Azacitidine as epigenetic priming for chemotherapy is safe and well-tolerated in infants with newly diagnosed KMT2A-rearranged acute lymphoblastic leukemia: Children's Oncology Group trial AALL15P1.

Infants less than 1 year old diagnosed with KMT2A-rearranged (KMT2A-r) acute lymphoblastic leukemia (ALL) are at high risk of remission failure, relapse, and death due to leukemia, despite intensive therapies. Infant KMT2A-r ALL blasts are characterized by DNA hypermethylation. Epigenetic priming with DNA methyltransferase inhibitors increases the cytotoxicity of chemotherapy in preclinical studies. The Children's Oncology Group trial AALL15P1 tested the safety and tolerability of five days of azacitidine immediately prior to the start of chemotherapy on day six, in four post-induction chemotherapy courses for infants with newly diagnosed KMT2A-r ALL. The treatment was welltolerated, with only two of 31 evaluable patients (6.5%) experiencing dose-limiting toxicity. Whole genome bisulfite sequencing of peripheral blood mononuclear cells (PBMCs) demonstrated decreased DNA methylation in 87% of samples tested following five days of azacitidine. Event-free survival was similar to prior studies of newly diagnosed infant ALL. Azacitidine is safe and results in decreased DNA methylation of PBMCs in infants with KMT2A-r ALL, but the incorporation of azacitidine to enhance cytotoxicity did not impact survival. Clinicaltrials.gov identifier: NCT02828358.

Genetic heterogeneity and enrichment of variants in DNA-repair genes in ameloblastoma.

OBJECTIVE: Ameloblastomas are a group of relatively common odontogenic tumors that frequently originate from the dental epithelium. These tumors are aggressive in nature and present as slow-growing painless cortical expansion of the jaw. Histologically, the follicular and plexiform subtypes constitute two-thirds of solid/multicystic ameloblastomas. The objective of this study was to understand the genetic architecture of follicular and plexiform ameloblastomas using deep whole-exome sequencing. METHODS: Archived formalin-fixed paraffin-embedded tissue blocks of follicular (n = 4) and plexiform (n = 6) ameloblastomas were retrieved and genomic DNAs were isolated from the tumor tissue dissected from the formalin-fixed paraffin-embedded block. The exomes were enriched using the Integrated DNA Technologies Exome Research Panel (IDT, Coralville, IA) and paired-end sequencing was completed on an Illumina NovaSeq 6000 with an average output of 20 GB of data resulting in a mean coverage of 400×. Variant analysis was completed using custom-developed software: Rapid Understanding of Nucleotide variant Effect Software and variant integration and knowledge interpretation in genomes. RESULTS: Our analyses focused on examining somatic variants (gnomAD minor allele frequency ≤1%) in genes found on an Food and Drug Administration -approved clinical cancer sequencing panel (FoundationOne®CDx). In follicular tumors, variants (>20% of the reads) were identified in BRAF, KMT2D, and ABL1 genes. In plexiform tumors, variants (>20% of the reads) were identified in ALK, BRAF, KRAS, KMT2D, SMO, KMT2A, and BRCA2 genes. Enrichment analysis showed a significant role of DNA repair genes in the development of these tumors. CONCLUSION: The variants identified in follicular and plexiform ameloblastomas were enriched in DNA-repair genes. The observed genetic heterogeneity in these ameloblastomas may contribute to the aggressive nature and recurrence risk of these tumors.

Clinical Validation of Genome Reference Consortium Human Build 38 in a Laboratory Utilizing Next-Generation Sequencing Technologies.

