N-myc Gene Expression Research Articles

Multi-omics revealed that ELAVL3 regulates MYCN in neuroblastoma via immunogenic cell death: Risk stratification and experimental research

Neuroblastoma (NB), a common and highly lethal malignant disease in pediatrics, still lacks an effective therapeutic approach that addresses all conditions. Immunogenic Cell Death (ICD) plays a crucial role in tumor cell death and triggers a potent anti-tumor immune response. In this study, we report an ICD-related index (ICDR-Index) in NB through various machine learning methodologies, utilizing bulk transcriptome data from 1244 NB samples and 16 scRNA-seq datasets. Our results showed that the ICDR-Index could accurately identify different risk subtypes of patients with NB and provide predictive value for prognosis. Importantly, we found that high-risk patients with NB exhibited significantly poor overall survival (OS) rates, adverse clinical phenotypes, poor immune cell infiltration, and low sensitivity to immunotherapy. Furthermore, we identified ELAVL3 as a key gene within the ICDR-Index, where high expression levels were associated with malignancy and poor OS in NB. Additionally, targeted silencing of ELAVL3 down-regulated MYCN gene expression and reduced the malignancy of NB cells. Notably, the si-ELAVL3-transfected NB cells enhanced the anti-tumor activity of NK cells. Collectively, this study offers avenues for predicting the risk stratification of patients with NB and reveals a potential mechanism by which ELAVL3 regulates NB cell death.

Unraveling the glycosphingolipid metabolism by leveraging transcriptome-weighted network analysis on neuroblastic tumors

BackgroundGlycosphingolipids (GSLs) are membrane lipids composed of a ceramide backbone linked to a glycan moiety. Ganglioside biosynthesis is a part of the GSL metabolism, which involves sequential reactions catalyzed by specific enzymes that in part have a poor substrate specificity. GSLs are deregulated in cancer, thus playing a role as potential biomarkers for personalized therapy or subtype classification. However, the analysis of GSL profiles is complex and requires dedicated technologies, that are currently not included in the commonly utilized high-throughput assays adopted in contexts such as molecular tumor boards.MethodsIn this study, we developed a method to discriminate the enzyme activity among the four series of the ganglioside metabolism pathway by incorporating transcriptome data and topological information of the metabolic network. We introduced three adjustment options for reaction activity scores (RAS) and demonstrated their application in both exploratory and comparative analyses by applying the method on neuroblastic tumors (NTs), encompassing neuroblastoma (NB), ganglioneuroblastoma (GNB), and ganglioneuroma (GN). Furthermore, we interpreted the results in the context of earlier published GSL measurements in the same tumors.ResultsBy adjusting RAS values using a weighting scheme based on network topology and transition probabilities (TPs), the individual series of ganglioside metabolism can be differentiated, enabling a refined analysis of the GSL profile in NT entities. Notably, the adjustment method we propose reveals the differential engagement of the ganglioside series between NB and GNB. Moreover, MYCN gene expression, a well-known prognostic marker in NTs, appears to correlate with the expression of therapeutically relevant gangliosides, such as GD2. Using unsupervised learning, we identified subclusters within NB based on altered GSL metabolism.ConclusionOur study demonstrates the utility of adjusting RAS values in discriminating ganglioside metabolism subtypes, highlighting the potential for identifying novel cancer subgroups based on sphingolipid profiles. These findings contribute to a better understanding of ganglioside dysregulation in NT and may have implications for stratification and targeted therapeutic strategies in these tumors and other tumor entities with a deregulated GSL metabolism.

DNp73 enhances tumor progression and immune evasion in multiple myeloma by targeting the MYC and MYCN pathways.

