[Recent advances in responsive isolation, release and clinical application of circulating tumor cells]

Circulating tumor cells (CTCs) are cells that dissociate from the tumor tissue and enter the lymphatic system or bloodstream with close association with tumor metastasis and recurrence. CTCs contain complete pathological information, which can be extracted by isolation, enrichment, and analysis of the CTCs to guide cancer diagnosis and treatment, thereby significantly improving the monitoring efficiency and prognosis of cancer. Compared with tissue biopsy, liquid biopsy with CTCs as a biomarker enables specific and dynamic detection of tumor growth with a less painful experience. For detection of CTCs, the cells must be captured from body fluids, followed then by their release and enrichment. This review summaries the latest research progress in responsive isolation of CTCs (e.g. with light, dielectrophoresis, acoustophoresis and magnetophoresis), chemical isolation (specific molecules and topological structure) and responsive release (e.g., light, electric, thermal, pH, enzyme responsiveness, and substrates break). Responsive isolation utilizes the differences in physical properties between CTCs and blood cells, while chemical isolation utilizes specific recognition mechanisms to capture the CTCs. These techniques result in low cell damage with a high specificity to facilitate further analysis. Currently, CTC detection has been applied for early diagnosis and prognostic assessment of multiple cancers including lung cancer, liver cancer, colorectal cancer, and prostate cancer.