Neuronal differentiation and cell-cycle programs mediate response to BET-bromodomain inhibition in MYC-driven medulloblastoma

Recurrent breakpoints in the BRD4 locus reduce toxicity associated with gene amplification

Recent work by the ICGC-PCAWG consortium identified recurrent focal deletions in the BRD4 gene, decreasing expression despite increased copy number. We show that these focal deletions occur in the context of cyclin E1 amplification in breast, ovarian, and endometrial cancers, and serve to disrupt BRD4 regulatory regions and gene expression across isoforms. We analyze open reading frame screen data and find that overexpression of BRD4 long (BRD4-L) and short isoform BRD4-S(a) impairs cell growth across cell lines. We confirm these results in OVSAHO ovarian cancer cells, where the overexpression of BRD4 isoforms significantly reduces tumor growth. Next, we mimic BRD4 focal deletions using CRISPR-Cas9 technology and show that these focal deletions rescue ovarian cancer cells from toxicity associated with BRD4 overexpression, suggesting that BRD4 levels must be fine-tuned for cancer cell proliferation. Our study provides experimental evidence for the first recurrent deletion reducing toxicity in cancer, expanding the landscape of cancer progression mechanisms.

Targeting processive transcription for Myc-driven circuitry in medulloblastoma

Background

Medulloblastoma is the most common malignant brain tumor of childhood. The highest-risk tumors are driven by recurrent Myc amplifications (Myc-MB) and experience poorer outcomes despite intensive multimodal therapy. The Myc transcription factor defines core regulatory circuitry for these tumors and acts to broadly amplify downstream pro-survival transcriptional programs. Therapeutic targeting of Myc directly has proven elusive, but inhibiting transcriptional cofactors may present an indirect means of drugging the oncogenic transcriptional circuitry sustaining Myc-MB.

Methods

Independent CRISPR-Cas9 screens were pooled to identify conserved dependencies in Myc-MB. We performed chromatin conformation capture (Hi-C) from primary patient Myc-MB samples to map enhancer-promoter interactions. We then treated in vitro and xenograft models with CDK9/7 inhibitors to evaluate effect on Myc-driven programs and tumor growth.

Results

Eight CRISPR-Cas9 screens performed across three independent labs identify CDK9 as a conserved dependency in Myc-MB. Myc-MB cells are susceptible to CDK9 inhibition, which is synergistic with concurrent inhibition of CDK7. Inhibition of transcriptional CDKs disrupts enhancer-promoter activity in Myc-MB and downregulates Myc-driven transcriptional programs, exerting potent anti-tumor effect.

Conclusions

Our findings identify CDK9 inhibition as a translationally promising strategy for the treatment of Myc-MB.

K ey P oints

CDK9 is an intrinsic dependency in Myc-driven medulloblastomaDual CDK9/7 inhibition disrupts Myc-driven transcriptional circuitryCDK9 inhibitors should be developed as pharmaceutical agents for Myc-MB.

I mportance of the S tudy

Medulloblastoma is the most common malignant brain tumor of childhood, and outcomes for high-risk subgroups remain unsatisfactory despite intensive multimodal therapy. In this study, we pool multiple independent CRISPR-Cas9 screens to identify transcriptional cofactors such as CDK9 as conserved dependencies in Myc-MB. Using Hi-C from primary patient samples, we map Myc enhancer-promoter interactions and show that they can be disrupted using inhibition of transcriptional CDKs. CDK9 inhibitor treatment depletes Myc-driven transcriptional programs, leading to potent anti-tumor effect in vitro and prolongation of xenograft survival in vivo . With a large number of CDK9 inhibitory compounds now in clinical development, this study highlights the opportunity for clinical translation of these for children diagnosed with Myc-MB.

Targeting BRD4 to attenuate RANKL-induced osteoclast activation and bone erosion in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease that can cause destruction of cartilage and bone's extracellular matrix. Bromodomain 4 (BRD4), as a transcriptional and epigenetic regulator, plays a key role in cancer and inflammatory diseases. While, the role of BRD4 in bone destruction in RA has not been extensively reported. Our study aimed to investigate the effect of BRD4 on the bone destruction in RA and, further, its mechanism in the pathogenesis of the disease. In this study, receiving approval from the Ethical Committee of the Affiliated Hospital of Qingdao University, we evaluated synovial tissues from patients with RA and OA for BRD4 expression through advanced techniques such as immunohistochemistry, quantitative real-time PCR (qRT-PCR), and Western blotting. We employed a collagen-induced arthritis (CIA) mouse model to assess the therapeutic efficacy of the BRD4 inhibitor JQ1 on disease progression and bone destruction, supported by detailed clinical scoring and histological examinations. Further, in vitro osteoclastogenesis assays using RAW264.7 macrophages, facilitated by TRAP staining and resorption pit assays, provided insights into the mechanistic effects of JQ1 on osteoclast function. Statistical analysis was rigorously conducted using SPSS, applying Kruskal-Wallis, one-way ANOVA, and Student's t-tests to validate the data. In our study, we found that BRD4 expression significantly increased in the synovial tissues of RA patients and the ankle joints of CIA mice, with JQ1, a BRD4 inhibitor, effectively reducing inflammation, arthritis severity (p < 0.05), and bone erosion. Treatment with JQ1 not only improved bone mass and structural integrity in CIA mice but also downregulated osteoclast-related gene expression and the RANKL/RANK signaling pathway, indicating a suppression of osteolysis. Furthermore, in vitro assays demonstrated that JQ1 markedly inhibited osteoclast differentiation and function, underscoring the pivotal role of BRD4 in osteoclastogenesis and its potential as a target for therapeutic intervention in RA-induced bone destruction. Our study concludes that targeting BRD4 with the inhibitor JQ1 significantly mitigates inflammation and bone destruction in rheumatoid arthritis, suggesting that inhibition of BRD4 may be a potential therapeutic strategy for the treatment of bone destruction in RA.

A compendium of Amplification-Related Gain Of Sensitivity genes in human cancer

While the effect of amplification-induced oncogene expression in cancer is known, the impact of copy-number gains on "bystander" genes is less understood. We create a comprehensive map of dosage compensation in cancer by integrating expression and copy number profiles from over 8000 tumors in The Cancer Genome Atlas and cell lines from the Cancer Cell Line Encyclopedia. Additionally, we analyze 17 cancer open reading frame screens to identify genes toxic to cancer cells when overexpressed. Combining these approaches, we propose a class of 'Amplification-Related Gain Of Sensitivity' (ARGOS) genes located in commonly amplified regions, yet expressed at lower levels than expected by their copy number, and toxic when overexpressed. We validate RBM14 as an ARGOS gene in lung and breast cancer cells, and suggest a toxicity mechanism involving altered DNA damage response and STING signaling. We additionally observe increased patient survival in a radiation-treated cancer cohort with RBM14 amplification.

