New insights into structural features and optimal detection of circulating tumor DNA determined by single-strand DNA analysis

Neutrophil Extracellular Traps and By-Products Play a Key Role in COVID-19: Pathogenesis, Risk Factors, and Therapy

Understanding of the pathogenesis of the coronavirus disease-2019 (COVID-19) remains incomplete, particularly in respect to the multi-organ dysfunction it may cause. We were the first to report the analogous biological and physiological features of COVID-19 pathogenesis and the harmful amplification loop between inflammation and tissue damage induced by the dysregulation of neutrophil extracellular traps (NETs) formation. Given the rapid evolution of this disease, the nature of its symptoms, and its potential lethality, we hypothesize that COVID-19 progresses under just such an amplifier loop, leading to a massive, uncontrolled inflammation process. Here, we describe in-depth the correlations of COVID-19 symptoms and biological features with those where uncontrolled NET formation is implicated in various sterile or infectious diseases. General clinical conditions, as well as numerous pathological and biological features, are analogous with NETs deleterious effects. Among NETs by-products implicated in COVID-19 pathogenesis, one of the most significant appears to be elastase, in accelerating virus entry and inducing hypertension, thrombosis and vasculitis. We postulate that severe acute respiratory syndrome-coronavirus 2 (SARS-CoV2) may evade innate immune response, causing uncontrolled NETs formation and multi-organ failure. In addition, we point to indicators that NETS-associated diseases are COVID-19 risk factors. Acknowledging that neutrophils are the principal origin of extracellular and circulating DNA release, we nonetheless, explain why targeting NETs rather than neutrophils themselves may in practice be a better strategy. This paper also offers an in-depth review of NET formation, function and pathogenic dysregulation, as well as of current and prospective future therapies to control NETopathies. As such, it enables us also to suggest new therapeutic strategies to fight COVID-19. In combination with or independent of the latest tested approaches, we propose the evaluation, in the short term, of treatments with DNase-1, with the anti-diabetic Metformin, or with drugs targeting elastase (i.e., Silvelestat). With a longer perspective, we also advocate a significant increase in research on the development of toll-like receptors (TLR) and C-type lectin-like receptors (CLEC) inhibitors, NET-inhibitory peptides, and on anti-IL-26 therapies.

Machine Learning-Assisted Evaluation of Circulating DNA Quantitative Analysis for Cancer Screening

While the utility of circulating cell-free DNA (cfDNA) in cancer screening and early detection have recently been investigated by testing genetic and epigenetic alterations, here, an original approach by examining cfDNA quantitative and structural features is developed. First, the potential of cfDNA quantitative and structural parameters is independently demonstrated in cell culture, murine, and human plasma models. Subsequently, these variables are evaluated in a large retrospective cohort of 289 healthy individuals and 983 patients with various cancer types; after age resampling, this evaluation is done independently and the variables are combined using a machine learning approach. Implementation of a decision tree prediction model for the detection and classification of healthy and cancer patients shows unprecedented performance for 0, I, and II colorectal cancer stages (specificity, 0.89 and sensitivity, 0.72). Consequently, the methodological proof of concept of using both quantitative and structural biomarkers, and classification with a machine learning method are highlighted, as an efficient strategy for cancer screening. It is foreseen that the classification rate may even be improved by the addition of such biomarkers to fragmentomics, methylation, or the detection of genetic alterations. The optimization of such a multianalyte strategy with this machine learning method is therefore warranted.

