Abstract 372: Expression profiling of circulating tumor cells: A prognostic and predictive biomarker in metastatic breast cancer

Abstract

Abstract Background: Circulating tumor cells (CTCs) are discussed to be an ideal surrogate marker to monitor disease progression in metastatic breast cancer (MBC) since response to therapy can only be assessed retrospectively after a therapy strategy has already failed. Here we established a new profiling method to characterize the heterogeneous CTC population and investigated if it is possible to predict treatment response based on expression of 46 genes in CTCs of MBC patients. Materials and Methods: 2×5 ml blood of 45 MBC patients was collected at the time of disease progression (T0) and at two consecutive clinical staging (T1 and T2) after 8-12 weeks of chemo-, hormone or antibody therapy for the detection of CTCs applying positive immunomagnetic selection targeting EpCAM, EGFR and HER2 using the AdnaTest EMT-2/Stem Cell Select (AdnaGen GmbH, Germany). Patients were classified into responders and non-responders at the time of clinical staging according to RECIST criteria. PCR assays targeting 46 selected transcript comprising breast cancer, stem cell, EMT, and references markers were designed and extensively optimized for a workflow based on pre-amplification and high throughput profiling. Each sample was profiled in duplicates with the full set of markers including also ValidPrime to correct for genomic background and InterPlate Calibrator to even out variations between runs. The entire workflow was validated to establish excellent technical reproducibility from sample collection through extraction, pre-amplification and analysis. Measured data were analyzed using parametric as well as non-parametric statistics with GenEx and SAS. qPCR as well as technical reads were normalized using the average expression of the reference genes B2M and ActB. Results: A number of genes, including ADAM17, CD24L4, EPCAM, KRT19, MTOR, HER2, TOP2A, and CD44 were differentially expressed in MBC patients (n = 45) as compared to healthy controls (n = 20). A group of non-responders could be identified based on gene expression. Interestingly, expression of ADAM17 (tumor necrosis factor-α-converting enzyme) differed significantly when responders were compared with non-responders at T1 (p = 0.000567). Conclusion: It is possible to distinguish MBC patients from healthy controls based on the expression of the genes investigated. Preliminary results indicate that ADAM17 is a key marker, distinguishing responders from non-responders. For more detailed analysis, it is desirable to build up a larger patient cohort in order to correlate gene expression profiles of CTC enriched samples to a given therapy for individualized treatment. Citation Format: Maren Bredemeier, Mikael Kubista, Robert Sjöback, Marie Jendrichova, Eva Rohlova, Vednula Novosadova, Katarina Kolostova, Siegfried Hauch, Bahriye Aktas, Mitra Tewes, Rainer Kimmig, Sabine Kasimir-Bauer. Expression profiling of circulating tumor cells: A prognostic and predictive biomarker in metastatic breast cancer. [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 372. doi:10.1158/1538-7445.AM2015-372