Targeting protein synthesis pathways in MYC-amplified medulloblastoma

MYC is one of the most deregulated oncogenic transcription factors in human cancers. MYC amplification/or overexpression is most common in Group 3 medulloblastoma and is positively associated with poor prognosis. MYC is known to regulate the transcription of major components of protein synthesis (translation) machinery, leading to promoted rates of protein synthesis and tumorigenesis. MTOR signaling-driven deregulated protein synthesis is widespread in various cancers, including medulloblastoma, which can promote the stabilization of MYC. Indeed, our previous studies demonstrate that the key components of protein synthesis machinery, including mTOR signaling and MYC targets, are overexpressed and activated in MYC-amplified medulloblastoma, confirming MYC-dependent addiction of enhanced protein synthesis in medulloblastoma. Further, targeting this enhanced protein synthesis pathway with combined inhibition of MYC transcription and mTOR translation by small-molecule inhibitors, demonstrates preclinical synergistic anti-tumor potential against MYC-driven medulloblastoma in vitro and in vivo. Thus, inhibiting enhanced protein synthesis by targeting the MYC indirectly and mTOR pathways together may present a highly appropriate strategy for treating MYC-driven medulloblastoma and other MYC-addicted cancers. Evidence strongly proposes that MYC/mTOR-driven tumorigenic signaling can predominantly control the translational machinery to elicit cooperative effects on increased cell proliferation, cell cycle progression, and genome dysregulation as a mechanism of cancer initiation. Several small molecule inhibitors of targeting MYC indirectly and mTOR signaling have been developed and used clinically with immunosuppressants and chemotherapy in multiple cancers. Only a few of them have been investigated as treatments for medulloblastoma and other pediatric tumors. This review explores concurrent targeting of MYC and mTOR signaling against MYC-driven medulloblastoma. Based on existing evidence, targeting of MYC and mTOR pathways together produces functional synergy that could be the basis for effective therapies against medulloblastoma.

Mechanistic insights into medulloblastoma relapse

Pediatric brain tumors are the leading cause of cancer-related deaths in children, with medulloblastoma (MB) being the most common type. A better understanding of these malignancies has led to their classification into four major molecular subgroups. This classification not only facilitates the stratification of clinical trials, but also the development of more effective therapies. Despite recent progress, approximately 30% of children diagnosed with MB experience tumor relapse. Recurrent disease in MB is often metastatic and responds poorly to current therapies. As a result, only a small subset of patients with recurrent MB survive beyond one year. Due to its dismal prognosis, novel therapeutic strategies aimed at preventing or managing recurrent disease are urgently needed. In this review, we summarize recent advances in our understanding of the molecular mechanisms behind treatment failure in MB, as well as those characterizing recurrent cases. We also propose avenues for how these findings can be used to better inform personalized medicine approaches for the treatment of newly diagnosed and recurrent MB. Lastly, we discuss the treatments currently being evaluated for MB patients, with special emphasis on those targeting MB by subgroup at diagnosis and relapse.

Drivers Underlying Metastasis and Relapse in Medulloblastoma and Targeting Strategies

Medulloblastomas comprise a molecularly diverse set of malignant pediatric brain tumors in which patients are stratified according to different prognostic risk groups that span from very good to very poor. Metastasis at diagnosis is most often a marker of poor prognosis and the relapse incidence is higher in these children. Medulloblastoma relapse is almost always fatal and recurring cells have, apart from resistance to standard of care, acquired genetic and epigenetic changes that correlate with an increased dormancy state, cell state reprogramming and immune escape. Here, we review means to carefully study metastasis and relapse in preclinical models, in light of recently described molecular subgroups. We will exemplify how therapy resistance develops at the cellular level, in a specific niche or from therapy-induced secondary mutations. We further describe underlying molecular mechanisms on how tumors acquire the ability to promote leptomeningeal dissemination and discuss how they can establish therapy-resistant cell clones. Finally, we describe some of the ongoing clinical trials of high-risk medulloblastoma and suggest or discuss more individualized treatments that could be of benefit to specific subgroups.

Group 3 medulloblastoma transcriptional networks collapse under domain specific EP300/CBP inhibition

Chemical discovery efforts commonly target individual protein domains. Many proteins, including the EP300/CBP histone acetyltransferases (HATs), contain several targetable domains. EP300/CBP are critical gene-regulatory targets in cancer, with existing high potency inhibitors of either the catalytic HAT domain or protein-binding bromodomain (BRD). A domain-specific inhibitory approach to multidomain-containing proteins may identify exceptional-responding tumor types, thereby expanding a therapeutic index. Here, we discover that targeting EP300/CBP using the domain-specific inhibitors, A485 (HAT) or CCS1477 (BRD) have different effects in select tumor types. Group 3 medulloblastoma (G3MB) cells are especially sensitive to BRD, compared with HAT inhibition. Structurally, these effects are mediated by the difluorophenyl group in the catalytic core of CCS1477. Mechanistically, bromodomain inhibition causes rapid disruption of genetic dependency networks that are required for G3MB growth. These studies provide a domain-specific structural foundation for drug discovery efforts targeting EP300/CBP and identify a selective role for the EP300/CBP bromodomain in maintaining genetic dependency networks in G3MB.

Targeting TRIP13 in favorable histology Wilms tumor with nuclear export inhibitors synergizes with doxorubicin

Wilms tumor (WT) is the most common renal malignancy of childhood. Despite improvements in the overall survival, relapse occurs in ~15% of patients with favorable histology WT (FHWT). Half of these patients will succumb to their disease. Identifying novel targeted therapies remains challenging in part due to the lack of faithful preclinical in vitro models. Here we establish twelve patient-derived WT cell lines and demonstrate that these models faithfully recapitulate WT biology using genomic and transcriptomic techniques. We then perform loss-of-function screens to identify the nuclear export gene, XPO1, as a vulnerability. We find that the FDA approved XPO1 inhibitor, KPT-330, suppresses TRIP13 expression, which is required for survival. We further identify synergy between KPT-330 and doxorubicin, a chemotherapy used in high-risk FHWT. Taken together, we identify XPO1 inhibition with KPT-330 as a potential therapeutic option to treat FHWTs and in combination with doxorubicin, leads to durable remissions in vivo.

