Establishment and Characterization of a CTC Cell Line from Peripheral Blood of Breast Cancer Patients

Background: Circulating tumor cell (CTC)-based patient-derived cells are ideal models for investigating the molecular basis of cancer. However, the rarity and heterogeneity of CTCs as well as the difficulties of primary culture limit their practical application. Establishing efficient in vitro culture methods and functionally characterizing CTCs is essential for cancer studies. To this end, we developed an experimental protocol for the isolation, expansion, and identification of breast cancer CTCs. Methods: The CTC-3 cell line was established from peripheral blood cells of a breast cancer patient. A karyotype analysis was performed. The molecular profile was assessed by flow cytometry, quantitative real-time PCR, and western blot. The characteristics of tumors formed by CTC-3 cells were evaluated by cell growth and tumor sphere formation assays and in a mouse xenograft model. The tumors were analyzed by immunohistochemistry, immunofluorescence analysis, and hematoxylin and eosin staining. Results: The CTC-3 cell line showed more aggressive growth both in vitro and in vivo than the widely used MCF-7 breast cancer cell line. CTC-3 cells were also more resistant to chemotherapeutic agents, and gene profiling indicated higher expression levels of the epithelial-to-mesenchymal transition and stemness markers as compared to MCF-7 cells. Conclusions: CTC-3 cells are a better model for investigating the malignant behavior of breast cancer than existing cell lines.