Detection Of Copy Number Changes Research Articles

Abstract P1-05-27: Liquid Biopsy for HER2 Status Assessment in Breast Cancer Using Surrogate DNA Methylation Markers

Abstract Background: Emerging HER2-targeted drugs especially antibody–drug conjugates (ADCs) are promising and provide more options for breast cancer management. Current assessment of HER2 status and treatment decisions are mainly dependent on immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) on the primary tumor tissues. With the disease progression, the molecular status of the tumor may evolve and become discordant with the primary site. However, longitudinal monitoring of HER2 status is limited by infeasible repeated sampling of the tumor tissues. A non-invasive and accurate approach to obtaining real-time samples for measuring HER2 alterations is thus an unmet need for surveillance and guiding treatment selection in breast cancer. Detecting HER2 aberration in cell-free DNA (cfDNA) can allow repeated sampling and avoid effects from tumor heterogeneity of tissue biopsy. Previous approaches for HER2 status determination using liquid biopsy were mostly dependent on the detection of copy number changes in cfDNA, but the limited signal-to-noise ratio poses a great challenge to the accuracy and robustness of the tests. In this study, we identified a group of DNA methylation markers for determining HER2 status in cfDNA for breast cancer. Methods: Genome-wide DNA methylation sequencing was conducted in tissue (25 HER2-positive and 35 HER2-negative) and plasma (32 HER2-positive and 107 HER2-negative) samples to identify specific methylation markers for HER2 status. HER2-positive samples were defined by IHC 3+ and 2+ with FISH positive, while HER2-negative ones were IHC 0/1+ and 2+ with FISH negative. Candidate markers were verified in another two sets of plasma samples (1. 30 HER2-positive and 40 HER2-negative; 2. 33 HER2-positive and 53 HER2-negative) by using quantitative methylation-specific PCR (qMSP). The performance of the markers was estimated by the Wilcoxon test, receiver operating characteristic curve, and logistic regression modelling. Results: 36 HER2 status-specific markers were discovered from genome-wide DNA methylation sequencing. Based on the qMSP results, 11 markers were verified by the performance analyses. The individual area under the curve (AUC) of these markers was from 0.58 to 0.68. From logistic regression modelling and 2-fold cross-validation, a 7-marker diagnostic model was built and validated on plasma samples, with the highest AUC of 0.812. Conclusion: cfDNA methylation detection inferring HER2 overexpression is a novel and non-invasive option for monitoring HER2 status in breast cancer patients, with a potential application in response prediction of HER2-targeted treatments. Further validation of the test is undergoing in large multi-centre cohorts in China. Citation Format: Xianyu Zhang, Shiyao Lu, Hui Li, Xin Liu, Jun Wang, Liuhong Zeng, Zhipeng Lu, Siyu Liu, Yanling Yin, Marina Bibikova, Zhiwei Chen, Jian-Bing Fan, Da Pang. Liquid Biopsy for HER2 Status Assessment in Breast Cancer Using Surrogate DNA Methylation Markers [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P1-05-27.

COT-8 DEVELOPMENT OF TARGETED GENE PANEL FOR RAPID MOLECULAR DIAGNOSIS OF BRAIN TUMORS

Abstract Background Brain tumors are diagnosed based on pathological and genetic features defined by WHO classification. Although targeted gene panels are clinically available, most of them do not cover all the necessary genes for the diagnosis of brain tumors. Moreover, broad copy number analysis, which the current WHO classification requires, usually lacks in the gene panel. Another problem is that those panels demand a high burden of time and cost, which disturbs rapid diagnosis and broad application. To overcome those problems, we developed a rapid and cost-effective workflow of molecular diagnosis for brain tumors. Methods Our panel contains 109 genes of which 68 are necessary for fundamental molecular diagnosis and 41 are other common driver genes. To detect copy number changes and structural variants, which generate a fused gene, additional probes are placed on common SNPs and introns containing common breakpoints. MGMT methylation status is examined at the same time using bisulfite-converted DNA amplification. Sequencing data is analyzed using a supercomputer. Results The analysis time is within 4 days: 2 days for library preparation, 1 day for sequencing, and 12 hours for analysis. Detected driver alterations were validated by whole genome sequencing data. MGMT methylation status was correlated between the results of our workflow and pyrosequencing. Conclusions We have developed a rapid comprehensive molecular analysis workflow that detects genetic alterations and MGMT methylation. Our method allows a cost-effective molecular diagnosis with high accuracy, which would improve molecular diagnosis for brain tumors.