Multiple myeloma (MM) is an incurable hematological malignancy with high chromosome instability and heavy dependence on the immunosuppressive bone marrow microenvironment. P53 mutations are adverse prognostic factors in MM; however, clinically, some patients without P53 mutations also exhibit aggressive disease progression. DNp73, an inhibitor of TP53 tumor suppressor family members, drives drug resistance and cancer progression in several solid malignancies. Nevertheless, the biological functions of DNp73 and the molecular mechanisms in myelomagenesis remain unclear. The effects of DNp73 on proliferation and drug sensitivity were assessed using flow cytometry and xenograft models. To investigate the mechanisms of drug resistance, RNA-seq and ChIP-seq analyses were performed in MM cell lines, with validation by Western blot and RT-qPCR. Immunofluorescence and transwell assays were used to assess DNA damage and cell invasion in MM cells. Additionally, in vitro phagocytosis assays were conducted to confirm the role of DNp73 in immune evasion. Our study found that activation of NF-κB-p65 in multiple myeloma cells with different p53 mutation statuses upregulates DNp73 expression at the transcriptional level. Forced expression of DNp73 promoted aggressive proliferation and multidrug resistance in MM cells. Bulk RNA-seq analysis was conducted to assess the levels of MYCN, MYC, and CDK7. A ChIP-qPCR assay was used to reveal that DNp73 acts as a transcription factor regulating MYCN gene expression. Bulk RNA-seq analysis demonstrated increased levels of MYCN, MYC, and CDK7 with forced DNp73 expression in MM cells. A ChIP-qPCR assay revealed that DNp73 upregulates MYCN gene expression as a transcription factor. Additionally, DNp73 promoted immune evasion of MM cells by upregulating MYC target genes CD47 and PD-L1. Blockade of the CD47/SIRPα and PD-1/PD-L1 signaling pathways by the SIRPα-Fc fusion protein IMM01 and monoclonal antibody atezolizumab significantly restored the anti-MM activity of macrophages and T cells in the microenvironment, respectively. In summary, our study demonstrated for the first time that the p53 family member DNp73 remarkably induces proliferation, drug resistance, and immune escape of myeloma cells by directly targeting MYCN and regulating the MYC pathway. The oncogenic function of DNp73 is independent of p53 status in MM cells. These data contribute to a better understanding of the function of TP53 and its family members in tumorigenesis. Moreover, our study clarified that DNp73 overexpression not only promotes aggressive growth of tumor cells but, more importantly, promotes immune escape of MM cells through upregulation of immune checkpoints. DNp73 could serve as a biomarker for immunotherapy targeting PD-L1 and CD47 blockade in MM patients.

Novel Auger-Electron-Emitting 191Pt-Labeled Pyrrole-Imidazole Polyamide Targeting MYCN Increases Cytotoxicity and Cytosolic dsDNA Granules in MYCN-Amplified Neuroblastoma.

Auger electrons can cause nanoscale physiochemical damage to specific DNA sites that play a key role in cancer cell survival. Radio-Pt is a promising Auger-electron source for damaging DNA efficiently because of its ability to bind to DNA. Considering that the cancer genome is maintained under abnormal gene amplification and expression, here, we developed a novel 191Pt-labeled agent based on pyrrole-imidazole polyamide (PIP), targeting the oncogene MYCN amplified in human neuroblastoma, and investigated its targeting ability and damaging effects. A conjugate of MYCN-targeting PIP and Cys-(Arg)3-coumarin was labeled with 191Pt via Cys (191Pt-MYCN-PIP) with a radiochemical purity of >99%. The binding potential of 191Pt-MYCN-PIP was evaluated via the gel electrophoretic mobility shift assay, suggesting that the radioagent bound to the DNA including the target sequence of the MYCN gene. In vitro assays using human neuroblastoma cells showed that 191Pt-MYCN-PIP bound to DNA efficiently and caused DNA damage, decreasing MYCN gene expression and MYCN signals in in situ hybridization analysis, as well as cell viability, especially in MYCN-amplified Kelly cells. 191Pt-MYCN-PIP also induced a substantial increase in cytosolic dsDNA granules and generated proinflammatory cytokines, IFN-α/β, in Kelly cells. Tumor uptake of intravenously injected 191Pt-MYCN-PIP was low and its delivery to tumors should be improved for therapeutic application. The present results provided a potential strategy, targeting the key oncogenes for cancer survival for Auger electron therapy.

A Review of the Regulatory Mechanisms of N-Myc on Cell Cycle.

Neuroblastoma has obvious heterogeneity. It is one of the few undifferentiated malignant tumors that can spontaneously degenerate into completely benign tumors. However, for its high-risk type, even with various intensive treatment options, the prognosis is still unsatisfactory. At the same time, a large number of research data show that the abnormal amplification and high-level expression of the MYCN gene are positively correlated with the malignant progression, poor prognosis, and mortality of neuroblastoma. In this context, this article explores the role of the N-Myc, MYCN gene expression product on its target genes related to the cell cycle and reveals its regulatory network in promoting tumor proliferation and malignant progression. We hope it can provide ideas and direction for the research and development of drugs targeting N-Myc and its downstream target genes.

Dynamic plasticity of prostate cancer intermediate cells during androgen receptor-targeted therapy.

Treatment-emergent small cell neuroendocrine prostate cancer (t-SCNC) is associated with an epithelial lineage switch from an androgen receptor (AR)-positive to neuroendocrine (NE)-marker-positive status. Understanding the potential for reversibility of this aggressive disease state has been hampered by the paucity of models suitable for studying rate-limiting, transitional, or intermediate tumor cell subpopulations. We define a dual reporter model that measures acute transcriptional changes in response to castration or AR targeting agents. We identify steady-state transcriptional heterogeneity in AR and NE biomarkers, including intermediate subpopulations that are coordinately high for prostate-specific antigen (PSA) and neuron-specific enoclase (NSE) promoter activity. In the presence of castration or AR inhibitors, intermediate cells were necessary and sufficient for therapy-induced conversion of human PC cells to an NSE-high transcriptional status. Using hormone add-back studies, treatment-induced PSA-NSE transcriptional plasticity was reversible in PTEN-deficient PC cells but not in the presence of secondary genetic driver genes, including MYCN.

