Heat shock transcription factor 1 facilitates liver cancer progression by driving super-enhancer-mediated transcription of MYCN.

BACKGROUND: Heat shock transcription factors (HSFs) play crucial roles in the development of malignancies. However, the specific roles of HSFs in hepatocellular carcinoma (HCC) have yet to be fully elucidated. AIMS: To explore the involvement of the HSF family, particularly HSF1, in the progression and prognosis of HCC. MATERIALS & METHODS: We conducted a thorough analysis of HSF expression and copy number variations across various cancer datasets. Specifically focusing on HSF1, we examined its expression levels and prognostic implications in HCC. In vitro and in vivo experiments were carried out to evaluate the impact of HSF1 on liver cancer cell proliferation. Additionally, we utilized CUT&Tag, H3K27 acetylation enrichment, and RNA sequencing (RNA-seq) to investigate the super-enhancer (SE) regulatory landscapes of HSF1 in liver cancer cell lines. RESULTS: HSF1 expression is elevated in HCC and is linked to poor prognosis in several datasets. HSF1 stimulates liver cancer cell proliferation both in vitro and in vivo, partly through modulation of H3K27ac levels, influencing enhancer distribution. Mechanistically, our findings demonstrate that HSF1 transcriptionally activates MYCN expression by binding to its promoter and SE elements, thereby promoting liver cancer cell proliferation. Moreover, increased MYCN expression was detected in HCC tumors and correlated with unfavorable patient outcomes. DISCUSSION: Our study sheds light on previously unexplored aspects of HSF1 biology, identifying it as a transcription factor capable of shaping the epigenetic landscape in the context of HCC. Given HSF1's potential as an epigenetic regulator, targeting the HSF1-MYCN axis could open up new therapeutic possibilities for HCC treatment. CONCLUSION: The HSF1-MYCN axis constitutes a transcription-dependent regulatory mechanism that may function as both a prognostic indicator and a promising therapeutic target in liver cancer. Further exploration of this axis could yield valuable insights into novel treatment strategies for HCC.

Targeted inhibition of glycogen synthase kinase-3 using 9-ING-41 (elraglusib) enhances CD8 T-cell-reactivity against neuroblastoma cells.

The prognosis of patients with high-risk neuroblastoma remains poor, partly due to inadequate immune recognition of the tumor. Neuroblastomas display extremely low surface MHC-I, preventing recognition by cytotoxic T lymphocytes (CTLs) and contributing to an immunosuppressive tumor microenvironment. Glycogen synthase kinase-3 beta (GSK-3ß) is involved in pathways that may affect the MHC-I antigen processing and presentation pathway. We proposed that therapeutic inhibition of GSK-3ß might improve the surface display of MHC-I molecules on neuroblastoma cells, and therefore tested if targeting of GSK-3ß using the inhibitor 9-ING-41 (Elraglusib) improves MHC-I-mediated CTL recognition. We analyzed mRNA expression data of neuroblastoma tumor datasets and found that non-MYCN-amplified neuroblastomas express higher GSK-3ß levels than MYCN-amplified tumors. In non-MYCN-amplified cells SH-SY5Y, SK-N-AS and SK-N-SH 9-ING-41 treatment enhanced MHC-I surface display and the expression levels of a subset of genes involved in MHC-I antigen processing and presentation. Further, 9-ING-41 treatment triggered increased STAT1 pathway activation, upstream of antigen presentation pathways in two of the three non-MYCN-amplified cell lines. Finally, in co-culture experiments with CD8 + T cells, 9-ING-41 improved immune recognition of the neuroblastoma cells, as evidenced by augmented T-cell activation marker levels and T-cell proliferation, which was further enhanced by PD-1 immune checkpoint inhibition. Our preclinical study provides experimental support to further explore the GSK-3ß inhibitor 9-ING-41 as an immunomodulatory agent to increase tumor immune recognition in neuroblastoma.

Expansion of a neural crest gene signature following ectopic MYCN expression in sympathoadrenal lineage cells in vivo.

