Molecular profiling of single circulating tumor cells with diagnostic intention

Abstract

Several hundred clinical trials currently explore the role of circulating tumor cell ( CTC ) analysis for therapy decisions, but assays are lacking for comprehensive molecular characterization of CTC s with diagnostic precision. We therefore combined a workflow for enrichment and isolation of pure CTCs with a non‐random whole genome amplification method for single cells and applied it to 510 single CTC s and 189 leukocytes of 66 CTC ‐positive breast cancer patients. We defined a genome integrity index ( GII ) to identify single cells suited for molecular characterization by different molecular assays, such as diagnostic profiling of point mutations, gene amplifications and whole genomes of single cells. The reliability of > 90% for successful molecular analysis of high‐quality clinical samples selected by the GII enabled assessing the molecular heterogeneity of single CTC s of metastatic breast cancer patients. We readily identified genomic disparity of potentially high relevance between primary tumors and CTC s. Microheterogeneity analysis among individual CTC s uncovered pre‐existing cells resistant to ERBB 2 ‐targeted therapies suggesting ongoing microevolution at late‐stage disease whose exploration may provide essential information for personalized treatment decisions and shed light into mechanisms of acquired drug resistance.