Based on their receptor status, the six breast cancer cell lines were divided into three subtypes: hormone receptor positive (HR+: MCF7), human epidermal growth receptor positive (HER2+: BT474 and SKBR3) and triple negative (TN: MDA-MB-468, MDA-MB-231 and BT549) (Table 1) (Kao et al., 2009; Neve et al., 2006; Subik et al., 2010). The gene discussed is HR; the disease is breast cancer.