TROP2 as Patient-Tailoring but Not Prognostic Biomarker for Breast Cancer

Purpose: Trophoblast cell surface antigen 2 (TROP2) has emerged as a promising target of antibody-drug conjugates (ADCs) for triple-negative breast cancer (TNBC), as well as other breast cancers (BCs). This study aims to investigate the biomarker value of TROP2 for patient-tailoring and prognostic for BC patients, including TNBC. Methods: The levels of TROP2 expression in 404 Chinese BC tissues on tissue microarrays (TMAs) were quantified by immunohistochemistry and their correlations to the clinicopathological factors and the overall survival rate were analyzed. Also, BC cell lines and patient-derived organoids (PDOs) with different TROP2 expression levels were employed to investigate the correlation between TROP2 expression levels and the therapeutic responses to DS001, a TROP2-directed ADC molecule with stable linker and potent payload. Results: TROP2 overexpression was identified in significantly more (P = 0.046) tumor tissues (41.08%, 99/241) than normal adjacent tissues (31.29%, 51/163) from Chinese BC patients, and in significantly more (P = 0.024) TNBC patients (59.38%, 19/32) than in other BC types (38.28%, 80/209). BC cell line with the lowest TROP2 expression level failed to respond to DS001 treatment. The levels of TROP2 expression were determined to be significantly correlated with the potencies of DS001 treatment, but not with the overall survival rates of the patients. Conclusion: Our results demonstrated that TROP2 could serve as a patient-tailoring and predictive biomarker for ADC therapeutics but not as a general prognostic biomarker to predicate patient survival.