Sequence Artifacts in DNA from Formalin-Fixed Tissues: Causes and Strategies for Minimization

Species-resolved sequencing of low-biomass or degraded microbiomes using 2bRAD-M

Microbiome samples with low microbial biomass or severe DNA degradation remain challenging for amplicon-based or whole-metagenome sequencing approaches. Here, we introduce 2bRAD-M, a highly reduced and cost-effective strategy which only sequences ~ 1% of metagenome and can simultaneously produce species-level bacterial, archaeal, and fungal profiles. 2bRAD-M can accurately generate species-level taxonomic profiles for otherwise hard-to-sequence samples with merely 1 pg of total DNA, high host DNA contamination, or severely fragmented DNA from degraded samples. Tests of 2bRAD-M on various stool, skin, environmental, and clinical FFPE samples suggest a successful reconstruction of comprehensive, high-resolution microbial profiles.

Detection of Low-Copy Human Virus DNA upon Prolonged Formalin Fixation

Formalin fixation, albeit an outstanding method for morphological and molecular preservation, induces DNA damage and cross-linking, which can hinder nucleic acid screening. This is of particular concern in the detection of low-abundance targets, such as persistent DNA viruses. In the present study, we evaluated the analytical sensitivity of viral detection in lung, liver, and kidney specimens from four deceased individuals. The samples were either frozen or incubated in formalin (±paraffin embedding) for up to 10 days. We tested two DNA extraction protocols for the control of efficient yields and viral detections. We used short-amplicon qPCRs (63–159 nucleotides) to detect 11 DNA viruses, as well as hybridization capture of these plus 27 additional ones, followed by deep sequencing. We observed marginally higher ratios of amplifiable DNA and scantly higher viral genoprevalences in the samples extracted with the FFPE dedicated protocol. Based on the findings in the frozen samples, most viruses were detected regardless of the extended fixation times. False-negative calls, particularly by qPCR, correlated with low levels of viral DNA (<250 copies/million cells) and longer PCR amplicons (>150 base pairs). Our data suggest that low-copy viral DNAs can be satisfactorily investigated from FFPE specimens, and encourages further examination of historical materials.

Preanalytical Variables and Sample Quality Control for Clinical Variant Analysis

Broad molecular profiling by next-generation sequencing of solid tumors has become a critical tool for clinical decision-making in the era of precision oncology. In addition to many already approved targeted therapies, more than half of ongoing oncology-related clinical trials are biomarker-driven. Therefore, accurate and reliable assays are needed to assess the genetic make-up of tumor cells and guide clinicians in the therapy decision process. In order to obtain high-quality NGS data for variant detection, certain preanalytical steps and quality metrics should be followed. These include assessment of sample types, choice of extraction method, library preparation technology, sequencing platform, and finally sequencing quality control. Each of these steps has certain challenges and pitfalls that need to be addressed and overcome, respectively. In this chapter, we address the preanalytical quality control and how each of the involved steps may influence the final result. Following these guidelines and QC metrics may help in obtaining optimal results that will allow the precise and robust assessment of genetic variants in a clinical setting.

An efficient procedure for the recovery of DNA from formalin-fixed paraffin-embedded tissue sections

With the advent of new molecular diagnostic techniques, retrieving DNA from the formalin-fixed paraffin-embedded (FFPE) tissues has become an essential yet challenging step for efficient downstream processes. Owing to low quality and quantity of DNA retrieved from the FFPE sections, the process is often impractical and needs significant improvements. Here, we established an efficient method for the purification of DNA from FFPE specimens by optimizing incubation temperature, incubation time, and the concentration of a formalin scavenger tris(hydroxymethyl)aminomethane (Tris) for reverse-crosslinking. The optimized method, named "Highly concentrated Tris-mediated DNA extraction" (HiTE), yielded three times the DNA yield per tissue slice compared with a representative DNA extraction kit. Moreover, the use of HiTE-extracted DNA increased the yield of the sequencing library three times and accordingly yielded a log higher and more reproducible sequencing library compared with that obtained using the commonly used commercial kit. The sequencing library prepared from HiTE-extracted FFPE-DNA had longer inserts and produced reads that evenly covered the reference genome. Successful application of HiTE-extracted FFPE-DNA for whole-genome and targeted gene panel sequencing indicates its practical usability.

CUT&Tag-BS for simultaneous profiling of histone modification and DNA methylation with high efficiency and low cost

It remains a challenge to decipher the complex relationship between DNA methylation, histone modification, and the underlying DNA sequence with limited input material. Here, we developed an efficient, low-input, and low-cost method for the simultaneous profiling of genomic localization of histone modification and methylation status of the underlying DNA at single-base resolution from the same cells in a single experiment by integrating cleavage under targets and tagmentation (CUT&Tag) with tagmentation-based bisulfite sequencing (CUT&Tag-BS). We demonstrated the validity of our method using representative histone modifications of euchromatin and constitutive and facultative heterochromatin (H3K4me1, H3K9me3, and H3K27me3, respectively). Similar histone modification enrichment patterns were observed in CUT&Tag-BS compared with non-bisulfite-treated control, and H3K4me1-marked regions were found to mostly be CpG poor, lack methylation concordance, and exhibit prevalent DNA methylation heterogeneity among mouse embryonic stem cells (mESCs). We anticipate that CUT&Tag-BS will be widely applied to directly address the genomic relationship between DNA methylation and histone modification, especially in low-input scenarios with precious biological samples.

MicroSEC filters sequence errors for formalin-fixed and paraffin-embedded samples

The clinical sequencing of tumors is usually performed on formalin-fixed, paraffin-embedded samples and results in many sequencing errors. We identified that most of these errors are detected in chimeric reads caused by single-strand DNA molecules with microhomology. During the end-repair step of library preparation, mutations are introduced by the mis-annealing of two single-strand DNA molecules comprising homologous sequences. The mutated bases are distributed unevenly near the ends in the individual reads. Our filtering pipeline, MicroSEC, focuses on the uneven distribution of mutations in each read and removes the sequencing errors in formalin-fixed, paraffin-embedded samples without over-eliminating the mutations detected also in fresh frozen samples. Amplicon-based sequencing using 97 mutations confirmed that the sensitivity and specificity of MicroSEC were 97% (95% confidence interval: 82–100%) and 96% (95% confidence interval: 88–99%), respectively. Our pipeline will increase the reliability of the clinical sequencing and advance the cancer research using formalin-fixed, paraffin-embedded samples.

Masachika Ikegami and Shinji Kohsaka et al. develop MicroSEC, a computational pipeline to filter sequencing artifacts from archival formalin-fixed and paraffin-embedded samples. Given that archival FFPE tissue is of great interest for genomic analysis, but difficult to reliably analyze, this tool may improve the ability of researchers to probe sequencing data from these samples.

PbGP43 Genotyping Using Paraffin-Embedded Biopsies of Human Paracoccidioidomycosis Reveals a Genetically Distinct Lineage in the Paracoccidioides brasiliensis Complex

Paracoccidioidomycosis (PCM) is a systemic mycosis caused by a group of cryptic species embedded in the Paracoccidioides brasiliensis complex and Paracoccidioides lutzii. Four species were recently inferred to belong to the P. brasiliensis complex, but the high genetic diversity found in both human and environmental samples have suggested that the number of lineages may be higher. This study aimed to assess the 43-kilodalton glycoprotein genotypes (PbGP43) in paraffin-embedded samples from PCM patients to infer the phylogenetic lineages of the P. brasiliensis complex responsible for causing the infection. Formalin-fixed, paraffin-embedded (FFPE) tissue samples from patients with histopathological diagnosis of PCM were analyzed. DNAs were extracted and amplified for a region of the second exon of the PbGP43 gene. Products were sequenced and aligned with other PbGP43 sequences available. A haplotype network and the phylogenetic relationships among sequences were inferred. Amino acid substitutions were investigated regarding the potential to modify physicochemical properties in the proteins. Six phylogenetic lineages were identified as belonging to the P. brasiliensis complex. Two lineages did not group with any of the four recognized species of the complex, and, interestingly, one of them comprised only FFPE samples. A coinfection involving two lineages was found. Five parsimony-informative sites were identified and three of them showed radical non-synonymous substitutions with the potential to promote changes in the protein. This study expands the knowledge regarding the genetic diversity existing in the P. brasiliensis complex and shows the potential of FFPE samples in species identification and in detecting coinfections.

