title: The methyltransferase inhibitor 5-aza-2-deoxycytidine induces apoptosis via induction of 15-lipoxygenase-1 in colorectal cancer cells.
abstract: DNA methylation by DNA methyltransferases in CpG-rich promoter regions of genes is a well-described component of epigenetic silencing in human cells. Dysregulation of this process in cancer cells may lead to hypermethylation of promoter CpG islands, thus disabling transcription initiation of certain genes, such as tumor suppressor genes. Reversing epigenetic silencing and up-regulating genes involved in preventing or reversing the malignant phenotype has become a new, important targeted approach for cancer prevention and treatment. Therefore, methyltransferase inhibitors (MTI) have emerged recently as promising chemotherapeutic or preventive agents. The potent MTI 5-aza-2-deoxycytidine (5-Azadc) causes growth arrest, differentiation, and/or apoptosis of many tumor types in vitro and in vivo. The present study shows that low micromolar concentrations of 5-Azadc induce the expression of 15-lipoxygenase-1 (15-LOX-1) in human colorectal cancer cells. The expression of 15-LOX-1 correlates with 5-Azadc-induced increases in 13-S-hydroxyoctadecadienoic acid levels, growth inhibition, and apoptosis in these cells. Furthermore, specific inhibition of 15-LOX-1 by pharmacologic means or small interfering RNA significantly reduced the 5-Azadc-induced effects. These novel findings are the first demonstration of a mechanistic link between the induction of 15-LOX-1 by a MTI and apoptosis in cancer cells. This result has important implications for the study of 5-Azadc and other MTIs in the prevention and therapy of colorectal cancer and supports future investigations of the mechanisms by which MTIs up-regulate 15-LOX-1.
authors.affiliation: Department of Clinical Cancer Prevention, The University of Texas M.D. Anderson Cancer Center, Unit 1360, P.O. Box 301439, Houston, Texas 77230-1439, USA.
authors.forename: Linda C
authors.initials: LC
authors.lastname: Hsi
authors.forename: Xiaopei
authors.initials: X
authors.lastname: Xi
authors.forename: Yuanqing
authors.initials: Y
authors.lastname: Wu
authors.forename: Scott M
authors.initials: SM
authors.lastname: Lippman
mesh_terms: D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis; D001093:Arachidonate 15-Lipoxygenase / Q000096:biosynthesis*; D001374:Azacitidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D015153:Blotting, Western; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D015179:Colorectal Neoplasms / Q000201:enzymology* / Q000378:metabolism; D053938:DNA Fragmentation; D017931:DNA Primers / Q000737:chemistry; D000077209:Decitabine; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D044127:Epigenesis, Genetic; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D016147:Genes, Tumor Suppressor; D006801:Humans; D034741:RNA, Small Interfering / Q000378:metabolism; D013997:Time Factors; D014158:Transcription, Genetic; D015854:Up-Regulation
chemical_list: D000964:Antimetabolites, Antineoplastic; D000970:Antineoplastic Agents; D017931:DNA Primers; D004791:Enzyme Inhibitors; D034741:RNA, Small Interfering; D000077209:Decitabine; D001093:Arachidonate 15-Lipoxygenase; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D001374:Azacitidine