02 BOOK OF ABSTRACTS .indd

The effect of xantohumol on normal and cancer cell
lines and its modulatory effects on genotoxicity of
heterocyclic amine (IQ) in HepG2 cells
Irena Zajc, Janja Plazar, Metka Filipi~ and Tamara Lah
Department of Genetic Toxicology and Cancer Biology, National Institute
of Biology; Ve~na pot 111, 1000 Ljubljana, Slovenia, www.nib.si
Xanthohumol (XN) is the principal prenylated chalcone of the female inflorescences
of the hop (Humulus lupulus L.) and commonly used as a preservative and
flavouring agent in beer. It’s natural role is to protect the plants against insect
feeding. XN has been reported to have a broad spectrum of inhibitory mechanisms
at the initiation, promotion and progression stages of carcinogenesis. The aims
of the present study were to explore: 1) the cytotoxicity of XN on normal and
neoplastic human cell lines and its effects on cell adhesion and apoptosis and
2) the potential of XN to inhibit the heterocyclic amine IQ induced genotoxicity in
S. typhimurium TA98 and in human hepatoma HepG2 cells.
Normal human umbilical vein cells (HUVEC) and diploid immortalized human breast
epithelial cell line (MCF10A) with normal karyotype, and two tumour cell lines (breast
MCF10AneoT and glioblastoma U87 cell line) were used to study cytotoxicity of XN
and its effect on adhesion of the two cancer cell lines by MTT assay. The effect of
XN on apoptosis was studied by staining the cells with DNA binding dyes acridine
orange and ethidium bromide. Mutagenicity and antimutagenicity of XN was tested
with S. typhimurium TA98 using the standard plate incorporation procedure (Ames
test). Genotoxicity of XN and its potential to inhibit IQ induced DNA damage in
human hepatoma HepG2 cells were determined by the comet and the potential of
XN to modulate CYP1A activity was determined with the EROD assays.
XN was cytotoxic for cancer cells (U87 and MCF10AneoT) at 15 µM concentration
and for the normal cells (HUVEC and MCF10A) at 50 µM concentration.
At subtoxic concentrations, XN had a significant impact on adhesion of U87 cell
line to Matrigel and fibronectin, but it did not affect the adhesion of MCF10AneoT.
At 30 µM concentration, XN triggered apoptosis in all four cell lines. The proportion of
apoptotic cells did not differ among cell lines after 24 hours, whereas after 48 hours,
it was significantly higher in cancer cell lines than in the normal cells. In the Ames
test with Salmonella typhimurium TA98, XN showed dose dependent antimutagenic
activity against the indirect acting mutagen IQ. In HepG2 cells, XN reduced EROD
activity and at 10 µg/ml (28.25 µM) concentration completely prevented IQ induced
DNA damage, indicating that the mechanism of XN antigenotoxicity is inhibition of
metabolic activation of IQ.
In conclusion, this data showed selective cytotoxicity of XN for cancer cells, which
can at least partly contribute to selective induction of apoptosis. Furthermore, XN
is a potent inhibitor of IQ induced genotoxicity. Therefore, XN has a potential as
chemopreventive agent at the initiation and progression step of cancer development
and could present a candidate for prevention and treatment of cancer.
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