High-resolution profiling of fetal DNA clearance from maternal plasma by massively parallel sequencing

Molecular characterization and functional roles of circulating cell-free extrachromosomal circular DNA

Circular DNA segments isolated from chromosomes are known as extrachromosomal circular DNA (eccDNA). Its distinct structure and characteristics, along with the variations observed in different disease states, makes it a promising biomarker. Recent studies have revealed the presence of eccDNAs in body fluids, indicating their involvement in various biological functions. This finding opens up avenues for utilizing eccDNAs as convenient and real-time biomarkers for disease diagnosis, treatment monitoring, and prognosis assessment through noninvasive analysis of body fluids. In this comprehensive review, we focused on elucidating the size profiles, potential mechanisms of formation and clearance, detection methods, and potential clinical applications of eccDNAs. We aimed to provide a valuable reference resource for future research in this field.

Circulating cell-free DNA-based methylation pattern in plasma for early diagnosis of esophagus cancer

With the increased awareness of early tumor detection, the importance of detecting and diagnosing esophageal cancer in its early stages has been underscored. Studies have consistently demonstrated the crucial role of methylation levels in circulating cell-free DNA (cfDNA) in identifying and diagnosing early-stage cancer. cfDNA methylation pertains to the methylation state within the genomic scope of cfDNA and is strongly associated with cancer development and progression. Several research teams have delved into the potential application of cfDNA methylation in identifying early-stage esophageal cancer and have achieved promising outcomes. Recent research supports the high sensitivity and specificity of cfDNA methylation in early esophageal cancer diagnosis, providing a more accurate and efficient approach for early detection and improved clinical management. Accordingly, this review aims to present an overview of methylation-based cfDNA research with a focus on the latest developments in the early detection of esophageal cancer. Additionally, this review summarizes advanced analytical technologies for cfDNA methylation that have significantly benefited from recent advancements in separation and detection techniques, such as methylated DNA immunoprecipitation sequencing (MeDIP-seq). Recent findings suggest that biomarkers based on cfDNA methylation may soon find successful applications in the early detection of esophageal cancer. However, large-scale prospective clinical trials are required to identify the potential of these biomarkers.

Modeling early treatment response in AML from cell-free tumor DNA

Monitoring disease response after intensive chemotherapy for acute myeloid leukemia (AML) currently requires invasive bone marrow biopsies, imposing a significant burden on patients. In contrast, cell-free tumor DNA (ctDNA) in peripheral blood, carrying tumor-specific mutations, offers a less-invasive assessment of residual disease. However, the relationship between ctDNA levels and bone marrow blast kinetics remains unclear. We explored this in 10 AML patients with NPM1 and IDH2 mutations undergoing initial chemotherapy. Comparison of mathematical mixed-effect models showed that (1) inclusion of blast cell death in the bone marrow, (2) transition of ctDNA to peripheral blood, and (3) ctDNA decay in peripheral blood describes kinetics of blast cells and ctDNA best. The fitted model allows prediction of residual bone marrow blast content from ctDNA, and its scaling factor, representing clonal heterogeneity, correlates with relapse risk. Our study provides precise insights into blast and ctDNA kinetics, offering novel avenues for AML disease monitoring.

Short report: Plasma based biomarkers detect radiation induced brain injury in cancer patients treated for brain metastasis: A pilot study

BACKGROUND

Radiotherapy has an important role in the treatment of brain metastases but carries risk of short and/or long-term toxicity, termed radiation-induced brain injury (RBI). As the diagnosis of RBI is crucial for correct patient management, there is an unmet need for reliable biomarkers for RBI. The aim of this proof-of concept study is to determine the utility of brain-derived circulating free DNA (BncfDNA), identified by specific methylation patterns for neurons, astrocytes, and oligodendrocytes, as biomarkers brain injury induced by radiotherapy.

METHODS

Twenty-four patients with brain metastases were monitored clinically and radiologically before, during and after brain radiotherapy, and blood for BncfDNA analysis (98 samples) was concurrently collected. Sixteen patients were treated with whole brain radiotherapy and eight patients with stereotactic radiosurgery.

RESULTS

During follow-up nine RBI events were detected, and all correlated with significant increase in BncfDNA levels compared to baseline. Additionally, resolution of RBI correlated with a decrease in BncfDNA. Changes in BncfDNA were independent of tumor response.

CONCLUSIONS

Elevated BncfDNA levels reflects brain cell injury incurred by radiotherapy. further research is needed to establish BncfDNA as a novel plasma-based biomarker for brain injury induced by radiotherapy.

Microbial cell-free DNA detection: Minimally invasive diagnosis of infectious diseases

BACKGROUND

Detection of infectious diseases, especially among immunocompromised and patients on prolonged anti-microbial treatment, remains challenging, limited by conventional techniques with low sensitivity and long-turnaround time. Molecular detection by polymerase chain reaction (PCR) also has limited utility as it requires a targeted approach with prior suspicion of the infecting organism. Advancements in sequencing methodologies, specifically next-generation sequencing (NGS), have presented a promising opportunity to identify pathogens in cases where conventional techniques may be inadequate. However, the direct application of these techniques for diagnosing invasive infections is still limited by the need for invasive sampling, highlighting the pressing need to develop and implement non-invasive or minimally invasive approaches to improve the diagnosis of invasive infections.

OBJECTIVES

The objectives of this article are to explore the notable features, clinical utility, and constraints associated with the detection of microbial circulating cell-free DNA (mcfDNA) as a minimally invasive diagnostic tool for infectious diseases.

CONTENT

The mcfDNA detection provides an opportunity to identify micro-organisms in the blood of a patient. It is especially beneficial in immunocompromised patients where invasive sampling is not possible or where repeated cultures are negative. This review will discuss the applications and constraints of detecting mcfDNA for diagnosing infections and the various platforms available for its detection.

Bladder cancer

Bladder cancer is a global health issue with sex differences in incidence and prognosis. Bladder cancer has distinct molecular subtypes with multiple pathogenic pathways depending on whether the disease is non-muscle invasive or muscle invasive. The mutational burden is higher in muscle-invasive than in non-muscle-invasive disease. Commonly mutated genes include TERT, FGFR3, TP53, PIK3CA, STAG2 and genes involved in chromatin modification. Subtyping of both forms of bladder cancer is likely to change considerably with the advent of single-cell analysis methods. Early detection signifies a better disease prognosis; thus, minimally invasive diagnostic options are needed to improve patient outcomes. Urine-based tests are available for disease diagnosis and surveillance, and analysis of blood-based cell-free DNA is a promising tool for the detection of minimal residual disease and metastatic relapse. Transurethral resection is the cornerstone treatment for non-muscle-invasive bladder cancer and intravesical therapy can further improve oncological outcomes. For muscle-invasive bladder cancer, radical cystectomy with neoadjuvant chemotherapy is the standard of care with evidence supporting trimodality therapy. Immune-checkpoint inhibitors have demonstrated benefit in non-muscle-invasive, muscle-invasive and metastatic bladder cancer. Effective management requires a multidisciplinary approach that considers patient characteristics and molecular disease characteristics.

[Towards a generalization of non-invasive prenatal diagnosis of single-gene disorders? Assesment and outlook]

OBJECTIVES

The screening of fetal aneuploidies and non-invasive prenatal diagnosis of monogenic diseases (NIPD-MD) both rely on the study of free fetal DNA in maternal circulation, but their respective rise was unequal. Development of NIPD-MD has taken longer as it represents a less attractive commercial dynamic for industry, but also because it usually involves the development of tailored tests specific to each pathogenic variant.

