To examine the possibility that chemical inducers of cytochrome P450 may have effects on the expression of oncogenes and a tumor suppressor gene, human colon LS174T cells were treated with different cytochrome P450 inducers such as benzanthracene (Ba), pyrazole (Pyr) and phenobarbital-hydrocortisone (Pb-Hc). Three forms of cytochrome P450 (CYP1A1, CYP1A2 and CYP2E1) were detected in the colon cell line and all of them were induced following chemical treatments. Altered expression of c-fos, c-myc, c-jun, was observed following the treatments. c-src, K-ras and p53 were not significantly affected by any of the treatments at the time-point selected. Interestingly, c-fos expression was the most dramatically altered by different treatments, showing repression with all of the treatments. These data show that some oncogenes are responsive to inducers of cytochrome P450, the enzyme system by which many carcinogens are activated.

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