Epigenetic Regulation of Oncogenic Signaling Pathways in Breast Cancer in Response to Dietary Polyphenols
The Wnt and Hedgehog signaling pathways play key roles in embryonic and stem cell developmental processes but can become overactive in human cancers and contribute to cancer cell invasion and metastasis. Crosstalk occurs between these two pathways in cancer due to the ability of Hedgehog signaling proteins to regulate activity of the Wnt pathway, and vice versa. This interdependent regulation allows for cancer therapies to mutually target the activity of both pathways. Interestingly, certain dietary polyphenolic compounds suppress the Hedgehog and Wnt signals in cancer. In our study, polyphenols were shown to modify epigenetic marks in genes positively regulating these pathways including GLI2, a transcriptional activator of Hedgehog signaling, and WNT4, a Wnt signaling ligand. Using the polyphenol resveratrol (RSV) from grapes, we examined the role of DNA methylation in regulation of Hedgehog and Wnt signaling in breast cancer. Non-invasive MCF-7 and invasive MCF10CA1a human breast cancer cell lines were used as experimental models. Following genome-wide DNA methylation analysis with Illumina 450K array, pyrosequencing and QPCR were performed to assess methylation and expression of GLI2 and WNT4. RSV led to increased methylation of enhancer regions of GLI2 and WNT4, which was accompanied by decreases in gene expression. Consistently, downregulation of Wnt and Hedgehog target genes was also observed following treatment in both cell lines. Further analysis using ChIP identified alterations in chromatin marks and transcription factor binding indicating a transcriptionally silent chromatin state in MCF10CA1a cells after 9 days RSV treatment. A Wnt Phospho-antibody Array was used to evaluate Wnt signals and the data demonstrated decreased activity from positive regulators of Wnt signaling with increases in activity from Wnt negative regulators. Based on these results, we proposed a model whereby RSV treatment targets cancer cells and reduces their cancerous features and metastatic potential by re-methylating and silencing genes and signaling pathways that are driving forces of breast cancer. We provided scientific evidence for natural dietary compounds as epigenetic modulating agents that could combat epigenetic activation of genes driving breast cancer development and progression, and hence could be effective in breast cancer prevention and/or treatment.
Stefanska, Purdue University.
Molecular biology|Health sciences|Nutrition
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