Detoxification of Mitochondrial Oxidants and Apoptotic Signaling Are Facilitated by Thioredoxin-2 and Peroxiredoxin-3 during Hyperoxic Injury

A central hallmark of tumorigenesis is metabolic alterations that increase mitochondrial reactive oxygen species (mROS). In response, cancer cells upregulate their antioxidant capacity and redox-responsive signaling pathways. A promising chemotherapeutic approach is to increase ROS to levels incompatible with tumor cell survival. Mitochondrial peroxiredoxin 3 (PRX3) plays a significant role in detoxifying hydrogen peroxide (H2O2). PRX3 is a molecular target of thiostrepton (TS), a natural product and FDA-approved antibiotic. TS inactivates PRX3 by covalently adducting its two catalytic cysteine residues and crosslinking the homodimer. Using cellular models of malignant mesothelioma, we show here that PRX3 expression and mROS levels in cells correlate with sensitivity to TS and that TS reacts selectively with PRX3 relative to other PRX isoforms. Using recombinant PRXs 1–5, we demonstrate that TS preferentially reacts with a reduced thiolate in the PRX3 dimer at mitochondrial pH. We also show that partially oxidized PRX3 fully dissociates to dimers, while partially oxidized PRX1 and PRX2 remain largely decameric. The ability of TS to react with engineered dimers of PRX1 and PRX2 at mitochondrial pH, but inefficiently with wild-type decameric protein at cytoplasmic pH, supports a novel mechanism of action and explains the specificity of TS for PRX3. Thus, the unique structure and propensity of PRX3 to form dimers contribute to its increased sensitivity to TS-mediated inactivation, making PRX3 a promising target for prooxidant cancer therapy.

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Tocotrienol-Induced Caspase-8 Activation is Unrelated to Death Receptor Apoptotic Signaling in Neoplastic Mammary Epithelial Cells

Experimental Biology and Medicine ◽

10.1177/153537020422900806 ◽

2004 ◽

Vol 229 (8) ◽

pp. 745-755 ◽

Cited By ~ 67

Author(s):

Sumit Shah ◽

Paul W. Sylvester

Keyword(s):

Epithelial Cells ◽

Mammary Epithelial Cells ◽

Death Receptor ◽

Mammary Epithelial ◽

Caspase 8 ◽

Apoptotic Signaling

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Proteasome inhibitor MG132 induces apoptosis in human osteosarcoma U2OS cells

Human & Experimental Toxicology ◽

10.1177/09603271211017972 ◽

2021 ◽

pp. 096032712110179

Author(s):

Han Ki Lee ◽

See-Hyoung Park ◽

Myeong Jin Nam

Keyword(s):

Signaling Pathways ◽

Proteasome Inhibitor ◽

Migration And Invasion ◽

Apoptotic Signaling ◽

Antiapoptotic Proteins ◽

Human Osteosarcoma ◽

Anticancer Effects ◽

Caspase 7 ◽

U2os Cells ◽

Western Blotting Assay

MG132 is a potent, reversible, and cell-permeable 20S proteasome inhibitor and it is derived from a Chinese medicinal plant. The purpose of this study is to investigate the anticancer effects of MG132 against human osteosarcoma U2OS cells. We first performed MTT and colony formation assays to investigate the anti-proliferative effects of MG132. The results demonstrated that MG132 suppressed the proliferation of U2OS cells. Furthermore, we found that treatment with MG132 increased apoptosis and induced DNA damage in U2OS cells. Additionally, zymography, wound healing, and invasion assays showed that MG132 suppressed the enzymatic activity of matrix metalloproteinases, cell migration, and invasion, respectively of U2OS cells. Furthermore, western blotting assay was performed to investigate the apoptotic signaling pathways in MG132-treated U2OS cells. Our results showed that MG132 downregulated the expression of antiapoptotic proteins, including CDK2, CDK4, Bcl-xL, and Bcl-2, whereas it upregulated the expression of proapoptotic proteins, including p21, p27, p53, p-p53 (ser15, ser20, and ser46), cleaved forms of caspase-3, caspase-7, caspase-9, and PARP, and FOXO3 in U2OS cells. These results demonstrated that MG132 activated apoptotic signaling pathways in U2OS cells. Interestingly, MG132 downregulated the phosphorylation of Akt and Erk. Taken together, our results suggest that MG132 has anticancer effects in U2OS cells. Therefore, MG132 may be a potential therapeutic agent for the treatment of osteosarcoma.

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