What are Circulating Tumor Cells?

Cancer was the second leading cause of death in the United States in 2020, according to the Centers for Disease Control and Prevention (CDC). The analysis of Circulating Tumor Cells (CTCs) could potentially detect early signs of cancer (leading to early diagnosis), guide treatment, and help us further understand how cancer metastasizes.

CTCs are released into the bloodstream from primary cancer, metastasis, and even from a disseminated tumor cell reservoir. Since CTCs can give rise to new metastatic lesions and metastases are responsible for most cancer-related deaths, analysis of CTCs can be a powerful tool for the non-invasive investigation of cancer cell biomarkers and mutational status.

What Do Circulating Tumor Cells Indicate?

Since CTCs are broken off from a form of primary cancer or tumor cells, they could be an indication of cancer through malignant tumors.

What is the Difference Between Circulating Tumor Cells and Cancer Stem Cells?

Cancer Stem Cells (CSCs), a small subpopulation of cells found within a tumor capable of self-renewability and differentiation, may also play an important role in tumorigenesis as well as within the tumor microenvironment. While the connection between CSCs and CTCs remains to be fully understood, research indicates CSCs are sometimes found within CTCs and could potentially play a role in tumor metastasis. However, more research is still needed to further understand this connection.

Detection of Circulating Tumor Cells Through The Use Of Next-Generation Sequencing (NGS)

There are many ways to capture CTCs, one of which is with liquid biopsy testing. Liquid biopsy is conducted through a blood sample and can detect any pieces of DNA that might have broken off from tumor cells, as well as any cancer cells, that are circulating in the blood. Since liquid biopsy is minimally invasive, multiple blood samples can easily be taken over time to monitor and track cancer and to determine how effective treatment is for that cancer.

Once isolated, CTCs can be studied using Next-Generation Sequencing (NGS) to obtain their genomic profiles. Targeted sequencing of CTCs using amplicon-based NGS panels is an ideal approach because the workflow is simple to implement and requires a minimal amount of input DNA.

Measuring Somatic Mutations from CTCs and Plasma

CTC detection with Paragon’s Cleanplex NGS technology was done in collaboration with RareCyte and the Mayo Clinic. CTCs were visually identified using the CyteFinder® Instrument and were then retrieved with the CytePicker® Module for genomics analysis.

Cells were lysed in a PCR-compatible lysis buffer without whole genome amplification, and the lysate was used to prepare targeted NGS libraries using the CleanPlex OncoZoom Cancer Hotspot Panel. This approach resulted in libraries with excellent and consistent coverage and low error frequencies, enabling efficient and accurate assessment of somatic mutations in CTCs.