A therapeutically targetable positive feedback loop between lnc-HLX-2-7, HLX, and MYC that promotes group 3 medulloblastoma

Recent studies suggest that long non-coding RNAs (lncRNAs) contribute to medulloblastoma (MB) formation and progression. We have identified an lncRNA, lnc-HLX-2-7, as a potential therapeutic target in group 3 (G3) MBs. lnc-HLX-2-7 RNA specifically accumulates in the promoter region of HLX, a sense-overlapping gene of lnc-HLX-2-7, which activates HLX expression by recruiting multiple factors, including enhancer elements. RNA sequencing and chromatin immunoprecipitation reveal that HLX binds to and activates the promoters of several oncogenes, including TBX2, LIN9, HOXM1, and MYC. Intravenous treatment with cerium-oxide-nanoparticle-coated antisense oligonucleotides targeting lnc-HLX-2-7 (CNP-lnc-HLX-2-7) inhibits tumor growth by 40%-50% in an intracranial MB xenograft mouse model. Combining CNP-lnc-HLX-2-7 with standard-of-care cisplatin further inhibits tumor growth and significantly prolongs mouse survival compared with CNP-lnc-HLX-2-7 monotherapy. Thus, the lnc-HLX-2-7-HLX-MYC axis is important for regulating G3 MB progression, providing a strong rationale for using lnc-HLX-2-7 as a therapeutic target for G3 MBs.

Recent progress and structural analyses of domain-selective BET inhibitors

Epigenetic mechanisms for controlling gene expression through heritable modifications to DNA, RNA, and proteins, are essential processes in maintaining cellular homeostasis. As a result of their central role in human diseases, the proteins responsible for adding, removing, or recognizing epigenetic modifications have emerged as viable drug targets. In the case of lysine-ε-N-acetylation (Kac ), bromodomains serve as recognition modules ("readers") of this activating epigenetic mark and competition of the bromodomain-Kac interaction with small-molecule inhibitors is an attractive strategy to control aberrant bromodomain-mediated gene expression. The bromodomain and extra-terminal (BET) family proteins contain eight similar bromodomains. These BET bromodomains are among the more commonly studied bromodomain classes with numerous pan-BET inhibitors showing promising anticancer and anti-inflammatory efficacy. However, these results have yet to translate into Food and Drug Administration-approved drugs, in part due to a high degree of on-target toxicities associated with pan-BET inhibition. Improved selectivity within the BET-family has been proposed to alleviate these concerns. In this review, we analyze the reported BET-domain selective inhibitors from a structural perspective. We highlight three essential characteristics of the reported molecules in generating domain selectivity, binding affinity, and mimicking Kac molecular recognition. In several cases, we provide insight into the design of molecules with improved specificity for individual BET-bromodomains. This review provides a perspective on the current state of the field as this exciting class of inhibitors continue to be evaluated in the clinic.

Genome-wide pooled CRISPR screening in neurospheres

Spheroid culture systems have allowed in vitro propagation of cells unable to grow in canonical cell culturing conditions, and may capture cellular contexts that model tumor growth better than current model systems. The insights gleaned from genome-wide clustered regularly interspaced short palindromic repeat (CRISPR) screening of thousands of cancer cell lines grown in conventional culture conditions illustrate the value of such CRISPR pooled screens. It is clear that similar genome-wide CRISPR screens of three-dimensional spheroid cultures will be important for future biological discovery. Here, we present a protocol for genome-wide CRISPR screening of three-dimensional neurospheres. While many in-depth protocols and discussions have been published for more typical cell lines, few detailed protocols are currently available in the literature for genome-wide screening in spheroidal cell lines. For those who want to screen such cell lines, and particularly neurospheres, we provide a step-by-step description of assay development tests to be performed before screening, as well as for the screen itself. We highlight considerations of variables that make these screens distinct from, or similar to, typical nonspheroid cell lines throughout. Finally, we illustrate typical outcomes of neurosphere genome-wide screens, and how neurosphere screens typically produce slightly more heterogeneous signal distributions than more canonical cancer cell lines. Completion of this entire protocol will take 8-12 weeks from the initial assay development tests to deconvolution of the sequencing data.

DNA-PKcs as an upstream mediator of OCT4-induced MYC activation in small cell lung cancer

Small cell lung cancer (SCLC) is a neuroendocrine tumor noted for the rapid development of both metastases and resistance to chemotherapy. High mutation burden, ubiquitous loss of TP53 and RB1, and a mutually exclusive amplification of MYC gene family members contribute to genomic instability and make the development of new targeted agents a challenge. Previously, we reported a novel OCT4-induced MYC transcriptional activation pathway involving c-MYC, pOCT4^S111, and MAPKAPK2 in progressive neuroblastoma, also a neuroendocrine tumor. Using tumor microarray analysis of clinical samples and preclinical models, we now report a correlation in expression between these proteins in SCLC. In correlating c-MYC protein expression with genomic amplification, we determined that some SCLC cell lines exhibited high c-MYC without genomic amplification, implying amplification-independent MYC activation. We then confirmed direct interaction between OCT4 and DNA-PKcs and identified specific OCT4 and DNA-PKcs binding sites. Knock-down of both POU5F1 (encoding OCT4) and PRKDC (encoding DNA-PKcs) resulted in decreased c-MYC expression. Further, we confirmed binding of OCT4 to the promoter/enhancer region of MYC. Together, these data establish the presence of a DNA-PKcs/OCT4/c-MYC pathway in SCLCs. We then disruptively targeted this pathway and demonstrated anticancer activity in SCLC cell lines and xenografts using both DNA-PKcs inhibitors and a protein-protein interaction inhibitor of DNA-PKcs and OCT4. In conclusion, we demonstrate here that DNA-PKcs can mediate high c-MYC expression in SCLCs, and that this pathway may represent a new therapeutic target for SCLCs with high c-MYC expression.

Bromodomain and Extraterminal Domain (BET) Protein Inhibition Hinders Glioblastoma Progression by Inducing Autophagy-Dependent Differentiation

Glioblastoma multiforme (GBM) is the most common and aggressive type of malignant primary brain tumor, and it is characterized by a high recurrence incidence and poor prognosis due to the presence of a highly heterogeneous mass of stem cells with self-renewal capacity and stemness maintenance ability. In recent years, the epigenetic landscape of GBM has been explored and many epigenetic alterations have been investigated. Among the investigated epigenetic abnormalities, the bromodomain and extra-terminal domain (BET) chromatin readers have been found to be significantly overexpressed in GBM. In this work, we investigated the effects of BET protein inhibition on GBM cell reprogramming. We found that the pan-BET pharmacological inhibitor JQ1 was able to promote a differentiation program in GBM cells, thus impairing cell proliferation and enhancing the toxicity of the drug Temozolomide (TMZ). Notably, the pro-differentiation capability of JQ1 was prevented in autophagy-defective models, suggesting that autophagy activation is necessary for BET protein activity in regulating glioma cell fate. Given the growing interest in epigenetic therapy, our results further support the possibility of introducing a BET-based approach in GBM clinical management.