Liquid biopsy with cell free DNA: new horizons for prostate cancer

Although prostate cancer (PCa) is one of the most common tumors in European males, the only minimally invasive diagnostic tool in PCa setup is the determination of PSA in serum. Cell-free DNA (cfDNA) has been demonstrated to be helpful for PCa diagnosis but has not yet been integrated into the clinical setting. This review aims to provide a systematic update of cfDNA and its fragmentation patterns in PCa reported in literature published over the last twenty years. Due to the high variability of the scientific methods adopted and a lack of standardized median cfDNA levels, results fluctuate across different studies. These differences may be due to the cfDNA source, the quantification method, or the fragmentation pattern. Blood plasma is the most frequently analyzed biological fluid, but seminal plasma has been reported to contain higher cfDNA concentration due to its vicinity to the tumor origin. CfDNA has been shown to be composed of single-stranded (ssDNA) and double-stranded DNA (dsDNA), so the total cfDNA concentration should be preferred as it corresponds best to the tumor mass. Fluorometry and capillary electrophoresis (CE) may be quick and cost-effective tools for cfDNA assessment in a clinical setting. The greatest future challenge is the elaboration of common guidelines and standardized procedures for diagnostic laboratories performing cfDNA analysis. A multiparametric approach combining the analysis of total cfDNA (both ssDNA and dsDNA), cfDNA fragment length, and specific genetic mutations (ctDNA assessment) is required for optimal future applications of liquid biopsy.

Evaluating the quantity, quality and size distribution of cell-free DNA by multiplex droplet digital PCR

Cell-free DNA (cfDNA) has become a comprehensive biomarker in the fields of non-invasive cancer detection and monitoring, organ transplantation, prenatal genetic testing and pathogen detection. While cfDNA samples can be obtained using a broad variety of approaches, there is an urgent need to standardize analytical tools aimed at assessing its basic properties. Typical methods to determine the yield and fragment size distribution of cfDNA samples are usually either blind to genomic DNA contamination or the presence of enzymatic inhibitors, which can confound and undermine downstream analyses. Here, we present a novel droplet digital PCR assay to identify suboptimal samples and aberrant cfDNA size distributions, the latter typically associated with high levels of circulating tumour DNA (ctDNA). Our assay was designed to promiscuously cross-amplify members of the human olfactory receptor (OR) gene family and includes a customizable diploid locus for the determination of absolute cfDNA concentrations. We demonstrate here the utility of our assay to estimate the yield and quality of cfDNA extracts and deduce fragment size distributions that correlate well with those inferred by capillary electrophoresis and high throughput sequencing. The assay described herein is a powerful tool to establish quality controls and stratify cfDNA samples based on presumed ctDNA levels, then facilitating the implementation of robust, cost-effective and standardized analytical workflows into clinical practice.

Comparison of Circulating Cell-Free DNA Extraction Methods for Downstream Analysis in Cancer Patients

Circulating cell-free DNA (ccfDNA) may contain DNA originating from the tumor in plasma of cancer patients (ctDNA) and enables noninvasive cancer diagnosis, treatment predictive testing, and response monitoring. A recent multicenter evaluation of workflows by the CANCER-ID consortium using artificial spiked-in plasma showed significant differences and consequently the importance of carefully selecting ccfDNA extraction methods. Here, the quantity and integrity of extracted ccfDNA from the plasma of cancer patients were assessed. Twenty-one cancer patient-derived cell-free plasma samples were selected to compare the Qiagen CNA, Maxwell RSC ccfDNA plasma, and Zymo manual quick ccfDNA kit. High-volume citrate plasma samples collected by diagnostic leukapheresis from six cancer patients were used to compare the Qiagen CNA (2 mL) and QIAamp MinElute ccfDNA kit (8 mL). This study revealed similar integrity and similar levels of amplified short-sized fragments and tumor-specific mutants comparing the CNA and RSC kits. However, the CNA kit consistently showed the highest yield of ccfDNA and short-sized fragments, while the RSC and ME kits showed higher variant allelic frequencies (VAFs). Our study pinpoints the importance of standardizing preanalytical conditions as well as consensus on defining the input of ccfDNA to accurately detect ctDNA and be able to compare results in a clinical routine practice, within and between clinical studies.

Comparison of methods for the isolation of cell-free DNA from cell culture supernatant

In vitro characterization of cell-free DNA using two-dimensional cell culture models is emerging as an important step toward an improved understanding of the physical and biological characteristics of cell-free DNA in human biology. However, precise measurement of the cell-free DNA in cell culture medium is highly dependent on the efficacy of the method used for DNA purification, and is often a juncture of experimental confusion. Therefore, in this study, we compared six commercially available cell-free DNA isolation kits for the recovery of cell-free DNA from the cell culture supernatant of a human bone cancer cell line (143B), including two magnetic bead-based manual kits, one automated magnetic bead-based extraction method, and three manual spin-column kits. Based on cell-free DNA quantitation and sizing, using the Qubit dsDNA HS assay and Bioanalyzer HS DNA assay, respectively, the different methods showed significant variability concerning recovery, reproducibility, and size discrimination. These findings highlight the importance of selecting a cell-free DNA extraction method that is appropriate for the aims of a study. For example, mutational analysis of cell-free DNA may be enhanced by a method that favors a high yield or is biased toward the isolation of short cell-free DNA fragments. In contrast, quantitative analysis of cell-free DNA in a comparative setting (e.g. measuring the fluctuation of cell-free DNA levels over time) may require the selection of a cell-free DNA isolation method that forgoes a high recovery for high reproducibility and minimal size bias.

Tumor microenvironment complexity and therapeutic implications at a glance

The dynamic interactions of cancer cells with their microenvironment consisting of stromal cells (cellular part) and extracellular matrix (ECM) components (non-cellular) is essential to stimulate the heterogeneity of cancer cell, clonal evolution and to increase the multidrug resistance ending in cancer cell progression and metastasis. The reciprocal cell-cell/ECM interaction and tumor cell hijacking of non-malignant cells force stromal cells to lose their function and acquire new phenotypes that promote development and invasion of tumor cells. Understanding the underlying cellular and molecular mechanisms governing these interactions can be used as a novel strategy to indirectly disrupt cancer cell interplay and contribute to the development of efficient and safe therapeutic strategies to fight cancer. Furthermore, the tumor-derived circulating materials can also be used as cancer diagnostic tools to precisely predict and monitor the outcome of therapy. This review evaluates such potentials in various advanced cancer models, with a focus on 3D systems as well as lab-on-chip devices. Video abstract.

Recent advances in circulating nucleic acids in oncology

Circulating cell-free DNA (cfDNA) is one of the fastest growing and most exciting areas in oncology in recent years. Its potential clinical uses cover now each phase of cancer patient management care (predictive information, detection of the minimal residual disease, early detection of resistance, treatment monitoring, recurrence surveillance, and cancer early detection/screening). This review relates the recent advances in the application of circulating DNA or RNA in oncology building on unpublished or initial findings/work presented at the 10th international symposium on circulating nucleic acids in plasma and serum held in Montpellier from the 20th to the 22nd of September 2017. This year, presenters revealed their latest data and crucial observations notably in relation to (i) the circulating cell-free (cfDNA) structure and implications regarding their optimal detection; (ii) their role in the metastatic or immunological processes; (iii) evaluation of miRNA panels for cancer patient follow up; (iv) the detection of the minimal residual disease; (v) the evaluation of a screening tests for cancer using cfDNA analysis; and (vi) elements of preanalytical guidelines. This work reviews the recent progresses in the field brought to light in the meeting, as well as in the most important reports from the literature, past and present. It proposes a broader picture of the basic research and its potential, and of the implementation and current challenges in the use of circulating nucleic acids in oncology.

Hypoxia differently modulates the release of mitochondrial and nuclear DNA

BACKGROUND

We investigated the influence of hypoxia on the concentration of mitochondrial and nuclear cell-free DNA (McfDNA and NcfDNA, respectively).

METHOD

By an ultra-sensitive quantitative PCR-based assay, McfDNA and NcfDNA were measured in the supernatants of different colorectal cell lines, and in the plasma of C57/Bl6 mice engrafted with TC1 tumour cells, in normoxic or hypoxic conditions.

RESULTS

Our data when setting cell culture conditions highlighted the higher stability of McfDNA as compared to NcfDNA and revealed that cancer cells released amounts of nuclear DNA equivalent to the mass of a chromosome over a 6-h duration of incubation. In cell model, hypoxia induced a great increase in NcfDNA and McfDNA concentrations within the first 24 h. After this period, cfDNA total concentrations remained stable in hypoxia consecutive to a decrease of nuclear DNA release, and noteworthy, to a complete inhibition of daily mitochondrial DNA release. In TC1-engrafted mice submitted to intermittent hypoxia, plasma NcfDNA levels are much higher than in mice bred in normoxia, unlike plasma McfDNA concentration that is not impacted by hypoxia.

