Abstract Some evidence suggests that pediatric sarcomas have both shared and distinct genetic profiles; however, large-scale efforts to characterize germline genetic susceptibility across these malignancies are limited by their rarity. We evaluated the role of common and rare variants in the genetic etiology of the more frequent pediatric sarcomas: osteosarcoma (OS); Ewing sarcoma (ES); and rhabdomyosarcoma (RMS), subcategorized into embryonal (ERMS) and alveolar (ARMS). METHODS: We evaluated 4,161 European-ancestry cases with genotype data (1,843 OS, 733 ES, 1,585 RMS, and ~61,000 cancer-free adult controls) and 2,474 cases with exome or genome sequencing (1,002 OS, 579 ES, 893 RMS, and 1,057 controls; jointly called with the same QC). Analyses included: 1) estimating disease heritability for both common SNPs (MAF>3%; genome-wide) and rare loss-of-function variants (MAF<1%; exome-wide); and 2) determining the frequency of rare predicted pathogenic (P) or likely pathogenic (LP; ACMG-AMP) variants in cancer susceptibility genes (CSG). RESULTS: For OS, we conducted a new GWAS and determined that common variants explained 2.7% (SE 1.1%) of disease heritability, while rare LOF variants explained 12.7% (SE 1.5%; compared to 0.4% for synonymous variants). A similar pattern was observed for ERMS, where rare LOF variants explained a greater proportion of disease heritability (RMS 8.6%, SE 1.2%; ERMS 12.6%, SE 1.7%; ARMS n/a due to small sample size) compared to common variants from our new GWAS (0.9%, SE 1.6%). Conversely, common variants explained a greater proportion of ES heritability (5.4%, SE 0.5%) and of ARMS heritability (15.5%, SE 6.4%). For 113 established CSGs, and for the 60 moderate-to-high penetrant autosomal dominant (AD) genes, OS and ERMS had significantly (Pexact<0.01) more rare P/LP variants overall compared to controls; whereas ARMS and ES had significantly fewer P/LP variants than ERMS and OS, similar to the controls. We confirmed previously reported AD genes, and identified new genes, with an enrichment of P/LP variants in ERMS and OS compared to controls. For both ARMS and ES, the only AD gene significantly enriched for P/LP variants was CHEK2. For all cases, patients with a P/LP variant were significantly younger and had significantly more poor outcomes (ie, metastasis, stage 4 disease, and/or death) than those without. For 49 autosomal recessive CSGs, heterozygous P/LP carrier frequencies were similar among all sarcomas (8-11%), and several specific genes had similar P/LP variant enrichment across sarcomas, and for ES and ARMS only, compared to controls. CONCLUSION: In the largest set of pediatric sarcoma cases assembled to date, genetic susceptibility was largely driven by rare P/LP AD gene variants in tumor types not characterized by canonical somatic fusions (OS and ERMS). In contrast, fusion-driven tumor types (ES and ARMS) were driven more by common variants. Citation Format: Lisa Mirabello, Laura E. Egolf, Bin Zhu, D. Matthew Gianferante, Kevin Wang, Shengchao Alfred Li, Mitchell J. Machiela, Logan G. Spector, Joshua D. Schiffman, Aniko Sabo, Alexander Renwick, Bailey Martin-Giacalone, Michael E. Scheurer, Sharon Plon, Douglas Hawkins, Rajkumar Venkatramani, Douglas Stewart, Lindsay M. Morton, Melissa M. Hudson, Gregory T. Armstrong, Smita Bhatia, Michael Dean, Katherine A. Janeway, Ana Patiño-Garcia, Fernando Lecanda, Massimo Serra, Claudia Hattinger, Katia Scotlandi, Adrienne M. Flanagan, Fernanda Amary, Irene L. Andrulis, Jay S. Wunder, Mandy L. Ballinger, David M. Thomas, Olivier Delattre, Aubrey K. Hubbard, Jia Liu, Wen Luo, Belynda D. Hicks, Meredith Yeager, Maryam Rafati, Wen-Yi Huang, Maria T. Landi, Adriana Lori, Ryan Diver, Sharon A. Savage, Stephen J. Chanock, Philip J. Lupo. Underlying germline genetic architecture of pediatric sarcomas: Evaluating the role of common and rare variants in 4,160 patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 775.

