In this study, we designed an in vitro azoxymethane (AOM)-induced carcinogenesis model and analyzed the effect of deoxycholic acid (DCA) on growth, apoptosis, genotoxicity, and transformation of IEC6 intestinal cells. CYP2E1 production was confirmed in IEC6 cells. The growth of IEC6 cells was enhanced by DCA (100 microg/ml). However, IEC6 cells treated with DCA (200 microg/ml) were inhibited and disappeared at 48 hrs after treatment. Apoptotic cells increased 11.2 times by treatment with DCA (200 microg/ml) as compared to cells with no treatment. DNA injury detected by comet assay was found in cells treated with AOM, but not in cells treated with DCA (100 microg/ml) and AOM. The number of colony formation in soft agar increased by AOM treatment. However, the number of foci treated with DCA (100 microg/ml) plus AOM was 69% that of cells treated with AOM alone. Two out of the 6 mice subcutaneously injected with AOM-treated IEC6 cells showed tumorigenesis, whereas IEC6 cells treated with DCA (100 microg/ml) plus AOM or DCA (100 microg/ml) alone did not form any tumor. Reduced protein expression of MLH1, Bcl-2 was detected in IEC6 cells treated with DCA (100 microg/ml). Production of Bax, pJNK, TGF-beta, TGFBRI, TGFBRII, and beta-catenin were higher in IEC6 cells treated with DCA (100 microg/ml) than that in cells with no treatment. These results suggest that high-dose DCA induced apoptosis and inhibited AOM-induced in vitro transformation of IEC6 cells.