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.

• Klíčová slova
• Estrogen receptor (ER), circulating tumor cells, gene expression, human epidermal growth factor receptor 2 (HER2), metastatic breast cancer,
• MeSH
• chemorezistence MeSH
• dospělí MeSH
• Kaplanův-Meierův odhad MeSH
• lidé středního věku MeSH
• lidé MeSH
• metastázy nádorů MeSH
• nádorové biomarkery * MeSH
• nádorové cirkulující buňky metabolismus   patologie   MeSH
• nádory prsu genetika   patologie   terapie   MeSH
• progrese nemoci MeSH
• receptor erbB-2 genetika   MeSH
• receptory pro estrogeny genetika   MeSH
• regulace genové exprese u nádorů * MeSH
• senioři nad 80 let MeSH
• senioři MeSH
• staging nádorů MeSH
• stanovení celkové genové exprese MeSH
• transkriptom MeSH
• Check Tag
• dospělí MeSH
• lidé středního věku MeSH
• lidé MeSH
• senioři nad 80 let MeSH
• senioři MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• nádorové biomarkery * MeSH
• receptor erbB-2 MeSH
• receptory pro estrogeny MeSH