Metabolic rewiring in MYC-driven medulloblastoma by BET-bromodomain inhibition

Medulloblastoma (MB) is the most common malignant brain tumour in children. High-risk MB patients harbouring MYC amplification or overexpression exhibit a very poor prognosis. Aberrant activation of MYC markedly reprograms cell metabolism to sustain tumorigenesis, yet how metabolism is dysregulated in MYC-driven MB is not well understood. Growing evidence unveiled the potential of BET-bromodomain inhibitors (BETis) as next generation agents for treating MYC-driven MB, but whether and how BETis may affect tumour cell metabolism to exert their anticancer activities remains unknown. In this study, we explore the metabolic features characterising MYC-driven MB and examine how these are altered by BET-bromodomain inhibition. To this end, we employed an NMR-based metabolomics approach applied to the MYC-driven MB D283 and D458 cell lines before and after the treatment with the BETi OTX-015. We found that OTX-015 triggers a metabolic shift in both cell lines resulting in increased levels of myo-inositol, glycerophosphocholine, UDP-N-acetylglucosamine, glycine, serine, pantothenate and phosphocholine. Moreover, we show that OTX-015 alters ascorbate and aldarate metabolism, inositol phosphate metabolism, phosphatidylinositol signalling system, glycerophospholipid metabolism, ether lipid metabolism, aminoacyl-tRNA biosynthesis, and glycine, serine and threonine metabolism pathways in both cell lines. These insights provide a metabolic characterisation of MYC-driven childhood MB cell lines, which could pave the way for the discovery of novel druggable pathways. Importantly, these findings will also contribute to understand the downstream effects of BETis on MYC-driven MB, potentially aiding the development of new therapeutic strategies to combat medulloblastoma.

Combination of Ribociclib with BET-Bromodomain and PI3K/mTOR Inhibitors for Medulloblastoma Treatment In Vitro and In Vivo

Despite improvement in the treatment of medulloblastoma over the last years, numerous patients with MYC- and MYCN-driven tumors still fail current therapies. Medulloblastomas have an intact retinoblastoma protein RB, suggesting that CDK4/6 inhibition might represent a therapeutic strategy for which drug combination remains understudied. We conducted high-throughput drug combination screens in a Group3 (G3) medulloblastoma line using the CDK4/6 inhibitor (CDK4/6i) ribociclib at IC20, referred to as an anchor, and 87 oncology drugs approved by FDA or in clinical trials. Bromodomain and extra terminal (BET) and PI3K/mTOR inhibitors potentiated ribociclib inhibition of proliferation in an established cell line and freshly dissociated tumor cells from intracranial xenografts of G3 and Sonic hedgehog (SHH) medulloblastomas in vitro. A reverse combination screen using the BET inhibitor JQ1 as anchor, revealed CDK4/6i as the most potentiating drugs. In vivo, ribociclib showed single-agent activity in medulloblastoma models whereas JQ1 failed to show efficacy due to high clearance and insufficient free brain concentration. Despite in vitro synergy, combination of ribociclib with the PI3K/mTOR inhibitor paxalisib did not significantly improve the survival of G3 and SHH medulloblastoma-bearing mice compared with ribociclib alone. Molecular analysis of ribociclib and paxalisib-treated tumors revealed that E2F targets and PI3K/AKT/MTORC1 signaling genes were depleted, as expected. Importantly, in one untreated G3MB model HD-MB03, the PI3K/AKT/MTORC1 gene set was enriched in vitro compared with in vivo suggesting that the pathway displayed increased activity in vitro. Our data illustrate the difficulty in translating in vitro findings in vivo. See related article in Mol Cancer Ther (2022) 21(8):1306-1317.

Super enhancers: Pathogenic roles and potential therapeutic targets for acute myeloid leukemia (AML)

Acute myeloid leukemia (AML) is a malignant hematological tumor with disordered oncogenes/tumor suppressor genes and limited treatments. The potent anti-cancer effects of bromodomain and extra-terminal domain (BET) inhibitors, targeting the key component of super enhancers, in early clinical trials on AML patients, implies the critical role of super enhancers in AML. Here, we review the concept and characteristic of super enhancer, and then summarize the current researches about super enhancers in AML pathogenesis, diagnosis and classification, followed by illustrate the potential super enhancer-related targets and drugs, and propose the future directions of super enhancers in AML. This information provides integrated insight into the roles of super enhancers in this disease.

Development of an N-Terminal BRD4 Bromodomain-Targeted Degrader

Targeted protein degradation is a powerful induced-proximity tool to control cellular protein concentrations using small molecules. However, the design of selective degraders remains empirical. Among bromodomain and extra-terminal (BET) family proteins, BRD4 is the primary therapeutic target over family members BRD2/3/T. Existing strategies for selective BRD4 degradation use pan-BET inhibitors optimized for BRD4:E3 ubiquitin ligase (E3) ternary complex formation, but these result in residual inhibition of undegraded BET-bromodomains by the pan-BET ligand, obscuring BRD4-degradation phenotypes. Using our selective inhibitor of the first BRD4 bromodomain, iBRD4-BD1 (IC50 = 12 nM, 23- to 6200-fold intra-BET selectivity), we developed dBRD4-BD1 to selectively degrade BRD4 (DC50 = 280 nM). Notably, dBRD4-BD1 upregulates BRD2/3, a result not observed with degraders using pan-BET ligands. Designing BRD4 selectivity up front enables analysis of BRD4 biology without wider BET-inhibition and simplifies designing BRD4-selective heterobifunctional molecules, such as degraders with new E3 recruiting ligands or for additional probes beyond degraders.

Medulloblastoma group 3 and 4 tumors comprise a clinically and biologically significant expression continuum reflecting human cerebellar development

Medulloblastoma is currently subclassified into distinct DNA methylation subgroups/subtypes with particular clinico-molecular features. Using RNA sequencing (RNA-seq) in large, well-annotated cohorts of medulloblastoma, we show that transcriptionally group 3 and group 4 medulloblastomas exist as intermediates on a bipolar continuum between archetypal group 3 and group 4 entities. Continuum position is prognostic, reflecting a propensity for specific DNA copy-number changes, and specific switches in isoform/enhancer usage and RNA editing. Examining single-cell RNA-seq (scRNA-seq) profiles, we show that intratumoral transcriptional heterogeneity along the continuum is limited in a subtype-dependent manner. By integrating with a human scRNA-seq reference atlas, we show that this continuum is mirrored by an equivalent continuum of transcriptional cell types in early fetal cerebellar development. We identify distinct developmental niches for all four major subgroups and link each to a common developmental antecedent. Our findings show a transcriptional continuum arising from oncogenic disruption of highly specific fetal cerebellar cell types, linked to almost every aspect of group 3/group 4 molecular biology and clinico-pathology.

