Liquid Biopsies: Genotyping Circulating Tumor DNA

Abstract

Genotyping tumor tissue in search of somatic genetic alterations for actionable information has become routine practice in clinical oncology. Although these sequence alterations are highly informative, sampling tumor tissue has significant inherent limitations; tumor tissue is a single snapshot in time, is subject to selection bias resulting from tumor heterogeneity, and can be difficult to obtain. Cell-free fragments of DNA are shed into the bloodstream by cells undergoing apoptosis or necrosis, and the load of circulating cell-free DNA (cfDNA) correlates with tumor staging and prognosis. Moreover, recent advances in the sensitivity and accuracy of DNA analysis have allowed for genotyping of cfDNA for somatic genomic alterations found in tumors. The ability to detect and quantify tumor mutations has proven effective in tracking tumor dynamics in real time as well as serving as a liquid biopsy that can be used for a variety of clinical and investigational applications not previously possible.

Molecular analysis of single circulating tumour cells following long‐term storage of clinical samples

“…We and others have previously demonstrated the potential clinical benefit of molecular characterization of CTCs following single‐cell isolation from patient blood samples (Carter et al ., 2017; Diaz and Bardelli, 2014; Fusi et al ., 2013; Rothwell et al ., 2016). To facilitate single CTC isolation and analysis, we have established a simple yet robust workflow, which allows banking of either the entire CellSearch ® sample prior to cell isolation, or individual CTCs after DEPArray™ single‐cell isolation (Fig.…”

“…Both CTCs and circulating free DNA (cfDNA) can be readily obtained from a simple peripheral blood draw and together represent a ‘liquid biopsy’ that holds considerable potential for providing biomarkers that can improve cancer patient management (Carter et al ., 2017; Diaz and Bardelli, 2014; Fusi et al ., 2013; Krebs et al ., 2014; Rothwell et al ., 2016). The isolation and characterization of single tumour cells from the circulation can give an insight into the heterogeneity and genetic status of tumours, which has been associated with prognosis (Carter et al ., 2017; Casasent et al ., 2017; Navin, 2015).…”

“…The molecular characterization of tumours also has the potential to give insight into mechanisms of resistance to therapies and tumour heterogeneity (Burrell and Swanton, 2014; Carter et al ., 2017; Casasent et al ., 2017; Jamal‐Hanjani et al ., 2015; Navin, 2015). Circulating tumour cells (CTCs) found in the blood of patients with cancer are being evaluated for clinical utility as a liquid biopsy that can facilitate molecular characterization of the patient's disease (Carter et al ., 2017; Diaz and Bardelli, 2014; Fusi et al ., 2013; Krebs et al ., 2014; Rothwell et al ., 2016). Use of a simple blood draw and CTC analysis has the added benefit of ease of sample collection as well as the possibility of repeat sampling.…”

Neueste technologische Entwicklungen für die Analyse von zirkulierender Tumor-DNA

“…Liquid Biopsy, womit u.a. die Analyse von zirkulierender Tumor-DNA (ctDNA) sowie zirkulierenden Tumorzellen (CTCs) bezeichnet wird, ist seit Längerem bekannt und in zahlreichen Übersichtsarbeiten umfassend diskutiert [1][2][3][4][5]. Arbeiten der letzten Jahre haben bewiesen, dass ctDNA die molekulargenetischen Veränderun-gen von Tumoren und deren Metastasen reflektiert und daher als Surrogatmarker für das gesamte Tumorgenom angesehen werden kann.…”

Biopsies liquides, une révolution en cancérologie ?

“…Ce type d'approche rencontre actuellement un large écho en cancérologie [3], et donne déjà lieu à plusieurs applications commerciales : il semble donc que le moment soit venu de faire un nouveau point sur cette technologie, sur ses performances et ses domaines d'application.…”