3,6-Dihydroxyflavone Suppresses Breast Carcinogenesis by Epigenetically Regulating miR-34a and miR-21

Abstract

Our previous study selected a promising chemopreventive agent 3,6-dihydroxyflavone (3,6-DHF) and found that 3,6-DHF significantly upregulates miR-34a and downregulates miR-21 in breast carcinogenesis, yet the upstream and downstream events of the anticancer mechanism remain unclear. The present study showed that 3,6-DHF cotreatment effectively inhibits carcinogens-induced breast carcinogenic transformation in human breast epithelial MCF10A cells. The data revealed the significant downregulation of miR-34a and upregulation of miR-21 in breast carcinogenesis, which could be mitigated by 3,6-DHF treatment. Methylation-specific PCR detections showed that 3,6-DHF inhibits the hypermethylation of the miR-34a promoter. Further studies indicated that 3,6-DHF is an effective methyltransferase (DNMT)1 inhibitor, docking to the putative cytosine pocket of the protein, and thus decreases the DNMT activity in a dose-dependent manner. Moreover, the ChIP-qPCR analysis for histone modifications showed that 3,6-DHF treatment significantly lowers the H3K9-14ac on the miR-21 promoter. In addition, our study revealed that 3,6-DHF represses the PI3K/Akt/mTOR signaling pathway in breast carcinogenesis in vitro and in vivo. Inhibition of miR-34a or overexpression of miR-21 significantly reduced the effects of 3,6-DHF on Notch-1 and PTEN, and consequently weakened the suppression of 3,6-DHF on PI3K/ Akt/mTOR. We concluded that 3,6-DHF upregulates miR-34a via inhibiting DNMT1 and hypermethylation, whereas downregulates miR-21 by modulating histone modification, and consequently suppresses the PI3K/Akt/mTOR signaling pathway in breast carcinogenesis. Cancer Prev Res; 8(6); 509-17. Ó2015 AACR.

The DNMT1/miR-34a/FOXM1 Axis Contributes to Stemness of Liver Cancer Cells

“…Aberrant regulation of miRNAs is involved in controlling stemness in multiple cancers by modulating stemness-related genes [39][40][41]. MiR-34a is a tumor suppressor miRNA and is downregulated in many malignancies, for example, human liver cancer [10,11]. Interestingly, miR-34a might be regulated by DNMT1 through promoter methylation in cancer cells or CSLCs [42].…”

“…It has been reported that DNMT1 is important in maintaining cancer stem cells (CSCs) in a self-renewal capability and promoting tumorigenesis, for example, mammary CSCs [8] and leukemia stem cells [9]. Importantly, Peng et al reported that DNMT1 repression could upregulate miR-34a to induce cytotoxicity and apoptosis in breast cancer cells [10]. Chamani et al showed that DNMT1 inhibition increases miR-34a expression, resulting in reduced viability of both Hep G2 and Huh7 cells [11].…”

Ginkgetin induces G2-phase arrest in HCT116 colon cancer cells through the modulation of b-Myb and miRNA34a expression

“…The epigenetic silencing of miR-34a by aberrant CpG methylation frequently occurs in various types of human cancer (39). Dihydroxyflavone has been reported to demethylate miR-34a and increases its expression in breast cancer cells (40). Therefore, we hypothesize that ginkgetin controls the expression of miR-34a through its epigenetic modulation; however, ginkgetin did not affect the demethylation of miR-34a (data not shown).…”

Adrenaline inhibits osteogenesis via repressing miR‐21 expression

“…Moreover, miR‐21 was suppressed during both early (1 week) and later (2 weeks) osteogenic differentiation (Figure B). To further analyze the possible mechanism of how adrenaline inhibits miR‐21, we focused on the histone modification of the miR‐21 promoter (Peng et al, ). As noted in Figure C, acetyl‐H3K9 antibody ChIP analysis revealed that osteogenic induction medium significantly induced the enrichment of acetylated H3K9 on the miR21 promoter, whereas adrenaline inhibited the enrichment.…”