BACKGROUND: Laboratories utilizing next-generation sequencing align sequence data to a standardized human reference genome (HRG). Several updated versions, or builds, have been released since the original HRG in 2001, including the Genome Reference Consortium Human Build 38 (GRCh38) in 2013. However, most clinical laboratories still use GRCh37, which was released in 2009. We report our laboratory's clinical validation of GRCh38. METHODS: Migration to GRCh38 was validated by comparing the coordinates (lifting over) of 9443 internally curated variants from GRCh37 to GRCh38, globally comparing protein coding sequence variants aligned with GRCh37 vs GRCh38 from 917 exomes, assessing genes with known discrepancies, comparing coverage differences, and establishing the analytic sensitivity and specificity of variant detection using Genome in a Bottle data. RESULTS: Eight discrepancies, due to strand swap or reference base, were observed. Three clinically relevant variants had the GRCh37 alternate allele as the reference allele in GRCh38. A comparison of 88 295 calls between builds identified 8 disease-associated genes with sequence differences: ABO, BNC2, KIZ, NEFL, NR2E3, PTPRQ, SHANK2, and SRD5A2. Discrepancies in coding regions in GRCh37 were resolved in GRCh38. CONCLUSIONS: There were a small number of clinically significant changes between the 2 genome builds. GRCh38 provided improved detection of nucleotide changes due to the resolution of discrepancies present in GRCh37. Implementation of GRCh38 results in more accurate and consistent reporting.

Chromosomal Microarray Reinterpretation: Applications to Pediatric Practice.

Chromosomal microarray analysis (CMA) frequently yields inconclusive results. We reexamined inconclusive CMA results from 33 previously tested patients and reached a definitive diagnosis in 3 (9.1%) and identified the need for additional testing in 4 (12.1%). Reinterpretation may resolve inconclusive CMA results.

MYOD1 as a prognostic indicator in rhabdomyosarcoma.

BACKGROUND/OBJECTIVES: Rhabdomyosarcoma (RMS) is characterized by the expression of the myogenic regulatory protein MYOD1. Histologic types include alveolar, embryonal (ERMS), and spindle cell sclerosing RMS (SRMS). SRMS harbors MYOD1 mutations in a subset of adult cases in association with poor prognosis. DESIGN/METHODS: To study the level of MYOD1 protein expression and its clinical significance, we have analyzed variable numbers of pediatric (<18 years of age) and adult (age range ≥18 to 35 years) ERMS and SRMS cases for presence or absence of MYOD1 immunoreactivity in correlation with clinical outcome and MYOD1 L122R mutations. RESULTS: Lack of MYOD1 immunoreactivity, identified in 23.8% of nonalveolar RMS (non-ARMS) cases, was more prevalent in SRMS (44%) than ERMS (17.2%) and was significantly associated with low overall survival and unfavorable tumor sites (p < .05). Lack of MYOD1 immunoreactivity was not associated with MYOD1 L122R mutations, which were identified in 3/37 (8%) cases including only two of 31 (6.5%) pediatric cases, one of 11 or 9% pediatric SRMS, and one case of infant ERMS. CONCLUSION: These studies highlight the prognostic role of MYOD1 in non-ARMS. Lack of MYOD1 immunoreactivity is associated with poor prognosis in ERMS and SRMS. MYOD1 gene mutations are generally infrequent in pediatric RMS. Although mutations are predominant in SRMS, they may exceptionally occur in infantile ERMS.

Reinterpretation of Chromosomal Microarrays with Detailed Medical History.

OBJECTIVE: To investigate the utility of a detailed medical history in the interpretation of chromosomal microarray results for pediatric patients with a constitutional disease. STUDY DESIGN: A retrospective review and reinterpretation of test results from chromosomal microarrays performed from 2011 to 2013. Previously reported genetic variants were reanalyzed after review of the patient's complete electronic medical record (cEMR). A 3-tier system was used for reclassification of variants: pathogenic or likely pathogenic (P/LP); variant of uncertain significance (VUS); or benign or likely benign (B/LB). RESULTS: Over an 18-month period, 998 patients with chromosomal microarray results were identified. The most common reasons for chromosomal microarray testing were developmental delay (n = 336), autism spectrum disorder (n = 241), and seizures (n = 143). Chromosomal microarray testing identified 1 or more variants in 48% (482 of 998) of patients; 516 patients had a negative report. For the 482 patients with variants, the original interpretations were composed of 19.3% P/LP (93 of 482), 44.8% VUS (216 of 482), and 35.9% B/LB (173 of 482) variants. After review of the cEMR, 34% of patient results (164 of 482) were changed in interpretation. One case changed from B/LB to VUS, 7 VUS were upgraded to P/LP, and 156 VUS were downgraded to B/LB. No P/LP variants had a change in interpretation. CONCLUSIONS: Overall, 16.4% (164 of 998) of patients with chromosomal microarray testing had a change in interpretation. Access to the patient's cEMR improves the interpretation of chromosomal microarrays by decreasing the number of uncertain (VUS) interpretations.

