Quercetin arrests G2/M phase and induces caspase-dependent cell death in U937 cells
Introduction
Many natural dietary phytochemicals found in fruits, vegetables, spices, and tea have been shown to be protective against cancer in various animal models [1], [2]. The most common flavonoid glycones found in the diet are quercetin, rutin and robinin [3]. Quercetin (3,3′,4′,5,7-pentahydroxy-flavone) has been previously reported to inhibit leukemic cell growth without suppressing normal hematopoiesis [4]. It blocks the cell cycle at the G1/S transition in human colon cancer cells [5], [6] and arrests the cell cycle in late G1 prior to the beginning of S phase in human leukemic T-cells [7] and in G2/M phase in human breast cancer cells [8], [9]. Previous in vitro studies have reported that quercetin inhibits the growth of HT-29 cells, the human colon adenocarcinoma cell line in a dose-dependent manner [10], [11]. These activities of quercetin make it a promising candidate for treatment and prevention of various cancers.
Cyclin gene expression is tightly regulated in a phase-specific manner [12]. Cyclin A is synthesized at the onset of the S-phase, reaches a maximum at mitosis, and is degraded during the pro-metaphase, shortly prior to cyclin B1 degradation. Cyclin B1 accumulates in the S-phase, reaches a maximum at mitosis, and then is rapidly degraded at the metaphase/anaphase transition. Cyclin E begins to accumulate in late G1, peak at the G1/S transition and is down-regulated during S phase [13]. Cyclin E regulates G1-phase progression or S-phase commitment in mammalian cells.
In this study, to characterize the precise mechanism of action of quercetin on the cell division cycle engine, we analyzed cell cycle kinetics and expression level of cell cycle related proteins in quercetin-treated U937 cells. Subsequently, we examined its effect on the cell proliferation and cell death of human leukemia cells to clarify the mechanism of anti-proliferative effects of quercetin.
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Cells, cellular treatments and materials
The human leukemia U937 cells were obtained from ATCC (Rockville, MD). The culture medium used throughout these experiments was Dulbecco's modified Eagle's medium containing 10% FCS, 20 mM HEPES, 100 μg/ml gentamicin (complete medium). The quercetin was directly added to cell cultures at the indicated concentrations while untreated cells contained the solvent alone. Anti-cdk2, anti-cdc2, anti-cdk4, anti-cyclin D, anti-cyclin E, anti-cyclin B, anti-p21, and anti-p27 antibodies were purchased from
Effect of quercetin on cell cycle distribution
To test whether quercetin affected cell growth of U937 cells, cells were cultured in the presence or absence of 10 or 20 μM quercetin and the change in cell number over time was determined. The number of cells in the 20 μM quercetin-treated U937 cells was significantly inhibited in their cell growth, whereas the quercetin untreated U937 cells increased 2.8 fold cell numbers (Fig. 1A). To investigate the mechanisms involved in growth inhibition induced by quercetin, we carried out time kinetic
Discussion
A large variety of polyphenolic compounds from the vegetables and fruits have evoked considerable attention because of their multiplex biologic properties. Flavonoids have potent anti-proliferative, anti-neoplastic properties, and antioxidant activity, and it has been suggested that they prevent chronic diseases such as cancer [15], [16]. The relationship between diet and cancers has been implicated in several epidemiological studies [17].
Recent reports have been shown that quercetin has
Acknowledgements
This work was supported by grants to T.K. Kwon from the MRC Program of the Korea Science and Engineering Foundation (No. R13-2002–028–03001–0).
References (31)
- et al.
The effect of quercetin on cell cycle progression and growth of human gastric cancer cells
Fed. Eur. Biochem. Soc. Lett.
(1990) - et al.
Comparative effects of flavonoids on the growth, viability and metabolism of a colonic adenocarcinoma cell line (HT29 cells)
Cancer Lett.
(1996) Antiproliferative potency of structurally distinct dietary flavonoids on human colon cancer cells
Cancer Lett.
(1996)A long twentieth century of the cell cycle and beyond
Cell
(2000)- et al.
Effect of flavonoids on cell cycle progression in prostate cancer cells
Cancer Lett.
(2002) - et al.
Quercetin, a dietary-derived quercetin, a dietary-derived flavonoid, possesses antiangiogenic potential
Eur. J. Pharmacol.
(2003) - et al.
Studies on the inhibitory effects of quercetin on the growth of HL-60 leukemia cells
Biochem. Pharmacol.
(1997) - et al.
Mechanism of oxidative DNA damage induced by quercetin in the presence of Cu (II)
Mutat. Res.
(1999) - et al.
Ubiquitin/proteasome-dependent degradation of D-type cyclins is linked to tumor necrosis factor-induced cell cycle arrest
J. Biol. Chem.
(2002) - et al.
TGF-beta induced G (1) cell cycle arrest requires the activity of the proteasome pathwayt, transforming growth factor
Exp. Cell Res.
(2002)