CONCLUSION

This study suggests that hypoxia negatively modulates nuclear and, particularly, mitochondrial DNA releases in long-term hypoxia, and revealed that the underlying mechanisms are differently regulated.

Blood contains circulating cell-free respiratory competent mitochondria

Mitochondria are considered as the power-generating units of the cell due to their key role in energy metabolism and cell signaling. However, mitochondrial components could be found in the extracellular space, as fragments or encapsulated in vesicles. In addition, this intact organelle has been recently reported to be released by platelets exclusively in specific conditions. Here, we demonstrate for the first time, that blood preparation with resting platelets, contains whole functional mitochondria in normal physiological state. Likewise, we show, that normal and tumor cultured cells are able to secrete their mitochondria. Using serial centrifugation or filtration followed by polymerase chain reaction-based methods, and Whole Genome Sequencing, we detect extracellular full-length mitochondrial DNA in particles over 0.22 µm holding specific mitochondrial membrane proteins. We identify these particles as intact cell-free mitochondria using fluorescence-activated cell sorting analysis, fluorescence microscopy, and transmission electron microscopy. Oxygen consumption analysis revealed that these mitochondria are respiratory competent. In view of previously described mitochondrial potential in intercellular transfer, this discovery could greatly widen the scope of cell-cell communication biology. Further steps should be developed to investigate the potential role of mitochondria as a signaling organelle outside the cell and to determine whether these circulating units could be relevant for early detection and prognosis of various diseases.

Size profile of cell-free DNA: A beacon guiding the practice and innovation of clinical testing

Cell-free DNA (cfDNA) has pioneered the development of noninvasive prenatal testing and liquid biopsy, its emerging applications include organ transplantation, autoimmune diseases, and many other disorders; size profile of cfDNA is a crucial biological property and is essential for its clinical applications. Therefore, a thorough mastery of the characteristic and potential applications of cfDNA size profile is needed. Methods: Based on the recent researches, we summarized the size profile of cfDNA in pregnant women, tumor patients, transplant recipients and systemic lupus erythematosus (SLE) patients to explore the common features. We also concluded the applications of size profile in pre-analytical phases, analytical phases for novel assays, and preparation of quality control materials (QCMs). Results: The size profile of cfDNA shared common features in different populations, and was distributed as a "ladder" pattern with a dominant peak at ~166 bp. However, cfDNA entailed slightly discrepant characteristics due to specific tissues of origin. The dominant peaks of fetal and maternal cfDNA fragments in pregnant women were at 143 bp and 166 bp, respectively. The plasma cfDNA in tumor patients, transplant recipients, and SLE patients had a peak of around 166 bp. In pre-analytical phases, size profile served as a vital indicator to judge the eligibility of specimens, thus ensuring the successful implementation of assays. More importantly, the size profile had the potential to enrich short fragments, calculate fetal fraction, detect fetal abnormalities, predict tumor progress in analytical phase and to guide the preparation of QCMs. Conclusions: Our finding summarized the characteristics and potential applications of cfDNA size profile, providing clinical researchers with novel assays by the extensive application of cfDNA.

A ligation-based single-stranded library preparation method to analyze cell-free DNA and synthetic oligos

Background

Cell-free DNA (cfDNA), present in circulating blood plasma, contains information about prenatal health, organ transplant reception, and cancer presence and progression. Originally developed for the genomic analysis of highly degraded ancient DNA, single-stranded DNA (ssDNA) library preparation methods are gaining popularity in the field of cfDNA analysis due to their efficiency and ability to convert short, fragmented DNA into sequencing libraries without altering DNA ends. However, current ssDNA methods are costly and time-consuming.

Results

Here we present an efficient ligation-based single-stranded library preparation method that is engineered to produce complex libraries in under 2.5 h from as little as 1 nanogram of input DNA without alteration to the native ends of template molecules. Our method, called Single Reaction Single-stranded LibrarY or SRSLY, ligates uniquely designed Next-Generation Sequencing (NGS) adapters in a one-step combined phosphorylation/ligation reaction that foregoes end-polishing. Using synthetic DNA oligos and cfDNA, we demonstrate the efficiency and utility of this approach and compare with existing double-stranded and single-stranded approaches for library generation. Finally, we demonstrate that cfDNA NGS data generated from SRSLY can be used to analyze DNA fragmentation patterns to deduce nucleosome positioning and transcription factor binding.

