The histone deacetylase inhibitor trichostatin A alters microRNA expression profiles in apoptosis-resistant breast cancer cells

Abstract

The development of drug resistance represents a major complication in the effective treatment of breast cancer. Epigenetic therapy, through the use of histone deacetylase inhibitors (HDACi) or demethylation agents, is an emerging area of therapeutic targeting in a number of ontological entities, particularly in the setting of aggressive therapy-resistant disease. Using the well-described HDAC inhibitor trichostatin A (TSA) we demonstrate the suppression of in vitro clonogenicity in the previously described apoptosis-resistant MCF-7TN-R breast carcinoma cell line. Additionally, recent work has demonstrated that these agents can alter the expression profile of microRNA signatures in malignant cells. Using an unbiased microRNA microarray analysis, changes in miRNA expression of MCF-7TN-R cells treated with TSA for 24 h were analyzed. We observed significant up-regulation of 22 miRNAs and down-regulation of 10 miRNAs in response to TSA treatment. Our results demonstrate that the HDACi, TSA, exerts anticancer activity in the apoptosis-resistant MCF-7TN-R breast carcinoma cell line. This activity is correlated with TSA alteration of microRNA expression profiles indicative of a less aggressive phenotype.

Figure 1

TSA suppression of MCF-7TN-R cell clonogenic survival. MCF-7TN-R cells were plated (2,000 cells/well) in 10% DMEM in 6-well plates and allowed to adhere overnight. Twenty-four hours later the cells were treated with vehicle (DMSO) or TSA (0.1, 1, 10 μM) for 10 days. Colonies of ≥50 cells were counted as positive. Bars represent mean percentage clonogenic survival normalized to DMSO control cells ± SEM. (^**p<0.01).

Figure 2

TSA regulation of microRNA expression in MCF-7TN-R. Heatmap of microRNA changes induced by treatment with TSA (10 μM) after 24 h in MCF-7TN-R cells. microRNAs demonstrating statistically significant changes in expression are shown (p<0.01). Green indicates down-regulated expression and red indicates up-regulated expression of microRNAs. Individual samples are represented in columns while specific microRNAs are represented by rows as labeled.