Genome-wide transcriptome analysis of the dietary chemopreventive phytochemical sulforaphane on normal and prostate cancer cells.
Epidemiological studies provide strong evidence that consumption of cruciferous vegetables, such as broccoli, can significantly reduce the risk of developing cancers. Sulforaphane (SFN), a phytochemical derived from cruciferous vegetables, induces anti-proliferative and pro-apoptotic responses in prostate cancer cells, but not in normal prostate cells. The mechanisms responsible for these specific chemopreventive properties remain unclear. We utilized RNA sequencing to test the hypothesis that SFN modifies the expression of genes that are critical in prostate cancer progression. Normal prostate epithelial cells, and androgen-dependent and androgen-independent prostate cancer cells were treated with 15 µM SFN and the transcriptome was determined at 6 and 24 hour time points. SFN altered the expression of ~3,000 genes in each cell line and the response was highly dynamic over time. SFN influenced the expression of genes in functional groups and pathways that are critical in cancer including cell cycle, apoptosis and angiogenesis, but the specific effects of SFN differed depending on the state of cancer progression. Network analysis suggested that a transcription factor that is overexpressed in many cancers, Specificity protein 1 (Sp1), is a major mediator of SFN-induced changes in gene expression. Nuclear Sp1 protein was significantly decreased by 24 hour SFN treatment in prostate cancer cells, while a related transcription factor, Sp3 protein was only modestly decreased in androgen-independent prostate cancer cells.  Overall, the data show that SFN significantly affects gene expression in normal and cancer cells, with key targets in chemopreventive processes, making it a promising dietary anti-cancer agent. Overall design: Examination of how the transcriptome of normal and prostate cancer cells is altered by treatment with sulforaphane