Genomic Profiling of Lung Adenocarcinoma in Never-Smokers

PURPOSE

Approximately 10%-40% of patients with lung cancer report no history of tobacco smoking (never-smokers). We analyzed whole-exome and RNA-sequencing data of 160 tumor and normal lung adenocarcinoma (LUAD) samples from never-smokers to identify clinically actionable alterations and gain insight into the environmental and hereditary risk factors for LUAD among never-smokers.

METHODS

We performed whole-exome and RNA-sequencing of 88 and 69 never-smoker LUADs. We analyzed these data in conjunction with data from 76 never-smoker and 299 smoker LUAD samples sequenced by The Cancer Genome Atlas and Clinical Proteomic Tumor Analysis Consortium.

RESULTS

We observed a high prevalence of clinically actionable driver alterations in never-smoker LUADs compared with smoker LUADs (78%-92% v 49.5%; P < .0001). Although a subset of never-smoker samples demonstrated germline alterations in DNA repair genes, the frequency of samples showing germline variants in cancer predisposing genes was comparable between smokers and never-smokers (6.4% v 6.9%; P = .82). A subset of never-smoker samples (5.9%) showed mutation signatures that were suggestive of passive exposure to cigarette smoke. Finally, analysis of RNA-sequencing data showed distinct immune transcriptional subtypes of never-smoker LUADs that varied in their expression of clinically relevant immune checkpoint molecules and immune cell composition.

CONCLUSION

In this comprehensive genomic and transcriptome analysis of never-smoker LUADs, we observed a potential role for germline variants in DNA repair genes and passive exposure to cigarette smoke in the pathogenesis of a subset of never-smoker LUADs. Our findings also show that clinically actionable driver alterations are highly prevalent in never-smoker LUADs, highlighting the need for obtaining biopsies with adequate cellularity for clinical genomic testing in these patients.

Single-strand specific nuclease enhances accuracy of error-corrected sequencing and improves rare mutation-detection sensitivity

Error-corrected sequences (ECSs) that utilize double-stranded DNA sequences are useful in detecting mutagen-induced mutations. However, relatively higher frequencies of G:C > T:A (1 × 10⁻⁷ bp) and G:C > C:G (2 × 10⁻⁷ bp) errors decrease the accuracy of detection of rare G:C mutations (approximately 10⁻⁷ bp). Oxidized guanines in single-strand (SS) overhangs generated after shearing could serve as the source of these errors. To remove these errors, we first computationally discarded up to 20 read bases corresponding to the ends of the DNA fragments. Error frequencies decreased proportionately with trimming length; however, the results indicated that they were not sufficiently removed. To efficiently remove SS overhangs, we evaluated three mechanistically distinct SS-specific nucleases (S1 Nuclease, mung bean nuclease, and RecJf exonuclease) and found that they were more efficient than computational trimming. Consequently, we established Jade-Seq™, an ECS protocol with S1 Nuclease treatment, which reduced G:C > T:A and G:C > C:G errors to 0.50 × 10⁻⁷ bp and 0.12 × 10⁻⁷ bp, respectively. This was probably because S1 Nuclease removed SS regions, such as gaps and nicks, depending on its wide substrate specificity. Subsequently, we evaluated the mutation-detection sensitivity of Jade-Seq™ using DNA samples from TA100 cells exposed to 3-methylcholanthrene and 7,12-dimethylbenz[a]anthracene, which contained the rare G:C > T:A mutation (i.e., 2 × 10⁻⁷ bp). Fold changes of G:C > T:A compared to the vehicle control were 1.2- and 1.3-times higher than those of samples without S1 Nuclease treatment, respectively. These findings indicate the potential of Jade-Seq™ for detecting rare mutations and determining the mutagenicity of environmental mutagens.

Whole genome and exome sequencing reference datasets from a multi-center and cross-platform benchmark study

With the rapid advancement of sequencing technologies, next generation sequencing (NGS) analysis has been widely applied in cancer genomics research. More recently, NGS has been adopted in clinical oncology to advance personalized medicine. Clinical applications of precision oncology require accurate tests that can distinguish tumor-specific mutations from artifacts introduced during NGS processes or data analysis. Therefore, there is an urgent need to develop best practices in cancer mutation detection using NGS and the need for standard reference data sets for systematically measuring accuracy and reproducibility across platforms and methods. Within the SEQC2 consortium context, we established paired tumor-normal reference samples and generated whole-genome (WGS) and whole-exome sequencing (WES) data using sixteen library protocols, seven sequencing platforms at six different centers. We systematically interrogated somatic mutations in the reference samples to identify factors affecting detection reproducibility and accuracy in cancer genomes. These large cross-platform/site WGS and WES datasets using well-characterized reference samples will represent a powerful resource for benchmarking NGS technologies, bioinformatics pipelines, and for the cancer genomics studies.

Technical aspects of the use of cytopathological specimens for diagnosis and predictive testing in malignant epithelial neoplasms of the lung

Lung cancer is a leading cause of cancer mortality worldwide but recent years have seen a rapidly rising proportion of cases of advanced non-small cell carcinoma amenable to increasingly targeted therapy, initially based on the differential response to systemic treatment of tumours of squamous or glandular differentiation. In two-thirds of the cases, where patients present with advanced disease, both primary pathological diagnosis and biomarker testing is based on small biopsies and cytopathological specimens. The framework of this article is an overview of the technical aspect of each stage of the specimen pathway with emphasis on maximising potential for success when using small cytology samples. It brings together the current literature addressing pre-analytical and analytical aspects of specimen acquisition, performing rapid onsite evaluation, and undertaking diagnostic and predictive testing using immunocytochemistry and molecular platforms. The advantages and drawbacks of performing analysis on cell block and non-cell block specimen preparations is discussed.

Performance of 16S Metagenomic Profiling in Formalin-Fixed Paraffin-Embedded versus Fresh-Frozen Colorectal Cancer Tissues

Formalin-fixed, paraffin-embedded (FFPE) tissues represent the most widely available clinical material to study colorectal cancer (CRC). However, the accuracy and clinical validity of FFPE microbiome profiling in CRC is uncertain. Here, we compared the microbial composition of 10 paired fresh-frozen (FF) and FFPE CRC tissues using 16S rRNA sequencing and RNA-ISH. Both sample types showed different microbial diversity and composition. FF samples were enriched in archaea and representative CRC-associated bacteria, such as Firmicutes, Bacteroidetes and Fusobacteria. Conversely, FFPE samples were mainly enriched in typical contaminants, such as Sphingomonadales and Rhodobacterales. RNA-ISH in FFPE tissues confirmed the presence of CRC-associated bacteria, such as Fusobacterium and Bacteroides, as well as Propionibacterium allowing discrimination between tumor-associated and contaminant taxa. An internal quality index showed that the degree of similarity within sample pairs inversely correlated with the dominance of contaminant taxa. Given the importance of FFPE specimens for larger studies in human cancer genomics, our findings may provide useful indications on potential confounding factors to consider for accurate and reproducible metagenomics analyses.

Oncomine™ Comprehensive Assay v3 vs. Oncomine™ Comprehensive Assay Plus

Simple Summary

The detection of genetic alterations in cancer is important to obtain knowledge of the underlying mutational tumor composition. Knowing the mutational profile can assist oncologists on tailoring optimal personalized treatments. Moreover, obtaining additional information from a broader cancer-related gene panel, without compromising performance, can benefit both current and future patients. In this study, we assessed the performance of gene mutations identified from sequencing using the newly Oncomine™ Comprehensive Assay Plus (OCA-Plus). The assessment was performed in comparison to gene mutations identified from sequencing using the Oncomine™ Comprehensive Assay v3 (OCAv3), currently used in our routine clinical setting. Therefore, an investigation of their performance was conducted on intersecting nucleotide positions within overlapping genes covered by both the OCA-Plus and the OCAv3. We show here that there is a 91% concordance between identified pathogenic and likely pathogenic classified variants.

Abstract

The usage of next generation sequencing in combination with targeted gene panels has enforced a better understanding of tumor compositions. The identification of key genomic biomarkers underlying a disease are crucial for diagnosis, prognosis, treatment and therapeutic responses. The Oncomine™ Comprehensive Assay v3 (OCAv3) covers 161 cancer-associated genes and is routinely employed to support clinical decision making for a therapeutic course. An improved version, Oncomine™ Comprehensive Assay Plus (OCA-Plus), has been recently developed, covering 501 genes (144 overlapping with OCAv3) in addition to microsatellite instability (MSI) and tumor mutational burden (TMB) assays in one workflow. The validation of MSI and TMB was not addressed in the present study. However, the implementation of new assays must be validated and confirmed across multiple samples before it can be introduced into a clinical setting. Here, we report the comparison of DNA sequencing results from 50 ovarian cancer formalin-fixed, paraffin-embedded samples subjected to OCAv3 and OCA-Plus. A validation assessment of gene mutations identified using OCA-Plus was performed on the 144 overlapping genes and 313,769 intersecting nucleotide positions of the OCAv3 and the OCA-Plus. Our results showed a 91% concordance within variants classified as likely-pathogenic or pathogenic. Moreover, results showed that a region of PTEN is poorly covered by the OCA-Plus assay, hence, we implemented rescue filters for those variants. In conclusion, the OCA-Plus can reflect the mutational profile of genomic variants compared with OCAv3 of 144 overlapping genes, without compromising performance.

