Liquid biopsy of circulating tumor cells: From isolation, enrichment, and genome sequencing to clinical applications.

Circulating tumor cells (CTCs), shed from primary tumors into the bloodstream, play a crucial role in metastasis and hold great potential in cancer diagnosis, prognosis, and treatment monitoring. Conventional CTC detection using epithelial biomarkers like epithelial cell adhesion molecule (EpCAM) for immunocapture overlooks mesenchymal-like CTCs with high metastatic potential, spurring the development of non-immunocapture technologies that use biophysical traits for enrichment. Innovations in microfluidic platforms and multi-parametric sorting improve isolation efficiency and address related challenges. Breakthroughs in single-cell genomic and transcriptomic sequencing enable in-depth molecular characterization of CTCs. Clinically, CTC enumeration and molecular profiling are emerging as real-time tools for assessing therapeutic response and predicting outcomes, especially in metastatic breast, prostate, and colorectal cancers. This review focuses on CTC isolation, enrichment techniques, their applications in different tumors, downstream analysis progress, and potential in precision medicine.