A preliminary study of the relationship between breast cancer metastasis and loss of heterozygosity by using exome sequencing.
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ABSTRACT:
SUBMITTER: Li H
PROVIDER: S-EPMC5381542 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:MotivationThe ability to detect copy-number variation (CNV) and loss of heterozygosity (LOH) from exome sequencing data extends the utility of this powerful approach that has mainly been used for point or small insertion/deletion detection.ResultsWe present ExomeCNV, a statistical method to detect CNV and LOH using depth-of-coverage and B-allele frequencies, from mapped short sequence reads, and we assess both the method's power and the effects of confounding variables. We apply our method to a cancer exome resequencing dataset. As expected, accuracy and resolution are dependent on depth-of-coverage and capture probe design.AvailabilityCRAN package 'ExomeCNV'.Contactfsathira@fas.harvard.edu; snelson@ucla.eduSupplementary informationSupplementary data are available at Bioinformatics online.
| S-EPMC3179661 | biostudies-literature
Project description:Using whole-exome sequencing (WES) for the detection of chromosomal aberrations from tumor samples has become increasingly popular, as it is cost-effective and time efficient. However, factors which present in WES tumor samples, including diversity in exon size, batch effect and tumor impurity, can complicate the identification of somatic mutation in each region of the exon. To address these issues, the authors of the present study have developed a novel method, PECNV, for the detection of genomic copy number variants and loss of heterozygosity in WES datasets. PECNV combines normalized logarithm ratio of read counts (Log Ratio) and B allele frequency (BAF), and then employs expectation maximization (EM) algorithm to estimate parameters involved in the models. A comprehensive assessment of PECNV of PECNV was performed by analyzing simulated datasets contaminated with different normal cell proportion and eight real primary triple-negative breast cancer samples. PECNV demonstrated superior results compared with ExomeCNV and EXCAVATOR for the detection of genomic aberrations in WES data.
| S-EPMC6126229 | biostudies-literature
Project description:Objective Conflicting results regarding SOX17 genes and the risk of intracranial aneurysms (IA) exist in the Korean population, although significant positive correlations were noted in genome-wide association studies in European and Japanese populations. Therefore, we aimed to investigate an association between SOX17 gene variants and IA using exome sequencing data. Methods This study included 26 age-gender matched IA patients and 26 control subjects. The SOX17 gene variants identified from whole-exome sequencing data were examined. Genetic associations to estimate odds ratio (OR) and 95% confidence interval (CI) were performed using the software EPACTS. Results The mean age of the IA and control groups were 51.0±9.3 years and 49.4±14.3 years, respectively (p=0.623). Seven variants of SOX17, including six single nucleotide polymorphisms and one insertion and deletion, were observed. Among these variants, rs12544958 (A>G) showed the most association with IA, but the association was not statistically significant (OR, 1.97; 95% CI, 0.81–4.74; p=0.125). Minor allele frequencies of the IA patients and controls were 0.788 and 0.653, respectively. None of the remaining variants were significantly associated with IA formation. Conclusion No significant association between SOX17 gene variants and IA were noted in the Korean population. A large-scale exome sequencing study is necessary to investigate any Korean-specific genetic susceptibility to IA.
| S-EPMC7477156 | biostudies-literature
Project description:Metastasis is a major cause of cancer-related mortality, and it is essential to understand how metastasis occurs in order to overcome it. One relevant question is the origin of a metastatic tumor cell population. Although the hypothesis of a single-cell origin for metastasis from a primary tumor has long been prevalent, several recent studies using mouse models have supported a multicellular origin of metastasis. Human bulk whole-exome sequencing (WES) studies also have demonstrated a multiple "clonal" origin of metastasis, with different mutational compositions. Specifically, there has not yet been strong research to determine how many founder cells colonize a metastatic tumor. To address this question, under the metastatic model of "single bottleneck followed by rapid growth," we developed a method to quantify the "founder cell population size" in a metastasis using paired WES data from primary and metachronous metastatic tumors. Simulation studies demonstrated the proposed method gives unbiased results with sufficient accuracy in the range of realistic settings. Applying the proposed method to real WES data from four colorectal cancer patients, all samples supported a multicellular origin of metastasis and the founder size was quantified, ranging from 3 to 17 cells. Such a wide-range of founder sizes estimated by the proposed method suggests that there are large variations in genetic similarity between primary and metastatic tumors in the same subjects, which may explain the observed (dis)similarity of drug responses between tumors.
