Clinical Applications of and Challenges in Single-Cell Analysis of Circulating Tumor Cells

Technological advancements in next-generation sequencing are continually changing the landscape of genomic, transcriptomic, and epigenetic research at the single-cell level. These technologies have been used to detect and analyze circulating tumor cells (CTCs) at the molecular level and provide a new approach for the management of cancer patients. A series of unanticipated discoveries, including the heterogeneity of cancer cell populations, new driver mutations responsible for the resistance of tumors to chemotherapy, and the mechanism of tumor metastasis, have been made using single CTC sequencing. CTC detection has been used in cancer diagnosis and monitoring and in determining the prognosis of cancer patients. Traditional treatment for cancer patients is universal and does not consider genetic variations among patients, but in the era of precision medicine, giving the right drug to the right patient at the right time is the core philosophy. In this study, we review the fundamental principles of CTC isolation and single-cell sequencing and discuss recent progress in their application in both basic research and clinical fields and describe the current challenges.