Target actionability review to evaluate CDK4/6 as a therapeutic target in paediatric solid and brain tumours

BACKGROUND

Childhood cancer is still a leading cause of death around the world. To improve outcomes, there is an urgent need for tailored treatment. The systematic evaluation of existing preclinical data can provide an overview of what is known and identify gaps in the current knowledge. Here, we applied the target actionability review (TAR) methodology to assess the strength and weaknesses of available scientific literature on CDK4/6 as a therapeutic target in paediatric solid and brain tumours by structured critical appraisal.

METHODS

Using relevant search terms in PubMed, a list of original publications investigating CDK4/6 in paediatric solid tumour types was identified based on relevancy criteria. Each publication was annotated for the tumour type and categorised into separate proof-of-concept (PoC) data modules. Based on rubrics, quality and experimental outcomes were scored independently by two reviewers. A third reviewer evaluated and adjudicated score discrepancies. Scores for each PoC module were averaged for each tumour type and visualised in a heatmap matrix in the publicly available R2 data portal.

RESULTS AND CONCLUSIONS

This CDK4/6 TAR, generated by analysis of 151 data entries from 71 publications, showed frequent genomic aberrations of CDK4/6 in rhabdomyosarcoma, osteosarcoma, high-grade glioma, medulloblastoma, and neuroblastoma. However, a clear correlation between CDK4/6 aberrations and compound efficacy is not coming forth from the literature. Our analysis indicates that several paediatric indications would need (further) preclinical evaluation to allow for better recommendations, especially regarding the dependence of tumours on CDK4/6, predictive biomarkers, resistance mechanisms, and combination strategies. Nevertheless, our TAR heatmap provides support for the relevance of CDK4/6 inhibition in Ewing sarcoma, medulloblastoma, malignant peripheral nerve sheath tumour and to a lesser extent neuroblastoma, rhabdomyosarcoma, rhabdoid tumour and high-grade glioma. The interactive heatmap is accessible through R2 [r2platform.com/TAR/CDK4_6].

Regulation of 3D Organization and Its Role in Cancer Biology

Three-dimensional (3D) genomics is the frontier field in the post-genomics era, its foremost content is the relationship between chromatin spatial conformation and regulation of gene transcription. Cancer biology is a complex system resulting from genetic alterations in key tumor oncogenes and suppressor genes for cell proliferation, DNA replication, cell differentiation, and homeostatic functions. Although scientific research in recent decades has revealed how the genome sequence is mutated in many cancers, high-order chromosomal structures involved in the development and fate of cancer cells represent a crucial but rarely explored aspect of cancer genomics. Hence, dissection of the 3D genome conformation of cancer helps understand the unique epigenetic patterns and gene regulation processes that distinguish cancer biology from normal physiological states. In recent years, research in tumor 3D genomics has grown quickly. With the rapid progress of 3D genomics technology, we can now better determine the relationship between cancer pathogenesis and the chromatin structure of cancer cells. It is becoming increasingly explicit that changes in 3D chromatin structure play a vital role in controlling oncogene transcription. This review focuses on the relationships between tumor gene expression regulation, tumor 3D chromatin structure, and cancer phenotypic plasticity. Furthermore, based on the functional consequences of spatial disorganization in the cancer genome, we look forward to the clinical application prospects of 3D genomic biomarkers.

Bromodomain and Extra-Terminal Protein Inhibitors: Biologic Insights and Therapeutic Potential in Pediatric Brain Tumors

Pediatric brain tumors have surpassed leukemia as the leading cause of cancer-related death in children. Several landmark studies from the last two decades have shown that many pediatric brain tumors are driven by epigenetic dysregulation within specific developmental contexts. One of the major determinants of epigenetic control is the histone code, which is orchestrated by a number of enzymes categorized as writers, erasers, and readers. Bromodomain and extra-terminal (BET) proteins are reader proteins that bind to acetylated lysines in histone tails and play a crucial role in regulating gene transcription. BET inhibitors have shown efficacy in a wide range of cancers, and a number have progressed to clinical phase testing. Here, we review the evidence for BET inhibitors in pediatric brain tumor experimental models, as well as their translational potential.

An effector index to predict target genes at GWAS loci

Drug development and biological discovery require effective strategies to map existing genetic associations to causal genes. To approach this problem, we selected 12 common diseases and quantitative traits for which highly powered genome-wide association studies (GWAS) were available. For each disease or trait, we systematically curated positive control gene sets from Mendelian forms of the disease and from targets of medicines used for disease treatment. We found that these positive control genes were highly enriched in proximity of GWAS-associated single-nucleotide variants (SNVs). We then performed quantitative assessment of the contribution of commonly used genomic features, including open chromatin maps, expression quantitative trait loci (eQTL), and chromatin conformation data. Using these features, we trained and validated an Effector Index (Ei), to map target genes for these 12 common diseases and traits. Ei demonstrated high predictive performance, both with cross-validation on the training set, and an independently derived set for type 2 diabetes. Key predictive features included coding or transcript-altering SNVs, distance to gene, and open chromatin-based metrics. This work outlines a simple, understandable approach to prioritize genes at GWAS loci for functional follow-up and drug development, and provides a systematic strategy for prioritization of GWAS target genes.