P-547 Confined placental mosaicism for inherited segmental aneuploidies in miscarriages traces early karyotype self-correction events

Abstract Study question Does tissue-specific compartmentalization of segmental aneuploidies in first-trimester miscarriages reflect their postzygotic de novo origin or correction of inherited copy number variants (CNV)? Summary answer Most of mosaic CNVs (84%) in spontaneous abortions with normal karyotype arose de novo, but 16% resulted from postzygotic tissue-specific correction of maternally inherited variants. What is known already Chromosomal mosaicism is a hallmark of early human embryogenesis affecting significantly developmental potential of blastocysts, it’s implantation and delivery rates. Most of the currently available data are related to mosaic aneuploidies for a whole chromosome in IVF cycles, whereas little is known about origin and fate of mosaic segmental CNVs due to inherent limitations of NGS and aCGH for detection of copy number changes less for 5-10 Mb in size after single-cell whole genome amplification. Study design, size, duration Chorionic villi (CV) and extraembryonic mesoderm (EM) of miscarriages as well as maternal and paternal peripheral blood DNA samples were evaluated by aCGH+SNP arrays to detect the prevalence and tissue-specific distribution of segmental aneuploidies. As far as CV and EM are derivatives of trophectoderm and inner cell mass lineages, comparative analysis of both tissues allows to investigate the origin of mosaic CNVs by postzygotic de novo appearance or correction of the inherited variants. Participants/materials, setting, methods Eleven trios (mother, father, CV and EM samples from spontaneous abortion with normal karyotype by G-banding) were included in the study. Mean gestational age was 7.9 weeks. Mean maternal and paternal ages were 30.8 and 30.5 years, respectively. aCGH+SNP analysis was performed by SurePrint G3 Human CGH + SNP 4 × 180K microarrays (Agilent Technologies) with 13 kb median aCGH probes spacing. Main results and the role of chance Altogether 116 CNVs were detected in CV and EM samples from 11 abortions. Fifty four (46.6%) variants were present in both tissues, while 29 (25%) were confined by CV and 33 (28.4%) by EM. Most of tissue-specific segmental aneuploidies in CV (90%) and EM (79%) arose de novo, whereas others were inherited from parents. It is important that 5 maternally inherited microduplications in some clinically significant regions like 1p21.1 (103 kb in size), 2p21 (3.56 kb), 3p22.3 (128 kb), 7q36.3 (42.7 kb), and Xq28 (182 kb) were confined by EM, whereas two at 4p16.3 (22.3 kb) and 19q13.43 (2.2 kb) by CV. No cases of tissue-specific maternally inherited microdeletions or paternal CNVs were observed in our study. One can suggest that confined placental mosaicism for inherited maternal microduplications arisen by trisomy rescue mechanism with loss of additional maternal chromosome copy in CV or EM after its divergence around the time of blastocyst implantation. This hypothesis is confirmed by comparative SNP-haplotype analysis of DNA samples from both CV and EM tissues as well as parental samples in the subchromosomal regions of microduplications and adjusted loci. Limitations, reasons for caution Control group of induced (social) abortions of the same developmental terms are required to estimate the prevalence and distribution of mosaic segmental aneuploidies in embryonic and extraembrionic tissues during normal human embryo development. Wider implications of the findings Tracing of tissue-specific mosaic segmental aneuploidies in first-trimester miscarriages allows to estimate the level of karyotype instability and self-correction during human embryo development. This study was supported by the Russian Science Foundation, № 21-65-00017, https://rscf.ru/project/21-65-00017/ Trial registration number not applicable

TAaCGH Suite for Detecting Cancer—Specific Copy Number Changes Using Topological Signatures

Copy number changes play an important role in the development of cancer and are commonly associated with changes in gene expression. Persistence curves, such as Betti curves, have been used to detect copy number changes; however, it is known these curves are unstable with respect to small perturbations in the data. We address the stability of lifespan and Betti curves by providing bounds on the distance between persistence curves of Vietoris–Rips filtrations built on data and slightly perturbed data in terms of the bottleneck distance. Next, we perform simulations to compare the predictive ability of Betti curves, lifespan curves (conditionally stable) and stable persistent landscapes to detect copy number aberrations. We use these methods to identify significant chromosome regions associated with the four major molecular subtypes of breast cancer: Luminal A, Luminal B, Basal and HER2 positive. Identified segments are then used as predictor variables to build machine learning models which classify patients as one of the four subtypes. We find that no single persistence curve outperforms the others and instead suggest a complementary approach using a suite of persistence curves. In this study, we identified new cytobands associated with three of the subtypes: 1q21.1-q25.2, 2p23.2-p16.3, 23q26.2-q28 with the Basal subtype, 8p22-p11.1 with Luminal B and 2q12.1-q21.1 and 5p14.3-p12 with Luminal A. These segments are validated by the TCGA BRCA cohort dataset except for those found for Luminal A.

EP400: Utility of genome sequencing in CNV identification in an immune disorders cohort

Chromosomal microarray (CMA) enables the detection of copy number changes within exon or gene-level resolution depending on probe density and gene coverage. Genome sequencing (GS) can circumvent these resolution issues through detection of smaller copy number changes enabled by uniformity of coverage that is not possible by exome sequencing (ES). Copy number variants (CNVs) can add to the diagnostic yield of inborn errors of immunity (IEI); however, the role of genome sequencing in identifying CNVs in IEI is not well understood.