Tracking de novo protein synthesis in the activated sludge microbiome using BONCAT-FACS

In order to ensure stable performance of engineered biotechnologies that rely on mixed microbial community systems, it is important to identify process-specific microbial traits and study their in-situ activity and responses to changing environmental conditions and system operational parameters. We used BioOrthogonal Non-Canonical Amino acid Tagging (BONCAT) in combination with Fluorescence-Activated Cell Sorting (FACS) and 16S rRNA gene amplicon sequencing to identify translationally active cells in activated sludge. We found that only a subset of the activated sludge microbiome is translationally active during the aerobic treatment phase of a full-scale sequencing batch reactor designed to enhance biological phosphorus removal from municipal wastewater. Relative abundance of amplicon sequence variants was not a reliable predictor of species activity. BONCAT-positive and -negative cells revealed a broad range of population-wide and taxa-specific translational heterogeneity. BONCAT-FACS in combination with amplicon sequencing can provide new insights into the ecophysiology of highly dynamic microbiomes in activated sludge systems.

UNMASC: tumor-only variant calling with unmatched normal controls

Despite years of progress, mutation detection in cancer samples continues to require significant manual review as a final step. Expert review is particularly challenging in cases where tumors are sequenced without matched normal control DNA. Attempts have been made to call somatic point mutations without a matched normal sample by removing well-known germline variants, utilizing unmatched normal controls, and constructing decision rules to classify sequencing errors and private germline variants. With budgetary constraints related to computational and sequencing costs, finding the appropriate number of controls is a crucial step to identifying somatic variants. Our approach utilizes public databases for canonical somatic variants as well as germline variants and leverages information gathered about nearby positions in the normal controls. Drawing from our cohort of targeted capture panel sequencing of tumor and normal samples with varying tumortypes and demographics, these served as a benchmark for our tumor-only variant calling pipeline to observe the relationship between our ability to correctly classify variants against a number of unmatched normals. With our benchmarked samples, approximately ten normal controls were needed to maintain 94% sensitivity, 99% specificity and 76% positive predictive value, far outperforming comparable methods. Our approach, called UNMASC, also serves as a supplement to traditional tumor with matched normal variant calling workflows and can potentially extend to other concerns arising from analyzing next generation sequencing data.

Proteotranscriptomic classification and characterization of pancreatic neuroendocrine neoplasms

Pancreatic neuroendocrine neoplasms (PNENs) are biologically and clinically heterogeneous. Here, we use a multi-omics approach to uncover the molecular factors underlying this heterogeneity. Transcriptomic analysis of 84 PNEN specimens, drawn from two cohorts, is substantiated with proteomic profiling and identifies four subgroups: Proliferative, PDX1-high, Alpha cell-like and Stromal/Mesenchymal. The Proliferative subgroup, consisting of both well- and poorly differentiated specimens, is associated with inferior overall survival probability. The PDX1-high and Alpha cell-like subgroups partially resemble previously described subtypes, and we further uncover distinctive metabolism-related features in the Alpha cell-like subgroup. The Stromal/Mesenchymal subgroup exhibits molecular characteristics of YAP1/WWTR1(TAZ) activation suggestive of Hippo signaling pathway involvement in PNENs. Whole-exome sequencing reveals subgroup-enriched mutational differences, supported by activity inference analysis, and identifies hypermorphic proto-oncogene variants in 14.3% of sequenced PNENs. Our study reveals differences in cellular signaling axes that provide potential directions for PNEN patient stratification and treatment strategies.

Precision diagnostics: Integration of tissue pathology and genomics in cancer

Traditionally, cancer diagnosis and management has been reactionary in that symptoms lead to investigations, then a diagnosis is followed by clinical management. This process is heavily dependent on tissue diagnosis mainly by histopathology and to a lesser extent, cytopathology. However, in recent times there has been a shift towards precision medicine to enable prevention, prediction and personalisation in healthcare. The core of precision medicine is optimising therapeutic benefit for patients, by using genomic and molecular profiling, analogously termed precision pathology. This review explores (1) the evolution of pathology from a para-clinical discipline to a mainstream medical field integral to oncology tumour boards; (2) its critical role in preventative, diagnostic, therapeutic and follow-up cancer care; (3) the future of tissue pathology in the era of precision oncology; and (4) how pathologists may evolve to future-proof their profession.

The Japanese Society of Pathology Practical Guidelines on the handling of pathological tissue samples for cancer genomic medicine

Clinical cancer genomic testing based on next‐generation sequencing can help select genotype‐matched therapy and provide diagnostic and prognostic information. Pathological tissue from malignant tumors obtained during routine practice are frequently used for genomic testing. This article is aimed to standardize the proper handling of pathological specimens in practice for genomic medicine based on the findings established in “Guidelines on the handling of pathological tissue samples for genomic medicine (in Japanese)” published by The Japanese Society of Pathology (JSP) in 2018. The two‐part practical guidelines are based on empirical data analyses; Part 1 describes the standard preanalytic operating procedures for tissue collection, processing, and storage of formalin‐fixed paraffin‐embedded (FFPE) samples, while Part 2 describes the assessment and selection of FFPE samples appropriate for genomic testing, typically conducted by a pathologist. The guidelines recommend that FFPE sample blocks be used within 3 years from preparation, and the tumor content should be ≥30% (minimum 20%). The empirical data were obtained from clinical studies performed by the JSP in collaboration with leading Japanese cancer genome research projects. The Japanese Ministry of Health, Labour, and Welfare (MHLW) recommended to comply with the JSP practical guidelines in implementing cancer genomic testing under the national health insurance system in over 200 MHLW‐designated core and cooperative cancer genome medicine hospitals in Japan.

Viral metagenomic sequencing in the diagnosis of meningoencephalitis: a review of technical advances and diagnostic yield

INTRODUCTION

Meningoencephalitis patients are often severely impaired and benefit from early etiological diagnosis, though many cases remain without identified cause. Metagenomics as pathogen agnostic approach can result in additional etiological findings; however, the exact diagnostic yield when used as a secondary test remains unknown.

AREAS COVERED

This review aims to highlight recent advances with regard to wet and dry lab methodologies of metagenomic testing and technical milestones that have been achieved. A selection of procedures currently applied in accredited diagnostic laboratories is described in more detail to illustrate best practices. Furthermore, a meta-analysis was performed to assess the additional diagnostic yield utilizing metagenomic sequencing in meningoencephalitis patients. Finally, the remaining challenges for successful widespread implementation of metagenomic sequencing for the diagnosis of meningoencephalitis are addressed in a future perspective.

EXPERT OPINION

The last decade has shown major advances in technical possibilities for using mNGS in diagnostic settings including cloud-based analysis. An additional advance may be the current established infrastructure of platforms for bioinformatic analysis of SARS-CoV-2, which may assist to pave the way for global use of clinical metagenomics.

Formalin-Fixed and Paraffin-Embedded Samples for Next Generation Sequencing: Problems and Solutions

Over the years, increasing information has been asked of the pathologist: we have moved from a purely morphological diagnosis to biomolecular and genetic studies, which have made it possible to implement the use of molecular targeted therapies, such as anti-epidermal growth factor receptor (EGFR) molecules in EGFR-mutated lung cancer, for example. Today, next generation sequencing (NGS) has changed the approach to neoplasms, to the extent that, in a short time, it has gained a place of absolute importance and diagnostic, prognostic and therapeutic utility. In this scenario, formaldehyde-fixed and paraffin-embedded (FFPE) biological tissue samples are a source of clinical and molecular information. However, problems can arise in the genetic material (DNA and RNA) for use in NGS due to fixation, and work is being devoted to possible strategies to reduce its effects. In this paper, we discuss the applications of FFPE tissue samples in the execution of NGS, we focus on the problems arising with the use of this type of material for nucleic acid extraction and, finally, we consider the most useful strategies to prevent and reduce single nucleotide polymorphisms (SNV) and other fixation artifacts.