Clinical Trials in High-Risk Medulloblastoma: Evolution of the SIOP-Europe HR-MB Trial

Medulloblastoma patients receive adapted therapies stratified according to their risk-profile. Favourable, standard, and high disease-risk groups are each defined by the status of clinical and pathological risk factors, alongside an evolving repertoire of diagnostic and prognostic biomarkers. Medulloblastoma clinical trials in Europe are coordinated by the International Society for Paediatric Oncology (SIOP-Europe) brain tumour group. Favourable and standard-risk patients are eligible for the SIOP-PNET5-MB clinical trial protocol. In contrast, therapies for high-risk disease worldwide have, to date, encompassed a range of different treatment philosophies, with no clear consensus on approach. Higher radiotherapy doses are typically deployed, delivered either conventionally or in hyper-fractionated/accelerated regimens. Similarly, both standard and high-dose chemotherapies were assessed. However, trials to date in high-risk medulloblastoma have commonly been institutional or national, based on modest cohort sizes, and have not evaluated the relative performance of different strategies in a randomised fashion. We describe the concepts and design of the SIOP-E high-risk medulloblastoma clinical trial (SIOP-HR-MB), the first international biomarker-driven, randomised, clinical trial for high-risk medulloblastoma. SIOP-HR-MB is programmed to recruit >800 patients in 16 countries across Europe; its primary objectives are to assess the relative efficacies of the alternative established regimens. The HR-MB patient population is molecularly and clinically defined, and upfront assessments incorporate a standardised central review of molecular pathology, radiology, and radiotherapy quality assurance. Secondary objectives include the assessment of (i) novel therapies within an upfront 'window' and (ii) therapy-associated neuropsychology, toxicity, and late effects, alongside (iii) the collection of materials for comprehensive integrated studies of biological determinants within the SIOP-HR-MB cohort.

Zebrafish Paralogs brd2a and brd2b Are Needed for Proper Circulatory, Excretory and Central Nervous System Formation and Act as Genetic Antagonists during Development

Brd2 belongs to the BET family of epigenetic transcriptional co-regulators that act as adaptor-scaffolds for the assembly of chromatin-modifying complexes and other factors at target gene promoters. Brd2 is a protooncogene and candidate gene for juvenile myoclonic epilepsy in humans, a homeobox gene regulator in Drosophila, and a maternal-zygotic factor and cell death modulator that is necessary for normal development of the vertebrate central nervous system (CNS). As two copies of Brd2 exist in zebrafish, we use antisense morpholino knockdown to probe the role of paralog Brd2b, as a comparative study to Brd2a, the ortholog of human Brd2. A deficiency in either paralog results in excess cell death and dysmorphology of the CNS, whereas only Brd2b deficiency leads to loss of circulation and occlusion of the pronephric duct. Co-knockdown of both paralogs suppresses single morphant defects, while co-injection of morpholinos with paralogous RNA enhances them, suggesting novel genetic interaction with functional antagonism. Brd2 diversification includes paralog-specific RNA variants, a distinct localization of maternal factors, and shared and unique spatiotemporal expression, providing unique insight into the evolution and potential functions of this gene.

MYC protein interactors in gene transcription and cancer

The transcription factor and oncoprotein MYC is a potent driver of many human cancers and can regulate numerous biological activities that contribute to tumorigenesis. How a single transcription factor can regulate such a diverse set of biological programmes is central to the understanding of MYC function in cancer. In this Perspective, we highlight how multiple proteins that interact with MYC enable MYC to regulate several central control points of gene transcription. These include promoter binding, epigenetic modifications, initiation, elongation and post-transcriptional processes. Evidence shows that a combination of multiple protein interactions enables MYC to function as a potent oncoprotein, working together in a 'coalition model', as presented here. Moreover, as MYC depends on its protein interactome for function, we discuss recent research that emphasizes an unprecedented opportunity to target protein interactors to directly impede MYC oncogenesis.

Systems pharmacogenomics identifies novel targets and clinically actionable therapeutics for medulloblastoma

BACKGROUND

Medulloblastoma (MB) is the most common malignant paediatric brain tumour and a leading cause of cancer-related mortality and morbidity. Existing treatment protocols are aggressive in nature resulting in significant neurological, intellectual and physical disabilities for the children undergoing treatment. Thus, there is an urgent need for improved, targeted therapies that minimize these harmful side effects.

METHODS

We identified candidate drugs for MB using a network-based systems-pharmacogenomics approach: based on results from a functional genomics screen, we identified a network of interactions implicated in human MB growth regulation. We then integrated drugs and their known mechanisms of action, along with gene expression data from a large collection of medulloblastoma patients to identify drugs with potential to treat MB.

RESULTS

Our analyses identified drugs targeting CDK4, CDK6 and AURKA as strong candidates for MB; all of these genes are well validated as drug targets in other tumour types. We also identified non-WNT MB as a novel indication for drugs targeting TUBB, CAD, SNRPA, SLC1A5, PTPRS, P4HB and CHEK2. Based upon these analyses, we subsequently demonstrated that one of these drugs, the new microtubule stabilizing agent, ixabepilone, blocked tumour growth in vivo in mice bearing patient-derived xenograft tumours of the Sonic Hedgehog and Group 3 subtype, providing the first demonstration of its efficacy in MB.

CONCLUSIONS

Our findings confirm that this data-driven systems pharmacogenomics strategy is a powerful approach for the discovery and validation of novel therapeutic candidates relevant to MB treatment, and along with data validating ixabepilone in PDX models of the two most aggressive subtypes of medulloblastoma, we present the network analysis framework as a resource for the field.

Epigenetic heterogeneity promotes acquired resistance to BET bromodomain inhibition in ovarian cancer

BET bromodomain inhibitors (BETi) are promising therapeutic regimens for epithelial ovarian cancer (EOC). However, early-stage clinical trials indicate that drug tolerance may limit their anti-tumor efficacy. Here, we show that JQ1-refractory EOC cells acquire reversible resistance to BET inhibition and remain dependent on BRD4 function. The insensitivity is driven by a unique non-genetic mechanism that involves clonal selection for a pre-existing cell subpopulation with ample acetylated histones and sufficient nuclear phase-separated BRD4 droplets to counteract BETi antagonism. A vertical combination approach by co-blocking BET proteins and downstream Aurora kinases proves to achieve more complete responses than single inhibitors. Collectively, our study implicates epigenetic heterogeneity in therapeutic resistance to chromatin-targeted agents and proposes a rational strategy to address this anticipated clinical dilemma.

Enhancer rewiring in tumors: an opportunity for therapeutic intervention

Enhancers are cis-regulatory sequences that fine-tune expression of their target genes in a spatiotemporal manner. They are recognized by sequence-specific transcription factors, which in turn recruit transcriptional coactivators that facilitate transcription by promoting assembly and activation of the basal transcriptional machinery. Their functional importance is underscored by the fact that they are often the target of genetic and nongenetic events in human disease that disrupt their sequence, interactome, activation potential, and/or chromatin environment. Dysregulation of transcription and addiction to transcriptional effectors that interact with and modulate enhancer activity are common features of cancer cells and are amenable to therapeutic intervention. Here, we discuss the current knowledge on enhancer biology, the broad spectrum of mechanisms that lead to their malfunction in tumor cells, and recent progress in developing drugs that efficaciously target their dependencies.