An In Vitro Study of Saffron Carotenoids: The Effect of Crocin Extracts and Dimethylcrocetin on Cancer Cell Lines.

Crocus sativus L. has various pharmacological properties, known for over 3600 years. These properties are attributed mainly to biologically active substances, which belong to the terpenoid group and include crocins, picrocrocin and safranal. The aim of the current work was to examine the effects of crocins (CRCs) and their methyl ester derivate dimethylcrocetin (DMCRT) on glioblastoma and rhabdomyosarcoma cell lines, in terms of cytotoxicity and gene expression, implicated in proapoptotic and cell survival pathways. Cell cytotoxicity was assessed with Alamar Blue fluorescence assay after treatment with saffron carotenoids for 24, 48 and 72 h and concentrations ranging from 22.85 to 0.18 mg/mL for CRCs and 11.43 to 0.09 mg/mL for DMCRT. In addition, BAX, BID, BCL2, MYCN, SOD1, and GSTM1 gene expression was studied by qRT-PCR analysis. Both compounds demonstrated cytotoxic effects against glioblastoma and rhabdomyosarcoma cell lines, in a dose- and time-dependent manner. They induced apoptosis, via BAX and BID upregulation, MYCN and BCL-2, SOD1, GSTM1 downregulation. The current research denotes the possible anticancer properties of saffron carotenoids, which are considered safe phytochemicals, already tested in clinical trials for their health promoting properties.

Non-Genomic Control of Dynamic MYCN Gene Expression in Liver Cancer.

Upregulated MYCN gene expression is restricted to specialized cell populations such as EpCAM+ cancer stem cells in liver cancer, regardless of DNA amplification and mutation. Here, we reviewed the role of MYCN gene expression in liver homeostasis, regeneration, and tumorigenesis, and discussed the potential non-genomic mechanisms involved in controlling MYCN gene expression in liver cancer, with a focus on inflammation-mediated signal transduction and microRNA-associated post-transcriptional regulation. We concluded that dynamic MYCN gene expression is an integrated consequence of multiple signals in the tumor microenvironment, including tumor growth-promoting signals, lipid desaturation-mediated endoplasmic reticulum stress adaptation signals, and tumor suppressive miRNAs, making it a potential predictive biomarker of tumor stemness and plasticity. Therefore, understanding and tracing the dynamic changes and functions of MYCN gene expression will shed light on the origin of liver tumorigenesis at the cellular level and the development of novel therapeutic and diagnostic strategies for liver cancer treatment.

Exploring and Targeting the Tumor Immune Microenvironment of Neuroblastoma.

Pediatric neuroblastoma is a heterogenous disease that accounts for significant morbidity and mortality in children. Deep genomic and transcriptomic profiling of patient tumors has revealed a low mutational burden and a paucity of therapeutic targets. Furthermore, different molecular subtypes, such as MYCN amplification, have been associated with adverse outcomes. Using whole transcriptome sequencing, we previously explored the immune microenvironment of neuroblastoma subtypes and discovered its association with clinical outcome. Specifically, we found that patients with tumors infiltrated by higher levels of cytotoxic lymphocytes had a better overall survival. Additionally, we found that a high MYCN gene expression signature in MYCN-non-amplified tumors is an independent predictor of adverse outcome. However, signatures of tumor infiltrating cytotoxic immune cells in this subtype of tumors predict an improved outcome. While this is clinically informative, it does not provide a full picture of the dynamics underlying the biology of tumor immune microenvironment and how to use this information to improve patient outcomes. Here, we highlight our previous work and current approaches using immunotherapy in neuroblastoma and explore our current understanding of the immune biology of these tumors. We further describe how this correlates with patient outcome, and how this information can be used to develop novel immunotherapeutic strategies for pediatric patients with neuroblastoma.

Enhanced recombinant C-terminal domain of gli2 gene expression can improve wound healing through promoting cdc25b and N-Myc genes expression

