Loss of heterozygosity does not occur in BRCA1/2 mutant pediatric solid and central nervous system tumors.

Utilization of tumor-only sequencing has expanded in pediatric cancer patients, which can lead to identification of pathogenic variants in genes that may be germline and/or have uncertain relevance to the tumor in question, such as the homologous recombination (HR) pathway genes BRCA1/2. We identified patients with pathogenic BRCA1/2 mutations from somatic tumor sequencing, and performed additional germline sequencing to assess for the presence of loss of heterozygosity (LOH). Of seven patients identified, four (57.1%) mutations were found in the germline and none had associated LOH. Our data suggest that BRCA1/2 mutations identified in this context are likely incidental findings.

Rare FGFR Oncogenic Alterations in Sequenced Pediatric Solid and Brain Tumors Suggest FGFR Is a Relevant Molecular Target in Childhood Cancer.

PURPOSE: Multiple FGFR inhibitors are currently in clinical trials enrolling adults with different solid tumors, while very few enroll pediatric patients. We determined the types and frequency of FGFR alterations (FGFR1-4) in pediatric cancers to inform future clinical trial design. METHODS: Tumors with FGFR alterations were identified from two large cohorts of pediatric solid tumors subjected to targeted DNA sequencing: The Dana-Farber/Boston Children's Profile Study (n = 888) and the multi-institution GAIN/iCAT2 (Genomic Assessment Improves Novel Therapy) Study (n = 571). Data from the combined patient population of 1,395 cases (64 patients were enrolled in both studies) were reviewed and cases in which an FGFR alteration was identified by OncoPanel sequencing were further assessed. RESULTS: We identified 41 patients with tumors harboring an oncogenic FGFR alteration. Median age at diagnosis was 8 years (range, 6 months-26 years). Diagnoses included 11 rhabdomyosarcomas, nine low-grade gliomas, and 17 other tumor types. Alterations included gain-of-function sequence variants (n = 19), amplifications (n = 10), oncogenic fusions (FGFR3::TACC3 [n = 3], FGFR1::TACC1 [n = 1], FGFR1::EBF2 [n = 1], FGFR1::CLIP2 [n = 1], and FGFR2::CTNNA3 [n = 1]), pathogenic-leaning variants of uncertain significance (n = 4), and amplification in combination with a pathogenic-leaning variant of uncertain significance (n = 1). Two novel FGFR1 fusions in two different patients were identified in this cohort, one of whom showed a response to an FGFR inhibitor. CONCLUSION: In summary, activating FGFR alterations were found in approximately 3% (41/1,395) of pediatric solid tumors, identifying a population of children with cancer who may be eligible and good candidates for trials evaluating FGFR-targeted therapy. Importantly, the genomic and clinical data from this study can help inform drug development in accordance with the Research to Accelerate Cures and Equity for Children Act.

Molecular profiling identifies targeted therapy opportunities in pediatric solid cancer.

To evaluate the clinical impact of molecular tumor profiling (MTP) with targeted sequencing panel tests, pediatric patients with extracranial solid tumors were enrolled in a prospective observational cohort study at 12 institutions. In the 345-patient analytical population, median age at diagnosis was 12 years (range 0-27.5); 298 patients (86%) had 1 or more alterations with potential for impact on care. Genomic alterations with diagnostic, prognostic or therapeutic significance were present in 61, 16 and 65% of patients, respectively. After return of the results, impact on care included 17 patients with a clarified diagnostic classification and 240 patients with an MTP result that could be used to select molecularly targeted therapy matched to identified alterations (MTT). Of the 29 patients who received MTT, 24% had an objective response or experienced durable clinical benefit; all but 1 of these patients received targeted therapy matched to a gene fusion. Of the diagnostic variants identified in 209 patients, 77% were gene fusions. MTP with targeted panel tests that includes fusion detection has a substantial clinical impact for young patients with solid tumors.

