Quercetin, a flavonoid, is found in many plants, including edible fruits and vegetables. We examined the effects on cell growth of human malignant cells derived from the gastrointestinal tract and on cell cycle progression. Quercetin markedly inhibited the growth of human gastric cancer cells and the ICsO value was 32-55 PM. DNA synthesis was suppressed to 14% of the control level by the treatment with 70 PM quercetin for 2 days.Furthermore, quercetin blocked cell progression from the Gi to the S phase.Quercetin; Cell cycle; (Human gastric cancer cell) 1, INTRODUCTIONQuercetin, a flavonoid found in many plants, is widely distributed in edible fruits and vegetables. Humans regularly consume foods containing quercetin not only in its free form, but also in the fi-glycoside form, such as rutin and quercitrin. When quercetin was administered orally, it was poorly absorbed from the digestive tract and did not have a great influence on the organs except the gastrointestinal tract. A proportion of the quercetin administered was degraded by the intestinal microflora and the remainder was excreted in feces in an unchanged form [l-2].Recently quercetin was found to inhibit the cell growth of leukemia cells, Ehrich ascites tumor cells [3], and NK/Ly ascites tumor cells 141. To clarify the mechanism of anti-tumor effects, we examined its effect on the cell growth of four human gastric cancer cell lines, as well as on the cell cycle. MATERIALS AND METHODS Cell line and chemicalsQuercetin was purchased from Wako Pure Chemical Industries, Osaka. In this study, four human gastric cancer cell lines, HGC-27 [S], NUGC-2 [6], were used. Ceils were cultured in RPM1 1640 (Nissui) supplemented with 10% fetal calf serum and incubated at 37°C in a humidifi~ atmosphere containing 5% COz. Quercetin was dissolved in 0.25% dimethy sulfoxide (DMSO) and diluted to its final concentration in each culture dish. Measurement of cytotoxicityCells were plated at a density of 4 x 104 cells/2 ml medium in Correspondence address: M. Yoshida, Institute for Oriental Medicine, Hyogo, l-l-l, Higashidaimotsu-thou, Amagasaki 660, Japan 10 35 mm diameter dishes. The various concentrations of quercetin were added at the inoculation of cells, or at the 2nd day after the inoculation of cells. Control cells were exposed to DMSO at the same concentration as the other dishes. The culture was continued without medium change. The number of viable cells were measured by the Trypan blue dye exclusion test. The values represent means * SD. Data were analyzed using a two-tailed Student's t-test. Me~urement of DNA synthesis. DNA synthesis was assayed at 1, 3, 12, 18, 24, 36, and 48 h after treatment with quercetin. HGC-27 cells were incubated for 1 h with 10,&i of ['H]thymidine. The cells were washed with 2 ml of phosphate-buffered saline, treated with 2 ml of 5% trichloroacetic acid (TCA), and kept overnight or longer in a wet chamber. Cells were washed with 2 ml of 5% TCA and solubilized with 0.8 ml of 1% sodium dodecyl sulphate. The radioactivities of aliquots were c...

Transcriptional activation of human heat shock protein (HSP) genes by heat shock or other stresses is regulated by the activation of a heat shock factor (HSF). Activated HSF posttranslationally acquires DNA-binding ability. We previously reported that quercetin and some other flavonoids inhibited the induction of HSPs in HeLa and COLO 320DM cells, derived from a human colon cancer, at the level of mRNA accumulation. In this study, we examined the effects of quercetin on the induction of HSP70 promoterregulated chloramphenicol acetyltransferase (CAT) activity and on the binding of HSF to the heat shock element (HSE) by a gel mobility shift assay with extracts of COLO 320DM cells. Quercetin inhibited heat-induced CAT activity in COS-7 and COLO 320DM cells which were transfected with plasmids bearing the CAT gene under the control of the promoter region of the human HSP70 gene. Treatment with quercetin inhibited the binding of HSF to the HSE in whole-cell extracts activated in vivo by heat shock and in cytoplasmic extracts activated in vitro by elevated temperature or by urea. The binding of HSF activated in vitro by Nonidet P-40 was not suppressed by the addition of quercetin. The formation of the HSF-HSE complex was not inhibited when quercetin was added only during the binding reaction of HSF to the HSE after in vitro heat activation. Quercetin thus interacts with HSF and inhibits the induction of HSPs after heat shock through inhibition of HSF activation.Physiologic stress, including heat shock, enhances the synthesis of a limited number of intracellular proteins, the so-called heat shock proteins (HSPs) (19). The heat shock response has been observed in all cells so far tested, and some of the HSPs have been well conserved throughout evolution. In higher organisms, the induction of HSPs by heat shock or other stresses is regulated at the transcriptional and translational levels. The transcription of heat shock genes is regulated by the cis-acting heat shock element (HSE) in the promoter region and the trans-acting heat shock factor (HSF). The HSE consensus sequence was defined as the repeat of a 5-bp unit, NGAAN or NTTCN (2,28), where N is any nucleotide, and the molecular cloning of HSF from yeast and Drosophila cells has been reported (5,36,38). In Saccharomyces cerevisiae, HSF is already bound to the HSE under normal conditions, and transcriptional activation is induced after heat shock at least partly through the phosphorylation of HSF, whereas in Drosophila and mammalian cells, HSF acquires DNA-binding ability only after heat shock through posttranslational modification of HSF (18, 34).We have reported that quercetin and several other flavonoids inhibit the synthesis of HSPs, including HSP110, HSP90, HSP70, HSP47, HSP40, and HSP28, induced by heat shock, azetidine, or sodium arzenite treatment in two human cancer cell lines, HeLa and COLO 320DM cells (12). Quercetin inhibited the induction of HSP70 at the level of mRNA accumulation (12).Flavonoids are a group of dyes commonly contained in higher plants (...

Keywords: flavonoids/heat shock proteins/human cancer cell lines ABSTRACT. Cells exposed to several forms of stress, such as heat shock, transiently synthesize a group of proteins called heat shock proteins (hsps). Although many stressors other than heat shock are known to induce hsps, inhibitors of hsp expression have never been reported. Here we show that quercetiri and several other flavonoids inhibit the synthesis of hsps induced by heat shock in two human cell lines, Hela cells and COLO320 DMcells. Quercetin inhibited the induction of hsp70 at the level of mRNAaccumulation. This is the first report to describe the inhibition of hsp expression by reagents.Whencells or organisms are exposed to heat shock,

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Quercetin inhibits growth of COLO320 DM cells, derived from a human colon cancer. The inhibitory effect is partially reversible when quercetin is removed from the culture medium. Flow cytometric analysis has revealed that quercetin causes perturbation of the cell cycle, inducing a frozen cell-cycle pattern and a block at the G1/S boundary. The synthesis of a 17-kDa protein was specifically inhibited by the addition of quercetin, and recovered when the cells at the G1/S boundary progressed into S-phase after the removal of quercetin from the culture medium. Furthermore, using synchronized cells obtained by centrifugal elutriation, we have shown that the rate of synthesis of a 17-kDa protein was low in G1, and high in S-phase of the cell cycle. Thus, this protein appears to be cell-cycle-related.