Apoptosis inducing effect of DIM is mediated by inhibition of nuclear translocation of NF-KappaB in breast cancer cells.

Abstract

3144

Dietary indole-3-cabinol (I3C), a natural compound present in vegetables of the Genus Brassica family show clinical benefits and causes apoptosis in breast cancer cells. Our laboratory and others have shown that I3C induces apoptosis in breast cancer cells, and the induction of apoptosis is believed to be mediated by inactivation of Akt and NF-KappaB pathways. 3-3Acute Diindolylmethane (DIM), a major in vivo acid-catalyzed condensation product of I3C is also suggested to have some benefit for the treatment of breast cancer. However, the precise molecular mechanism(s) by which DIM induces apoptosis in breast cancer cells has not been fully elucidated. Hence, we investigated whether DIM-induced apoptosis of breast cancer cells could also be mediated by inactivation of Akt and NF-KappaB. We found that DIM induces apoptotic processes in MCF10A derived malignant (MCF10CA1a) cell line but not in non-tumorigenic parental MCF10A cells. Immunoprecipitation, kinase assays, and Western blot analysis showed that DIM specifically inhibits Akt kinase activity and abrogates the EGF-induced activation of Akt in breast cancer cells, similar to those observed for I3C. We also found that DIM reduces phosphorylation of IKappaB, an inhibitor of NF-KappaB. Our confocal study clearly shows that DIM blocks the translocation of p65, a subunit of NF-KappaB to the nucleus. DNA binding analysis and transfection studies with IKK cDNA revealed that over-expression of IKK mediates IKappaB phosphorylation, which activates NF-KappaB, and this activation was completely abrogated by DIM treatment. Taken together, these results extend our previous findings with I3C and suggest that the inactivation of Akt and NF-KappaB activity also plays important roles in DIM-induced apoptosis in breast cancer cells. These results are more relevant to vivo situations. Our results also suggest that DIM could be a promising chemopreventive and /or therapeutic agent by selective induction of apoptosis in malignant breast epithelial cells.