BACKGROUND:High-risk neuroblastoma is a complex genetic disease that is lethal in more than 50% of patients despite intense multimodal therapy. Through genome-wide association studies (GWAS) and next-generation sequencing, we have identified common single nucleotide polymorphisms and rare, pathogenic or likely pathogenic germline loss-of-function variants in BARD1 enriched in neuroblastoma patients. The functional implications of these findings remain poorly understood.METHODS:We correlated BARD1 genotype with expression in normal tissues and neuroblastomas, along with the burden of DNA damage in tumors. To validate the functional consequences of germline pathogenic or likely pathogenic BARD1 variants, we used CRISPR-Cas9 to generate isogenic neuroblastoma (IMR-5) and control (RPE1) cellular models harboring heterozygous BARD1 loss-of-function variants (R112*, R150*, E287fs, and Q564*) and quantified genomic instability in these cells via next-generation sequencing and with functional assays measuring the efficiency of DNA repair.RESULTS:Both common and rare neuroblastoma-associated BARD1 germline variants were associated with lower levels of BARD1 mRNA and an increased burden of DNA damage. Using isogenic heterozygous BARD1 loss-of-function variant cellular models, we functionally validated this association with inefficient DNA repair. BARD1 loss-of-function variant isogenic cells exhibited reduced efficiency in repairing Cas9-induced DNA damage, ineffective RAD51 focus formation at DNA double-strand break sites, and enhanced sensitivity to cisplatin and poly (ADP-ribose) polymerase (PARP) inhibition both in vitro and in vivo.CONCLUSIONS:Taken together, we demonstrate that germline BARD1 variants disrupt DNA repair fidelity. This is a fundamental molecular mechanism contributing to neuroblastoma initiation that may have important therapeutic implications.

BACKGROUND Neuroblastoma is an embryonal cancer of the developing sympathetic nervous system. The genetic contribution of rare pathogenic or likely pathogenic (P-LP) germline variants in patients without a family history remains unclear. METHODS Germline DNA sequencing was performed on 786 neuroblastoma patients. The frequency of rare cancer predisposition gene (CPG) P-LP variants in cases was compared to two cancer-free control cohorts. Matched tumor DNA sequencing was evaluated for "second hits" and germline DNA array data from 5,585 neuroblastoma cases and 23,505 cancer-free control children was analyzed to identify rare germline copy number variants (CNVs). Patients with germline P-LP variants were compared to those without to test for association with clinical characteristics, tumor features, and survival. RESULTS We observed 116 P-LP variants involving 13.9% (109/786) of patients, representing a significant excess burden compared to controls (odds ratio: 1.60, 95% confidence interval: 1.27-2.00). BARD1 harbored the most significant enrichment of P-LP variants (odds ratio: 32.30, 95% confidence interval: 6.44-310.35). Rare germline CNVs disrupting BARD1 were identified in patients but absent in controls (odds ratio: 29.47, 95% confidence interval: 1.52-570.70). Patients harboring a germline P-LP variant had a worse overall survival compared to those without (P = 8.6x10-3). CONCLUSIONS BARD1 is an important neuroblastoma predisposition gene harboring both common and rare germline P-LP variation. The presence of any germline P-LP variant in a CPG was independently predictive of worse overall survival. As centers move toward paired tumor-normal sequencing at diagnosis, efforts should be made to centralize data and provide an infrastructure to support cooperative longitudinal prospective studies of germline pathogenic variation.

Importance:Neuroblastoma accounts for 12% of childhood cancer deaths. The genetic contribution of rare pathogenic germline variation in patients without a family history remains unclear. Objective:To define the prevalence, spectrum, and clinical significance of pathogenic germline variation in cancer predisposition genes (CPGs) in neuroblastoma patients. Design Setting and Participants:Germline DNA sequencing was performed on the peripheral blood from 786 neuroblastoma patients unselected for family history. Rare variants mapping to CPGs were evaluated for pathogenicity and the percentage of cases harboring pathogenic (P) or likely pathogenic (LP) variants was quantified. The frequency of CPG P-LP variants in neuroblastoma cases was compared to two distinct cancer-free control cohorts to assess enrichment. Matched tumor DNA sequencing was evaluated for "second hits" at CPGs and germline DNA array data from 5,585 neuroblastoma cases and 23,505 cancer-free control children was analyzed to identify rare germline copy number variants (CNVs) affecting genes with an excess burden of P-LP variants in neuroblastoma. Neuroblastoma patients with germline P-LP variants were compared to those without P-LP variants to test for association with clinical characteristics, tumor features, and patient survival. Main Outcomes and Measures:Rare variant prevalence, pathogenicity, enrichment, and association with clinical characteristics, tumor features, and patient survival. Results:We observed 116 P-LP variants in CPGs involving 13.9% (109/786) of patients, representing a significant excess burden of P-LP variants compared to controls (9.1%; P = 5.14 × 10-5, Odds Ratio: 1.60, 95% confidence interval: 1.27-2.00). BARD1 harbored the most significant burden of P-LP variants compared to controls (1.0% vs. 0.03%; P = 8.18 × 10-7; Odds Ratio: 32.30, 95% confidence interval: 6.44-310.35). Rare germline CNVs disrupting BARD1 were also identified in neuroblastoma patients (0.05%) but absent in controls (P = 7.08 × 10-3; Odds Ratio: 29.47, 95% confidence interval: 1.52 - 570.70). Overall, P-LP variants in DNA repair genes in this study were enriched in cases compared to controls (8.1% vs. 5.7%; P = 0.01; Odds Ratio: 1.45, 95% confidence interval: 1.08-1.92). Neuroblastoma patients harboring a germline P-LP variant had a worse overall survival when compared to patients without P-LP variants (P = 8.6 × 10-3), and this remained significant in a multivariate Cox proportional-hazards model (P = 0.01). Conclusions and Relevance:Neuroblastoma patients harboring germline P-LP variants in CPGs have worse overall survival and BARD1 is an important predisposition gene affected by both common and rare pathogenic variation. Germline sequencing should be performed for all neuroblastoma patients at diagnosis to inform genetic counseling and support future longitudinal and mechanistic studies. Patients with a germline P-LP variant should be closely monitored, regardless of risk group assignment.

