suitable properties for both oral and intravenous (IV) administration. This focused two-phase explore-exploit medicinal chemistry effort delivered the candidate molecule in 3 months with less than 100 final compounds synthesized.

Therapeutic targeting of BET bromodomain and other epigenetic acetylrecognition domain-containing factors

Development of cancer therapies targeting chromatin modifiers and transcriptional regulatory factors is rapidly expanding to include new targets and novel targeting strategies. At the same time, basic molecular research continues to refine our understanding of the epigenetic mechanisms regulating transcription, gene expression, and oncogenesis. This mini-review focuses on cancer therapies targeting the chromatin-associated factors that recognize histone lysine acetylation. Recently reported safety and efficacy are discussed for inhibitors targeting the bromodomains of bromodomain and extraterminal domain (BET) family proteins. In light of recent results indicating that the transcriptional regulator BRD4-PTEFb can function independently of BRD4's bromodomains, the clinical trial performance of these BET inhibitors is placed in a broader context of existing and potential strategies for targeting BRD4-PTEFb. Recently developed therapies targeting bromodomain-containing factors within the SWI/SNF (BAF) family of chromatin remodeling complexes are discussed, as is the potential for targeting the bromodomain-containing transcription factor TAF1 and the YEATS acetylrecognition domain-containing factor GAS41. Recent findings regarding the selectivity and combinatorial specificity of acetylrecognition are highlighted. In conclusion, the potential for further development is discussed with a focus on proximity-based therapies targeting this class of epigenetic factors.

Multimodal Therapy Approaches for NUT Carcinoma by Dual Combination of Oncolytic Virus Talimogene Laherparepvec with Small Molecule Inhibitors

NUT (nuclear-protein-in-testis) carcinoma (NC) is a highly aggressive tumor disease. Given that current treatment regimens offer a median survival of six months only, it is likely that this type of tumor requires an extended multimodal treatment approach to improve prognosis. In an earlier case report, we could show that an oncolytic herpes simplex virus (T-VEC) is functional in NC patients. To identify further combination partners for T-VEC, we have investigated the anti-tumoral effects of T-VEC and five different small molecule inhibitors (SMIs) alone and in combination in human NC cell lines. Dual combinations were found to result in higher rates of tumor cell reductions when compared to the respective monotherapy as demonstrated by viability assays and real-time tumor cell growth monitoring. Interestingly, we found that the combination of T-VEC with SMIs resulted in both stronger and earlier reductions in the expression of c-Myc, a main driver of NC cell proliferation, when compared to T-VEC monotherapy. These results indicate the great potential of combinatorial therapies using oncolytic viruses and SMIs to control the highly aggressive behavior of NC cancers and probably will pave the way for innovative multimodal clinical studies in the near future.

Cotargeting CDK4/6 and BRD4 Promotes Senescence and Ferroptosis Sensitivity in Cancer

Cyclin-dependent kinase 4/6 (CDK4/6) inhibitors are approved for breast cancer treatment and show activity against other malignancies, including KRAS-mutant non-small cell lung cancer (NSCLC). However, the clinical efficacy of CDK4/6 inhibitors is limited due to frequent drug resistance and their largely cytostatic effects. Through a genome-wide cDNA screen, we identified that bromodomain-containing protein 4 (BRD4) overexpression conferred resistance to the CDK4/6 inhibitor palbociclib in KRAS-mutant NSCLC cells. Inhibition of BRD4, either by RNA interference or small-molecule inhibitors, synergized with palbociclib to induce senescence in NSCLC cells and tumors, and the combination prolonged survival in a KRAS-mutant NSCLC mouse model. Mechanistically, BRD4-inhibition enhanced cell-cycle arrest and reactive oxygen species (ROS) accumulation, both of which are necessary for senescence induction; this in turn elevated GPX4, a peroxidase that suppresses ROS-triggered ferroptosis. Consequently, GPX4 inhibitor treatment selectively induced ferroptotic cell death in the senescent cancer cells, resulting in tumor regression. Cotargeting CDK4/6 and BRD4 also promoted senescence and ferroptosis vulnerability in pancreatic and breast cancer cells. Together, these findings reveal therapeutic vulnerabilities and effective combinations to enhance the clinical utility of CDK4/6 inhibitors.

SIGNIFICANCE

The combination of cytostatic CDK4/6 and BRD4 inhibitors induces senescent cancer cells that are primed for activation of ferroptotic cell death by targeting GPX4, providing an effective strategy for treating cancer.

