title: 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.
authors.affiliation: Research Center for Nutrition and Food Safety, Third Military Medical University; Chongqing Key Laboratory of Nutrition and Food Safety, Chongqing, China. Department of Public Health, School of Preclinical Medicine, Chengdu Medical College, Chengdu, China.
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Peng
authors.affiliation: Research Center for Nutrition and Food Safety, Third Military Medical University; Chongqing Key Laboratory of Nutrition and Food Safety, Chongqing, China. henry8010@126.com mimt2007@126.com.
authors.forename: Hui
authors.initials: H
authors.lastname: Chang
authors.affiliation: Research Center for Nutrition and Food Safety, Third Military Medical University; Chongqing Key Laboratory of Nutrition and Food Safety, Chongqing, China.
authors.forename: Yeyun
authors.initials: Y
authors.lastname: Gu
authors.affiliation: Research Center for Nutrition and Food Safety, Third Military Medical University; Chongqing Key Laboratory of Nutrition and Food Safety, Chongqing, China.
authors.forename: Junli
authors.initials: J
authors.lastname: Chen
authors.affiliation: Research Center for Nutrition and Food Safety, Third Military Medical University; Chongqing Key Laboratory of Nutrition and Food Safety, Chongqing, China.
authors.forename: Long
authors.initials: L
authors.lastname: Yi
authors.affiliation: Research Center for Nutrition and Food Safety, Third Military Medical University; Chongqing Key Laboratory of Nutrition and Food Safety, Chongqing, China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Xie
authors.affiliation: Research Center for Nutrition and Food Safety, Third Military Medical University; Chongqing Key Laboratory of Nutrition and Food Safety, Chongqing, China.
authors.forename: Jundong
authors.initials: J
authors.lastname: Zhu
authors.affiliation: Research Center for Nutrition and Food Safety, Third Military Medical University; Chongqing Key Laboratory of Nutrition and Food Safety, Chongqing, China.
authors.forename: Qianyong
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: Research Center for Nutrition and Food Safety, Third Military Medical University; Chongqing Key Laboratory of Nutrition and Food Safety, Chongqing, China. henry8010@126.com mimt2007@126.com.
authors.forename: Mantian
authors.initials: M
authors.lastname: Mi
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D049109:Cell Proliferation / Q000187:drug effects; D002471:Cell Transformation, Neoplastic / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000037:antagonists & inhibitors; D019175:DNA Methylation; D057890:Epigenomics; D005260:Female; D005419:Flavonoids / Q000494:pharmacology*; D005455:Fluorescent Antibody Technique; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D007124:Immunoenzyme Techniques; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D035683:MicroRNAs / Q000235:genetics*; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D014407:Tumor Cells, Cultured; D023041:Xenograft Model Antitumor Assays
chemical_list: C555160:3,6-dihydroxyflavone; D005419:Flavonoids; C524940:MIRN21 microRNA, human; C522425:MIRN34 microRNA, human; D035683:MicroRNAs; D012333:RNA, Messenger; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; C000619380:DNMT1 protein, human; C000619381:Dnmt1 protein, mouse; C000619382:Dnmt1 protein, rat; C546842:MTOR protein, human; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases