Working with Miraculous Mice: Mus musculus as a Model Organism.

The laboratory mouse has been described as a "miracle" model organism, providing a window by which we may gain an understanding of ourselves. Since the first recorded mouse experiment in 1664, the mouse has become the most used animal model in biomedical research. Mice are ideally suited as a model organism because of their small size, short gestation period, large litter size, and genetic similarity to humans. This article provides a broad overview of the laboratory mouse as a model organism and is intended for undergraduates and those new to working with mice. We delve into the history of the laboratory mouse and outline important terminology to accurately describe research mice. The types of laboratory mice available to researchers are reviewed, including outbred stocks, inbred strains, immunocompromised mice, and genetically engineered mice. The critical role mice have played in advancing knowledge in the areas of oncology, immunology, and pharmacology is highlighted by examining the significant contribution of mice to Nobel Prize winning research. International mouse mutagenesis programs and accurate phenotyping of mouse models are outlined. We also explain important considerations for working with mice, including animal ethics; the welfare principles of replacement, refinement, and reduction; and the choice of mouse model in experimental design. Finally, we present practical advice for maintaining a mouse colony, which involves adequate training of staff, the logistics of mouse housing, monitoring colony health, and breeding strategies. Useful resources for working with mice are also listed. The aim of this overview is to equip the reader with a broad appreciation of the enormous potential and some of the complexities of working with the laboratory mouse in a quest to improve human health. © 2024 The Author(s). Current Protocols published by Wiley Periodicals LLC.

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.

Precision-guided treatment in high-risk pediatric cancers.

Recent research showed that precision medicine can identify new treatment strategies for patients with childhood cancers. However, it is unclear which patients will benefit most from precision-guided treatment (PGT). Here we report consecutive data from 384 patients with high-risk pediatric cancer (with an expected cure rate of less than 30%) who had at least 18 months of follow-up on the ZERO Childhood Cancer Precision Medicine Program PRecISion Medicine for Children with Cancer (PRISM) trial. A total of 256 (67%) patients received PGT recommendations and 110 (29%) received a recommended treatment. PGT resulted in a 36% objective response rate and improved 2-year progression-free survival compared with standard of care (26% versus 12%; P = 0.049) or targeted agents not guided by molecular findings (26% versus 5.2%; P = 0.003). PGT based on tier 1 evidence, PGT targeting fusions or commenced before disease progression had the greatest clinical benefit. Our data show that PGT informed by comprehensive molecular profiling significantly improves outcomes for children with high-risk cancers. ClinicalTrials.gov registration: NCT03336931.

A Phase 1 Study of Intravenous EGFR-ErbituxEDVsMIT in Children with Solid or CNS Tumours Expressing Epidermal Growth Factor Receptor.

BACKGROUND: Recurrent or refractory solid and central nervous system (CNS) tumours in paediatric patients have limited treatment options and carry a poor prognosis. The EnGeneIC Dream Vector (EDV) is a novel nanocell designed to deliver cytotoxic medication directly to the tumour. The epidermal growth factor receptor is expressed in several CNS and solid tumours and is the target for bispecific antibodies attached to the EDV. OBJECTIVE: To assess the safety and tolerability of EGFR-Erbitux receptor EnGeneIC Dream Vector with mitoxantrone (EEDVsMit) in children with recurrent / refractory solid or CNS tumours expressing EGFR. PATIENTS AND METHODS: Patients aged 2-21 years with relapsed or refractory CNS and solid tumours, or radiologically diagnosed diffuse intrinsic pontine glioma (DIPG), were treated in this phase I open-label study of single agent EEDVsMit. Thirty-seven patients' tumours were screened for EGFR expression. EEDVsMit was administered twice weekly in the first cycle and weekly thereafter. Standard dose escalation with a rolling 6 design was employed. Dosing commenced at 5 × 108 EEDVsMit per dose and escalated to 5 × 109 EEDVsMit per dose. RESULTS: EGFR expression was detected in 12 (32%) of the paediatric tumours tested. Nine patients were enrolled and treated on the trial, including three patients with diffuse midline glioma. Overall, EEDVsMit was well tolerated, with no dose-limiting toxicities observed. The most common drug-related adverse events were grade 1-2 fever, nausea and vomiting, rash, lymphopaenia, and mildly deranged liver function tests. All patients had disease progression, including one patient who achieved a mixed response as the best response. CONCLUSIONS: EGFR-Erbitux receptor targeted EnGeneIC Dream Vector with mitoxantrone can be safely delivered in paediatric patients aged 2-21 years with solid or CNS tumours harbouring EGFR expression. The discovery of EGFR expression in a high proportion of paediatric gliomas means that EGFR may be useful as a target for other treatment strategies. Targeted therapeutic-loaded EDVs may be worth exploring further for their role in stimulating an anti-tumour immune response. GOV IDENTIFIER: NCT02687386.

