Abstract:

Objective: To investigate the role of epidermal growth factor receptor (EGFR) in the regulation of B[a]P-induced silent information regulator 1 (SIRT1) activation in the human bronchial epithelial cells (BEAS-2B),and to clarify the relationship between EGFR/SIRT1 signal transduction pathway and the occurrence and development lung cancer. Methods: The prediction analysis of transcriptional factor binding sites of SIRT1 was performed by MOTIF Search^TM software. The primary cultivated BEAS-2B cells were divided into control group (without B[a]P exposure) and B[a]P groups (the cells were exposed to B[a]P for 6,12,24,48 h). RT-PCR and Western blotting method were carried out to detect the EGFR mRNA and protein expression levels. The BEAS-2B cells transfected with SIRT1 promotor luciferase reporter gene plasmid were treated with human epidermal growth factor (hEGF) and Genistein (tyrosine protein kinase inhibitor) for 24 h,the morphology of BEAS-2B cells was observed by inverted microscope,and luciferase reporter assay was used to test the SIRT1 transcriptional activity. The human lung tissue biopsies were acquired and the immunohistochemical analysis was used to determine the EGFR protein expression level. Results: The transcriptional factor binding sites of SIRT1 contained EGF, 2Fe-2S and vWF. Compared with control group,the expression levels of EGFR mRNA in B[a]P groups were increased in a time-dependent manner,and reached the peak at 12 h (P < 0.05);the EGFR protein expression levels were also increased (P < 0.05).The SIRT1 luciferase activity in hEGF group was increased compared with control group (P < 0.05);when hEGF and B[a]P worked together,the SIRT1 luciferase activity was increased even further (P < 0.001). The cells showed arrangement and morphologic changes gradually when the B[a]P concentration was above 30 μmol·L^-1. Genistein (30 μmol·L^-1) inhibited the increase of SIRT1 luciferase activity induced by B[a]P ,and there was significant difference compared with control group(P < 0.05).The immunohistochemistry results showed that EGFR expression level in lung cancer tissue was higher than that in normal lung tissue (P < 0.001). Conclusion: EGFR can regulate the B[a]P-induced SIRT1 expression in BEAS-2B cells,and to cause lung chronic inflammation; EGFR/SIRT1 signal transduction pathway may play a role in the occurrence and development of lung cancer.

Key words: benzo(a)pyrene, epidermal growth factor receptor, silent information regulator 1, signaling transduction