Methylation mediated silencing of MicroRNA-1 gene and its role in hepatocellular carcinogenesis.
MicroRNAs (miR) are a class of small ( approximately 21 nucleotide) noncoding RNAs that, in general, negatively regulate gene expression. Some miRs harboring CGIs undergo methylation-mediated silencing, a characteristic of many tumor suppressor genes. To identify such miRs in liver cancer, the miRNA expression profile was analyzed in hepatocellular carcinoma (HCC) cell lines treated with 5-azacytidine (DNA hypomethylating agent) and/or trichostatin A (histone deacetylase inhibitor). The results showed that these epigenetic drugs differentially regulate expression of a few miRs, particularly miR-1-1, in HCC cells. The CGI spanning exon 1 and intron 1 of miR-1-1 was methylated in HCC cell lines and in primary human HCCs but not in matching liver tissues. The miR-1-1 gene was hypomethylated and activated in DNMT1-/- HCT 116 cells but not in DNMT3B null cells, indicating a key role for DNMT1 in its methylation. miR-1 expression was also markedly reduced in primary human hepatocellular carcinomas compared with matching normal liver tissues. Ectopic expression of miR-1 in HCC cells inhibited cell growth and reduced replication potential and clonogenic survival. The expression of FoxP1 and MET harboring three and two miR-1 cognate sites, respectively, in their respective 3'-untranslated regions, was markedly reduced by ectopic miR-1. Up-regulation of several miR-1 targets including FoxP1, MET, and HDAC4 in primary human HCCs and down-regulation of their expression in 5-AzaC-treated HCC cells suggest their role in hepatocarcinogenesis. The inhibition of cell cycle progression and induction of apoptosis after re-expression of miR-1 are some of the mechanisms by which DNA hypomethylating agents suppress hepatocarcinoma cell growth.
Datta
Jharna
J
Department of Molecular and Cellular Biochemistry, College of Pharmacy, and Comprehensive Cancer Center, Ohio State University, Columbus, Ohio 43210, USA.
Kutay
Huban
H
Nasser
Mohd W
MW
Nuovo
Gerard J
GJ
Wang
Bo
B
Majumder
Sarmila
S
Liu
Chang-Gong
CG
Volinia
Stefano
S
Croce
Carlo M
CM
Schmittgen
Thomas D
TD
Ghoshal
Kalpana
K
Jacob
Samson T
ST
D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000235:genetics; D006528:Carcinoma, Hepatocellular / Q000235:genetics*; D002453:Cell Cycle / Q000235:genetics; D049109:Cell Proliferation; D016000:Cluster Analysis; D018899:CpG Islands / Q000187:drug effects / Q000235:genetics; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000037:antagonists & inhibitors; D019175:DNA Methylation; D018450:Disease Progression; D004791:Enzyme Inhibitors / Q000494:pharmacology; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing / Q000187:drug effects / Q000502:physiology; D045325:HCT116 Cells; D056572:Histone Deacetylase Inhibitors; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics*; D035683:MicroRNAs / Q000235:genetics* / Q000502:physiology*; D020411:Oligonucleotide Array Sequence Analysis; D010641:Phenotype; D014162:Transfection; D014407:Tumor Cells, Cultured
D000970:Antineoplastic Agents; D004791:Enzyme Inhibitors; D056572:Histone Deacetylase Inhibitors; D035683:MicroRNAs; D004248:DNA (Cytosine-5-)-Methyltransferases