Wound is an important cause of morbidity and mortality in population because it can be caused by many factors like events, illness and surgery. Identification of wound healing factors and their role can be useful for effective treatment. GLI2 as an important activator of SHH signaling pathway should be further investigated. In this study we focused on the effect of a recombinant derivative of GLI2 gene on the progression of wound healing and expression of cdc25a and Myc genes as two transcription factors involved in wound healing pathways.A fragment containing coding sequence of functional domains of C-terminal of GLI2 protein was cloned in pcDNA3.1+ plasmid. A 1 cm diameter circular area wound up on the back of the one group of wistar albino rats. In the next step, purified recombinant plasmid containing GLI2 C-terminal domains coding sequence, was injected subcutaneously around the wound similar to what we do about the DNA vaccine strategy. Wound area was following during 7 days and all results was documented by digital pictures. Peripheral tissue of the wounds was dissected and studied for cdc25a and N-Myc genes expression real-time RT-PCR analysis. Total of wound scare was dissected after 7 days since injection. These biopsies were subjected to RNA extraction and Real-Time PCR analysis for expression analysis of Gli2, N-myc and cdc25b genes. In addition, a piece of every biopsy was analyzed by immunohistochemistry method for detection and analysis of gli2 protein.Our results showed a significant improvement in wound healing treatment by recombinant injected pcDNA3.1/GLI compared with the control group. Also, the affected tissue of rats that express recombinant gli2, had significant increasing of N-myc and cdc25b gene expression, which leads to acceleration of cell proliferation during wound healing.GLI2 protein is the major activator of SHH pathway and this signaling route has a vital role in renewing and repair of tissues.GLI2 protein can be consider as a potent factor in wound healing. Especially GLI2 as a transcription factor can regulates the expression of many proteins that play important role in healing process. Our results support the function of some of GLI motives in gene expression separately. Overexpression of N-Myc and cdc25b genes compared with the control group, can indirectly explain the function mechanism of GLI2 in the tissue repair.

Lipid desaturation-associated endoplasmic reticulum stress regulates MYCN gene expression in hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is the second leading cause of cancer-related deaths worldwide due to its high rate of recurrence, in part because of cancer stem cell (CSC)-dependent “field cancerization”. Recently, we identified that the oncogene v-myc avian myelocytomatosis viral oncogene neuroblastoma derived homolog (MYCN) marked CSC-like subpopulations in heterogeneous HCC and served as a therapeutic target and prognostic marker for HCC. In this study, we explored the molecular basis of upregulated MYCN gene expression in HCC cells. Liquid chromatograph time-of-flight mass spectrometry-based metabolome analysis demonstrated that the content of unsaturated fatty acids was increased in MYCN high expression (MYCNhigh) CSC-like HCC cells. Inhibition of lipid desaturation using either the chemical inhibitor or siRNA/shRNA against stearoyl-CoA desaturase-1 (SCD1) suppressed cell proliferation as well as MYCN gene expression in MYCNhigh HCC cells, grown as both monolayer and spheres. Further mechanistic study using RNA-seq based transcriptome analysis revealed that endoplasmic reticulum (ER) stress related signaling networks such as endocannabinoid cancer inhibition pathway were under the control of SCD1 in MYCNhigh HCC cells. Furthermore, the expression of ER stress-inducible transcription suppressor cyclic AMP-dependent transcription factor (ATF3) was downregulated in MYCNhigh CSC-like HCC cells and CSC-rich spheroids, which was upregulated by inhibition of lipid desaturation or treatment with acyclic retinoid (ACR). Lipid profiling using NMR spectroscopy revealed that the ACR dramatically reduced the content of unsaturated fatty acids in HCC cells. The chemical inducer of ER stress inhibited MYCN gene expression, while the chemical inhibitor of ER stress or knockdown of ATF3 gene expression partially rescued the suppression of MYCN gene expression by ACR in MYCNhigh HCC cells. These data suggested that lipid desaturation-mediated ER stress signaling regulates MYCN gene expression in HCC cells and serves as a promising therapeutic target for the treatment and prevention of HCC.

