ERBB3 and breast neoplasm: We then tested HER3-VIA for binding to a series of human HER3-expressing breast tumor cell lines, including the high HER3-expressing BT474M1 and BT474, the moderately HER3-expressing SKBR3 and T47D, and the HER3 low/negative, triple negative MDA-MB-231 tumor cell lines (Fig. 1b).