Occurrence and characterization of medulloblastoma in a patient with Curry-Jones syndrome.

Medulloblastoma in a Patient with Curry-Jones Syndrome with a mosaic variant, c.1234C > T (p.Leu412Phe), in SMO.

Outcomes of Hematopoietic Cell Transplantation in Patients with Germline SAMD9/SAMD9L Mutations.

Germline mutations in SAMD9 and SAMD9L genes cause MIRAGE (myelodysplasia, infection, restriction of growth, adrenal hypoplasia, genital phenotypes, and enteropathy) (OMIM: *610456) and ataxia-pancytopenia (OMIM: *611170) syndromes, respectively, and are associated with chromosome 7 deletions, myelodysplastic syndrome (MDS), and bone marrow failure. In this retrospective series, we report outcomes of allogeneic hematopoietic cell transplantation (HCT) in patients with hematologic disorders associated with SAMD9/SAMD9L mutations. Twelve patients underwent allogeneic HCT for MDS (n = 10), congenital amegakaryocytic thrombocytopenia (n = 1), and dyskeratosis congenita (n = 1). Exome sequencing revealed heterozygous mutations in SAMD9 (n = 6) or SAMD9L (n = 6) genes. Four SAMD9 patients had features of MIRAGE syndrome. Median age at HCT was 2.8 years (range, 1.2 to 12.8 years). Conditioning was myeloablative in 9 cases and reduced intensity in 3 cases. Syndrome-related comorbidities (diarrhea, infections, adrenal insufficiency, malnutrition, and electrolyte imbalance) were present in MIRAGE syndrome cases. One patient with a familial SAMD9L mutation, MDS, and morbid obesity failed to engraft and died of refractory acute myeloid leukemia. The other 11 patients achieved neutrophil engraftment. Acute post-transplant course was complicated by syndrome-related comorbidities in MIRAGE cases. A patient with SAMD9L-associated MDS died of diffuse alveolar hemorrhage. The other 10 patients had resolution of hematologic disorder and sustained peripheral blood donor chimerism. Ten of 12 patients were alive with a median follow-up of 3.1 years (range, 0.1 to 14.7 years). More data are needed to refine transplant approaches in SAMD9/SAMD9L patients with significant comorbidities and to develop guidelines for their long-term follow-up.

Hepatitis C virus genotyping of organ donor samples to aid in transplantation of HCV-positive organs.

Given the availability of new highly efficacious anti-HCV therapies, some clinicians have advocated for wider use of kidneys from hepatitis C virus-positive (HCV+) donors, including transplanting them into HCV-negative recipients. As treatment regimens for HCV are commonly guided by genotype, pretransplant HCV genotyping of tissue donors would be beneficial. To our knowledge, donor HCV genotyping has never been reported. We retrieved archived frozen plasma samples for 17 previous organ donors through a local organ procurement organization. We performed HCV genotyping using the eSensor HCVg Direct Test (GenMark Diagnostics) and also by Sanger sequencing, for confirmation (Retrogen). In addition, viral loads were measured using the COBAS AmpliPrep/TaqMan system (Roche Diagnostics). We found that most of the samples (n = 14) were HCV Genotype 1a with the remainder being Genotype 2b (n = 1) or Genotype 3 (n = 2). All genotyping results were concordant with Sanger sequencing. The average HCV viral load in the sample group was ~ 1.6 million IU/mL (range: ~16 000 IU/mL to 7 million IU/mL). We demonstrate that viral RNA from organ donor plasma can be successfully genotyped for HCV. This ability suggests that transplantation of HCV+ kidneys into HCV-negative recipients, followed by genotype-guided antiviral therapy, could be feasible.