Neural crest cells (NCC) are multipotent migratory stem cells that originate from the neural tube during early vertebrate embryogenesis. NCCs give rise to a variety of cell types within the developing organism, including neurons and glia of the sympathetic nervous system. It has been suggested that failure in correct NCC differentiation leads to several diseases, including neuroblastoma (NB). During normal NCC development, MYCN is transiently expressed to promote NCC migration, and its downregulation precedes neuronal differentiation. Overexpression of MYCN has been linked to high-risk and aggressive NB progression. For this reason, understanding the effect overexpression of this oncogene has on the development of NCC-derived sympathoadrenal progenitors (SAP), which later give rise to sympathetic nerves, will help elucidate the developmental mechanisms that may prime the onset of NB. Here, we found that overexpressing human EGFP-MYCN within SAP lineage cells in zebrafish led to the transient formation of an abnormal SAP population, which displayed expanded and elevated expression of NCC markers while paradoxically also co-expressing SAP and neuronal differentiation markers. The aberrant NCC signature was corroborated with in vivo time-lapse confocal imaging in zebrafish larvae, which revealed transient expansion of sox10 reporter expression in MYCN overexpressing SAPs during the early stages of SAP development. In these aberrant MYCN overexpressing SAP cells, we also found evidence of dampened BMP signaling activity, indicating that BMP signaling disruption occurs following elevated MYCN expression. Furthermore, we discovered that pharmacological inhibition of BMP signaling was sufficient to create an aberrant NCC gene signature in SAP cells, phenocopying MYCN overexpression. Together, our results suggest that MYCN overexpression in SAPs disrupts their differentiation by eliciting abnormal NCC gene expression programs, and dampening BMP signaling response, having developmental implications for the priming of NB in vivo.

Preclinical spheroid models identify BMX as a therapeutic target for metastatic MYCN nonamplified neuroblastoma.

The development of targeted therapies offers new hope for patients affected by incurable cancer. However, multiple challenges persist, notably in controlling tumor cell plasticity in patients with refractory and metastatic illness. Neuroblastoma (NB) is an aggressive pediatric malignancy originating from defective differentiation of neural crest-derived progenitors with oncogenic activity due to genetic and epigenetic alterations and remains a clinical challenge for high-risk patients. To identify critical genes driving NB aggressiveness, we performed combined chromatin and transcriptome analyses on matched patient-derived xenografts (PDXs), spheroids, and differentiated adherent cultures derived from metastatic MYCN nonamplified tumors. Bone marrow kinase on chromosome X (BMX) was identified among the most differentially regulated genes in PDXs and spheroids versus adherent models. BMX expression correlated with high tumor stage and poor patient survival and was crucial to the maintenance of the self-renewal and tumorigenic potential of NB spheroids. Moreover, BMX expression positively correlated with the mesenchymal NB cell phenotype, previously associated with increased chemoresistance. Finally, BMX inhibitors readily reversed this cellular state, increased the sensitivity of NB spheroids toward chemotherapy, and partially reduced tumor growth in a preclinical NB model. Altogether, our study identifies BMX as a promising innovative therapeutic target for patients with high-risk MYCN nonamplified NB.

Joint metabolomics and transcriptomics analysis systematically reveal the impact of MYCN in neuroblastoma.

The limited understanding of the molecular mechanism underlying MYCN-amplified (MNA) neuroblastoma (NB) has hindered the identification of effective therapeutic targets for MNA NB, contributing to its higher mortality rate compared to MYCN non-amplified (non-MNA) NB. Therefore, a comprehensive analysis integrating metabolomics and transcriptomics was conducted to systematically investigate the MNA NB. Metabolomics analysis utilized plasma samples from 28 MNA NB patients and 68 non-MNA NB patients, while transcriptomics analysis employed tissue samples from 15 MNA NB patients and 37 non-MNA NB patients. Notably, joint metabolomics and transcriptomics analysis was performed. A total of 46 metabolites exhibited alterations, with 21 displaying elevated levels and 25 demonstrating reduced levels in MNA NB. In addition, 884 mRNAs in MNA NB showed significant changes, among which 766 mRNAs were higher and 118 mRNAs were lower. Joint-pathway analysis revealed three aberrant pathways involving glycerolipid metabolism, purine metabolism, and lysine degradation. This study highlights the substantial differences in metabolomics and transcriptomics between MNA NB and non-MNA NB, identifying three abnormal metabolic pathways that may serve as potential targets for understanding the molecular mechanisms underlying MNA NB.

