Volume 4, Issue 7 p. 2160-2174
Research Article

Protein expression profiling identifies molecular targets of quercetin as a major dietary flavonoid in human colon cancer cells

Uwe Wenzel

Corresponding Author

Uwe Wenzel

Department of Food and Nutrition, Molecular Nutrition Unit, Technical University of Munich, Freising, Germany

Department of Food and Nutrition, Molecular Nutrition Unit, Hochfeldweg 2, D-85350 Freising-Weihenstephan, Germany Fax: +49-8161-71-3999===Search for more papers by this author
Angelika Herzog

Angelika Herzog

Department of Food and Nutrition, Molecular Nutrition Unit, Technical University of Munich, Freising, Germany

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Sabine Kuntz

Sabine Kuntz

Department of Food and Nutrition, Molecular Nutrition Unit, Technical University of Munich, Freising, Germany

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Hannelore Daniel

Hannelore Daniel

Department of Food and Nutrition, Molecular Nutrition Unit, Technical University of Munich, Freising, Germany

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First published: 22 June 2004
Citations: 71

Abstract

A high dietary intake of plant foods is thought to contribute to the prevention of colorectal cancers in humans and flavonoids as part of such a diet are considered to contribute to those protective effects. Quercetin is a major dietary flavonoid consumed with a diet rich in onions, tea, and apples. We used HT-29 human colon cancer cells and investigated the effects of quercetin on proliferation, apoptosis, and differentiation as processes shown to be disregulated during cancer development. To identify the cellular targets of quercetin action, two-dimensional gel electrophoresis was performed and proteins altered in expression level after quercetin exposure of cells were identified by mass spectrometry of peptide fragments generated by tryptic digestion. Quercetin inhibited the proliferation of HT-29 cells with an IC50-value of 81.2 ± 6.6 μM. Cell differentiation based on surface expression of alkaline phosphatase was enhanced 4-fold and the activity of the pro-apoptotic effector caspase-3 increased 3-fold. Those effects were associated with the regulation of heat-shock proteins and annexins shown to both play a crucial role in the process of apoptosis. Cytoskeletal caspase substrates were found as regulated as well and various proteins involved in intermediary metabolism and in gene regulation showed altered steady-state expression levels upon quercetin treatment of cells. In conclusion, quercetin alters the levels of a variety of proteins involved in growth, differentiation, and apoptosis of colon cancer cells. Their identification as molecular targets of quercetin may explain the anti-cancer activities of this flavonoid.