Role for DNA Methylation in the Regulation of miR-200c and miR-141 Expression in Normal and Cancer Cells

Abstract

BackgroundThe 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.Methodology/Principal FindingsEpigenetic 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/SignificanceWe 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.

miR-200a Regulates Nrf2 Activation by Targeting Keap1 mRNA in Breast Cancer Cells

“…DNA hypermethylation has been found to be associated with miR-200 family silencing in breast cancer (28). We find that treatment with epigenetic therapy (the HDAC inhibitor SAHA) can lead to re-expression of miR-200a in breast cancer cells.…”

Regulation of Vascular Endothelial Growth Factor Signaling by miR-200b

“…Recent studies showed that epigenetic mechanisms are involved in the regulation of miR-200 expression (Vrba et al, 2010;Wiklund et al, 2010) Two recent papers reported that miR-200b is involved in angiogenesis. As stated earlier, miR-200b targets Ets-1 and inhibits angiogenic activity of HMECs (Chan et al, 2011).…”

Smad3 regulates E-cadherin via miRNA-200 pathway

“…Previous reports showed that miR-200 family members were downregulated in many tumors, including breast, pancreatic and bladder cancers because of hypermethylation of the miR-200 promoter Neves et al, 2010;Vrba et al, 2010;Wiklund et al, 2011). To test whether the downregulation of miR-200 family members in SNU484-LPCX cells resulted from miR-200 promoter hypermethylation, we treated SNU484-LPCX cells with 5-aza-2 0 -deoxycytidine.…”