Pathogenic role of super-enhancers as potential therapeutic targets in lung cancer

Lung cancer is still one of the deadliest malignancies today, and most patients with advanced lung cancer pass away from disease progression that is uncontrollable by medications. Super-enhancers (SEs) are large clusters of enhancers in the genome's non-coding sequences that actively trigger transcription. Although SEs have just been identified over the past 10 years, their intricate structure and crucial role in determining cell identity and promoting tumorigenesis and progression are increasingly coming to light. Here, we review the structural composition of SEs, the auto-regulatory circuits, the control mechanisms of downstream genes and pathways, and the characterization of subgroups classified according to SEs in lung cancer. Additionally, we discuss the therapeutic targets, several small-molecule inhibitors, and available treatment options for SEs in lung cancer. Combination therapies have demonstrated considerable advantages in preclinical models, and we anticipate that these drugs will soon enter clinical studies and benefit patients.

Construction of a gene model related to the prognosis of patients with gastric cancer receiving immunotherapy and exploration of COX7A1 gene function

BACKGROUND

GC is a highly heterogeneous tumor with different responses to immunotherapy, and the positive response depends on the unique interaction between the tumor and the tumor microenvironment (TME). However, the currently available methods for prognostic prediction are not satisfactory. Therefore, this study aims to construct a novel model that integrates relevant gene sets to predict the clinical efficacy of immunotherapy and the prognosis of GC patients based on machine learning.

METHODS

Seven GC datasets were collected from the Gene Expression Omnibus (GEO) database, The Cancer Genome Atlas (TCGA) database and literature sources. Based on the immunotherapy cohort, we first obtained a list of immunotherapy related genes through differential expression analysis. Then, Cox regression analysis was applied to divide these genes with prognostic significancy into protective and risky types. Then, the Single Sample Gene Set Enrichment Analysis (ssGSEA) algorithm was used to score the two categories of gene sets separately, and the scores differences between the two gene sets were used as the basis for constructing the prognostic model. Subsequently, Weighted Correlation Network Analysis (WGCNA) and Cytoscape were applied to further screen the gene sets of the constructed model, and finally COX7A1 was selected for the exploration and prediction of the relationship between the clinical efficacy of immunotherapy for GC. The correlation between COX7A1 and immune cell infiltration, drug sensitivity scoring, and immunohistochemical staining were performed to initially understand the potential role of COX7A1 in the development and progression of GC. Finally, the differential expression of COX7A1 was verified in those GC patients receiving immunotherapy.

RESULTS

First, 47 protective genes and 408 risky genes were obtained, and the ssGSEA algorithm was applied for model construction, showing good prognostic discrimination ability. In addition, the patients with high model scores showed higher TMB and MSI levels, and lower tumor heterogeneity scores. Then, it is found that the COX7A1 expressions in GC tissues were significantly lower than those in their corresponding paracancerous tissues. Meanwhile, the patients with high COX7A1 expression showed higher probability of cancer invasion, worse clinical efficacy of immunotherapy, worse overall survival (OS) and worse disease-free survival (DFS).

CONCLUSIONS

The ssGSEA score we constructed can serve as a biomarker for GC patients and provide important guidance for individualized treatment. In addition, the COX7A1 gene can accurately distinguish the prognosis of GC patients and predict the clinical efficacy of immunotherapy for GC patients.

NUT carcinoma in pediatric patients: Characteristics, therapeutic regimens, and outcomes of 11 cases registered with the German Registry for Rare Pediatric Tumors (STEP)

BACKGROUND AND AIMS

Nuclear protein of the testis (NUT) carcinoma (NC) is a rare and highly aggressive tumor defined by the presence of a somatic NUTM1 rearrangement, occurring mainly in adolescents and young adults. We analyzed the clinical and biological features of German pediatric patients (≤18 years) with NC.

METHODS

This study describes the characteristics and outcome of 11 children with NC registered in the German Registry for Rare Pediatric Tumors (STEP).

RESULTS

Eleven patients with a median age of 13.2 years (range 6.6-17.8) were analyzed. Malignant misdiagnoses were made in three patients. Thoracic/mediastinal tumors were found to be the primary in six patients, head/neck in four cases; one patient had multifocal tumor with an unknown primary. All patients presented with regional lymph node involvement, eight patients (72.7%) with distant metastases. Seven patients underwent surgery, eight radiotherapy with curative intent; polychemotherapy was administered in all patients. Novel treatment strategies including immunotherapy, targeted therapies, and virotherapy were applied in three patients. Median event-free survival and overall survival were 1.5 and 6.5 months, respectively.

CONCLUSIONS

Every undifferentiated or poorly differentiated carcinoma should undergo testing for the specific rearrangement of NUTM1, in order to initiate an intense therapeutic regimen as early as possible. As in adults, only few pediatric patients with NC achieve prolonged survival. Thus, novel therapeutic strategies should be included and tested in clinical trials.

