Citations

Abstract The amplified MYCN gene serves as an oncogenic driver in approximately 20% of high-risk pediatric neuroblastomas. Here, we show that the family member MYC is a potent transforming gene in a separate subset of high-risk neuroblastoma cases (∼10%), based on (i) its upregulation by focal enhancer amplification or genomic rearrangements leading to enhancer hijacking, and (ii) its ability to transform neuroblastoma precursor cells in a transgenic animal model. The aberrant regulatory elements associated with oncogenic MYC activation include focally amplified distal enhancers and translocation of highly active enhancers from other genes to within topologically associating domains containing the MYC gene locus. The clinical outcome for patients with high levels of MYC expression is virtually identical to that of patients with amplification of the MYCN gene, a known high-risk feature of this disease. Together, these findings establish MYC as a bona fide oncogene in a clinically significant group of high-risk childhood neuroblastomas. Significance: Amplification of the MYCN oncogene is a recognized hallmark of high-risk pediatric neuroblastoma. Here, we demonstrate that MYC is also activated as a potent oncogene in a distinct subset of neuroblastoma cases through either focal amplification of distal enhancers or enhancer hijacking mediated by chromosomal translocation. Cancer Discov; 8(3); 320–35. ©2017 AACR. This article is highlighted in the In This Issue feature, p. 253

Abstract Elevated expression levels of MYC family genes are frequently observed in human cancer cells and correlate with tumor aggressiveness and poor prognosis. In neuroblastoma 40% of all cases are high-risk, of which 20% harbor amplification of the MYCN proto-oncogene. In high-risk cases lacking MYCN gene amplification, high expression levels of c-MYC (MYC) are often present and are associated with unfavorable histology and a poor survival. Unlike MYCN amplification, which is frequently observed in the presence of segmental chromosomal aberrations, MYC overexpression is not associated with genetic abnormalities or somatic mutations. In order to study this newly defined subgroup, we have created a novel transgenic zebrafish model in which overexpression of MYC alone in the peripheral sympathetic nervous system (PSNS) drives early-onset neuroblastoma in nearly every fish by seven weeks of age. The tumors resulting from MYC overexpression arise in the interrenal gland, which is the fish counterpart of the adrenal medulla, and are histologically identical to human neuroblastoma. We next performed the Assay for Transposase Accessible Chromatin (ATAC) sequencing and RNA-seq to identify open chromatin regions that correlate with activation of gene transcription. Lineage specific genes essential for neuronal precursor cell identity, such as PHOX2B, HAND2, and TFAP2A are highly expressed in both MYC-expressing and MYCN-amplified human neuroblastoma cell lines and are actively transcribed in zebrafish models of MYC and MYCN driven neuroblastoma. Furthermore, these studies reveal shared and differential regulatory of effects of MYC relative to MYCN activity in maintaining the malignant phenotype of neuroblastoma in vivo. Additional insight into the mechanisms of aberrant transcriptional regulation will inform the future design and use of therapeutic strategies targeting transcription in this high-risk malignancy of childhood. Citation Format: Mark W. Zimmerman, Shuning He, Shizhen Zhu, Song Yang, Yi Zhou, Leonard I. Zon, A Thomas Look. Modeling the chromatin and transcriptional landscape of MYC and MYCN driven neuroblastoma in zebrafish [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 3871. doi:10.1158/1538-7445.AM2017-3871

Pulmonary vein stenosis (PVS) is a luminal narrowing of extrapulmonary pulmonary veins. In pediatric patients, it arises following repair of congenital heart disease, particularly anomalous pulmonary venous return; in lung disease, especially prematurity; and rarely in isolation. The etiology is unknown and the course often fatal without lung transplantation. We hypothesized that systematic clinicopathologic review of pediatric PVS could provide further pathogenic insight. We included patients who underwent first resection of pulmonary venous tissue for symptomatic PVS at our pediatric referral center from 1995 to 2014. Clinical records and hematoxylin and eosin slides were reviewed. Subsets were immunostained for smooth muscle actin, Ki-67, β-catenin, estrogen receptor, and other markers and analyzed forUSP6gene rearrangement. A total of 97 patients (57% male; median age: 6 mo) were identified. Overall, 59 (61%) had prior congenital heart disease repair, 35 involving pulmonary vein manipulation. Samples included 213 separate anatomic sites (median: 2/patient). Histologically, all showed sparsely cellular intimal expansion composed of haphazardly arranged fibroblasts with slender nuclei in myxoid matrix. This tissue merged with underlying collagen. Most samples had a variably continuous sheath of cardiomyocytes. Ancillary tests supported a reactive fibroblastic proliferation; in particular, fibroblasts showed cytoplasmic β-catenin localization, no estrogen receptor expression, and noUSP6rearrangement. At last follow-up (mean: 2.3 y), 46% of patients had died of disease. Pediatric PVS uniformly consists of a paucicellular fibrointimal proliferation, irrespective of clinical scenario. It may be best conceived of as a form of reactive hyperplasia. As with other forms of vascular remodeling, trauma (iatrogenic or occult) is likely an inciting factor. A comprehensive understanding of the surgical pathology of PVS may further inform therapeutic strategies in this lethal disease.