A Primer for Research Scientists on Assessing Mouse Gross and Histopathology Images in the Biomedical Literature.

Advances in genomic technologies have enabled the development of abundant mouse models of human disease, requiring accurate phenotyping to elucidate the consequences of genetic manipulation. Anatomic pathology, an important component of the mouse phenotyping pipeline, is ideally performed by human or veterinary pathologists; however, due to insufficient numbers of pathologists qualified to assess these mouse models morphologically, research scientists may perform "do-it-yourself" pathology, resulting in diagnostic error. In the biomedical literature, pathology data is commonly presented as images of tissue sections, stained with either hematoxylin and eosin or antibodies via immunohistochemistry, accompanied by a figure legend. Data presented in such images and figure legends may contain inaccuracies. Furthermore, there is limited guidance for non-pathologist research scientists concerning the elements required in an ideal pathology image and figure legend in a research publication. In this overview, the components of an ideal pathology image and figure legend are outlined and comprise image quality, image composition, and image interpretation. Background knowledge is important for producing accurate pathology images and critically assessing these images in the literature. This foundational knowledge includes understanding relevant human and mouse anatomy and histology and, for cancer researchers, an understanding of human and mouse tumor classification and morphology, mouse stain background lesions, and tissue processing artifacts. Accurate interpretation of immunohistochemistry is also vitally important and is detailed with emphasis on the requirement for tissue controls and the distribution, intensity, and intracellular location of staining. Common pitfalls in immunohistochemistry interpretation are outlined, and a checklist of questions is provided by which any pathology image may be critically examined. Collaboration with pathologist colleagues is encouraged. This overview aims to equip researchers to critically assess the quality and accuracy of pathology images in the literature to improve the reliability and reproducibility of published pathology data. © 2023 The Authors. Current Protocols published by Wiley Periodicals LLC.

High-Throughput Drug Screening of Primary Tumor Cells Identifies Therapeutic Strategies for Treating Children with High-Risk Cancer.

For one-third of patients with pediatric cancer enrolled in precision medicine programs, molecular profiling does not result in a therapeutic recommendation. To identify potential strategies for treating these high-risk pediatric patients, we performed in vitro screening of 125 patient-derived samples against a library of 126 anticancer drugs. Tumor cell expansion did not influence drug responses, and 82% of the screens on expanded tumor cells were completed while the patients were still under clinical care. High-throughput drug screening (HTS) confirmed known associations between activating genomic alterations in NTRK, BRAF, and ALK and responses to matching targeted drugs. The in vitro results were further validated in patient-derived xenograft models in vivo and were consistent with clinical responses in treated patients. In addition, effective combinations could be predicted by correlating sensitivity profiles between drugs. Furthermore, molecular integration with HTS identified biomarkers of sensitivity to WEE1 and MEK inhibition. Incorporating HTS into precision medicine programs is a powerful tool to accelerate the improved identification of effective biomarker-driven therapeutic strategies for treating high-risk pediatric cancers. SIGNIFICANCE: Integrating HTS with molecular profiling is a powerful tool for expanding precision medicine to support drug treatment recommendations and broaden the therapeutic options available to high-risk pediatric cancers.