Clinical management of NUT carcinoma (NC) in Germany: Analysis of survival, therapy response, tumor markers and tumor genome sequencing in 35 adult patients

NUT carcinomas (NC) are very rare and highly aggressive tumors, molecularly defined by an aberrant gene fusion involving the NUTM1 gene. NCs preferentially arise intrathoracically or in the head and neck region, having a highly adverse prognosis with almost no long-term survivors. Here, we report on a cohort of 35 adult NC patients who were evaluated at University Hospital Tuebingen in an eight year time span, i.e. between 2016 and 2023. Primary objectives were overall survival (OS) and influence of primary tumor locations, fusion gene types and staging on OS. Secondary objectives were patient baseline characteristics, risk factors, tumor markers, treatment decisions and responses to therapy comparing thoracic vs non-thoracic origins. Further, data from tumor genome sequencing were analyzed. In this monocentric German cohort, 54 % of patients had thoracic tumors and 65 % harbored a BRD4-NUTM1 fusion gene. Median OS was 7.5 months, being significantly dependent on primary tumor location and nodal status. Initial misdiagnosis was a problem in 31 % of the cases. Surgery was the first treatment in most patients (46 %) and 80 % were treated with polychemotherapies, showing longer progression free survival (PFS) with ifosfamide-based than with platinum-based regimens. Patients treated with an immune checkpoint inhibitor (ICI) in addition to first-line chemotherapy tended to have longer OS. Initial LDH levels could be identified as a prognostic measure for survival prognosis. Sequencing data highlight aberrant NUTM1 fusion genes as unique tumor driver genes. This is the largest adult European cohort of this orphan tumor disease, showing epidemiologic and molecular features as well as relevant clinical data. Awareness to prevent misdiagnosis, fast contact to a specialized nation-wide center and referral to clinical studies are essential as long-term survival is rarely achieved with any of the current therapeutic regimes.

A Phase I/II Study of GSK525762 Combined with Fulvestrant in Patients with Hormone Receptor-positive/HER2-negative Advanced or Metastatic Breast Cancer

PURPOSE

Endocrine-based therapy is the initial primary treatment option for hormone receptor-positive and human epidermal growth factor receptor 2-negative (HR+/HER2-) metastatic breast cancer (mBC). However, patients eventually experience disease progression due to resistance to endocrine therapy. Molibresib (GSK525762) is a small-molecule inhibitor of bromodomain and extraterminal (BET) family proteins (BRD2, BRD3, BRD4, and BRDT). Preclinical data suggested that the combination of molibresib with endocrine therapy might overcome endocrine resistance. This study aimed to investigate the safety, tolerability, pharmacokinetics, pharmacodynamics, and efficacy [objective response rate (ORR)] of molibresib combined with fulvestrant in women with HR+/HER2- mBC.

PATIENTS AND METHODS

In this phase I/II dose-escalation and dose-expansion study, patients received oral molibresib 60 or 80 mg once daily in combination with intramuscular fulvestrant. Patients enrolled had relapsed/refractory, advanced/metastatic HR+/HER2- breast cancer with disease progression on prior treatment with an aromatase inhibitor, with or without a cyclin-dependent kinase 4/6 inhibitor.

RESULTS

The study included 123 patients. The most common treatment-related adverse events (AE) were nausea (52%), dysgeusia (49%), and fatigue (45%). At a 60-mg dosage of molibresib, >90% of patients experienced treatment-related AE. Grade 3 or 4 treatment-related AE were observed in 47% and 48% of patients treated with molibresib 60 mg and molibresib 80 mg, respectively. The ORR was 13% [95% confidence interval (CI), 8-20], not meeting the 25% threshold for proceeding to phase II. Among 82 patients with detected circulating tumor DNA and clinical outcome at study enrollment, a strong association was observed between the detection of copy-number amplification and poor progression-free survival (HR, 2.89; 95% CI, 1.73-4.83; P < 0.0001).

CONCLUSIONS

Molibresib in combination with fulvestrant did not demonstrate clinically meaningful activity in this study.

Primary pulmonary nuclear protein of the testis midline carcinoma: case report and systematic review with pooled analysis

Nuclear protein of the testis (NUT) midline carcinoma (NMC) is a rare tumor, with particularly low incidence in the lungs, and a correspondingly poor prognosis. To determine the clinicopathological characteristics, outcomes, and prognostic factors of primary pulmonary NMC, a case was reported and a systematic review was performed. Twenty-nine records, including ours, involving 62 cases, were finally included. The median age at diagnosis was 29.5 years. At presentation, the most common symptoms at presentation were cough (47.50%) and chest/back pain (37.50%). In terms of diagnosis, 32.14% of NMC cases were identified through immunohistochemistry (IHC); However, a greater number of cases may be misdiagnosed initially, and ultimately, the diagnosis of NMC was confirmed through a combination of IHC and fluorescence in situ hybridization (FISH). Despite the clinical application of various chemotherapy-based treatments, the actual effectiveness remains unsatisfactory. Furthermore, Cox regression analysis of multiple factors identified male gender and concurrent presence of pleural effusion as indicators of shorter survival time in patients. These results emphasize the importance of increased diagnostic awareness among clinical and pathology practitioners concerning NMC. While there is currently no established standard for treating NMC, a treatment approach combining multiple methods shows promise for future research. Concurrently, clinical and foundational investigations addressing variables such as gender and the presence of pleural effusion may yield valuable insights into the diagnosis and treatment of NMC.

