Histone deacetylase activity and vitamin D-dependent gene expressions in relation to sulforaphane in human breast cancer cells.

Abstract

This study employed a combinatorial chemopreventive strategy to investigate the impact of dietary histone deacetylase (HDAC) inhibitor, that is, sulforaphane on chromatin remodeling in BC. To understand the epigenetics-mediated changes in gene expression, MCF-7 cells were exposed for 24hr to 1,25(OH)2D3 (100nM) either alone or in combination with L-sulforaphane and TSA (20μM and 1μM, respectively) at 70% confluency. Changes in VDR, CYP24A1, CYP27B1, and TRPV6 gene expressions were quantified using real-time PCR-based assays. HDAC inhibitor activity was assessed using HDAC I/II assay that measured global changes in acetylation status. Cell viability was measured using ATP and MT assays. Clonogenic and migration assays were performed to analyze the ability of single cells to grow into colonies and % closure (migration ability) upon treatments, respectively. Results were expressed as ΔCT±standard error of means (SEM) from One-way ANOVA analyses for mRNA expressions and mean±SEM for all other assays. In MCF-7 cells, treatment with 1,25(OH)2D3 tended to decrease VDR (13±0.4) and CYP27B1 (12±0.96), while significantly increased TRPV6 (p=.02, 14±0.1) and CYP24A1 (p<.0001, 0.38±0.12) expression. D alone and D+TSA group had the opposite effects on HDAC inhibition from SFN alone, D+SFN, and TSA alone. The clonogenic assay showed a significant decrease in colony formation with no colonies for D+TSA (p<.03) and TSA alone groups (p<.03). Cell viability tended to decrease with D alone and in combination with TSA. These data suggest that the effects of 1,25(OH)2D3 and sulforaphane are selective and gene-specific in MCF-7 cells. Breast cancer (BC) affects a large number of the U.S. population each year. Like most cancers, nutrition does play a role in the prevention of BC. However, dietary advice that includes reducing alcohol intake, red meat, and saturated fat consumption, while increasing the intake of heart-healthy fats, dietary fiber, and lean protein, etc., is difficult to apply to all cancers from a preventative standpoint. Vitamin D has been implicated in BC, mostly as a protective factor, with mixed findings. This research focuses on the role of vitamin D as a protective intervention in human BC, along with a dietary bioactive compound-sulforaphane. The idea is to combine the known benefits of a micronutrient with potential benefits of the bioactive compound to establish a stronger intervention against BC progression, irrespective of the subtype.