Abstract 1591: Comprehensive molecular profiling of circulating tumor cells from metastatic breast cancer patients

Abstract

Abstract Background: Recent enumeration studies on CTCs have demonstrated the clinical value of these cells. The molecular biology of CTCs, however, remains poorly understood. Methods: We performed RNA and DNA profiling of CTCs from metastatic breast cancer (MBC) patients. 244 blood samples from 162 MBC patients were subjected to immunomagnetic enrichment and fluorescence activated cell sorting (IE/FACS) to isolate highly pure CTCs. Microfluidic-based multiplex QPCR analysis was utilized to determine the expression levels of 64 cancer-related genes. Parallel genome-wide copy number analysis by array comparative genomic hybridization was also performed on CTCs isolated from the same enriched blood samples. Results: Transcriptional analysis of CTCs was successfully performed in 151 samples from 105 patients. We observed the up-regulation of several genes including CCND1, EPCAM, KRT7 and MUC1 and the down-regulation of hematopoietic-related genes including PTPRC (CD45) and CD68 (adjusted p <0.001) in CTCs. Clustering analysis of expression profiles revealed three CTC clusters, one containing both subtypes basal (ESR1-low) and normal-like (ESR1-low, CAV1/VIM-high) and two other clusters containing luminal subtype (ESR1-high). A subset of CTCs expressed epithelial-mesenchymal transition genes, however, genes for stem cellness were not generally expressed. Serial CTC expression profiling in 28 patients demonstrated changes in expression over time. Exploratory single CTC expression analysis revealed cell-to-cell heterogeneity. Parallel genome-wide copy number analysis in matched CTCs from 49 patients revealed gains (e.g. 1q and 8q), losses (e.g., 8p and 16q), and focal amplifications (e.g. on 8q and 11q including CCND1) that are frequently observed in primary breast cancers. We also observed three copy number clusters with varying levels of genomic aberrations. Up-regulation of CCND1 and ERBB2 in CTCs was associated with increased level of genomic instability. Conclusions: Parallel gene expression and copy number profiling provided novel insights on the biology of CTCs. Molecular characterization of CTCs may shed further light on the biology of metastasis and disease progression. Citation Format: Mark Jesus Mendoza Magbanua, Louai Hauranieh, Ritu Roy, Praveen Pendyala, Eduardo Sosa, Janet Scott, Hope Rugo, John Park. Comprehensive molecular profiling of circulating tumor cells from metastatic breast cancer patients. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1591. doi:10.1158/1538-7445.AM2015-1591