METHODS

We have carried out a review of the literature on the various indications and technologies involved in the use of NIPD-MM. We present its current implementation and its development in France.

RESULTS

To date, NIPD-MD has been routinely offered in France for several years by the laboratories of the French NIPD-MD network but remains mostly limited to the exclusion of paternal or de novo variants, the exclusion DPNI-MD. Indeed, it is still difficult to study the transmission of maternal variants from circulating free DNA analysis, due to its biological complexity: coexistence and predominance of similar DNA sequences of maternal origin. Different strategies, either direct or indirect, are being evaluated to establish fetal status regardless of the parental origin of the disease or its transmission mode. The emergence of commercial screening solutions for monogenic diseases complements the arsenal of prenatal exploration tools for these diseases.

CONCLUSION

The multitude of existing technologies and protocols may complicate the information provided during antenatal consultations, but mastery of know-how and knowledge of ethical issues of NIPD-MD will ensure optimal service and better management of pregnancies at risk of transmitting monogenic disease.

CTC, ctDNA, and Exosome in Thyroid Cancers: A Review

Thyroid cancer has become more common in recent years all around the world. Many issues still need to be urgently addressed in the diagnosis, treatment, and prognosis of thyroid cancer. Liquid biopsy (mainly circulating tumor DNA (ctDNA), circulating tumor cells (CTCs), and circulating exosomes) may provide a novel and ideal approach to solve these issues, allows us to assess the features of diseases more comprehensively, and has a function in a variety of malignancies. Recently, liquid biopsy has been shown to be critical in thyroid cancer diagnosis, treatment, and prognosis in numerous previous studies. In this review, by testing CTCs, ctDNA, and exosomes, we focus on the possible clinical role of liquid biopsy in thyroid cancer, including diagnostic and prognostic biomarkers and response to therapy. We briefly review how liquid biopsy components have progressed in thyroid cancer by consulting the existing public information. We also discuss the clinical potential of liquid biopsy in thyroid cancer and provide a reference for liquid biopsy research. Liquid biopsy has the potential to be a useful tool in the early detection, monitoring, or prediction of response to therapies and prognosis in thyroid cancer, with promising clinical applications.

Incidental Detection of Malignancies With Cell-Free DNA Screening

Cell-free circulating DNA is an evolving technology with important clinical applications in both obstetric care and oncology. In the challenging patient with pregnancy and co-existing malignancy, the utility of cell-free DNA both for aneuploidy screening and cancer identification is an area of active research. Understanding the physiology associated with circulating cell-free DNA and subsequent laboratory evaluation is critical for clinicians caring for the obstetric patient with cell-free fetal DNA screening results suggestive of malignancy. Ongoing research is necessary to determine best practices for the evaluation and management of these patients with promising applications in the advancement of precision medicine.

Donor-derived cell free DNA as a biomarker in kidney transplantation

The early detection of acute rejection in the allograft is important as it provides an opportunity for timely therapeutic intervention in order to preserve graft function and achieve longer graft survival. Donor-derived cell-free DNA (dd-cfDNA) has emerged as a new biomarker in the field of kidney transplantation. In this review, we used data from various studies to examine the role of dd-cfDNA in comparison to creatinine and donor-specific antibodies in the early detection of transplant rejection. We also reviewed the use of dd-cfDNA in other organ transplants as well as the challenges and potential future direction for dd-cfDNA as a diagnostic tool.

Blood has never been thicker: Cell-free DNA fragmentomics in the liquid biopsy toolbox of B-cell lymphomas

Liquid biopsies utilizing plasma circulating tumor DNA (ctDNA) are anticipated to revolutionize decision-making in cancer care. In the field of lymphomas, ctDNA-based blood tests represent the forefront of clinically applicable tools to harness decades of genomic research for disease profiling, quantification, and detection. More recently, the discovery of nonrandom fragmentation patterns in cell-free DNA (cfDNA) has opened another avenue of liquid biopsy research beyond mutational interrogation of ctDNA. Through examination of structural features, nucleotide content, and genomic distribution of massive numbers of plasma cfDNA molecules, the study of fragmentomics aims at identifying new tools that augment existing ctDNA-based analyses and discover new ways to profile cancer from blood tests. Indeed, the characterization of aberrant lymphoma ctDNA fragment patterns and harnessing them with powerful machine-learning techniques are expected to unleash the potential of nonmutant molecules for liquid biopsy purposes. In this article, we review cfDNA fragmentomics as an emerging approach in the ctDNA research of B-cell lymphomas. We summarize the biology behind the formation of cfDNA fragment patterns and discuss the preanalytical and technical limitations faced with current methodologies. Then we go through the advances in the field of lymphomas and envision what other noninvasive tools based on fragment characteristics could be explored. Last, we place fragmentomics as one of the facets of ctDNA analyses in emerging multiview and multiomics liquid biopsies. We pay attention to the unknowns in the field of cfDNA fragmentation biology that warrant further mechanistic investigation to provide rational background for the development of these precision oncology tools and understanding of their limitations.

Bacterial DNA metabolism analysis by metagenomic next-generation sequencing (mNGS) after treatment of bloodstream infection

BACKGROUND

With the advent of metagenomic next-generation sequencing (mNGS), the time of DNA metabolism can be explored after bacteria be killed. In this study, we applied mNGS in investigation of the clearance profile of circulating bacteria DNA.

METHODS

All of the rabbits were injected with the inactivated Escherichia coli. Using mNGS, we analyzed serial samples of plasma collected from rabbits to detect clearance profile of circulating E. coli DNA.

RESULTS

In this study, we found that the of E. coli DNA could still be detected 6 h after injecting killed bacteria. The clearance half-lives associated with the 2 phases are 0.37 and 1.81 h. We also explored there is no correlation between the disease severity with the E. coli DNA reads in circulation.

CONCLUSIONS

After the bacteria were completely killed, their DNA could still be detected in the blood circulation. The metabolism of bacterial DNA in the circulation had two phases: fast and slow phases, and there were no correlations between the level of bacteria reads with the severity of patients' disease after the bacteria have been completely killed.

Potential non-invasive biomarkers in tumor immune checkpoint inhibitor therapy: response and prognosis prediction

Immune checkpoint inhibitors (ICIs) have dramatically enhanced the treatment outcomes for diverse malignancies. Yet, only 15-60% of patients respond significantly. Therefore, accurate responder identification and timely ICI administration are critical issues in tumor ICI therapy. Recent rapid developments at the intersection of oncology, immunology, biology, and computer science have provided an abundance of predictive biomarkers for ICI efficacy. These biomarkers can be invasive or non-invasive, depending on the specific sample collection method. Compared with invasive markers, a host of non-invasive markers have been confirmed to have superior availability and accuracy in ICI efficacy prediction. Considering the outstanding advantages of dynamic monitoring of the immunotherapy response and the potential for widespread clinical application, we review the recent research in this field with the aim of contributing to the identification of patients who may derive the greatest benefit from ICI therapy.

