Investigation of the clonal relationship of EpCAM high-expressing and low-expressing circulating tumor cells

Background Circulating tumor cells (CTCs) are considered as precursors of metastatic spread and can act as prognostic and predictive biomarkers. Their enrichment is mainly based on immunomagnetic technologies relying on antibodies against EpCAM. Although it was shown that an EpCAM low-expressing fraction is not captured by this, knowledge about its clinical relevance and relation to EpCAM-positive CTCs is still lacking.

Therefore, we developed an immunomagnetic assay to enrich CTCs EpCAM-independently to compare EpCAM high- and low-expressing CTCs enriched with the same method.

Methods CTCs were enriched from 20 metastatic breast cancer patients’ blood samples using antibodies against the cell surface proteins Trop-2 and CD49f coupled to magnetic particles. The CTCs’ EpCAM expression was determined by fluorescence microscopy. EpCAM high-expressing and low-expressing CTCs were isolated. Their chromosomal aberrations and predictive mutations were analyzed by low pass and targeted next generation sequencing.

Results The application of antibodies against Trop-2 and CD49f showed a synergistic effect in the CTC yield. The correlation of EpCAM-based fluorescence intensities and patients’ survival revealed that patients with EpCAM high-expressing CTCs had a worse overall (p = 0.046) and progression free survival (p = 0.026) compared to EpCAM low-expressing CTCs. EpCAM high- and low-expressing CTCs presented similar chromosomal aberrations and mutations indicating a close evolutionary relationship.

Conclusion Our data indicate that EpCAM high-expressing CTCs are particularly prognostically relevant. However, since EpCAM low-expressing CTCs represent similar genomic clones of the tumor, they could be used as tumor surrogate material and could have relevance if no CTCs are detected EpCAM-dependently.

Interessenskonflikt

Ich erkläre als korrespondierender Autor, dass meine Koautoren mir mitgeteilt haben, dass sie während der letzten 3 Jahre keine wirtschaftlichen oder persönlichen Verbindungen im oben genannten Sinne hatten. Auch ich selbst hatte keine derartigen Verbindungen in den letzten 3 Jahren.

Publication History

Article published online:
21 June 2022