Ling Tao1, Sarah C Forester, Joshua D Lambert. 1. Center of Excellence for Plant and Mushroom Foods for Health, Department of Food Science, The Pennsylvania State University, University Park, PA, USA.
Abstract
SCOPE: The tea catechin, (-)-epigallocatechin-3-gallate (EGCG), has potential cancer preventive effects. The prooxidant activity of EGCG may play a role in these effects. METHODS AND RESULTS: Here, we report that EGCG exerted cytotoxic effects against oral cancer cell lines (IC50 = 83-95 μM). EGCG treatment resulted in formation of extracellular reactive oxygen species (ROS), however, these ROS were rapidly cleared (half-life = 1.7 h). EGCG treatment increased the production of mitochondrial H2 O2 in SCC-25 cells (0-6 h) before the induction of apoptosis. Subsequently, an opening of the mitochondrial transition pore and a decrease in mitochondrial membrane potential were observed. The mitochondria-specific antioxidant, MitoTEMPO, reduced these effects. HGF-1 human gingival fibrobasts were resistant to EGCG (IC50 > 200 μM) and EGCG-induced ROS. EGCG induced differential expression of genes related to antioxidant defense in oral cancer cells and gingival fibroblasts: metallothionein 3, superoxide dismutase 2/3, and thioredoxin reductase 2 were downregulated in SCC-25 cells, but upregulated in HGF-1 cells. CONCLUSION: We conclude that induction of mitochondrial ROS and mitochondrial dysfunction by EGCG play a role in the inhibition of oral cancer, and that gingival fibroblasts are spared from these effects in part because of a selective induction of antioxidant responsive genes.
SCOPE: The tea catechin, (-)-epigallocatechin-3-gallate (EGCG), has potential cancer preventive effects. The prooxidant activity of EGCG may play a role in these effects. METHODS AND RESULTS: Here, we report that EGCG exerted cytotoxic effects against oral cancer cell lines (IC50 = 83-95 μM). EGCG treatment resulted in formation of extracellular reactive oxygen species (ROS), however, these ROS were rapidly cleared (half-life = 1.7 h). EGCG treatment increased the production of mitochondrial H2 O2 in SCC-25 cells (0-6 h) before the induction of apoptosis. Subsequently, an opening of the mitochondrial transition pore and a decrease in mitochondrial membrane potential were observed. The mitochondria-specific antioxidant, MitoTEMPO, reduced these effects. HGF-1 human gingival fibrobasts were resistant to EGCG (IC50 > 200 μM) and EGCG-induced ROS. EGCG induced differential expression of genes related to antioxidant defense in oral cancer cells and gingival fibroblasts: metallothionein 3, superoxide dismutase 2/3, and thioredoxin reductase 2 were downregulated in SCC-25 cells, but upregulated in HGF-1 cells. CONCLUSION: We conclude that induction of mitochondrial ROS and mitochondrial dysfunction by EGCG play a role in the inhibition of oral cancer, and that gingival fibroblasts are spared from these effects in part because of a selective induction of antioxidant responsive genes.
Authors: Abbas K Samadi; Alan Bilsland; Alexandros G Georgakilas; Amedeo Amedei; Amr Amin; Anupam Bishayee; Asfar S Azmi; Bal L Lokeshwar; Brendan Grue; Carolina Panis; Chandra S Boosani; Deepak Poudyal; Diana M Stafforini; Dipita Bhakta; Elena Niccolai; Gunjan Guha; H P Vasantha Rupasinghe; Hiromasa Fujii; Kanya Honoki; Kapil Mehta; Katia Aquilano; Leroy Lowe; Lorne J Hofseth; Luigi Ricciardiello; Maria Rosa Ciriolo; Neetu Singh; Richard L Whelan; Rupesh Chaturvedi; S Salman Ashraf; H M C Shantha Kumara; Somaira Nowsheen; Sulma I Mohammed; W Nicol Keith; William G Helferich; Xujuan Yang Journal: Semin Cancer Biol Date: 2015-05-05 Impact factor: 15.707