Therapeutic plasma exchange and immunosuppressive therapy in a patient with anti-GAD antibody-related epilepsy: quantification of the antibody response.

Antibodies to glutamic acid decarboxylase (GAD) have been associated with a host of neurological disorders including stiff person syndrome, cerebellar ataxia, limbic encephalitis, and epilepsy. Whether anti-GAD antibodies have an etiological role in these neurological disorders or simply serve as disease markers is unclear. Here, we report a case of a patient with recurrent seizures, poorly responsive to conventional treatment, associated with anti-GAD antibodies. The patient was experiencing near daily seizures at the time of presentation and had marked improvement while receiving immunosuppressive therapy and therapeutic plasma exchange (TPE). We go on to show that the patient had a substantial reduction of her GAD autoantibody burden following this therapy. Using immunostaining, we further demonstrate a progressive loss of GAD reactivity in the patient's sera to neurons and GAD-expressing HELA cells with successive TPEs. Hence, these data support the concept of an immune-mediated pathogenic component to these autoantibody-associated neurological syndromes.

Insulin stimulation of SREBP-1c processing in transgenic rat hepatocytes requires p70 S6-kinase.

Insulin activates sterol regulatory element-binding protein-1c (SREBP-1c) in liver, thereby increasing fatty acid and triglyceride synthesis. We created a line of transgenic rats that produce epitope-tagged human SREBP-1c in liver under control of the constitutive apolipoprotein E promoter/enhancer. This system allows us to dissect the pathway by which insulin stimulates SREBP-1c processing without interference by the insulin-mediated increase in SREBP-1c mRNA. Rats are used because freshly isolated rat hepatocytes respond much more robustly to insulin than do mouse hepatocytes. The data reveal that insulin-mediated stimulation of SREBP-1c processing requires the mechanistic target of rapamycin complex 1 (mTORC1), which also is required for insulin-mediated SREBP-1c mRNA induction. However, in contrast to mRNA induction, insulin stimulation of SREBP-1c processing is blocked by an inhibitor of p70 S6-kinase. The data indicate that the pathways for insulin enhancement of SREBP-1c mRNA and proteolytic processing diverge after mTORC1. Stimulation of processing requires the mTORC1 target p70 S6-kinase, whereas induction of mRNA bypasses this enzyme. Insulin stimulation of both processes is blocked by glucagon. The transgenic rat system will be useful in further defining the molecular mechanism for insulin stimulation of lipid synthesis in liver in normal and diabetic states.

Evaluation of Hi-C sequencing for the detection of gene fusions in hematologic and solid pediatric cancer samples.

HiC sequencing is a DNA-based next-generation sequencing method that preserves the 3D conformation of the genome and has shown promise in detecting genomic rearrangements in translational research studies. To evaluate HiC as a potential clinical diagnostic platform, analytical concordance with routine laboratory testing was assessed using primary pediatric leukemia and sarcoma specimens previously positive for clinically significant genomic rearrangements. Archived specimen types tested included viable and nonviable frozen leukemic cells, as well as formalin-fixed paraffin-embedded (FFPE) tumor tissues. Initially, pediatric acute myeloid leukemia (AML) and alveolar rhabdomyosarcoma (A-RMS) specimens with known genomic rearrangements were subjected to HiC analysis to assess analytical concordance. Subsequently, a discovery cohort consisting of AML and acute lymphoblastic leukemia (ALL) cases with no known genomic rearrangements based on prior clinical diagnostic testing were evaluated to determine whether HiC could detect rearrangements. Using a standard sequencing depth of 50 million raw read-pairs per sample, or approximately 5X raw genomic coverage, 100% concordance was observed between HiC and previous clinical cytogenetic and molecular testing. In the discovery cohort, a clinically relevant gene fusion was detected in 45% of leukemia cases (5/11). This study demonstrates the value of HiC sequencing to medical diagnostic testing as it identified several clinically significant rearrangements, including those that might have been missed by current clinical testing workflows. Key points: HiC sequencing is a DNA-based next-generation sequencing method that preserves the 3D conformation of the genome, facilitating detection of genomic rearrangements.HiC was 100% concordant with clinical diagnostic testing workflows for detecting clinically significant genomic rearrangements in pediatric leukemia and rhabdomyosarcoma specimens.HiC detected clinically significant genomic rearrangements not previously detected by prior clinical cytogenetic and molecular testing.HiC performed well with archived non-viable and viable frozen leukemic cell samples, as well as archived formalin-fixed paraffin-embedded tumor tissue specimens.

