title: DNA-hypomethylating agent, 5'-azacytidine, induces cyclooxygenase-2 expression via the PI3-kinase/Akt and extracellular signal-regulated kinase-1/2 pathways in human HT1080 fibrosarcoma cells.
abstract: The cytosine analogue 5'-azacytidine (5'-aza) induces DNA hypomethylation by inhibiting DNA methyltransferase. In clinical trials, 5'-aza is widely used in epigenetic anticancer treatments. Accumulated evidence shows that cyclooxygenase-2 (COX-2) is overexpressed in various cancers, indicating that it may play a critical role in carcinogenesis. However, few studies have been performed to explore the molecular mechanism underlying the increased COX-2 expression. Therefore, we tested the hypothesis that 5'-aza regulates COX-2 expression and prostaglandin E2 (PGE2) production. The human fibrosarcoma cell line HT1080, was treated with various concentrations of 5'-aza for different time periods. Protein expressions of COX-2, DNA (cytosine-5)-methyltransferase 1 (DNMT1), pAkt, Akt, extracellular signal-regulated kinase (ERK), and phosphorylated ERK (pERK) were determined using western blot analysis, and COX-2 mRNA expression was determined using RT-PCR. PGE2 production was evaluated using the PGE2 assay kit. The localization and expression of COX-2 were determined using immunofluorescence staining. Treatment with 5'-aza induces protein and mRNA expression of COX-2. We also observed that 5'-aza-induced COX-2 expression and PGE2 production were inhibited by S-adenosylmethionine (SAM), a methyl donor. Treatment with 5'-aza phosphorylates PI3-kinase/Akt and ERK-1/2; inhibition of these pathways by LY294002, an inhibitor of PI3-kinase/Akt, or PD98059, an inhibitor of ERK-1/2, respectively, prevents 5'-aza-induced COX-2 expression and PGE2 production. Overall, these observations indicate that the hypomethylating agent 5'-aza modulates COX-2 expression via the PI3-kinase/Akt and ERK-1/2 pathways in human HT1080 fibrosarcoma cells.
authors.affiliation: Department of Biological Sciences, College of Natural Sciences, Kongju National University, Gongju 182, Republic of Korea.
authors.forename: Seon-Mi
authors.initials: SM
authors.lastname: Yu
authors.affiliation: Department of Biological Sciences, College of Natural Sciences, Kongju National University, Gongju 182, Republic of Korea.
authors.forename: Song-Ja
authors.initials: SJ
authors.lastname: Kim
mesh_terms: D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D001374:Azacitidine / Q000494:pharmacology*; D015153:Blotting, Western; D045744:Cell Line, Tumor; D051546:Cyclooxygenase 2 / Q000096:biosynthesis*; D015232:Dinoprostone / Q000096:biosynthesis; D005354:Fibrosarcoma / Q000201:enzymology / Q000473:pathology*; D005455:Fluorescent Antibody Technique; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects*
chemical_list: D000964:Antimetabolites, Antineoplastic; D051546:Cyclooxygenase 2; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D015232:Dinoprostone; D001374:Azacitidine