Genetic sequencing technologies are evolving at a rapid pace with major implications for research and clinical practice. In this review, the authors provide an updated overview of next-generation ...sequencing (NGS) and emerging methodologies. NGS has tremendously improved sequencing output while being more time and cost-efficient in comparison to Sanger sequencing. The authors describe short-read sequencing approaches, such as sequencing by synthesis, ion semiconductor sequencing, and nanoball sequencing. Third-generation long-read sequencing now promises to overcome many of the limitations of short-read sequencing, such as the ability to reliably resolve repeat sequences and large genomic rearrangements. By combining complementary methods with massively parallel DNA sequencing, a greater insight into the biological context of disease mechanisms is now possible. Emerging methodologies, such as advances in nanopore technology, in situ nucleic acid sequencing, and microscopy-based sequencing, will continue the rapid evolution of this area. These new technologies hold many potential applications for hematological disorders, with the promise of precision and personalized medical care in the future.
The Zero Childhood Cancer Program is a precision medicine program to benefit children with poor-outcome, rare, relapsed or refractory cancer. Using tumor and germline whole genome sequencing (WGS) ...and RNA sequencing (RNAseq) across 252 tumors from high-risk pediatric patients with cancer, we identified 968 reportable molecular aberrations (39.9% in WGS and RNAseq, 35.1% in WGS only and 25.0% in RNAseq only). Of these patients, 93.7% had at least one germline or somatic aberration, 71.4% had therapeutic targets and 5.2% had a change in diagnosis. WGS identified pathogenic cancer-predisposing variants in 16.2% of patients. In 76 central nervous system tumors, methylome analysis confirmed diagnosis in 71.1% of patients and contributed to a change of diagnosis in two patients (2.6%). To date, 43 patients have received a recommended therapy, 38 of whom could be evaluated, with 31% showing objective evidence of clinical benefit. Comprehensive molecular profiling resolved the molecular basis of virtually all high-risk cancers, leading to clinical benefit in some patients.
Predicting the impact of coding and noncoding variants on splicing is challenging, particularly in non-canonical splice sites, leading to missed diagnoses in patients. Existing splice prediction ...tools are complementary but knowing which to use for each splicing context remains difficult. Here, we describe Introme, which uses machine learning to integrate predictions from several splice detection tools, additional splicing rules, and gene architecture features to comprehensively evaluate the likelihood of a variant impacting splicing. Through extensive benchmarking across 21,000 splice-altering variants, Introme outperformed all tools (auPRC: 0.98) for the detection of clinically significant splice variants. Introme is available at https://github.com/CCICB/introme .
Genes encoding TRK are oncogenic drivers in multiple tumour types including infantile fibrosarcoma, papillary thyroid cancer and high-grade gliomas (HGG). TRK fusions have a critical role in ...tumourigenesis in 40% of infant HGG. Here we report the first case of a TRK fusion-driven HGG treated with larotrectinib-the first selective pan-TRK inhibitor in clinical development. This 3-year-old girl had failed multiple therapies including chemotherapy and radiotherapy. Tumour profiling confirmed an ETV6-NTRK3 fusion. Treatment with larotrectinib led to rapid clinical improvement with near total resolution of primary and metastatic lesions on MRI imaging. This is the first report of a TRK fusion glioma successfully treated with a TRK inhibitor.
Extensive molecular heterogeneity of pancreatic ductal adenocarcinoma (PDA), few effective therapies and high mortality make this disease a prime model for advancing development of tailored ...therapies. The p16-cyclin D-cyclin-dependent kinase 4/6-retinoblastoma (RB) protein (CDK4) pathway, regulator of cell proliferation, is deregulated in PDA. Our aim was to develop a novel personalised treatment strategy for PDA based on targeting CDK4.
Sensitivity to potent CDK4/6 inhibitor PD-0332991 (palbociclib) was correlated to protein and genomic data in 19 primary patient-derived PDA lines to identify biomarkers of response. In vivo efficacy of PD-0332991 and combination therapies was determined in subcutaneous, intrasplenic and orthotopic tumour models derived from genome-sequenced patient specimens and genetically engineered model. Mechanistically, monotherapy and combination therapy were investigated in the context of tumour cell and extracellular matrix (ECM) signalling. Prognostic relevance of companion biomarker, RB protein, was evaluated and validated in independent PDA patient cohorts (>500 specimens).
Subtype-specific in vivo efficacy of PD-0332991-based therapy was for the first time observed at multiple stages of PDA progression: primary tumour growth, recurrence (second-line therapy) and metastatic setting and may potentially be guided by a simple biomarker (RB protein). PD-0332991 significantly disrupted surrounding ECM organisation, leading to increased quiescence, apoptosis, improved chemosensitivity, decreased invasion, metastatic spread and PDA progression in vivo. RB protein is prevalent in primary operable and metastatic PDA and may present a promising predictive biomarker to guide this therapeutic approach.
This study demonstrates the promise of CDK4 inhibition in PDA over standard therapy when applied in a molecular subtype-specific context.