Conclusions

SRSLY is a versatile tool for converting short and fragmented DNA molecules, like cfDNA fragments, into sequencing libraries while retaining native lengths and ends.

Early detection of cancer using circulating tumor DNA: biological, physiological and analytical considerations

Early diagnosis of cancer improves the efficacy of curative therapies. However, due to the difficulties involved in distinguishing between small early-stage tumors and normal biological variation, early detection of cancer is an extremely challenging task and there are currently no clinically validated biomarkers for a pan-cancer screening test. It is thus of particular significance that increasing evidence indicates the potential of circulating tumor DNA (ctDNA) molecules, which are fragmented segments of DNA shed from tumor cells into adjacent body fluids and the circulatory system, to serve as molecular markers for early cancer detection and thereby allow early intervention and improvement of therapeutic and survival outcomes. This is possible because ctDNA molecules bear cancer-specific fragmentation patterns, nucleosome depletion motifs, and genetic and epigenetic alterations, as distinct from plasma DNA originating from non-cancerous tissues/cells. Compared to traditional biomarkers, ctDNA analysis therefore presents the distinctive advantage of detecting tumor-specific alterations. However, based on a thorough survey of the literature, theoretical and empirical evidence suggests that current ctDNA analysis strategies, which are mainly based on DNA mutation detection, do not demonstrate the necessary diagnostic sensitivity and specificity that is required for broad clinical implementation in a screening context. Therefore, in this review we explain the biological, physiological, and analytical challenges toward the development of clinically meaningful ctDNA tests. In addition, we explore some approaches that can be implemented in order to increase the sensitivity and specificity of ctDNA assays.

The size of cell-free mitochondrial DNA in blood is inversely correlated with tumor burden in cancer patients

Circulating cell-free DNAs (cfDNAs) are fragmented DNA molecules released into the blood by cells. Previous studies have suggested that mitochondria-originated cfDNA fragments (mt-cfDNAs) in cancer patients are more fragmented than those from healthy controls. However, it is still unknown where these short mt-cfDNAs originate, and whether the length of mt-cfDNAs can be correlated with tumor burden and cancer progression. In this study, we first performed whole-genome sequencing analysis (WGS) of cfDNAs from a human tumor cell line-xenotransplantation mouse model and found that mt-cfDNAs released from transplanted tumor cells were shorter than the mouse counterpart. We next analyzed blood cfDNA samples from hepatocellular carcinoma and prostate cancer patients and found that mt-cfDNA lengths were inversely related to tumor size as well as the concentration of circulating tumor DNA. Our study suggested that monitoring the size of mt-cfDNAs in cancer patients would be a useful way to estimate tumor burden and cancer progression.

Quick assessment of cell-free DNA in seminal fluid and fragment size for early non-invasive prostate cancer diagnosis

BACKGROUND

Liquid biopsy consists in the quantification and qualification of circulating cell-free DNA (cfDNA) and tumor-derived DNA (ctDNA) for cancer recognition. Recently, the characterization of seminal cfDNA (scfDNA) has been reported as a possible biomarker for prostate cancer (PCa) diagnosis.

METHODS

Thirty patients with histologically proven PCa, 33 with benign prostate hyperplasia (BPH) and 21 healthy controls were enrolled. cfDNA was extracted from seminal fluid samples. cfDNA quantification and analysis were performed using Qubit ssDNA Kit and Agilent 2100 Bioanalyzer. Statistical analysis included: Levene's test, Shapiro-Wilk, Kolmogorov-Smirnov and Kruskal Wallis tests.

RESULTS

Median cfDNA was significantly higher in PCa patients 428.45 ng/mL (173.93-1159.62) compared to BPH patients 77.4 ng/mL (18.23-501) and healthy controls 25.4 ng/mL (15.37-76.62). scfDNA fragments longer than 1000 base-pairs were more common in patients with PCa compared to those with BPH and controls.