Super-enhancers and the super-enhancer reader BRD4: tumorigenic factors and therapeutic targets

Transcriptional super-enhancers and the BET bromodomain protein BRD4 are emerging as critical drivers of tumorigenesis and therapeutic targets. Characterized by substantial accumulation of histone H3 lysine 27 acetylation (H3K27ac) signals at the loci of cell identity genes and critical oncogenes, super-enhancers are recognized, bound and activated by BRD4, resulting in considerable oncogene over-expression, malignant transformation, cancer cell proliferation, survival, tumor initiation and progression. Small molecule compound BRD4 BD1 and BD2 bromodomain inhibitors block BRD4 binding to super-enhancers, suppress oncogene transcription and expression, reduce cancer cell proliferation and survival, and repress tumor progression in a variety of cancer types. Like other targeted therapy agents, BRD4 inhibitors show moderate anticancer effects on their own, and exert synergistic anticancer effects in vitro and in preclinical models, when combined with other anticancer agents including CDK7 inhibitors, CBP/p300 inhibitors and histone deacetylase inhibitors. More recently, BRD4 BD2 bromodomain selective inhibitors, proteolysis-targeting chimera (PROTAC) BRD4 protein degraders, and dual BRD4 and CBP/p300 bromodomain co-inhibitors have been developed and shown better anticancer efficacy and/or safety profile. Importantly, more than a dozen BRD4 inhibitors have entered clinical trials in patients with cancer of various organ origins. In summary, super-enhancers and their reader BRD4 are critical tumorigenic drivers, and BRD4 BD1 and BD2 bromodomain inhibitors, BRD4 BD2 bromodomain selective inhibitors, PROTAC BRD4 protein degraders, and dual BRD4 and CBP/p300 bromodomain co-inhibitors are promising novel anticancer agents for clinical translation.

The BRD4-NUT Fusion Alone Drives Malignant Transformation of NUT Carcinoma

NUT carcinoma (NC) is an aggressive squamous carcinoma defined by the BRD4-NUT fusion oncoprotein. Routinely effective systemic treatments are unavailable for most NC patients. The lack of an adequate animal model precludes identifying and leveraging cell-extrinsic factors therapeutically in NC. Here, we created a genetically engineered mouse model (GEMM) of NC that forms a Brd4::NUTM1 fusion gene upon tamoxifen induction of Sox2-driven Cre. The model displayed complete disease penetrance, with tumors arising from the squamous epithelium weeks after induction and all mice succumbing to the disease shortly thereafter. Closely resembling human NC (hNC), GEMM tumors (mNC) were poorly differentiated squamous carcinomas with high expression of MYC that metastasized to solid organs and regional lymph nodes. Two GEMM-derived cell lines were developed whose transcriptomic and epigenetic landscapes harbored key features of primary GEMM tumors. Importantly, GEMM tumor and cell line transcriptomes co-classified with those of human NC. BRD4-NUT also blocked differentiation and maintained the growth of mNC as in hNC. Mechanistically, GEMM primary tumors and cell lines formed large histone H3K27ac-enriched domains, termed megadomains, that were invariably associated with the expression of key NC-defining proto-oncogenes, Myc and Trp63. Small-molecule BET bromodomain inhibition (BETi) of mNC induced differentiation and growth arrest and prolonged survival of NC GEMMs, as it does in hNC models. Overall, tumor formation in the NC GEMM is definitive evidence that BRD4-NUT alone can potently drive the malignant transformation of squamous progenitor cells into NC.

SIGNIFICANCE

The development of an immunocompetent model of NUT carcinoma that closely mimics the human disease provides a valuable global resource for mechanistic and preclinical studies to improve treatment of this incurable disease.

Combination Therapies to Improve the Efficacy of Immunotherapy in Triple-negative Breast Cancer

Immune checkpoint inhibition combined with chemotherapy is currently approved as first-line treatment for patients with advanced PD-L1-positive triple-negative breast cancer (TNBC). However, a significant proportion of metastatic TNBC is PD-L1-negative and, in this population, chemotherapy alone largely remains the standard-of-care and novel therapeutic strategies are needed to improve clinical outcomes. Here, we describe a triple combination of anti-PD-L1 immune checkpoint blockade, epigenetic modulation thorough bromodomain and extra-terminal (BET) bromodomain inhibition (BBDI), and chemotherapy with paclitaxel that effectively inhibits both primary and metastatic tumor growth in two different syngeneic murine models of TNBC. Detailed cellular and molecular profiling of tumors from single and combination treatment arms revealed increased T- and B-cell infiltration and macrophage reprogramming from MHCIIlow to a MHCIIhigh phenotype in mice treated with triple combination. Triple combination also had a major impact on gene expression and chromatin profiles shifting cells to a more immunogenic and senescent state. Our results provide strong preclinical evidence to justify clinical testing of BBDI, paclitaxel, and immune checkpoint blockade combination.

