Epidemiological data indicate that dietary consumption of cruciferous vegetables may reduce the risk of many cancers including breast cancer. Cruciferous vegetables contain high levels of glucosinolates; stable phytochemicals that when metabolized produce cancer-preventing active isothiocyanates. Isothiocyanates, such as sulforaphane (SFN) found in broccoli sprouts, are thought to prevent tumorigenesis through epigenetic mechanisms controlling the expression of tumor-related genes. Ingestion of broccoli sprouts results in rapid distribution of SFN to breast epithelium, however, the effect of chronic exposure to low levels of SFN on the growth of breast cells has not been fully explored.

In the present study we assessed the effect of SFN on the growth of an immortalized breast cell line (MCF10A), and two breast cancer cell lines; the estrogen receptor positive MCF-7 cell line, and the estrogen receptor negative TMX2-28 cell line. We first determined the seeding densities for each cell line that resulted in 80% confluence after three days of growth in T-25 flasks: MCF10A (1 x 106), MCF-7 (8 x 105), and TMX2-28 (5 x 105) per 5 mL. Next, cells from each line were plated at the predetermined seeding densities in T-25 flasks and treated with either SFN (5 μM) or vehicle (0.02% DMSO) for up to 40 days. Every third day, cell cultures were photographed, after which the cells were resuspended in culture medium, counted using a hemocytometer, and the predetermined numbers of cells (seeding numbers) were returned to T-25 flasks and treated with SFN or vehicle. Cells not needed for seeding the flasks were archived for future analysis of gene expression and DNA methylation.

Treatment with SFN decreased cell growth. After 22 days of treatment with SFN, mean proliferation of both the MCF10A and MCF-7 cell cultures was inhibited by 62% (t = 2.8; p = 0.02) and 72% (t = 2.6; p = 0.02), respectively. In contrast, the decrease in proliferation of TMX2-28 cells treated with SFN was not statistically significant (t = 1.2; p = 0.255) from the vehicle control at 22 days. However, by day 40, TMX2-28 cell cultures treated with SFN showed a significant decrease in mean proliferation 36% (t = 2.2; p = 0.04). Ongoing studies are examining the epigenetic mechanisms by which SFN decreased cell proliferation.

Citation Format: Ashley L. Silvia, Eva P. Browne, Kathleen F. Arcaro. Chronic, low-dose treatment with sulforaphane inhibits growth of breast cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5366. doi:10.1158/1538-7445.AM2013-5366