CONCLUSIONS

scfDNA concentration and fragment size differed significantly in the three groups of PCa, BPH and healthy controls. Both parameters are potential clinical biomarkers for PCa and can be used in both early diagnosis and follow-up. Using automated systems for high-throughput cfDNA quantification could improve the reproducibility of the method and facilitate the implementation of liquid biopsies in the clinical setting.

Genome-wide cell-free DNA fragmentation in patients with cancer

Cell-free DNA in the blood provides a non-invasive diagnostic avenue for patients with cancer1. However, characteristics of the origins and molecular features of cell-free DNA are poorly understood. Here we developed an approach to evaluate fragmentation patterns of cell-free DNA across the genome, and found that profiles of healthy individuals reflected nucleosomal patterns of white blood cells, whereas patients with cancer had altered fragmentation profiles. We used this method to analyse the fragmentation profiles of 236 patients with breast, colorectal, lung, ovarian, pancreatic, gastric or bile duct cancer and 245 healthy individuals. A machine learning model that incorporated genome-wide fragmentation features had sensitivities of detection ranging from 57% to more than 99% among the seven cancer types at 98% specificity, with an overall area under the curve value of 0.94. Fragmentation profiles could be used to identify the tissue of origin of the cancers to a limited number of sites in 75% of cases. Combining our approach with mutation-based cell-free DNA analyses detected 91% of patients with cancer. The results of these analyses highlight important properties of cell-free DNA and provide a proof-of-principle approach for the screening, early detection and monitoring of human cancer.

Guidelines for the Preanalytical Conditions for Analyzing Circulating Cell-Free DNA

Circulating cell-free DNA (cfDNA) isolated from blood has been identified as a potential biomarker in numerous fields, and has been the object of intensive research over the past decade, although its original discovery dates back 60 years. While it is already used routinely in commercial and clinical practice in oncology and prenatal testing, other potential applications have emerged, including for diabetes, cardiovascular diseases, organ transplantation, autoimmune diseases, sepsis, trauma, and sport management. As with the discovery and development of any biomarker, preanalytical requirements and documentation are as important as analytical requirements. Except for the case of noninvasive prenatal testing and prenatal diagnosis, the implementation of cfDNA in a clinical setting remains limited because of the lack of standardization of cfDNA analysis. In particular, only a few attempts have been made to collect and pool scientific data on the relevant preanalytical factors, and no standard operating procedure has yet been set. For this report, we have performed a thorough and systematic search via MEDLINE® for relevant preanalytical variables and patient factors. These form the basis of the guidelines we propose for analyzing nuclear cfDNA.

Quantifying circulating cell-free DNA in humans

To our knowledge, this is the first comprehensive study on the influence of several pre-analytical and demographic parameters that could be a source of variability in the quantification of nuclear and mitochondrial circulating DNA (NcirDNA and McirDNA). We report data from a total of 222 subjects, 104 healthy individuals and 118 metastatic colorectal cancer (mCRC) patients. Approximately 50,000 and 3,000-fold more mitochondrial than nuclear genome copies were found in the plasma of healthy individuals and mCRC patients, respectively. In healthy individuals, NcirDNA concentration was statistically influenced by age (p = 0.009) and gender (p = 0.048). Multivariate analysis with logistic regression specified that age over 47 years-old was predictive to have higher NcirDNA concentration (OR = 2.41; p = 0.033). McirDNA concentration was independent of age and gender in healthy individuals. In mCRC patients, NcirDNA and McirDNA levels were independent of age, gender, delay between food intake and blood collection, and plasma aspect, either with univariate or multivariate analysis. Nonetheless, ad hoc study suggested that menopause and blood collection time might have tendency to influence cirDNA quantification. In addition, high significant statistical differences were found between mCRC patients and healthy individuals for NcirDNA (p < 0.0001), McirDNA (p < 0.0001) and McirDNA/NcirDNA ratio (p < 0.0001). NcirDNA and McirDNA levels do not vary in the same way with regards to cancer vs healthy status, pre-analytical and demographic factors.