In vitro cytotoxicity of epigallocatechin gallate and tea extracts to cancerous and normal cells from the human oral cavity.
This study compared the in vitro responses of malignant and normal cells from the human oral cavity to tea extracts and to its main polyphenolic component, (-)-epigallocatechin gallate (EGCG). The antiproliferative effects of tea polyphenolic extracts and EGCG were more pronounced towards immortalized, tumourigenic (CAL27, HSC-2, and HSG(1)) and non-tumourigenic (S-G) cells than towards normal (GN56 and HGF-1) fibroblasts and green tea was more toxic than black tea. As the addition of tea extract or EGCG to cell culture medium led to the formation of hydrogen peroxide (H(2)O(2)), the research then focused on EGCG as an inducer of oxidative stress, using CAL27, the cancerous cells most sensitive to EGCG, HSG(1), the cancerous cells least sensitive to EGCG, and GN56 cells. The toxicity of EGCG was decreased in the presence of catalase, an enzyme that degrades H(2)O(2), or of deferoxamine, a chelator of Fe(3+). Conversely, pretreatment of the cells with the glutathione depleters, 1-chloro-2,4-dinitrobenzene and 1,3-bis(2-chloroethyl)-N-nitrosourea, potentiated the toxicity of EGCG. A 4-hr exposure to EGCG lessened the intracellular level of reduced glutathione in the CAL27 and HSG(1) cells, but not in the GN56 fibroblasts. Whereas EGCG itself did not induce lipid peroxidation, Fe(2+)-induced lipid peroxidation was potentiated by EGCG. A 72-hr exposure to cytotoxic concentrations of EGCG induced significant cytoplasmic vacuolization in all cell types. The results presented herein are consistent with EGCG acting as a prooxidant, with the cancerous cells more sensitive to oxidative stress than the normal cells.
Weisburg
Jeffrey H
JH
Stern College for Women, Yeshiva University, Department of Biology, 245 Lexington Avenue, New York, NY 10016, U.S.A. weisburg@yu.edu
Weissman
Danielle B
DB
Sedaghat
Tannaz
T
Babich
Harvey
H
D016588:Anticarcinogenic Agents / Q000494:pharmacology* / Q000633:toxicity; D028241:Camellia sinensis; D002294:Carcinoma, Squamous Cell / Q000473:pathology; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology* / Q000633:toxicity; D006801:Humans; D015227:Lipid Peroxidation / Q000187:drug effects; D009055:Mouth / Q000166:cytology; D018384:Oxidative Stress / Q000187:drug effects; D010936:Plant Extracts / Q000494:pharmacology / Q000633:toxicity; D013662:Tea / Q000737:chemistry; D014062:Tongue Neoplasms / Q000473:pathology; D014407:Tumor Cells, Cultured
D016588:Anticarcinogenic Agents; D010936:Plant Extracts; D013662:Tea; D002392:Catechin; C045651:epigallocatechin gallate