Single cell transcriptional profiling of Circulating Tumor Cells (CTCs): Intra-patient heterogeneity of endocrine resistant and phenotypic markers
20 September 2018 (online)
Understanding the heterogenous CTC biology might help to answer key issues addressing the complexity of metastatic processes and therapy resistance. Here we demonstrate single CTC transcriptional profiling, providing early insight into intra-patient CTC heterogeneity and allowing comparisons to breast cancer cell lines widely used for examining therapy resistance.
A PCR panel consisting of 30 different endocrine resistance and phenotypic markers was designed and tested for single cell profiling by using different breast cancer cell lines (MCF-7, MCF-7/TAMR and MDA-MB-231). In addition, CTCs were enriched from a diagnostic leukapheresis product obtained from a patient suffering from metastatic breast cancer resistant to endocrine therapy using the ParsortixTM system. RNA of single uncultured and cultured CTCs was extracted, reversely transcribed into cDNA and subsequently pre-amplified. Next, gene expression profiles were generated by multiplex real-time PCR.
Multimarker analysis was possible in single cells with intense signals of KR19 and ACTB (61,5% of cell lines (n = 13), 17,9% of uncultured CTCs (n = 39) and 33% of cultured CTCs (n = 15)). We found that single cell line cells and pools of 5 cells reproducibly clustered together. Moreover, single cell transcriptomic profiles of each cell line were consistent with penotypic and endocrine biomarker patterns (e.g. ER, HER2, VIM). Gene expression profiles of CTCs and cultured CTCs revealed intra-patient heterogeneity with clustering into subgroups concerning phenotypic (EpCAM, CD44) and endocrine markers (ER, HER2).
Multimarker RNA profiling of enriched single CTCs and cultured CTCs may provide important insights into intra-patient tumoral heterogeneity relevant for therapy resistance.