Circulating Cell-Free DNAs as a Biomarker and Therapeutic Target for Acetaminophen-Induced Liver Injury

Acetaminophen (APAP) overdose is a leading cause of drug-induced liver injury and acute liver failure, while the detection, prognosis prediction, and therapy for APAP-induced liver injury (AILI) remain improved. Here, it is determined that the temporal pattern of circulating cell-free DNA (cfDNA) is strongly associated with damage and inflammation parameters in AILI. CfDNA is comparable to alanine aminotransferase (ALT) in predicting mortality and outperformed ALT when combined with ALT in AILI. The depletion of cfDNA or neutrophils alleviates liver damage, while the addition of cfDNA or adoptive transfer of neutrophils exacerbates the damage. The combination of DNase I and N-acetylcysteine attenuates AILI significantly. This study establishes that cfDNA is a mechanistic biomarker to predict mortality in AILI mice. The combination of scavenging cfDNA and reducing oxidative damage provides a promising treatment for AILI.

Diagnosis and monitoring of virus-associated cancer using cell-free DNA

Viral-associated cancers are a distinct group of malignancies with a unique pathogenesis and epidemiology. Liquid biopsy is a minimally invasive way to identify tumor-associated abnormalities in blood derivatives, such as plasma, to guide the diagnosis, prognosis, and treatment of patients with cancer. Liquid biopsy encompasses a multitude of circulating analytes with the most extensively studied being cell-free DNA (cfDNA). In recent decades, substantial advances have been made toward the study of circulating tumor DNA in nonviral-associated cancers. Many of these observations have been translated to the clinic to improve the outcomes of patients with cancer. The study of cfDNA in viral-associated cancers is rapidly evolving and reveals tremendous potential for clinical applications. This review provides an overview of the pathogenesis of viral-associated malignancies, the current state of cfDNA analysis in oncology, the current state of cfDNA analysis in viral-associated cancers, and perspectives for the future of liquid biopsies in viral-associated cancers.

Bridging biological cfDNA features and machine learning approaches

Liquid biopsies (LBs), particularly using circulating tumor DNA (ctDNA), are expected to revolutionize precision oncology and blood-based cancer screening. Recent technological improvements, in combination with the ever-growing understanding of cell-free DNA (cfDNA) biology, are enabling the detection of tumor-specific changes with extremely high resolution and new analysis concepts beyond genetic alterations, including methylomics, fragmentomics, and nucleosomics. The interrogation of a large number of markers and the high complexity of data render traditional correlation methods insufficient. In this regard, machine learning (ML) algorithms are increasingly being used to decipher disease- and tissue-specific signals from cfDNA. Here, we review recent insights into biological ctDNA features and how these are incorporated into sophisticated ML applications.

Prenatal genetic diagnosis of monogenic diseases

Prenatal genetic diagnosis of monogenic diseases is a process involving the use of a variety of molecular techniques for the molecular characterization of a potential monogenic disease in the fetus during pregnancy. Prenatal genetic diagnosis can be performed through invasive and non-invasive methods. A distinction must be made between "NIPD" (non-invasive prenatal diagnosis), which is considered to be diagnostic, from "NIPT" (non-invasive prenatal test), which is a screening test that requires subsequent confirmation by invasive methods. The different techniques currently available aim at detecting either, previously characterized pathogenic mutations in the family, the risk haplotype associated with the familial mutation, or potential pathogenic mutation(s) in a gene associated with a diagnostic suspicion. An overview is provided of relevant aspects of prenatal genetic diagnosis of monogenic diseases. The objective of this paper is to describe the main molecular techniques currently available and used in clinical practice. A description is provided of the indications, limitations and analytical recommendations regarding these techniques, and the standards governing genetic counseling. Continuous rapid advances in the clinical applications of genomics have provided increased access to comprehensive molecular characterization. Laboratories are struggling to keep in pace with technology developments.

Diagnostic applications and limitations for the use of cell-free fetal DNA (cffDNA) in animal husbandry and wildlife management

In animal breeding, a species sex can influence the value of the animal. For example, in the horse breeding industry, mares are preferred as polo horses, while in wildlife breeding males with larger horns are more valuable. Therefore, the economic advantages of knowing the unborn fetus' sex are important to successful animal management. Ultrasonography is used to determine the sex of unborn fetuses, but this method places additional stress on the animal and require specialized equipment and expertise. Conversely, molecular-based sexing techniques require less invasive sampling and can determine sex more reliably. Although in humans, various studies have evaluated the use of cell-free fetal DNA (cffDNA) for prenatal sexing, very few animal studies have been published in this field. Several factors can affect the sensitivity of cffDNA-based sex determination, for example the gestational age. These factors are often not optimized and validated when establishing a protocol for prenatal sexing. In this review, we summarize the current literature on cffDNA in animals. We discuss the diagnostic applications and limitations in the use thereof in animal husbandry and wildlife management. Lastly, the feasibility of implementing diagnostic tests is evaluated and solutions are given to the current drawbacks of the technology.

Mutant-RB1 circulating tumor DNA in the blood of unilateral retinoblastoma patients: What happens during enucleation surgery: A pilot study

Cell free DNA (cfDNA) and circulating tumor cell free DNA (ctDNA) from blood (plasma) are increasingly being used in oncology for diagnosis, monitoring response, identifying cancer causing mutations and detecting recurrences. Circulating tumor RB1 DNA (ctDNA) is found in the blood (plasma) of retinoblastoma patients at diagnosis before instituting treatment (naïve). We investigated ctDNA in naïve unilateral patients before enucleation and during enucleation (6 patients/ 8 mutations with specimens collected 5-40 minutes from severing the optic nerve) In our cohort, following transection the optic nerve, ctDNA RB1 VAF was measurably lower than pre-enucleation levels within five minutes, 50% less within 15 minutes and 90% less by 40 minutes.

Circulating DNA fragmentomics and cancer screening

The high fragmentation of nuclear circulating DNA (cirDNA) relies on chromatin organization and protection or packaging within mononucleosomes, the smallest and the most stabilized structure in the bloodstream. The detection of differing size patterns, termed fragmentomics, exploits information about the nucleosomal packing of DNA. Fragmentomics not only implies size pattern characterization but also considers the positioning and occupancy of nucleosomes, which result in cirDNA fragments being protected and persisting in the circulation. Fragmentomics can determine tissue of origin and distinguish cancer-derived cirDNA. The screening power of fragmentomics has been considerably strengthened in the omics era, as shown in the ongoing development of sophisticated technologies assisted by machine learning. Fragmentomics can thus be regarded as a strategy for characterizing cancer within individuals and offers an alternative or a synergistic supplement to mutation searches, methylation, or nucleosome positioning. As such, it offers potential for improving diagnostics and cancer screening.

The Clinical Utility of Droplet Digital PCR for Profiling Circulating Tumor DNA in Breast Cancer Patients

Breast cancer is the most common cancer affecting women worldwide. It is a malignant and heterogeneous disease with distinct molecular subtypes, which has prognostic and predictive implications. Circulating tumor DNA (ctDNA), cell-free fragmented tumor-derived DNA in blood plasma, is an invaluable source of specific cancer-associated mutations and holds great promise for the development of minimally invasive diagnostic tests. Furthermore, serial monitoring of ctDNA over the course of systemic and targeted therapies not only allows unparalleled efficacy assessments but also enables the identification of patients who are at risk of progression or recurrence. Droplet digital PCR (ddPCR) is a powerful technique for the detection and monitoring of ctDNA. Due to its relatively high accuracy, sensitivity, reproducibility, and capacity for absolute quantification, it is increasingly used as a tool for managing cancer patients through liquid biopsies. In this review paper, we gauge the clinical utility of ddPCR as a technique for mutational profiling in breast cancer patients and focus on HER2, PIK3CA, ESR1, and TP53, which represent the most frequently mutated genes in breast cancers.

