1,1-Bis(3′-Indolyl)-1-(p-substitutedphenyl)methanes Inhibit Growth, Induce Apoptosis, and Decrease the Androgen Receptor in LNCaP Prostate Cancer Cells through Peroxisome Proliferator-Activated Receptor γ-Independent Pathways

Assessment of NR4A Ligands That Directly Bind and Modulate the Orphan Nuclear Receptor Nurr1

Nurr1/NR4A2 is an orphan nuclear receptor transcription factor implicated as a drug target for neurological disorders including Alzheimer's and Parkinson's diseases. Previous studies identified small-molecule NR4A nuclear receptor modulators, but it remains unclear if these ligands affect transcription via direct binding to Nurr1. We assessed 12 ligands reported to affect NR4A activity for Nurr1-dependent and Nurr1-independent transcriptional effects and the ability to bind the Nurr1 ligand-binding domain (LBD). Protein NMR structural footprinting data show that amodiaquine, chloroquine, and cytosporone B bind the Nurr1 LBD; ligands that do not bind include C-DIM12, celastrol, camptothecin, IP7e, isoalantolactone, ethyl 2-[2,3,4-trimethoxy-6-(1-octanoyl)phenyl]acetate (TMPA), and three high-throughput screening hit derivatives. Importantly, ligands that modulate Nurr1 transcription also show Nurr1-independent effects on transcription in a cell type-specific manner, indicating that care should be taken when interpreting the functional response of these ligands in transcriptional assays. These findings should help focus medicinal chemistry efforts that desire to optimize Nurr1-binding ligands.

Oxidized analogs of Di(1H-indol-3-yl)methyl-4-substituted benzenes are NR4A1-dependent UPR inducers with potent and safe anti-cancer activity

Di(1H-indol-3-yl)(4-trifluoromethylphenyl)methane (DIM-Ph-4-CF3) is an analog of orphan nuclear receptor 4A1 (NR4A1) ligand cytosporone B. We have synthesized several oxidation products of DIM-Ph-4-CF3, focusing on analogs with electron-withdrawing or donating groups at their phenyl ring 4-positions, and examined their anti-cancer activity and mechanism-of-action. Mesylates (DIM-Ph-4-X+ OMs-s) having CF3, CO2Me and Cl groups were more effective inhibitors of cancer cell viability than their precursors. 19F NMR spectroscopy and differential scanning calorimetry strongly indicated interactions of DIM-Ph-4-CF3+ OMs- with the NR4A1 ligand binding domain, and compound-induced apoptosis of prostate cancer cells was dependent on NR4A1. DIM-Ph-4-CF3+ OMs- showed robust inhibition of LNCaP prostate cancer xenografts with no apparent toxicity. In vitro and in vivo, DIM-Ph-4-CF3+ OMs- activated proapoptotic unfolded protein response (UPR) signaling in prostate cancer cells. Independently of DIM-Ph-4-CF3+ OMs-, the bulk of NR4A1 localized to the cytoplasm in various cancer cell lines, suggesting a cytoplasmic mechanism-of-action of DIM-Ph-4-CF3+ OMs- in UPR induction and cell death. In summary, the data suggest that oxidized analogs of DIM-Ph-4-CF3 possess potent and safe anti-cancer activity which is mediated through UPR signaling downstream of NR4A1 binding.

Pharmacological activation of PPARγ inhibits hypoxia-induced proliferation through a caveolin-1-targeted and -dependent mechanism in PASMCs