Clinical analysis of neuroblastoma with pulmonary or pleural involvement

Objective To analyze the clinical characteristics of children with neuroblastoma (NB) complica-ted with lung or pleural metastasis, further to explore the correlation between characteristics and short-term outcome of NB, so as to provide a basis for clinical diagnosis and treatment. Methods A retrospective analysis was performed concerning the age of onset, clinical features, treatment and outcome of 36 patients with NB who were admitted at Blood Tumor Center, Beijing Children′s Hospital of Capital Medical University from December 2007 to December 2017.The diagnostic criteria, therapeutic regimen and therapeutic efficacy criteria of the enrolled children were all based on the NB protocol of Beijing Children′s Hospital of Capital Medical University (BCH-NB-2007), the clinical stage was based on international clinical stage of neuroblastoma (INSS stage), and stratified treatment was conducted according to the BCH-NB risk grouping standard.The follow-up period lasted till October 31, 2018. Results (1)The common clinical features of grouped children: 36 patients were selected into the group, accounted for 5.99% (36/601 cases) in total hospitalized NB children, they were less than 10 years old, 10 cases under 18 months, and the median age was 29.5 months (9-105 months); 20 cases were male, and 16 cases were female; the primary tumor was located in the retroperitoneal site in 19 cases, accounting for 52.78%, 9 cases in adrenal site, accounting for 25.00%, and 8 cases in mediastinal site, accounting for 22.22%.Risk groups: 29 cases were in high-risk group, 6 cases were in medium-risk group and 1 case was in low-risk group.The main symptoms were of pain onset in 8 cases, fever in 6 cases, local mass in 6 cases, abdominal mass in 4 cases, mediastinal mass in 3 cases, paleness in 3 cases, subcutaneous nodules in 2 cases, abdominal distension in 2 cases, lower limb swelling in 1 case, and diarrhea in 1 case. Among them, 16 cases had respiratory system symptoms first, accounting for 44.4%.(2)Laboratory examination: there were 35 patients of neuron-specific enolase (NSE) ≥25 μg/L on the initial diagnosis, of which 11 cases were more than 370 μg/L, the value of serum lactate dehydrogenase (LDH) ≥717.5 U/L in 25 patients, accounting for 69.44%, and 10 cases were accompanied by N-myc gene amplification.(3)Imaging examination: on the first diagnosis, chest/abdomen CT showed 75.75%(24/33 cases) of pleural or lung involvement, PET-CT showed 81.8% (27/33 cases) of pleural or lung involvement, B-ultrasound showed 41.67%(5/12 cases) of pleural or lung involvement; 3 imaging examinations showed: 1 positive in 16 cases, 2 positive in 16 cases, and 3 positive in 4 cases.(4)Comparison of clinical features of pleural and pulmonary involvement: among the 30 children with pleural involvement, 6 cases had respiratory symptoms, 3 cases had respiratory symptoms on the 6 cases with pulmonary involvement only, and 4 cases with pleural and pulmonary involvement had no respiratory symptoms at first diagnosis.(5)Treatment and outcome: 2 cases died because of critical condition after diagnosis, 5 cases didn′t receive the law treatment, 29 cases accepted law stratification treatment, among them, 1 case in low risk group, INSS-Ⅳ, alleviate current (CR); 4 cases in the moderate group, INSS-Ⅳ, CR in 2 cases, partial response (PR) in 1 case, progress in 1 case, new tumor foci occurring after chemotherapy discontinuation for 13 months. Twenty-four cases were in the high-risk group, event occurred in 7 cases (29.17%) of them, 1 case had progression by postoperative evaluation, 4 cases of progression at 1.5, 2.0, 3.0 and 6.0 months after cessation of chemotherapy, and 2 cases had recurrence at 11 and 17 months after cessation of chemotherapy.Overall survival rate (OS) was 41.4% for all children analyzed by Kaplan-Merier, and 32.9% of them were predicted to have 3-year event-free survival. Conclusions Children with pulmonary or pleural metastasis of neuroblastoma have no specific respiratory symptoms.CT scan might be a useful method for diagnosing the group Ⅳ children with pulmonary or pleural metastasis of neuroblastoma.Moreover, there seemed to be no significant correlation between the N-myc gene expression and survival prognosis of these children. Key words: Neuroblastoma; Pleural; Pulmonary; Clinical feature; Prognosis

Cancer-related mRNA expression analysis using a novel flow cytometry-based assay.

Cancer-related gene expression data mostly originate from unfractionated bulk samples, leading to "expression averaging" of heterogeneous populations. Multicolor flow cytometry (FCM) may distinguish heterogeneous populations based on the phenotypic characterization of single-cells, but is not applicable for RNA targets. Here, we evaluated the PrimeFlow™ RNA assay, a novel FCM-based assay designed to measure gene expressions, in two cancer entities with high and low RNA target levels. Neuroblastoma (NB) cell lines were studied for MYCN gene expression by PrimeFlow™ and compared with the gold standard, RT-qPCR. Dilution series of NB cells (0.10-11%) were prepared to evaluate performance in small cell populations. Diagnostic material of de novo acute myeloid leukemia (AML) patients was used to measure Wilms' tumor 1 (WT1) expression in bulk leukemic cells and rare subsets, e.g. leukemic stem cells (LSCs). FCM analysis was performed on a FACSCanto II (BD Biosciences) using Infinicyt™ (Cytognos® ) for data analysis. mRNA expression was reported by normalized mean fluorescence intensity (MFI) values and staining indices. MYCN mRNA quantified by PrimeFlow™ significantly correlated with RT-qPCR and remained detectable in small (0.1%) populations. Using PrimeFlowTM , WT1 levels were shown to be significantly higher in AML patient samples with WT1 overexpression, previously defined by RT-qPCR. Moreover, WT1 overexpression was distinguishable between heterogeneous cell populations and remained measurable in rare LSCs. PrimeFlow™ is a sensitive technique to investigate mRNA expressions, with high concordance to RT-qPCR. High (MYCN) and subtle (WT1) overexpressed mRNA targets can be quantified in heterogeneous and rare subpopulations e.g. LSCs. © 2017 International Clinical Cytometry Society.