Precision Medicine Is Changing the Roles of Healthcare Professionals, Scientists, and Research Staff: Learnings from a Childhood Cancer Precision Medicine Trial.

Precision medicine programs aim to utilize novel technologies to identify personalized treatments for children with cancer. Delivering these programs requires interdisciplinary efforts, yet the many groups involved are understudied. This study explored the experiences of a broad range of professionals delivering Australia's first precision medicine trial for children with poor-prognosis cancer: the PRecISion Medicine for Children with Cancer (PRISM) national clinical trial of the Zero Childhood Cancer Program. We conducted semi-structured interviews with 85 PRISM professionals from eight professional groups, including oncologists, surgeons, clinical research associates, scientists, genetic professionals, pathologists, animal care technicians, and nurses. We analyzed interviews thematically. Professionals shared that precision medicine can add complexity to their role and result in less certain outcomes for families. Although many participants described experiencing a greater emotional impact from their work, most expressed very positive views about the impact of precision medicine on their profession and its future potential. Most reported navigating precision medicine without formal training. Each group described unique challenges involved in adapting to precision medicine in their profession. Addressing training gaps and meeting the specific needs of many professional groups involved in precision medicine will be essential to ensure the successful implementation of standard care.

A novel transcriptional signature identifies T-cell infiltration in high-risk paediatric cancer.

BACKGROUND: Molecular profiling of the tumour immune microenvironment (TIME) has enabled the rational choice of immunotherapies in some adult cancers. In contrast, the TIME of paediatric cancers is relatively unexplored. We speculated that a more refined appreciation of the TIME in childhood cancers, rather than a reliance on commonly used biomarkers such as tumour mutation burden (TMB), neoantigen load and PD-L1 expression, is an essential prerequisite for improved immunotherapies in childhood solid cancers. METHODS: We combined immunohistochemistry (IHC) with RNA sequencing and whole-genome sequencing across a diverse spectrum of high-risk paediatric cancers to develop an alternative, expression-based signature associated with CD8+ T-cell infiltration of the TIME. Furthermore, we explored transcriptional features of immune archetypes and T-cell receptor sequencing diversity, assessed the relationship between CD8+ and CD4+ abundance by IHC and deconvolution predictions and assessed the common adult biomarkers such as neoantigen load and TMB. RESULTS: A novel 15-gene immune signature, Immune Paediatric Signature Score (IPASS), was identified. Using this signature, we estimate up to 31% of high-risk cancers harbour infiltrating T-cells. In addition, we showed that PD-L1 protein expression is poorly correlated with PD-L1 RNA expression and TMB and neoantigen load are not predictive of T-cell infiltration in paediatrics. Furthermore, deconvolution algorithms are only weakly correlated with IHC measurements of T-cells. CONCLUSIONS: Our data provides new insights into the variable immune-suppressive mechanisms dampening responses in paediatric solid cancers. Effective immune-based interventions in high-risk paediatric cancer will require individualised analysis of the TIME.

Histone H3-wild type diffuse midline gliomas with H3K27me3 loss are a distinct entity with exclusive EGFR or ACVR1 mutation and differential methylation of homeobox genes.

