Circulating Tumor DNA—A Novel Biomarker of Tumor Progression and Its Favorable Detection Techniques

Abstract

Cancer is the second leading cause of death in the world and seriously affects the quality of life of patients. The diagnostic techniques for tumors mainly include tumor biomarker detection, instrumental examination, and tissue biopsy. In recent years, liquid technology represented by circulating tumor DNA (ctDNA) has gradually replaced traditional technology with its advantages of being non-invasive and accurate, its high specificity, and its high sensitivity. ctDNA may carry throughout the circulatory system through tumor cell necrosis, apoptosis, circulating exosome secretion, etc., carrying the characteristic changes in tumors, such as mutation, methylation, microsatellite instability, gene rearrangement, etc. In this paper, ctDNA mutation and methylation, as the objects to describe the preparation process before ctDNA analysis, and the detection methods of two gene-level changes, including a series of enrichment detection techniques derived from PCR, sequencing-based detection techniques, and comprehensive detection techniques, are combined with new materials. In addition, the role of ctDNA in various stages of cancer development is summarized, such as early screening, diagnosis, molecular typing, prognosis prediction, recurrence monitoring, and drug guidance. In summary, ctDNA is an ideal biomarker involved in the whole process of tumor development.

Importance of Ultrasensitive ELISA in Cancer Research

“…Much of cancer research is centered on the analysis of nucleic acids [1]. DNA testing is considered to be the gold standard in cancer testing [2].…”

Use of exosome transcriptome-based analysis to identify novel biomarkers in patients with locally advanced esophageal squamous cell carcinoma undergoing neoadjuvant chemoradiotherapy

“…Analysis of exosomes is benefit to the diagnose of tumor and prediction of the tumor prognosis (6). Previous study has shown that the exosomes secreted by tumors can enter into circulatory system and be detected in the blood (7). Separating the exosomes in the blood could realize the non-invasive way to identify the characteristics of tumors at an early stage and potential therapeutic targets.…”

Somatic Copy Number Alteration in Circulating Tumor DNA for Monitoring of Pediatric Patients with Cancer

“…Recurrent CNAs in MYCN , 1q and 17p loci are considered good biomarkers for cancer monitoring through circulating tumor DNA (ctDNA) detection in liquid biopsy since they are reported in several pediatric malignancies [ 18 , 19 , 20 , 21 , 22 , 23 , 24 ] and can be identified using accessible methodologies, such as digital PCR (dPCR) and qPCR [ 25 ]. Although dPCR provides limited information regarding the profile of alterations, it has a low cost and high sensitivity.…”

“…ctDNA levels are associated with the prognosis and may assist in the disease monitoring of patients diagnosed with a wide range of malignancies, e.g., prostate, breast, bladder and ovarian cancer [ 25 , 28 , 29 , 30 , 31 , 32 , 33 ]. In patients diagnosed with osteosarcoma, higher ctDNA levels were associated with a worse prognosis [ 34 ].…”