Cell-Free DNA in the Pathogenesis and Therapy of Non-Infectious Inflammations and Tumors

The basic function of the immune system is the protection of the host against infections, along with the preservation of the individual antigenic identity. The process of self-tolerance covers the discrimination between self and foreign antigens, including proteins, nucleic acids, and larger molecules. Consequently, a broken immunological self-tolerance results in the development of autoimmune or autoinflammatory disorders. Immunocompetent cells express pattern-recognition receptors on their cell membrane and cytoplasm. The majority of endogenous DNA is located intracellularly within nuclei and mitochondria. However, extracellular, cell-free DNA (cfDNA) can also be detected in a variety of diseases, such as autoimmune disorders and malignancies, which has sparked interest in using cfDNA as a possible biomarker. In recent years, the widespread use of liquid biopsies and the increasing demand for screening, as well as monitoring disease activity and therapy response, have enabled the revival of cfDNA research. The majority of studies have mainly focused on the function of cfDNA as a biomarker. However, research regarding the immunological consequences of cfDNA, such as its potential immunomodulatory or therapeutic benefits, is still in its infancy. This article discusses the involvement of various DNA-sensing receptors (e.g., absent in melanoma-2; Toll-like receptor 9; cyclic GMP-AMP synthase/activator of interferon genes) in identifying host cfDNA as a potent danger-associated molecular pattern. Furthermore, we aim to summarize the results of the experimental studies that we recently performed and highlight the immunomodulatory capacity of cfDNA, and thus, the potential for possible therapeutic consideration.

Applications of molecular barcode sequencing for the detection of low-frequency variants in circulating tumour DNA from hepatocellular carcinoma

PURPOSE

Liquid biopsy has emerged as a promising tool for minimally invasive and accurate detection of various malignancies. We aimed to apply molecular barcode sequencing to circulating tumour DNA (ctDNA) from liquid biopsies of hepatocellular carcinoma (HCC).

STUDY DESIGN

Patients with HCC or benign liver disease were enrolled between 2017 and 2018. Matched tissue and serum samples were obtained from these patients. Plasma cell-free DNA was extracted and subjected to targeted sequencing with ultra-high coverage and molecular barcoding.

RESULTS

The study included 143 patients: 102 with HCC, 7 with benign liver tumours and 34 with chronic liver disease. No tier 1/2 or oncogenic mutations were detected in patients with benign liver disease. Among the HCC patients, 49 (48%) had tier 1/2 mutations in at least one gene; detection rates were higher in advanced stages (75%) than in early stages (26%-33%). TERT was the most frequently mutated gene (30%), followed by TP53 (16%), CTNNB1 (14%), ARID2 (5%), ARID1A (4%), NFE2L2 (4%), AXIN1 (3%) and KRAS (1%). Survival among patients with TP53 mutations was significantly worse (p = 0.007) than among patients without these mutations, whereas CTNNB1 and TERT mutations did not affect survival. ctDNA testing combined with α-fetoprotein and prothrombin induced by vitamin K absence-II analyses improved HCC detection, even in early stages.

CONCLUSIONS

ctDNA detection using molecular barcoding technology offers dynamic and personalized information concerning tumour biology, such information can guide clinical diagnosis and management. This detection also has the potential as a minimally invasive approach for prognostic stratification and post-therapeutic monitoring.

Clinical and Biological Aspects of Disseminated Tumor Cells and Dormancy in Breast Cancer

Progress in detection and treatment have drastically improved survival for early breast cancer patients. However, distant recurrence causes high mortality and is typically considered incurable. Cancer dissemination occurs via circulating tumor cells (CTCs) and up to 75% of breast cancer patients could harbor micrometastatses at time of diagnosis, while metastatic recurrence often occurs years to decades after treatment. During clinical latency, disseminated tumor cells (DTCs) can enter a state of cell cycle arrest or dormancy at distant sites, and are likely shielded from immune detection and treatment. While this is a challenge, it can also be seen as an outstanding opportunity to target dormant DTCs on time, before their transformation into lethal macrometastatic lesions. Here, we review and discuss progress made in our understanding of DTC and dormancy biology in breast cancer. Strides in our mechanistic insights of these features has led to the identification of possible targeting strategies, yet, their integration into clinical trial design is still uncertain. Incorporating minimally invasive liquid biopsies and rationally designed adjuvant therapies, targeting both proliferating and dormant tumor cells, may help to address current challenges and improve precision cancer care.

ESMO recommendations on the use of circulating tumour DNA assays for patients with cancer: a report from the ESMO Precision Medicine Working Group

Circulating tumour DNA (ctDNA) assays conducted on plasma are rapidly developing a strong evidence base for use in patients with cancer. The European Society for Medical Oncology convened an expert working group to review the analytical and clinical validity and utility of ctDNA assays. For patients with advanced cancer, validated and adequately sensitive ctDNA assays have utility in identifying actionable mutations to direct targeted therapy, and may be used in routine clinical practice, provided the limitations of the assays are taken into account. Tissue based testing remains the preferred test for many cancer patients, due to limitations of ctDNA assays detecting fusion events and copy number changes, although ctDNA assays may be routinely used when faster results will be clinically important, or when tissue biopsies are not possible or inappropriate. Reflex tumour testing should be considered following a non-informative ctDNA result, due to false negative results with ctDNA testing. In patients treated for early-stage cancers, detection of molecular residual disease (MRD) or molecular relapse (MR), has high evidence of clinical validity in anticipating future relapse in many cancers. MRD/MR detection cannot be recommended in routine clinical practice, as currently there is no evidence for clinical utility in directing treatment. Additional potential applications of ctDNA assays, under research development and not recommended for routine practice, include identifying patients not responding to therapy with early dynamic changes in ctDNA levels, monitoring therapy for the development of resistance mutations prior to clinical progression, and in screening asymptomatic people for cancer. Recommendation for reporting of results, future development of ctDNA assays, and future clinical research are made.

Potential clinical utility of liquid biopsies in ovarian cancer

Ovarian cancer (OC) is the most lethal gynecologic malignancy worldwide. One of the main challenges in the management of OC is the late clinical presentation of disease that results in poor survival. Conventional tissue biopsy methods and serological biomarkers such as CA-125 have limited clinical applications. Liquid biopsy is a novel sampling method that analyzes distinctive tumour components released into the peripheral circulation, including circulating tumour DNA (ctDNA), circulating tumour cells (CTCs), cell-free RNA (cfRNA), tumour-educated platelets (TEPs) and exosomes. Increasing evidence suggests that liquid biopsy could enhance the clinical management of OC by improving early diagnosis, predicting prognosis, detecting recurrence, and monitoring response to treatment. Capturing the unique tumour genetic landscape can also guide treatment decisions and the selection of appropriate targeted therapies. Key advantages of liquid biopsy include its non-invasive nature and feasibility, which allow for serial sampling and longitudinal monitoring of dynamic tumour changes over time. In this review, we outline the evidence for the clinical utility of each liquid biopsy component and review the advantages and current limitations of applying liquid biopsy in managing ovarian cancer. We also highlight future directions considering the current challenges and explore areas where more studies are warranted to elucidate its emerging clinical potential.

