The Effect of Histone Hyperacetylation on Viability of Basal-Like Breast Cancer Cells MDA-MB-231

Background: The Basal-Like breast cancer, is always known for lack of expression of estrogen receptor (ER), progesterone receptor (PR) and as well, absence of epidermal growth factor receptor 2 (HER2) gene amplification. Improper expression pattern of ER, PR, and Her2, makes Basal-Like breast tumors resistant to the current hormonal and anti HER2 treatments. In recent decades, several studies have been conducted to investigate the regulatory role of chemical modifications of core histones in gene expression. Their results have shown that histone acetylation is involved in regulation of cell survival. Acetylation of core histones is regulated by the epigenetic-modifying enzymes named Histone Deacetylases (HDACs). As a new approach to control the viability of breast tumor cells resistant to the hormonal and anti-HER2 treatments, we have targeted the HDACs. Using Trichostatin A (TSA) as a known HDACs inhibitor, we have tried to hyperacetylate the core histones of MDA-MB-231 cells as an in vitro model of Basal-Like breast tumors. Then we have investigated the effect of histone hyperacetylation on viability of MDA-MB-231 cells. Methods: MDA-MB-231 cells were cultured in RPMI 1640 medium containing 10% fetal bovine serum (FBS) and were incubated at 37°C, in a humidified incubator with 5% CO2 atmosphere. Then cells were treated with different concentrations of TSA including: 50, 100, 200, 400, 800 and 1000 nM or control (1% DMSO). After 24 and 48 hours, viability of cells was evaluated by MTT assay. Results: After 24 and 48h exposure to different concentrations of TSA, MDA-MB-231 cells showed a maximum tolerable dose. At higher concentrations, TSA decreased the percentage of cell viability through a time-dose dependent manner. IC50 value for 48h treatment was 600 nM. Conclusions: Our results indicate that HDACs inhibition and subsequently hyperacetylation of histones, leads to cytotoxic effects on breast tumor cells resistant to the current treatments. Following this pilot research we are trying to suggest molecular mechanisms underlying the anti-proliferative effects triggered by HDACs inhibition.