Inhibition of thioredoxin reductase by mansonone F analogues: Implications for anticancer activity

Mammalian thioredoxin reductase (TrxR), a ubiquitous selenocysteine containing oxidoreductase, catalyzes the NADPH-dependent reduction of oxidized thioredoxin (Trx). TrxR has been suggested as a potential target for anticancer drugs development for its overexpression in human tumors and its diverse functions in intracellular redox control, cell growth and apoptosis. Mansonone F (MF) compounds have been shown to exhibit antiproliferative effects, but their complex mechanisms are unknown. In the present study, we have investigated the effects of some synthesized MF analogues on TrxR and HeLa cells. The studies of the mode of inhibition and the interactions of IG3, one of the most potent MF analogues, with TrxR showed MF compounds could be partly reduced by the C-terminal selenolthiol active site, and possibly by the N-terminal dithiol motif and/or FAD domain of TrxR simultaneously, accompanied by redox cycling with the generation of superoxide anion radicals. In addition, MF analogues exhibited the potential to inhibit the growth of HeLa cells and reduce TrxR activity in cell lysates. The cell cycle was arrested in G2/M phase and apoptosis was induced in a dose-dependent manner. Furthermore, our results showed that IG3-treated HeLa cells induced the change of intracellular ROS. Taken together, the reported results here suggest that inhibition of TrxR by MF analogues provides a possible complex mechanism for explaining the anticancer activity of MF compounds.