First-in-human Study of AZD5153, A Small-molecule Inhibitor of Bromodomain Protein 4, in Patients with Relapsed/Refractory Malignant Solid Tumors and Lymphoma

AZD5153, a reversible, bivalent inhibitor of the bromodomain and extraterminal family protein BRD4, has preclinical activity in multiple tumors. This first-in-human, phase I study investigated AZD5153 alone or with olaparib in patients with relapsed/refractory solid tumors or lymphoma. Adults with relapsed tumors intolerant of, or refractory to, prior therapies received escalating doses of oral AZD5153 once daily or twice daily continuously (21-day cycles), or AZD5153 once daily/twice daily continuously or intermittently plus olaparib 300 mg twice daily, until disease progression or unacceptable toxicity. Between June 30, 2017 and April 19, 2021, 34 patients received monotherapy and 15 received combination therapy. Dose-limiting toxicities were thrombocytopenia/platelet count decreased (n = 4/n = 2) and diarrhea (n = 1). The recommended phase II doses (RP2D) were AZD5153 30 mg once daily or 15 mg twice daily (monotherapy) and 10 mg once daily (intermittent schedule) with olaparib. With AZD5153 monotherapy, common treatment-emergent adverse events (TEAE) included fatigue (38.2%), thrombocytopenia, and diarrhea (each 32.4%); common grade ≥ 3 TEAEs were thrombocytopenia (14.7%) and anemia (8.8%). With the combination, common TEAEs included nausea (66.7%) and fatigue (53.3%); the most common grade ≥ 3 TEAE was thrombocytopenia (26.7%). AZD5153 had dose-dependent pharmacokinetics, with minimal accumulation, and demonstrated dose-dependent modulation of peripheral biomarkers, including upregulation of HEXIM1. One patient with metastatic pancreatic cancer receiving combination treatment had a partial response lasting 4.2 months. These results show AZD5153 was tolerable as monotherapy and in combination at the RP2Ds; common toxicities were fatigue, hematologic AEs, and gastrointestinal AEs. Strong evidence of peripheral target engagement was observed.

Prolonged Survival of NUT Midline Carcinoma and Current Approaches to Treatment

NUT midline carcinoma is a rare malignancy most commonly seen in adolescents and young adults. The disease presents most often in the lung or head and neck area but can be seen occasionally elsewhere. The diagnosis can be difficult and requires a high degree of suspicion with demonstration of the classic fusion rearrangement mutation of the NUTM1 gene with one of a variety of partners by immunohistochemistry, fluorescent in situ hybridization, or genomic analysis. Survival is usually only a number of months with few long-term survivors. Here we report one of the longest-known survivors of this disease treated with surgery and radiation without additional therapy. Systemic treatment approaches including the use of chemotherapy and BET and histone deacetylase inhibitors have yielded modest results. Further studies of these, as well as p300 and CDK9 inhibitors and combinations of BET inhibitors with chemotherapy or CDK 4/6 inhibitors, are being evaluated. Recent reports suggest there may be a role for immune checkpoint inhibitors, even in the absence of high tumor mutation burden or PD-L1 positivity. RNA sequencing of this patient's tumor demonstrated overexpression of multiple potentially targetable genes. Given the altered transcription that results from the causative mutation multi-omic evaluation of these tumors may uncover druggable targets for treatment.

BET Bromodomain Inhibitors: Novel Design Strategies and Therapeutic Applications

The mammalian bromodomain and extra-terminal domain (BET) family of proteins consists of four conserved members (Brd2, Brd3, Brd4, and Brdt) that regulate numerous cancer-related and immunity-associated genes. They are epigenetic readers of histone acetylation with broad specificity. BET proteins are linked to cancer progression due to their interaction with numerous cellular proteins including chromatin-modifying factors, transcription factors, and histone modification enzymes. The spectacular growth in the clinical development of small-molecule BET inhibitors underscores the interest and importance of this protein family as an anticancer target. Current approaches targeting BET proteins for cancer therapy rely on acetylation mimics to block the bromodomains from binding chromatin. However, bromodomain-targeted agents are suffering from dose-limiting toxicities because of their effects on other bromodomain-containing proteins. In this review, we provided an updated summary about the evolution of small-molecule BET inhibitors. The design of bivalent BET inhibitors, kinase and BET dual inhibitors, BET protein proteolysis-targeting chimeras (PROTACs), and Brd4-selective inhibitors are discussed. The novel strategy of targeting the unique C-terminal extra-terminal (ET) domain of BET proteins and its therapeutic significance will also be highlighted. Apart from single agent treatment alone, BET inhibitors have also been combined with other chemotherapeutic modalities for cancer treatment demonstrating favorable clinical outcomes. The investigation of specific biomarkers for predicting the efficacy and resistance of BET inhibitors is needed to fully realize their therapeutic potential in the clinical setting.

