The Effects of Combinatorial Genistein and Sulforaphane in Breast Tumor Inhibition: Role in Epigenetic Regulation.

Dietary compounds that possess the properties of altering epigenetic processes are gaining popularity as targets for cancer prevention studies. These compounds when administered at optimal concentrations and especially in combination can have enhanced effects in cancer prevention or therapy. It is important to study the interaction of two or more compounds in order to assess their role in enhancing prevention. Genistein (GEN), found in soy, has been extensively studied for its role as an epigenetic modifier especially as a DNA methyltransferase (DNMT) inhibitor and sulforaphane (SFN), found in cruciferous vegetables, is known as a histone deacetylase (HDAC) inhibitor. However, very little is known about the effects of these two compounds in conjunction in breast cancer prevention or therapy. In our current study, we determined that, at certain doses, the compounds have synergistic effects in decreasing cellular viability of breast cancer cell lines. Our results indicate that the combination of GEN and SFN is much more effective than their single doses in increasing the rate of apoptosis and lowering the colony forming potential of these cells. We determined that these compounds inhibit cell cycle progression to G2 phase in MDA-MB-231 and G1 phase in MCF-7 breast cancer cell lines. Additionally, we determined that the combination is effective as an HDAC and histone methyltransferase (HMT) inhibitor. Furthermore, we demonstrated that this combination downregulates the levels of HDAC2 and HDAC3 both at the mRNA and protein levels. We also found that these compounds have the potential to downregulate KLF4 levels, which plays an important role in stem cell formation. The combination of GEN and SFN is also effective in downregulating hTERT levels, which is known to be activated when KLF4 binds to its promoter region. Our hypothesis is further strengthened by