Sp1 is involved in 8-chloro-adenosine-upregulated death receptor 5 expression in human hepatoma cells

作者：Sun, Minmin; Zhang, Jinchun; Liu, Shilian; Liu, Yanxin; Zheng, Dexian^*

来源：Oncology Reports, 2008, 19(1): 177-185.

• Sp1
• 8-chloro-adenosine
• NF-kappa B
• death receptor 5
• hepatoma cells

8-Chloro-adenosine (8-Cl-Ado) is an adenosine derivative, which inhibits proliferation and induces apoptosis in various tumor cells. Subtoxic concentration of 8-Cl-Ado sensitizes human hepatoma cells to tumor necrosis factor-related apoptosis inducing ligand (TRAIL)-triggered apoptosis. However, the molecular mechanism by which TRAIL cytotoxicity is amplified by 8-Cl-Ado is unknown. In the present study, we demonstrated by Western blot and real-time PCR that 8-Cl-Ado selectively up-regulated death receptor 5 (DR5), but not death receptor 4 (DR4), at both protein and RNA levels in human hepatoma. cell line BEL-7402. Analysis of the transcriptional regulation of DR5 expression by using Dual-Luciferase reporter assay system demonstrated that the 5'-flanking fragment -207 to -145 upstream to the ATG site within the DR5 promoter region was responsible for the 8-Cl-Ado-upregulated DR5 expression. Electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) confirmed that 8-Cl-Ado treatment facilitated transcription factor Sp1 binding to its cis-element -198/-189 in the DR5 promoter, suggesting that Sp1 is at least one of the 8-Cl-Ado-responsive transcription factors. However, we observed that nuclear factor kappa B (NF-kappa B) activity remained invariable in the cells treated with 8-Cl-Ado. These data allowed us to draw a conclusion that 8-Cl-Ado-enhanced DR5 expression is regulated by Sp1 binding to the -198/-189 cis-element in DR5 promoter without affecting NF-kappa B activity in the hepatoma cells. This study may shed light on further screening the regulators of DR5 expression and developing novel therapeutic drugs for liver cancer.

• 出版日期2008-1
• 单位中国医学科学院北京协和医院