DNA adduct formation by Fusarium culture extracts: lack of role of fusarinC

Fusarium fungi have been shown to infect corn and other crops worldwide, an d have a significant impact on human health through loss of crops or contam ination of food with mycotoxins. Isolates of Fusarium fungi from an area of South Africa with high incidence of esophageal cancer have been shown to i nduce esophageal and liver cancer in rats. Several isolates of Fusarium fun gi were grown on corn to determine if genotoxic products were produced. We report the incubation of methanol extracts of Fusarium verticillioides cult ures with DNA in the presence of rat liver fractions (S9) resulted in the f ormation of a unique DNA adduct that was detected by P-32-postlabeling. Fus arin C was purified from cultures of Fusarium verticillioides RRC 415, and was not responsible for the formation of the DNA adduct. Treatment of the m ethanolic extracts with ultraviolet B radiation reduced the fusarin C conte nt in the extract; however, this had no effect on the formation of the DNA adduct following incubation of the extract with DNA and S9. The unique DNA adduct was formed following the incubation of several Fusarium verticillioi dess isolates from the US and South Africa, while extracts of cultures of F usarium graminearium and Fusarium sacchari isolates formed very little of t he DNA adduct when incubated with DNA and S9. These data suggest that neith er fusarin C nor any of its metabolites an responsible for formation of the DNA adduct, and that an unidentified compound is prevent in F. verticillio ides cultures that forms a DNA adduct, and may be important in the etiology of human esophageal cancer. (C) 2000 Elsevier Science Ireland Ltd. All rig hts reserved.