The long noncoding RNA lnc-HLX-2-7 is oncogenic in Group 3 medulloblastomas

BACKGROUND

Medulloblastoma (MB) is an aggressive brain tumor that predominantly affects children. Recent high-throughput sequencing studies suggest that the noncoding RNA genome, in particular long noncoding RNAs (lncRNAs), contributes to MB subgrouping. Here we report the identification of a novel lncRNA, lnc-HLX-2-7, as a potential molecular marker and therapeutic target in Group 3 MBs.

METHODS

Publicly available RNA sequencing (RNA-seq) data from 175 MB patients were interrogated to identify lncRNAs that differentiate between MB subgroups. After characterizing a subset of differentially expressed lncRNAs in vitro and in vivo, lnc-HLX-2-7 was deleted by CRISPR/Cas9 in the MB cell line. Intracranial injected tumors were further characterized by bulk and single-cell RNA-seq.

RESULTS

Lnc-HLX-2-7 is highly upregulated in Group 3 MB cell lines, patient-derived xenografts, and primary MBs compared with other MB subgroups as assessed by quantitative real-time, RNA-seq, and RNA fluorescence in situ hybridization. Depletion of lnc-HLX-2-7 significantly reduced cell proliferation and 3D colony formation and induced apoptosis. Lnc-HLX-2-7-deleted cells injected into mouse cerebellums produced smaller tumors than those derived from parental cells. Pathway analysis revealed that lnc-HLX-2-7 modulated oxidative phosphorylation, mitochondrial dysfunction, and sirtuin signaling pathways. The MYC oncogene regulated lnc-HLX-2-7, and the small-molecule bromodomain and extraterminal domain family‒bromodomain 4 inhibitor Jun Qi 1 (JQ1) reduced lnc-HLX-2-7 expression.

CONCLUSIONS

Lnc-HLX-2-7 is oncogenic in MB and represents a promising novel molecular marker and a potential therapeutic target in Group 3 MBs.

Bromodomain and extra-terminal inhibitors-A consensus prioritisation after the Paediatric Strategy Forum for medicinal product development of epigenetic modifiers in children-ACCELERATE

Based on biology and pre-clinical data, bromodomain and extra-terminal (BET) inhibitors have at least three potential roles in paediatric malignancies: NUT (nuclear protein in testis) carcinomas, MYC/MYCN-driven cancers and fusion-driven malignancies. However, there are now at least 10 BET inhibitors in development, with a limited relevant paediatric population in which to evaluate these medicinal products. Therefore, a meeting was convened with the specific aim to develop a consensus among relevant biopharmaceutical companies, academic researchers, as well as patient and family advocates, about the development of BET inhibitors, including prioritisation and their specific roles in children. Although BET inhibitors have been in clinical trials in adults since 2012, the first-in-child study (BMS-986158) only opened in 2019. In the future, when there is strong mechanistic rationale or pre-clinical activity of a class of medicinal product in paediatrics, early clinical evaluation with embedded correlative studies of a member of the class should be prioritised and rapidly executed in paediatric populations. There is a strong mechanistic and biological rationale to evaluate BET inhibitors in paediatrics, underpinned by substantial, but not universal, pre-clinical data. However, most pan-BET inhibitors have been challenging to administer in adults, since monotherapy results in only modest anti-tumour activity and provides a narrow therapeutic index due to thrombocytopenia. It was concluded that it is neither scientifically justified nor feasible to undertake simultaneously early clinical trials in paediatrics of all pan-BET inhibitors. However, there is a clinical need for global access to BET inhibitors for patients with NUT carcinoma, a very rare malignancy driven by bromodomain fusions, with proof of concept of clinical benefit in a subset of patients treated with BET inhibitors. Development and regulatory pathway in this indication should include children and adolescents as well as adults. Beyond NUT carcinoma, it was proposed that further clinical development of other pan-BET inhibitors in children should await the results of the first paediatric clinical trial of BMS-986158, unless there is compelling rationale based on the specific agent of interest. BDII-selective inhibitors, central nervous system-penetrant BET inhibitors (e.g. CC-90010), and those dual-targeting BET/p300 bromodomain are of particular interest and warrant further pre-clinical investigation. This meeting emphasised the value of a coordinated and integrated strategy to drug development in paediatric oncology. A multi-stakeholder approach with multiple companies developing a consensus with academic investigators early in the development of a class of compounds, and then engaging regulatory agencies would improve efficiency, productivity, conserve resources and maximise potential benefit for children with cancer.

In vitro Modeling of Embryonal Tumors

A subset of pediatric tumors affects very young children and are thought to arise during fetal life. A common theme is that these embryonal tumors hijack developmental programs, causing a block in differentiation and, as a consequence, unrestricted proliferation. Embryonal tumors, therefore typically maintain an embryonic gene signature not found in their differentiated progeny. Still, the processes underpinning malignant transformation remain largely unknown, which is hampering therapeutic innovation. To gain more insight into these processes, in vitro and in vivo research models are indispensable. However, embryonic development is an extremely dynamic process with continuously changing cellular identities, making it challenging to define cells-of-origin. This is crucial for the development of representative models, as targeting the wrong cell or targeting a cell within an incorrect developmental time window can result in completely different phenotypes. Recent innovations in in vitro cell models may provide more versatile platforms to study embryonal tumors in a scalable manner. In this review, we outline different in vitro models that can be explored to study embryonal tumorigenesis and for therapy development.

CloneSifter: enrichment of rare clones from heterogeneous cell populations

BACKGROUND

Many biological processes, such as cancer metastasis, organismal development, and acquisition of resistance to cytotoxic therapy, rely on the emergence of rare sub-clones from a larger population. Understanding how the genetic and epigenetic features of diverse clones affect clonal fitness provides insight into molecular mechanisms underlying selective processes. While large-scale barcoding with NGS readout has facilitated cellular fitness assessment at the population level, this approach does not support characterization of clones prior to selection. Single-cell genomics methods provide high biological resolution, but are challenging to scale across large populations to probe rare clones and are destructive, limiting further functional analysis of important clones.

RESULTS

Here, we develop CloneSifter, a methodology for tracking and enriching rare clones throughout their response to selection. CloneSifter utilizes a CRISPR sgRNA-barcode library that facilitates the isolation of viable cells from specific clones within the barcoded population using a sequence-specific retrieval reporter. We demonstrate that CloneSifter can measure clonal fitness of cancer cell models in vitro and retrieve targeted clones at abundance as low as 1 in 1883 in a heterogeneous cell population.

CONCLUSIONS

CloneSifter provides a means to track and access specific and rare clones of interest across dynamic changes in population structure to comprehensively explore the basis of these changes.

