Circulating Tumor Cells: Enrichment and Genomic Applications

Recent technical advances have led to an increased interest in the detection and molecular characterization of circulating tumor cells (CTCs). Evaluation of CTCs carries great potential as a tool in cancer patient management and prognostication. Numerous clinical trials on early and metastatic cancer are employing CTCs to evaluate the efficacy of systemic therapy. There is also an increasing interest in using CTCs for detailed molecular and cellular characterization of both well-characterized and novel biomarkers. However, technical challenges have limited the opportunity to deeply probe these rare events, particularly as they occur in a background of millions of normal cells. More recently, the identification of tumor stromal cells, such as cancer-associated fibroblasts (CAFs) and tumor-associated macrophages (TAMs), circulating in cancer patient blood along with and in association with CTCs has both opened doors to understanding the roles of CTC-associated cells in metastasis as well as raised questions about how to capture and characterize these circulating stromal cells (cStCs). Better characterization of both CTCs and CTC-associated circulating cells should clearly lead to a better understanding of cancer progression, the effects of therapy, and the identification of novel therapeutic targets. CTC and CTC-cStC evaluation is expected to become more widely used in both clinical and research settings.