title: Energy restriction-mimetic agents induce apoptosis in prostate cancer cells in part through epigenetic activation of KLF6 tumor suppressor gene expression.
abstract: Although energy restriction has been recognized as an important target for cancer prevention, the mechanism by which energy restriction-mimetic agents (ERMAs) mediate apoptosis remains unclear. By using a novel thiazolidinedione-derived ERMA, CG-12 (Wei, S., Kulp, S. K., and Chen, C. S. (2010) J. Biol. Chem. 285, 9780-9791), vis-à-vis 2-deoxyglucose and glucose deprivation, we obtain evidence that epigenetic activation of the tumor suppressor gene Kruppel-like factor 6 (KLF6) plays a role in ERMA-induced apoptosis in LNCaP prostate cancer cells. KLF6 regulates the expression of many proapoptotic genes, and shRNA-mediated KLF6 knockdown abrogated the ability of ERMAs to induce apoptosis. Chromatin immunoprecipitation analysis indicates that this KLF6 transcriptional activation was associated with increased histone H3 acetylation and histone H3 lysine 4 trimethylation occupancy at the promoter region. Several lines of evidence demonstrate that the enhancing effect of ERMAs on these active histone marks was mediated through transcriptional repression of histone deacetylases and H3 lysine 4 demethylases by down-regulating Sp1 expression. First, putative Sp1-binding elements are present in the promoters of the affected histone-modifying enzymes, and luciferase reporter assays indicate that site-directed mutagenesis of these Sp1 binding sites significantly diminished the promoter activities. Second, shRNA-mediated knockdown of Sp1 mimicked the repressive effect of energy restriction on these histone-modifying enzymes. Third, ectopic Sp1 expression protected cells from the repressive effect of CG-12 on these histone-modifying enzymes, thereby abolishing the activation of KLF6 expression. Together, these findings underscore the intricate relationship between energy restriction and epigenetic regulation of tumor suppressor gene expression, which has therapeutic relevance to foster novel strategies for prostate cancer therapy.
authors.affiliation: Division of Medicinal Chemistry, College of Pharmacy, Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: Chun-Han
authors.initials: CH
authors.lastname: Chen
authors.forename: Po-Hsien
authors.initials: PH
authors.lastname: Huang
authors.forename: Po-Chen
authors.initials: PC
authors.lastname: Chu
authors.forename: Mei-Chuan
authors.initials: MC
authors.lastname: Chen
authors.forename: Chih-Chien
authors.initials: CC
authors.lastname: Chou
authors.forename: Dasheng
authors.initials: D
authors.lastname: Wang
authors.forename: Samuel K
authors.initials: SK
authors.lastname: Kulp
authors.forename: Che-Ming
authors.initials: CM
authors.lastname: Teng
authors.forename: Qianben
authors.initials: Q
authors.lastname: Wang
authors.forename: Ching-Shih
authors.initials: CS
authors.lastname: Chen
mesh_terms: D000107:Acetylation / Q000187:drug effects; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D045744:Cell Line, Tumor; D044127:Epigenesis, Genetic / Q000187:drug effects* / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects* / Q000235:genetics; D055785:Gene Knockdown Techniques; D006655:Histone Deacetylases / Q000235:genetics / Q000378:metabolism; D006657:Histones / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D000075723:Kruppel-Like Factor 6; D051741:Kruppel-Like Transcription Factors / Q000096:biosynthesis* / Q000235:genetics; D008297:Male; D008745:Methylation / Q000187:drug effects; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis* / Q000235:genetics; D020218:Response Elements / Q000235:genetics; D016329:Sp1 Transcription Factor / Q000235:genetics / Q000378:metabolism; D045162:Thiazolidinediones / Q000494:pharmacology*; D025521:Tumor Suppressor Proteins / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D006657:Histones; D007004:Hypoglycemic Agents; C105465:KLF6 protein, human; D000075723:Kruppel-Like Factor 6; D051741:Kruppel-Like Transcription Factors; D011518:Proto-Oncogene Proteins; D016329:Sp1 Transcription Factor; D045162:Thiazolidinediones; D025521:Tumor Suppressor Proteins; D006655:Histone Deacetylases; C039671:ciglitazone