title: Hypermethylation and silencing of the putative tumor suppressor Tazarotene-induced gene 1 in human cancers.
abstract: A variety of tumor suppressor genes are down-regulated by hypermethylation during carcinogenesis. Using methylated CpG amplification-representation difference analysis, we identified a DNA fragment corresponding to the Tazarotene-induced gene 1 (TIG1) promoter-associated CpG island as one of the genes hypermethylated in the leukemia cell line K562. Because TIG1 has been proposed to act as a tumor suppressor, we tested the hypothesis that cytosine methylation of the TIG1 promoter suppresses its expression and causes a loss of responsiveness to retinoic acid in some neoplastic cells. We examined TIG1 methylation and expression status in 53 human cancer cell lines and 74 primary tumors, including leukemia and head and neck, breast, colon, skin, brain, lung, and prostate cancer. Loss of TIG1 expression was strongly associated with TIG1 promoter hypermethylation (P < 0.001). There was no correlation between TIG1 promoter methylation and that of retinoid acid receptor beta2 (RARbeta2), another retinoic-induced putative tumor suppressor gene (P = 0.78). Treatment with the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine for 5 days restored TIG1 expression in all eight silenced cell lines tested. TIG1 expression was also inducible by treatment with 1 micro M all-trans-retinoic acid for 3 days except in densely methylated cell lines. Treatment of the K562 leukemia cells with demethylating agent combined with all-trans-retinoic acid induced apoptosis. These findings indicate that silencing of TIG1 promoter by hypermethylation is common in human cancers and may contribute to the loss of retinoic acid responsiveness in some neoplastic cells.
authors.affiliation: Department of Leukemia, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA. eyoussef@mdanderson.org
authors.forename: Emile M
authors.initials: EM
authors.lastname: Youssef
authors.forename: Xu-qi
authors.initials: XQ
authors.lastname: Chen
authors.forename: Eisaku
authors.initials: E
authors.lastname: Higuchi
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Kondo
authors.forename: Guillermo
authors.initials: G
authors.lastname: Garcia-Manero
authors.forename: Reuben
authors.initials: R
authors.lastname: Lotan
authors.forename: Jean-Pierre J
authors.initials: JP
authors.lastname: Issa
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D001374:Azacitidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D019175:DNA Methylation / Q000187:drug effects; D000077209:Decitabine; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D020868:Gene Silencing / Q000187:drug effects; D016147:Genes, Tumor Suppressor; D006801:Humans; D008565:Membrane Proteins; D009369:Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D011401:Promoter Regions, Genetic; D014176:Protein Biosynthesis; D011506:Proteins / Q000235:genetics*; D018168:Receptors, Retinoic Acid / Q000235:genetics; D014212:Tretinoin / Q000494:pharmacology
chemical_list: D000970:Antineoplastic Agents; D004791:Enzyme Inhibitors; D008565:Membrane Proteins; D011506:Proteins; C452562:RARRES1 protein, human; D018168:Receptors, Retinoic Acid; C082925:retinoic acid receptor beta; D014212:Tretinoin; D000077209:Decitabine; D001374:Azacitidine