CfDNA Measurement as a Diagnostic Tool for the Detection of Brain Somatic Mutations in Refractory Epilepsy

Epilepsy is a neurological disorder that affects more than 50 million people. Its etiology is unknown in approximately 60% of cases, although the existence of a genetic factor is estimated in about 75% of these individuals. Hundreds of genes involved in epilepsy are known, and their number is increasing progressively, especially with next-generation sequencing techniques. However, there are still many cases in which the results of these molecular studies do not fully explain the phenotype of the patients. Somatic mutations specific to brain tissue could contribute to the phenotypic spectrum of epilepsy. Undetectable in the genomic DNA of blood cells, these alterations can be identified in cell-free DNA (cfDNA). We aim to review the current literature regarding the detection of somatic variants in cfDNA to diagnose refractory epilepsy, highlighting novel research directions and suggesting further studies.

Trans-Renal Cell-Free Tumor DNA for Urine-Based Liquid Biopsy of Cancer

Cancer biomarkers are a promising tool for cancer detection, personalization of therapy, and monitoring of treatment response or recurrence. “Liquid biopsy” commonly refers to minimally invasive or non-invasive sampling of a bodily fluid (i.e., blood, urine, saliva) for detection of cancer biomarkers such as circulating tumor cells or cell-free tumor DNA (ctDNA). These methods offer a means to collect frequent tumor assessments without needing surgical biopsies. Despite much progress with blood-based liquid biopsy approaches, there are limitations—including the limited amount of blood that can be drawn from a person and challenges with collecting blood samples at frequent intervals to capture ctDNA biomarker kinetics. These limitations are important because ctDNA is present at extremely low levels in plasma and there is evidence that measuring ctDNA biomarker kinetics over time can be useful for clinical prediction. Additionally, blood-based assays require access to trained phlebotomists and often a trip to a healthcare facility. In contrast, urine is a body fluid that can be self-collected from a patient’s home, at frequent intervals, and mailed to a laboratory for analysis. Multiple reports indicate that fragments of ctDNA pass from the bloodstream through the kidney’s glomerular filtration system into the urine, where they are known as trans-renal ctDNA (TR-ctDNA). Accumulating studies indicate that the limitations of blood based ctDNA approaches for cancer can be overcome by measuring TR-ctDNA. Here, we review current knowledge about TR-ctDNA in urine as a cancer biomarker approach, and discuss its clinical potential and open questions in this research field.

Circulating Tumor DNA: An Emerging Tool in Gastrointestinal Cancers

Circulating tumor DNA (ctDNA) is tumor-derived fragmented DNA in the bloodstream that has come from primary or metastatic cancer sites. Neoplasm-specific genetic and epigenetic abnormalities are increasingly being identified through liquid biopsy: a novel, minimally invasive technique used to isolate and analyze ctDNA in the peripheral circulation. Liquid biopsy and other emerging ctDNA technologies represent a paradigm shift in cancer diagnostics because they allow for the detection of minimal residual disease in patients with early-stage disease, improve risk stratification, capture tumor heterogeneity and genomic evolution, and enhance ctDNA-guided adjuvant and palliative cancer therapy. Moreover, ctDNA can be used to monitor the tumor response to neoadjuvant and postoperative therapy in patients with metastatic disease. Using clearance of ctDNA as an endpoint for escalation/de-escalation of adjuvant chemotherapy for patients considered to have high-risk disease has become an important area of research. The possibility of using ctDNA as a surrogate for treatment response-including for overall survival, progression-free survival, and disease-free survival-is an attractive concept; this surrogate will arguably reduce study duration and expedite the development of new therapies. In this review, we summarize the current evidence on the applications of ctDNA for the diagnosis and management of gastrointestinal tumors. Gastrointestinal cancers-including tumors of the esophagus, stomach, colon, liver, and pancreas-account for one-quarter of global cancer diagnoses and contribute to more than one-third of cancer-related deaths. Given the prevalence of gastrointestinal malignancies, ctDNA technology represents a powerful tool to reduce the global burden of disease.

Cell-Free DNA Fragmentomics in Liquid Biopsy

Cell-free DNA (cfDNA) in bodily fluids has rapidly transformed the development of noninvasive prenatal testing, cancer liquid biopsy, and transplantation monitoring. Plasma cfDNA consists of a mixture of molecules originating from various bodily tissues. The study of the fragmentation patterns of cfDNA, also referred to as ‘fragmentomics’, is now an actively pursued area of biomarker research. Clues that cfDNA fragmentation patterns might carry information concerning the tissue of origin of cfDNA molecules have come from works demonstrating that circulating fetal, tumor-derived, and transplanted liver-derived cfDNA molecules have a shorter size distribution than the background mainly of hematopoietic origin. More recently, an improved understanding of cfDNA fragmentation has provided many emerging fragmentomic markers, including fragment sizes, preferred ends, end motifs, single-stranded jagged ends, and nucleosomal footprints. The intrinsic biological link between activities of various DNA nucleases and characteristic fragmentations has been demonstrated. In this review, we focus on the biological properties of cell-free DNA unveiled recently and their potential clinical applications.

Utility of Plasma Microbial Cell-Free DNA Decay Kinetics After Aortic Valve Replacement for Bartonella Endocarditis: Case Report

Background

Detection and sequencing of circulating microbial cell-free DNA (mcfDNA) in plasma is an increasingly popular tool for diagnosing many infectious diseases, but could also be used to monitor the progress of infection. However, the decay of this microbial cell-free DNA in blood following treatment has not been previously characterized.

Case Presentation

A 53 year-old male was diagnosed with Bartonella quintana bioprosthetic aortic valve endocarditis by sequencing of the mcfDNA in the blood (Karius, Redwood City, CA). We then monitored the kinetics of decay of mcfDNA after parenteral antibiotics and valve resection in this individual. We measured plasma mcfDNA (Karius) in serial samples obtained in the operating room to calculate mcfDNA half-life after valve resection. After four weeks of parenteral antibiotics, Bartonella mcfDNA signal decreased by 78%. The signal subsequently rose during operative manipulation of the infected valve but dropped 81-fold over four hours following valve resection. The half-life of mcfDNA between the time shortly following resection of the infected valve and 24 to 48 hours post-operatively was between 35 and 115 minutes. The trend in mcfDNA signal was characterized by rapid and then slower phases of decay within 24 hours, and little change between 24 and 48 hours.

Conclusions

This study is one of the first to characterize decay kinetics of mcfDNA and highlights the potential of monitoring mcfDNA in addressing major challenges in infective endocarditis management, including monitoring the response to therapy, and as an early screen for recurrence.

Selection of new diagnostic markers for Dirofilaria repens infections with the use of phage display technology

Dirofilaria repens is a parasitic nematode causing vector-borne disease (dirofilariasis), considered an emerging problem in veterinary and human medicine. Although main hosts are carnivores, particularly dogs, D. repens shows high zoonotic potential. The disease spreads uncontrollably, affecting new areas. Since there is no vaccine against dirofilariasis, the only way to limit disease transmission is an early diagnosis. Currently, diagnosis depends on the detection of microfilariae in the host bloodstream using modified Knott's test or multiplex PCR. However, the efficacy of tests relying on microfilariae detection is limited by microfilariae periodic occurrence. Therefore, a new reliable diagnostic test is required. Our study aimed to select new diagnostic markers for dirofilariasis with potential application in diagnostics. We focused on single epitopes to ensure high specificity of diagnosis and avoid cross-reactivity with the other parasite infections common in dogs. Using phage display technology and 12-mer peptides library, we selected epitopes highly reactive with IgG from sera of infected dogs. Additionally, our study presents the possibility of detecting D. repens specific cell-free DNA in dogs with no microfilaria but high IgG and IgM antibody levels against parasite somatic antigen.

