BACKGROUND: Molecular characterization of tumors could be a key to therapeutic decision-making with regards to targeted therapies in castration-resistant prostate cancer (CRPC). A convenient solution may be non-invasive liquid biopsy testing of circulating tumor cells (CTCs). For this reason, CTC-enriched samples obtained by immunomagnetic separation (AdnaTest®) were studied as a source material for high-throughput gene expression analysis using BioMark™. PATIENTS AND METHODS: CTC-enriched samples from 41 CRPC patients previously determined to be CTC positive using the AdnaTest® were retrospectively re-analysed for androgen receptor (AR) messenger RNA (mRNA), using the updated AdnaTest®. Blood samples were drawn two times from each patient: at the time of CRPC diagnosis and after the third docetaxel cycle. A gene expression panel of 27 genes related to CRPC therapeutic decision-making, including AR full length (ARFL) and splice variant 7 (ARV7), was retrospectively analyzed on a BioMark™ platform in 29 of 41 patients. RESULTS: The AdnaTest® detected AR mRNA in three-quarters of CTC-positive samples taken at the time of CRPC diagnosis and after the third docetaxel cycle. AR detection was associated with a shorter disease-specific survival (45.0 vs. 20.4 months) at the time of CRPC diagnosis. ARFL expression at the time of CRPC diagnosis, measured on the BioMark™ platform, was associated with a lower decrease of serum level of prostate-specific antigen (sPSA) (p = 0.029), i.e., worse therapy response. ARV7 was found in 38% of the ARFL--positive samples at both analyzed timepoints. CONCLUSION: Detection of AR expression by AdnaTest® in CTC-enriched samples may help predict patients' survival. These AdnaTest® CTC-enriched samples can be used in a high-throughput quantitative polymerase chain reaction (qPCR) analysis of gene expression, provided that the specificity of the assay for each individual gene is properly validated. The BioMark™ platform can be used for the simultaneous detection of ARFL and ARV7 and other genes in CTC-enriched samples from CRPC patients.

• MeSH
• Genetic Testing methods   MeSH
• Immunomagnetic Separation MeSH
• Real-Time Polymerase Chain Reaction MeSH
• Middle Aged MeSH
• Humans MeSH
• Biomarkers, Tumor * MeSH
• Neoplastic Cells, Circulating metabolism   pathology   MeSH
• Prostatic Neoplasms, Castration-Resistant diagnosis   genetics   MeSH
• Follow-Up Studies MeSH
• High-Throughput Screening Assays MeSH
• Aged, 80 and over MeSH
• Aged MeSH
• Gene Expression Profiling * methods   MeSH
• Transcriptome MeSH
• Check Tag
• Middle Aged MeSH
• Humans MeSH
• Male MeSH
• Aged, 80 and over MeSH
• Aged MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Biomarkers, Tumor * MeSH

Resistance to systemic therapy is a major problem in metastatic breast cancer (MBC) that can be explained by initial tumor heterogeneity as well as by evolutionary changes during therapy and tumor progression. Circulating tumor cells (CTCs) detected in a liquid biopsy can be sampled and characterized repeatedly during therapy in order to monitor treatment response and disease progression.Our aim was to investigate how CTC derived gene expression of treatment predictive markers (ESR1/HER2) and other cancer associated markers changed in patient blood samples during six months of first-line systemic treatment for MBC. CTCs from 36 patients were enriched using CellSearch (Janssen Diagnostics) and AdnaTest (QIAGEN) before gene expression analysis was performed with a customized gene panel (TATAA Biocenter).Our results show that antibodies against HER2 and EGFR were valuable to isolate CTCs unidentified by CellSearch and possibly lacking EpCAM expression. Evaluation of patients with clinically different breast cancer subgroups demonstrated that gene expression of treatment predictive markers changed over time. This change was especially prominent for HER2 expression.In conclusion, we found that changed gene expression during first-line systemic therapy for MBC could be a possible explanation for treatment resistance. Characterization of CTCs at several time-points during therapy could be informative for treatment selection.

• Keywords
• Estrogen receptor (ER), circulating tumor cells, gene expression, human epidermal growth factor receptor 2 (HER2), metastatic breast cancer,
• MeSH
• Drug Resistance, Neoplasm MeSH
• Adult MeSH
• Kaplan-Meier Estimate MeSH
• Middle Aged MeSH
• Humans MeSH
• Neoplasm Metastasis MeSH
• Biomarkers, Tumor * MeSH
• Neoplastic Cells, Circulating metabolism   pathology   MeSH
• Breast Neoplasms genetics   pathology   therapy   MeSH
• Disease Progression MeSH
• Receptor, ErbB-2 genetics   MeSH
• Receptors, Estrogen genetics   MeSH
• Gene Expression Regulation, Neoplastic * MeSH
• Aged, 80 and over MeSH
• Aged MeSH
• Neoplasm Staging MeSH
• Gene Expression Profiling MeSH
• Transcriptome MeSH
• Check Tag
• Adult MeSH
• Middle Aged MeSH
• Humans MeSH
• Aged, 80 and over MeSH
• Aged MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Biomarkers, Tumor * MeSH
• Receptor, ErbB-2 MeSH
• Receptors, Estrogen MeSH