Pediatric brain and spinal cancers are collectively the leading disease-related cause of death in children; thus, we urgently need curative therapeutic strategies for these tumors. To accelerate such discoveries, the Children's Brain Tumor Network (CBTN) and Pacific Pediatric Neuro-Oncology Consortium (PNOC) created a systematic process for tumor biobanking, model generation, and sequencing with immediate access to harmonized data. We leverage these data to establish OpenPBTA, an open collaborative project with over 40 scalable analysis modules that genomically characterize 1,074 pediatric brain tumors. Transcriptomic classification reveals universal TP53 dysregulation in mismatch repair-deficient hypermutant high-grade gliomas and TP53 loss as a significant marker for poor overall survival in ependymomas and H3 K28-mutant diffuse midline gliomas. Already being actively applied to other pediatric cancers and PNOC molecular tumor board decision-making, OpenPBTA is an invaluable resource to the pediatric oncology community.

Abstract Background: Neuroblastoma is a childhood cancer that arises from the sympathetic nervous system. Approximately 1% of patients have a family history of disease with causal germline mutations in neuroblastoma predisposition genes, ALK or PHOX2B. Recent genome-wide association studies (GWAS) of sporadic cases have identified over two dozen susceptibility loci, and next-generation sequencing studies estimate that 8-10% of children with cancer harbor a rare pathogenic (P) or likely pathogenic (LP) germline variant in a cancer predisposition gene (CPG). To date, the heritability and clinical significance of germline P/LP variants remains unknown due to a lack of parental germline DNA. Methods: Through the Gabriella Miller Kids First program, we performed whole genome sequencing (WGS) at 30x depth on patient-parent triads (n=457) and dyads (n=99), along with WGS and exome sequencing on matched tumor DNA (n=336) and RNA-sequencing on matched tumor RNA (n=207). Rare variants (allele frequency <0.1% in ExAC, 1000 Genomes, and gnomAD) in a predefined set of CPGs (n=197) were annotated, and pathogenicity was assessed using ClinVar, InterVar, and manual review. Gene-based enrichment was performed by comparison to gnomAD WGS data (n=143,068), excluding TCGA samples. Heritability was evaluated using family-based variant calling. Tumor DNA sequencing was analyzed for second hits or somatic enrichment of the germline P/LP variant. Tumor RNA sequencing was interrogated to identify expressed P/LP variants and preferential allelic expression. Ongoing analyses are utilizing polygenic risk scores from our GWAS study to inform tumor penetrance. Results: We observed 78 P/LP germline variants in CPGs in 75 probands (13.5%). Of the 72 probands with trio data, 95% of the P/LP variants were inherited (54% maternal, 46% paternal). Several CPGs showed enrichment of P/LP variants, including BARD1 (p=0.001; OR 16.16; 95% CI 3.21-50.45). We observed one canonical ALK mutation (R1275Q), but no PHOX2B mutations. For patients with corresponding tumor samples, all germline P/LP variants were observed in the tumor DNA. Germline P/LP variants were associated with high-risk disease as defined by risk group (high vs. low/intermediate, p=0.005), INRG stage (stage M vs stage L1/L2/MS, p=0.024), and MYCN amplification status (amplified vs not amplified, p=0.016). Conclusions: Here we show that approximately 13.5% of patients with neuroblastoma harbor a rare P/LP germline variant in a CPG, and the vast majority of these are inherited. Neuroblastoma patients with P/LP germline variants are more likely to have high-risk disease and several variants suggest potential therapeutic opportunities. Work is ongoing to understand the genetic factors that explain why parents harboring the same P/LP variant did not develop neuroblastoma, and to determine the genetic counseling implications of these data. Citation Format: Emily Blauel, Zalman Vaksman, Alex Lee, Rebecca Kaufman, Laura Egolf, Andrew Olshan, John Maris, Diskin Sharon. Heritability of cancer predisposition gene mutations in 556 neuroblastoma patients with paired parental DNA whole genome sequences [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 3030.