Diffuse midline gliomas (DMG) harbouring H3K27M mutation are paediatric tumours with a dismal outcome. Recently, a new subtype of midline gliomas has been described with similar features to DMG, including loss of H3K27 trimethylation, but lacking the canonical H3K27M mutation (H3-WT). Here, we report a cohort of five H3-WT tumours profiled by whole-genome sequencing, RNA sequencing and DNA methylation profiling and combine their analysis with previously published cases. We show that these tumours have recurrent and mutually exclusive mutations in either ACVR1 or EGFR and are characterised by high expression of EZHIP associated to its promoter hypomethylation. Affected patients share a similar poor prognosis as patients with H3K27M DMG. Global molecular analysis of H3-WT and H3K27M DMG reveal distinct transcriptome and methylome profiles including differential methylation of homeobox genes involved in development and cellular differentiation. Patients have distinct clinical features, with a trend demonstrating ACVR1 mutations occurring in H3-WT tumours at an older age. This in-depth exploration of H3-WT tumours further characterises this novel DMG, H3K27-altered sub-group, characterised by a specific immunohistochemistry profile with H3K27me3 loss, wild-type H3K27M and positive EZHIP. It also gives new insights into the possible mechanism and pathway regulation in these tumours, potentially opening new therapeutic avenues for these tumours which have no known effective treatment. This study has been retrospectively registered on clinicaltrial.gov on 8 November 2017 under the registration number NCT03336931 ( https://clinicaltrials.gov/ct2/show/NCT03336931 ).

A Primer for Assessing the Pathology in Mouse Models of Neuroblastoma.

Neuroblastoma, the most common extracranial solid tumor in young children, arises from the sympathetic nervous system. Our understanding of neuroblastoma has been improved by the development of both genetically engineered and xenograft mouse models of the disease. Anatomical pathology is an essential component of the phenotyping of mouse models of cancer, characterizing the morphologic effects of genetic manipulation and drug treatment. The Th-MYCN model, the most widely used of several genetically engineered mouse models of neuroblastoma, was established by targeted expression of the human MYCN gene to murine neural crest cells under the control of the rat tyrosine hydroxylase promoter. Neuroblastoma development in Th-MYCN mice is preceded by neuroblast hyperplasia-the persistence and proliferation of neural crest-derived neuroblasts within the sympathetic autonomic ganglia. The neuroblastomas that subsequently develop morphologically resemble human neuroblastoma and carry chromosomal gains and losses in regions syntenic with those observed in human tumors. In this overview, we describe the essential pathologic features for investigators when assessing mouse models of neuroblastoma. We outline human neuroblastoma as the foundation for understanding the murine disease, followed by details of the murine sympathetic ganglia from which neuroblastoma arises. Sympathetic ganglia, both with and without neuroblast hyperplasia, are described. The macroscopic and microscopic features of murine neuroblastoma are explained, including assessment of xenografts and tumors following drug treatment. An approach to experimental design is also detailed. Increased understanding of the pathology of murine neuroblastoma should improve reproducibility and comparability of research findings and assist investigators working with mouse models of neuroblastoma. © 2021 Wiley Periodicals LLC.

Parents' experiences of postmortem tumor donation for high-grade gliomas: benefits and suggested improvements.

BACKGROUND: Pediatric high-grade glioma is a devastating diagnosis. There has been no improvement in outcomes for several decades, with few children surviving 2 years postdiagnosis. Research progress has been hampered by a lack of tumor samples, which can be used to develop and test novel therapies. Postmortem tumor donations are therefore a valuable opportunity to collect tissue. In this study, we explored Australian parents' experiences of donating their child's tumor for research after their child had died. METHODS: We collected qualitative data from 11 bereaved parents who consented to donate samples of their child's high-grade glioma for research postmortem. We asked parents about their perceived benefits/burdens of the autopsy, recommendations for improving consent discussions, and decision regret. RESULTS: Parents hoped that their donation would help to find a cure for future children with high-grade glioma. They described feeling comforted knowing that their child's suffering may help others. Some parents also felt that the donation would help them better understand their child's tumor. Although some parents described discomfort about procedures leading up to the autopsy, parents reported minimal regret regarding their decision to donate their child's tumor. Parents provided recommendations to improve consent discussions, such as providing more information about the autopsy logistics and why the donation was needed. CONCLUSION: Parents consented to autopsy for altruistic reasons, although donation may also assist parents in their grieving. There is a strong need to improve access to tumor donations for any family who wishes to donate.