Abstract LB-080: The histone methyltransferase DOT1L promotes neuroblastoma by regulating gene transcription

Abstract Myc oncoproteins exert tumorigenic effects by regulating the expression of target oncogenes. Histone H3 lysine 79 (H3K79) methylation at Myc-responsive elements of target gene promoters is a strict prerequisite for Myc-induced transcriptional activation. DOT1L is the only known histone methyltransferase that catalyses H3K79 methylation. Here, we showed that N-Myc up-regulated DOT1L mRNA and protein expression by binding to the DOT1L gene promoter. Knocking down DOT1L reduced mRNA and protein expression of the N-Myc target genes ODC1 and E2F2. DOT1L bound to the Myc Box II domain of N-Myc protein, and knocking down DOT1L reduced histone H3K79 methylation and N-Myc protein binding at the ODC1 and E2F2 gene promoters and reduced neuroblastoma cell proliferation. Treatment with the small molecule DOT1L inhibitor SGC0946 reduced H3K79 methylation and proliferation of MYCN gene-amplified neuroblastoma cells. In mice xenografted with neuroblastoma cells stably expressing doxycycline-inducible DOT1L small hair-pin RNA, ablating DOT1L expression with doxycycline significantly reduced ODC1 and E2F2 expression, reduced tumor progression and improved overall survival. In addition, high levels of DOT1L gene expression in human neuroblastoma tissues correlated with high levels of MYCN, ODC1 and E2F2 gene expression, and independently correlated with poor patient survival. Taken together, our data identify DOT1L as a novel co-factor in N-Myc-mediated transcriptional activation of target genes and neuroblastoma oncogenesis, and DOT1L inhibitors as novel anticancer agents against MYCN-amplified neuroblastoma. Citation Format: Matthew Wong, Andrew Tee, Giorgio Milazzo, Jessica Bell, Stefan Hüttelmaier, Patsie Polly, Giovanni Perini, Christopher J. Scarlett, Tao Liu. The histone methyltransferase DOT1L promotes neuroblastoma by regulating gene transcription [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr LB-080. doi:10.1158/1538-7445.AM2017-LB-080

The Histone Methyltransferase DOT1L Promotes Neuroblastoma by Regulating Gene Transcription.

Myc oncoproteins exert tumorigenic effects by regulating expression of target oncogenes. Histone H3 lysine 79 (H3K79) methylation at Myc-responsive elements of target gene promoters is a strict prerequisite for Myc-induced transcriptional activation, and DOT1L is the only known histone methyltransferase that catalyzes H3K79 methylation. Here, we show that N-Myc upregulates DOT1L mRNA and protein expression by binding to the DOT1L gene promoter. shRNA-mediated depletion of DOT1L reduced mRNA and protein expression of N-Myc target genes ODC1 and E2F2 DOT1L bound to the Myc Box II domain of N-Myc protein, and knockdown of DOT1L reduced histone H3K79 methylation and N-Myc protein binding at the ODC1 and E2F2 gene promoters and reduced neuroblastoma cell proliferation. Treatment with the small-molecule DOT1L inhibitor SGC0946 reduced H3K79 methylation and proliferation of MYCN gene-amplified neuroblastoma cells. In mice xenografts of neuroblastoma cells stably expressing doxycycline-inducible DOT1L shRNA, ablating DOT1L expression with doxycycline significantly reduced ODC1 and E2F2 expression, reduced tumor progression, and improved overall survival. In addition, high levels of DOT1L gene expression in human neuroblastoma tissues correlated with high levels of MYCN, ODC1, and E2F2 gene expression and independently correlated with poor patient survival. Taken together, our results identify DOT1L as a novel cofactor in N-Myc-mediated transcriptional activation of target genes and neuroblastoma oncogenesis. Furthermore, they characterize DOT1L inhibitors as novel anticancer agents against MYCN-amplified neuroblastoma. Cancer Res; 77(9); 2522-33. ©2017 AACR.

A Myc Activity Signature Predicts Poor Clinical Outcomes in Myc-Associated Cancers.

Myc transcriptional activity is frequently deregulated in human cancers, but a Myc-driven gene signature with prognostic ability across multiple tumor types remains lacking. Here, we selected 18 Myc-regulated genes from published studies of Myc family targets in epithelial ovarian cancer (EOC) and neuroblastoma. A Myc family activity score derived from the 18 genes was correlated to MYC/MYCN/MYCL1 expression in a panel of 35 cancer cell lines. The prognostic ability of this signature was evaluated in neuroblastoma, medulloblastoma, diffuse large B-cell lymphoma (DLBCL), and EOC microarray gene expression datasets using Kaplan-Meier and multivariate Cox regression analyses and was further validated in 42 primary neuroblastomas using qPCR. Cell lines with high MYC, MYCN, and/or MYCL1 gene expression exhibited elevated expression of the signature genes. Survival analysis showed that the signature was associated with poor outcome independently of well-defined prognostic factors in neuroblastoma, breast cancer, DLBCL, and medulloblastoma. In EOC, the 18-gene Myc activity signature was capable of identifying a group of patients with poor prognosis in a "high-MYCN" molecular subtype but not in the overall cohort. The predictive ability of this signature was reproduced using qPCR analysis of an independent cohort of neuroblastomas, including a subset of tumors without MYCN amplification. These data reveal an 18-gene Myc activity signature that is highly predictive of poor prognosis in diverse Myc-associated malignancies and suggest its potential clinical application in the identification of Myc-driven tumors that might respond to Myc-targeted therapies. Cancer Res; 77(4); 971-81. ©2016 AACR.