| S-EPMC7079087 | biostudies-literature
Project description:The genomic landscape of breast cancer (BC) is complex. The purpose of this study was to decipher the mutational profiles of Taiwanese patients with BC using next-generation sequencing. We performed whole-exome sequencing on DNA from 24 tumor tissue specimens from BC patients. Sanger sequencing was used to validate the identified variants. Sanger sequencing was also performed on paired adjacent nontumor tissues. After genotype calling and algorithmic annotations, we identified 49 deleterious variants in canonical cancer-related genes in our BC cohort. The most frequently mutated genes were PIK3CA (16.67%), FKBP9 (12.5%), TP53 (12.5%), ATM (8.33%), CHEK2 (8.33%), FOXO3 (8.33%), NTRK1 (8.33%), and NUTM2B (8.33%). Seven mutated variants (ATR p.V1581fs, CSF1R p.R579Q, GATA3 p.T356delinsTMKS, LRP5 p.W389*, MAP3K1 p.T918fs, MET p.K1161fs, and MTR p.P1178S) were novel variants that are not present in any gene mutation database. After grouping the samples according to molecular subtype, we found that the cell cycle, MAPK, and chemokine signaling pathways in the luminal A subtype of BC; the focal adhesion, axon guidance, and endocytosis pathways in the luminal B subtype; and amyotrophic lateral sclerosis in the basal-like subtype were exclusively altered. Survival curve analysis showed that the presence of the MAPK signaling pathway and endocytosis mutations were correlated with a poor prognosis. These survival data were consistent with cBioPortal analyses of 2,051 BC cases. We discovered novel mutations in patients with BC. These results have implications for developing strategic, adjuvant, and gene-targeted therapies.
| S-EPMC7851574 | biostudies-literature
Project description:Chromosome arm deletions are frequently observed in human cancers. Such large-scale aberrations may trigger phenotypes distinct from those that arise by loss of single genes. Using TALEN-based genomic engineering, we generated cell models with targeted 8p loss-of-heterozygosity (LOH) that mimics an 8p deletion commonly found in breast cancer patients. 8p LOH triggered up-regulation of the mevalonate pathway. The alterations in lipid metabolism led to increased metastatic potential and drug resistance of 8p-deleted cells that are in agreement with poorer survival rates of breast cancer patients harbouting 8p LOH. Our findings also suggest novel therapeutic strategies for treatment of 8p LOH tumors. RNASeq Analysis of two Wt 8p Cell clones vs two 8p LOH cell clones generated via TALEN Approach
2015-05-21 | E-GEOD-68042 | biostudies-arrayexpress
Project description:BackgroundLoss of heterozygosity (LOH) is an important marker for one of the 'two-hits' required for tumor suppressor gene inactivation. Traditional methods for mapping LOH regions require the comparison of both tumor and patient-matched normal DNA samples. However, for many archival samples, patient-matched normal DNA is not available leading to the under-utilization of this important resource in LOH studies. Here we describe a new method for LOH analysis that relies on the genome-wide comparison of heterozygosity of single nucleotide polymorphisms (SNPs) between cohorts of cases and un-matched healthy control samples. Regions of LOH are defined by consistent decreases in heterozygosity across a genetic region in the case cohort compared to the control cohort.MethodsDNA was collected from 20 Follicular Lymphoma (FL) tumor samples, 20 Diffuse Large B-cell Lymphoma (DLBCL) tumor samples, neoplastic B-cells of 10 B-cell Chronic Lymphocytic Leukemia (B-CLL) patients and Buccal cell samples matched to 4 of these B-CLL patients. The cohort heterozygosity comparison method was developed and validated using LOH derived in a small cohort of B-CLL by traditional comparisons of tumor and normal DNA samples, and compared to the only alternative method for LOH analysis without patient matched controls. LOH candidate regions were then generated for enlarged cohorts of B-CLL, FL and DLBCL samples using our cohort heterozygosity comparison method in order to evaluate potential LOH candidate regions in these non-Hodgkin's lymphoma tumor subtypes.ResultsUsing a small cohort of B-CLL samples with patient-matched normal DNA we have validated the utility of this method and shown that it displays more accuracy and sensitivity in detecting LOH candidate regions compared to the only alternative method, the Hidden Markov Model (HMM) method. Subsequently, using B-CLL, FL and DLBCL tumor samples we have utilised cohort heterozygosity comparisons to localise LOH candidate regions in these subtypes of non-Hodgkin's lymphoma. Detected LOH regions included both previously described regions of LOH as well as novel genomic candidate regions.ConclusionsWe have proven the efficacy of the use of cohort heterozygosity comparisons for genome-wide mapping of LOH and shown it to be in many ways superior to the HMM method. Additionally, the use of this method to analyse SNP microarray data from 3 common forms of non-Hodgkin's lymphoma yielded interesting tumor suppressor gene candidates, including the ETV3 gene that was highlighted in both B-CLL and FL.
| S-EPMC2885361 | biostudies-literature
Project description:Chromosome arm deletions are frequently observed in human cancers. Such large-scale aberrations may trigger phenotypes distinct from those that arise by loss of single genes. Using TALEN-based genomic engineering, we generated cell models with targeted 8p loss-of-heterozygosity (LOH) that mimics an 8p deletion commonly found in breast cancer patients. 8p LOH triggered up-regulation of the mevalonate pathway. The alterations in lipid metabolism led to increased metastatic potential and drug resistance of 8p-deleted cells that are in agreement with poorer survival rates of breast cancer patients harbouting 8p LOH. Our findings also suggest novel therapeutic strategies for treatment of 8p LOH tumors.