Dual Targeting of Chromatin Stability By The Curaxin CBL0137 and Histone Deacetylase Inhibitor Panobinostat Shows Significant Preclinical Efficacy in Neuroblastoma.

PURPOSE: We investigated whether targeting chromatin stability through a combination of the curaxin CBL0137 with the histone deacetylase (HDAC) inhibitor, panobinostat, constitutes an effective multimodal treatment for high-risk neuroblastoma. EXPERIMENTAL DESIGN: The effects of the drug combination on cancer growth were examined in vitro and in animal models of MYCN-amplified neuroblastoma. The molecular mechanisms of action were analyzed by multiple techniques including whole transcriptome profiling, immune deconvolution analysis, immunofluorescence, flow cytometry, pulsed-field gel electrophoresis, assays to assess cell growth and apoptosis, and a range of cell-based reporter systems to examine histone eviction, heterochromatin transcription, and chromatin compaction. RESULTS: The combination of CBL0137 and panobinostat enhanced nucleosome destabilization, induced an IFN response, inhibited DNA damage repair, and synergistically suppressed cancer cell growth. Similar synergistic effects were observed when combining CBL0137 with other HDAC inhibitors. The CBL0137/panobinostat combination significantly delayed cancer progression in xenograft models of poor outcome high-risk neuroblastoma. Complete tumor regression was achieved in the transgenic Th-MYCN neuroblastoma model which was accompanied by induction of a type I IFN and immune response. Tumor transplantation experiments further confirmed that the presence of a competent adaptive immune system component allowed the exploitation of the full potential of the drug combination. CONCLUSIONS: The combination of CBL0137 and panobinostat is effective and well-tolerated in preclinical models of aggressive high-risk neuroblastoma, warranting further preclinical and clinical investigation in other pediatric cancers. On the basis of its potential to boost IFN and immune responses in cancer models, the drug combination holds promising potential for addition to immunotherapies.

The important role of routine cytopathology in pediatric precision oncology.

BACKGROUND: The development of high-throughput drug screening (HTS) using primary cultures provides a promising, clinically translatable approach to tailoring treatment strategies for patients with cancer. However, this has been challenging for solid tumors because of often limited amounts of tissue available. In most cases, in vitro expansion is required before HTS, which may lead to overgrowth and contamination by non-neoplastic cells. METHODS: In this study, hematoxylin and eosin staining and immunohistochemical staining were performed on 129 cytopathology cases from 95 patients. These cytopathology cases comprised cell block preparations derived from primary tumor specimens or patient-derived xenografts as part of a pediatric precision oncology trial. Cytopathology cases were compared with the morphology and immunohistochemical staining profile of the original tumor. Cases were reported as tumor cells present, equivocal, or tumor cells absent. The HTS results from cytopathologically validated cultures were incorporated into a multidisciplinary tumor board report issued to the treating clinician to guide clinical decision making. RESULTS: On cytopathologic examination, tumor cells were present in 77 of 129 cases (60%) and were absent in 38 of 129 cases (29%), whereas 14 of 129 cases (11%) were equivocal. Cultures that contained tumor cells resembled the tumors from which they were derived. CONCLUSIONS: Cytopathologic examination of tumor cell block preparations is feasible and provides detailed morphologic characterization. Cytopathologic examination is essential for ensuring that samples submitted for HTS contain representative tumor cells and that in vitro drug sensitivity data are clinically translatable.

Exploiting the reactive oxygen species imbalance in high-risk paediatric acute lymphoblastic leukaemia through auranofin.