Previously, we and others have demonstrated that activation of peroxisome proliferator-activated receptor γ (PPARγ) by specific pharmacological agonists inhibits the pathogenesis of chronic hypoxia-induced pulmonary hypertension (CHPH) by suppressing the proliferation and migration in distal pulmonary arterial smooth muscle cells (PASMCs). Moreover, these beneficial effects of PPARγ are mediated by targeting the intracellular calcium homeostasis and store-operated calcium channel (SOCC) proteins, including the main caveolae component caveolin-1. However, other than the caveolin-1 targeted mechanism, in this study, we further uncovered a caveolin-1 dependent mechanism within the activation of PPARγ by the specific agonist GW1929. First, effective knockdown of caveolin-1 by small-interfering RNA (siRNA) markedly abolished the upregulation of GW1929 on PPARγ expression at both mRNA and protein levels; Then, in HEK293T, which has previously been reported with low endogenous caveolin-1 expression, exogenous expression of caveolin-1 significantly enhanced the upregulation of GW1929 on PPARγ expression compared with nontransfection control. In addition, inhibition of PPARγ by either siRNA or pharmacological inhibitor T0070907 led to increased phosphorylation of cellular mitogen-activated protein kinases ERK1/2 and p38. In parallel, GW1929 dramatically decreased the expression of the proliferative regulators (cyclin D1 and PCNA), whereas it increased the apoptotic factors (p21, p53, and mdm2) in hypoxic PASMCs. Furthermore, these effects of GW1929 could be partially reversed by recovery of the drug treatment. In combination, PPARγ activation by GW1929 reversibly drove the cell toward an antiproliferative and proapoptotic phenotype in a caveolin-1-dependent and -targeted mechanism.

Peroxisome Proliferator-Activated Receptor γ-Mediated Inhibition on Hypoxia-Triggered Store-Operated Calcium Entry. A Caveolin-1-Dependent Mechanism

Our previous publication demonstrated that peroxisome proliferator-activated receptor γ (PPARγ) inhibits the pathogenesis of chronic hypoxia (CH)-induced pulmonary hypertension by targeting store-operated calcium entry (SOCE) in rat distal pulmonary arterial smooth muscle cells (PASMCs). In this study, we aim to determine the role of a membrane scaffolding protein, caveolin-1, during the suppressive process of PPARγ on SOCE. Adult (6-8 weeks) male Wistar rats (200-250 g) were exposed to CH (10% O2) for 21 days to establish CH-induced pulmonary hypertension. Primary cultured rat distal PASMCs were applied for the molecular biological experiments. First, hypoxic exposure led to 2.5-fold and 1-fold increases of caveolin-1 protein expression in the distal pulmonary arteries and PASMCs, respectively. Second, effective knockdown of caveolin-1 significantly reduced hypoxia-induced SOCE for 58.2% and 41.5%, measured by Mn(2+) quenching and extracellular Ca(2+) restoration experiments, respectively. These results suggested that caveolin-1 acts as a crucial regulator of SOCE, and hypoxia-up-regulated caveolin-1 largely accounts for hypoxia-elevated SOCE in PASMCs. Then, by using a high-potency PPARγ agonist, GW1929, we detected that PPARγ activation inhibited SOCE and caveolin-1 protein for 62.5% and 59.8% under hypoxia, respectively, suggesting that caveolin-1 also acts as a key target during the suppressive process of PPARγ on SOCE in PASMCs. Moreover, by using effective small interfering RNAs against PPARγ and caveolin-1, and PPARγ antagonist, T0070907, we observed that PPARγ plays an inhibitory role on caveolin-1 protein by promoting its lysosomal degradation, without affecting the messenger RNA level. PPARγ inhibits SOCE, at least partially, by suppressing cellular caveolin-1 protein in PASMCs.

Evaluation of self-emulsified DIM-14 in dogs for oral bioavailability and in Nu/nu mice bearing stem cell lung tumor models for anticancer activity

