Disabling Mitochondrial Peroxide Metabolism via Combinatorial Targeting of Peroxiredoxin 3 as an Effective Therapeutic Approach for Malignant Mesothelioma

Abstract

Dysregulation of signaling pathways and energy metabolism in cancer cells enhances production of mitochondrial hydrogen peroxide that supports tumorigenesis through multiple mechanisms. To counteract the adverse effects of mitochondrial peroxide many solid tumor types up-regulate the mitochondrial thioredoxin reductase 2 - thioredoxin 2 (TRX2) - peroxiredoxin 3 (PRX3) antioxidant network. Using malignant mesothelioma cells as a model, we show that thiostrepton (TS) irreversibly disables PRX3 via covalent crosslinking of peroxidatic and resolving cysteine residues in homodimers, and that targeting the oxidoreductase TRX2 with the triphenylmethane gentian violet (GV) potentiates adduction by increasing levels of disulfide-bonded PRX3 dimers. Due to the fact that activity of the PRX3 catalytic cycle dictates the rate of adduction by TS, immortalized and primary human mesothelial cells are significantly less sensitive to both compounds. Moreover, stable knockdown of PRX3 reduces mesothelioma cell proliferation and sensitivity to TS. Expression of catalase in shPRX3 mesothelioma cells restores defects in cell proliferation but not sensitivity to TS. In a SCID mouse xenograft model of human mesothelioma, administration of TS and GV together reduced tumor burden more effectively than either agent alone. Because increased production of mitochondrial hydrogen peroxide is a common phenotype of malignant cells, and TS and GV are well tolerated in mammals, we propose that targeting PRX3 is a feasible redox-dependent strategy for managing mesothelioma and other intractable human malignancies.

Kinetic analysis of structural influences on the susceptibility of peroxiredoxins 2 and 3 to hyperoxidation

“…Support for this notion comes from other biochemical and modelling studies [14] and the observation that hyperoxidation can occur with substoichiometric amounts of H 2 O 2 [32,33]. It is also consistent with observations that Prx3 is preferentially inhibited by thiostrepton, a compound that covalently links the monomers and reacts preferentially with the single disulfide dimer [34]. A possible explanation is that formation of a S p O 2 – at one active site increases the rate of disulfide formation at the other (Reaction 3; Figure 1).…”

Down-Regulation of SOX2 Underlies the Inhibitory Effects of the Triphenylmethane Gentian Violet on Melanoma Cell Self-Renewal and Survival

“…GV has been used as an antibacterial, antimycotic, and antiangiogenic agent. More recently, GV has shown a strong anticancer activity both in vitro and in vivo (Bhandarkar et al, 2009;Cunniff et al, 2015;Mukawera et al, 2015;Perry et al, 2006;Yamaguchi et al, 2015) with minimal adverse effects, thus making it safe for use in humans (Arbiser, 2009). Taken together, our data suggest that GV could be a good candidate for both chemoprevention and therapeutic treatment of human melanoma.…”

Activation of the Nrf2-Keap 1 Pathway in Short-Term Iodide Excess in Thyroid in Rats

“…Finally, mitochondria contain 30 times more Prx 3 than glutathione peroxidase; Prx 3 can be classified as an important regulator of mitochondrial H 2 O 2 [22]. The elevated expression of Prx 3 is associated with the blockage of apoptosis, increasing cell proliferation, and is related to adaptive responses, which are all required to maintain mitochondrial function [53, 54]. Bae et al have suggested that Prx 3 and Srx jointly protect mice from Pyrazole-induced oxidative liver injury in a Nrf2-dependent manner [43].…”