Introduction:
- Non-encapsulated DNA transported from cells into the circulatory system throughout the body is referred to as cell-free DNA (cfDNA).
- cfDNA was originally found in human blood in 1948, but it was not widely used for infectious disease diagnosis and monitoring until decades later, once technology had advanced to utilize the possibilities of cfDNA for a noninvasive, quick, and sensitive approach to diagnosis.
- Plasma, as well as other physiological fluids such as CSF, pleural fluid, urine, saliva, and others, contain cfDNA. Circulating tumor DNA refers to a fraction of that cell-free DNA that comes from a tumor clone (or ctDNA).
History:
In 1948, Mandel and Metais discovered the presence of cell-free DNA (cfDNA) in blood plasma. Bendich and colleagues proposed that cancer-derived cfDNA might be responsible in metastasis seventeen years later, in 1965. The first link to sickness, however, took an additional year to detect. Tan and colleagues discovered that patients with systemic lupus erythematosus had large quantities of circulating cell-free DNA (cfDNA) in their blood in 1966.
According to previous research, the majority of plasma cfDNA molecules in healthy people originated from the hematological system. However, in some physiological or pathological circumstances, such as pregnancy, organ transplantation, and cancer, the related/affected tissues may release more DNA into the peripheral circulation. As a result, noninvasive screening of cfDNA in peripheral blood could discover disorders in individuals. In recent years, a number of technologies based on cfDNA analysis have arisen, including noninvasive prenatal testing (NIPT), liquid biopsy, organ transplant monitoring, and detecting immunological illnesses and malignancies.
Fig: Putative origins of cell-free DNA (cfDNA) in the human body
Properties of cfDNA:
- cfDNA has a number of features that indicate it is produced after a cell has died. cfDNA is a kind of nucleic acid fragment believed to be released from nucleosomes into the circulation after apoptosis or necrosis. Macrophages normally clean away these fragments, but cancer cells overproduce themselves, leaving more cfDNA behind.
- Despite the fact that cfDNA is widespread in human body fluids, its molecular source is unknown. It has a half-life of about two hours and is present in both early and late-stage disease in many common tumors, including non-small cell lung and breast cancer. It is much smaller than genomic DNA, with more than 70% of plasma cfDNA being smaller than 300 bp. It has an average size of 170 bp double-stranded DNA and is present in both early and late-stage disease in many common tumors, including non-small cell lung and breast cancer.
- Monomers, dimers, and trimers are all present in circulation. The amount of cfDNA produced by various specimen types varies greatly. In comparison to Streck and plasma specimen types, serum provides the most cfDNA but has the most genomic DNA contamination. The concentration of cfDNA in plasma fluctuates dramatically, ranging from 1 to 100,000 fragments per milliliter.
- Fetal cfDNA is shorter than maternal cfDNA in pregnant women, according to many research, and hence fetal cfDNA can be utilized to diagnose fetal abnormalities. Based on diverse methodologies, types and stages of tumors, and orientations of cfDNA, the accurate assessment of size profile in cancer patients differed slightly and should be closely examined. Furthermore, the size profile of cfDNA has been widely used in a variety of fields, including quality control in laboratories, enrichment of short DNA fragments, detection of the fetal fraction (FF) and fetal abnormalities in NIPT, tumor progression prediction in liquid biopsies, and allograft damage in transplantation.
Applications:
- The small size of cfDNA is thought to allow it to get through the renal barrier and into the urine. Healthy people’s cfDNA concentrations range from less than 10 ng/ml to more than 1,500 ng/ml.
- Under some health complications (e.g., cancer and infectious diseases) and physiological states, significant changes in the size distribution and quantity of cfDNA in the urine and blood have been reported between individuals and even within the same individual (e.g., pregnancy).
- Circulating cell-free DNA (cfDNA) has been studied as a noninvasive disease biomarker since its discovery in human blood plasma over 70 years ago. Its discovery provoked a wave of research on the role of cfDNA in various diseases.
Fig: Potential applications of cell-free DNA in cancer management
- Clinical applications have triggered a renewed interest, making them a popular and promising research topic in a variety of fields.
- cfDNA can be discovered in a variety of bodily fluids, in both healthy and unhealthy people. The rapid development of novel molecular tools is driving the study and identification of cfDNA, which holds the key to minimally invasive diagnostics, disease monitoring, clinical decision-making, and patient outcomes.
- cfDNA has already had a significant impact on prenatal medicine, and it has the potential to become the standard of care in other domains, like as oncology, transplant medicine, and cardiovascular disorders, in the near future.
References:
- Ranucci R. Cell-Free DNA: Applications in Different Diseases. Methods Mol Biol. 2019; 1909:3-12. doi: 10.1007/978-1-4939-8973-7_1. PMID: 30580419.
- Yan Y-y, Guo Q-r, Wang F-h, Adhikari R, Zhu Z-y, Zhang H-y, Zhou W-m, Yu H, Li J-q and Zhang J-y (2021) Cell-Free DNA: Hope and Potential Application in Cancer. Front. Cell Dev. Biol. 9:639233. doi: 10.3389/fcell.2021.639233.
- Volik, S., Alcaide, M., Morin, R.D. and Collins, C., 2016. Cell-free DNA (cfDNA): clinical significance and utility in cancer shaped by emerging technologies. Molecular Cancer Research, 14(10), pp.898-908.
- Karen Sherwood, Eric T. Weimer, Characteristics, properties, and potential applications of circulating cell-free dna in clinical diagnostics: a focus on transplantation, Journal of Immunological Methods, Volume 463, 2018, Pages 27-38.
- Bronkhorst, A.J., Ungerer, V. and Holdenrieder, S., 2019. The emerging role of cell-free DNA as a molecular marker for cancer management. Biomolecular detection and quantification, 17, p.100087.
- Aucamp, J., Bronkhorst, A.J., Badenhorst, C.P. and Pretorius, P.J., 2018. The diverse origins of circulating cell‐free DNA in the human body: a critical re‐evaluation of the literature. Biological Reviews, 93(3), pp.1649-1683.