Motivation: Despite widespread prevalence of somatic structural variations (SVs) across most tumor types, understanding of their molecular implications often remains poor. SVs are extremely heterogeneous in size and complexity, hindering the interpretation of their pathogenic role. Tools integrating large SV datasets across platforms are required to fully characterize the cancer's somatic landscape. Results: svpluscnv R package is a swiss army knife for the integration and interpretation of orthogonal datasets including copy number variant segmentation profiles and sequencing-based structural variant calls. The package implements analysis and visualization tools to evaluate chromosomal instability and ploidy, identify genes harboring recurrent SVs and detects complex rearrangements such as chromothripsis and chromoplexia. Further, it allows systematic identification of hot-spot shattered genomic regions, showing reproducibility across alternative detection methods and datasets.

Accelerating cures for children with cancer remains an immediate challenge due to extensive oncogenic heterogeneity between and within histologies, distinct molecular mechanisms evolving between diagnosis and relapsed disease, and limited therapeutic options. To systematically prioritize and rationally test novel agents in preclinical murine models, researchers within the Pediatric Preclinical Testing Consortium developed over 370 patient-derived xenografts (PDXs) from high-risk childhood cancers, many refractory to current standard-of-care treatments. Here, we genomically characterize 261 PDX models from 29 unique pediatric cancer malignancies and demonstrate faithful recapitulation of histologies, subtypes, and refine our understanding of relapsed disease. Expression and mutational signatures are used to classify tumors for TP53 and NF1 inactivation, as well as impaired DNA repair. We anticipate these data will serve as a resource for pediatric cancer drug development and guide rational clinical trial design for children with cancer.nnHighlightsO_LIMultiplatform genomic analysis defines landscape of 261 pediatric cancer patient derived xenograft (PDX) modelsnC_LIO_LIPediatric patient derived xenografts faithfully recapitulate relapsed diseasenC_LIO_LIInferred TP53 pathway inactivation correlates with pediatric cancer copy number burdennC_LIO_LISomatic mutational signatures predict impaired DNA repair across multiple histologiesnC_LI

Accelerating cures for children with cancer remains an immediate challenge as a result of extensive oncogenic heterogeneity between and within histologies, distinct molecular mechanisms evolving between diagnosis and relapsed disease, and limited therapeutic options. To systematically prioritize and rationally test novel agents in preclinical murine models, researchers within the Pediatric Preclinical Testing Consortium are continuously developing patient-derived xenografts (PDXs)—many of which are refractory to current standard-of-care treatments—from high-risk childhood cancers. Here, we genomically characterize 261 PDX models from 37 unique pediatric cancers; demonstrate faithful recapitulation of histologies and subtypes; and refine our understanding of relapsed disease. In addition, we use expression signatures to classify tumors for TP53 and NF1 pathway inactivation. We anticipate that these data will serve as a resource for pediatric oncology drug development and will guide rational clinical trial design for children with cancer.

Neuroblastoma is a cancer of the developing sympathetic nervous system. It is diagnosed in 600-700 children per year in the United States and accounts for 12% of pediatric cancer deaths. Despite recent advances in our understanding of this malignancy's complex genetic architecture, the contribution of rare germline variants remains undefined. Here, we conducted a genome-wide analysis of large (>500 kb), rare (<1%) germline copy number variants (CNVs) in two independent, multi-ethnic cohorts totaling 5,585 children with neuroblastoma and 23,505 cancer-free control children. We identified a 550-kb deletion on chromosome 16p11.2 significantly enriched in neuroblastoma cases (0.39% of cases and 0.03% of controls; p = 3.34 × 10-9). Notably, this CNV corresponds to a known microdeletion syndrome that affects approximately one in 3,000 children and confers risk for diverse developmental phenotypes including autism spectrum disorder and other neurodevelopmental disorders. The CNV had a substantial impact on neuroblastoma risk, with an odds ratio of 13.9 (95% confidence interval = 5.8-33.4). The association remained significant when we restricted our analysis to individuals of European ancestry in order to mitigate potential confounding by population stratification (0.42% of cases and 0.03% of controls; p = 4.10 × 10-8). We used whole-genome sequencing (WGS) to validate the deletion in paired germline and tumor DNA from 12 cases. Finally, WGS of four parent-child trios revealed that the deletion primarily arose de novo without maternal or paternal bias. This finding expands the clinical phenotypes associated with 16p11.2 microdeletion syndrome to include cancer, and it suggests that disruption of the 16p11.2 region may dysregulate neurodevelopmental pathways that influence both neurological phenotypes and neuroblastoma.