Circulating Tumor Cells and the “Liquid Biopsy”
In the era of high resolution imaging technologies and advancements in treatment therapies, metastatic cancer is still often considered a fatal disease. The breaking away of cells from the primary solid tumor and their spread to other parts of the body via the bloodstream often correlates with poor prognosis. Such circulating tumor cells (CTCs) have been detected in the peripheral blood of cancer patients as early as 1869 and have now been observed for many various types of metastatic disease. It is now clear that CTCs may serve as a surrogate to tumor biopsy and enable determination of optimized (personalized) treatment benefit based on the biology of individual tumors. As result, methods for noninvasive recovery of CTCs from cancer patient's blood and the application of tumor biomarkers to better elucidate molecular pathways for therapy selection have been the focus of numerous studies and clinical trials.
CTCs are Rare and Heterogeneous
Despite the obvious importance of CTCs, incorporation into standard screening and treatment guidelines has been challenging due to a number of factors. Firstly, CTCs are extremely rare in comparison to hematologic cells (about 1 tumor cell per 1 billion blood cells), which make them difficult to isolate. Second, though many strategies have been developed to allow recovery of CTCs for enumeration, few enable subsequent molecular analysis of only the CTCs. Heterogeneity among CTCs can exist, making downstream analysis unreliable when pooling cells following recovery from blood. Finally, it is now apparent that perhaps the important CTCs are not only epithelial in origin but also mesenchymal as result of EMT (Epithelial to Mesenchymal Transition), a mechanism of the metastatic process. Thus, any sample preparation strategies limiting evaluation to epithelial CTCs may result in inaccurate interpretation of disease state.
CTCs have Clinical Utility
Multiple platforms exist today reporting recovery of CTCs based on immuno-phenotypic characteristics (e.g. EpCAM+/Cytokeratin+/CD45- staining). A positive correlation between the frequency of CTCs and patient survival has been demonstrated for metastatic breast cancer (Cristofanilli et al., 2014 Breast Cancer), metastatic prostate cancer (deBono et al., 2014 Am Soc Clin Oncol Educ Book), and metastatic colorectal cancer. However, to-date, the clinical detection of CTCs in blood of patients has been largely limited to the enumeration of epithelial derived CTCs by means of antibody-based capture followed by differential fluorescent staining to distinguish CTCs from normal cells as a prognostic indicator of patient risk. Efforts to go beyond enumeration of CTCs to include the molecular characterization of the circulating tumor cells is expected to improve the clinical utility of CTCs.
Discover Every Cell’s Story
The DEPArray platform bridges the gap between current enrichment methods and what is needed for downstream molecular applications to effectively characterize tumor cells from peripheral blood. The ability to sort and recover individual cells, or pools of common phenotypes, overcomes the limitations associated with analysis of enriched samples that are compromised by the presence of normal peripheral blood cells intermixed with heterogeneous tumor (CTC) cells. When combined with single cell whole genome amplification (see Ampli1 WGA Kit) more sensitive and reliable profiling of tumor cell populations recovered from a simple blood draw can be achieved.
CTC Application Workflow
The complete CTCs validated workflows - which inludes Ampli1 WGA and Ampli1 LowPass Kit - will drive you through the processing of CTC DNA for mutation detection and Copy Number Aberration by NGS analysis.
To review publications and resource references, please visit our Publications page.