A sketch of known and novel MYCN-associated miRNA networks in neuroblastoma.

Neuroblastoma (NB) originates from neural crest-derived precursors and represents the most common childhood extracranial solid tumour. MicroRNAs (miRNAs), a class of small non-coding RNAs that participate in a wide variety of biological processes by regulating gene expression, appear to play an essential role within the NB context. High-throughput next generation sequencing (NGS) was applied to study the miRNA transcriptome in a cohort of NB tumours with and without MYCN-amplification (MNA and MNnA, respectively) and in dorsal root ganglia (DRG), as a control. Out of the 128 miRNAs differentially expressed in the NB vs. DRG comparison, 47 were expressed at higher levels, while 81 were expressed at lower levels in the NB tumours. We also found that 23 miRNAs were differentially expressed in NB with or without MYCN-amplification, with 17 miRNAs being upregulated and 6 being downregulated in the MNA subtypes. Functional annotation analysis of the target genes of these differentially expressed miRNAs demonstrated that many mRNAs were involved in cancer-related pathways, such as DNA-repair and apoptosis as well as FGFR and EGFR signalling. In particular, we found that miR-628-3p negatively affects MYCN gene expression. Furthermore, we identified a novel miRNA candidate with variable expression in MNA vs. MNnA tumours, whose putative target genes are implicated in the mTOR pathway. The present study provides further insight into the molecular mechanisms that correlate miRNA dysregulation to NB development and progression.

Abstract LB-149: LYAR promotes cell proliferation by repressing CHAC1 expression in neuroblastoma

Abstract Introduction: Neuroblastoma is a cancer of the sympathetic nervous system occurring mostly in infants and young children. Despite considerable progress in the treatment of neuroblastoma, 5-year survival rates have remained less than 50% for the majority of children with high-risk disease. Amplification of the MYCN oncogene and consequent overexpression of the N-Myc oncoprotein is a major prognostic indicator in neuroblastoma, which is strongly associated with aggressive tumour behaviour and poor patient outcome. N-Myc oncoprotein induces neuroblastoma by modulating gene and protein expression and consequently causing cell proliferation. LYAR (Ly-1 antibody reactive clone), a novel nucleolar protein with zinc finger DNA-binding motifs, is mostly involved in cell growth regulation in many cancers. Results: Here we showed that N-Myc up-regulated LYAR expression in neuroblastoma cells. Conversely, LYAR up-regulated N-Myc expression. Affymetrix gene array studies revealed that the gene most significantly repressed by LYAR siRNAs was ChaC glutathione-specific gamma-glutamylcyclotransferase 1 (CHAC1). Consistent with this finding, RT-PCR and immunoblot confirmed that LYAR siRNAs increased CHAC1 gene and protein expression. Alamar blue assays and cell cycle analyses demonstrated that LYAR induced MYCN-amplified neuroblastoma cell proliferation in a CHAC1-depedent manner. Additionally, high levels of LYAR gene expression in human neuroblastoma tissues were associated with MYCN gene expression and predicted poor patient survival independent of patient age and disease stage. Conclusions: Our data demonstrate LYAR as a potential target in neuroblastoma oncogenesis, and provide critical evidence to support the application of LYAR inhibitors for the therapy of neuroblastoma patients. Citation Format: Yuting Sun, Bernard Atmadibrata, Bing Liu, Tao Liu. LYAR promotes cell proliferation by repressing CHAC1 expression in neuroblastoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-149.

The MYCN-HMGA2-CDKN2A pathway in non-small cell lung carcinoma—differences in histological subtypes

