Detection of Activating Estrogen Receptor Gene (ESR1) Mutations in Single Circulating Tumor Cells

Purpose: Early detection is essential for treatment plans before onset of metastatic disease. Our purpose was to demonstrate feasibility to detect and monitor estrogen receptor 1 (ESR1) gene mutations at the single circulating tumor cell (CTC) level in metastatic breast cancer (MBC). <br /><br />Experimental Design: We used a CTC molecular characterization approach to investigate heterogeneity of 14 hot spot mutations in ESR1 and their correlation with endocrine resistance. Combining the CellSearch^® and DEPArray™ technologies allowed recovery of 71 single CTCs and 12 WBC from 3 ER-positive MBC patients. 40 CTCs and 12 WBC were subjected to whole genome amplification by MALBAC and Sanger sequencing.<br /><br />Results: Among 3 selected patients, 2 had an ESR1 mutation (Y537). One showed two different ESR1 variants in a single CTC and another showed loss of heterozygosity. All mutations were detected in matched cell-free DNA (cfDNA). Furthermore, one had 2 serial blood samples analyzed and showed changes in both cfDNA and CTCs with emergence of mutations in ESR1 (Y537S and T570I), which has not been reported previously.<br /><br />Conclusions: : CTCs are easily accessible biomarkers to monitor and better personalize management of patients with previously demonstrated ER-MBC who are progressing on endocrine therapy. We showed that single CTC analysis can yield important information on clonal heterogeneity, and can be a source of discovery of novel and potential driver mutations. Finally, we also validate a workflow for liquid biopsy that will facilitate early detection of ESR1 mutations, the emergence of endocrine resistance and the choice of further target therapy.

http://ift.tt/2urQLNt