Data sharing to improve concordance in variant interpretation across laboratories: results from the Canadian Open Genetics Repository.

BACKGROUND: This study aimed to identify and resolve discordant variant interpretations across clinical molecular genetic laboratories through the Canadian Open Genetics Repository (COGR), an online collaborative effort for variant sharing and interpretation. METHODS: Laboratories uploaded variant data to the Franklin Genoox platform. Reports were issued to each laboratory, summarising variants where conflicting classifications with another laboratory were noted. Laboratories could then reassess variants to resolve discordances. Discordance was calculated using a five-tier model (pathogenic (P), likely pathogenic (LP), variant of uncertain significance (VUS), likely benign (LB), benign (B)), a three-tier model (LP/P are positive, VUS are inconclusive, LB/B are negative) and a two-tier model (LP/P are clinically actionable, VUS/LB/B are not). We compared the COGR classifications to automated classifications generated by Franklin. RESULTS: Twelve laboratories submitted classifications for 44 510 unique variants. 2419 variants (5.4%) were classified by two or more laboratories. From baseline to after reassessment, the number of discordant variants decreased from 833 (34.4% of variants reported by two or more laboratories) to 723 (29.9%) based on the five-tier model, 403 (16.7%) to 279 (11.5%) based on the three-tier model and 77 (3.2%) to 37 (1.5%) based on the two-tier model. Compared with the COGR classification, the automated Franklin classifications had 94.5% sensitivity and 96.6% specificity for identifying actionable (P or LP) variants. CONCLUSIONS: The COGR provides a standardised mechanism for laboratories to identify discordant variant interpretations and reduce discordance in genetic test result delivery. Such quality assurance programmes are important as genetic testing is implemented more widely in clinical care.

Real-World Performance of a Comprehensive Genomic Profiling Test Optimized for Small Tumor Samples.

PURPOSE: Tissue-based comprehensive genomic profiling (CGP) is increasingly used for treatment selection in patients with advanced cancer; however, tissue availability may limit widespread implementation. Here, we established real-world CGP tissue availability and assessed CGP performance on consecutively received samples. MATERIALS AND METHODS: We conducted a post hoc, nonprespecified analysis of 32,048 consecutive tumor tissue samples received for StrataNGS, a multiplex polymerase chain reaction (PCR)-based comprehensive genomic profiling (PCR-CGP) test, as part of an ongoing observational trial (NCT03061305). Sample characteristics and PCR-CGP performance were assessed across all tested samples, including exception samples not meeting minimum input quality control (QC) requirements (< 20% tumor content [TC], < 2 mm2 tumor surface area [TSA], DNA or RNA yield < 1 ng/µL, or specimen age > 5 years). Tests reporting ≥ 1 prioritized alteration or meeting TC and sequencing QC were considered successful. For prostate carcinoma and lung adenocarcinoma, tests reporting ≥ 1 actionable or informative alteration or meeting TC and sequencing QC were considered actionable. RESULTS: Among 31,165 (97.2%) samples where PCR-CGP was attempted, 10.7% had < 20% TC and 59.2% were small (< 25 mm2 tumor surface area). Of 31,101 samples evaluable for input requirements, 8,089 (26.0%) were exceptions not meeting requirements. However, 94.2% of the 31,101 tested samples were successfully reported, including 80.5% of exception samples. Positive predictive value of PCR-CGP for ERBB2 amplification in exceptions and/or sequencing QC-failure breast cancer samples was 96.7%. Importantly, 84.0% of tested prostate carcinomas and 87.9% of lung adenocarcinomas yielded results informing treatment selection. CONCLUSION: Most real-world tissue samples from patients with advanced cancer desiring CGP are limited, requiring optimized CGP approaches to produce meaningful results. An optimized PCR-CGP test, coupled with an inclusive exception testing policy, delivered reportable results for > 94% of samples, potentially expanding the proportion of CGP-testable patients and impact of biomarker-guided therapies.

