The multifactorial origin of gastric cancer encompasses environmental factors mainly associated with diet. Pteridium aquilinum-bracken fern-is the only higher plant known to cause cancer in animals. Its carcinogenic toxin, ptaquiloside, has been identified in milk of cows and groundwater. Humans can be directly exposed by consumption of the plant, contaminated water or milk, and spore inhalation. Epidemiological studies have shown an association between bracken exposure and gastric cancer. In the present work, the genotoxicity of P. aquilinum and ptaquiloside, including DNA damaging effects and DNA damage response, was characterized in human gastric epithelial cells and in a mouse model. In vitro, the highest doses of P. aquilinum extracts (40 mg/ml) and ptaquiloside (60 μg/ml) decreased cell viability and induced apoptosis. γH2AX and P53-binding protein 1 analysis indicated induction of DNA strand breaks in treated cells. P53 level also increased after exposure, associated with ATR-Chk1 signaling pathway activation. The involvement of ptaquiloside in the DNA damage activity of P. aquilinum was confirmed by deregulation of the expression of a panel of genes related to DNA damage signaling pathways and DNA repair, in response to purified ptaquiloside. Oral administration of P. aquilinum extracts to mice increased gastric cell proliferation and led to frameshift events in intron 2 of the P53 gene. Our data demonstrate the direct DNA damaging and mutagenic effects of P. aquilinum. These results are in agreement with the carcinogenic properties attributed to this fern and its ptaquiloside toxin and support their role in promoting gastric carcinogenesis.

Ptaquiloside is a natural toxin present in bracken ferns ( Pteridium sp .). Cattle ingesting bracken may develop bladder tumours and excrete genotoxins in meat and milk. However, the fate of ptaquiloside in cattle and the link between ptaquiloside and cattle carcinogenesis is unresolved. Here, we present the toxicokinetic profile of ptaquiloside in plasma and urine after intravenous administration of ptaquiloside and after oral administration of bracken. Administered intravenously ptaquiloside, revealed a volume of distribution of 1.3 L kg -1 with a mean residence-time of 4 hours. A large fraction of ptaquiloside was converted to non-toxic pterosin B in the blood stream. Both ptaquiloside and pterosin B were excreted in urine (up to 41% of the dose). Oral administration of ptaquiloside via bracken extract or dried ferns did not result in observations of ptaquiloside in body fluids, indicating deglycosolidation in the rumen. Pterosin B was detected in both plasma and urine after oral administration. Hence, transport of carcinogenic ptaquiloside metabolites over the rumen membrane is indicated. Pterosin B recovered from urine counted for 7% of the dose given intravenously. Heifers exposed to bracken for 7 days (2 mg ptaquiloside kg -1 ) developed preneoplastic lesions in the urinary bladder most likely caused by genotoxic ptaquiloside metabolites.