Recent Studies on Aromatase and Sulfatase Involved in Breast Cancer and their Inhibitors

Enzyme aromatase uses several androgen substrates for the biosynthesis of estrogen, i.e. conversion of androstenedione to estrone and testosterone to biologically potent estradiol. Aromatase inhibitors (AIs) such as anastrozole, letrozole and exemestane have been established in standard endocrine therapy of breast cancer, by interfering with estrogen signaling cascade. Steroid sulphatase (STS) regulates the level of active oestrogens and androgens in human target organs and steroidogenic tissues, which have a key role in hormone dependent breast cancers (HDBC). Sulfatase is still under the exploration stage and is yet to emerge as a potential therapeutic target in breast cancer. The discovery of estrone 3-O-sulfamate (EMATE), a highly potent irreversible STS inhibitor, accelerated the development of potent steroidal and nonsteroidal STS inhibitors. Attempts are also being made for the development of dual inhibitors of AI and STS, as an alternative approach to overcome the acquired resistance. This review includes the molecular structures and biochemistry of aromatase and sulphatase enzymes. The advances in the development of inhibitors of the two enzymes have also been outlined.