Development and Validation of StrataNGS, a Multiplex PCR, Semiconductor Sequencing-Based Comprehensive Genomic Profiling Test.

Despite widespread use in targeted tumor testing, multiplex PCR/semiconductor (Ion Torrent) sequencing-based assessment of all comprehensive genomic profiling (CGP) variant classes has been limited. Herein, we describe the development and validation of StrataNGS, a 429-gene, multiplex PCR/semiconductor sequencing-based CGP laboratory-developed test performed on co-isolated DNA and RNA from formalin-fixed, paraffin-embedded tumor specimens with ≥2 mm2 tumor surface area. Validation was performed in accordance with MolDX CGP validation guidelines using 1986 clinical formalin-fixed, paraffin-embedded samples and an in-house developed optimized bioinformatics pipeline. Across CGP variant classes, accuracy ranged from 0.945 for tumor mutational burden (TMB) status to >0.999 for mutations and gene fusions, positive predictive value ranged from 0.915 for TMB status to 1.00 for gene fusions, and reproducibility ranged from 0.998 for copy number alterations to 1.00 for splice variants and insertions/deletions. StrataNGS TMB estimates were highly correlated to those from whole exome- or FoundationOne CDx-determined TMB (Pearson r = 0.998 and 0.960, respectively); TMB reproducibility was 0.996 (concordance correlation coefficient). Limit of detection for all variant classes was <20% tumor content. Together, we demonstrate that multiplex PCR/semiconductor sequencing-based tumor tissue CGP is feasible using optimized bioinformatic approaches described herein.

Invasive squamous cell carcinomas and precursor lesions on UV-exposed epithelia demonstrate concordant genomic complexity in driver genes.

Although squamous cell carcinomas (SCC) are the most frequent human solid tumor at many anatomic sites, the driving molecular alterations underlying their progression from precursor lesions are poorly understood, especially in the context of photodamage. Therefore, we used high-depth, targeted next-generation sequencing (NGS) of RNA and DNA from routine tissue samples to characterize the progression of both well- (cutaneous) and poorly (ocular) studied SCCs. We assessed 56 formalin-fixed paraffin-embedded (FFPE) cutaneous lesions (n = 8 actinic keratosis, n = 30 carcinoma in situ [CIS], n = 18 invasive) and 43 FFPE ocular surface lesions (n = 2 conjunctival/corneal intraepithelial neoplasia, n = 20 CIS, n = 21 invasive), from institutions in the US and Brazil. An additional seven cases of advanced cutaneous SCC were profiled by hybrid capture-based NGS of >1500 genes. The cutaneous and ocular squamous neoplasms displayed a predominance of UV-signature mutations. Precursor lesions had highly similar somatic genomic landscapes to SCCs, including chromosomal gains of 3q involving SOX2, and highly recurrent mutations and/or loss of heterozygosity events affecting tumor suppressors TP53 and CDKN2A. Additionally, we identify a novel molecular subclass of CIS with RB1 mutations. Among TP53 wild-type tumors, human papillomavirus transcript was detected in one matched pair of cutaneous CIS and SCC. Amplicon-based whole-transcriptome sequencing of select 20 cutaneous lesions demonstrated significant upregulation of pro-invasion genes in cutaneous SCCs relative to precursors, including MMP1, MMP3, MMP9, LAMC2, LGALS1, and TNFRSF12A. Together, ocular and cutaneous squamous neoplasms demonstrate similar alterations, supporting a common model for neoplasia in UV-exposed epithelia. Treatment modalities useful for cutaneous SCC may also be effective in ocular SCC given the genetic similarity between these tumor types. Importantly, in both systems, precursor lesions possess the full complement of major genetic changes seen in SCC, supporting non-genetic drivers of invasiveness.

Next-generation sequencing identifies recurrent copy number variations in invasive breast carcinomas from Ghana.

