ESR1 and breast cancer: Indeed, cadmium produced an apparent basal-like breast cancer phenotype, including ER negativity, HER2 negativity, reduced BRCA1 expression, and increased expression of p63 and CK5, all noteworthy characteristics of basal-like human breast cancer phenotype (Fadare and Tavassoli 2007; Liu et al. 2008; Ribeiro-Silva et al. 2005; Yehiely et al. 2006).