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  • Identification of Small Molecule Inhibitors of Human Cytochrome c Oxidase That Target Chemoresistant Glioma Cells.

Identification of Small Molecule Inhibitors of Human Cytochrome c Oxidase That Target Chemoresistant Glioma Cells.

The Journal of biological chemistry (2016-09-30)
Claudia R Oliva, Tahireh Markert, Larry J Ross, E Lucile White, Lynn Rasmussen, Wei Zhang, Maaike Everts, Douglas R Moellering, Shannon M Bailey, Mark J Suto, Corinne E Griguer
ABSTRACT

The enzyme cytochrome c oxidase (CcO) or complex IV (EC 1.9.3.1) is a large transmembrane protein complex that serves as the last enzyme in the respiratory electron transport chain of eukaryotic mitochondria. CcO promotes the switch from glycolytic to oxidative phosphorylation (OXPHOS) metabolism and has been associated with increased self-renewal characteristics in gliomas. Increased CcO activity in tumors has been associated with tumor progression after chemotherapy failure, and patients with primary glioblastoma multiforme and high tumor CcO activity have worse clinical outcomes than those with low tumor CcO activity. Therefore, CcO is an attractive target for cancer therapy. We report here the characterization of a CcO inhibitor (ADDA 5) that was identified using a high throughput screening paradigm. ADDA 5 demonstrated specificity for CcO, with no inhibition of other mitochondrial complexes or other relevant enzymes, and biochemical characterization showed that this compound is a non-competitive inhibitor of cytochrome c When tested in cellular assays, ADDA 5 dose-dependently inhibited the proliferation of chemosensitive and chemoresistant glioma cells but did not display toxicity against non-cancer cells. Furthermore, treatment with ADDA 5 led to significant inhibition of tumor growth in flank xenograft mouse models. Importantly, ADDA 5 inhibited CcO activity and blocked cell proliferation and neurosphere formation in cultures of glioma stem cells, the cells implicated in tumor recurrence and resistance to therapy in patients with glioblastoma. In summary, we have identified ADDA 5 as a lead CcO inhibitor for further optimization as a novel approach for the treatment of glioblastoma and related cancers.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Glutathione Peroxidase from bovine erythrocytes, lyophilized powder, ≥300 units/mg protein
Sigma-Aldrich
Xanthine Oxidase from bovine milk, Grade I, ammonium sulfate suspension, ≥0.4 units/mg protein
Sigma-Aldrich
Glutathione Reductase from baker's yeast (S. cerevisiae), ammonium sulfate suspension, 100-300 units/mg protein (biuret)
Sigma-Aldrich
Cytochrome c Oxidase from bovine heart, 5 mg protein/mL
Sigma-Aldrich
Superoxide Dismutase from human erythrocytes, essentially salt-free, lyophilized powder, ≥2,500 units/mg protein