Molecular Characterization of Single Circulating Tumor Cells – Challenges and Promise for Translation to the Clinic

Molecular Characterization of Single Circulating Tumor Cells – Challenges and Promise for Translation to the Clinic

Abstract
Circulating Tumor Cells (CTCs) shed from primary tumors and metastases represent a surrogate material of the tumor that can be analyzed at any time with a minimal invasive blood draw to obtain information about disease progression. Since a biopsy of the primary tumour or metastatic lesion alone is not always able to recapitulate the molecular characteristics of the entire tumour, sequentially collected CTCs could potentially reveal the complete disease landscape for real-time monitoring of response to therapy, which remains a need unmet in current clinical practice using tissue biopsy.
In recent years, genomic and transcriptomic analysis of CTCs has been increasingly used in oncology clinical trials as an essential tool in precision medicine for real-time monitoring of tumour evolution and for identifying patients who might benefit from additional treatments or targeted therapies or who develop resistance to specific therapies.
However, due to their rarity, the characterization of CTCs is a technically demanding multi-step process that starts with enrichment, followed by identification and isolation and whole genome/transcriptome amplification prior to the molecular analysis itself (mainly represented by NGS). Thus, the transition from bulk to single cell analysis on patient-derived CTCs requires technologically-advanced equipment, experienced professionals and a level of workflow standardization that has not yet been fully achieved.Different approaches are available for every single step, each with advantages and disadvantages, and their numerous combinations in dedicated CTC workflows require careful verification and validation for each individual clinical purpose.The aim of this presentation is to highlight the potential of molecular analysis of individual CTCs and the pitfalls associated with their manipulation, especially in the pre-analytical phase. Examples of workflows used by our group in the study of CTCs at the single cell level in different tumour types (i.e. breast, colon and thyroid cancer) and with different clinical aims will be given.