Herbs, Herbal Compounds and Nutrients that Synergize with Chemotherapeutic Agents

Low concentrations of diindolylmethane, a metabolite of indole-3-carbinol, protect against oxidative stress in a BRCA1-dependent manner.
The indole-3-carbinol (I3C) metabolite 3,3′-diindolylmethane (DIM) is a proposed cancer prevention agent for various tumor types, including breast cancer. Here, we show that DIM up-regulates expression of the tumor suppressor protein BRCA1 in carcinoma and normal cell types. Up-regulation of BRCA1 was dose and time dependent, and it was observed at physiologically relevant micromolar and submicromolar DIM concentrations when cells were exposed for 72 hours. Treatment with the parent compound (I3C) or DIM (1 micromol/L) protected against cell killing due to H(2)O(2) and other oxidants, and the protection was abrogated by knockdown of BRCA1. DIM stimulated signaling by the antioxidant transcription factor NFE2L2 (NRF2) through the antioxidant response element in a BRCA1-dependent manner. We further showed that DIM rapidly stimulated phosphorylation of BRCA1 on Ser (1387) and Ser (1524) and that these phosphorylations are required for protection against oxidative stress. DIM-induced phosphorylation of BRCA1 on Ser (1387) was dependent on ataxia-telangiectasia mutated. Finally, in our assay systems, H(2)O(2)-induced cell death was not due to apoptosis. However, a significant component of cell death was attributable to autophagy, and both DIM and BRCA1 inhibited H(2)O(2)-induced autophagy. Our findings suggest that low concentrations of DIM protect cells against oxidative stress via the tumor suppressor BRCA1 by several distinct mechanisms. Cancer Res. 2009 Aug 1;69(15):6083-91. Epub 2009 Jul 21. (Fan S, et al 2009)

The dietary phytochemical indole-3-carbinol is a natural elastase enzymatic inhibitor that disrupts cyclin E protein processing.
Indole-3-carbinol (I3C), a naturally occurring component of Brassica vegetables, such as broccoli, cabbage, and Brussels sprouts, induces a G(1) cell-cycle arrest of human breast cancer cells, although the direct cellular targets that mediate this process are unknown. Treatment of highly invasive MDA-MB-231 breast cancer cells with I3C shifted the stable accumulation of cyclin E protein from the hyperactive lower-molecular-mass 35-kDa form that is associated with cancer cell proliferation and poor clinical outcomes to the 50-kDa cyclin E form that typically is expressed in normal mammary tissue. An in vitro cyclin E processing assay, in combination with zymography, demonstrated that I3C, but not its natural dimer, 3,3′-diindolylmethane, disrupts proteolytic processing of the 50-kDa cyclin E into the lower-molecular-mass forms by direct inhibition of human neutrophil elastase enzymatic activity. Analysis of elastase enzyme kinetics using either cyclin E or N-methoxysuccinyl-Ala-Ala-Pro-Val-p-nitroanalide as substrates demonstrated that I3C acts as a noncompetitive inhibitor of elastase activity with an inhibitory constant of approximately 12 microM. Finally, siRNA ablation of neutrophil elastase protein production in MDA-MB-231 cells mimicked the I3C-disrupted processing of the 50-kDa cyclin E protein and the indole-induced cell-cycle arrest. Taken together, our results demonstrate that elastase is the first identified specific target protein for I3C and that the direct I3C inhibition of elastase enzymatic activity implicates the potential use of this indole, or related compounds, in targeted therapies of human breast cancers where high elastase levels are correlated with poor prognosis. Proc Natl Acad Sci U S A. 2008 Dec 16;105(50):19750-5. Epub 2008 Dec 8. (Nguyen HH, et al 2008)

Indole-3-carbinol inhibits Sp1-induced matrix metalloproteinase-2 expression to attenuate migration and invasion of breast cancer cells.
Indole-3-carbinol (I3C), a major indole metabolite in cruciferous vegetables, has been shown to inhibit invasion of breast cancer cells. This study addressed the effect of I3C on the expression of matrix metalloproteinases (MMPs) and clarified the underlying mechanism. Migration, invasion, and MMP-2 activity of MCF-7 breast cancer cells were dose-dependently inhibited by I3C. In addition, the MMP-2 mRNA level was also reduced by I3C. Promoter deletion and mutation analysis suggested that I3C inhibited MMP-2 gene transcription via the -85/-7 bp promoter region and the Sp1 transcription factor binding site located within the -72/-64 bp promoter region was important for the inhibition. Chromatin immunoprecipitation assay confirmed that Sp1 proteins constitutively bound to this consensus sequence in vivo and that the binding was attenuated by I3C. In addition, I3C inhibited the extracellular signal-regulated kinase (ERK) signaling pathway in MCF-7 cells. The results suggest that I3C inhibits MMP-2 expression by blocking the ERK/Sp1-mediated gene transcription to attenuate migration and invasion of breast cancer cells. J Agric Food Chem. 2009 Jan 14;57(1):76-82. (Hung WC, Chang HC. 2009)

