Among the most promising, the histone lysine N-methyltransferase, H3 lysine-79 specific, Dot1L was found to be a key component of the ERα-mediated transcriptional regulation in BC, where its selective pharmacological inhibition was shown to cause growth arrest and death of AE-sensitive and AE-resistant human ER + BC tumor models [8]. This evidence concerns the gene ESR1 and breast cancer.