Epigenotype, Genotype, and Phenotype Analysis of Taiwanese Patients with Silver-Russell Syndrome.

Background: Silver–Russell syndrome (SRS) is a clinically and genetically heterogeneous disorder characterized by severe intrauterine growth retardation, poor postnatal growth, characteristic facial features, and body asymmetry. Hypomethylation of the imprinted genes of the chromosome 11p15.5 imprinting gene cluster and maternal uniparental disomy of chromosome 7 (mUPD7) are the major epigenetic disturbances. The aim of this study was to characterize the epigenotype, genotype, and phenotype of these patients in Taiwan. Methods: Two hundred and six subjects with clinically suspected SRS were referred for diagnostic testing, which was performed by profiling the methylation of H19-associated imprinting center (IC) 1 and the imprinted PEG1/MEST region using methylation-specific multiplex ligation-dependent probe amplification and high-resolution melting analysis with a methylation-specific polymerase chain reaction assay. We also applied a whole genome strategy to detect copy number changes and loss of heterozygosity. Clinical manifestations were recorded and analyzed according to the SRS scoring system proposed by Bartholdi et al. Results: Among the 206 referred subjects, 100 were classified as having a clinical diagnosis of SRS (score ≥ 8, maximum = 15) and 106 had an SRS score ≤ 7. Molecular lesions were detected in 45% (45/100) of the subjects with a clinical diagnosis of SRS, compared to 5% (5/106) of those with an SRS score ≤ 7. Thirty-seven subjects had IC1 hypomethylation, ten subjects had mUPD7, and three subjects had microdeletions. Several clinical features were found to be statistically different (p < 0.05) between the “IC1 hypomethylation” and “mUPD7” groups, including relative macrocephaly at birth (89% vs. 50%), triangular shaped face (89% vs. 50%), clinodactyly of the fifth finger (68% vs. 20%), and SRS score (11.4 ± 2.2 vs. 8.3 ± 2.5). Conclusions: The SRS score was positively correlated with the molecular diagnosis rate (p < 0.001). The SRS subjects with mUPD7 seemed to have fewer typical features and lower SRS scores than those with IC1 hypomethylation. Careful clinical observation and timely molecular confirmation are important to allow for an early diagnosis and multidisciplinary management of these patients.

Improving high-resolution copy number variation analysis from next generation sequencing using unique molecular identifiers

BackgroundRecently, copy number variations (CNV) impacting genes involved in oncogenic pathways have attracted an increasing attention to manage disease susceptibility. CNV is one of the most important somatic aberrations in the genome of tumor cells. Oncogene activation and tumor suppressor gene inactivation are often attributed to copy number gain/amplification or deletion, respectively, in many cancer types and stages. Recent advances in next generation sequencing protocols allow for the addition of unique molecular identifiers (UMI) to each read. Each targeted DNA fragment is labeled with a unique random nucleotide sequence added to sequencing primers. UMI are especially useful for CNV detection by making each DNA molecule in a population of reads distinct.ResultsHere, we present molecular Copy Number Alteration (mCNA), a new methodology allowing the detection of copy number changes using UMI. The algorithm is composed of four main steps: the construction of UMI count matrices, the use of control samples to construct a pseudo-reference, the computation of log-ratios, the segmentation and finally the statistical inference of abnormal segmented breaks. We demonstrate the success of mCNA on a dataset of patients suffering from Diffuse Large B-cell Lymphoma and we highlight that mCNA results have a strong correlation with comparative genomic hybridization.ConclusionWe provide mCNA, a new approach for CNV detection, freely available at https://gitlab.com/pierrejulien.viailly/mcna/ under MIT license. mCNA can significantly improve detection accuracy of CNV changes by using UMI.

FrenchFISH: Poisson Models for Quantifying DNA Copy Number From Fluorescence In Situ Hybridization of Tissue Sections.

PURPOSEChromosomal aberration and DNA copy number change are robust hallmarks of cancer. The gold standard for detecting copy number changes in tumor cells is fluorescence in situ hybridization (FISH) using locus-specific probes that are imaged as fluorescent spots. However, spot counting often does not perform well on solid tumor tissue sections due to partially represented or overlapping nuclei.MATERIALS AND METHODSTo overcome these challenges, we have developed a computational approach called FrenchFISH, which comprises a nuclear volume correction method coupled with two types of Poisson models: either a Poisson model for improved manual spot counting without the need for control probes or a homogeneous Poisson point process model for automated spot counting.RESULTSWe benchmarked the performance of FrenchFISH against previous approaches using a controlled simulation scenario and tested it experimentally in 12 ovarian carcinoma FFPE-tissue sections for copy number alterations at three loci (c-Myc, hTERC, and SE7). FrenchFISH outperformed standard spot counting with 74% of the automated counts having < 1 copy number difference from the manual counts and 17% having < 2 copy number differences, while taking less than one third of the time of manual counting.CONCLUSIONFrenchFISH is a general approach that can be used to enhance clinical diagnosis on sections of any tissue by both speeding up and improving the accuracy of spot count estimates.