Indole-3-carbinol inhibits MDA-MB-231 breast cancer cell motility and induces stress fibers and focal adhesion formation by activation of Rho kinase activity.Indole-3-carbinol (I3C), a phytochemical derived from cruciferous vegetables such as broccoli and Brussels sprouts, has potent antiproliferative effects in human breast cancer cells and has been shown to decrease metastatic spread of tumors in experimental animals. Using chemotaxis and fluorescent-bead cell motility assays, we demonstrated that I3C significantly decreased the in vitro migration of MDA-MB-231 cells, a highly invasive breast cancer cell line. Immunofluorescence staining of the actin cytoskeleton revealed that concurrent with the loss of cell motility, I3C treatment significantly increased stress fiber formation. Furthermore, I3C induced the localization of the focal adhesion component vinculin and tyrosine-phosphorylated proteins to the cell periphery, which implicates an indole-dependent enhancement of focal adhesions within the outer boundary of the cells. Coimmunoprecipitation analysis of focal adhesion kinase demonstrated that I3C stimulated the dynamic formation of the focal adhesion protein complex without altering the total level of individual focal adhesion proteins. The RhoA-Rho kinase pathway is involved in stress fiber and focal adhesion formation, and I3C treatment stimulated Rho kinase enzymatic activity and cofilin phosphorylation, which is a downstream target of Rho kinase signaling, but did not increase the level of active GTP-bound RhoA. Exposure of MDA-MB-231 cells to the Rho kinase inhibitor Y-27632, or expression of dominant negative RhoA ablated the I3C induced formation of stress fibers and of peripheral focal adhesions. Expression of constitutively active RhoA mimicked the I3C effects on both processes. Taken together, our data demonstrate that I3C induces stress fibers and peripheral focal adhesions in a Rho kinase-dependent manner that leads to an inhibition of motility in human breast cancer cells. Int J Cancer. 2009 May 15;124(10):2294-302. (Brew CT, et al 2009)

OSU-A9, a Potent Indole-3-Carbinol Derivative, Suppresses Breast Tumor Growth by Targeting the Akt-NF-{kappa}B Pathway and Stress Response Signaling.
The molecular heterogeneity of human tumors challenges the development of effective preventive and therapeutic strategies. To overcome this issue, a rational approach is the concomitant targeting of clinically relevant cellular abnormalities with combination therapy or a potent multi-targeted agent. OSU-A9 is a novel indole-3-carbinol derivative that retains the parent compound’s ability to perturb multiple components of oncogenic signaling, but provides marked advantages in chemical stability and antitumor potency. Here, we show that OSU-A9 exhibits two-orders-of-magnitude greater potency than indole-3-carbinol in inducing apoptosis in various breast cancer cell lines with distinct genetic abnormalities, including MCF-7, MDA-MB-231, and SKBR3, with IC(50) in the range of 1.2 – 1.8 muM vis-à-vis 200 muM for indole-3-carbinol. This differential potency was paralleled by OSU-A9’s superior activity against multiple components of the Akt-NF-kappaB and stress response signaling pathways. Notable among these were the increased estrogen receptor beta/estrogen receptor alpha expression ratio, reduced expression of HER2 and CXCR4, and the upregulation of arylhydrocarbon receptor expression and its downstream target Nrf2. Nonmalignant MCF-10A cells were resistant to OSU-A9’s antiproliferative effects. Daily oral administration of OSU-A9 at 25 and 50 mg/kg for 49 days significantly inhibited MCF-7 tumor growth by 59% and 70%, respectively, without overt signs of toxicity or evidence of induced hepatic biotransformation enzymes. In summary, OSU- A9 is a potent, orally bioavailable inhibitor of the Akt-NF-kappaB signaling network, targeting multiple aspects of breast tumor pathogenesis and progression. Thus, its translational potential for the treatment or prevention of breast cancer warrants further investigation. Carcinogenesis. 2009 Aug 25. [Epub ahead of print] (Weng JR, et al 2009)

3,3′-diindolylmethane induction of p75NTR-dependent cell death via the p38 mitogen-activated protein kinase pathway in prostate cancer cells.
The p75(NTR) functions as a tumor suppressor in prostate epithelial cells, where its expression declines with progression to malignant cancer. Previously, we showed that treatment with the nonsteroidal anti-inflammatory drug, indomethacin, induced p75(NTR) expression in the T24 cancer cell line leading to p75(NTR)-mediated decreased survival. Utilizing the indole moiety of indomethacin as a pharmacophore, we identified in rank-order with least efficacy, ketorolac, etodolac, indomethacin, 5-methylindole-3-acetic acid, indole-3-carbinol, and 3,3′-diindolylmethane (DIM) exhibiting greatest activity for induction of p75(NTR) levels and inhibition of cell survival. Prostate (PC-3, DU-145) and bladder (T24) cancer cells were more sensitive to DIM induction of p75(NTR)-associated loss of survival than breast (MCF7) and fibroblast (3T3) cells. Transfection of the PC-3 prostate cell line with a dominant-negative form of p75(NTR) before DIM treatment significantly rescued cell survival demonstrating a cause and effect relationship between DIM induction of p75(NTR) levels and inhibition of survival. Furthermore, siRNA knockdown of the p38 mitogen-activated protein kinase (MAPK) protein prevented induction of p75(NTR) by DIM in the PC-3 prostate cell line. DIM treatment induced phosphorylation of p38 MAPK as early as within 1 minute. Collectively, we identify DIM as an indole capable of inducing p75(NTR)-dependent apoptosis via the p38 MAPK pathway in prostate cancer cells. Cancer Prev Res (Phila Pa). 2009 Jun;2(6):566-71. Epub 2009 May 26 (Khwaja FS, Wynne S, Posey I, Djakiew D. 2009)