Proteostasis perturbation of N-Myc leveraging HSP70 mediated protein turnover improves treatment of neuroendocrine prostate cancer.

N-Myc is a key driver of neuroblastoma and neuroendocrine prostate cancer (NEPC). One potential way to circumvent the challenge of undruggable N-Myc is to target the protein homeostasis (proteostasis) system that maintains N-Myc levels. Here, we identify heat shock protein 70 (HSP70) as a top partner of N-Myc, which binds a conserved "SELILKR" motif and prevents the access of E3 ubiquitin ligase, STIP1 homology and U-box containing protein 1 (STUB1), possibly through steric hindrance. When HSP70's dwell time on N-Myc is increased by treatment with the HSP70 allosteric inhibitor, STUB1 is in close proximity with N-Myc and becomes functional to promote N-Myc ubiquitination on the K416 and K419 sites and forms polyubiquitination chains linked by the K11 and K63 sites. Notably, HSP70 inhibition significantly suppressed NEPC tumor growth, increased the efficacy of aurora kinase A (AURKA) inhibitors, and limited the expression of neuroendocrine-related pathways.

The DNA methylome of pediatric brain tumors appears shaped by structural variation and predicts survival.

Structural variation heavily influences the molecular landscape of cancer, in part by impacting DNA methylation-mediated transcriptional regulation. Here, using multi-omic datasets involving >2400 pediatric brain and central nervous system tumors of diverse histologies from the Children's Brain Tumor Network, we report hundreds of genes and associated CpG islands (CGIs) for which the nearby presence of somatic structural variant (SV) breakpoints is recurrently associated with altered expression or DNA methylation, respectively, including tumor suppressor genes ATRX and CDKN2A. Altered DNA methylation near enhancers associates with nearby somatic SV breakpoints, including MYC and MYCN. A subset of genes with SV-CGI methylation associations also have expression associations with patient survival, including BCOR, TERT, RCOR2, and PDLIM4. DNA methylation changes in recurrent or progressive tumors compared to the initial tumor within the same patient can predict survival in pediatric and adult cancers. Our comprehensive and pan-histology genomic analyses reveal mechanisms of noncoding alterations impacting cancer genes.

Association with TFIIIC limits MYCN localisation in hubs of active promoters and chromatin accumulation of non-phosphorylated RNA polymerase II.

MYC family oncoproteins regulate the expression of a large number of genes and broadly stimulate elongation by RNA polymerase II (RNAPII). While the factors that control the chromatin association of MYC proteins are well understood, much less is known about how interacting proteins mediate MYC's effects on transcription. Here, we show that TFIIIC, an architectural protein complex that controls the three-dimensional chromatin organisation at its target sites, binds directly to the amino-terminal transcriptional regulatory domain of MYCN. Surprisingly, TFIIIC has no discernible role in MYCN-dependent gene expression and transcription elongation. Instead, MYCN and TFIIIC preferentially bind to promoters with paused RNAPII and globally limit the accumulation of non-phosphorylated RNAPII at promoters. Consistent with its ubiquitous role in transcription, MYCN broadly participates in hubs of active promoters. Depletion of TFIIIC further increases MYCN localisation to these hubs. This increase correlates with a failure of the nuclear exosome and BRCA1, both of which are involved in nascent RNA degradation, to localise to active promoters. Our data suggest that MYCN and TFIIIC exert an censoring function in early transcription that limits promoter accumulation of inactive RNAPII and facilitates promoter-proximal degradation of nascent RNA.

The transcriptional co-repressor Runx1t1 is essential for MYCN-driven neuroblastoma tumorigenesis.

