Association Between Histone Deacetylase Activity and Vitamin D-Dependent Gene Expressions in Relation to Sulforaphane in Human Colorectal Cancer Cell

Background: It is relatively unknown how dietary bioactive compound sulforaphane (SFN), and vitamin D regulate gene expression in colorectal cancer. We hypothesized that combination of SFN with vitamin D would prove beneficial in colorectal cancer. A combinatorial chemo preventive strategy was employed to investigate the impact of sulforaphane on chromatin remodeling in colorectal carcinoma. To understand the epigenetics-mediated changes in gene expression in response to sulforaphane and vitamin D, Caco-2 cells were exposed for 24 hours to vitamin D (100nM) either alone or in combination with L-sulforaphane and TSA (20μM and 1μM respectively) at 70% confluency (proliferating) and after 13 days post confluency (fully differentiated). Changes to VDR, CYP24A1, CYP27B1 and TRPV6 gene expressions were quantified using real-time PCR-based assays. Histone deacetylase inhibitor activity was assessed using HDAC I/II assay that measured global changes in acetylation status.

Results: In differentiated Caco-2 cells, none of the genes had significant changes from D alone group. D+SFN (p=0.99) demonstrated an opposing effect from D alone and decreased VDR expression. However, in proliferating Caco-2 cells, D+SFN (p<0.04) increased VDR expression and decreased CYP27B1 (p<0.01) more than D alone (p=0.38 and p=0.07 respectively). Although statistically significant, D+SFN (p=0.01) effects on HDAC inhibitor activity was lower than TSA alone (p<0.0004) or SFN alone group (p<0.0014).

Conclusion: These data suggest that colon cancer cells respond to dietary components differently under different conditions. The effect of vitamin D and sulforaphane is selective and gene-specific in the complex multistep process of colorectal carcinogenesis in vitro. This article is protected by copyright. All rights reserved.

Keywords: HAT, histone acetyltransferase; HDAC, histone deacetylase; SFN, sulforaphane; TSA, Trichostatin A; Vitamin D3.