BackgroundExtensive research has increased our understanding of the molecular alterations needed for non-small cell lung cancer (NSCLC) development. Deregulation of a pathway including MYCN, HMGA2 and CDKN2A, with the participation of DICER1, is of importance in several solid tumours, and may also be of significance in the pathogenesis of NSCLC.MethodsGene expression of MYCN, HMGA2, CDKN2A and DICER1 were investigated with RT-qPCR in surgically resected NSCLC tumour tissue from 175 patients. Expression of the let-7 microRNA family was performed in 78 adenocarcinomas and 16 matching normal lung tissue samples using microarrays. The protein levels of HMGA2 were determined by immunohistochemistry in 156 tumour samples and the protein expression was correlated with gene expression. Associations between clinical data, including time to recurrence, and expression of mRNA, protein and microRNAs were analysed.ResultsCompared to adenocarcinomas, squamous cell carcinomas had a median 5-fold increase in mRNA expression of HMGA2 (p = 0.003). A positive correlation (r = 0.513, p < 0.010) between HMGA2 mRNA expression and HMGA2 protein expression was seen. At the protein level, 90 % of the squamous cell carcinomas expressed high levels of the HMGA2 protein compared to 47 % of the adenocarcinomas (p < 0.0001). MYCN was positively correlated with HMGA2 (p < 0.010) and DICER1 mRNA expression (p < 0.010), and the expression of the let-7 microRNAs seemed to be correlated with the genes studied. MYCN expression was associated with time to recurrence in multivariate survival analyses (p = 0.020).ConclusionsA significant difference in HMGA2 mRNA expression between the histological subtypes of NSCLC was seen with a higher expression in the squamous cell carcinomas. This was also found at the protein level, and we found a good correlation between the mRNA and the protein expression of HMGA2. Moreover, the expression of MYCN, HMGA2, and DICER1 seems to be correlated to each other and the expression of the let7-genes impacted by their expression. MYCN gene expression seems to be of importance in time to recurrence in this patient cohort with resected NSCLC.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-016-2104-9) contains supplementary material, which is available to authorized users.

Abstract B34: Antitumor activity and sensitivity evaluation of novel BET inhibitors in neuroblastoma

Abstract Children with neuroblastoma exhibit marked variability in outcome based on age at diagnosis, disease stage and tumor biologic characteristics. Genomic amplification of MYCN is a potent oncogenic driver and negative prognostic marker in neuroblastoma patients. Therefore, there is a pressing need to identify therapeutic agents that target MYCN gene expression. The bromodomain and extra-terminal (BET) family of proteins are epigenetic regulators known to control expression of genes involved in cell growth and oncogenesis. Previous reports demonstrate that BET inhibition (BETi) significantly attenuates cellular proliferation in numerous cancer models, perhaps via modulation of the MYC and/or MYCN oncogenes. Here, we show that potent BET inhibition induces anti-tumor effects in preclinical neuroblastoma models. Specifically, GSK726 and GSK762 (GlaxoSmithKline) were used for in vitro cytotoxicity and in vivo therapeutic studies, respectively. Neuroblastoma cell lines (n=22) were treated with GSK726 to calculate IC50 values in a luminescence-based cell viability assay and differential sensitivity was observed with an IC50 range of 27 nM to 9.5 µM. In sensitive cell lines, cell cycle distribution and induction of apoptosis were also measured. In these cell lines, GSK726 treatment resulted in MYCN depletion, G1 arrest within 24 hours, and apoptosis as measured by cleaved-PARP. To assess in vivo efficacy, GSK762 was subcutaneously administered in xenograft models and in genetically engineered neuroblastoma mouse models overexpressing MYCN and MYCN/ALK F1174L in the neural crest. In both models, GSK762 treatment resulted in tumor growth delay. Further assessment of results seen in vitro and in vivo indicated that MYCN amplification status did not fully predict sensitivity to GSK726 or GSK762. Thus, to determine additional biomarkers of sensitivity, we examined baseline gene expression data at the extremes of IC50 values by comparing sensitive (n=6; IC50&amp;lt;128 nM) and resistant (n=4; IC50&amp;gt;940 nM) neuroblastoma cell lines. Gene expression data from the neuroblastoma cell lines generated on HuGene1.0ST expression microarrays (Affymetrix) were utilized, and data were analyzed using the Limma package in R/Bioconductor. Univariate analysis, with a false discovery rate less than 0.25, revealed 6 genes (PTER, PCDHB14, RFTN1, JAK2, MYCBP, and DACH1) that were differentially expressed between sensitive and resistant cell lines in the MYCN amplified setting. While all 6 genes predicted BETi sensitivity in the MYCN-amplified subset of cell lines, only DACH1 expression predicted sensitivity to BET inhibition irrespective of MYCN amplification status (p=7.92x10-7). In addition, high DACH1 expression was correlated with poor patient outcome (p=1.74x10-5). As a result, high DACH1 expression serves as a candidate biomarker for future studies with respect to sensitivity to BETi. Ultimately, these studies will help to optimize the clinical utility of BETi in neuroblastoma and perhaps other MYC-driven malignancies. Citation Format: Jason R. Healy, Robert W. Schnepp, Lori S. Hart, Pichai Raman, Laura Danielson, Michael Russell, Priya Khurana, Maria Gagliardi, Ryan M. Kinsey, Anastasia Wyce, Olena Barbash, Peter J. Tummino, Louis Chesler, John M. Maris. Antitumor activity and sensitivity evaluation of novel BET inhibitors in neuroblastoma. [abstract]. In: Proceedings of the AACR Special Conference on Myc: From Biology to Therapy; Jan 7-10, 2015; La Jolla, CA. Philadelphia (PA): AACR; Mol Cancer Res 2015;13(10 Suppl):Abstract nr B34.