SIRT1 expression is highly elevated by stimulated 17-β-estradiol (E2) levels in most ERα-positive breast cancer samples (Elangovan et al., 2011; Lee et al., 2011) while SIRT1 inhibition leads to ER signaling inhibition (Yao et al., 2010) implying SIRT1 role as ERα co-activator. This evidence concerns the gene SIRT1 and breast cancer.