Abstract 4319: Clinical utility of multiplex digital PCR to detect androgen receptor amplification in cell-free DNA for prognosis of metastatic castration-resistant prostate cancer

Abstract Background: Androgen receptor (AR) amplification is a common genomic event in advanced prostate cancer, in particular, the metastatic castration-resistant prostate cancer (mCRPC) and is associated with poor treatment response and short overall survival (OS). Recent studies also show more frequent amplification at AR enhancer region in the mCRPC patients. The aim of this study is to evaluate clinical utility of multiplex digital PCR assay to detect amplification at AR locus in cell-free DNA (cfDNA) for prognostication of mCRPC. Methods: Plasma samples were collected from 108 patients with mCRPC before stage-specific treatment. The target regions were selected based on our previous sequencing data showing frequent amplification in mCRPC patients at AR loci, including AR enhancer, AR (AR exon 1 and exon 8) and OPHN1 (downstream of AR). Multiplex digital PCR assays to detect four targets were developed by adjusting the concentrations of primers and probes. The Kaplan-Meier (KM) estimate was used for OS analysis. Results: We first examined existing databases to determine relative stable genomic regions in prostate cancer. This analysis showed most stable regions in three gene loci including C2orf16 at 2p23.2, FAM111B at 11q12.1, and GRIA3 at Xq25, which were then used as reference controls for copy number normalization. We then designed two multiplex digital PCR assays to quantify copy number of selected targets. To separate two different targets with same fluorescence, we adjusted ratio of FAM-labeled probes with 1: 0.4 and HEX-labeled probes with 1:0.4. The ratio of FAM to HEX probes was 1:1.5 in final assays. The combination of four different targets in one reaction gave 9 possible clusters in the 2D amplitude space. We defined the amplification as the normalized ratio ≥ 1.8 between target and reference loci. By applying this cutoff in 108 mCRPC samples, we detected the amplification of AR-enhancer, AR and OPHN1 in 38, 34, and 25 samples, respectively. KM analysis showed the significant association of amplification in AR-enhancer (p=0.0053, HR=2.16[1.41-6.53]), AR (p=0.04, HR=1.74[1.04-4.03]) and OPHN1 (p=0.031, HR=1.91[1.07-5.53]) with OS. This result was consistent with whole genome sequencing data in the same group of patients. Conclusions: We established a highly sensitive multiplex digital PCR assay to detect copy number changes of AR, AR enhancer and OPHN1 in plasma cfDNA and demonstrated its potential clinical use as non-invasive testing tool for mCRPC prognosis. The easy-to-use and low-cost multiplex digital PCR assay covers multiple gene loci, which can aid in improving the sensitivity of detecting amplification at AR locus in the highly heterogeneous mCRPC patients. Citation Format: Meijun Du, Chiang-Ching Huang, Winston Tan, Manish Kohli, Liang Wang. Clinical utility of multiplex digital PCR to detect androgen receptor amplification in cell-free DNA for prognosis of metastatic castration-resistant prostate cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4319.

Whole genome SNP arrays for best practice for detection of diagnostic, prognostic and therapy related copy number changes and copy neutral-loss of heterozygosity across solid tumors and hematologic malignancies.

e15575 Background: High resolution single nucleotide polymorphism (SNP) chromosomal microarrays (CMA) detect copy number changes and copy neutral-loss of heterozygosity (CN-LOH) across the entire genome, currently providing the best assessment for these types of genomic variants. Chromosomal microarrays are first tier tests utilized in the postnatal detection of microdeletions, microduplications and uniparental disomy/regions of homozygosity in constitutional disorders involving congenital abnormalities, developmental delay and intellectual disability. Methods: In the oncology setting, aberrations detected may be diagnostic, prognostic, and therapeutic. Because CMA assesses the entire genome and can readily detect aberrations as small as a single exon to as large as a whole chromosome, this is an important clinical tool to bridge the gap between low resolution of metaphase chromosome analysis and PCR-based short read sequencing-based assays. Results: No single genomic technique (metaphase chromosome analysis, FISH, CMA or Next Generation Sequencing, including large targeted gene panels) has the ability to detect all relevant information. Therefore, CMA should be considered an important clinical tool for solid and liquid tumors. Across a wide variety of solid tumors, whole genome assessment (including oncogene amplification, tumor suppressor loss, and copy number burden) leads not only to possible therapy targets but also to opportunities for participation in active clinical trials. Recently, the Cancer Genomics Consortium has published evidenced-based reviews on the clinical utility of CMA for copy number and CN-LOH assessment in a variety of hematologic malignancies, and similar papers in solid tumors are in review. Recognizing the growing evidence for CMA, the American Medical Association (AMA) CPT editorial board recently created a new Tier 1 test for cytogenomic arrays in neoplasia, and Centers for Medicare and Medicaid Services (CMS) approved crosswalking the price of the new code to the well-established constitutional cytogenomic array CPT code. Conclusions: For this presentation, examples of diagnostic, prognostic, and therapeutic utility and inclusion in clinical trials across many hematologic and solid tumor neoplasms will be presented to demonstrate the efficacy, cost effectiveness and sensitivity of whole genome assessment of copy number and copy neutral loss of heterozygosity

