BPA is known to harbor estrogenic activity; this compound is a weak agonist of both estrogen receptor alpha and beta (ERα and ERβ, respectively) (Kuiper et al. 1997) and is capable of stimulating moderate estrogen-independent proliferation in breast cancer cells (Hess-Wilson et al. 2006; Olsen et al. 2003). The gene discussed is ESR2; the disease is breast carcinoma.