3, 3-Diindolylmethane-14 (DIM-14), a novel lipophilic derivative of DIM, has demonstrated anticancer activity in different types of cancers. However, poor solubility and low oral bioavailability of DIM-14 limit its translational benefits in vivo. This study was carried out to improve the oral bioavailability of DIM-14 via self-emulsifying drug (SED) delivery system in dogs and to evaluate pharmacodynamic characteristics of SED against H1650 stem cell tumor models. DIM-14 was incorporated into an oil, surfactant, and co-surfactant mixture using labrafil and tween-80 to obtain SED. SED were characterized by droplet size, polydispersitiy index (PDI), zeta potential, entrapment efficiency (EE), in vitro permeability and drug release (investigated with Caco-2 monolayers and dissolution apparatus respectively). Pharmacokinetic parameters in dogs were evaluated and analyzed using Winonlin. Anti-tumor activity was carried out in H1650 lung tumor model. Particle size of SED was between 230 and 246 nm and surface charge was negative and ranged from 26.50 to 28.69 mV. Entrapment efficiency of SED was 85%. Pharmacokinetic evaluation in dogs showed increased Cmax (39.18 ± 7.34 vs 21.68 ± 6.3 μg·dL-1), higher AUC0-t (34,481.34 ± 1125.46 vs 14,159.53 ± 702.20 μg·min·dL-1) and improved absorption with 3 times more bioavailability of SED compared to DIM-14 solution. SED showed ~30-59% tumor volume/weight reduction in H1650 tumor model compared to DIM-P solution. Our studies demonstrate the potential application of self-emulsifying drug delivery system (SEDDS), that enhances oral absorption of DIM-14 and increased anti-tumor activity against lung tumor models.

The determination of the absolute configuration of a chiral 2,3'-diindolylarylmethane by NMR spectroscopy

We present the determination of the absolute configuration of a chiral 2,3'-diindolylarylmethane 1 by using the combination of NMR spectroscopic and circular dichroism techniques. The results would be useful for the future study of the effect of chirality on the biological activity of 2,3'-diindolylarylmethanes.

Small molecule-induced mitochondrial disruption directs prostate cancer inhibition via UPR signaling

We previously identified SMIP004 (N-(4-butyl-2-methyl-phenyl) acetamide) as a novel inducer of cancer-cell selective apoptosis of human prostate cancer cells. SMIP004 decreased the levels of positive cell cycle regulators, upregulated cyclin-dependent kinase inhibitors, and resulted in G1 arrest, inhibition of colony formation in soft agar, and cell death. However, the mechanism of SMIP004-induced cancer cell selective apoptosis remained unknown. Here, we used chemical genomic and proteomic profiling to unravel a SMIP004-induced pro-apoptotic pathway, which initiates with disruption of mitochondrial respiration leading to oxidative stress. This, in turn, activates two pathways, one eliciting cell cycle arrest by rapidly targeting cyclin D1 for proteasomal degradation and driving the transcriptional downregulation of the androgen receptor, and a second pathway that activates pro-apoptotic signaling through MAPK activation downstream of the unfolded protein response (UPR). SMIP004 potently inhibits the growth of prostate and breast cancer xenografts in mice. Our data suggest that SMIP004, by inducing mitochondrial ROS formation, targets specific sensitivities of prostate cancer cells to redox and bioenergetic imbalances that can be exploited in cancer therapy.

Theranostic tumor homing nanocarriers for the treatment of lung cancer

The drugs/strategies to selectively inhibit tumor blood supply have generated interest in recent years for enhancement of cancer therapeutics. The objective of this study was to formulate tumor homing PEGylated CREKA peptide conjugated theranostic nanoparticles of DIM-C-pPhC6H5 (DIM-P) and investigate in vivo antitumor activity as well as evaluate the targeted efficiency to lung tumors using imaging techniques. DIM-P loaded Nanoparticles (NCs-D) were prepared using lipids, and DOGS-NTA-Ni and the surface of NCs-D were modified with PEGylated CREKA peptide (PCNCs-D). PCNCs-D showed 3 fold higher binding to clotted plasma proteins in tumor vasculature compared to NCs-D. PCNCs-D showed 26%±4% and 22%±5% increase in tumor reduction compared to NCs-D in metastatic and orthotopic models respectively. In-vivo imaging studies showed ~40 folds higher migration of PCNCs-Di in tumor vasculature than NCs-Di. Our studies demonstrate the role of PCNCs-D as theranostic tumor homing drug delivery and imaging systems for lung cancer diagnosis and treatment.

FROM THE CLINICAL EDITOR

This study demonstrates a very efficient delivery system to address lung cancer growth through blood supply inhibition.

Relative impact of 3- and 5-hydroxyl groups of cytosporone B on cancer cell viability

A novel and the shortest route, thus far, for preparing cytosporone B (Csn-B) is reported. Csn-B and two analogs were used to probe the importance of hydroxyl groups at the 3- and 5-positions of the Csn-B benzene ring in inhibiting the viability of human H460 lung cancer and LNCaP prostate cancer cells, inducing H460 cell apoptosis, and interacting with the NR4A1 (TR3) ligand-binding domain (LBD). These studies indicate that Csn-B and 5-Me-Csn-B, having a phenolic hydroxyl at the 3-position of their aromatic rings, had similar activities in inhibiting cancer cell viability and in inducing apoptosis, whereas 3,5-(Me)₂-Csn-B was unable to do so. These results are in agreement with ligand-binding experiments showing that the interaction with the NR4A1 LBD required the presence of the 3-hydroxyl group.

3,3'-diindolylmethane induces activating transcription factor 3 (ATF3) via ATF4 in human colorectal cancer cells

3,3'-Diindolylmethane (DIM) is a major in vivo condensation product of indole-3-carbinol, which is present in cruciferous vegetables. Although these compounds have been widely implicated in antitumorigenic and proapoptotic properties in animal as well as in vitro models of cancer, the underlying cellular mechanisms regulated by DIM are only partially understood. Activating transcription factor 3 (ATF3) is a member of the ATF/c-AMP response element-binding (CREB) subfamily of the basic-region leucine zipper family and has been known to induce apoptosis in human colorectal cancer (CRC) cells. The present study was performed to elucidate the molecular mechanism of ATF3 induction by DIM in human CRC cells. The DIM treatment induced apoptosis and induced ATF3 gene expression at protein and messenger RNA levels. DIM increased ATF3 promoter activity, and the region of -84 to +34 within ATF3 promoter was responsible for promoter activation by DIM. This region contained an ATF binding site. Deletion and point mutation of the ATF binding site (-23 to -16) abolished ATF3 promoter activation by DIM, and overexpression of ATF4 enhanced ATF3 transactivation. Chromatin immunoprecipitation assay confirmed the binding of ATF4 in the ATF3 promoter. Inhibition of ATF4 expression by small interference RNA results in repression of DIM-induced ATF3 expression. The current study demonstrates that DIM stimulates ATF3 expression through ATF4-mediated pathway and subsequently induces apoptosis in human CRC cells.

A peroxisome proliferator-activated receptor ligand MCC-555 imparts anti-proliferative response in pancreatic cancer cells by PPARgamma-independent up-regulation of KLF4

MCC-555 is a novel PPARα/γ dual ligand of the thiazolidinedione class and was recently developed as an anti-diabetic drug with unique properties. MCC-555 also has anti-proliferative activity through growth inhibition and apoptosis induction in several cancer cell types. Our group has shown that MCC-555 targets several proteins in colorectal tumorigenesis including nonsteroidal anti-inflammatory drug (NSAID)-activated gene (NAG-1) which plays an important role in chemoprevention responsible for chemopreventive compounds. NAG-1 is a member of the TGF-β superfamily and is involved in tumor progression and development; however, NAG-1's roles in pancreatic cancer have not been studied. In this report, we found that MCC-555 alters not only NAG-1 expression, but also p21 and cyclin D1 expression. NAG-1 and p21 expression was not blocked by PPARγ-specific antagonist GW9662, suggesting that MCC-555-induced NAG-1 and p21 expression is independent of PPARγ activation. However, decreasing cyclin D1 by MCC-555 seems to be affected by PPARγ activation. Further, we found that the GC box located in the NAG-1 promoter play an important role in NAG-1 transactivation by MCC-555. Subsequently, we screened several transcription factors that may bind to the GC box region in the NAG-1 promoter and found that KLF4 potentially binds to this region. Expression of KLF4 precedes NAG-1 and p21 expression in the presence of MCC-555, whereas blocking KLF4 expression using specific KLF4 siRNA showed that both NAG-1 and p21 expression by MCC-555 was blocked. In conclusion, MCC-555's actions on anti-proliferation involve both PPARγ-dependent and -independent pathways, thereby enhancing anti-tumorigenesis in pancreatic cancer cells.