Unlocking inaccessible historical genomes preserved in formalin

Museum specimens represent an unparalleled record of historical genomic data. However, the widespread practice of formalin preservation has thus far impeded genomic analysis of a large proportion of specimens. Limited DNA sequencing from formalin-preserved specimens has yielded low genomic coverage with unpredictable success. We set out to refine sample processing methods and to identify specimen characteristics predictive of sequencing success. With a set of taxonomically diverse specimens collected between 1962 and 2006 and ranging in preservation quality, we compared the efficacy of several end-to-end whole genome sequencing workflows alongside a k-mer-based trimming-free read alignment approach to maximize mapping of endogenous sequence. We recovered complete mitochondrial genomes and up to 3× nuclear genome coverage from formalin-preserved tissues. Hot alkaline lysis coupled with phenol-chloroform extraction out-performed proteinase K digestion in recovering DNA, while library preparation method had little impact on sequencing success. The strongest predictor of DNA yield was overall specimen condition, which additively interacts with preservation conditions to accelerate DNA degradation. Here, we demonstrate a significant advance in capability beyond limited recovery of a small number of loci via PCR or target-capture sequencing. To facilitate strategic selection of suitable specimens for genomic sequencing, we present a decision-making framework that utilizes independent and nondestructive assessment criteria. Sequencing of formalin-preserved specimens will contribute to a greater understanding of temporal trends in genetic adaptation, including those associated with a changing climate. Our work enhances the value of museum collections worldwide by unlocking genomes of specimens that have been disregarded as a valid molecular resource.

Indolent feature of Helicobacter pylori-uninfected intramucosal signet ring cell carcinomas with CDH1 mutations

BACKGROUND

In Helicobacter pylori (Hp)-uninfected individuals, diffuse-type gastric cancer (DGC) was reported as the most common type of cancer. However, the carcinogenic mechanism of Hp-uninfected sporadic DGC is largely unknown.

METHODS

We performed whole-exome sequencing of Hp-uninfected DGCs and Hp-uninfected normal gastric mucosa. For advanced DGCs, external datasets were also analyzed.

RESULTS

Eighteen patients (aged 29-78 years) with DGCs and nine normal subjects (28-77 years) were examined. The mutation burden in intramucosal DGCs (10-66 mutations per exome) from individuals aged 29-73 years was not very different from that in the normal gastric glands, which showed a constant mutation accumulation rate (0.33 mutations/exome/year). Unbiased dN/dS analysis showed that CDH1 somatic mutation was a driver mutation for intramucosal DGC. CDH1 mutation was more frequent in intramucosal DGCs (67%) than in advanced DGCs (27%). In contrast, TP53 mutation was more frequent in advanced DGCs (52%) than in intramucosal DGCs (0%). This discrepancy in mutations suggests that CDH1-mutated intramucosal DGCs make a relatively small contribution to advanced DGC formation. Among the 16 intramucosal DGCs (median size, 6.5 mm), 15 DGCs were pure signet ring cell carcinoma (SRCC) with reduced E-cadherin expression and a low proliferative capacity (median Ki-67 index, 2.4%). Five SRCCs reviewed endoscopically over 2-5 years showed no progression.

CONCLUSIONS

Impaired E-cadherin function due to CDH1 mutation was considered as an early carcinogenic event of Hp-uninfected intramucosal SRCC. Genetic and clinical analyses suggest that Hp-uninfected intramucosal SRCCs may be less likely to develop into advanced DGCs.

Toward best practice in cancer mutation detection with whole-genome and whole-exome sequencing

Clinical applications of precision oncology require accurate tests that can distinguish true cancer-specific mutations from errors introduced at each step of next-generation sequencing (NGS). To date, no bulk sequencing study has addressed the effects of cross-site reproducibility, nor the biological, technical and computational factors that influence variant identification. Here we report a systematic interrogation of somatic mutations in paired tumor-normal cell lines to identify factors affecting detection reproducibility and accuracy at six different centers. Using whole-genome sequencing (WGS) and whole-exome sequencing (WES), we evaluated the reproducibility of different sample types with varying input amount and tumor purity, and multiple library construction protocols, followed by processing with nine bioinformatics pipelines. We found that read coverage and callers affected both WGS and WES reproducibility, but WES performance was influenced by insert fragment size, genomic copy content and the global imbalance score (GIV; G > T/C > A). Finally, taking into account library preparation protocol, tumor content, read coverage and bioinformatics processes concomitantly, we recommend actionable practices to improve the reproducibility and accuracy of NGS experiments for cancer mutation detection.

Mining museums for historical DNA: advances and challenges in museomics

Historical DNA (hDNA), obtained from museum and herbarium specimens, has yielded spectacular new insights into the history of organisms. This includes documenting historical genetic erosion and extinction, discovering species new to science, resolving evolutionary relationships, investigating epigenetic effects, and determining origins of infectious diseases. However, the development of best-practices in isolating, processing, and analyzing hDNA remain under-explored, due to the substantial diversity of specimen preparation types, tissue sources, archival ages, and collecting histories. Thus, for hDNA to reach its full potential, and justify the destructive sampling of the rarest specimens, more experimental work using time-series collections, and the development of improved methods to correct for data asymmetries and biases due to DNA degradation are required.

The mutation profile of differentiated thyroid cancer coexisting with undifferentiated anaplastic cancer resembles that of anaplastic thyroid cancer but not that of archetypal differentiated thyroid cancer

Differentiated thyroid cancer (DTC) has one of the lowest cancer mutational burdens, while anaplastic thyroid cancer (ATC) has a much higher mutation frequency. A fraction of ATC has an associated differentiated component, which suggests the coevolution of both cancers. Here, we aimed to compare mutation frequency in coexisting ATC and DTC diagnosed concurrently in the same thyroid gland (3 cases) as well as in archetypal DTC and ATC alone (5 cases each). Single-nucleotide variations (SNV) and copy number variations (CNV) were analyzed in each case based on the next-generation sequencing data. We found a similar extent of mutational events, both SNV and CNV, in undifferentiated and differentiated components of thyroid cancers coexisting in one patient. The magnitude of these mutations was comparable to the level of mutations observed in ATC alone; yet, it was much higher than in archetypal DTC. This suggested that, despite histopathological features of differentiated tumors, molecular characteristics of such cancers coexisting with ATC and archetypal DTC could be significantly different. Pairwise comparison of mutational profiles of coexisting cancers enabled assumption on the possible evolution of both components, which appeared distinct in 3 analyzed cases. This included independent development of ATC and DTC diagnosed concurrently in two lobes of the same thyroid, as well as the development of anaplastic and differentiated cancer from the common ancestor that putatively gained a key driver mutation (BRAF^V600E or KRAS^Q61R), which was followed either by early or late molecular separation of both cancers.

Canine tumor mutational burden is correlated with TP53 mutation across tumor types and breeds

Spontaneous canine cancers are valuable but relatively understudied and underutilized models. To enhance their usage, we reanalyze whole exome and genome sequencing data published for 684 cases of >7 common tumor types and >35 breeds, with rigorous quality control and breed validation. Our results indicate that canine tumor alteration landscape is tumor type-dependent, but likely breed-independent. Each tumor type harbors major pathway alterations also found in its human counterpart (e.g., PI3K in mammary tumor and p53 in osteosarcoma). Mammary tumor and glioma have lower tumor mutational burden (TMB) (median < 0.5 mutations per Mb), whereas oral melanoma, osteosarcoma and hemangiosarcoma have higher TMB (median ≥ 1 mutations per Mb). Across tumor types and breeds, TMB is associated with mutation of TP53 but not PIK3CA, the most mutated genes. Golden Retrievers harbor a TMB-associated and osteosarcoma-enriched mutation signature. Here, we provide a snapshot of canine mutations across major tumor types and breeds.

Continuous Plankton Recorder in the omics era: from marine microbiome to global ocean observations

First routinely deployed in 1931 the Continuous Plankton Recorder (CPR) technology has established the most extensive, marine biological sampling programme in the world. With more than 90 years of sampling, over a total of 8 million nautical miles covered and 500 000 curated samples, the CPR survey provides a gold mine of information available to marine researchers. Such information is likely to exponentially increase thanks to new cutting-edge molecular technologies that are beginning to be applied on CPR samples. In this review we aim to address the exciting developments that the genomic revolution is having on ​CPR applications from the study of marine microbiome to ocean plankton communities leading to ​a new 'digital era' of the global ocean CPR observation programme.