African and African-American (AA) women have higher incidence of triple-negative breast cancers (TNBC) with high histological grade and aggressive clinical behavior, but the reasons are not fully understood. We recently found that the oncogenic protein EZH2 is overexpressed in Ghanaian breast cancer patients, with 16% of the tumors expressing cytoplasmic EZH2. Understanding the molecular underpinnings of these aggressive tumors may lead to the identification of potential targetable oncogenic drivers. We characterized the copy number variations of 11 Ghanaian breast tumor patients by targeted multiplexed PCR-based DNA next-generation sequencing (NGS) over 130 cancer-relevant genes. While the DNA quality was not optimal for mutation analysis, 90% of the tumors had frequent recurrent copy number alterations (CNAs) of 17 genes: SDHC, RECQL4, TFE3, BCL11A, BCL2L1, PDGFRA, DEK, SMUG1, AKT3, SMARCA4, VHL, KLF6, CCNE1, G6PD, FGF3, ABL1, and CCND1, with the top oncogenic functions being mitotic G1-G1/S-phase regulation, gene transcription, apoptosis, and PI3K/AKT pathway. The most common recurrent high-level CNAs were gains of RECQL4 and SDHC, in 50% and 60% of cases, respectively. Network analyses revealed a significant predicted interaction among 12 of the 17 (70.6%) genes with high-level CNAs (p = 5.7E-07), which was highly correlated with EZH2 expression (r = 0.4-0.75). By immunohistochemistry, RECQL4 and SDHC proteins were upregulated in 53 of 86 (61.6%) and 48 of 86 (56%) of Ghanaian invasive carcinoma tissue samples. In conclusion, our data show that invasive carcinomas from Ghana exhibit recurrent CNAs in 17 genes, with functions in oncogenic pathways, including PI3K/AKT and G1-G1/S regulation, which may have implications for the biology and treatment of invasive carcinomas in African and AA women.

Multiclonality and Marked Branched Evolution of Low-Grade Endometrioid Endometrial Carcinoma.

The molecular events driving low-grade endometrioid endometrial carcinoma (LGEC) development-like in many cancers-are incompletely understood. Hence, here we performed multiregion, comprehensive somatic molecular profiling of routinely processed formalin-fixed, paraffin-embedded (FFPE) material from 13 cases of LGEC totaling 64 minute, spatially defined cell populations ranging from presumed precursor lesions through invasive LGEC. Shared driving PTEN, PIK3R1, or PIK3CA mutations support clonal origin of the samples in each case, except for two cases with two clonally distinct neoplastic populations, consistent with unexpected multiclonality in LGEC development. Although substantial heterogeneity in driving somatic alterations was present across populations in nearly all cases, these alterations were usually clonal in a given population, supporting continued selection and clonal sweeping of driving alterations in populations with both precursor and LGEC histology. Importantly, CTNNB1 mutational status, which has been proposed as both prognostic and predictive in LGEC, was frequently heterogeneous and subclonal, occurring both exclusively in precursor or cancer populations in different cases. Whole-transcriptome profiling of coisolated RNA from 12 lesions (from 5 cases) was robust and confirmed histologic and molecular heterogeneity, including activated Wnt signaling in CTNNB1-mutant versus wild-type populations. Taken together, we demonstrate clinically relevant multiclonality and intratumoral heterogeneity during LGEC development with important implications for diagnosis, prognosis, and therapeutic prediction. More broadly, our methodology is broadly scalable to enable high-throughput genomic and transcriptomic characterization of precursor and invasive cancer populations from routine FFPE specimens. IMPLICATIONS: Multiregion profiling of LGEC populations using a highly scalable approach demonstrates clinically relevant multiclonality and intratumoral heterogeneity.

Effect of Loading Method on a Peptide Substrate Reporter in Intact Cells.

Studies of live cells often require loading of exogenous molecules through the cell membrane; however, effects of loading method on experimental results are poorly understood. Therefore, in this work, we compared three methods for loading a fluorescently labeled peptide into cells of the model organism Dictyostelium discoideum. We optimized loading by pinocytosis, electroporation, and myristoylation to maximize cell viability and characterized loading efficiency, localization, and uniformity. We also determined how the loading method affected measurements of enzyme activity on the peptide substrate reporter using capillary electrophoresis. Loading method had a strong effect on the stability and phosphorylation of the peptide. The half-life of the intact peptide in cells was 19 ± 2, 53 ± 15, and 12 ± 1 min, for pinocytosis, electroporation, and myristoylation, respectively. The peptide was phosphorylated only in cells loaded by electroporation. Fluorescence microscopy suggested that the differences between methods were likely due to differences in peptide localization.

Targeted DNA and RNA Sequencing of Paired Urothelial and Squamous Bladder Cancers Reveals Discordant Genomic and Transcriptomic Events and Unique Therapeutic Implications.

BACKGROUND: Integrated molecular profiling has identified intrinsic expression-based bladder cancer molecular subtypes. Despite frequent histological diversity, robustness of subtypes in paired conventional (urothelial) and squamous components of the same bladder tumor has not been reported. OBJECTIVE: To assess the impact of histological heterogeneity on expression-based bladder cancer subtypes. DESIGN, SETTING, AND PARTICIPANTS: We performed clinically applicable, targeted DNA and/or RNA sequencing (multiplexed DNA and RNA sequencing [mxDNAseq and mxRNAseq, respectively]) on 112 formalin-fixed paraffin-embedded (FFPE) bladder cancer samples, including 12 cases with paired urothelial/squamous components and 21 bladder cancer cell lines. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Unsupervised hierarchical and consensus clustering of target gene expression enabled derivation of basal/luminal molecular subtyping. RESULTS AND LIMITATION: Across 21 bladder cancer cell lines, our custom mxRNAseq panel was highly concordant with whole transcriptome sequencing, and assessed targets robustly determined expression-based basal/luminal subtypes from The Cancer Genome Atlas data (in silico) and internally sequenced FFPE tissues. Frequent deleterious TP53 (56%) and activating hotspot PIK3CA (30%) somatic mutations were seen across 69 high-quality tissue samples. Potentially targetable focal ERBB2 (6%) or EGFR (6%) amplifications were also identified, and a novel subgene copy-number detection approach is described. Combined DNA/RNA analysis showed that focally amplified samples exhibit outlier EGFR and ERBB2 expression distinct from subtype-intrinsic profiles. Critically, paired urothelial and squamous components showed divergent basal/luminal status in three of 12 cases (25%), despite identical putatively clonal prioritized somatic genomic alterations. Limitations include lack of profiled paired normal tissues for formal somatic alteration determination, and the need for formal analytical and clinical validation. CONCLUSIONS: Our results support the feasibility of clinically relevant integrative bladder cancer profiling and challenge the intrinsic nature of expression subtypes in histologically diverse bladder cancers. PATIENT SUMMARY: A targeted RNA sequencing assay is capable of assessing gene expression-based subtypes in individual components of clinical bladder cancer tissue specimens. Different histological components of the same tumor may yield divergent expression profiles, suggesting that expression-based subtypes should be interpreted with caution in heterogeneous cancers.

Comprehensive Molecular Profiling of Olfactory Neuroblastoma Identifies Potentially Targetable FGFR3 Amplifications.

