Objective    To study the molecular mechanism of benzo(a)pyrene underlying the role of estrogen metabolism-related genes in human endometrial cancer cells.     Methods    Effect of benzo(a)pyrene on CYP450 was studied by exposing human endometrial cancer cells (RL95-2) to benzo(a)pyrene at various concentrations (0.016

0.8

0.4

2.0 and 10 μmol/L BP) for 12 h

or to 2 μmol/L BP for 6

12

24

36 and 48 h. RL95-2 cells were harvested and cleaved. Expressions of CYP1A1

CYP1B1 and CYP3A4 proteins in RL95-2 supernatant were detected by Western blotting. Supersome in expressed CYP450 was used as a positive control to confirm the reliability of assay methods.     Results    The expression of CYP1A1 protein was significantly increased in RL95-2 cells 12 h after they were exposed to different concentrations of benzo(a)pyrene or to 2 μmol/L BP for different periods of time

and reached it peak at 48 h

indicating that expression of CYP1A1 protein depends on the used dose and time of benzo(a)pyrene.     Conclusion    Benzo(a)pyrene can increase the expression of CYP1A1 in human endometrial cancer cells

cause changes in estrogen metabolism

and inhibit proliferation of  human endometrial cancer ells.