Circulating Tumor Cells (CTC) Enumeration

Background

Circulating tumor cells (CTCs) are tumor cells that have sloughed off the primary tumor and extravasate into and circulate in the blood. Although CTCs originate from the primary tumor, they are distinct from primary tumor cells, with EMT transition properties that help them break free from the primary tumor and facilitate intravasation into the bloodstream, dissemination in clusters of CTCs to increase metastatic potential, and exhibit stemness features that enhance their ability to initiate metastasis. Understanding of the metastatic cascade of CTCs has tremendous potential for the identification of targets against cancer metastasis. The enumeration of CTCs has emerged as a simple and effective biomarker with many applications in cancer research for prognosis and treatment. Moreover, they represent an entire cancer-derived cell population, providing a potent tool to study tumor heterogeneity and progression of the disease at various stages.

Fig. 1: Biological features of circulating tumor cell clusters

Epithelial–Mesenchymal Transition (EMT)

EMT provides a potential mechanistic basis for how CTC intravasate in primary tumors to reach the circulation, and seed tumor implants at distant secondary sites. EMT is associated with the increased tumor cell motility and an invasive phenotype. These changes are typically characterized by loss of E-Cadherin expression and subsequent translocalization of β-catenin from the cell membrane into the nucleus, increased expression of vimentin, production of matrix metalloproteinase enzymes, and upregulation of various EMT-inducing transcription factors such as Twist, Snail, and Slug. In a study of metastatic breast cancer there was at least one of three EMT markers (Akt2, PI3K, and Twist1), assessed by RT-PCR, to be expressed by the CTC population in 62% of patients harboring CTC. Evaluating CTC expression of EMT markers Twist and vimentin by immunofluorescence, it has been found vimentin/Twist expressing CTC in 77% of early-stage breast cancer patients compared to 100% of patients with metastatic disease.

CTCs Detection

As CTCs are very heterogeneous population, for their detection it is better to use pan-reactive antibodies. On the other hand, when trying to identify a particular source of circulating tumor cells, specific combinations of anti-cytokereatin antibodies are needed. Creative Diagnostics has developed a portfolio of CTCs antibodies can be used for efficient capture, recovery, and analysis of CTCs from liquid biopsy samples, cell culture, and other sample types, to facilitated the clinical applications of CTCs in cancer screening, treatment response monitoring, and prognosis evaluation.

Fig. 3: Fluorescent images of eight CTCs (Hoechst 33342+, F-MNPs+, CD45−) and WBCs (Hoechst 33342+, CD45+) from breast cancer patients' blood samples.
Ref: Hepel, Maria. "Magnetic nanoparticles for nanomedicine." Magnetochemistry 6.1 (2020): 3.

Fig. 4: Detection of Circulating tumor cells (CTCs) in renal cell carcinoma samples (RCC patient.
Ref: Zhu, Peixuan, et al. "Detection of tumor-associated cells in cryopreserved peripheral blood mononuclear cell samples for retrospective analysis." Journal of translational medicine 14 (2016): 1-12.