MYCN oncogene amplification is frequently observed in aggressive childhood neuroblastoma. Using an unbiased large-scale mutagenesis screen in neuroblastoma-prone transgenic mice, we identify a single germline point mutation in the transcriptional corepressor Runx1t1, which abolishes MYCN-driven tumorigenesis. This loss-of-function mutation disrupts a highly conserved zinc finger domain within Runx1t1. Deletion of one Runx1t1 allele in an independent Runx1t1 knockout mouse model is also sufficient to prevent MYCN-driven neuroblastoma development, and reverse ganglia hyperplasia, a known pre-requisite for tumorigenesis. Silencing RUNX1T1 in human neuroblastoma cells decreases colony formation in vitro, and inhibits tumor growth in vivo. Moreover, RUNX1T1 knockdown inhibits the viability of PAX3-FOXO1 fusion-driven rhabdomyosarcoma and MYC-driven small cell lung cancer cells. Despite the role of Runx1t1 in MYCN-driven tumorigenesis neither gene directly regulates the other. We show RUNX1T1 forms part of a transcriptional LSD1-CoREST3-HDAC repressive complex recruited by HAND2 to enhancer regions to regulate chromatin accessibility and cell-fate pathway genes.

Establishment and characterization of a novel MDM2/MYCN-co-amplified neuroblastoma cell line, NBN-SHIM, established from a late recurrent stage MS tumor.

The biological heterogeneity of neuroblastoma underscores the need for an in vitro model of each molecularly defined subgroup to investigate tumorigenesis and develop targeted therapies. We have established a permanently growing cell line from a 12-year-old girl who developed a late recurrent stage MS, MDM2-amplified neuroblastoma arising in the liver and performed histological, molecular, cytogenetic, exome, and telomere analyses of the recurrent tumor and the cell line. On histology, the recurrent tumor was immunoreactive for TP53, CDKN1A, and MDM2. A molecular cytogenetic study of the recurrent tumor revealed the amplification of MDM2 but no amplification of MYCN. The established cell line, NBM-SHIM, showed amplification of both MDM2 and MYCN on double-minute chromosomes. A copy number evaluation based on exome data confirmed the finding for MYCN and MDM2 and further identified high ploidy on CDK4 and GLI2 loci in the recurrent tumor and the cell line. The telomere maintenance mechanism on the cell line is unusual in terms of the low expression of TERT despite MYCN amplification and alternative lengthening of telomeres suggested by positive value for C-circle assay and telomere contents quantitative assay. The cell line is unique because it was established from a MYCN-nonamplified, MDM2-amplified, late-relapsed stage MS neuroblastoma, and MYCN amplification was acquired during cell culture. Therefore, the cell line is a valuable tool for investigating neuroblastoma tumorigenesis and new molecular targeted therapies for disrupted ARF-TP53-MDM2 pathway and amplification of MDM2 and CDK4.

Preclinical Pharmacokinetics in Tumors and Normal Tissues of the Antigene PNA Oligonucleotide MYCN-Inhibitor BGA002.

Although MYCN has been considered an undruggable target, MYCN alterations confer poor prognosis in many pediatric and adult cancers. The novel MYCN-specific inhibitor BGA002 is an antigene peptide nucleic acid oligonucleotide covalently bound to a nuclear localization signal peptide. In the present study, we characterized the pharmacokinetics (PK) of BGA002 after single and repeated administration to mice using a novel specific enzyme-linked immunosorbent assay. BGA002 concentrations in plasma showed linear PK, with dose proportional increase across the tested dose levels and similar exposure between male and female and between intravenous and subcutaneous route of administration. Repeated dosing resulted in no accumulation in plasma. Biodistribution up to 7 days after single subcutaneous administration of [14C]-radiolabeled BGA002 showed broad tissues and organ distribution (suggesting a potential capability to reach primary tumor and metastasis in several body sites), with high concentrations in kidney, liver, spleen, lymph nodes, adrenals, and bone marrow. Remarkably, we demonstrated that BGA002 concentrates in tumors after repeated systemic administrations in three mouse models with MYCN amplification (neuroblastoma, rhabdomyosarcoma, and small-cell lung cancer), leading to a significant reduction in tumor weight. Taking into account the available safety profile of BGA002, these data support further evaluation of BGA002 in patients with MYCN-positive tumors.

