Abstract
Human thioredoxin reductase 1 (TrxR1) is a selenocysteine-containing enzyme which plays a crucial role in regulating numerous redox signalling pathways within the cell. While its functioning is important in all cells, levels of TrxR1 expression are higher in cancer cells, possibly as an adaptation to much higher levels of reactive oxygen species and the need for more extensive DNA synthesis. This makes TrxR1 an attractive target for cancer therapy development. Inspired by the structure of disulphide compounds which have advanced through various stages of clinical development, we designed a series of dithiodiglycolic acid derivatives. These were prepared from respective thiol synthons using an iodine- or benzotriazolyl chloride-promoted oxidative disulphide bond formation. Inhibition of TrxR present in cell lysates from human neuroblastoma cells (SH-SY5Y) and rat liver cells indicated several compounds with a potential for TrxR inhibition. Some of these compounds were also tested for growth inhibition against two human cancer cell lines and normal human keratinocytes.
Highlights
Thioredoxin reductase enzymes (TrxR, EC 1.8.1.9), which are the focus of this work, belong to thioredoxin system along with NADPH and thioredoxin (Trx)
TrxR enzymes are overexpressed in cancer cells contributing to their resistant phenotype characterised by higher levels of ROS3
The trityl group was removed by the action of trifluoroacetic acid (TFA) used as a solvent (18a–c)18 or as a reagent (5 equiv.) in DCM (18d–k)19, in the presence of triethylsilane
Summary
Thioredoxin reductase enzymes (TrxR, EC 1.8.1.9), which are the focus of this work, belong to thioredoxin system along with NADPH and thioredoxin (Trx). TrxR enzymes are overexpressed in cancer cells contributing to their resistant phenotype characterised by higher levels of ROS3. Compounds – 5,50-dithiobis(2-nitrobenzoic acid) (8 known as DTNB or Ellman’s reagent), thioredoxin reductase fluorogenic substrate (9 or TRFS-green) and mitochondria-targeted “mitoTRFS” [10]13 have not been employed as TrxR inhibitors but rather as fluorescent probes, due to their being substrate (disulphide-linked Trx) analogues. The rest of the compounds are described in the Supplementary Data
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