Role of circulating tumor DNA methylation in gastric cancer initiation and progression: A comprehensive review

Figure 1 Liquid biopsy performed by using blood/plasma samples. A: The bloodstream close to the tumor mass receives circulating tumor cells, extracellular vesicles, and free nucleic acids from the tumor; B: The main methods that have been used to analyze circulating free DNA in blood samples are real-time PCR, COLD-PCR, digital PCR, BEAMing, and next-generation sequencing. ctDNA: Circulating free DNA.

Figure 2 Applications of circulating free DNA liquid biopsy in the recurrent and/or metastatic setting. A: Genotyping assays permit the deployment of precision-therapy umbrella enrichment studies that seek to identify specific actionable alterations and assign patients (randomly or not) to matched therapies of interest on the basis of a putative predictive biomarker; B: Dynamic and response-guided studies take advantage of the potential for changes in circulating free DNA (ctDNA) levels after treatment to anticipate clinical response to inform a change in therapy; C: To evaluate the utility of ctDNA genotyping and monitoring in the management of metastatic disease. ctDNA: Circulating free DNA. Created with BioRender.com (Supplementary material).

Figure 3 Current approaches for the sensitive detection of circulating free DNA. MS: Mass spectrometry.

Figure 4 Schematic of BEAMing. ctDNA: Circulating free DNA; HP: High pH.

Figure 5 Schematic diagram of the DNA-rN1-DNA-mediated SERS-based platform for circulating free DNA detection. ctDNA: Circulating free DNA; WES: Whole exome sequence; WGS: Whole genome sequence.

Figure 6 Development of a nanoparticle coupling tactic for detecting target KRAS mutations. ctDNA: Circulating free DNA.