Monitoring and adapting cancer treatment using circulating tumor DNA kinetics: Current research, opportunities, and challenges

Circulating tumor DNA (ctDNA) has emerged as a biomarker with wide-ranging applications in cancer management. While its role in guiding precision medicine in certain tumors via noninvasive detection of susceptibility and resistance alterations is now well established, recent evidence has pointed to more generalizable use in treatment monitoring. Quantitative changes in ctDNA levels over time (i.e., ctDNA kinetics) have shown potential as an early indicator of therapeutic efficacy and could enable treatment adaptation. However, ctDNA kinetics are complex and heterogeneous, affected by tumor biology, host physiology, and treatment factors. This review outlines the current preclinical and clinical knowledge of ctDNA kinetics in cancer and how early on-treatment changes in ctDNA levels could be applied in clinical research to collect evidence to support implementation in daily practice.

Liquid biopsies for residual disease and recurrence

Detection of minimal residual disease in patients with cancer, who are in complete remission with no cancer cells detectable, has the potential to improve recurrence-free survival through treatment selection. Studies analyzing circulating tumor DNA (ctDNA) in patients with solid tumors suggest the potential to accurately predict and detect relapse, enabling treatment strategies that may improve clinical outcomes. Over the past decade, assays for ctDNA detection in plasma samples have steadily increased in sensitivity and specificity. These are applied for the detection of residual disease after treatment and for earlier detection of recurrence. Novel clinical trials are now assessing how assays for "residual disease and recurrence" (RDR) may influence current treatment paradigms and potentially change the landscape of risk classification for cancer recurrence. In this review, we appraise the progress of RDR detection using ctDNA and consider the emerging role of liquid biopsy in the monitoring and management of solid tumors.

The integrity of cfDNA in follicular fluid and spent medium from embryo culture is associated with embryo grade in patients undergoing in vitro fertilization

PURPOSE

This study was conducted to verify if the cfDNA integrity (cfDI) in follicular fluid and subsequent spent embryo medium (SEM) could serve as potential non-invasive biomarker for high-grade embryo selection during IVF/ICSI.

METHODS

Thirty-two follicular fluids, 32 subsequent corresponding cleavage embryo SEM, and 23 subsequent blastocyst SEM were collected from 11 patients undergoing IVF/ICSI. CfDI was measured by ALU gene amplicons with different sizes by qPCR, as the ratio of long to short fragments.

RESULTS

CfDI in follicular fluid corresponding to subsequent high-grade cleavage embryos and blastocysts was significantly lower than that related to low-grade embryos (p = 0.018). Conversely, cfDI in SEM was significantly and positively correlated with high-grade embryos at both stages (p = 0.009). ROC curves of the analysis of cfDI in follicular fluid showed great potential in predicting subsequent embryogenesis and embryo grade (AUC > 0.927). Regardless of the cleavage embryo grade by morphology, cfDI in day 3 SEM could predict if the cleavage embryo could develop to a high-grade blastocyst (AUC = 0.820). A concordant shift pattern of cfDI from follicular fluid to subsequent day 3 SEM and day 5 SEM was found in 81.82% participants featured by various clinical characteristics.

CONCLUSION

CfDI in follicular fluid and SEM was significantly correlated with embryogenesis and embryo grade and could serve as a potential non-invasive biomarker in high-grade embryo selection. Direct qPCR was proved as a labor-saving and sensitive method for the analysis of cfDI in low volume of SEM.

Emerging role of cell-free DNA in kidney transplantation

Monitoring kidney transplants for rejection conventionally includes serum creatinine, immunosuppressive drug levels, proteinuria, and donor-specific antibody (DSA). Serum creatinine is a late marker of allograft injury, and the predictive ability of DSA regarding risk of rejection is variable. Histological analysis of an allograft biopsy is the standard method for diagnosing rejection but is invasive, inconvenient, and carries risk of complications. There has been a long quest to find a perfect biomarker that noninvasively predicts tissue injury caused by rejection at an early stage, so that diagnosis and treatment could be pursued without delay in order to minimize irreversible damage to the allograft. In this review, we discuss relatively novel research on identifying biomarkers of tissue injury, specifically elaborating on donor-derived cell-free DNA, and its clinical utility.

Role of Cell-Free DNA and Deoxyribonucleases in Tumor Progression

Many studies have reported an increase in the level of circulating cell-free DNA (cfDNA) in the blood of patients with cancer. cfDNA mainly comes from tumor cells and, therefore, carries features of its genomic profile. Moreover, tumor-derived cfDNA can act like oncoviruses, entering the cells of vulnerable organs, transforming them and forming metastatic nodes. Another source of cfDNA is immune cells, including neutrophils that generate neutrophil extracellular traps (NETs). Despite the potential eliminative effect of NETs on tumors, in some cases, their excessive generation provokes tumor growth as well as invasion. Considering both possible pathological contributions of cfDNA, as an agent of oncotransformation and the main component of NETs, the study of deoxyribonucleases (DNases) as anticancer and antimetastatic agents is important and promising. This review considers the pathological role of cfDNA in cancer development and the role of DNases as agents to prevent and/or prohibit tumor progression and the development of metastases.

Short single-stranded DNAs with putative non-canonical structures comprise a new class of plasma cell-free DNA

Background

Cell-free DNA (cfDNA), which is extracellular DNA present in the circulating plasma and other body fluids, is currently investigated as a minimally invasive, highly informative biomarker. While nucleosome-sized cfDNA fragments have been investigated intensively, shorter DNA fragments in the plasma have not been studied due to several technical limitations.

Results

We aimed to investigate the existence of shorter cfDNA fragments in the blood. Using an improved cfDNA purification protocol and a 3′-end-labeling method, we found DNA fragments of approximately 50 nucleotides in length in the human plasma, present at a molar concentration comparable to that of nucleosome-sized fragments. Unfortunately, these short fragments cannot be recovered by widely used cfDNA isolation methods. In addition, they are composed of single-stranded DNA (ssDNA), thus escaping detection in previous studies. Therefore, we established a library-preparation protocol based on our unique ssDNA ligation technique and applied it to the isolated cfDNA. Deep sequencing of these libraries revealed that the short fragments are derived from hundreds of thousands of genomic sites in open chromatin regions and enriched with transcription factor-binding sites. Remarkably, antisense strands of putative G-quadruplex motifs occupy as much as one-third of the peaks by these short fragments.

Conclusions

We propose a new class of plasma cfDNA composed of short single-stranded fragments that potentially form non-canonical DNA structures.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-021-01160-8.

Integrity of cell-free DNA in maternal plasma extracellular vesicles as a potential biomarker for non-invasive prenatal testing

OBJECTIVE

Large proportions of cell-free DNA (cfDNA) in plasma are localized in extracellular vesicles (EVs), which are secreted from placental cells. This study was conducted to reveal the integrity pattern of cfDNA in maternal plasma EVs (evcfDI) across gestation, and explore if evcfDI could be a potential biomarker in screening for aneuploid fetus in non-invasive prenatal testing (NIPT).

