| Selective estrogen receptor modulators (SERMs) are clinically important for treatment and prevention of breast cancer and for therapy of postmenopausal osteoporosis. However, SERMs are polyaromatic compounds and can be oxidatively bioactivated to reactive metabolites including o-quinone, quinone methide, and di-quinone methide. These reactive SERM quinoids are potentially genotoxic but also have the potential to induce cytoprotective phase II enzymes such as NAD(P)H-dependent quinone oxidoreductase (NQO1) via modifying cellular biomolecules.;To identify protein targets of SERM quinoids, four methodologies, using SERM derivatives conjugated with azido, biotin, or fluorophore tags were compared for sensitivity and specificity in vitro, in cell lysates, and in primary hepatocytes. The azidoTag/Staudinger method was sensitive but nonspecific; the azidoTag/click methodology had low sensitivity; and the dansylTag methodology failed to detect modified proteins in hepatocytes. The COATag methodology was confirmed to be the best, detecting 5 ng of modified protein in vitro and identifying protein targets in hepatocytes. For study of the protein targets of electrophilic metabolites formed by in situ oxidative bioactivation, the COATag is both sensitive and specific and does not appear to suffer from poor cell permeability.;In order to develop new SERMs with improved therapeutic profiles, a family of benzothiophene SERMs (X-DMA SERMs) including arzoxifene and its metabolite desmethylated arzoxifene (DMA) were developed with modulated redox activity. The induction of NQO1 by these SERMs was assayed in liver cells and in rat models and the potential mechanisms were investigated. The results suggested that arzoxifene might provide chemopreventive benefits over other SERMs via activating ER-independent Nrf2-ARE pathways. These studies are significant for the clinical use of benzothiophene SERMs as chemopreventive agents and should facilitate future research in the development of new SERMs. |
