Fig. 2

Commonly used techniques for extraction or analysis of RCC liquid biopsies in recent years. CTC isolation mainly includes size-based and antibody-based methods. cfDNA and ctDNA are separated by patients’ genomic alterations. PCR and sequencing are commonly used to detect and analyze mutations, size, expression, and methylation levels. ddPCR and targeting sequencing enable analysis of specific rare DNA with high sensitivity. With the development and diffusion of NGS, researchers can perform high-throughput analysis of cfDNA/ctDNA at a reduced cost. Similar to cfDNA/ctDNA, cfRNA is commonly analyzed by qPCR, ddPCR, methylation-specific quantitative PCR (qMSP), and NGS. Metabolite analysis is mainly performed using MS-based methods, while NMR and inductors have also been used in recent years. Protein analysis mainly depended on ELISA, the standard method for protein level measurements. Some automated analyzers with low cost and high efficiency are commercially available, which have potential for large-scale clinical applications. As an important field of proteomics, circulating cytokine assays use commercial detection platforms or technologies more frequently than Elisa, which enable a rapid detection of multiple cytokines in the blood. Up to now, there is no standard method for the extraction of exosomes. The most commonly used methods in recent years are ultracentrifugation and differential centrifugation. Meanwhile, some extraction reagents are used, such as exoQuick kit, exoEasy maxi kit and Total exosome isolation reagent