Role of bromodomain and extraterminal (BET) proteins in prostate cancer

INTRODUCTION

The bromodomain and extraterminal (BET) family of proteins are epigenetic readers of acetylated histones and are critical activators of oncogenic networks across many cancers. Therapeutic targeting of BET proteins has been an attractive area of clinical development for metastatic castration-resistant prostate cancer. In recent years, many structurally diverse BET inhibitors have been discovered and tested. Preclinical studies have demonstrated significant antiproliferative activity of BET inhibitors against prostate cancer. However, their clinical success as monotherapies has been limited by treatment-associated toxicities, primary and acquired drug resistance, and a lack of predictive biomarkers of benefit.

AREAS COVERED

This review provides an overview of advancements in BET inhibitor design, preclinical research, and conclusions from clinical trials in prostate cancer. We speculate on incorporating BET inhibitors into combination regimens with other agents to improve the therapeutic index of BET inhibition in treating prostate cancer.

EXPERT OPINION

The therapeutic potential of BET inhibitors for prostate cancer has been demonstrated in preclinical studies. However, further research is needed to identify biomarkers that can predict sensitivity to BET inhibitors and to develop novel, highly selective inhibitors to reduce toxicities. Finally, BET inhibitors are likely to hold the most clinical potential in combination with other agents.

Emerging Epigenetic-Based Nanotechnology for Cancer Therapy: Modulating the Tumor Microenvironment

Dysregulated epigenetic modifications dynamically drive the abnormal transcription process to affect the tumor microenvironment; thus, promoting cancer progression, drug resistance, and metastasis. Nowadays, therapies targeting epigenetic dysregulation of tumor cells and immune cells in the tumor microenvironment appear to be promising adjuncts to other cancer therapies. However, the clinical results of combination therapies containing epigenetic agents are disappointing due to systemic toxicities and limited curative effects. Here, the role of epigenetic processes, including DNA methylation, post-translational modification of histones, and noncoding RNAs is discussed, followed by detailed descriptions of epigenetic regulation of the tumor microenvironment, as well as the application of epigenetic modulators in antitumor therapy, with an emphasis on the epigenetic-based advanced drug delivery system in targeting the tumor microenvironment.

BET proteins: Biological functions and therapeutic interventions

Bromodomain and extra-terminal (BET) family member proteins (BRD2, BRD3, BRD4 and BRDT) play a pivotal role in interpreting the epigenetic information of histone Kac modification, thus controlling gene expression, remodeling chromatin structures and avoid replicative stress-induced DNA damages. Abnormal activation of BET proteins is tightly correlated to various human diseases, including cancer. Therefore, BET bromodomain inhibitors (BBIs) were considered as promising therapeutics to treat BET-related diseases, raising >70 clinical trials in the past decades. Despite preliminary effects achieved, drug resistance and adverse events represent two major challenges for current BBIs development. In this review, we will introduce the biological functions of BET proteins in both physiological and pathological conditions; and summarize the progress in current BBI drug development. Moreover, we will also discuss the major challenges in the front of BET inhibitor development and provide rational strategies to overcome these obstacles.

ACC010, a novel BRD4 inhibitor, synergized with homoharringtonine in acute myeloid leukemia with FLT3-ITD

Bromodomain-containing protein 4 (BRD4) inhibitors have been clinically developed to treat acute myeloid leukemia (AML), but their application is limited by the possibility of drug resistance, which is reportedly associated with the activation of the WNT/β-catenin pathway. Meanwhile, homoharringtonine (HHT), a classic antileukemia drug, possibly inhibits the WNT/β-catenin pathway. In this study, we attempted to combine a novel BRD4 inhibitor (ACC010) and HHT to explore their synergistic lethal effects in treating AML. Here, we found that co-treatment with ACC010 and HHT synergistically inhibited cell proliferation, induced apoptosis, and arrested the cell cycle in FMS-like tyrosine kinase 3-internal tandem duplication (FLT3-ITD)-positive AML cells in vitro, and significantly inhibiting AML progression in vivo. Mechanistically, ACC010 and HHT cooperatively downregulated MYC and inhibited FLT3 activation. Further, when HHT was added, ACC010-resistant cells demonstrated a good synergy. We also extended our study to the mouse BaF3 cell line with FLT3-inhibitor-resistant FLT3-ITD/tyrosine kinase domain mutations and AML cells without FLT3-ITD. Collectively, our results suggested that the combination treatment of ACC010 and HHT might be a promising strategy for AML patients, especially those carrying FLT3-ITD.

