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Stilbenoids remodel the DNA methylation patterns in breast cancer cells and inhibit oncogenic NOTCH signaling through epigenetic regulation of MAML2 transcriptional activity

ABSTRACT: Genome wide DNA methylation profiling of human breast cancer cell lines, lowly invasive MCF10CA1h and highly invasive MCF10CA1a, treated with vehicle control (ethanol) and with RSV (resveratrol). The Illumina Infinium 450K Human DNA methylation Beadchip v1.2 was used to obtain DNA methylation profiles across approximately 450,000 CpGs in human cell lines exposed to described treatments. Samples included biological triplicate of MCF10CA1h control (ethanol treated), biological triplicate of MCF10CA1h treated with RSV, biological triplicate of MCF10CA1a control (ethanol treated), biological triplicate of MCF10CA1a treated with RSV.

ORGANISM(S): Homo sapiens

PROVIDER: GSE80794 | GEO | 2016/08/10

SECONDARY ACCESSION(S): PRJNA319991

REPOSITORIES: GEO

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Project description:Transcription factor (TF)-mediated regulation of genes is often disrupted during carcinogenesis. The DNA methylation state of TF-binding sites may dictate transcriptional activity of corresponding genes. Stilbenoid polyphenols, such as pterostilbene (PTS), have been shown to exert anti-cancer action by remodeling DNA methylation and gene expression patterns of tumor suppressor genes and oncogenes. However, the mechanisms behind these effects still remain unclear. Here, the dynamics between oncogenic TF, OCT1, binding and de novo DNA methyltransferase, DNMT3B, binding in PTS-treated MCF10CA1a invasive breast cancer cells has been explored. Using chromatin immunoprecipitation (ChIP) followed by next generation sequencing, we determined 47 gene regulatory regions with decreased OCT1 binding and enriched DNMT3B binding in response to PTS. Most of those genes were found to have oncogenic and pro-metastatic functions. PRKCA, a gene encoding for protein kinase C alpha (PKC-alpha), was selected for further mechanistic investigation due to its functional and regulatory connection with numerous oncogenic pathways and cancer-driving processes. Two additional genes, troponin T2 (TNNT2) and DXZ4 associated non-coding transcript 2 (DANT2), were also investigated as they demonstrated some of the highest increase in DNMT3B occupancy and novel oncogenic functions. PTS led to the recruitment of DNMT3B to the PRKCA promoter region and TNNT2 and DANT2 enhancers at loci that are occupied by OCT1 in vehicle-treated cells. Substantial decrease in OCT1 occupancy with increased DNMT3B binding were accompanied by PRKCA promoter and TNNT2 and DANT2 enhancer hypermethylation, and gene silencing. Interestingly, hypermethylation of the regulatory regions of the genes in response to PTS was not detected in DNMT3B-CRISPR knockout MCF10CA1a breast cancer cells, which indicates DNMT3B-dependent methylation of PRKCA, TNNT2, and DANT2 upon PTS treatment. Our findings provide a better understanding of mechanistic players and their gene targets that possibly contribute to the anti-cancer action of stilbenoid polyphenols.

Project description:Basal-like and triple negative breast cancer (TNBC) share common molecular features, poor prognosis and a propensity for metastasis to the brain. Amplification of EGFR occurs in ~50% of basal-like breast cancer and mutations in the epidermal growth factor receptor (EGFR) have been reported in up to ~ 10% of Asian TNBC patients. In non-small cell lung cancer several different mutations in the EGFR tyrosine kinase domain confer sensitivity to receptor tyrosine kinase inhibitors, but the tumourigenic potential of EGFR mutations in breast cells and their potential for targeted therapy is unknown. Constructs containing wild type, G719S or E746-A750 deletion mutant forms of EGFR were transfected into the ‘near normal’ MCF10A breast cells and their tumorigenic derivative, MCF10CA1a. These transfected lines were used to investigate the effects of EGFR over-expression and mutation on proliferation, migration, invasion, response to gefitinib, and tumour formation in vivo. We also carried out copy number analysis and whole exome sequencing of the MCF10A and MCF10CA1a cell lines. Both activating mutations of EGFR increased the proliferative ability of MCF10A and MCF10CA1a cell lines, and increased the anchorage-independent growth and sensitivity to gefitinib in MCF10A cells. In addition, the EGFR-E746-A750 deletion increased the migratory and invasive abilities of the MCF10CA1a cell line in vitro, and greatly increased the formation and growth of MCF10CA1a tumours in vivo. Compared to MCF10A cells, MCF10CA1a cells had large regions of gain on chromosome 9 and the long arm of chromosome 3, deletion in the short arm of chromosome 7, and mutations in many genes implicated in cancer. The EGFR E746-A750 deletion mutation, and to a lesser extent G719S, greatly enhance the oncogenic properties of MCF10A cell line, and increase sensitivity to gefitinib. Although the addition of EGFR E746-A750 renders the MCF10CA1a cells more tumourigenic in vivo it is not accompanied by increased sensitivity to gefitinib, perhaps because of additional mutations, including the PIK3CA H1047R mutation, that the MCF10CA1a cell line has acquired. Screening TNBC/basal-like breast cancer for EGFR mutations may prove useful for directing therapy but, as in non-small cell lung cancer cancer, accompanying mutations in PIK3CA may confer gefitinib resistance.

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Stilbenoids remodel the DNA methylation patterns in breast cancer cells and inhibit oncogenic NOTCH signaling through epigenetic regulation of MAML2 transcriptional activity

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