Objectives: Delirium severity is independently associated with longer hospital stays, nursing home placement, and death in patients outside the ICU. Delirium severity in the ICU is not routinely measured because the available instruments are difficult to complete in critically ill patients. We designed our study to assess the reliability and validity of a new ICU delirium severity tool, the Confusion Assessment Method for the ICU-7 delirium severity scale. Design: Observational cohort study. Setting: Medical, surgical, and progressive ICUs of three academic hospitals. Patients: Five hundred eighteen adult (≥ 18 yr) patients. Interventions: None. Measurements and Main Results: Patients received the Confusion Assessment Method for the ICU, Richmond Agitation-Sedation Scale, and Delirium Rating Scale-Revised-98 assessments. A 7-point scale (0–7) was derived from responses to the Confusion Assessment Method for the ICU and Richmond Agitation-Sedation Scale items. Confusion Assessment Method for the ICU-7 showed high internal consistency (Cronbach’s α = 0.85) and good correlation with Delirium Rating Scale-Revised-98 scores (correlation coefficient = 0.64). Known-groups validity was supported by the separation of mechanically ventilated and nonventilated assessments. Median Confusion Assessment Method for the ICU-7 scores demonstrated good predictive validity with higher odds (odds ratio = 1.47; 95% CI = 1.30–1.66) of in-hospital mortality and lower odds (odds ratio = 0.8; 95% CI = 0.72–0.9) of being discharged home after adjusting for age, race, gender, severity of illness, and chronic comorbidities. Higher Confusion Assessment Method for the ICU-7 scores were also associated with increased length of ICU stay (p = 0.001). Conclusions: Our results suggest that Confusion Assessment Method for the ICU-7 is a valid and reliable delirium severity measure among ICU patients. Further research comparing it to other delirium severity measures, its use in delirium efficacy trials, and real-life implementation is needed to determine its role in research and clinical practice.

Abstract Earlier reports indicated that the role of Nf1 tumor suppressor gene in limiting sympathoadrenal cell growth during embryologic development is independent of its ability to down-modulate RAS-MAPK signaling. This finding raised the question of whether neuroblastoma pathogenesis was also accelerated by loss of a similar non-canonical function of NF1. To elucidate how loss of the NF1 tumor suppressor gene contributes to the development of high-risk neuroblastoma, we relied on a transgenic zebrafish model that overexpresses MYCN and harbors loss-of-function nf1 mutations. We show here that loss of nf1 leads to aberrant activation of RAS signaling in MYCN-induced neuroblastoma, promoting both increased tumor cell survival and rapid tumor cell proliferation. We demonstrate further that the GTPase-activating protein (GAP) activity of the (GAP)-related domain (GRD) is sufficient to suppress accelerated initiation of neuroblastoma in nf1-deficient zebrafish, even though this transgene is unable to restrict abnormal sympathoadrenal cell growth during embryologic development. Hence NF1 exhibits different activities in vivo in the normal development and tumorigenesis of the peripheral sympathetic nervous system. Our findings establish nf1-deficient zebrafish that overexpress MYCN as an ideal animal model system for investigating new strategies to improve treatment of very high risk neuroblastomas with aberrant RAS-MAPK activation. We are currently performing high-throughput in vivo drug analysis using these zebrafish with primary tumors. Citation Format: Shuning He, Marc R. Mansour, Mark W. Zimmerman, Dong Hyuk Ki, Hillary M. Layden, Koshi Akahane, Eric D. de Groh, Antonio R. Perez-Atayde, Shizhen Zhu, Jonathan A. Epstein, A Thomas Look. Synergy between loss of NF1 and overexpression of MYCN in neuroblastoma is mediated by the GAP-related domain. [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 2456.

Earlier reports showed that hyperplasia of sympathoadrenal cell precursors during embryogenesis in Nf1-deficient mice is independent of Nf1’s role in down-modulating RAS-MAPK signaling. We demonstrate in zebrafish that nf1 loss leads to aberrant activation of RAS signaling in MYCN-induced neuroblastomas that arise in these precursors, and that the GTPase-activating protein (GAP)-related domain (GRD) is sufficient to suppress the acceleration of neuroblastoma in nf1-deficient fish, but not the hypertrophy of sympathoadrenal cells in nf1 mutant embryos. Thus, even though neuroblastoma is a classical “developmental tumor”, NF1 relies on a very different mechanism to suppress malignant transformation than it does to modulate normal neural crest cell growth. We also show marked synergy in tumor cell killing between MEK inhibitors (trametinib) and retinoids (isotretinoin) in primary nf1a-/- zebrafish neuroblastomas. Thus, our model system has considerable translational potential for investigating new strategies to improve the treatment of very high-risk neuroblastomas with aberrant RAS-MAPK activation.