Possible Primary Thyroid Nuclear Protein in Testis Carcinomas with NSD3::NUTM1 Translocation Revealed by RNA Sequencing: A Report of Two Cases

Background: Nuclear protein in testis (NUT) carcinomas (NC) are a rare, highly aggressive, subset of squamous cell carcinomas, characterized by a translocation involving the NUTM1 gene. Thyroid location of NUT carcinomas has rarely been described. Methods: We report here two cases of thyroid NC with NSD3::NUTM1 translocation. Results: The first case presented as a very aggressive undifferentiated thyroid carcinoma in a 38-year-old man who died 21 months after the diagnosis. The second case was diagnosed after multiple lymphadenopathy recurrences mainly in the neck in a 37-year-old woman 7 years after total thyroidectomy for papillary thyroid carcinoma with a classic and a solid/trabecular component. Conclusions: Our case reports highlight the challenges in diagnosing these exceptional carcinomas. The therapeutic impact of the administration of pharmacological compounds with epigenetic action, in line with the physiopathology of these carcinomas, is also discussed.

Inhibition of BRD4 Promotes Pexophagy by Increasing ROS and ATM Activation

Although autophagy regulates the quality and quantity of cellular compartments, the regulatory mechanisms underlying peroxisomal autophagy (pexophagy) remain largely unknown. In this study, we identified several BRD4 inhibitors, including molibresib, a novel pexophagy inducer, via chemical library screening. Treatment with molibresib promotes loss of peroxisomes selectively, but not mitochondria, ER, or Golgi apparatus in HeLa cells. Consistently, depletion of BRD4 expression also induced pexophagy in RPE cells. In addition, the inhibition of BRD4 by molibresib increased autophagic degradation of peroxisome ATG7-dependency. We further found that molibresib produced reactive oxygen species (ROS), which potentiates ATM activation. Inhibition of ROS or ATM suppressed the loss of peroxisomes in molibresib-treated cells. Taken together, our data suggest that inhibition of BRD4 promotes pexophagy by increasing ROS and ATM activation.

Roles of Bromodomain Extra Terminal Proteins in Metabolic Signaling and Diseases

BET proteins, which recognize and bind to acetylated histones, play a key role in transcriptional regulation. The development of chemical BET inhibitors in 2010 greatly facilitated the study of these proteins. BETs play crucial roles in cancer, inflammation, heart failure, and fibrosis. In particular, BETs may be involved in regulating metabolic processes, such as adipogenesis and metaflammation, which are under tight transcriptional regulation. In addition, acetyl-CoA links energy metabolism with epigenetic modification through lysine acetylation, which creates docking sites for BET. Given this, it is possible that the ambient energy status may dictate metabolic gene transcription via a BET-dependent mechanism. Indeed, recent studies have reported that various BET proteins are involved in both metabolic signaling regulation and disease. Here, we discuss some of the most recent information on BET proteins and their regulation of the metabolism in both cellular and animal models. Further, we summarize data from some randomized clinical trials evaluating BET inhibitors for the treatment of metabolic diseases.

NUT Carcinoma—An Underdiagnosed Malignancy

NUT carcinoma (NC) is a rare and highly aggressive malignancy with a dismal prognosis and a median survival of 6–9 months only. Although very few cases of NC are reported each year, the true prevalence is estimated to be much higher, with NC potentially widely underdiagnosed due to the lack of awareness. NC primarily occurs in midline structures including thorax, head, and neck; however, other sites such as pancreas and kidney are also affected, albeit at lower frequencies. NC is characterized by a single translocation involving the NUTM1 (NUT midline carcinoma family member 1) gene and different partner genes. The resulting fusion proteins initiate tumorigenesis through a mechanism involving BET (bromo-domain and extra-terminal motif) proteins such as Bromodomain-containing protein 4 (BRD4) and inordinate acetylation of chromatin, leading to the dysregulation of growth and differentiation genes. While no clinical characteristics are specific for NC, some histologic features can be indicative; therefore, patients with these tumor characteristics should be routinely tested for NUTM1. The diagnosis of NC using immunohistochemistry with a highly specific antibody is straightforward. There are currently no standard-of-care treatment options for patients with NC. However, novel therapies specifically addressing the unique tumorigenic mechanism are under investigation, including BET inhibitors. This review aims to raise awareness of this underdiagnosed cancer entity and provide all patients the opportunity to be properly diagnosed and referred to a clinical study.

