Circulating Tumor Cells ( Ctcs )

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Circulating tumor cells (CTCs)
Circulating tumor cells (CTCs), represent tumor cells that contain a heterogeneous populace of cells, including apoptotic tumor and viable tumor cells that have shed into the vasculature or lymphatics from a primary or metastatic tumor and are carried around the body in the circulation by undergoing phenotypic changes that are accompanied by a process called as epithelial-mesenchymal transition (EMT) 64-68. Evidence now suggests that the tumors has ability to make their own blood vessels when they reach the size of 1-2 mm3 by inducing angiogenesis or through vasculogenic mimicry, the blood vessels composed of endothelial cells and tumor cells, however, vasculogenic mimicry form blood vessels without
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However, it is not necessarily always associated with metastasis, as only 0.01% of CTCs takes part in metastasis92, 94, 95. Moreover, highly sensitive, single cell investigation showed marked heterogeneity of individual CTCs for protein expression and localization, and the CTCs reflected the character of both the primary biopsy and the transformations seen in the metastatic sites96, 97, which corresponds with the evidence of “seed and soil” hypothesis98-100.
Amassing proof has demonstrated that CTCs can be utilized as a biomarker to non-invasively supervise cancer progression and provide direction to monitor the treatment101-103. The American Society of Clinical Oncology (ASCO) approved CTCs as a tumor marker for breast cancer in 2007104, 105.
Nevertheless, CTCs detection, identification, enumeration and molecular characterization are very challenging, since CTCs are uncommon in peripheral blood of patients (that is, 1–100 CTCs among billions of normal cells) with a half-life between 1 to 2.4 hours and due to its fragile nature it tends to degrade when collected in standard blood collecting tubes106-109, 110, 111.
CTCs being heterogeneous population of cells, CTCs can be positively or negatively enriched on the basis of: 1. Physical characteristics (that is, cell diameter >15 μm, nuclear-cytoplasmic ratio >0.8, electric charges, deformability, the hyperchromatic nuclei, sunken
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