Current Understanding in Cancer Treatment and Monitoring Through Identification of Circulating Tumor Cells and Tumor-Derived Extracellular Vesicles

Dear Colleagues,

Cancer has been one of the leading causes of mortality and morbidity for over the past 50 years, second after cardiovascular diseases. Early detection, effective monitoring, and optimal therapy selection are instrumental in bringing cancer from a deadly to a controllable disease. Traditionally, cancer therapy and monitoring have been based on the characteristics of the tumor. More recently, liquid biopsies in blood and molecular diagnostics from other body fluids have been demonstrated to be a non-invasive alternative to effectively detect and monitor cancer through the identification and characterization of cancer biomarkers. Among the multitude of available analytes, this Topical Collection will focus on advancements in classical liquid biopsy analyte circulating tumor cells (CTCs) and will explore the role of tumor-derived extracellular vesicles (tdEVs) for clinical outcome and treatment response.

CTCs are shed from tumors to the circulation and can extravasate in other tissues, originating more tumors. The molecular analysis of the CTCs, which may include their secretome and gene profiling, may be used to select the optimal therapy. Challenges arise from the low frequency of CTCs in blood, limiting the information that captures the biology of the tumors. Complementary to CTCs, cancer markers such as extracellular vesicles derived from the tumor are utilized as biomarkers in liquid biopsies. Cancer cells release particles enclosed by a phospholipid membrane containing biomolecules that can reflect the nature of the parental cells. Such particles include exosomes, microvesicles, oncosomes, and apoptotic bodies, which, being of tumor origin, can be referred to as tumor-derived extracellular vesicles (tdEVs). Such tdEVs might complement CTCs as cancer biomarkers. Challenges in identifying tdEVs in body fluids derive from their small but broad size range, from 30 nm up to 5 µm in diameter, and their low abundance compared to other sub-micrometer particles, for example, in the blood. In addition to diagnosis, cancer biomarkers in body fluids are also important in monitoring cancer treatment response. Therefore, we believe that it is important to detect and characterize CTCs and tdEVs, and this information can help us to better understand cancer progression, cancer metastasis, and will impact diagnosis and treatment of cancer.

This Topical Collection of Cells will cover:

• Current methods to detect cancer biomarkers, including CTCs and tdEVs;
• Molecular characterization of CTCs and tdEVs;
• Role of CTCs and tdEVs in cancer aggressivity and metastasis;
• Clinical application/validation of new CTC and tdEV technologies;
• Correlation of CTCs and tdEVs with clinical outcome;
• Evaluation of CTCs and tdEVs in monitoring cancer treatment response.

Prof. Dr. Leon Terstappen
Dr. Agustin Enciso-Martinez
Dr. Ruchi Bansal
Prof. Dr. Nikolas H. Stoecklein
Collection Editors

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