ERBB2 and breast cancer: To interrogate this assumption, five breast cancer cell lines, MM231, MM468, T47D, BT474, and SKBR3 representing the basal B/claudin-low, basal A, luminal A, luminal B, and HER2-overexpressing molecular types of breast cancers, respectively, were cultured on the three types of hydrogels for 5–7 days and stained with Vim, E-cad, and ZO-1.