2015-05-21 | GSE68042 | GEO
Project description:Exome sequencing can identify genetic causes of idiopathic recurrent pregnancy loss (RPL).We identified compound heterozygous deleterious mutations affecting DYNC2H1 and ALOX15 in two out of four families with RPL. Both genes have a role in early development. Bioinformatics analysis of all genes with rare and putatively pathogenic mutations in miscarriages and couples showed enrichment in pathways relevant to pregnancy loss, including the complement and coagulation cascades pathways.Next generation sequencing (NGS) is increasingly being used to identify known and novel gene mutations in children with developmental delay and in fetuses with ultrasound-detected anomalies. In contrast, NGS is rarely used to study pregnancy loss. Chromosome microarray analysis detects putatively causative DNA copy number variants (CNVs) in ?2% of miscarriages and CNVs of unknown significance (predominantly parental in origin) in up to 40% of miscarriages. Therefore, a large number of miscarriages still have an unknown cause.Whole exome sequencing (WES) was performed using Illumina HiSeq 2000 platform on seven euploid miscarriages from four families with RPL. Golden Helix SVS v8.1.5 was used for data assessment and inheritance analysis for deleterious DNA variants predicted to severely disrupt protein-coding genes by introducing a frameshift, loss of the stop codon, gain of the stop codon, changes in splicing or the initial codon. Webgestalt (http://bioinfo.vanderbilt.edu/webgestalt/) was used for pathway and disease association enrichment analysis of a gene pool containing putatively pathogenic variants in miscarriages and couples in comparison to control gene pools.Compound heterozygous mutations in DYNC2H1 and ALOX15 were identified in miscarriages from two families with RPL. DYNC2H1 is involved in cilia biogenesis and has been associated with fetal lethality in humans. ALOX15 is expressed in placenta and its dysregulation has been associated with inflammation, placental, dysfunction, abnormal oxidative stress response and angiogenesis. The pool of putatively pathogenic single nucleotide variants (SNVs) and small insertions and deletions (indels) detected in the miscarriages showed enrichment in 'complement and coagulation cascades pathway', and 'ciliary motility disorders'. We conclude that CNVs, individual SNVs and pool of deleterious gene mutations identified by exome sequencing could contribute to RPL.The size of our sample cohort is small. The functional effect of candidate mutations should be evaluated to determine whether the mutations are causative.This is the first study to assess whether SNVs may contribute to the pathogenesis of miscarriage. Furthermore, our findings suggest that collective effect of mutations in relevant biological pathways could be implicated in RPL.The study was funded by Canadian Institutes of Health Research (grant MOP 106467) and Michael Smith Foundation of Health Research Career Scholar salary award to ERS.
| S-EPMC4847612 | biostudies-literature
Project description:In an effort to identify novel genes implicated in breast carcinogenesis, a genomewide scan for loss of heterozygosity (LOH) and copy number changes in paired-DNA samples extracted from normal and tumor tissue of frozen sections from women undergoing surgery for invasive breast cancer was conducted. The Affymetrix 10K SNP array was used to examine genomewide LOH of chromosomal regions. The number of LOH events, number of informative loci, percent heterozygosity, and percent fractional allelic loss (%FAL) were calculated. Although LOH events were detected in all samples, the proportion of LOH ranged from 0.1 to 57.2%. Elevated LOH events were detected in two samples, with a %FAL of 57.2 and 56.2. Chromosomal regions exceeding a threshold value for a P-value curve based on multiple-testing adjusted permutation methods were identified as significant regions of shared LOH across samples. Regions with significant LOH included 2p25.3; 2p21; 2p15 approximately p16.1, 2q23.3; and, 16q12.1. Chromosomal region 1q32.1 was identified as a region with significant copy number amplification. Regions of LOH and copy number changes identified from this analysis may provide insights into the underlying processes of and genes involved in breast carcinogenesis. The present study demonstrates a feasible methodological approach for the assessment of LOH and copy number changes.
| S-EPMC3972020 | biostudies-literature