Human Papillomavirus Detection by Whole-Genome Next-Generation Sequencing: Importance of Validation and Quality Assurance Procedures

Next-generation sequencing (NGS) yields powerful opportunities for studying human papillomavirus (HPV) genomics for applications in epidemiology, public health, and clinical diagnostics. HPV genotypes, variants, and point mutations can be investigated in clinical materials and described in previously unprecedented detail. However, both the NGS laboratory analysis and bioinformatical approach require numerous steps and checks to ensure robust interpretation of results. Here, we provide a step-by-step review of recommendations for validation and quality assurance procedures of each step in the typical NGS workflow, with a focus on whole-genome sequencing approaches. The use of directed pilots and protocols to ensure optimization of sequencing data yield, followed by curated bioinformatical procedures, is particularly emphasized. Finally, the storage and sharing of data sets are discussed. The development of international standards for quality assurance should be a goal for the HPV NGS community, similar to what has been developed for other areas of sequencing efforts including microbiology and molecular pathology. We thus propose that it is time for NGS to be included in the global efforts on quality assurance and improvement of HPV-based testing and diagnostics.

Selective multiplexed enrichment for the detection and quantitation of low-fraction DNA variants via low-depth sequencing

DNA sequence variants with allele fractions below 1% are difficult to detect and quantify by sequencing owing to intrinsic errors in sequencing-by-synthesis methods. Although molecular-identifier barcodes can detect mutations with a variant-allele frequency (VAF) as low as 0.1% using next-generation sequencing (NGS), sequencing depths of over 25,000× are required, thus hampering the detection of mutations at high sensitivity in patient samples and in most samples used in research. Here we show that low-frequency DNA variants can be detected via low-depth multiplexed NGS after their amplification, by a median of 300-fold, using polymerase chain reaction and rationally designed 'blocker' oligonucleotides that bind to the variants. Using an 80-plex NGS panel and a sequencing depth of 250×, we detected single nucleotide polymorphisms with a VAF of 0.019% and contamination in human cell lines at a VAF as low as 0.07%. With a 16-plex NGS panel covering 145 mutations across 9 genes involved in melanoma, we detected low-VAF mutations (0.2-5%) in 7 out of the 19 samples of freshly frozen tumour biopsies, suggesting that tumour heterogeneity could be notably higher than previously recognized.

A new method to accurately identify single nucleotide variants using small FFPE breast samples

Most tissue collections of neoplasms are composed of formalin-fixed and paraffin-embedded (FFPE) excised tumor samples used for routine diagnostics. DNA sequencing is becoming increasingly important in cancer research and clinical management; however it is difficult to accurately sequence DNA from FFPE samples. We developed and validated a new bioinformatic pipeline to use existing variant-calling strategies to robustly identify somatic single nucleotide variants (SNVs) from whole exome sequencing using small amounts of DNA extracted from archival FFPE samples of breast cancers. We optimized this strategy using 28 pairs of technical replicates. After optimization, the mean similarity between replicates increased 5-fold, reaching 88% (range 0-100%), with a mean of 21.4 SNVs (range 1-68) per sample, representing a markedly superior performance to existing tools. We found that the SNV-identification accuracy declined when there was less than 40 ng of DNA available and that insertion-deletion variant calls are less reliable than single base substitutions. As the first application of the new algorithm, we compared samples of ductal carcinoma in situ of the breast to their adjacent invasive ductal carcinoma samples. We observed an increased number of mutations (paired-samples sign test, P < 0.05), and a higher genetic divergence in the invasive samples (paired-samples sign test, P < 0.01). Our method provides a significant improvement in detecting SNVs in FFPE samples over previous approaches.

Confirming putative variants at ≤ 5% allele frequency using allele enrichment and Sanger sequencing

Whole exome sequencing (WES) is used to identify mutations in a patient's tumor DNA that are predictive of tumor behavior, including the likelihood of response or resistance to cancer therapy. WES has a mutation limit of detection (LoD) at variant allele frequencies (VAF) of 5%. Putative mutations called at ≤ 5% VAF are frequently due to sequencing errors, therefore reporting these subclonal mutations incurs risk of significant false positives. Here we performed ~ 1000 × WES on fresh-frozen and formalin-fixed paraffin-embedded (FFPE) tissue biopsy samples from a non-small cell lung cancer patient, and identified 226 putative mutations at between 0.5 and 5% VAF. Each variant was then tested using NuProbe NGSure, to confirm the original WES calls. NGSure utilizes Blocker Displacement Amplification to first enrich the allelic fraction of the mutation and then uses Sanger sequencing to determine mutation identity. Results showed that 52% of the 226 (117) putative variants were disconfirmed, among which 2% (5) putative variants were found to be misidentified in WES. In the 66 cancer-related variants, the disconfirmed rate was 82% (54/66). This data demonstrates Blocker Displacement Amplification allelic enrichment coupled with Sanger sequencing can be used to confirm putative mutations ≤ 5% VAF. By implementing this method, next-generation sequencing can reliably report low-level variants at a high sensitivity, without the cost of high sequencing depth.

A simple and rapid approach for human herpesvirus type 8 subtype characterization using single base extension

Sequence analysis of the ORFK1 of human herpesvirus type 8 (HHV-8) allows the identification of six major subtypes (A-F), which are related to human migrations and the clinical progression of Kaposi's sarcoma. Sequencing and subsequent phylogenetic analysis of ORFK1 is considered to be the most reliable method for HHV-8 genotyping. However, it exhibits challenges and limitations. Herein, we designed and validated a single base extension (SBE) protocol for characterization of HHV-8 ORFK1 subtypes. A nested polymerase chain reaction (PCR) protocol was carried out to amplify a small 294-bp PCR product encompassing four single nucleotide polymorphisms at positions 360, 406, 465 and 527 of the HHV-8 genome. Finally, a multiplex SBE technique was developed and validated in 20 samples previously genotyped by phylogenetic analysis. The patterns obtained in this reaction could successfully discriminate between ORFK1 subtypes. The typing results obtained completely matched with those of the 'gold standard' method in all analysed samples. This method can reliably identify HHV-8 subtypes A, B and C, which are the most prevalent ones worldwide, and the remaining subtypes (D, E and F). SBE can be useful as an efficient, rapid and low-cost screening method for viral genotyping in a single tube, particularly samples with low-quality DNA, and with easy data interpretation.

Retrieving high-quality genomic DNA from formalin-fixed paraffin-embedded tissues for multiple molecular analyses

Formalin-fixed paraffin-embedded (FFPE) tissues represent the biggest source of archival materials for molecular biology research and pathology investigations. Nevertheless, fixation by formalin may cause denaturation and modification of macromolecules constraining DNA quality and its downstream applications. In this study, we developed a fast, simple, and cost-effective phenol/chloroform-based protocol for the extraction of high-quality DNA from 101 FFPE colorectal cancer tissue blocks that can be used in multiple molecular studies. DNA samples extracted using this phenol/chloroform protocol and the QIAamp DNA FFPE Tissue kit were evaluated for the quantity, quality, and amplificability. Spectrophotometer analyses revealed significantly higher quality and quantity of DNA samples obtained with the phenol/chloroform protocol as compared to those of the QIAamp DNA FFPE Tissue kit. In addition, the amplificability of these samples as assessed by conventional and multiplex polymerase chain reaction (PCR), followed by sequencing and fragment analyses presented an absolute success rate. Additionally, it is able to amplify a DNA fragment of 725 base-pairs at an adequate amount for downstream applications. This fast, simple, and cost-effective method may facilitate the molecular analyses of a large number of FFPE specimens that best suits the needs of the overall study design in terms of the quality and quantity of the extracted DNA.

Strand Orientation Bias Detector to determine the probability of FFPE sequencing artifacts

Formalin-fixed paraffin-embedded tissue, the most common tissue specimen stored in clinical practice, presents challenges in the analysis due to formalin-induced artifacts. Here, we present Strand Orientation Bias Detector (SOBDetector), a flexible computational platform compatible with all the common somatic SNV-calling pipelines, designed to assess the probability whether a given detected mutation is an artifact. The underlying predictor mechanism is based on the posterior distribution of a Bayesian logistic regression model trained on The Cancer Genome Atlas whole exomes. SOBDetector is a freely available cross-platform program, implemented in Java 1.8.

