title: Reduction in promotor methylation utilizing EGCG (epigallocatechin-3-gallate) restores RXRα expression in human colon cancer cells.
abstract: Silencing of regulatory genes through hypermethylation of CpG islands is an important mechanism in tumorigenesis. In colon cancer, RXRα, an important dimerization partner with other nuclear transcription factors, is silenced through this mechanism. We previously found that colon tumors in ApcMin/+ mice had diminished levels of RXRα protein and expression levels of this gene were restored by treatment with a green tea intervention, due to reduced promoter methylation of RXRα. We hypothesized that CIMP+ cell lines, which epigenetically silence key regulatory genes would also evidence silencing of RXRα and EGCG treatment would restore its expression. We indeed found EGCG to restore RXRα activity levels in the human cell lines, in a dose dependent manner and reduced RXRα promoter methylation. EGCG induced methylation changes in several other colon cancer related genes but did not cause a decrease in global methylation. Numerous epidemiological reports have shown the benefits of green tea consumption in reducing colon cancer risk but to date no studies have shown that the risk reduction may be related to the epigenetic restoration by tea polyphenols. Our results show that EGCG modulates the reversal of gene silencing involved in colon carcinogenesis providing a possible avenue for colon cancer prevention and treatment.
authors.affiliation: Department of Molecular Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA.
authors.forename: Jay
authors.initials: J
authors.lastname: Morris
authors.affiliation: Department of Cell & Molecular Pharmacology, Medical University of South Carolina, Charleston, SC 29425, USA.
authors.forename: Vondina R
authors.initials: VR
authors.lastname: Moseley
authors.affiliation: Department of Molecular Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA.
authors.forename: April B
authors.initials: AB
authors.lastname: Cabang
authors.affiliation: Department of Cell & Molecular Pharmacology, Medical University of South Carolina, Charleston, SC 29425, USA.
authors.forename: Katie
authors.initials: K
authors.lastname: Coleman
authors.affiliation: Department of Public Health Science, Medical University of South Carolina, Charleston, SC 29425, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Wei
authors.affiliation: Department of Biostatistics & Epidemiology, Medical University of South Carolina, Charleston, SC 29425, USA.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Garrett-Mayer
authors.affiliation: Department of Molecular Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Wargovich
mesh_terms: D016588:Anticarcinogenic Agents / Q000494:pharmacology*; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000473:pathology*; D019175:DNA Methylation / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D011401:Promoter Regions, Genetic / Q000235:genetics; D047490:Retinoid X Receptor alpha / Q000096:biosynthesis*; D013662:Tea
chemical_list: D016588:Anticarcinogenic Agents; D047490:Retinoid X Receptor alpha; D013662:Tea; D002392:Catechin; C045651:epigallocatechin gallate
keywords: EGCG; RXRα; colon cancer; epigenetics; methylation