3,3'-Diindolylmethane Inhibits TNF-α- and TGF-β-Induced Epithelial-Mesenchymal Transition in Breast Cancer Cells.

Epithelial-mesenchymal transition (EMT) is the initial event required by cancer cells. Thus, inhibition of the EMT process could have potential benefits for preventing the spread of cancers. The phytochemicals have been reported to have inhibitory activity against the EMT process in breast cancers, but the mechanism behind this effect has not been fully elucidated. 3,3'-Diindolylmethane (DIM) is a major indole derived from bioactive compounds in cruciferous vegetables. In this study, we examined the effects of DIM cotreatment together with TNF-α/TGF-β on the EMT process as well as the mechanisms underlying its effects on human breast cancer cells. DIM significantly enhanced the mRNA and protein expression of E-cadherin and occludin in MCF-7 cells. The protein expression levels of E-cadherin and occludin in MCF-7 cells were significantly decreased after TNF-α/TGF-β treatment alone, but these effects were reversed by the DIM co-treatment. Furthermore, DIM with TNF-α/TGF-β co-treatment attenuated the phosphorylation of Smad2/3 and ERK1/2 proteins. DIM significantly inhibited the TNF-α/TGF-β-induced migration of breast cancer cells. Taken together, the results indicated that DIM effectively suppressed EMT processes through the inhibition of TNF-α/TGF-β-associated signaling pathways in breast cancer cells. Thus, DIM may be a novel preventive and/or therapeutic approach for the treatment of breast cancers.