Antibody-drug Conjugate Biomarker Expression in Gestational Trophoblastic Disease: Folate Receptor Alpha, Nectin-4, Trop-2, and Tissue Factor

Antibody-drug conjugates (ADC) are emerging therapies with promising results in the treatment of solid tumors. In this study, we aimed to evaluate biomarker expression of ADCs, including folate receptor alpha (FOLR1), Nectin-4, trophoblast cell surface antigen 2 (Trop-2), and tissue factor (TF) in a diverse cohort of gestational trophoblastic disease. Immunohistochemistry for FOLR1, Nectin-4, Trop-2, and TF was evaluated in tissue microarray of 18 complete hydatidiform moles (CHM) and whole tissue sections of 62 gestational trophoblastic neoplasia (GTN) by 2 gynecologic pathologists. Western blotting for FOLR1, Nectin-4, and Trop-2 was performed in JEG-3 and JAR choriocarcinoma cell lines, 2 CHM and 3 GTN clinical samples. Results: The overall immunohistochemical positive rate in GTN was 11% for FOLR1, 59% for Nectin-4, 38% for Trop-2, and 26% for TF. Choriocarcinomas showed 27% positivity for FOLR1, 75% for Nectin-4, 40% for Trop-2, and 25% for TF. Epithelioid trophoblastic tumors (ETT) were positive for Nectin-4 in 58%, for Trop-2 in 79%, and for TF in 67% of cases. Placental site trophoblastic tumors were positive only for Nectin-4 (23% of cases). In CHM, only Nectin-4 revealed a higher degree of expression and limited staining for the other markers. Western blotting showed FOLR1 expression in CHM, JEG-3, and JAR; Nectin-4 in CHM and PSTT; and Trop-2 in CHM, JEG-3, and choriocarcinoma. Conclusion: A subset of GTN shows expression for FOLR1, Nectin-4, Trop-2, and TF, particularly choriocarcinoma and ETT. These results suggest that patients with GTN could potentially benefit from ADC treatment.