15E-13 |
Effects of flavonoids and allyl sulfides on telomerase activity in U937 cells |
H. S. CHUN, E. H. Choi, and H. J. Kim. Korea Food Research Institute, San 46-1, Baekhyun-dong, Bundang-gu, Sungnam, 463-746, South Korea Considerable animal and human epidemiological studies suggest that food-derived substances including flavonoids and allyl sulfides have preventive potentials against many forms of cancer. However, the exact mechanisms underlying these activities are still unclear. Based on the recent observation that more than 85% of cancers express telomerase, the reverse transcriptase responsible for maintaining the ends of chromosomes, telomerase has been recently given a great interest and proposed as a potential target for chemotherapy or chemoprevension. As a mechanistic study, the effects of seven flavonoids including four catechins and three allyl sulfides on telomerase activity were investigated in U937 human monoblastoid leukemia cells as representatives for leukemias. Telomerase activity was measured by telomeric repeat amplification protocol (TRAP) assay both in cell-free system and living cells, and quantified using a densitometer/software system. Among the flavonoids tested, epigallocatechin gallate (EGCG) at 2-8 mg/ml concentration inhibited the telomerase activity in a cell free system. Fifty percent inhibitory cencentration (IC50) for this effect of ECGC in a cell free system was estimated to be at ~ 2 mg/ml. A further measurement of telomerase activity in living cells also showed that telomerase product signal was decreased in U937 cells treated with 50-100 mg/ml of EGCG. However, none of the allyl sulfides tested in this study showed the inhibitory effect on the telomerase activity both in cell-free system and living cells. Therefore, it is suggested that telomerase inhibition could be one of the major mechanisms underlying the cancer preventive potentials of catechins, particularly EGCG.
Session 15E, Nutraceuticals & Functional Foods I
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