Severus: accurate detection and characterization of somatic structural variation in tumor genomes using long reads.

Most current studies rely on short-read sequencing to detect somatic structural variation (SV) in cancer genomes. Long-read sequencing offers the advantage of better mappability and long-range phasing, which results in substantial improvements in germline SV detection. However, current long-read SV detection methods do not generalize well to the analysis of somatic SVs in tumor genomes with complex rearrangements, heterogeneity, and aneuploidy. Here, we present Severus: a method for the accurate detection of different types of somatic SVs using a phased breakpoint graph approach. To benchmark various short- and long-read SV detection methods, we sequenced five tumor/normal cell line pairs with Illumina, Nanopore, and PacBio sequencing platforms; on this benchmark Severus showed the highest F1 scores (harmonic mean of the precision and recall) as compared to long-read and short-read methods. We then applied Severus to three clinical cases of pediatric cancer, demonstrating concordance with known genetic findings as well as revealing clinically relevant cryptic rearrangements missed by standard genomic panels.

Integrated genetic profiling of archival pediatric high-grade glial tumors and reassessment with 2021 WHO classification of paediatric CNS tumours.

Though rare, pediatric high-grade gliomas (pHGG) are a leading cause of cancer-related mortality in children. We wanted to determine whether our currently available clinical laboratory methods could better define diagnosis for pHGG that had been archived at our institution for the past 20 years (1998 to 2017). We investigated 33 formalin-fixed paraffin-embedded pHGG using ThermoFisher Oncoscan SNP microarray with somatic mutation analysis, Sanger sequencing, and whole genome sequencing. These data were correlated with historical histopathological, chromosomal, clinical, and radiological data. Tumors were subsequently classified according to the 2021 WHO Classification of Paediatric CNS Tumours. All 33 tumors were found to have genetic aberrations that placed them within a 2021 WHO subtype and/or provided prognostic information; 6 tumors were upgraded from WHO CNS grade 3 to grade 4. New pHGG genetic features were found including two small cell glioblastomas with H3 G34 mutations not previously described; one tumor with STRN-NTRK2 fusion; and a congenital diffuse leptomeningeal glioneuronal tumor without a chromosomal 1p deletion but with KIAA1549-BRAF fusion. Overall, the combination of laboratory methods yielded key information for tumor classification. Thus, even small studies of these uncommon tumor types may yield new genetic features and possible new subtypes that warrant future investigations.

Perinucleolar Compartment (PNC) Prevalence as an Independent Prognostic Factor in Pediatric Ewing Sarcoma: A Multi-Institutional Study.

The perinucleolar compartment (PNC) is a small nuclear body that plays important role in tumorigenesis. PNC prevalence correlates with poor prognosis and cancer metastasis. Its expression in pediatric Ewing sarcoma (EWS) has not previously been documented. In this study, we analyzed 40 EWS tumor cases from Caucasian and Hispanic patients for PNC prevalence by immunohistochemical detection of polypyrimidine tract binding protein and correlated the prevalence with dysregulated microRNA profiles. EWS cases showed staining ranging from 0 to 100%, which were categorized as diffuse (≥77%, n = 9, high PNC) or not diffuse (<77%, n = 31) for low PNC. High PNC prevalence was significantly higher in Hispanic patients from the US (n = 6, p = 0.017) and in patients who relapsed with metastatic disease (n = 4; p = 0.011). High PNC was associated with significantly shorter disease-free survival and early recurrence compared to those with low PNC. Using NanoString digital profiling, high PNC tumors revealed upregulation of eight and downregulation of 18 microRNAs. Of these, miR-320d and miR-29c-3p had the most significant differential expression in tumors with high PNC. In conclusion, this is the first study that demonstrates the presence of PNC in EWS, reflecting its utility as a predictive biomarker associated with tumor metastasis, specific microRNA profile, Hispanic ethnic origin, and poor prognosis.