Clinical Validation of Whole Genome Sequencing for Cancer Diagnostics

Whole genome sequencing (WGS) using fresh-frozen tissue and matched blood samples from cancer patients may become the most complete genetic tumor test. With the increasing availability of small biopsies and the need to screen more number of biomarkers, the use of a single all-inclusive test is preferable over multiple consecutive assays. To meet high-quality diagnostics standards, we optimized and clinically validated WGS sample and data processing procedures, resulting in a technical success rate of 95.6% for fresh-frozen samples with sufficient (≥20%) tumor content. Independent validation of identified biomarkers against commonly used diagnostic assays showed a high sensitivity (recall; 98.5%) and precision (positive predictive value; 97.8%) for detection of somatic single-nucleotide variants and insertions and deletions (across 22 genes), and high concordance for detection of gene amplification (97.0%; EGFR and MET) as well as somatic complete loss (100%; CDKN2A/p16). Gene fusion analysis showed a concordance of 91.3% between DNA-based WGS and an orthogonal RNA-based gene fusion assay. Microsatellite (in)stability assessment showed a sensitivity of 100% with a precision of 94%, and virus detection (human papillomavirus), an accuracy of 100% compared with standard testing. In conclusion, whole genome sequencing has a >95% sensitivity and precision compared with routinely used DNA techniques in diagnostics, and all relevant mutation types can be detected reliably in a single assay.

Multiregion whole-exome sequencing of intraductal papillary mucinous neoplasms reveals frequent somatic KLF4 mutations predominantly in low-grade regions

OBJECTIVE

Intraductal papillary mucinous neoplasms (IPMNs) are non-invasive precursor lesions that can progress to invasive pancreatic cancer and are classified as low-grade or high-grade based on the morphology of the neoplastic epithelium. We aimed to compare genetic alterations in low-grade and high-grade regions of the same IPMN in order to identify molecular alterations underlying neoplastic progression.

DESIGN

We performed multiregion whole exome sequencing on tissue samples from 17 IPMNs with both low-grade and high-grade dysplasia (76 IPMN regions, including 49 from low-grade dysplasia and 27 from high-grade dysplasia). We reconstructed the phylogeny for each case, and we assessed mutations in a novel driver gene in an independent cohort of 63 IPMN cyst fluid samples.

RESULTS

Our multiregion whole exome sequencing identified KLF4, a previously unreported genetic driver of IPMN tumorigenesis, with hotspot mutations in one of two codons identified in >50% of the analyzed IPMNs. Mutations in KLF4 were significantly more prevalent in low-grade regions in our sequenced cases. Phylogenetic analyses of whole exome sequencing data demonstrated diverse patterns of IPMN initiation and progression. Hotspot mutations in KLF4 were also identified in an independent cohort of IPMN cyst fluid samples, again with a significantly higher prevalence in low-grade IPMNs.

CONCLUSION

Hotspot mutations in KLF4 occur at high prevalence in IPMNs. Unique among pancreatic driver genes, KLF4 mutations are enriched in low-grade IPMNs. These data highlight distinct molecular features of low-grade and high-grade dysplasia and suggest diverse pathways to high-grade dysplasia via the IPMN pathway.

Technical in-depth comparison of two massive parallel DNA-sequencing methods for formalin-fixed paraffin-embedded tissue from victims of sudden cardiac death

Sudden cardiac death (SCD) is a tragic and traumatic event. SCD is often associated with hereditary genetic disease and in such cases, sequencing of stored formalin fixed paraffin embedded (FFPE) tissue is often crucial in trying to find a causal genetic variant. This study was designed to compare two massive parallel sequencing assays for differences in sensitivity and precision regarding variants related to SCD in FFPE material. From eight cases of SCD where DNA from blood had been sequenced using HaloPlex, corresponding FFPE samples were collected six years later. DNA from FFPE samples were amplified using HaloPlex HS, sequenced on MiSeq, representing the first method, as well as amplified using modified Twist and sequenced on NextSeq, representing the second method. Molecular barcodes were included to distinguish artefacts from true variants. In both approaches, read coverage, uniformity and variant detection were compared using genomic DNA isolated from blood and corresponding FFPE tissue, respectively. In terms of coverage uniformity, Twist performed better than HaloPlex HS for FFPE samples. Despite higher overall coverage, amplicon-based HaloPlex technologies, both for blood and FFPE tissue, suffered from design and/or performance issues resulting in genes lacking complete coverage. Although Twist had considerably lower overall mean coverage, high uniformity resulted in equal or higher fraction of genes covered at ≥ 20X. By comparing variants found in the matched samples in a pre-defined cardiodiagnostic gene panel, HaloPlex HS for FFPE material resulted in high sensitivity, 98.0% (range 96.6-100%), and high precision, 99.9% (range 99.5-100%) for moderately fragmented samples, but suffered from reduced sensitivity (range 74.2-91.1%) in more severely fragmented samples due to lack of coverage. Twist had high sensitivity, 97.8% (range 96.8-98.7%) and high precision, 99.9% (range 99.3-100%) in all analyzed samples, including the severely fragmented samples.

Next-Generation Sequencing with Liquid Biopsies from Treatment-Naïve Non-Small Cell Lung Carcinoma Patients

Recently, the liquid biopsy (LB), a non-invasive and easy to repeat approach, has started to compete with the tissue biopsy (TB) for detection of targets for administration of therapeutic strategies for patients with advanced stages of lung cancer at tumor progression. A LB at diagnosis of late stage non-small cell lung carcinoma (NSCLC) is also being performed. It may be asked if a LB can be complementary (according to the clinical presentation or systematics) or even an alternative to a TB for treatment-naïve advanced NSCLC patients. Nucleic acid analysis with a TB by next-generation sequencing (NGS) is gradually replacing targeted sequencing methods for assessment of genomic alterations in lung cancer patients with tumor progression, but also at baseline. However, LB is still not often used in daily practice for NGS. This review addresses different aspects relating to the use of LB for NGS at diagnosis in advanced NSCLC, including its advantages and limitations.

Detection of activating mutations in liquid biopsy of Egyptian breast cancer patients using targeted next-generation sequencing: a pilot study

BACKGROUND

Breast cancer (BC) is the 2^nd most prevalent malignancy worldwide and is the most prevalent cancer among Egyptian women. The number of newly described cancer-associated genes has grown exponentially since the emergence of next-generation sequencing (NGS) technology. We aim to identify activating mutations in liquid biopsy of Egyptian breast cancer patients using targeted NGS technology. We also demonstrate the microsatellite instability (MSI) status using BAT25, BAT26, and NR27 markers which are tested on the Bioanalyzer 2100 system.

RESULTS

Twenty-one variants were detected in 15 genes: 7 Substitution-Missense, 12 Substitution-coding silent, and 2 Substitution-intronic. Regarding ClinVar database, out of 21 variants there were 14 benign variants, 3 variants with conflicting interpretations of pathogenicity, 3 variants not reported, and 1 drug response variant. TP53 p.(Pro72Arg) missense mutations were found in 75% of patients. PIK3CA p.(Ile391Met), KDR p.(Gln472His) missense mutations were detected in 25% of patients each. Two patients revealed APC gene missense mutation with p.(Ile1307Lys) and p.(Glu1317Gln) variants. Only one patient showed ATM p.(Phe858Leu) gene mutation and one showed FGFR3 p.(Ala719Thr) variant. Regarding microsatellite instability (MSI) status, 2/8 (25%) patients were MSS, 3/8 (37.5%) patients were MSI-L, and 3/8 (37.5%) patients were MSI-HI.

CONCLUSION

It is essential to use and validate minimally invasive liquid biopsy for activating mutations detection by next-generation sequencing especially in patients with inoperable disease or bone metastasis. This work should be extended with larger patient series with comparison of genetic mutations in liquid-based versus tissue-based biopsy and longer follow up period.

Comprehensive tumor molecular profile analysis in clinical practice

BACKGROUND

Tumor molecular profile analysis by Next Generation Sequencing technology is currently widely applied in clinical practice and has enabled the detection of predictive biomarkers of response to targeted treatment. In parallel with targeted therapies, immunotherapies are also evolving, revolutionizing cancer therapy, with Programmed Death-ligand 1 (PD-L1), Microsatellite instability (MSI), and Tumor Mutational Burden (TMB) analysis being the biomarkers employed most commonly.

METHODS

In the present study, tumor molecular profile analysis was performed using a 161 gene NGS panel, containing the majority of clinically significant genes for cancer treatment selection. A variety of tumor types have been analyzed, including aggressive and hard to treat cancers such as pancreatic cancer. Besides, the clinical utility of immunotherapy biomarkers (TMB, MSI, PD-L1), was also studied.

RESULTS

Molecular profile analysis was conducted in 610 cancer patients, while in 393 of them a at least one biomarker for immunotherapy response was requested. An actionable alteration was detected in 77.87% of the patients. 54.75% of them received information related to on-label or off-label treatment (Tiers 1A.1, 1A.2, 2B, and 2C.1) and 21.31% received a variant that could be used for clinical trial inclusion. The addition to immunotherapy biomarker to targeted biomarkers' analysis in 191 cases increased the number of patients with an on-label treatment recommendation by 22.92%, while an option for on-label or off-label treatment was provided in 71.35% of the cases.

