Identification of inhibitors of Cytochrome P450 (CYP) 1B1

Abstract

Cytochrome P450(CYP)1B1 is known to be overexpressed in several types of human malignancies. The role of CYP1B1 in estradiol metabolism to catalyze the hydroxylation at the C‐4 position is of specific importance in estrogen‐related tumorigenesis. Finding a safe, potent inhibitor to this critical step could lead to chemoprevention of several forms of human cancer. We initially used the Chembridge online database (www.hit2lead.com) to perform similarity searches, using 2,3′,4,5′‐tetramethoxystilbene (TMS), a compound known to inhibit CYP1B1 activity, as the search target. Using A 50% similarity threshold, 64 compounds were ultimately tested at a single concentration for inhibition of CYP1B1 catalyzed ethoxyresorufin‐o‐deethylase (EROD) activity. Five compounds inhibited EROD activity to an extent equal to or greater than TMS, and were considered positive hits. CYP1‐selectivity studies were performed on these five compounds, establishing selectivity of CYP1B1 over both CYP1A1 and CYP1A2. Kinetic studies were used to determine the Ki and the mechanism of enzyme inhibition. Cell viability studies were performed using the MTT assay on breast cancer cell lines. Additionally, follow on studies have been performed using analogs of the original five compounds to continue the search for safe, potent inhibitors of CYP1B1.Support or Funding InformationONR