Olfactory neuroblastomas (ONBs), also known as esthesioneuroblastomas, are malignant round-cell tumors that represent up to 5% of sinonasal malignancies. Despite their aggressive course, molecular studies of ONBs have been limited, and targeted therapies are lacking. To identify potential oncogenic drivers and targetable pathways in ONBs, we characterized 20 ONBs, including archived ONBs profiled by targeted, multiplexed PCR (mxPCR)-based DNA next-generation sequencing (NGS) of the coding sequence of over 400 cancer-relevant genes (n = 16), mxPCR-based RNA NGS of 108 target genes (n = 15), and 2 ONBs profiled by comprehensive hybrid-capture-based clinical grade NGS of >1,500 genes. Somatic mutations were infrequent in our cohort, with 7 prioritized nonsynonymous mutations in 5 of 18 (28%) ONBs, and no genes were recurrently mutated. We detected arm/chromosome-level copy-number alterations in all tumors, most frequently gains involving all or part of chromosome 20, chromosome 5, and chromosome 11. Recurrent focal amplifications, often but not exclusively in the context of arm-level gains, included CCND1 [n = 4/18 (22%) tumors] and the targetable receptor tyrosine kinase FGFR3 [n = 5/18 (28%) tumors]. Targeted RNA NGS confirmed high expression of FGFR3 in ONB (at levels equivalent to bladder cancer), with the highest expression observed in FGFR3-amplified ONB cases. Importantly, our findings suggest that FGFR3 may be a therapeutic target in a subset of these aggressive tumors.Implications: ONBs harbor recurrent chromosomal copy-number changes, including FGFR3 amplification associated with overexpression. Hence, FGFR3 may represent a novel therapeutic target in these tumors. Mol Cancer Res; 15(11); 1551-7. ©2017 AACR.

Molecular Profiling of Multiple Primary Merkel Cell Carcinoma to Distinguish Genetically Distinct Tumors From Clonally Related Metastases.

Importance: Merkel cell carcinoma (MCC) is an aggressive cutaneous neuroendocrine carcinoma. In rare cases, the development of an additional cutaneous MCC tumor is clinically consistent with a second primary MCC tumor rather than a cutaneous metastasis, which has important treatment and prognostic implications. Objective: To evaluate genetic relatedness in 4 cases with the clinical diagnosis of multiple primary MCCs. Design, Setting, and Participants: In this case series, 7 cases of clinically designated multiple primary MCC were identified; 4 cases met inclusion criteria for next-generation sequencing (NGS) analysis. Mutations, copy number alterations, and Merkel cell polyomavirus (MCPyV) sequence were analyzed and compared between clinically designated multiple primary tumors to characterize genetic relatedness and hence assess clonality. Patients with clinically designated multiple primary MCC were identified from the multidisciplinary MCC Program at the University of Michigan, a tertiary care center. Main Outcomes and Measures: Four cases of clinically designated multiple primary MCC were characterized by tumor sequencing and targeted MCPyV sequencing to distinguish independent primary tumors from related metastases. Results: Overall, 4 patients in their 70s or 80s were included and analyzed. Cases 1 and 4 were verified as genetically distinct primary tumors and did not harbor similar copy number alterations or demonstrate significant mutational overlap. Cases 2 and 3 were designated as clonally related based on overlapping copy number alterations. In clonally related tumors, chromosomal copy number changes were more reliable than mutations for demonstrating clonality. Regardless of clonality, we found that MCPyV status was concordant for all tumor pairs and MCPyV positive tumors harbored predominatly subclonal mutations. Conclusions and Relevance: Our findings suggest that patients with MCC may develop a second genetically distinct primary tumor; in this case, the subsequent tumor is likely to develop through similar mechanisms of pathogenesis, either MCPyV-mediated or ultraviolet light-mediated. Next-generation sequencing analysis of chromosomal copy number changes and mutations is useful in distinguishing multiple primary MCCs from progression of MCC clinically resembling multiple primaries, allowing appropriate staging of the patient.

Molecular Profiling to Determine Clonality of Serial Magnetic Resonance Imaging/Ultrasound Fusion Biopsies from Men on Active Surveillance for Low-Risk Prostate Cancer.

