Breast cancer cells are classified into several subtypes: Luminal A subtype, including MCF-7 and T47D cells; Luminal B subtype, such as BT474; HER-2 positive subtype, represented by SKBR3 cells; and triple-negative subtype, exemplified by MDA-MB-231, MDA-MB-468, and BT549 cells, based on their expression of ER, PR, HER-2, and Ki-67. Here, ERBB2 is linked to breast cancer.