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Gene expression profiling of circulating tumor cells in breast cancer

ABSTRACT: CTCs are the purpoted intermediates of metastatic dissemination and are likely to contain cellular clones responsible for disease progression representing a preferred source for identification of druggable targets. Unfortunately a molecular characterization of CTCs is seriously hampered by their low numbers even in metastatic patients and by the elevated contamination of isolated CTCs with leukocytes. With the final goal of providing a reliable assay allowing to obtain valuable information on CTC features in the clinical setting, we have developed a method based on capture with beads linked to EpCAM and to MUC1 exploiting a commercially available kit and performing an extensive gene expression profiling with the DASL platform. For spike-in experiments, low pre-defined numbers of cells derived from established breast cancer cell lines (MCF7 and MDA-MB-468) were spiked into 5 mL of whole blood of healthy donor and captured using AdnaTest EMT-1/StemCell Select kit. Total RNA isolated from the captured cells together with total RNA isolated from the same in vitro cultered cells was processed in duplicate or triplicate onto Illumina Whole-Genome DASL HT platform. Finally, gene expression profiling was carried out on CTCs isolated from blood of 7 patients with advanced breast cancer. According with the characteristics of the study, data normalization was not applicable

ORGANISM(S): Homo sapiens

SUBMITTER: Fina E

PROVIDER: S-ECPF-GEOD-55470 | biostudies-other | 2015 Jan

REPOSITORIES: biostudies-other

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Project description:The presence of circulating tumor cells (CTCs) in the blood of ovarian cancer patients was shown to correlate with decreased overall survival, whereby CTCs with epithelial-mesenchymal-transition (EMT) or stem-like traits are supposed to be involved in metastatic progression and recurrence. Thus, investigating the transcriptional profiles of CTCs might help to identify therapy resistant tumor cells and to overcome treatment failure. For this purpose, we established a multi-marker panel for the molecular characterization of single CTCs, detecting epithelial (EpCAM, Muc-1, CK5/7), EMT (N-cadherin, Vimentin, Snai1/2, CD117, CD146, CD49f) and stem cell (CD44, ALDH1A1, Nanog, SOX2, Notch1/4, Oct4, Lin28) associated transcripts. First primer specificity and PCR-performance of the multiplex-RT-PCRs were successfully validated on genomic DNA and cDNA isolated from OvCar3 cells. The assay sensitivity of the epithelial panel was evaluated by adding defined numbers of tumor cells into the blood of healthy donors and performing a subsequent immunomagnetic tumor cell enrichment (AdnaTest OvarianCancerSelect), resulting in a 100% concordance for the epithelial markers EpCAM and Muc-1 to the AdnaTest OvarianCancerDetect. Additionally, by processing blood from ovarian cancer patients, high assay sensitivity could be verified. In blood of healthy donors no signals for epithelial markers were detected, for EMT and stem cell markers, however, signals were obtained mainly originating from leukocytes which calls for single cell analysis. To that aim by using the ovarian cancer cell line OvCar3, we successfully established a workflow enabling the characterization of single CTCs. It consists of a density gradient-dependent enrichment for nucleated cells, a depletion of CD45-positive cells of hematopoietic origin followed by immunofluorescent labeling of CTCs by EpCAM and Muc-1. Single CTCs are then isolated by micromanipulation and processed for panel gene expression profiling. Finally, fifteen single CTCs from three ovarian cancer patients were analyzed and found to be positive for stem cell (CD44, ALDH1A1, Nanog, Oct4) and EMT markers (N-cadherin, Vimentin, Snai2, CD117, CD146). Albeit, inter-cellular and intra/inter-patient heterogeneity and co-expression of epithelial, mesenchymal and stem cell transcripts on the same CTC was observed. We have established a robust workflow to perform sensitive single cell panel gene expression analysis without the need of pre-amplification steps. Our data point towards a heterogeneous expression of stem cell and EMT associated transcripts in ovarian cancer CTCs.

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Gene expression profiling of circulating tumor cells in breast cancer

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