Mechanisms of growth inhibition induced by methylene-substituted and ring-substituted dims in breast cancer cells
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One in 8 women will be diagnosed with breast cancer in the United States and estrogen receptor (ER) status largely influences the type and subsequent success of treatment employed. Although ER-positive breast cancer can be treated with endocrine therapy, the more invasive ER-negative breast cancer is non-responsive to this therapy and cytotoxic agents are often utilized which are associated with many adverse side effects. Consequently, there is a genuine need to develop more effective, less toxic treatments for invasive breast cancer. Indole-3-carbinol is a phytochemical found in cruciferous vegetables and one of its major metabolites, 3,3’-diindolylmethane (DIM), exhibits a broad range of anticancer and antitumorigenic activities. ER-negative MDA-MB-231 and MDA-MB-453 breast cancer cell growth was inhibited after treatment with a novel series of methylenesubstituted DIMs (C-DIMs), namely 1,1-bis(3’-indolyl)-1-(p-substitutedphenyl) methanes containing trifluoromethyl (DIM-C-pPhCF3), t-butyl (DIM-C-pPhtBu) and phenyl (DIM-C-pPhC6H5) groups. In addition, DIM-C-pPhC6H5 (40 mg/kg/d) inhibited tumor growth in nude mice bearing MDA-MB-231 cells as xenografts. Treatment of breast cancer cells with C-DIMs lead to downregulation of cyclin D1 and induction of non-steroidal anti-inflammatory drug-activated gene 1. Detection of necrosis, caspasedependent or caspase-independent apoptosis were not observed in breast cancer cells treated with C-DIMs, however autophagic cell death was induced by C-DIMs. DIM and ring-substituted DIMs have exhibited antitumorigenic activity in tumor murine mammary models. An investigation into the mechanism of cell death induced by DIM and 5,5’-dibromoDIM (5,5’-diBrDIM) in both ER-positive (MCF-7) and ERnegative (MDA-MB-231) breast cancer cells revealed modulation of several key signaling pathways involved in growth control. Both DIM and 5,5’-diBrDIM downregulated cyclin D1, although only 5,5’-diBrDIM induced a depolarization of the mitochondrial membrane. In addition, apoptosis was observed in MCF-7 cells treated with 5,5’-diBrDIM but not MDA-MB-231 cells. In summary, C-DIMs may represent new mechanism-based agents for treatment of breast cancer through induction of autophagic cell death. The ring-substituted DIMs correspond to a novel class of uncharged mitochondrial poisons that are also highly effective in inhibiting breast cancer cell growth. Results of this research provide evidence for the potential role of two new series of DIM analogs for the treatment of highly aggressive breast cancer.
Vanderlaag, Kathryn Elisabeth (2007). Mechanisms of growth inhibition induced by methylene-substituted and ring-substituted dims in breast cancer cells. Doctoral dissertation, Texas A&M University. Available electronically from