MicroRNA-dependent regulation of DNA methyltransferase-1 and tumor suppressor gene expression by interleukin-6 in human malignant cholangiocytes

Abstract

Although the inflammation-associated cytokine Interleukin-6 (IL-6) has been implicated in cholangiocarcinoma growth, the relationship between IL-6 and oncogenic changes is unknown. IL-6 can increase expression of DNA methyltransferase 1 (DNMT-1) and epigenetically regulate the expression of several genes, including microRNAs (miRNAs). DNMT-1 up-regulation occurs in hepatobiliary cancers and is associated with a poor prognosis. To understand the potential regulation of DNMT-1 by IL-6 dependent miRNAs, we examined the expression of a group of miRNAs which have sequence complementarity to the 3′-UTR of DNMT-1, namely miR-148a, miR-152 and miR-301. The expression of these miRNAs was decreased in cholangiocarcinoma cells. Moreover, the expression of all three miRNAs was decreased in IL-6 over-expressing malignant cholangiocytes in vitro and in tumor cell xenografts. There was a concomitant decrease in expression of the methylation-sensitive tumor suppressor genes Rassf1a, and p16INK4a. Using luciferase reporter constructs, DNMT-1 was verified as a target for miR-148a and miR-152. Precursors to miR-148a and miR-152 decreased DNMT-1 protein expression, increased Rassf1a and p16INK4a expression and reduced cell proliferation. Conclusion These data indicate that IL-6 can regulate the activity of DNMT-1 and expression of methylation-dependent tumor suppressor genes by modulation of miR-148a and miR-152, and provide a link between this inflammation-associated cytokines and oncogenesis in cholangiocarcinoma.

MicroRNA-148a Can Regulate Runt-Related Transcription Factor 3 Gene Expression via Modulation of DNA Methyltransferase 1 in Gastric Cancer

“…Thus miR148a could downregulate DNMT expression, which decreased the methylation of RUNX3, and RUNX3 protein levels increased. Our findings are consistent with several studies that provide evidence for miRNA-induced regulation of promoter methylation through DNMTs (Braconi et al, 2010;Garzon et al, 2009;Li et al, 2012;Pan et al, 2010;Wang et al, 2012;Zhao et al, 2011).…”

“…This suggests that miR-148a may not directly target RUNX3. Previous studies have already confirmed that miR-148a could modulate DNMT1 and DNMT3B protein expression (Braconi et al, 2010;Duursma et al, 2008;Pan et al, 2010;Zhu et al, 2012). Therefore, our results show that overexpression of miR148a in gastric cancer cells might upregulate RUNX3 expression through the modulation of DNMTs.…”

“…In our previous studies, we confirmed that miR-148a was significantly downregulated in gastric cancer (Zhu et al, 2012). Furthermore, it has been verified that DNMT1 is a target of miR-148a (Braconi et al, 2010;Pan et al, 2010). Therefore, we hypothesized that miR-148a could regulate RUNX3 gene expression through modulation of DNMT1-dependent DNA methylation in gastric cancer.…”

miR‐148a promotes plasma cell differentiation and targets the germinal center transcription factors Mitf and Bach2

“…3A, right). The regulation of DNMT1 by miR-148a has been reported in cholangiocytes and chronically activated CD4-positive T cells [22,23], and miR-148a-mediated reduction of Bim abundance was recently confirmed in chronically activated T cells [24] and glioblastoma tumor cells [34]; thus, those miR-148a targets were not included in the luciferase assays.To determine whether miR-148a mRNA targets that were confirmed in HEK293 cells by a dual luciferase assay are also reduced in B cells upon miR-148a expression, we either overexpressed miR-148a or prevented its upregulation in activated B cells and determined the effect on the abundance of the corresponding proteins by Western blotting. The analysis of GFP + cells from miR-148a/GFP-or control/GFP-vector transduced 1-day-old splenic B-cell cultures confirmed that DNMT1, Bim, and Mitf were reduced at protein levels in LPS blasts overexpressing miR-148a when compared to the corresponding β-actin loading control signals (Fig.…”

Application of omic technologies in cancer research

“…Such alterations have been shown to be present in many cancers, including breast cancer 20 and cholangiocarcinoma. 21 Hypermethylation of the paired-like homeodomain transcription factor 2 gene has been shown to be a prognostic indicator of disease recurrence in prostate cancer. 22 The Epigenome can also be influenced by altered chromatin regulation resulting from histone modifications.…”