BACKGROUND: The prognosis for high-risk childhood acute leukaemias remains dismal and established treatment protocols often cause long-term side effects in survivors. This study aims to identify more effective and safer therapeutics for these patients. METHODS: A high-throughput phenotypic screen of a library of 3707 approved drugs and pharmacologically active compounds was performed to identify compounds with selective cytotoxicity against leukaemia cells followed by further preclinical evaluation in patient-derived xenograft models. RESULTS: Auranofin, an FDA-approved agent for the treatment of rheumatoid arthritis, was identified as exerting selective anti-cancer activity against leukaemia cells, including patient-derived xenograft cells from children with high-risk ALL, versus solid tumour and non-cancerous cells. It induced apoptosis in leukaemia cells by increasing reactive oxygen species (ROS) and potentiated the activity of the chemotherapeutic cytarabine against highly aggressive models of infant MLL-rearranged ALL by enhancing DNA damage accumulation. The enhanced sensitivity of leukaemia cells towards auranofin was associated with lower basal levels of the antioxidant glutathione and higher baseline ROS levels compared to solid tumour cells. CONCLUSIONS: Our study highlights auranofin as a well-tolerated drug candidate for high-risk paediatric leukaemias that warrants further preclinical investigation for application in high-risk paediatric and adult acute leukaemias.

Recurrent SPECC1L-NTRK fusions in pediatric sarcoma and brain tumors.

The identification of rearrangements driving expression of neurotrophic receptor tyrosine kinase (NTRK) family kinases in tumors has become critically important because of the availability of effective, specific inhibitor drugs. Whole-genome sequencing (WGS) combined with RNA sequencing (RNA-seq) can identify novel and recurrent expressed fusions. Here we describe three SPECC1L-NTRK fusions identified in two pediatric central nervous system cancers and an extracranial solid tumor using WGS and RNA-seq. These fusions arose either through a simple balanced rearrangement or in the context of a complex chromoplexy event. We cloned the SPECC1L-NTRK2 fusion directly from a patient sample and showed that enforced expression of this fusion is sufficient to promote cytokine-independent survival and proliferation. Cells transformed by SPECC1L-NTRK2 expression are sensitive to a TRK inhibitor drug. We report here that SPECC1L-NTRK fusions can arise in a range of pediatric cancers. Although WGS and RNA-seq are not required to detect NTRK fusions, these techniques may be of benefit when NTRK fusions are not suspected on clinical grounds or not identified by other methods.

Whole genome, transcriptome and methylome profiling enhances actionable target discovery in high-risk pediatric cancer.

The Zero Childhood Cancer Program is a precision medicine program to benefit children with poor-outcome, rare, relapsed or refractory cancer. Using tumor and germline whole genome sequencing (WGS) and RNA sequencing (RNAseq) across 252 tumors from high-risk pediatric patients with cancer, we identified 968 reportable molecular aberrations (39.9% in WGS and RNAseq, 35.1% in WGS only and 25.0% in RNAseq only). Of these patients, 93.7% had at least one germline or somatic aberration, 71.4% had therapeutic targets and 5.2% had a change in diagnosis. WGS identified pathogenic cancer-predisposing variants in 16.2% of patients. In 76 central nervous system tumors, methylome analysis confirmed diagnosis in 71.1% of patients and contributed to a change of diagnosis in two patients (2.6%). To date, 43 patients have received a recommended therapy, 38 of whom could be evaluated, with 31% showing objective evidence of clinical benefit. Comprehensive molecular profiling resolved the molecular basis of virtually all high-risk cancers, leading to clinical benefit in some patients.

CD30 and ALK combination therapy has high therapeutic potency in RANBP2-ALK-rearranged epithelioid inflammatory myofibroblastic sarcoma.

