Biomarkers of tumour redox status in response to modulations of glutathione and thioredoxin antioxidant pathways.

The ability of certain cancer cells to maintain a highly reduced intracellular environment is correlated with aggressiveness and drug resistance. Since the glutathione (GSH) and thioredoxin (TRX) systems cooperate to a tight regulation of ROS in cell physiology, and to a stimulation of tumour initiation and progression, modulation of the GSH and TRX pathways are emerging as new potential targets in cancer. <italic>In vivo</italic> methods to assess changes in tumour redox status are critically needed to assess the relevance of redox-targeted agents. The current study assesses <italic>in vitro</italic> and <italic>in vivo</italic> biomarkers of tumour redox status in response to treatments targeting the GSH and TRX pathways, by comparing cytosolic and mitochondrial redox nitroxide electron paramagnetic resonance (EPR) probes, and cross-validation with redox dynamic fluorescent measurement. For that purpose, the effect of the GSH modulator buthionine sulfoximine (BSO) and of the TRX reductase inhibitor auranofin were measured <italic>in vitro</italic> using both cytosolic and mitochondrial EPR and roGFP probes in breast and cervical cancer cells. <italic>In vivo</italic>, mice bearing breast or cervical cancer xenografts were treated with the GSH or TRX modulators and monitored using the mito-TEMPO spin probe. Our data highlight the importance of using mitochondria-targeted spin probes to assess changes in tumour redox status induced by redox modulators. Further <italic>in vivo</italic> validation of the mito-tempo spin probe with alternative <italic>in vivo</italic> methods should be considered, yet the spin probe used <italic>in vivo</italic> in xenografts demonstrated sensitivity to the redox status modulators. [ABSTRACT FROM AUTHOR]