Role of cyclins and cyclin-dependent kinases in pluripotent stem cells and their potential as a therapeutic target

Over the last 15 years connections between cell cycle control, maintenance of pluripotency, and control of cell fate decisions have been firmly established. With the emergence of powerful tools, such as highly-specific small molecule inhibitors for cyclin-dependent protein kinase (CDK) activity and single-cell imaging technologies, the mechanistic links between cyclins, CDKs and regulation in PSCs in mechanistic detail has been made possible. In this review, we discuss new developments that mechanistically link the CDK regulatory network to control of cell fate decisions, including maintenance of the pluripotent state. Overall, these findings have potential to impact the translational applications of stem cells in regenerative medicine, drug discovery and cancer treatment.

Bromodomains and Extra-Terminal (BET) Inhibitor JQ1 Suppresses Proliferation of Acute Lymphocytic Leukemia by Inhibiting c-Myc-Mediated Glycolysis

Background

Acute lymphocytic leukemia (ALL) is a common blood cancer which induces high mortality in children. Bromodomains and extra-terminal (BET) protein inhibitors, such as JQ1 and ARV-825, are promising cancer therapeutic agents that can be used by targeting c-Myc. A recent work reported that JQ1 effectively attenuates ALL in vitro by suppressing cell proliferation and accelerating apoptosis. The purpose of this research was to probe into the potential mechanism of how JQ1 inhibits ALL cell proliferation in vitro.

Material/Methods

Cell viability of ALL cells were measured by CTG after treatment by JQ1. Cell cycle analysis was done by EdU and PI staining. Cell apoptosis was assessed by Annexin V/PI staining. Glycolysis was detected using Seahorse and LC-MS kits. The expression of glycolytic rate-limiting enzymes was assessed by RNA-seq, qRT-PCR, and Western blot.

Results

JQ1 suppressed cell proliferation by arresting the cell cycle and inducing the apoptosis of acute lymphocytic leukemia cells. JQ1 inhibited cell proliferation of B-ALL cells by restraining glycolysis. Conversely, the cell cycle block of B-ALL cells induced by JQ1 was partially abolished after pretreatment with 2-Deoxy-D-glucose (2-DG), an inhibitor of glycolysis. Furthermore, JQ1 restrained the glycolysis of B-ALL cell lines by remarkably downregulating the rate-limiting enzymes of glycolysis, such as hexokinase 2, phosphofructokinase, and lactate dehydrogenase A. Moreover, the cell cycle arrest was reversed in B-ALL cells with overexpressed c-Myc treated by JQ1, which is involved in the enhancement of glycolysis.

Conclusions

The BET inhibitor JQ1 suppresses the proliferation of ALL by inhibiting c-Myc-mediated glycolysis, thus providing a new strategy for the treatment of ALL.

Pediatric embryonal brain tumors in the molecular era

Introduction: Embryonal brain tumors (EBTs) are highly aggressive malignancies predominantly affecting children. They include medulloblastoma (MB), atypical rhabdoid/teratoid tumors (ATRT), pineoblastoma (PB), embryonal tumor multiple rosettes (ETMR)/C19MC-altered tumors, and newly recognized embryonal tumors with FOXR2 activation or BCOR alteration.Areas covered: This review will provide a comprehensive overview and updated of the literature on each of these EBTs. The evolution from location- and histopathology-based diagnosis to more specific and robust molecular-based classification schemes, as well as treatment modalities, will be discussed.Expert commentary: The subgrouping of EBTs with multi-omic profiling has had important implications for risk stratification and discovery of targetable driver pathways. However, these innovations are unlikely to significantly improve survival among high-risk patients until robust preclinical studies are conducted, followed by validation in biology-informed clinical trials.

Combinational therapeutic targeting of BRD4 and CDK7 synergistically induces anticancer effects in head and neck squamous cell carcinoma

The bromodomain and extra-terminal domain protein BRD4 has been recognized as a key oncogenic driver and a druggable target against cancer. However, these BRD4 inhibitors as monotherapy were moderate in efficacy in preclinical models. Here we utilized a small-scale drug synergy screen that combined the BRD4 inhibitor (JQ1) with 8 epigenetic or transcriptional targeted chemicals and identified THZ1 (a CDK7 inhibitor) acting synergistically with JQ1 against head neck squamous cell carcinoma (HNSCC). Combinational JQ1 and THZ1 treatment impaired cell proliferation, induced apoptosis and senescence, which were largely recapitulated by dual BRD4 and CDK7 knockdown. Combinational treatment inhibited tumor growth and progression in 4NQO-induced HNSCC and xenograft animal models. RNA-sequencing analyses identified hundreds of differentially expressed genes modulated by JQ1 and THZ1, which were significantly enriched in categories including cell cycle and apoptosis. Mechanistically, combinational treatment reduced H3K27ac enrichment in the super-enhancer region of YAP1, which inactivated its transcription and in turn induced anti-proliferative and pro-apoptotic effects. Combined BRD4 and CDK7 upregulation associated with worst prognosis in HNSCC patients. Collectively, our findings reveal a novel therapeutic strategy of pharmacological inhibitions of BRD4 and CDK7 against HNSCC.

Impacts of cannabinoid epigenetics on human development: reflections on Murphy et. al. 'cannabinoid exposure and altered DNA methylation in rat and human sperm' epigenetics 2018; 13: 1208-1221

Recent data from the Kollins lab (‘Cannabinoid exposure and altered DNA methylation in rat and human sperm’ Epigenetics 2018; 13: 1208–1221) indicated epigenetic effects of cannabis use on sperm in man parallel those in rats and showed substantial shifts in both hypo- and hyper-DNA methylation with the latter predominating. This provides one likely mechanism for the transgenerational transmission of epigenomic instability with sperm as the vector. It therefore contributes important pathophysiological insights into the probable mechanisms underlying the epidemiology of prenatal cannabis exposure potentially explaining diverse features of cannabis-related teratology including effects on the neuraxis, cardiovasculature, immune stimulation, secondary genomic instability and carcinogenesis related to both adult and pediatric cancers. The potentially inheritable and therefore multigenerational nature of these defects needs to be carefully considered in the light of recent teratological and neurobehavioural trends in diverse jurisdictions such as the USA nationally, Hawaii, Colorado, Canada, France and Australia, particularly relating to mental retardation, age-related morbidity and oncogenesis including inheritable cancerogenesis. Increasing demonstrations that the epigenome can respond directly and in real time and retain memories of environmental exposures of many kinds implies that the genome-epigenome is much more sensitive to environmental toxicants than has been generally realized. Issues of long-term multigenerational inheritance amplify these concerns. Further research particularly on the epigenomic toxicology of many cannabinoids is also required.