Benzo[a]pyrene diol epoxide suppresses retinoic acid receptor-beta2 expression by recruiting DNA (cytosine-5-)-methyltransferase 3A.

Abstract

Tobacco smoke is an important risk factor for various human cancers, including esophageal cancer. How benzo [a]pyrene diol epoxide (BPDE), a carcinogen present in tobacco smoke as well as in environmental pollution, induces esophageal carcinogenesis has yet to be defined. In this study, we investigated the molecular mechanism responsible for BPDE-suppressed expression of retinoic acid receptor-beta2 (RAR-beta2) in esophageal cancer cells. We treated esophageal cancer cells with BPDE before performing methylation-specific polymerase chain reaction (MSP) to find that BPDE induced methylation of the RAR-beta2 gene promoter. We then performed chromatin immunoprecipitation (ChIP) assays to find that BPDE recruited genes of the methylation machinery into the RAR-beta2 gene promoter. We found that BPDE recruited DNA (cytosine-5-)-methyltransferase 3 alpha (DNMT3A), but not beta (DNMT3B), in a time-dependent manner to methylate the RAR-beta2 gene promoter, which we confirmed by reverse transcription-polymerase chain reaction (RT-PCR) analysis of the reduced RAR-beta2 expression in these BPDE-treated esophageal cancer cell lines. However, BPDE did not significantly change DNMT3A expression, but it slightly reduced DNMT3B expression. DNA methylase inhibitor 5-aza-2'-deoxycytidine (5-Aza) and DNMT3A small hairpin RNA (shRNA) vector antagonized the effects of BPDE on RAR-beta2 expressions. Transient transfection of the DNMT3A shRNA vector also antagonized BPDE's effects on expression of RAR-beta2, c-Jun, phosphorylated extracellular signal-regulated protein kinases 1/2 (ERK1/2), and cyclooxygenase-2 (COX-2), suggesting a possible therapeutic effect. The results of this study form the link between the esophageal cancer risk factor BPDE and the reduced RAR-beta2 expression.

• Authors: Fei Ye, Xiao-Chun Xu
• Journal: Molecular cancer (Mol Cancer) Vol. 9 Pg. 93 (Apr 28 2010) ISSN: 1476-4598 [Electronic] England
• PMID: 20426865 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Carcinogens
• DNMT3A protein, human
• Receptors, Retinoic Acid
• retinoic acid receptor beta
• 7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide
• DNA (Cytosine-5-)-Methyltransferases
• DNA Methyltransferase 3A
• DNA methyltransferase 3B

Topics

• 7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide (toxicity)
• Blotting, Northern
• Blotting, Western
• Carcinogens (toxicity)
• Cell Line, Tumor
• Chromatin Immunoprecipitation
• DNA (Cytosine-5-)-Methyltransferases (genetics, metabolism)
• DNA Methylation
• DNA Methyltransferase 3A
• Esophageal Neoplasms (genetics, metabolism)
• Gene Expression (drug effects)
• Humans
• Promoter Regions, Genetic
• Receptors, Retinoic Acid (biosynthesis, genetics)
• Reverse Transcriptase Polymerase Chain Reaction
• Transfection