Combining copy number, methylation markers, and mutations as a panel for endometrial cancer detection via intravaginal tampon collection

ObjectiveWe aimed to assess whether endometrial cancer (EC) can be detected in shed DNA collected with vaginal tampon by analyzing copy number, methylation markers, and mutations. MethodsTampons were collected prior to hysterectomy from 38 EC patients and 28 women with benign indications. Extracted tampon DNA underwent the following: 1) low-coverage whole genome sequencing (LC-WGS) to assess copy number, 2) pyrosequencing to measure percent promotor methylation of HOXA9, RASSF1, and CDH13 and 3) next generation sequencing (NGS) to identify mutations in 19 genes associated with EC identified through The Cancer Genome Atlas. Sensitivity and specificity for each test and test combinations were calculated. ResultsMethylation analysis yielded the highest specificities but lowest sensitivities (37–40% sensitivity; 100% specificity for HOXA9, RASSF1 and HTR1B) while mutation analysis had improved sensitivity (50% sensitivity; 83% specificity). Only one “false positive” result for copy number variants was identified among women with benign surgical indications, which was based on detection of copy number changes, and associated with a leiomyosarcoma that was only recognized at hysterectomy. Considering any of the 3 biomarker classes as a positive, resulted in a sensitivity of 92% and specificity of 86%. Mutation analysis did not add sensitivity to the combination of analysis of copy number and methylation. ConclusionsThis study demonstrates a proof-of-principle for non-invasive yet precise detection of endometrial cancer. We propose that with improved biomarker testing, it may be possible to develop a clinically useful test for detecting EC.

EP1.01-13 A Phase 2 Trial Assessing Osimertinib Activity Against Leptomeningeal Carcinomatosis in EGFR-Mutant Lung Cancer

Leptomeningeal carcinomatosis (LMC) occurs in 10 % of EGFR-mutant lung adenocarcinoma (LA). Retrospective studies have suggeted a clinical benefit of osimertinib in treating LMC in patients with EGFR-mutant LA. We conducted a phase 2 prospective trial to demonstrate the clinical efficacy, activity, and LMC-specific mechanisms of resitance to osimertinib in EGFR-mutant LA patients. We performed gadalidium-enhanced brain MRIs at the time of enrollment, followed by scheduled brain imaging once every six weeks. Clinical neurological exams were performed every four weeks. Adverse Events (AEs) were assessed by NCI-CTCAE Ver. 4. Cerebral spinal fluid (CSF) and plasma was obtained on day 1 and 21 for all patients. The CSF osimertinib penetration rate was measured by liquid-chromatography mass spectrometry (LC-MSMS) and compared to plasma osimertinib levels. Targeted droplet digital PCR (ddPCR) was used to detect copy number changes of Met and the EGFR C797S mutation in patients CSF-DNA and plasma cell free (cf) DNA. We enrolled six pre EGFR-TKI treated EGFR mutant LA with LMC. We observed a LMC-specific progression free survival of 3.7 months and overall survival of 6.2 months or longer with osimertinib. Four and three of six patients showed neurological and radiological responses, respectively. No patients had any AEs greater than grade 3 and all patients continued osimertinib beyond PD. The osimertinib CSF penetration rate was 1.2±0.5%. Met copy number was normal in plasma, but increased in the CSF of 2/6 patients prior to progression. Met copy number was confirmed in 1/6 patients at the time of progression. An aquired EGFR C797S mutation was observed in 1/6 patients prior to progression.View Large Image Figure ViewerDownload Hi-res image Download (PPT) Osimertinib 80 mg is efficacious in the treatment of LMC in EGFR mutated LA. CSF-specific MET copy number gain and EGFR C797S mutations arise prior to progression in EGFR-mutant LA patients treated with osimeritinib.