Tumour cellularity, the relative proportion of tumour and normal cells in a sample, affects the sensitivity of mutation detection, copy number analysis, cancer gene expression and methylation ...profiling. Tumour cellularity is traditionally estimated by pathological review of sectioned specimens; however this method is both subjective and prone to error due to heterogeneity within lesions and cellularity differences between the sample viewed during pathological review and tissue used for research purposes. In this paper we describe a statistical model to estimate tumour cellularity from SNP array profiles of paired tumour and normal samples using shifts in SNP allele frequency at regions of loss of heterozygosity (LOH) in the tumour. We also provide qpure, a software implementation of the method. Our experiments showed that there is a medium correlation 0.42 (Formula: see text-value=0.0001) between tumor cellularity estimated by qpure and pathology review. Interestingly there is a high correlation 0.87 (Formula: see text-value Formula: see text 2.2e-16) between cellularity estimates by qpure and deep Ion Torrent sequencing of known somatic KRAS mutations; and a weaker correlation 0.32 (Formula: see text-value=0.004) between IonTorrent sequencing and pathology review. This suggests that qpure may be a more accurate predictor of tumour cellularity than pathology review. qpure can be downloaded from https://sourceforge.net/projects/qpure/.
Long noncoding RNAs (lncRNAs) cause Polycomb repressive complexes (PRCs) to spread over broad regions of the mammalian genome. We report that in mouse trophoblast stem cells, the Airn and Kcnq1ot1 ...lncRNAs induce PRC-dependent chromatin modifications over multi-megabase domains. Throughout the Airn-targeted domain, the extent of PRC-dependent modification correlated with intra-nuclear distance to the Airn locus, preexisting genome architecture, and the abundance of Airn itself. Specific CpG islands (CGIs) displayed characteristics indicating that they nucleate the spread of PRCs upon exposure to Airn. Chromatin environments surrounding Xist, Airn, and Kcnq1ot1 suggest common mechanisms of PRC engagement and spreading. Our data indicate that lncRNA potency can be tightly linked to lncRNA abundance and that within lncRNA-targeted domains, PRCs are recruited to CGIs via lncRNA-independent mechanisms. We propose that CGIs that autonomously recruit PRCs interact with lncRNAs and their associated proteins through three-dimensional space to nucleate the spread of PRCs in lncRNA-targeted domains.
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•Airn and Kcnq1ot1 direct PRCs to multi-megabase domains in trophoblast stem cells•Airn-induced H3K27me3 correlates with DNA structure, RNA abundance, and PRC-bound CGIs•Deletion of a single PRC-bound CGI caused a 4.5-Mb loss of H3K27me3 in the Airn domain•Like Xist, Airn and Kcnq1ot1 require HNRNPK to spread H3K27me3 in domains
Schertzer et al. studied relationships between long noncoding RNAs (lncRNAs) and Polycomb repressive complexes (PRCs) in mouse trophoblast stem cells. They found that genome architecture, lncRNA abundance, and CpG island DNA each play important roles in dictating the intensity of PRC-induced chromatin modifications within lncRNA target domains.
Whole-exome sequencing (WES) has revolutionized Mendelian diagnostics, however, there is no consensus on the timing of data review in undiagnosed individuals and only preliminary data on the ...cost-effectiveness of this technology. We aimed to assess the utility of WES data reanalysis for diagnosis in Mendelian disorders and to analyze the cost-effectiveness of this technology compared with a traditional diagnostic pathway.
WES was applied to a cohort of 54 patients from 37 families with a variety of Mendelian disorders to identify the genetic etiology. Reanalysis was performed after 12 months with an improved WES diagnostic pipeline. A comparison was made between costs of a modeled WES pathway and a traditional diagnostic pathway in a cohort with intellectual disability (ID).
Reanalysis of WES data at 12 months improved diagnostic success from 30 to 41% due to interim publication of disease genes, expanded phenotype data from referrer, and an improved bioinformatics pipeline. Cost analysis on the ID cohort showed average cost savings of US$586 (AU$782) for each additional diagnosis.
Early application of WES in Mendelian disorders is cost-effective and reanalysis of an undiagnosed individual at a 12-month time point increases total diagnoses by 11%.
Abstract
Motivation
Genome sequencing has had a remarkable impact on our ability to study the effects of human genetic variation, however, variant interpretation remains the major bottleneck. ...Understanding the potential impact of variants, including structural variants, requires extensive annotation from disparate sources of knowledge, and in silico prediction algorithms.
Results
We introduce Seave, an intuitive web platform that enables all types of variants to be securely stored, annotated and filtered. Variants are annotated with allele frequencies and pathogenicity assessments from many popular databases and in silico pathogenicity prediction scores. Seave enables filtering of variants with specific inheritance patterns, including somatic variants, by quality, allele frequencies and gene lists which can be curated and saved. Seave was made for whole genome data and is capable of storing and querying copy number and structural variants.
Availability and implementation
To demo Seave with public data, see https://www.seave.bio. Source code is available at http://code.seave.bio and extensive documentation is available at http://documentation.seave.bio. Seave can be locally installed on an Apache server with PHP and MySQL, or we provide an Amazon Machine Image for quick deployment. For commercial and clinical diagnostic licensing, contact the corresponding author.
Supplementary information
Supplementary data are available at Bioinformatics online.
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