Cell cycle alterations of human embryo lung fibroblasts induced by benzo(a)pyrene is positively regulated by cyclin D1 and CDK4

OBJECTIVE: To study the effects of benzo(a)pyrene (B(a)P) on the cell cycle distributions and expression of cell cycle regulated protein cyclin D1 and CDK4 in human embryo lung fibroblasts (HELF), and to investigate the relationship between the expression of both cyclin D1 and CDK4 proteins and the cell cycle alterations. METHODS: Antisense cyclin D1 cDNA and antisense CDK4 cDNA were respectively transfected into HELF cells, and two stable transfectants were established. The protein expression levels of cyclin D1 and CDK4 were detected by western-blotting assay when HELF were treated with B(a)P at the doses of 0.1, 0.5, 2.5 and 12.5 micromol/L B(a)P for 24h. And the flow cytometry assay was used for detecting the cell cycle effects in HELF cells and two stable transfectants. RESULTS: Two cell lines respectively expressed antisense cyclin D1 RNA and antisense CDK4 RNA were successively established in the present study. The protein expressions of cyclin D1 were greatly increased by B(a)P treatment, whereas B(a)P had no significant effects on the protein levels of CDK4. The cell cycle distributions were significantly altered at the level of 2.5 micromol/L B(a)P for 24h treatment. The cell numbers in G1 phase significantly decreased. However, the cell numbers in S phase significantly increased. CONCLUSION: Cyclin D1 and CDK4 could be active genes and could positively regulate the cell cycle alterations induced by B(a)P.