Gene Expression Signatures in Circulating Tumor Cells Correlate with Response to Therapy in Metastatic Breast Cancer

BACKGROUND: Circulating tumor cells (CTCs) are thought to be an ideal surrogate marker to monitor disease progression in metastatic breast cancer (MBC). We investigated the prediction of treatment response in CTCs of MBC patients on the basis of the expression of 46 genes. METHODS: From 45 MBC patients and 20 healthy donors (HD), 2 x 5 mL of blood was collected at the time of disease progression (TP0) and at 2 consecutive clinical staging time points (TP1 and TP2) to proceed with the Adna Test EMT-2/StemCellSelect (TM) (QIAGEN). Patients were grouped into (a) responder (R) and nonresponder (NR) at TP1 and (b) overall responder (OR) and overall non-responder (ONR) at TP2. A 46-gene PCR assay was used for preamplification and high-throughput gene expression profiling. Data were analyzed by use of GenEx (MultiD) and SAS. RESULTS: The CTC positivity was defined by the fourgene signature (EPCAM, KRT19, MUC1, ERBB2 positivity). Fourteen genes were identified as significantly differentially expressed between CTC + and CTC - patients (KRT19, FLT1, EGFR, EPCAM, GZMM, PGR, CD24, KIT, PLAU, ALDH1A1, CTSD, MKI67, TWIST1, and ERBB2). KRT19 was highly expressed in CTC + patients and ADAM17 in the NR at TP1. A significant differential expression of 4 genes (KRT19, EPCAM, CDH1, and SCGB2A2) was observed between OR and ONR when stratifying the samples into CTC + or CTC -. CONCLUSIONS: ADAM17 could be a key marker in distinguishing R from NR, and KRT19 was powerful in identifying CTCs. (C) 2017 American Association for Clinical Chemistry