Sulforaphane Bioavailability and Chemopreventive Activity in Men Presenting for Biopsy of the Prostate Gland: A Randomized Controlled Trial

Abstract

Previous studies suggest compounds such as sulforaphane (SFN) derived from cruciferous vegetables may prevent prostate cancer development and progression. This study evaluated the effect of broccoli sprout extract (BSE) supplementation on blood histone deacetylase (HDAC) activity, prostate RNA gene expression, and tissue biomarkers (histone H3 lysine 18 acetylation (H3K18ac), HDAC3, HDAC6, Ki67, and p21). A total of 98 men scheduled for prostate biopsy were allocated into either BSE (200 µmol daily) or a placebo in our double-blind, randomized controlled trial. We used nonparametric tests to evaluate the differences of blood HDAC activity and prostate tissue immunohistochemistry biomarkers between treatment groups. Further, we performed RNA-Seq analysis on the prostate biopsies and identified 40 differentially expressed genes correlated with BSE treatment, including downregulation of two genes previously implicated in prostate cancer development, AMACR and ARLNC1. Although urine and plasma SFN isothiocyanates and individual SFN metabolites were statistically higher in the treatment group, our results did not show a significant difference in HDAC activity or prostate tissue biomarkers. This study indicates BSE supplementation correlates with changes in gene expression but not with several other prostate cancer biomarkers. More research is required to fully understand the chemopreventive effects of BSE supplementation on prostate cancer.

Trial registration: ClinicalTrials.gov NCT01265953.

Figures

Figure 1.

Randomized controlled trial sample size flowchart.

Figure 2.. Expression patterns of significantly differentially expressed genes.

The heatmap shows the 40 significantly differentially expressed genes with respect to the BSE treatment on samples that came from subjects with evidence of prostate cancer. Columns represent expression of each sample, with sample labels at the bottom of the heatmap. Rows represent each differentially expressed gene, with the HUGO Gene Nomenclature Committee (HGNC) gene names listed along the right of the heatmap. Individual cells are colored relative to the row means of log2-fold changes. Each sample is annotated with level of cancer severity in the subject, treatment, and phenotype along the top of the heatmap. Dendrograms along the top and left side of the heatmap represent hierarchical clusters determined based on Euclidean distance calculations of sample-wide and gene-wide expression dissimilarities, respectively. The green box shows the cluster of six genes we identified, with two, AMACR and ARLNC1, having expression confirmed using qPCR (Figure 3).

Figure 3.. Effects of BSE supplements on ARLNC1 and AMACR expression.

ARLNC1 and AMACR mRNA levels were detected in available prostate biopsy samples using RNA sequencing. Biopsies were designated no cancer if they were from subjects with benign tissue cores, while cancer positive samples came from subjects who had a severity score of 2–3. Subjects were given either a placebo or a BSE supplement. Bars indicate the mean expression level of the indicated gene with SEM. Statistics were calculated with DESeq2 software package (n = 7–18). TPM, transcripts per million.