Abstract P3-06-03: Copy number analysis identifies ESR1 and MDM4 as drivers of progression in invasive lobular breast carcinoma

Abstract Background: Invasive lobular carcinoma (ILC) is the second most common histological subtype of breast cancer after invasive ductal carcinoma (IDC). While specific clinical and pathological features differ between ILC and IDC, both histologies are treated the same, due to a lack of knowledge of targetable pathways underlying the observed differences. To identify potential genetic drivers of ILC progression, we set out to identify genes with copy number (CN) alterations, comparing tumors with good outcome to those with poor outcome. Method: We designed probes for a total of 67 genes known to be frequently altered in breast cancer and used sensitive nanoString technology to comprehensively investigate CN alterations of these genes in 70 well-curated primary ILCs. ILC cell lines MDA-MB-134-VI, SUM44PE, and BCK4 were used for functional studies including proliferation, apoptosis, colony formation, and analysis of gene expression. Results: Our studies reveal that ESR1 is frequently amplified in primary ILC (14% gains and 10% amplification), and that tumors with amplified ESR1 are more likely to recur compared to those with normal CN. Our analysis also identified a subset of ILCs with HER2 amplification (19%) despite a negative clinical IHC score, and these tumors expressed high HER2 mRNA, protein, and demonstrated enrichment of a molecular HER2 signature. The other most frequently amplified genes included CCND1 (33%), MDM4 (17%), and MYC (17%), and most frequently lost genes were NCOR2 (7%), FGFR4 (6%) and TP53 (6%). MDM4, a negative regulator of p53, has previously been reported to play a role in breast cancer, though little is known about its role in ILC. We demonstrate that decreasing MDM4 levels in p53 wild type ILC cell lines results in increased apoptosis, decreased proliferation associated with cell cycle arrest, and activation of p53 target genes. Intriguingly, a similar induction of G0/G1 cell cycle arrest and increase in apoptosis was observed in p53 mutant ILC cells after MDM4 downregulation, suggesting a p53-independent function of MDM4. Conclusion: Sensitive detection of CN changes identified amplifications of ESR1 and MDM4 as potential drivers of ILC. Functional studies demonstrate that MDM4 has both p53 dependent and independent functions that warrant further study. Citation Format: Atkinson JM, Cao L, Basudan A, Sikora MJ, Bahreini A, Tasdemir N, Jankowitz RC, McAuliffe PF, Dabbs D, Haupt S, Haupt Y, Peter Lucas PC, Lee AV, Oesterreich S. Copy number analysis identifies ESR1 and MDM4 as drivers of progression in invasive lobular breast carcinoma [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-06-03.

Chromosome 21 Gain Is Dispensable for Transient Myeloproliferative Disorder (TMD) Development

Transient myeloproliferative disorder (TMD) is a hematopoietic disease, characterized by a clonal proliferation of immature megakaryoblasts in the neonatal period occurring in approximately 10% of newborns with Down syndrome (DS). Rarely, TMD occurs in non-DS newborns but then it is associated with somatic trisomy 21 (tri21). Tri21 together with in-utero gained mutations in the GATA1 gene encoding a myeloid transcription factor are thus considered essential in TMD.Recently, we have identified a TMD with a typical manifestation and course in a newborn without DS/somatic tri21, which admits that tri21 is dispensable for TMD development. To elucidate the alternative TMD pathogenesis, we performed comprehensive genomic/transcriptomic profiling of this TMD case. We utilized high-density SNP array and whole exome and transcriptome sequencing (WES/RNAseq) to detect copy number changes, mutations and fusion genes. We did not find any aberrations on chromosome 21 and any fusion genes. Two focal intronic losses, likely representing benign germline variants, were found on chromosome X. In addition to 6 missense mutations affecting genes without established roles in hematopoietic disorders, we found in-frame deletions in the GATA1 and JAK1 genes. Both mutations are novel. The GATA1 D65_C228del mutation is predicted to result in an internally truncated protein - GATA1aber. Unlike GATA1s (resulting from GATA1 mutations in DS-TMD) which lacks the transactivation domain (TAD) but retains both Zinc fingers (ZF), GATA1aber lacks part of TAD and the N-terminal ZF. Nevertheless, we hypothesize that GATA1aber substitutes the pathogenetic role of GATA1s. The JAK1 gene encodes a non-receptor tyrosine-kinase engaged in the JAK/STAT signaling pathway. The identified mutation results in the loss of phenylalanine 636 (F636del), which is located in the pseudokinase domain and belongs to a conserved amino acid triad (F636-F575-V658) that is believed to mediate a structural switch controlling the JAK1 catalytic activity (Toms, Nat Struct Mol Biol, 2013). JAK1 mutations are implicated in various hematological malignancies including acute megakaryocytic leukemia, and we hypothesize that JAK1 F636del co-operates with GATA1aber on TMD pathogenesis via deregulation of cytokine/growth factor signaling.We cloned the coding sequences of GATA1aber and JAK1 F636del and transfected them into a model cell line in which we confirmed the expression of both in-silico predicted proteins. Their subcellular trafficking was analogous to that of their wild type counterparts; GATA1aber was found in the nucleus and JAK1 F636del in both the nucleus and cytoplasm. Next, we assessed the kinase activity of JAK1 F636del. To distinguish auto- from trans-phosphorylation, we utilized the JAK1 F636del construct harboring an inactivating mutation of an ATP-binding site (K908G). The JAK1 F636del (but not JAK1 F636del + K908G) was autophosphorylated on Y1034/Y1035 and induced STATs phosphorylation both under steady-state conditions and following non-specific stimulation with PMA. However, at all studied time points all phosphorylation levels were lower compared to wild-type JAK1. Moreover, unlike constitutively active JAK1 V658I, JAK1 F636del did not confer IL3-independent growth to the murine B-cell progenitor cell line BAF3. Interestingly, the transforming potential of double-mutated JAK1 (JAK1 V658I + F636del) was enforced compared to JAK1 V658I. These data show that F636del does not lead to constitutive activation, but in the same time it is not functionally neutral. As the impact of F636del on JAK1 function may vary depending on upstream signaling, we are currently assessing JAK1 F636 kinase activity/transforming potential in BAF3 cells stably expressing the IL6 receptor, which (unlike the IL3 receptor) directly activates JAK1 upon ligand binding. In the future, we plan to study the impact of JAK1 F636del on GATA1s induced deregulation of erythroid/megakaryocytic lineage development and to demonstrate “GATA1s-like” function of GATA1aber.To conclude, we identified two novel mutations affecting GATA1 and JAK1 as likely drivers in an alternative tri21-independent TMD pathogenesis. As the pathogenetic role of tri21 has been poorly understood so far, we believe that by clarifying an alternative mechanism of TMD development, we could improve our understanding of this intriguing disease in general.Support: GAUK 86218 DisclosuresNo relevant conflicts of interest to declare.

