Establishment of a new method for detection of TROP2-positive circulating tumor cells in breast cancer

Trophoblast cell surface antigen 2 (TROP2) overexpression has been demonstrated in several tumor types, including breast cancer (BC). Circulating tumor cells (CTCs) offer a non-invasive, dynamic and real-time detection method. The detection of TROP2 expression in CTCs is significant for predicting BC progression, prognosis and the efficacy of targeted therapy. A quantitative analysis method for TROP2 of CTCs was established using our established TUMORFISHER detection platform based on epithelial cell adhesion molecule (EpCAM), and a new magnetic nanoparticle with TROP2 as the trapping target was developed, named TROP2@MNPs. The developed quantitative analysis of TROP2 was an effective method for accurately identifying the expression of TROP2 in BC cells and CTCs from BC patients, which was consistent with the data obtained by immunohistochemical (IHC) analysis. The established TROP2@MNPs could specifically capture TROP2-positive BC cells, and the capture efficiency was closely related to the expression of TROP2 in CTCs. Notably, the TROP2-based enrichment strategy was found to capture TROP2-expressing CTCs that were missed by the EpCAM-based enrichment strategy. The TROP2-targeting CTC capture platform, TROP2@MNPs, could serve as a liquid biopsy of TROP2 expression in BC patients, providing an important reference for further research on CTC-related diagnosis and individualised treatment employing TROP2-targeting drugs.