In Vitro and In Vivo Models of Circulating Tumor Cells

The ability to detect CTCs in the peripheral blood of cancer patients is a major challenge, and many interesting technologies have been developed in recent years. CTCs can function as potential real-time decision-making guides for selecting appropriate therapies during the course of the disease or for the development and testing of new treatments. However, these cells are extremely rare and require technology that is sensitive and specific enough. One of the methods that may be useful for the characterization of these cells is the development of CTC-derived xenografts (CDXs) or CTC-derived cell lines at relevant times during the progression of the disease. Xenograft models derived from CTC (CDX) and ex vivo cultures have emerged as treatable systems for exploring tumor-initiating cells (TICs). In addition, these models have been shown to be predictive of clinical outcomes and are being used for preclinical evaluation medicines, identification of biomarkers, biological studies, and personalized medicinal strategies. In this chapter, we discuss the basic knowledge of CTCs and demonstrate some of the existing CTC-derived models, including in vivo CDXs and PDXs and in vitro functional culture assays in different types of cancer. We also highlight the important discoveries that helped to uncover new insights into the biology of CTC and new therapeutic strategies.