Ultrasound findings provide clues to investigate founder mutations expressed as runs of homozygosity in chromosomal microarray studies.

Chromosomal microarray analysis is effectively applied prenatally to detect copy number changes. Single nucleotide polymorphism (SNP) probes included in the microarray platform can detect regions of excessive homozygosity and identical-by-descent genomic stretches. The utility of the latter as part of prenatal diagnosis is not well established. Recessive founder mutations are well recognized within distinct ethnic groups. Combining these data with prenatal sonography provides accurate focused molecular diagnoses quickly. We aimed to evaluate the application of this approach in expectant families presenting to our unit. Three unrelated gravidae presenting with specific fetal sonographic findings: (1) ventriculomegaly with encephalocele; (2) severe polyhydramnion; and (3) enlarged echogenic kidneys, underwent amniocentesis for chromosomal microarray analysis, and genome-wide human SNP array was used to analyze DNA from amniocytes. The Genomic Oligoarray and SNP array evaluation tool v3.0© was used to detect recessive loci associated with the reported clinical findings. Candidate genes were further interrogated using the Israeli National Genetic Database (INGD) and specifically searching and identifying a corresponding founder mutation within the defined ethnic group. Three fetuses from 3 distinct nuclear families in which the parents shared a similar ethnicity (either Ashkenazi or Bukharan Jews) albeit no reported consanguinity were assessed. We found no copy number changes; however, by evaluating regions of homozygosity, we were able to reveal relevant candidate gene for the specific phenotype for each fetus. Using the INGD led to targeted testing of a specific homozygous fetal mutation for which parents were found to be carriers. In the fetus with ventriculomegaly with encephalocele c.1167dupA mutation in the FKTN gene, in the fetus with severe polyhydramnion c.167ins6[TTTCCC] mutation in the BSND gene, and in the fetus with enlarged echogenic kidneys, c.3761_3762delCCinsG in the PKHD1 gene were identified. A tripartite approach integrating sonographic pathology with regions of excessive homozygosity data and INGD-based founder mutation repository yields a comprehensive streamlined approach to provide accurate genetic diagnosis and counselling within the time constraints of an ongoing pregnancy.

Evaluating melanocytic lesions with single nucleotide polymorphism (SNP) chromosomal microarray

Histopathology is the gold standard for diagnosing melanocytic lesions; however, distinguishing benign versus malignant is not always clear histologically. Single nucleotide polymorphism (SNP) microarray analysis may help in making a definitive diagnosis. Here, we share our experience with the Oncoscan FFPE Assay and demonstrate its diagnostic utility in the context of ambiguous melanocytic lesions.Eleven archival melanocytic lesions, including three benign nevi, four melanomas, three BAP1-deficient Spitzoid nevi and one nevoid melanoma were selected for validation. SNP-array was performed according to the manufacturer's protocol, using the recommended 80ng of DNA; however, as little as 15ng was used if the extraction yield was lower. Concordance was assessed with H&E and various combinations of BAP1 and p16 immunohistochemical stains (IHC) and external reference laboratory chromosomal microarray results. After validation, the SNP array was utilized to make definitive diagnoses in four challenging cases.Oncoscan SNP array findings were in concordance with H&E, IHC, and reference laboratory chromosomal microarray testing.The SNP-based microarray can accurately detect copy number changes and aid in making a more definitive diagnosis of challenging melanocytic lesions. This can be accomplished using significantly less DNA than is required by other microarray technologies.