BACKGROUND: Epithelioid inflammatory myofibroblastic sarcoma (eIMS) is characterised by perinuclear ALK localisation, CD30 expression and early relapse despite crizotinib treatment. We aimed to identify therapies to prevent and/or treat ALK inhibitor resistance. METHODS: Malignant ascites, from an eIMS patient at diagnosis and following multiple relapses, were used to generate matched diagnosis and relapse xenografts. RESULTS: Xenografts were validated by confirmation of RANBP2-ALK rearrangement, perinuclear ALK localisation and CD30 expression. Although brentuximab-vedotin (BV) demonstrated single-agent activity, tumours regrew during BV therapy. BV resistance was associated with reduced CD30 expression and induction of ABCB1. BV resistance was reversed in vitro by tariquidar, but combination BV and tariquidar treatment only briefly slowed xenograft growth compared with BV alone. Combining BV with either crizotinib or ceritinib resulted in marked tumour shrinkage in both xenograft models, and resulted in prolonged tumour-free survival in the diagnosis compared with the relapse xenograft. CONCLUSIONS: CD30 is a therapeutic target in eIMS. BV efficacy is limited by the rapid emergence of resistance. Prolonged survival with combination ALK and CD30-targeted-therapy in the diagnosis model provides the rationale to trial this combination in eIMS patients at diagnosis. This combination could also be considered for other CD30-positive, ALK-rearranged malignancies.

Suppression of ABCE1-Mediated mRNA Translation Limits N-MYC-Driven Cancer Progression.

The ability of the N-MYC transcription factor to drive cancer progression is well demonstrated in neuroblastoma, the most common extracranial pediatric solid tumor, where MYCN amplification heralds a poor prognosis, with only 11% of high-risk patients surviving past 5 years. However, decades of attempts of direct inhibition of N-MYC or its paralogues has led to the conclusion that this protein is "undruggable." Therefore, targeting pathways upregulated by N-MYC signaling presents an alternative therapeutic approach. Here, we show that MYCN-amplified neuroblastomas are characterized by elevated rates of protein synthesis and that high expression of ABCE1, a translation factor directly upregulated by N-MYC, is itself a strong predictor of poor clinical outcome. Despite the potent ability of N-MYC in heightening protein synthesis and malignant characteristics in cancer cells, suppression of ABCE1 alone selectively negated this effect, returning the rate of translation to baseline levels and significantly reducing the growth, motility, and invasiveness of MYCN-amplified neuroblastoma cells and patient-derived xenograft tumors in vivo. The growth of nonmalignant cells or MYCN-nonamplified neuroblastoma cells remained unaffected by reduced ABCE1, supporting a therapeutic window associated with targeting ABCE1. Neuroblastoma cells with c-MYC overexpression also required ABCE1 to maintain cell proliferation and translation. Taken together, ABCE1-mediated translation constitutes a critical process in the progression of N-MYC-driven and c-MYC-driven cancers that warrants investigations into methods of its therapeutic inhibition. SIGNIFICANCE: These findings demonstrate that N-MYC-driven cancers are reliant on elevated rates of protein synthesis driven by heightened expression of ABCE1, a vulnerability that can be exploited through suppression of ABCE1.

ABCC4/MRP4 contributes to the aggressiveness of Myc-associated epithelial ovarian cancer.

Epithelial ovarian cancer (EOC) is a complex disease comprising discrete histological and molecular subtypes, for which survival rates remain unacceptably low. Tailored approaches for this deadly heterogeneous disease are urgently needed. Efflux pumps belonging to the ATP-binding cassette (ABC) family of transporters are known for roles in both drug resistance and cancer biology and are also highly targetable. Here we have investigated the association of ABCC4/MRP4 expression to clinical outcome and its biological function in endometrioid and serous tumors, common histological subtypes of EOC. We found high expression of ABCC4/MRP4, previously shown to be directly regulated by c-Myc/N-Myc, was associated with poor prognosis in endometrioid EOC (P = .001) as well as in a subset of serous EOC with a "high-MYCN" profile (C5/proliferative; P = .019). Transient siRNA-mediated suppression of MRP4 in EOC cells led to reduced growth, migration and invasion, with the effects being most pronounced in endometrioid and C5-like serous cells compared to non-C5 serous EOC cells. Sustained knockdown of MRP4 also sensitized endometrioid cells to MRP4 substrate drugs. Furthermore, suppression of MRP4 decreased the growth of patient-derived EOC cells in vivo. Together, our findings provide the first evidence that MRP4 plays an important role in the biology of Myc-associated ovarian tumors and highlight this transporter as a potential therapeutic target for EOC.