Loss of Chromosome Y in Neuroblastoma Is Associated With High-Risk Disease, 11q-Deletion, and Telomere Maintenance.

Neuroblastoma (NB) is a heterogeneous childhood cancer with a slightly higher incidence in boys than girls, with the reason for this gender disparity unknown. Given the growing evidence for the involvement of loss of the Y chromosome (LoY) in male diseases including cancer, we investigated Y chromosome status in NB. Male NB tumor samples from a Swedish cohort, analyzed using Cytoscan HD SNP-microarray, were selected. Seventy NB tumors were analyzed for aneuploidy of the Y chromosome, and these data were correlated with other genetic, biological, and clinical parameters. LoY was found in 21% of the male NB tumors and it was almost exclusively found in those with high-risk genomic profiles. Furthermore, LoY was associated with increased age at diagnosis and enriched in tumors with 11q-deletion and activated telomere maintenance mechanisms. In contrast, tumors with an MYCN-amplified genomic profile retained their Y chromosome. The understanding of LoY in cancer is limited, making it difficult to conclude whether LoY is a driving event in NB or function of increased genomic instability. Gene expression analysis of Y chromosome genes in male NB tumors showed low expression of certain genes correlating with worse overall survival. KDM5D, encoding a histone demethylase stands out as an interesting candidate for further studies. LoY has been shown to impact the epigenomic layer of autosomal loci in nonreproductive tissues, and KDM5D has been reported as downregulated and/or associated with poor survival in different malignancies. Further studies are needed to explore the mechanisms and functional consequences of LoY in NB.

A MYCN-driven de-differentiation profile identifies a subgroup of aggressive retinoblastoma.

Retinoblastoma are childhood eye tumors arising from retinal precursor cells. Two distinct retinoblastoma subtypes with different clinical behavior have been described based on gene expression and methylation profiling. Using consensus clustering of DNA methylation analysis from 61 retinoblastomas, we identify a MYCN-driven cluster of subtype 2 retinoblastomas characterized by DNA hypomethylation and high expression of genes involved in protein synthesis. Subtype 2 retinoblastomas outside the MYCN-driven cluster are characterized by high expression of genes from mesodermal development, including NKX2-5. Knockdown of MYCN expression in retinoblastoma cell models causes growth arrest and reactivates a subtype 1-specific photoreceptor signature. These molecular changes suggest that removing the driving force of MYCN oncogenic activity rescues molecular circuitry driving subtype 1 biology. The MYCN-RB gene signature generated from the cell models better identifies MYCN-driven retinoblastoma than MYCN amplification and can identify cases that may benefit from MYCN-targeted therapy. MYCN drives tumor progression in a molecularly defined retinoblastoma subgroup, and inhibiting MYCN activity could restore a more differentiated and less aggressive tumor biology.

Study on the role of MYCN in retinoblastoma by inhibiting p53 and activating wnt/ßcatenin/Fra-1 signaling pathway by reducing DKK3.

Retinoblastoma (RB) is a pediatric malignancy, typically diagnosed at birth or during early childhood. The pathogenesis of RB is marked by the amplification of the Basic Helix-Loop-Helix (BHLH) Transcription Factor MYCN, which serves as a transcriptional regulator capable of binding to Dickkopf 3 (DKK3). However, the precise role of DKK3 in the malignant progression of RB cells caused by MYCN remains elusive. In the present study, the expression of MYCN was either overexpressed or interfered in RB cells. Subsequently, the expression level of DKK3 was assessed through quantitative real-time polymerase chain reaction and western blot analysis. Cell proliferation was evaluated using the Cell Counting Kit-8 assay and 5-ethynyl-2'-deoxyuridine staining, while cell cycle progression and apoptosis were analyzed by flow cytometry and western blot analysis, respectively. Additionally, the expression of proteins involved in the Wnt/ß-catenin/Fra-1/p53 signaling pathway was evaluated via western blot analysis. To gain further insights, Wnt agonists and the P53 inhibitor PFT-α were introduced into exploration. The current investigation revealed a negative correlation between the expression levels of MYCN and DKK3 in RB cells. Additionally, DKK3 overexpression inhibited cell proliferation, promoted cell apoptosis, and arrested cell cycle in RB cells with high expression of MYCN. Moreover, enhanced DKK3 expression inhibited proliferation, promoted cell cycle arrest and apoptosis of RB cells by modulating the wnt/ßcatenin/Fra-1/p53 signaling pathway. Furthermore, in vivo experiments revealed that overexpression of DKK3 inhibits the growth of RB tumors. Collectively, our findings elucidate that MYCN stimulates the Wnt/ß-catenin/Fra-1 pathway by suppressing DKK3 expression, ultimately suppressing p53 activity and contributing to malignant progression of RB.

