COMT and neoplasm: 2-Methoxyestradiol (1, Figure 1), which is the methylation metabolite of 2-hydroxyetradiol under the action of catechol-O-methyltransferase (COMT), has been elucidated as a highly potent anti-proliferative metabolite against different tumor cells and can induce apoptosis both in vitro and in vivo [1,2,3,4].