Liu and colleagues showed that Norendox inhibited CYP2C19 and aromatase (CYP19A1) activity (Liu et al. 2013), while CYP19A1 activity was also inhibited by Endox (Lu et al. 2012) pointing to a dualistic inhibitory effect of Endox on estrogen-driven breast cancer cells. This evidence concerns the gene CYP19A1 and breast cancer.