Purpose: To determine whether MRI/ultrasound (MRI/US) fusion biopsy facilitates longitudinal resampling of the same clonal focus of prostate cancer and to determine whether high-grade cancers can evolve from low-grade clones.Experimental Design: All men on active surveillance who underwent tracking MRI/US fusion biopsy of Gleason 6 prostate cancer, on at least two distinct occasions, between 2012 and 2014 were enrolled. MRI/US fusion was used to track and resample specific cancer foci. IHC for ERG and targeted RNA/DNA next-generation sequencing (NGS) were performed on formalin-fixed paraffin-embedded prostate biopsy specimens to assess clonality.Results: Thirty-one men with median age and PSA of 65 years and 4.6 ng/mL, respectively, were analyzed. The median sampling interval was 12 months (range, 5-35). Of the 26 evaluable men, ERG IHC concordance was found between initial and repeat biopsies in 25 (96%), indicating resampling of the same clonal focus over time. Targeted NGS supported ERG IHC results and identified unique and shared driving mutations, such as IDH1 and SPOP, in paired specimens. Of the nine men (34.6%) who were found to have Gleason ≥7 on repeat biopsy, all displayed temporal ERG concordance. Prioritized genetic alterations were detected in 50% (13/26) of paired samples. Oncogenic mutations were detected in 22% (2/9) of Gleason 6 cancers prior to progression and 44% (4/9) of Gleason ≥7 cancers when progression occurred.Conclusions: Precise tracking of prostate cancer foci via MRI/US fusion biopsy allowed subsequent resampling of the same clonal focus of cancer over time. Further research is needed to clarify the grade progression potential of Gleason 6 prostate cancer. Clin Cancer Res; 23(4); 985-91. ©2016 AACR.

Targeted next-generation sequencing of CIC-DUX4 soft tissue sarcomas demonstrates low mutational burden and recurrent chromosome 1p loss.

Gene fusions between CIC and DUX4 define a rare class of soft tissue sarcomas poorly understood at the molecular level. Previous karyotyping and fluorescence in situ hybridization studies support chromosome 8 trisomy as a recurrent alteration; however, other driving alterations are largely unknown. Thus, we analyzed 11 formalin-fixed, paraffin-embedded CIC-DUX4 sarcoma tissue samples (including 3 sample pairs) using targeted Ion Torrent-based multiplexed polymerase chain reaction next-generation sequencing to characterize potential somatic driver alterations in 409 genes. Although we did not identify recurrent somatic mutations (point mutations or insertions/deletions), copy number analysis showed recurrent, broad copy number alterations, including gain of chromosome 8 and loss of 1p. In one sample pair (untreated primary and local recurrence resections), we identified similar copy number profiles and a somatic ARID1A R963X nonsense mutation exclusively in the local recurrence sample. In another sample pair (pre- and post-radiation treatment specimens), we observed single-copy loss of chromosome 7q exclusively in the posttreatment recurrence sample, supporting it as an acquired event after radiation treatment. In the last sample pair (near-concurrent, postchemotherapy primary and distant metastasis), molecular profiles were highly concordant, consistent with limited intertumoral heterogeneity. In summary, next-generation sequencing identified limited somatic driver mutations in CIC-DUX4 sarcomas. However, we identified novel, recurrent copy number alterations, including chromosome 1p, which is also the locus of ARID1A. Additional functional work and assessment of larger cohorts are needed to determine the biological and clinical significance of the alterations identified herein.

Microfluidic Chemical Cytometry for Enzyme Assays of Single Cells.

Cellular heterogeneity occurs, and should be probed, at multiple levels of cellular structure and physiology from the genome to enzyme activity. In particular, single-cell measures of protein levels are complemented by single-cell measurements of the activity of these proteins. Microfluidic assays of enzyme activity at the single-cell level combine moderate to high throughput with low dead volumes and the potential for automation. Herein, we describe the steps required to fabricate and operate a microfluidic device for chemical cytometry of fluorescent or fluorogenic reporters of enzyme activity in individual cells.