CONCLUSIONS

Tumor molecular profile analysis using NGS is a first-tier method for a variety of tumor types and provides important information for decision making in the treatment of cancer patients. Importantly, simultaneous analysis for targeted therapy and immunotherapy biomarkers could lead to better tumor characterization and offer actionable information in the majority of patients. Furthermore, our data suggest that one in two patients may be eligible for on-label ICI treatment based on biomarker analysis. However, appropriate interpretation of results from such analysis is essential for implementation in clinical practice and accurate refinement of treatment strategy.

Consistency of the S5 DNA methylation classifier in formalin-fixed biopsies versus corresponding exfoliated cells for the detection of pre-cancerous cervical lesions

Methylation biomarkers are promising tools for diagnosis and disease prevention. The S5 classifier is aimed at the prevention of cervical cancer by the early detection of cervical intraepithelial neoplasia (CIN). S5 is based on pyrosequencing a promoter region of EPB41L3 and five late regions of HPV types 16, 18, 31, and 33 following bisulfite conversion of DNA. Good biomarkers should perform well in a variety of sample types such as exfoliated cells, fresh frozen or formalin-fixed paraffin-embedded (FFPE) materials. Here, we tested the performance of S5 on 315 FFPE biopsies with paired exfoliated cervical samples using four different conversion kits (Epitect Bisulfite, Epitect Fast Bisulfite, EZ DNA Methylation, and EZ DNA Methylation-Lightning). The S5 values from FFPE biopsies for all kits were significantly correlated with those obtained from their paired exfoliated cells. For the EZ DNA Methylation kit, we observed an average increased methylation of 4.4% in FFPE. This was due to incomplete conversion of DNA (73% for FFPE vs. 95% for cells). The other kits had a DNA conversion rate in FFPE similar to the cells (95%-97%). S5 performed well at discriminating Collapse

Key Words

• DNA methylation
• S5 classifier
• biomarker
• cervical cancer
• formalin-fixed paraffin-embedded samples (FFPE)

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MESH Headings

• Adolescent
• Adult
• Aged
• Alphapapillomavirus/genetics
• Area Under Curve
• Biopsy/methods
• Colposcopy
• DNA Methylation
• Female
• Formaldehyde
• Humans
• Microfilament Proteins/genetics
• Middle Aged
• Precancerous Conditions/genetics
• Precancerous Conditions/pathology
• Sensitivity and Specificity
• Sulfites
• Tissue Fixation
• Uterine Cervical Neoplasms/genetics
• Uterine Cervical Neoplasms/pathology
• Young Adult
• Uterine Cervical Dysplasia/genetics
• Uterine Cervical Dysplasia/pathology

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Grants

• 21070 Cancer Research UK
• 27046 Cancer Research UK
• C569/A16891 Cancer Research UK
• Cancer Research UK

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Affiliation(s)

Caroline Reuter Centre for Cancer PreventionWolfson Institute of Preventive MedicineQueen Mary University of LondonLondonUK
Matthew Preece Centre for Cancer PreventionWolfson Institute of Preventive MedicineQueen Mary University of LondonLondonUK
Rawinder Banwait Centre for Cancer PreventionWolfson Institute of Preventive MedicineQueen Mary University of LondonLondonUK
Sabrina Boer Department of UrologyRadboud University Medical CenterRadboud Institute for Molecular Life SciencesNijmegenthe Netherlands
Jack Cuzick Centre for Cancer PreventionWolfson Institute of Preventive MedicineQueen Mary University of LondonLondonUK
Attila Lorincz Centre for Cancer PreventionWolfson Institute of Preventive MedicineQueen Mary University of LondonLondonUK
Belinda Nedjai Centre for Cancer PreventionWolfson Institute of Preventive MedicineQueen Mary University of LondonLondonUK

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The Prognostic Value of Methylation Signatures and NF2 Mutations in Atypical Meningiomas

Simple Summary

The WHO 2016 classification of human meningiomas is debated due to the subjective evaluation of the histopathological diagnostics and grading. However, meningioma classification based on genome-wide DNA methylation profiling has become useful in classification of these tumors by being a better prognostic tool. The current pilot study was designed to test out genome-wide DNA methylation profiling on atypical meningiomas as these tumors have a highly variable risk of recurrence. Although we found that it had diagnostic value, further refinements on the methylation profile procedure are required. With this study we aim to motivate and impact researchers to continue to work and debate towards an improved meningioma classification including molecular and genetic biomarkers, which will benefit patients with such diagnoses.

Abstract

Background: Due to the solely subjective histopathological assessment, the WHO 2016 classification of human meningiomas is subject to interobserver variation. Consequently, the need for more reliable and objective markers are highly needed. The aim of this pilot study was to apply genome-wide DNA methylation analysis on a series of atypical meningiomas to evaluate the practical utility of this approach, examine whether prognostic subclasses are achieved and investigate whether there is an association between the methylation subclasses with poor prognosis and time to recurrence. NF1/2 mutation analyses were also performed to explore the prognostic value of such mutations in these atypical meningiomas. Methods: Twenty intracranial WHO grade II atypical meningiomas from adult patients were included. They consisted of 10 cases with recurrence (group I), and 10 cases without recurrence (group II). The formalin-fixed and paraffin-embedded tissues underwent standardized genome-wide DNA methylation analysis, and the profiles were matched with the reference library and tumor classifier from Heidelberg. NF1/2 somatic mutation analyses were performed using the CNSv1panel from Düsseldorf. Results: Eighteen out of 20 cases matched to the meningioma class using the common brain tumor classifier (v11b4). Four of these cases matched to a methylation subclass related to a prognostic subgroup based on a cut-off of 0.9. NF2 mutations were detected in 55% of cases across both groups, and the most prominent copy number alterations were chromosomal losses of 22q, 1p and 14q. No significant NF1 mutations were identified. Conclusions: Genome-wide DNA methylation profiling represents a useful tool in the diagnostics of meningiomas, however, methodological adjustments need to be addressed.

Molecular identification of pathogenic fungi in formalin-fixed and paraffin-embedded tissues

Introduction. Histopathological examination (HPE) of tissue helps in the diagnosis of invasive fungal infections (IFIs) but cannot identify the fungus to the genus/species levelGap Statement Available protocols for the molecular identification of fungi from formalin-fixed and paraffin-embedded (FFPE) tissues have limitations in terms of extraction and target selection, and standardisation.Aim. Development of sequence-based fungal identification protocol after extraction of DNA from formalin-fixed and paraffin-embedded (FFPE) tissues.Methodology. A total of 63 FFPE tissues from histopathology proven IFI cases were used to standardize the DNA extraction (commercial QIAamp kit-based extraction and conventional phenol-chloroform-isoamyl alcohol [PCI] method) and sequence-based fungal identification protocols. The PCR targeted different ribosomal DNA (rDNA) regions including complete internal transcribed spacer (ITS1-5.8S-ITS2), separate ITS1 and ITS2, 18S and D1/D2 of 28S regions. Semi-nested PCR targeting Mucorales-specific 18S rDNA region was performed in tissues having aseptate hyphae. The optimized ITS1-PCR protocol was evaluated in 119 FFPE tissues containing septate hyphae or yeast, and Mucorales-specific semi-nested PCR in 126 FFPE tissues containing aseptate hyphae.Results. The DNA yield by conventional PCI method was significantly higher (P<0.0001) than commercial kit, though the quality of DNA was similar by both protocols. The test accuracy was best while using ITS1 (61.9 %) as the target compared to 7.9, 29.9 and 22.2 % on targeting ITS1-5.8S-ITS2, ITS2, the D1/D2 region of 28S, respectively. The test accuracies of ITS1-PCR in tissues containing septate hyphae, aseptate hyphae and yeasts were 75.5, 18.7 and 100 %, respectively. The amplification (targeting ITS1 region) improved by increasing the thickness of tissue section (up to 50 µm) used for DNA extraction. ITS1-PCR protocol could amplify fungal DNA in 76 (63.8 %) tissues and Mucorales-specific semi-nested PCR in 86 (68.3 %) tissues.Conclusion. Conventional PCI-based DNA extraction from thick tissue (50 µm) may be used until optimal commercial fungal DNA extraction kit is developed. Subsequent ITS1-PCR for septate fungi and yeast, and semi-nested PCR targeting 18S rDNA for Mucorales are recommended to identify the fungus in FFPE tissues.

