Table 1.

Liquid biopsy and its application

Type of biomarker	Method	Tumor	Result	Reference
cfDNA	Multimodal epigenetic sequencing analysis (MESA)	Colorectal cancer	MESA comprehensively analyzed the comprehensive and complementary epigenetic profile of cfDNA, which improved non-invasive cancer detection	[136]
cfDNA	Bisulfite sequencing; constructed a classifier (OvaPrint)	High-grade serous ovarian carcinoma (HGSOC)	OvaPrint can highly sensitively and specifically evaluate symptomatic patients with HGSOC, so it is necessary to further develop its non-HGSOC EOC type for women with symptomatic and asymptomatic masses	[137]
ccfDNA (circulating cell-free DNA)	Methylation-specific real-time PCR	Metastatic prostate cancer	Monitor the therapeutic effect	[138]
Bone marrow (BM); blood plasma (BP)	Quantitative methylation-specific PCR (qMSP); bisulfite amplicon sequencing (BAS)	Acute lymphoblastic leukemia	Cyclic biomarkers based on epigenetics may be used as a substitute for B- and T-ALL subtype classifiers and BM biopsy	[139]
ccfDNA	quantitative methylation-specific polymerase chain reaction	metastatic melanoma	SHOX2 ccfDNAm is an early predictor of the prognosis of patients with melanoma treated with anti-PD-1. The SHOX2 ccfDNAm test may be helpful for individualized treatment decision	[140]
Pleural fluid	Sentinel-MPE liquid biopsy assay	malignancy in pleural fluid	Sentinel-MPE test for detecting tumor-specific methylation based on ten genomic loci can be a supplementary tool for cytological diagnosis of MPE	[141]
ctDNA	ctDNA methylation, quantitative polymerase chain reaction assay	Colorectal Cancer	ctDNA methylation has potential in postoperative management, which can help to detect residual diseases, risk stratification, chemotherapy guidance, and recurrence monitoring in clinical environment	[142]