Application of the FISH method and high-density SNP arrays to assess genetic changes in neuroblastoma-research by one institute.

Neuroblastoma is the most common extracranial solid tumor in children. Amplification of the MYCN gene has been observed in approximately 20%-30% of tumors. It is strongly correlated with advanced-stage disease, rapid tumor progression, resistance to chemotherapy and poor outcomes independent of patient age and stage of advanced disease. MYCN amplification identifies high-risk patients. To assess neuroblastoma tumors with MYCN amplification we used paraffin-embedded tissue sections in 57 patients and intraoperative tumor imprints in 10 patients by fluorescence in situ hybridization (FISH). Positive results for MYCN amplification have been observed in twelve patients' paraffin-embedded tissue sections and in three patients' intraoperative tumor imprints, which represents 22.4% of all patients tested in the analysis. Fluorescence in situ hybridization is a highly sensitive and useful technique for detecting MYCN amplification on paraffin-embedded tissue sections of neuroblastoma tumors and intraoperative tumor imprints thus facilitating therapeutic decisions based on the presence or absence of this important biologic marker. The presence of structural changes, regardless of MYCN gene amplification status, influences the clinical behavior of neuroblastoma. High-Density SNP Arrays have emerged as the perfect tools for detecting these changes due to their exceptional accuracy, sensitivity and ability to analyze copy number and allele information. Consequently, they are proven to be highly valuable in the genomic diagnosis of immature neuroectodermal tumors.

Aurora Kinase A Is Overexpressed in Human Retinoblastoma and Correlates with Histopathologic High-Risk Factors: Implications for Targeted Therapy.

Retinoblastoma (RB) is an intraocular malignancy initiated by loss of RB1 function and/or dysregulation of MYCN oncogene. RB is primarily treated with chemotherapy; however, systemic toxicity and long-term adverse effects remain a significant challenge necessitating the identification of specific molecular targets. Aurora kinase A (AURKA), a critical cell cycle regulator, contributes to cancer pathogenesis, especially in RB1-deficient and MYCN-dysregulated tumors. The current immunohistochemistry study in patient specimens (n = 67) indicated that AURKA is overexpressed in RB, and this elevated expression correlates with one or more histopathologic high-risk factors, such as tumor involvement of the optic nerve, choroid, sclera, and/or anterior segment. More specifically, AURKA is ubiquitously expressed in most advanced-stage RB tumors that show a suboptimal response to chemotherapy. shRNA-mediated depletion/pharmacologic inhibition studies in cell lines, patient-derived cells, in vivo xenografts, and enucleated patient specimens confirmed that RB cells are highly sensitive to a lack of functional AURKA. In addition, AURKA and N-myc proto-oncogene protein (MYCN) associate with each other to regulate their levels in RB cells. Overall, these results demonstrate a previously unknown up-regulation of AURKA in RB, facilitated by its crosstalk with MYCN. The elevated levels of this kinase may indicate unfavorable prognosis in tumors refractory to chemotherapy. This study provides a rationale and confirms that therapeutic targeting of elevated AURKA in RB could be a potential treatment approach.

The TERT Promoter is Polycomb-Repressed in Neuroblastoma Cells with Long Telomeres.

