Carcinogenesis Advance Access originally published online on April 24, 2009
Carcinogenesis 2009 30(6):1032-1040; doi:10.1093/carcin/bgp101
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Dietary flavonoid fisetin induces a forced exit from mitosis by targeting the mitotic spindle checkpoint
1 Medical Biotechnology, VTT Technical Research Centre of Finland, 20521 Turku, Finland
2 Turku Graduate School of Biomedical Sciences, 20520 Turku, Finland
3 Turku Centre for Biotechnology, University of Turku, 20521 Turku, Finland
4 Centre of Excellence for Translational Genome-Scale Biology, Academy of Finland, Finland
5 Cell Cycle and Cancer Biology Research Program, Oklahoma Medical Research Foundation, 825 Northeast 13th Street, MS 48, Oklahoma City, OK, 73104, USA
* To whom correspondence should be addressed. VTT Medical Biotechnology, 4th Floor, Pharmacity Building, Itäinen Pitkäkatu 4C, 20521 Turku, Finland. Tel: +358 02 4788614; Fax: +358 020 7222840;Email: marko.kallio{at}vtt.fi
Fisetin is a natural flavonol present in edible vegetables, fruits and wine at 2–160 µg/g concentrations and an ingredient in nutritional supplements with much higher concentrations. The compound has been reported to exert anticarcinogenic effects as well as antioxidant and anti-inflammatory activity via its ability to act as an inhibitor of cell proliferation and free radical scavenger, respectively. Our cell-based high-throughput screen for small molecules that override chemically induced mitotic arrest identified fisetin as an antimitotic compound. Fisetin rapidly compromised microtubule drug-induced mitotic block in a proteasome-dependent manner in several human cell lines. Moreover, in unperturbed human cancer cells fisetin caused premature initiation of chromosome segregation and exit from mitosis without normal cytokinesis. To understand the molecular mechanism behind these mitotic errors, we analyzed the consequences of fisetin treatment on the localization and phoshorylation of several mitotic proteins. Aurora B, Bub1, BubR1 and Cenp-F rapidly lost their kinetochore/centromere localization and others became dephosphorylated upon addition of fisetin to the culture medium. Finally, we identified Aurora B kinase as a novel direct target of fisetin. The activity of Aurora B was significantly reduced by fisetin in vitro and in cells, an effect that can explain the observed forced mitotic exit, failure of cytokinesis and decreased cell viability. In conclusion, our data propose that fisetin perturbs spindle checkpoint signaling, which may contribute to the antiproliferative effects of the compound.
Abbreviations: Cdk, cyclin-dependent kinase; DMEM, Dulbecco's modified Eagle's medium; DMSO, dimethyl sulfoxide; FACS, fluorescent-activated cell sorting; FBS, fetal bovine serum; HTS, high-throughput screen; Topo, topoisomerase
These authors contributed equally to this work. Received November 26, 2008; revised April 15, 2009; accepted April 17, 2009.