Therapeutic Targeting of EZH2 and BET BRD4 in Pediatric Rhabdoid Tumors

Deciphering the interplay of histone post-translational modifications in cancer: Co-targeting histone modulators for precision therapy

Chromatin undergoes dynamic regulation through reversible histone post-translational modifications (PTMs), orchestrated by "writers," "erasers," and "readers" enzymes. Dysregulation of these histone modulators is well implicated in shaping the cancer epigenome and providing avenues for precision therapies. The approval of six drugs for cancer therapy targeting histone modulators, along with the ongoing clinical trials of numerous candidates, represents a significant advancement in the field of precision medicine. Recently, it became apparent that histone PTMs act together in a coordinated manner to control gene expression. The intricate crosstalk of histone PTMs has been reported to be dysregulated in cancer, thus emerging as a critical factor in the complex landscape of cancer development. This formed the foundation of the swift emergence of co-targeting different histone modulators as a new strategy in cancer therapy. This review dissects how histone PTMs, encompassing acetylation, phosphorylation, methylation, SUMOylation and ubiquitination, collaboratively influence the chromatin states and impact cellular processes. Furthermore, we explore the significance of histone modification crosstalk in cancer and discuss the potential of targeting histone modification crosstalk in cancer management. Moreover, we underscore the significant strides made in developing dual epigenetic inhibitors, which hold promise as emerging candidates for effective cancer therapy.

Recent advances in multitarget-directed ligands via in silico drug discovery

To combat multifactorial refractory diseases, such as cancer, cardiovascular, and neurodegenerative diseases, multitarget drugs have become an emerging area of research aimed at 'synthetic lethality' (SL) relationships associated with drug-resistance mechanisms. In this review, we discuss the in silico design of dual and triple-targeted ligands, strategies by which specific 'warhead' groups are incorporated into a parent compound or scaffold with primary inhibitory activity against one target to develop one small molecule that inhibits two or three molecular targets in an effort to increase potency against multifactorial diseases. We also discuss the analytical exploration of structure-activity relationships (SARs), physicochemical properties, polypharmacology, scaffold feature extraction of US Food and Drug Administration (FDA)-approved multikinase inhibitors (MKIs), and updates regarding the clinical status of dual-targeted chemotypes.

Bromodomain and extraterminal (BET) proteins: biological functions, diseases, and targeted therapy

BET proteins, which influence gene expression and contribute to the development of cancer, are epigenetic interpreters. Thus, BET inhibitors represent a novel form of epigenetic anticancer treatment. Although preliminary clinical trials have shown the anticancer potential of BET inhibitors, it appears that these drugs have limited effectiveness when used alone. Therefore, given the limited monotherapeutic activity of BET inhibitors, their use in combination with other drugs warrants attention, including the meaningful variations in pharmacodynamic activity among chosen drug combinations. In this paper, we review the function of BET proteins, the preclinical justification for BET protein targeting in cancer, recent advances in small-molecule BET inhibitors, and preliminary clinical trial findings. We elucidate BET inhibitor resistance mechanisms, shed light on the associated adverse events, investigate the potential of combining these inhibitors with diverse therapeutic agents, present a comprehensive compilation of synergistic treatments involving BET inhibitors, and provide an outlook on their future prospects as potent antitumor agents. We conclude by suggesting that combining BET inhibitors with other anticancer drugs and innovative next-generation agents holds great potential for advancing the effective targeting of BET proteins as a promising anticancer strategy.

Targeting EZH2 in SMARCB1-deficient sarcomas: Advances and opportunities to potentiate the efficacy of EZH2 inhibitors

Soft tissue sarcomas (STSs) are rare mesechymal malignancies characterized by distintive molecular, histological and clinical features. Many STSs are considered as predominatly epigenetic diseases due to underlying chromatin deregulation. Discovery of deregulated functional antagonism between the chromatin remodeling BRG1/BRM-associated (BAFs) and the histone modifying Polycomb repressor complexes (PRCs) has provided novel actionable targets. In epithelioid sarcoma (ES), extracranial, extrarenal malignant rhabdoid tumors (eMRTs) and synovial sarcoma (SS), the total or partial loss of the BAF core subunit SMARCB1, driven by different alterations, is associated with PRC2 deregulation and dependency on its enzymatic subunit, EZH2. In these SMARCB1-deficient STSs, aberrant EZH2 expression and/or activity emerged as a druggable vulnerability. Although preclinical investigation supported EZH2 targeting as a promising therapeutic option, clinical studies demonstrated a variable response to EZH2 inhibitors. Actually, whereas the clinical benefit recorded in ES patients prompted the FDA approval of the EZH2 inhibitor tazemetostat, the modest and sporadic responses observed in eMRT and SS patients highlighted the need to deepen mechanistic as well as pharmacological investigations to improve drug effectiveness. We summarize the current knowledge of different mechanisms driving SMARCB1 deficiency and EZH2 deregulation in ES, eMRT and SS along with preclinical and clinical studies of EZH2-targeting agents. Possible implication of the PRC2- and enzymatic-independent functions of EZH2 and of its homolog, EZH1, in the response to anti-EZH2 agents will be discussed together with combinatorial strategies under investigation to improve the efficacy of EZH2 targeting in these tumors.

