Steroid sulfatase: A systematic study on the isolation, single step purification, and identification of its new inhibitors.

Estrogen receptor positive breast cancer (ERBC) is among the most common type of breast cancers. Currently aromatase inhibition is the mainstay therapy of ERBC. However, the emergence of drug resistance, and relapse of tumor progression has created the need of identification of new targets for drug development against ERBC. Hence, steroid sulfatase (STS) has emerged as a new drug target for the treatment of ERBC, as it is involved in the biosynthesis of hormones, including estrogens and androgens. The current study focuses on the purification of STS from human placentae, followed by identification of its small molecule inhibitors. STS enzyme was purified from human placenta, and characterized by Q-TOF LC/MS. The catalytic activity of the enzyme was analyzed using 1H NMR spectroscopy. Afterwards, a total of 161 commercially available synthetic and natural products were screened using fluorescence-based inhibition assay in-vitro. Among them, compounds 1 (sulfochlorophenol S), 2 (1,2-dihyrdoxyanthracene-9,10-dione), 3 (phenyl-2,3,4-trihydroxyphenyl methanone), 4 (4-anilinophenol), and 5 (lawsone) showed a moderate STS inhibitory activity with IC50 values between 11 and 16 μM. The non-covalent interactions between inhibitors and STS were studied via STD-NMR, molecular docking, and simulation studies. The newly identified inhibitors were found to be non-cytotoxic and druggable as assessed via MTT calorimetric, and ADMET analyses. The current study identifies significant and non-cytotoxic inhibitors of STS as potential drug hit against ERBC.