ERBB2 and breast cancer: Among the latter, TOP1, which was also found in EVs from murine BRCA1-deficient tumors [25], may be of particular interest to be evaluated in future studies as an EV-associated biomarker in monitoring breast cancer response to therapy for the following reasons: it functions as an oncogene [26], it is frequently amplified in breast cancer [27], and lastly, because it is a target for deruxtecan, which is effectively delivered to ERBB2+ breast cancer cells by Tz as antibody drug conjugate (DS-8201a) [28].