Current advances in immunotherapy for atypical teratoid rhabdoid tumor (ATRT)

Atypical teratoid rhabdoid tumors (ATRT) are rare and aggressive embryonal tumors of central nervous system that typically affect children younger than 3 years of age. Given the generally poor outcomes of patients with ATRT and the significant toxicities associated with conventional multi-modal therapies, there is an urgent need for more novel approaches to treat ATRT, one such approach being immunotherapy. The recent rise of large-scale, multicenter interdisciplinary studies has delineated several molecular and genetic characteristics unique to ATRT. This review aims to describe currently available data on the tumor immune microenvironment of ATRT and its specific subtypes and to summarize the emerging clinical and preclinical results of immunotherapy-based approaches. It will also highlight the evolving knowledge of epigenetics on immunomodulation in this epigenetically influenced tumor, which may help guide the development of effective immunotherapeutic approaches in the future.

Purification, characterization and bioactivities of a 4-O-methylglucuronoxylan from Aralia echinocaulis

The discovery of active constituents from food plants is an important area of research in pharmaceutical sciences. Aralia echinocaulis is a medicinal food plant that is mainly used to prevent or treat rheumatoid arthritis in China. This paper reported the isolation, purification and bioactivity of a polysaccharide (HSM-1-1) from A. echinocaulis. Its structural features were analyzed according to the molecular weight distribution, monosaccharide composition, gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance spectra. The results indicated that HSM-1-1 was a new 4-O-methylglucuronoxylan mainly composed of xylan and 4-O-methyl glucuronic acid with the molecular weight of 1.6 × 10⁴ Da. Furthermore, the antitumor and anti-inflammatory activities of HSM-1-1 in vitro were investigated, and the results showed that HSM-1-1 had potent proliferation inhibition activity on colon cancer cell SW480 with an inhibition rate of 17.57 ± 1.03 % at a concentration of 600 μg/mL, as measured via MTS methods. To our knowledge, this is the first report of a polysaccharide structure obtained from A. echinocaulis and its bioactivities, and its potential as an adjuvant natural product with antitumor effects is shown.

Clinicopathological and molecular characterization of a case classified by DNA‑methylation profiling as "CNS embryonal tumor with BRD4-LEUTX fusion"

Central Nervous System (CNS) embryonal tumors represent a heterogeneous group of highly aggressive tumors occurring preferentially in children but also described in adolescents and adults. In 2021, the CNS World Health Organization (WHO) classification drastically changed the diagnosis of the other CNS embryonal tumors including new histo-molecular tumor types. Here, we report a pediatric case of a novel tumor type among the other CNS embryonal tumors classified within the methylation class "CNS Embryonal Tumor with BRD4-LEUTX Fusion". The patient was a 4-year girl with no previous history of disease. For a few weeks, she suffered from headaches, vomiting and mild fever associated with increasing asthenia and loss of weight leading to a global deterioration of health. MRI brain examination revealed a large, grossly well-circumscribed tumoral mass lesion located in the left parietal lobe, contralateral hydrocephalus and midline shift. Microscopic examination showed a highly cellular tumor with a polymorphic aspect. The majority of the tumor harbored neuroectodermal features composed of small cells with scant cytoplasm and hyperchromatic nuclei associated with small "medulloblastoma-like" cells characterized by syncytial arrangement and focally a streaming pattern. Tumor cells were diffusely positive for Synaptophysin, CD56, INI1 and SMARCA4 associated with negativity for GFAP, OLIG-2, EMA, BCOR, LIN28A and MIC-2. Additional IHC features included p53 protein expression in more than 10% of the tumor's cells and very interestingly, loss of H3K27me3 expression. The Heidelberg DNA-methylation classifier classified this case as "CNS Embryonal Tumor with BRD4:LEUTX Fusion". RNA-sequencing analyses confirmed the BRD4 (exon 13)-LEUTX (exon 2) fusion with no other molecular alterations found by DNA sequencing. Our case report confirmed that a new subgroup of CNS embryonal tumor with high aggressive potential, loss of H3K27me3 protein expression, BRDA4-LEUTX fusion, named "Embryonal CNS tumor with BRD4-LEUTX fusion", has to be considered into the new CNS WHO classification.