Differential Methylation in the GSTT1 Regulatory Region in Sudden Unexplained Death and Sudden Unexpected Death in Epilepsy

Sudden cardiac death (SCD) is a diagnostic challenge in forensic medicine. In a relatively large proportion of the SCDs, the deaths remain unexplained after autopsy. This challenge is likely caused by unknown disease mechanisms. Changes in DNA methylation have been associated with several heart diseases, but the role of DNA methylation in SCD is unknown. In this study, we investigated DNA methylation in two SCD subtypes, sudden unexplained death (SUD) and sudden unexpected death in epilepsy (SUDEP). We assessed DNA methylation of more than 850,000 positions in cardiac tissue from nine SUD and 14 SUDEP cases using the Illumina Infinium MethylationEPIC BeadChip. In total, six differently methylated regions (DMRs) between the SUD and SUDEP cases were identified. The DMRs were located in proximity to or overlapping genes encoding proteins that are a part of the glutathione S-transferase (GST) superfamily. Whole genome sequencing (WGS) showed that the DNA methylation alterations were not caused by genetic changes, while whole transcriptome sequencing (WTS) showed that DNA methylation was associated with expression levels of the GSTT1 gene. In conclusion, our results indicate that cardiac DNA methylation is similar in SUD and SUDEP, but with regional differential methylation in proximity to GST genes.

Distinct Signatures of Genomic Copy Number Variants Define Subgroups of Merkel Cell Carcinoma Tumors

Simple Summary

Cancer results from genetic changes in cells. These changes are often mutations that alter the DNA sequence of critical genes. However, duplications and deletions in cancer-related genes can also contribute to malignant transformation. In this study we use Nanostring technology to assess DNA copy number changes in samples of Merkel cell carcinoma (MCC), a rare and aggressive neuroendocrine skin tumor. We were able to identify recurrent amplifications and deletions in cancer-related genes. We also found that MCC tumors grouped into three distinct copy number variant profiles. The first group consisted of tumors with multiple deletions. The second group contained tumors with low levels of genomic structural alterations. The last group comprised tumors containing multiple amplifications. Our study suggests that most MCC tumors are associated with deletions in cancer-related genes or are lacking in copy number changes, whereas a small percentage of tumors are associated with genomic amplifications.

Abstract

Merkel cell carcinoma (MCC) is a rare, aggressive neuroendocrine skin cancer. Most MCC tumors contain integrated Merkel cell polyomavirus DNA (virus-positive MCC, VP-MCC) and carry a low somatic mutation burden whereas virus-negative MCC (VN-MCC) possess numerous ultraviolet-signature mutations. In contrast to viral oncogenes and sequence mutations, little is known about genomic structural variants in MCC. To identify copy number variants in commonly altered genes, we analyzed genomic DNA from 31 tumor samples using the Nanostring nCounter copy number cancer panel. Unsupervised clustering revealed three tumor groups with distinct genomic structural variant signatures. The first cluster was characterized by multiple recurrent deletions in genes such as RB1 and WT1. The second cluster contained eight VP-MCC and displayed very few structural variations. The final cluster contained one VP-MCC and four VN-MCC with predominantly genomic amplifications in genes like MDM4, SKP2, and KIT and deletions in TP53. Overall, VN-MCC contained more structure variation than VP-MCC but did not cluster separately from VP-MCC. The observation that most MCC tumors demonstrate a deletion-dominated structural group signature, independent of virus status, suggests a shared pathophysiology among most VP-MCC and VN-MCC tumors.

Disseminated pancreatic adenocarcinoma in an eclectus parrot (Eclectus roratus)

CASE DESCRIPTION

A 15-year-old 0.412-kg (0.906-lb) sexually intact male eclectus parrot (Eclectus roratus) was evaluated because its owners found it lethargic and dyspneic at the bottom of its cage.

CLINICAL FINDINGS

The parrot was thin and had generalized muscle wasting, diffuse feather loss, pale mucous membranes, and melena. The coelomic cavity was distended and soft on palpation, with coelomic effusion suspected. Results of a CBC indicated leukocytosis with left shift heterophilia, including toxic heterophils, lymphopenia, and anemia. Plasma biochemical analyses revealed severe hyperamylasemia.

TREATMENT AND OUTCOME

Radiography revealed no evidence of a metallic foreign body but severe loss of coelomic detail, suggestive of a coelomic mass, coelomic effusion with coelomitis, or both. Ultrasonography and CT revealed severe accumulation of coelomic fluid; a large, heterogeneous, irregularly marginated, and moderately vascularized mass in the caudal aspect of the coelomic cavity; and multiple hepatic, coelomic, and pulmonary nodules. On the basis of a poor prognosis, the parrot was euthanized. Necropsy results confirmed exocrine pancreatic adenocarcinoma, with disseminated metastases in the liver, gastrointestinal tract, coelomic cavity, and lungs.

CLINICAL RELEVANCE

In birds, pancreatic adenocarcinoma is rarely reported but should be considered a differential diagnosis for hyperamylasemia, coelomic mass, coelomic effusion, or abnormal gastrointestinal signs, alone or in combination. Ultrasonography and CT can be useful in further evaluating such patients and should be considered in the diagnostic plan.

Best practices for the extraction of genomic DNA from formalin-fixed paraffin-embedded tumor tissue for cancer genomic profiling tests

Recently, two cancer genomic profiling tests have been approved in Japan and implemented in routine clinical practice: the FDA-approved FoundationOne CDx test, and the OncoGuide NCC Oncopanel test. The quality and quantity of DNA significantly affects the sequencing results; therefore, preparing a sufficient amount of high-quality DNA for clinical cancer genomic profiling tests is important. We examined the best practices for the extraction of cancer genomic DNA from formalin-fixed paraffin-embedded (FFPE) tumor tissues of pancreatic, lung and colon cancer specimens. We found that the quality of cancer genomic DNA extracted from 10-μm-thick FFPE samples improved significantly, compared with that from 4-μm-thick FFPE samples, suggesting that 10-μm-thick FFPE samples are preferable for clinical cancer genomic profiling tests. For convenience, we created a quick reference table for calculating the required number of FFPE slides.

Core needle biopsy wash as a tool for acquiring additional diagnostic material for laboratory testing

AIMS

To determine if a simple prewash step added to the processing workflow of tissue procurement by a core needle biopsy device will recover enough cells to expand the laboratory testing armamentarium.

METHODS

Tissue was obtained from unfixed resection specimens using a core needle device and washed in a buffered solution before fixation. This creates a liquid aliquot from which dislodged cells can be kept and separated from the tissue specimen, the latter of which can then undergo traditional formalin-fixed, paraffin-embedded processing.

RESULTS

Cells dislodged from the tissue during the biopsy procedure are recoverable, are representative of the tissue section and of sufficient quantities for additional laboratory testing.

CONCLUSIONS

The core needle biopsy wash is an under-recognised and underutilised approach to extending the diagnostic capabilities of the limited amount of targeted material obtained during this common procedure. The ability to recover supplemental amounts of diagnostic material yields great potential as a substrate for a multitude of current and developing laboratory assays.

De Novo Genotypic Heterogeneity in the UL56 Region in Cytomegalovirus-Infected Tissues: Implications for Primary Letermovir Resistance

BACKGROUND

Letermovir, an inhibitor of unique long (UL)56-encoded cytomegalovirus (CMV)-terminase, shows prophylactic effects with low-grade adverse events in hematopoietic stem cell transplant recipients. Despite few case reports on acquired letermovir resistance, the frequency of de novo amino acid (A.A.) changes encoded by UL56 in CMV-infected tissues is unclear.

METHODS

We analyzed CMV UL56 sequences between the conserved region IV and variable region I in 175 formalin-fixed, paraffin-embedded tissues obtained from 147 patients showing positive CMV immunochemical staining between November 2012 and October 2016. Nucleotides 552-1330 of the open reading frame of UL56 were amplified with 5 primers and sequenced by a dideoxy fluorescence-based cycle.

RESULTS

Six (3.4%) tissues from 4 (2.7%) patients harbored A.A. substitutions. There were no known potent resistant mutations. However, we found C325Y in 2 tissues from 1 patient, along with other mutations. Four novel A.A. changes, which have not been observed in previous in vitro experiments, were identified (T244I, S301T, G312V, and M434I). Most (9 of 11, 81.8%) of the A.A. changes occurred between the codons 301 and 325 present between the conserved regions V and VI.

CONCLUSIONS

The treatment difficulties associated with letermovir resistance in a clinical setting need to be verified before its widespread use.