Acquiring a telomere maintenance mechanism is a hallmark of high-risk neuroblastoma and commonly occurs by expressing telomerase (TERT). Telomerase-negative neuroblastoma has long telomeres and utilizes the telomerase-independent alternative lengthening of telomeres (ALT) mechanism. Conversely, no discernable telomere maintenance mechanism is detected in a fraction of neuroblastoma with long telomeres. Here, we show, unlike most cancers, DNA of the TERT promoter is broadly hypomethylated in neuroblastoma. In telomerase-positive neuroblastoma cells, the hypomethylated DNA promoter is approximately 1.5 kb. The TERT locus shows active chromatin marks with low enrichment for the repressive mark, H3K27me3. MYCN, a commonly amplified oncogene in neuroblstoma, binds to the promoter and induces TERT expression. Strikingly, in neuroblastoma with long telomeres, the hypomethylated region spans the entire TERT locus, including multiple nearby genes with enrichment for the repressive H3K27me3 chromatin mark. Furthermore, subtelomeric regions showed enrichment of repressive chromatin marks in neuroblastomas with long telomeres relative to those with short telomeres. These repressive marks were even more evident at the genic loci, suggesting a telomere position effect (TPE). Inhibiting H3K27 methylation by three different EZH2 inhibitors induced the expression of TERT in cell lines with long telomeres and H3K27me3 marks in the promoter region. EZH2 inhibition facilitated MYCN binding to the TERT promoter in neuroblastoma cells with long telomeres. Taken together, these data suggest that epigenetic regulation of TERT expression differs in neuroblastoma depending on the telomere maintenance status, and H3K27 methylation is important in repressing TERT expression in neuroblastoma with long telomeres. SIGNIFICANCE: The epigenetic landscape of the TERT locus is unique in neuroblastoma. The DNA at the TERT locus, unlike other cancer cells and similar to normal cells, are hypomethylated in telomerase-positive neuroblastoma cells. The TERT locus is repressed by polycomb repressive complex-2 complex in neuroblastoma cells that have long telomeres and do not express TERT. Long telomeres in neuroblastoma cells are also associated with repressive chromatin states at the chromosomal termini, suggesting TPE.

N-MYC impairs innate immune signaling in high-grade serous ovarian carcinoma.

High-grade serous ovarian cancer (HGSC) is a challenging disease, especially for patients with immunologically "cold" tumors devoid of tumor-infiltrating lymphocytes (TILs). We found that HGSC exhibits among the highest levels of MYCN expression and transcriptional signature across human cancers, which is strongly linked to diminished features of antitumor immunity. N-MYC repressed basal and induced IFN type I signaling in HGSC cell lines, leading to decreased chemokine expression and T cell chemoattraction. N-MYC inhibited the induction of IFN type I by suppressing tumor cell-intrinsic STING signaling via reduced STING oligomerization, and by blunting RIG-I-like receptor signaling through inhibition of MAVS aggregation and localization in the mitochondria. Single-cell RNA sequencing of human clinical HGSC samples revealed a strong negative association between cancer cell-intrinsic MYCN transcriptional program and type I IFN signaling. Thus, N-MYC inhibits tumor cell-intrinsic innate immune signaling in HGSC, making it a compelling target for immunotherapy of cold tumors.

MYC Family Amplification Dictates Sensitivity to BET Bromodomain Protein Inhibitor Mivebresib (ABBV075) in Small-Cell Lung Cancer.

Small-cell lung cancer (SCLC) accounts for nearly 15% of all lung cancers. Although patients respond to first-line therapy readily, rapid relapse is inevitable, with few treatment options in the second-line setting. Here, we describe SCLC cell lines harboring amplification of MYC and MYCN but not MYCL1 or non-amplified MYC cell lines exhibit superior sensitivity to treatment with the pan-BET bromodomain protein inhibitor mivebresib (ABBV075). Silencing MYC and MYCN partially rescued SCLC cell lines harboring these respective amplifications from the antiproliferative effects of mivebresib. Further characterization of genome-wide binding of MYC, MYCN, and MYCL1 uncovered unique enhancer and epigenetic preferences. Implications: Our study suggests that chromatin landscapes can establish cell states with unique gene expression programs, conveying sensitivity to epigenetic inhibitors such as mivebresib.