NanoString Digital Molecular Profiling of Protein and microRNA in Rhabdomyosarcoma.

PURPOSE: Rhabdomyosarcoma (RMS) exhibits a complex prognostic algorithm based on histologic, biologic and clinical parameters. The embryonal (ERMS) and spindle cell-sclerosing RMS (SRMS) histologic subtypes warrant further studies due to their heterogenous genetic background and variable clinical behavior. NanoString digital profiling methods have been previously highlighted as robust novel methods to detect protein and microRNA expression in several cancers but not in RMS. METHODS/PATIENTS: To identify prognostic biomarkers, we categorized 12 ERMS and SRMS tumor cases into adverse (n = 5) or favorable (n = 7) prognosis groups and analyzed their signaling pathways and microRNA profiles. The digital spatial profiling of protein and microRNA analysis was performed on formalin-fixed, paraffin-embedded (FFPE) tumor tissue using NanoString technology. RESULTS: The detectable expression of several component members of the PI3K/AKT, MAPK and apoptosis signaling pathways was highlighted in RMS, including INPP4B, Pan-AKT, MET, Pan-RAS, EGFR, phospho-p90 RSK, p44/42 ERK1/2, BAD, BCL-XL, cleaved caspase-9, NF1, PARP and p53. Compared to cases with favorable prognosis, the adverse-prognosis tumor samples had significantly increased expression of INPP4B, which was confirmed with traditional immunohistochemistry. The analysis of microRNA profiles revealed that, out of 798 microRNAs assessed, 228 were overexpressed and 134 downregulated in the adverse prognosis group. Significant over-expression of oncogenic/tumor suppressor miR-3144-3p, miR-612, miR-302d-3p, miR-421, miR-548ar-5p and miR-548y (p < 0.05) was noted in the adverse prognosis group. CONCLUSION: This study highlights the utility of NanoString digital profiling methods in RMS, where it can detect distinct molecular signatures with the expression of signaling pathways and microRNAs from FFPE tumor tissue that may help identify prognostic biomarkers of interest. The overexpression of INPP4B and miR-3144-3p, miR-612, miR-302d-3p, miR-421, miR-548y and miR-548ar-5p may be associated with worse overall survival in ERMS and SRMS.

Clinical Validation of Somatic Mutation Detection by the OncoScan CNV Plus Assay.

The OncoScan CNV Plus Assay (OS+) is a single-nucleotide polymorphism microarray platform that can detect 74 hotspot somatic mutations (SMs) in nine genes via molecular inversion probes. We report validation of the SM component of OS+ using a cohort of pediatric high-grade brain tumor specimens. SM calls were generated from 46 brain tumor cases, most tested orthogonally via bidirectional Sanger sequencing. The initial calling algorithm result showed that 31 tumors were positive and 15 were negative for SM, with a total of 71 OS+ SM calls [28 high-confidence (HC) and 43 low-confidence (LC)]. Sanger sequencing was performed for 54 of the 71 calls (27 HC and 27 LC), as well as for 21 randomly selected hotspots across the 15 OS+ negative cases. HC calls (except EGFR) Sanger sequencing confirmed positive, negative calls confirmed negative, but none of the LC calls were Sanger-confirmed positive. An update of the OS+ algorithm resolved the LC calls, but of the 11 HC SM EGFR calls, Sanger sequencing confirmed only one. Two PTEN SM calls by OS+ in two separate cases were also negative per Sanger sequencing. We conclude that a majority of HC OS+ SM calls were accurate, except calls identified in EGFR and PTEN. Clinically, we report SMs identified by OS+ only after Sanger sequencing verification.