This study was conducted to investigate chemopreventive effects of Ganoderma lucidum using a unique in vitro human urothelial cell (HUC) model consisted of HUC-PC cells and MTC-11 cells. Ethanol and water extracts of fruiting bodies and spores of the G. lucidum were used to examine growth inhibition, actin polymerization status, and impact of actin remodeling on cell migration and adhesion. Results showed that ethanol extracts had a stronger growth inhibition effect than water extracts. Cell cycle analysis showed that the growth inhibition effect was associated with G2/M arrest. At non-cytotoxic concentrations (40-80 microg/ml), these extracts induced actin polymerization, which in turn inhibited carcinogen 4-aminobiphenyl induced migration in both cell lines. The increased actin polymerization was associated with increased stress fibers and focal adhesion complex formation, however, expression of matrix metalloproteinase-2 and focal adhesion kinase (total and phospholated) were unchanged, which suggests that other mechanisms may be involved.