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

Abstract

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 kappaB (NF-kappaB) 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-kappaB 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.

• Authors: Minmin Sun, Jinchun Zhang, Shilian Liu, Yanxin Liu, Dexian Zheng
• Journal: Oncology reports (Oncol Rep) Vol. 19 Issue 1 Pg. 177-85 (Jan 2008) ISSN: 1021-335X [Print] Greece
• PMID: 18097593 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Antineoplastic Agents
• Immunoglobulins
• RNA, Messenger
• Receptors, TNF-Related Apoptosis-Inducing Ligand
• SP1 antigen
• Adenosine

Topics

• Adenosine (pharmacology)
• Antineoplastic Agents (pharmacology)
• Base Sequence
• Blotting, Western
• Carcinoma, Hepatocellular (metabolism)
• Cell Line, Tumor
• Electrophoretic Mobility Shift Assay
• Humans
• Immunoglobulins (drug effects, metabolism)
• Immunoprecipitation
• Liver Neoplasms (metabolism)
• Molecular Sequence Data
• Promoter Regions, Genetic (drug effects)
• Protein Biosynthesis (drug effects)
• RNA, Messenger (analysis)
• Receptors, TNF-Related Apoptosis-Inducing Ligand (biosynthesis, drug effects, genetics)
• Reverse Transcriptase Polymerase Chain Reaction
• Transcription, Genetic (drug effects)
• Up-Regulation