Role for DNA methylation in the regulation of miR-200c and miR-141 expression in normal and cancer cells.
BACKGROUND
The microRNA-200 family participates in the maintenance of an epithelial phenotype and loss of its expression can result in epithelial to mesenchymal transition (EMT). Furthermore, the loss of expression of miR-200 family members is linked to an aggressive cancer phenotype. Regulation of the miR-200 family expression in normal and cancer cells is not fully understood.


RESULTS
Epigenetic mechanisms participate in the control of miR-200c and miR-141 expression in both normal and cancer cells. A CpG island near the predicted mir-200c/mir-141 transcription start site shows a striking correlation between miR-200c and miR-141 expression and DNA methylation in both normal and cancer cells, as determined by MassARRAY technology. The CpG island is unmethylated in human miR-200/miR-141 expressing epithelial cells and in miR-200c/miR-141 positive tumor cells. The CpG island is heavily methylated in human miR-200c/miR-141 negative fibroblasts and miR-200c/miR-141 negative tumor cells. Mouse cells show a similar inverse correlation between DNA methylation and miR-200c expression. Enrichment of permissive histone modifications, H3 acetylation and H3K4 trimethylation, is seen in normal miR-200c/miR-141-positive epithelial cells, as determined by chromatin immunoprecipitation coupled to real-time PCR. In contrast, repressive H3K9 dimethylation marks are present in normal miR-200c/miR-141-negative fibroblasts and miR-200c/miR-141 negative cancer cells and the permissive histone modifications are absent. The epigenetic modifier drug, 5-aza-2'-deoxycytidine, reactivates miR-200c/miR-141 expression showing that epigenetic mechanisms play a functional role in their transcriptional control.


CONCLUSIONS
We report that DNA methylation plays a role in the normal cell type-specific expression of miR-200c and miR-141 and this role appears evolutionarily conserved, since similar results were obtained in mouse. Aberrant DNA methylation of the miR-200c/141 CpG island is closely linked to their inappropriate silencing in cancer cells. Since the miR-200c cluster plays a significant role in EMT, our results suggest an important role for DNA methylation in the control of phenotypic conversions in normal cells.
Vrba
Lukas
L
Arizona Cancer Center, The University of Arizona, Tucson, Arizona, USA.
Jensen
Taylor J
TJ
Garbe
James C
JC
Heimark
Ronald L
RL
Cress
Anne E
AE
Dickinson
Sally
S
Stampfer
Martha R
MR
Futscher
Bernard W
BW
D002460:Cell Line; D045744:Cell Line, Tumor; D047369:Chromatin Immunoprecipitation; D018899:CpG Islands; D019175:DNA Methylation; D005786:Gene Expression Regulation; D006657:Histones / Q000378:metabolism; D006801:Humans; D035683:MicroRNAs / Q000235:genetics*; D016133:Polymerase Chain Reaction
D006657:Histones; C533895:MIRN141 microRNA, human; C533896:MIRN200 microRNA, human; D035683:MicroRNAs