Trop-2-expressing cells had better cell viability compared to control cells in the presence of lapatinib or neratinib treatment. Lapatinib- and neratinib-induced cell apoptosis was rescued by Trop-2 overexpression. Notably, patients responded to anti-HER2 therapy had lower Trop-2 transcript expression than non-responders....These results suggested that the oncogenic role of Trop-2 in HER2-positive breast cancer and Trop-2 expression might confer resistance to anti-HER2 therapy.