OP22.08: Integrating ultrasound findings with chromosomal microarray stretches of homozygosity and principles in founder populations

Chromosomal microarray (CMA) analysis is effectively applied prenatally to detect copy number changes. SNP probes included on the microarray platform can detect regions of excessive homozygosity (ROH) and identical-by-descent genomic stretches. The utility of the latter in prenatal diagnosis is not well established. Recessive founder mutations have been identified within distinct ethnic groups. Combining these data with prenatal sonography provides accurate molecular diagnoses quickly. Three gravidae presenting with specific fetal sonographic findings: 1) ventriculomegaly with encephalocele; 2) severe polyhydramnion, and 3) enlarged echogenic kidneys, underwent amniocentesis for CMA, and Genome-Wide Human SNP array was used to analyse DNA from amniocytes. The Genomic Oligoarray and SNP array evaluation tool v3.0 was used to detect recessive loci associated with the reported clinical findings. Candidate regions were further interrogated using the National Genetic Database. Three fetuses from three distinct nuclear families in which the parents shared a similar ethnicity (either Ashkenazi or Bukharan Jews) but no reported consanguinity, were assessed. No copy number changes were observed, however evaluation of regions of homozygosity revealed a relevant candidate gene for the specific phenotype for each fetus. Using the National Genetic Database a specific mutation was examined in both parents (c.1167dupA mutation in the FKTN gene, c.167ins6[TTTCCC] mutation in the BSND gene and c.3761_3762delCCinsG in the PKHD1 gene, respectively). Both parents were found to be carriers and the fetuses homozygotes to the mutation. For the first time, specific sonographic pathology, data from ROH extracted from CMA results, and information regarding common founder mutations in distinct ethnic subgroups were combined to create a comprehensive streamlined approach to provide effective genetic diagnosis and counselling within the time constraints of ongoing pregnancy.

Development of a Chromosomal Microarray Test for the Detection of Abnormalities in Formalin-Fixed, Paraffin-Embedded Products of Conception Specimens

Testing the products of conception (POCs) provides information about the cause of fetal loss and helps determine the recurrence risk of future losses and chromosome abnormalities in subsequent pregnancies. Historically, the Mayo Clinic Cytogenetics Laboratory performed targeted fluorescent in situ hybridization (FISH) testing to identify aneuploidy of only certain chromosomes in formalin-fixed, paraffin-embedded (FFPE) POC samples. Chromosomal microarray studies using the Affymetrix OncoScan FFPE Assay can detect copy number changes across the genome. We validated the utility of the OncoScan assay using 25 archival FFPE POC specimens with previous FISH results (five normal, 12 trisomy, six triploidy, two monosomy). Of the five normal samples, four had no clinically relevant findings, and one sample was found to have trisomy 9, which is not detectable by the FISH test. For the 20 samples with abnormal FISH results, the OncoScan assay identified all reported abnormalities along with additional findings. A sample with trisomy 22 was also found to have trisomy 7. Another sample reported as triploidy was found to have four copies of chromosome 16. In conclusion, we verified the performance characteristics of OncoScan on FFPE POC specimens and found it acceptable for clinical use. Additional information was identified in 3 of 25 cases (12%) that would explain the pregnancy loss or provide recurrence risk for the family.

Shallow Whole Genome Sequencing can Detect Copy Number Changes in FFPE Material in the Progression of Barrett's Esophagus

Shallow Whole Genome Sequencing can Detect Copy Number Changes in FFPE Material in the Progression of Barrett's Esophagus

Embryonal Origin of MTSCC of Kidney May Explain its Morphological Heterogeneity: Diagnostic Impact of Genetic Analysis

Previous genetic and morphologic characterisation of mucinous tubular and spindle cell carcinoma (MTSCC) have yielded controversial results. The aim of this study was to explain the phenotypic heterogeneity of MTSCC diagnosed by genetic means. We analyzed 7 MTSCC by array CGH and microsatellite allelotyping and by histology for morphological variation. We worked-up two entire kidneys with MTSCC to find microscopic alterations. We confirmed the diagnosis of MTSCC by detecting copy number changes at chromosomes 1, 4, 6, 8, 13, 14, 15, 18 and 22. We detected 13 small, microscopic precursor lesions in the two kidneys and found similar histological structures in precursor lesions and MTSCC. MTSCC develops from embryonal rest-like lesions of impaired differentiation which may explain its morphological variations. Until diagnosis of a "malignant" MTSCC" is not confirmed by genetic means, it should not be called carcinoma.