METHODS

A total of 180 maternal plasma samples were collected during NIPT. Both evcfDNA and fetal evcfDNA (evcffDNA) were measured by quantitative PCR of LINE1 and SRY gene amplicons with different sizes. The evcfDI was calculated as the ratio of long to short fragments.

RESULTS

evcfDI is not affected by gestational age; whereas evcffDI has a mild decreasing trend with increasing gestational age (P = 0.048). evcfDI is significantly and negatively correlated with maternal body mass index (BMI; calculated as weight in kilograms divided by the square of height in meters: ≤18.5, 18.5-25, and ≥25) (P < 0.01) and age (<35 and ≥35 years) (P < 0.01). Mean evcfDI decreases from 2.113 in euploid controls to 0.681 in those with an aneuploid fetus in NIPT (P = 0.003).

CONCLUSION

Maternal clinical characteristics such as BMI and age could be innovative biomarkers to calibrate evcfDI, which was shown to be a potential indicator of an aneuploid fetus. Analysis of evcfDI based on quantitative PCR could serve as a novel, rapid, and low-cost NIPT strategy, which might facilitate testing at earlier gestations.

Donor-Derived Cell-Free DNA to Diagnose Graft Rejection Post-Transplant: Past, Present and Future

Donor-derived cell-free DNA (dd-cfDNA) is a non-invasive biomarker that is more sensitive and specific towards diagnosing any graft injury or rejection. Due to its applicability over all transplanted organs irrespective of age, sex, race, ethnicity, and the non-requirement of a donor sample, it emerges as a new gold standard for graft health and rejection monitoring. Published research articles describing the role and efficiency of dd-cfDNA were identified and scrutinized to acquire a brief understanding of the history, evolution, emergence, role, efficiency, and applicability of dd-cfDNA in the field of transplantation. The dd-cfDNA can be quantified using quantitative PCR, next-generation sequencing, and droplet digital PCR, and there is a commendatory outcome in terms of diagnosing graft injury and monitoring graft health. The increased levels of dd-cfDNA can diagnose the rejection prior to any other presently used biochemistry or immunological assay methods. Biopsies are performed when these tests show any signs of injury and/or rejection. Therefore, by the time these tests predict and show any unusual or improper activity of the graft, the graft is already damaged by almost 50%. This review elucidates the evolution, physiology, techniques, limitations, and prospects of dd-cfDNA as a biomarker for post-transplant graft damage and rejection.

Targeted Next-Generation Sequencing of Circulating Tumor DNA, Bone Marrow, and Peripheral Blood Mononuclear Cells in Pediatric AML

Background

The aim of the study was to validate the diagnostic role of circulating tumor DNA (ctDNA) in genetics aberration on the basis of next-generation sequencing (NGS) in pediatric acute myeloid leukemia (AML).

Methods

Bone marrow (BM) and peripheral blood (PB) were collected from 20 AML children at the time of initial diagnosis, and a ctDNA sample was isolated from PB. Detection of mutation was performed on ctDNA, BM, and peripheral blood mononuclear cell (PBMC) by NGS based on a 185-gene panel.

Results

Among 185 genes sequenced by the NGS platform, a total of 82 abnormal genes were identified in 20 patients. Among them, 61 genes (74.39%) were detected in ctDNA, PBMC, and BM samples, while 11 (13.41%) genes were found only in ctDNA and 4 (4.88%) were detected only in the BM sample, and 2 (2.44%) were detected only in PBMC. A total of 239 mutations were detected in three samples, while 209 in ctDNA, 180 in bone marrow, and 184 in PBMC. One hundred sixty-four mutations in ctDNA were shared by matched BM samples, and the median variant allelic frequency (VAF) of these mutations was 41.34% (range, 0.55% to 99.96%) and 44.36% (range, 0.56% to 99.98%) in bone marrow and ctDNA. It was found that 65.79% (75/114) of mutations with clinical significance were detected in three samples, with 9 mutations detected both in ctDNA and BM, and 2 mutations detected both in PBMC and BM. The consistency of mutations with clinical significance between ctDNA and BM was 77.06% (84/109). Among the 84 mutations with clinical significance detected in both sources, the concordance of VAF assessment by both methods was high (R² = 0.895).

Conclusion

This study demonstrates that ctDNA was a reliable sample in pediatric AML and can be used for mutation detection. Consistency analysis showed that ctDNA can mirror the genomic information from BM. In addition, a subset of mutations was exclusively detected in ctDNA. These data support the fact that monitoring ctDNA with next-generation sequencing-based assays can provide more information about gene mutations to guide precision treatment in pediatric AML.

The Monitoring of Donor-derived Cell-free DNA in Kidney Transplantation

Cell-free DNA (cfDNA) exists in plasma and can be measured by several techniques. It is now possible to differentiate donor-derived cfDNA (ddcfDNA) from recipient cfDNA in the plasma or urine of solid organ transplant recipients in the absence of donor and recipient genotyping. The assessment of ddcfDNA is being increasingly studied as a noninvasive means of identifying acute rejection (AR) in solid organ transplants, including subclinical AR. We herein review the literature on the correlation of ddcfDNA with AR in kidney transplantation. There have been at least 15 observational studies that have assessed ddcfDNA in urine or plasma using various methodologies with various thresholds for abnormality. Overall, elevated ddcfDNA indicates allograft injury as may occur with AR, infection, or acute tubular injury but may also be found in clinically stable patients with normal histology. Sensitivity is greater for antibody-mediated AR than for cell-mediated AR, and normal levels do not preclude significant cell-mediated rejection. Measurement of ddcfDNA is not a replacement for biopsy that remains the gold standard for diagnosing AR. Serial monitoring of stable patients may allow earlier detection of subclinical AR, but the efficacy of this approach remains to be established. Normal levels should not preclude planned protocol biopsies. There may be roles for following ddcfDNA levels to assess the adequacy of treatment of AR and to guide the intensity of immunosuppression in the individual patient. Randomized controlled trials are necessary to validate the benefit and cost-effectiveness for these various uses. No firm recommendations can be made at this time.

Stress and circulating cell-free mitochondrial DNA: A systematic review of human studies, physiological considerations, and technical recommendations

Cell-free mitochondrial DNA (cf-mtDNA) is a marker of inflammatory disease and a predictor of mortality, but little is known about cf-mtDNA in relation to psychobiology. A systematic review of the literature reveals that blood cf-mtDNA varies in response to common real-world stressors including psychopathology, acute psychological stress, and exercise. Moreover, cf-mtDNA is inducible within minutes and exhibits high intra-individual day-to-day variation, highlighting the dynamic regulation of cf-mtDNA levels. We discuss current knowledge on the mechanisms of cf-mtDNA release, its forms of transport ("cell-free" does not mean "membrane-free"), potential physiological functions, putative cellular and neuroendocrine triggers, and factors that may contribute to cf-mtDNA removal from the circulation. A review of in vitro, pre-clinical, and clinical studies shows conflicting results around the dogma that physiological forms of cf-mtDNA are pro-inflammatory, opening the possibility of other physiological functions, including the cell-to-cell transfer of whole mitochondria. Finally, to enhance the reproducibility and biological interpretation of human cf-mtDNA research, we propose guidelines for blood collection, cf-mtDNA isolation, quantification, and reporting standards, which can promote concerted advances by the community. Defining the mechanistic basis for cf-mtDNA signaling is an opportunity to elucidate the role of mitochondria in brain-body interactions and psychopathology.