Therapeutic opportunities to modulate immune tolerance through the metabolism-chromatin axis

The ability of the immune system to discriminate external stimuli from self-components - namely immune tolerance - occurs through a coordinated cascade of events involving a dense network of immune cells. Among them, CD4⁺CD25⁺ T regulatory cells are crucial to balance immune homeostasis and function. Growing evidence supports the notion that energy metabolites can dictate T cell fate and function via epigenetic modifications, which affect gene expression without altering the DNA sequence. Moreover, changes in cellular metabolism couple with activation of immune pathways and epigenetic remodeling to finely tune the balance between T cell activation and tolerance. This Review summarizes these aspects and critically evaluates novel possibilities for developing therapeutic strategies to modulate immune tolerance through metabolism via epigenetic drugs.

The contributing factors of resistance or sensitivity to epigenetic drugs in the treatment of AML

Drug resistance is the drug-effectiveness reduction in treatment and is a serious problem in oncology and infections. In oncology, drug resistance is a complicated process resulting from enhancing the function of a pump that transports drugs out of tumor cells, or acquiring mutations in drug target. Surprisingly, most drugs are very effective in the early stages, but the response to the drug wears off over time and resistance eventually develops. Drug resistance is caused by genetic and epigenetic changes that affect cancer cells and the tumor environment. The study of inherited changes in the phenotype without changes in the DNA sequence is called epigenetics. Because of reversible changes in epigenetics, they are an attractive target for therapy. Some of these epigenetic drugs are effective in treating cancers like acute myeloid leukemia (AML), which is characterized by the accumulation and proliferation of immature hematopoietic cells in the blood and bone marrow. In this article, we outlined the various contributing factors involved in resistance or sensitivity to epigenetic drugs in the treatment of AML.

Report of the First International Symposium on NUT Carcinoma

NUT carcinoma is a rare, aggressive cancer defined by rearrangements of the NUTM1 gene. No routinely effective treatments of NUT carcinoma exist, despite harboring a targetable oncoprotein, most commonly BRD4-NUT. The vast majority of cases are fatal. Poor awareness of the disease is a major obstacle to progress in the treatment of NUT carcinoma. While the incidence likely exceeds that of Ewing sarcoma, and BRD4-NUT heralded the bromodomain and extra-terminal domain (BET) inhibitor class of selective epigenetic modulators, NUT carcinoma is incorrectly perceived as "impossibly rare," and therefore receives comparatively little private or governmental funding or prioritization by pharma. To raise awareness, propagate scientific knowledge, and initiate a consensus on standard and targeted treatment of NUT carcinoma, we held the First International Symposium on NUT Carcinoma on March 3, 2021. This virtual event had more than eighty attendees from the Americas, Europe, Asia, and Australia. Patients with NUT carcinoma and family members were represented and shared perspectives. Broadly, the four areas discussed by experts in the field included (1) the biology of NUT carcinoma; (2) standard approaches to the treatment of NUT carcinoma; (3) results of clinical trials using BET inhibitors; and (4) future directions, including novel BET bromodomain inhibitors, combinatorial approaches, and immunotherapy. It was concluded that standard chemotherapeutic approaches and first-generation BET bromodomain inhibitors, the latter complicated by a narrow therapeutic window, are only modestly effective in a minority of cases. Nonetheless, emerging second-generation targeted inhibitors, novel rational synergistic combinations, and the incorporation of immuno-oncology approaches hold promise to improve the prognosis of this disease.

Manipulating Histone Acetylation Leads to Antitumor Effects in Hemangiosarcoma Cells

Canine hemangiosarcoma (HSA) is a malignant tumor derived from endothelial cells. No effective treatment has yet been developed because of the lack of understanding of its pathogenesis. Histone acetylation, an epigenetic modification, is highly associated with cancer pathogenesis. Manipulating histone acetylation by histone deacetylase inhibitors (HDACi) or bromodomain and extraterminal domain inhibitors (BETi) is one approach to treat various cancers. However, the role of histone acetylation in HSA remains unknown. This study aimed to investigate how histone acetylation functions in HSA pathogenesis using two HDACi, suberanilohydroxamic acid (SAHA) and valproic acid (VPA), and one BETi, JQ1, in vitro and in vivo. Histone acetylation levels were high in cell lines and heterogeneous in clinical cases. SAHA and JQ1 induced apoptosis in HSA cell lines. HSA cell lines treated with SAHA and VPA upregulated inflammatory-related genes and attracted macrophage cell line RAW264 cells, which suggests that SAHA and VPA can affect immune responses. JQ1 stimulated autophagy and inhibited the cell cycle in HSA cell lines. Finally, we demonstrated that JQ1 suppressed HSA tumor cell proliferation in vivo although SAHA and VPA did not affect tumor growth. These results suggest that BETi can be alternative drugs for HSA treatment. Although further research is required, our study indicated that dysregulation of histone acetylation is likely to be involved in HSA malignancy. This article is protected by copyright. All rights reserved.