EGFR and cancer: Because MES-TNBC cells express both EGFR and PDGFRβ, in order to confirm the efficacy of the dual-targeting nanovectors on both cancer and stromal cells, we generated tumor spheroids consisting of cancer BT-474 cells (only EGFR+) and MSCs (only PDGFRβ+) that grew as colonies with approximately a 150 μm diameter after 13 days in culture (Supplementary Fig. 10A and Fig. 6A).