Verification of performance of a direct fluorescent assay for cell-free DNA quantification, stability according to pre-analytical storage conditions, and the effect of freeze-thawing

A simple fluorescence-based cell-free DNA (CFD) assay has been previously developed that can directly measure nucleic acids without prior DNA extraction and amplification. However, studies on fluorescence-based CFD are lacking. In particular, there is no known information regarding the stability with regard to pre-analytical storage conditions in relation to time and temperature, or on the influence of freeze-thawing. Plasma was directly assayed to measure CFD using PicoGreen™ reagent. Standard linearity and accuracy were confirmed using salmon sperm DNA. Whole blood was left at room temperature (RT) and at 4˚C, and then plasma was separated. The CFD was also measured using thawed plasma after 1 week of freezing. As a correlation with a sperm DNA concentration, CFD demonstrated linearity over a wide range of concentrations, with a 0.998 correlation coefficient. The CFD level showed a change of up to 2.5 µg/ml according to pre-analytical storage time, and the changes were not consistent over time. The CFD values at RT after 1 h were similar to the baseline values, and the relative standard deviation was lowest under this condition. The CFD values between 4˚C and RT were similar over all time periods assessed. After freeze-thawing, the change in CFD value was reduced compared to that before freezing. The present study showed that CFD measurements using plasma processed within 1 h were optimal. Additionally, the effects of substantial changes according to storage conditions were reduced after freeze-thawing, and thus studies using stored samples is viable and relevant.

Circulating extracellular DNA is in association with continuous metabolic syndrome score in healthy adolescents

Obesity is associated with chronic low-grade inflammation that eventually leads to metabolic complications. Extracellular DNA (ecDNA) is a damage-associated molecular pattern. Extracellular mitochondrial DNA can activate innate immunity. We hypothesized that ecDNA, especially of mitochondrial origin, could be associated with components of the metabolic syndrome in young healthy probands. In a cross-sectional study, healthy adolescents (n = 1,249) provided blood samples. Anthropometric data, blood pressure, and blood counts were assessed. In addition, biochemical analysis of sera or plasma was conducted, including the quantification of advanced oxidation protein products (AOPPs) as a marker of oxidative stress induced by neutrophil or monocyte activation. Plasma ecDNA was isolated and measured by fluorometry. Nuclear and mitochondrial DNA were quantified by real-time PCR. Males had higher total plasma ecDNA [15 (11-21) vs. 11 (8-17) ng/mL; median (interquartile range)], nuclear [1,760 (956-3,273) vs. 1,153 (600-2,292) genome equivalents (GE)/mL], and mitochondrial [37,181 (14,836-90,896) vs. 30,089 (12,587-72,286) GE/mL] DNA. ecDNA correlated positively with the continuous metabolic syndrome score (r = 0.158 for males and r = 0.134 for females). Stronger correlations were found between ecDNA of mitochondrial origin and AOPP (r = 0.202 and 0.186 for males and females, respectively). Multivariate regression analysis revealed associations of nuclear DNA with leukocyte and erythrocyte counts. The results of this study of healthy adolescents show that circulating ecDNA is associated with the risk of metabolic syndrome, not with obesity per se. The association between mitochondrial ecDNA and AOPP requires further attention as it supports a potential role of mitochondria-induced sterile inflammation in the pathogenesis of the metabolic syndrome.

Donor-derived Cell-free DNA Kinetics Post-kidney Transplant Biopsy

Background.

Donor-derived cell-free DNA (dd-cfDNA) has generated interest as a biomarker for kidney injury including transplant (KT) rejection. It is possible that the KT biopsy procedure can cause the release of dd-cfDNA, therefore affecting the reliability of this assay in the postbiopsy period. We evaluated the effect of KT biopsy on the kinetics of dd-cfDNA.

Methods.

We conducted a single-arm prospective study. Samples were collected from 16 adult KT recipients undergoing KT biopsy. All participants had samples drawn within 8 h before the biopsy (prebiopsy), within 20 min (hour 0), 2 h (hour 2), and 24–48 h (hours 24–48) after the biopsy. We evaluated the change in dd-cfDNA from the prebiopsy time point to the following 3 time points after the biopsy.

Results.

At hour 0 and hour 2, there was a significantly larger log dd-cfDNA mean score compared with the prebiopsy score (least square mean estimate 0.4 [0.17-0.63] and 0.39 [0.09-0.68], respectively). By 24–28 h postbiopsy, there was no significant difference in log dd-cfDNA mean score compared with the prebiopsy score (least square mean estimate −0.21 [−0.6 to 0.19]).

Conclusions.

Mechanical injury from a KT biopsy can transiently increase circulating dd-cfDNA. The increase resolves by 24–48 h after the biopsy. Providers should wait 48 h postbiopsy to obtain dd-cfDNA levels to establish the correct baseline to be used for monitoring.

Post-Biopsy Cell-Free DNA From Blood: An Open Window on Primary Prostate Cancer Genetics and Biology

Circulating cell-free DNA (ccfDNA), released from normal and cancerous cells, is a promising biomarker for cancer detection as in neoplastic patients it is enriched in tumor-derived DNA (ctDNA). ctDNA contains cancer-specific mutations and epigenetic modifications, which can have diagnostic/prognostic value. However, in primary tumors, and in particular in localized prostate cancer (PCa), the fraction of ctDNA is very low and conventional strategies to study ccfDNA are unsuccessful. Here we demonstrate that prostate biopsy, by causing multiple injuries to the organ, leads to a significant increase in plasma concentration of ccfDNA (P<0.0024) in primary PCa patients. By calculating the minor allele fraction at patient-specific somatic mutations pre- and post-biopsy, we show that ctDNA is significantly enriched (from 3.9 to 164 fold) after biopsy, representing a transient “molecular window” to access and analyze ctDNA. Moreover, we show that newly released ccfDNA contains a larger fraction of di-, tri- and multi-nucleosome associated DNA fragments. This feature could be exploited to further enrich prostate-derived ccfDNA and to analyze epigenetic markers. Our data represent a proof-of-concept that liquid tumor profiling from peripheral blood performed just after the biopsy procedure can open a “valuable molecular metastatic window” giving access to the tumor genetic asset, thus providing an opportunity for early cancer detection and individual genomic profiling in the view of PCa precision medicine.

The Nexus of cfDNA and Nuclease Biology

Cell-free DNA (cfDNA) is a widely used noninvasive biomarker for diagnosis and prognosis of multiple disease states. Emerging evidence suggests that cfDNA might not just be passive waste products of cell death but could have a physiological and pathological function in inflammation and autoimmunity. The balance of cfDNA generation and clearance may thus be vital in health and disease. In particular, plasma nuclease activity has been linked to multiple pathologies including cancer and systemic lupus erythematosus (SLE) and associated with profound changes in the nonrandom fragmentation of cfDNA. Lastly, in this review, we explore the effects of DNA fragmentation factor B (DFFB), DNASE1L3, and DNASE1 on cfDNA levels and their fragmentomic profiles, and what these recent insights reveal about the biology of cfDNA.