Recent progress and novel approaches to treating atypical teratoid rhabdoid tumor

Atypical teratoid rhabdoid tumors (AT/RT) are malignant central nervous system (CNS) tumors that occur mostly in young children and have historically carried a very poor prognosis. While recent clinical trial results show that this tumor is curable, outcomes are still poor compared to other central nervous system embryonal tumors. We here review prior AT/RT clinical trials and highlight promising pre-clinical results that may inform novel clinical approaches to this aggressive cancer.

Design, Synthesis, and Biological Evaluation of a Potent Dual EZH2-BRD4 Inhibitor for the Treatment of Some Solid Tumors

Enhancer of zeste homolog 2 (EZH2) mediates the trimethylation of histone 3 lysine 27 (H3K27) to promote gene silencing. Inhibition of EZH2 is a viable strategy for cancer treatment; however, only a small subset of hematological malignancies are sensitive to small-molecule EZH2 inhibitors. EZH2 inhibitors cause H3K27 acetylation in most solid tumors, leading to drug resistance. Bromodomain-containing protein 4 (BRD4) inhibitors were reported to enhance the sensitivity of solid tumors to EZH2 inhibitors. Thus, we designed and evaluated a series of dual EZH2-BRD4 inhibitors. ZLD-2, the most promising compound, exhibited potent inhibitory activity against EZH2 and BRD4. Compared to the EZH2 inhibitor GSK126, ZLD-2 displayed potent antiproliferation activity against breast, lung, bladder, and pancreatic cancer cells. In vivo, ZLD-2 exhibited antitumor activity in a BxPC-3 mouse xenograft model, whereas GSK126 promoted tumor growth. Thus, ZLD-2 may be a lead compound for treating solid tumors.

Targeted Epigenetic Interventions in Cancer with an Emphasis on Pediatric Malignancies

Over the past two decades, novel hallmarks of cancer have been described, including the altered epigenetic landscape of malignant diseases. In addition to the methylation and hyd-roxymethylation of DNA, numerous novel forms of histone modifications and nucleosome remodeling have been discovered, giving rise to a wide variety of targeted therapeutic interventions. DNA hypomethylating drugs, histone deacetylase inhibitors and agents targeting histone methylation machinery are of distinguished clinical significance. The major focus of this review is placed on targeted epigenetic interventions in the most common pediatric malignancies, including acute leukemias, brain and kidney tumors, neuroblastoma and soft tissue sarcomas. Upcoming novel challenges include specificity and potential undesirable side effects. Different epigenetic patterns of pediatric and adult cancers should be noted. Biological significance of epigenetic alterations highly depends on the tissue microenvironment and widespread interactions. An individualized treatment approach requires detailed genetic, epigenetic and metabolomic evaluation of cancer. Advances in molecular technologies and clinical translation may contribute to the development of novel pediatric anticancer treatment strategies, aiming for improved survival and better patient quality of life.

Oncogenic roles of LINC01234 in various forms of human cancer

Abnormal expression of long non-coding RNAs (lncRNAs) plays an essential role in various malignant neoplasia. As a newly identified lncRNA, LINC01234 is abnormally expressed in several types of cancers and promotes the development of cancers. Accumulating evidence indicates that overexpression of LINC01234 is associated with poor clinical outcomes. Moreover, LINC01234 modulates many cellular events as a putative proto-oncogene, including proliferation, migration, invasion, apoptosis, cell cycle progression, and EMT. In terms of molecular mechanism, LINC01234 regulates gene expression by acting as ceRNA, participating in signaling pathways, interacting with proteins and other molecules, and encoding polypeptide. It reveals that LINC01234 may serve as a potential biomarker for cancer diagnosis, treatment, and prognosis. This review summarizes the expression pattern, biological function, and molecular mechanism of LINC01234 in human cancer and discusses its potential clinical utility.