Benzo[a]pyrene-induced cell cycle progression is through ERKs/cyclin D1 pathway and requires the activation of JNKs and p38 mapk in human diploid lung fibroblasts.
Treatment of cells with carcinogen Benzo[a]pyrene (B[a]P) allows cells to evade G1 arrest and induces cells abnormal proliferation. However, the mechanisms of its action at cellular level are not well understood. To address this question, normal human embryo lung diploid fibroblasts (HELF) were selected in the present study. We found that exposure of cells with 2.5 microM of B[a]P for 24 h resulted in a decrease of G1 population by 11.9% (P < 0.05) and a increase of S population by 17.2% (P < 0.05). Treatment of cells with B[a]P also caused dose-related activation of MAPK and induction of cyclin D1 protein expression, whereas the CDK4 protein levels were not significantly affected by B[a]P. Overexpression of cyclin D1 protein stimulated by B[a]P was significantly inhibited by 50 microM AG126 (an inhibitor of ERK1/2), but not by 25 microM SP600125 (an inhibitor of JNK1/2) or 5 microM SB203580 (an inhibitor of p38 mapk), suggesting that B[a]P-induced cyclin D1 expression was only regulated by ERK1/2 pathway. However, AG126, SP600125 or SB203580 led to cell cycle significantly arrested in G1 phase, indicating that ERK1/2, JNK1/2 and p38 mapk pathways are all required for B[a]P-induced G1/S transition. In addition, HELF cells transfecting with antisense cyclin D1 cDNA or antisense CDK4 cDNA showed significantly G1 arrest after B[a]P stimulation. These results suggested that B[a]P exposure accelerated the G1-->S transition by activation of MAPK signaling pathways. Cyclin D1 and CDK4 are rate-limiting regulators of the G1-->S transition and expression of cyclin D1 is predominantly regulated by ERK1/2 pathway in HELF cells.
Du
Hong Ju
HJ
Institute for Environmental Health and Related Product Safety, Chinese Center for Disease Control and Prevention, 29 Nan Wei Road, Beijing, 100050, P.R. China.
Tang
Ning
N
Liu
Bing Ci
BC
You
Bao Rong
BR
Shen
Fu Hai
FH
Ye
Meng
M
Gao
Ai
A
Huang
Chuan shu
Cs
D001564:Benzo(a)pyrene / Q000494:pharmacology*; D002453:Cell Cycle / Q000187:drug effects*; D019938:Cyclin D1 / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005347:Fibroblasts / Q000201:enzymology / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007399:Interphase / Q000187:drug effects; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008168:Lung / Q000166:cytology; D020935:MAP Kinase Signaling System / Q000187:drug effects; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
D019938:Cyclin D1; D001564:Benzo(a)pyrene; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases