EFFECT OF CYTOCHROME-P450 INDUCERS ON EXPRESSION OF ONCOGENES AND A TUMOR-SUPPRESSOR GENE IN HUMAN COLON-CANCER CELLS

To examine the possibility that chemical inducers of cytochrome P450 m ay 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 phenobar bital-hydrocortisone (Pb-Hc). Three forms of cytochrome P450 (CYP1A1, CYP1A2 and CYP2E1) were detected in the colon cell line and all of the m 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 t he time-point selected. Interestingly, c-fos expression was the most d ramatically altered by different treatments, showing repression with a ll of the treatments. These data show that some oncogenes are responsi ve to inducers of cytochrome P450, the enzyme system by which many car cinogens are activated.