The phytochemical indole-3-carbinol (I3C), found in cruciferous vegetables, and its major acid-catalyzed reaction product 3,3V-diindolylmethane (DIM) showed anticancer activity mediated by its pleiotropic effects on cell cycle progression, apoptosis, carcinogen bioactivation, and DNA repair. To further elucidate the molecular mechanism(s) by which 3,3V-diindolylmethane exerts its effects on breast cancer cells, we have used microarray gene expression profiling analysis. We found a total of 1,238 genes altered in 3,3V-diindolylmethane-treated cells, among which 550 genes were downregulated and 688 genes were up-regulated. Clustering analysis showed significant alterations in some genes that are critically involved in the regulation of cell growth, cell cycle, apoptosis, and signal transduction, including downregulation of survivin. Previous studies have shown that antiapoptotic protein survivin is overexpressed in many human cancers, including breast cancer. However, very little or no information is available regarding the consequence of down-regulation of survivin for cancer therapy. We, therefore, hypothesized that down-regulation of survivin as observed by 3,3V-diindolylmethane could be an important approach for the treatment of breast cancer. We have tested our hypothesis using multiple molecular approaches and found that 3,3V-diindolylmethane inhibited cell growth and induced apoptosis in MDA-MB-231 breast cancer cells by downregulating survivin, Bcl-2, and cdc25A expression and also caused up-regulation of p21 WAF1 expression, which could be responsible for cell cycle arrest. Down-regulation of survivin by small interfering RNA before 3,3V-diindolylmethane treatment resulted in enhanced cell growth inhibition and apoptosis, whereas overexpression of survivin by cDNA transfection abrogated 3,3V-diindolylmethane-induced cell growth inhibition and apoptosis. These results suggest that targeting survivin by 3,3V-diindolylmethane could be a new and novel approach for the prevention and/or treatment of breast cancer. (Cancer Res 2006; 66(9): 4952-60)

Pancreatic cancer (PC) is the fourth most common cause of cancer-related deaths in the United States, suggesting that designing novel therapeutic strategy is required to improve the survival outcome of patients diagnosed with PC. Recently, microRNAs (miRNA) have been found to be involved in the regulation of multiple aspects of tumor development and progression including PC. In this study, we investigate whether miR-34a plays a critical role in the control of cell growth and apoptosis in PC cells. We found that Re-expression (forced expression) of miR-34a inhibits cell growth and induces apoptosis, with concomitant down-regulation of Notch-1 signaling pathway, one of the target of miR-34a. Moreover, treatment of PC cells with a natural compound genistein led to the up-regulation of miR-34a, resulting in the down-regulation of Notch-1, which was correlated with inhibition of cell growth, and induction of apoptosis. Our findings suggest that genistein could function as a non-toxic activator of a miRNA that can suppress the proliferation of PC cells.

Indole compounds, obtained from cruciferous vegetables, have been investigated for their putative anti-cancer properties. Studies with indole-3-carbinol (I3C) and its dimeric product, 3, 3' diindolylmethane (DIM), have indicated efficacy of these compounds against a number of human cancers. Available as well as emerging data suggests that these compounds act on a number of cellular signaling pathways leading to their observed biological effects. Such pleiotropic effects of these compounds are also considered crucial for their chemosensitization activity wherein they help reduce the toxicity and resistance against conventional chemotherapeutic drugs. These observations have major clinical implications especially in chemotherapy. Through this review, we have attempted to update current understanding on the state of anti-cancer research involving indole compounds. We have also summarized the available literature on modulatory effects of indoles on molecular targets such as survivin, uPA/uPAR and signaling pathways such as the NF-kappaB pathway, which are important for the apoptosis-inducing and chemosensitizing properties of these compounds.

Recent results from epidemiology, in vitro cell culture and in vivo (animal and human) studies have suggested the benefits of indole-3-carbinol (I3C) for the prevention of many types of cancer, including breast cancer. However, there are no reports, to the best of our knowledge, on the effect of I3C on isogenic nontumorigenic and tumorigenic breast epithelial cells, and there is a significant void in our understanding of the molecular mechanism(s) by which I3C induces apoptotic cell death in breast cancer cells. To fill this gap in our understanding, we conducted experiments to investigate the effects of I3C on an isogenic nontumorigenic (MCF10A) and tumorigenic (MCF10CA1a [CA1a]) breast epithelial cells. Here we show that CA1a cells are more sensitive to low concentration of I3C in terms of cell growth inhibition compared to MCF10A cells. We further report that I3C upregulates Bax/Bcl-2 ratio and downregulates Bcl-xL expression in CA1a cells but not in MCF10A cells. We also report, for the first time, that I3C induces Bax translocation to the mitochondria, causing mitochondrial depolarization, resulting in the loss of mitochondrial potential leading to the release of cytochrome c and subsequent cell death in CA1a cells but not in MCF10A cells. From these results, we conclude that I3C selectively induces apoptosis in breast cancer cells, but not in nontumorigenic breast epithelial cells, suggesting the potential therapeutic benefit of I3C against breast cancer.