Evaluation of epigenetic effect of Silymarin in various cell lines

Epigenetic changes are effective in cancer development. Waddington described epigenetics in the 1940s as a change in gene expression without altering the base sequence of DNA. DNA methylation, histone modifications, chromatin remodeling and micro-RNA are recognized as the basic epigenetic mechanisms. Epigenetic changes play an important role in tumor formation and progression since it affects pathways related to tumor development in cancer cells. Epigenetically effective drugs are used in the control of gene expression related to cell cycle control, apoptosis, cell signaling, invasion, metastasis and angiogenesis. Reversibility of epigenetic irregularities allows the use of DNA methylation and histone acetylation inhibitors in the treatment of cancer, and has been shown to be an effective strategy in cancer treatment by targeting epigenetic differences such as DNA modification and histone modification. Drug candidate compounds capable of altering DNA methylation and histone modification profile have begun to develop and have been switched to preclinical and clinical stages. 5-azacitidine and SAHA inhibitor groups are administered alone or in combination with cytotoxic agents such as chemotherapy, radiotherapy approved by the Food and Drug Administration (FDA). 5-azacytidine is structurally similar to the cytosine nucleotide and provides for inhibition of DNA methyltransferases. Another therapeutic agent developed using epigenetic mechanisms is the histone deacetylase (HDAC) inhibitor SAHA. Silymarin is obtained from the seeds of Silybum marianum L., also called milk thistle of Asteraceae family.The most important active ingredient is silymarin is a polyphenol chemically and a flavonolignant as plant chemistry. Antioxidant, antimetastatic, antiangiogenic and antiinflammatory effects of silymarin have been shown in the studies. Silymarin is the most frequently used agent for complementary and alternative therapy among chemotherapy patients due to its anticarcinogenic effects. The aim of this study was to evaluate the effect of silymarin on epigenetic regulation in various cancer cell lines. Human neuroblastoma cell line SHSY5Y cells, human hepatocellular cell line HepG2 cells and human breast cancer cell line MCF-7 cells were grown in a 37°C incubator containing 5%CO2 and 95% humidity. Genotoxic doses of silymarin, 5-azacytidine and SAHA were determined by MTT test. Cells were treated for 48 hours according to the determined IC50 doses. DNMT and HDAC enzyme activities were measured. p53, cMyc and NFκB protein levels were determined by Western Blot. There are a limited number of studies on the effect of silymarin on epigenetic pathways. In this study, the effects of silymarin on epigenetic enzymes and protein levels in various cancer cell lines when used alone and in combination with epigenetic inhibitors were evaluated. According to our results, silymarin showed an inhibitory effect on DNMT. There was no inhibition effect on HDAC. Silymarin inhibited p53 K373, p53 K382, cMyc and NFκB protein levels, while p53 increased S46 protein level.