CTCs in early detection of Breast Cancer versus metastasized disease
By Priyanka Varma
Aug. 25th, 2022
CTCs or Circulating Tumor Cells are nucleated with cell like morphology, which stain positive for cytokeratin, and are recognized by the antibodies C11 and A53-B/A2 . They are considered a potential non-invasive alternative diagnostic tool (as well as a prognostic marker) to invasive tissue biopsy. Next Generation Sequencing (NGS) have identified clonal evolution not only in primary tumor but also in metastatic foci, owing to hematogenous dissemination of cell clones to distant organs.
Biomarkers on CTCs for breast cancer have been analyzed and compared with biomarkers on primary tumor and metastatic sites . In breast cancer, CTCs are present either as single cells or multicellular aggregates, which have higher (23-50 fold) metastatic potential. The increased metastatic capability of multicellular aggregate CTCs is owing to their highly differential expression of the prominent intercellular junction component, plakoglobin [3, 4].The CTCs invade through extracellular matrix and disseminate via blood stream to distant organs. However, not all CTC’s develop macroscopic metastatic foci as not all cells complete the entire metastatic cascade described above .
There are several platforms available to capture CTC’s physical aspects and immunological aspects. One such FDA approved platform is Cell Search by Veridex, based on magnetic EpCAM Ab based separation. It utilizes identification of CTC by CK8,18,19+and CD45-, of 4 µm and DAPI+ [2, 5, 6]. However, the EpCAM methodology can only capture EpCAM positive cells and hence owing to the heterogeneity inexpression of tumor, those having low or no EpCAM evade capture on this test. Non epithelial tumors, epithelial tumors with low or no expression of EpCAM or cells which have undergone epithelial to mesenchymal transition will not be captured by this test as EpCAM is an epithelial marker-based test . Tumor cell enrichment methods to identify CTCs utilizing differences in cell density, cell size is faster, more efficient and can identify a broader range of tumors including non-epithelial tumors and non-EMA expressing cells .
To detect CTC clusters at an earlier stage of breast cancer, some studies employed customized liquid handling platform and smart surface bio surface slides for automated cell seeding and fixation to reduce shear stress and were successful in providing proof of concept evidence of presence of CTC clusters at an earlier stage of breast cancer (IA, IIA, IIIA, IIB) at 75%sensitivity and 97% specificity for all subtypes (Luminal A-like, Luminal B-like, HER-2, Triple negative) and 81% sensitivity for luminal subtypes .
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