Antiandrogenic and growth inhibitory effects of ring-substituted analogs of 3,3'-diindolylmethane (ring-DIMs) in hormone-responsive LNCaP human prostate cancer cells

BACKGROUND

Cruciferous vegetables protect against prostate cancer. Indole-3-carbinol (I3C) and its major metabolite 3,3'-diindolylmethane (DIM), exhibit antitumor activities in vitro and in vivo. Several synthetic ring-substituted dihaloDIMs (ring-DIMs) appear to have increased anticancer activity.

METHODS

Inhibition of LNCaP prostate cancer cell growth was measured by a WST-1 cell viability assay. Cytoplasmic and nuclear proteins were analyzed by immunoblotting and immunofluorescence. Androgen receptor (AR) activation was assessed by measuring prostate-specific antigen (PSA) expression and using LNCaP cells containing human AR and an AR-dependent probasin promoter-green fluorescent protein (GFP) construct.

RESULTS

Like DIM, several ring-substituted dihaloDIM analogs, namely 4,4'-dibromo-, 4,4'-dichloro-, 7,7'-dibromo-, and 7,7'-dichloroDIM, significantly inhibited DHT-stimulated growth of LNCaP cells at concentrations ≥1 µM. We observed structure-dependent differences for the effects of the ring-DIMs on AR expression, nuclear AR accumulation and PSA levels in LNCaP cells after 24 hr. Both 4,4'- and 7,7'-dibromoDIM decreased AR protein and mRNA levels, whereas 4,4'- and 7,7'-dichloroDIM had minimal effect. All four dihaloDIMs (10 and 30 µM) significantly decreased PSA protein and mRNA levels. Immuofluorescence studies showed that only the dibromoDIMs increased nuclear localization of AR. All ring-DIMs caused a concentration-dependent decrease in fluorescence induced by the synthetic androgen R1881 in LNCaP cells transfected with wild-type human AR and an androgen-responsive probasin promoter-GFP gene construct, with potencies up to 10-fold greater than that of DIM.

CONCLUSION

The antiandrogenic effects of ring-DIMs suggest they may form the basis for the development of novel agents against hormone-sensitive prostate cancer, alone or in combination with other drugs.

Increased androgen receptor transcription: a cause of castration-resistant prostate cancer and a possible therapeutic target

Few effective therapies exist for the treatment of castration-resistant prostate cancer (CRPC). Recent evidence suggests that CRPC may be caused by augmented androgen/androgen receptor (AR) signaling, generally involving AR overexpression. Aberrant androgen/AR signaling associated with AR overexpression also plays a key role in prostate carcinogenesis. Although AR overexpression could be attributed to gene amplification, only 10-20% of CRPCs exhibit AR gene amplification, and aberrant AR expression in the remaining instances of CRPC is thought to be attributed to transcriptional, translational, and post-translational mechanisms. Overexpression of AR at the protein level, as well as the mRNA level, has been found in CRPC, suggesting a key role for transcriptional regulation of AR expression. Since the analysis of the AR promoter region in the 1990s, several transcription factors have been reported to regulate AR transcription. In this review, we discuss the molecules involved in the control of AR gene expression, with emphasis on its transcriptional control by transcription factors in prostate cancer. We also consider the therapeutic potential of targeting AR expression.

Activation of nuclear TR3 (NR4A1) by a diindolylmethane analog induces apoptosis and proapoptotic genes in pancreatic cancer cells and tumors

NR4A1 (Nur77, TR3) is overexpressed in pancreatic tumors and activation of TR3 by 1,1-bis(3'-indolyl)-1-(p-methoxyphenyl)methane (DIM-C-pPhOCH(3)) inhibits cell and tumor growth and induces apoptosis. Microarray analysis demonstrates that in L3.6pL pancreatic cancer cells DIM-C-pPhOCH(3) induces genes associated with metabolism, homeostasis, signal transduction, transcription, stress, transport, immune responses, growth inhibition and apoptosis. Among the most highly induced growth inhibitory and proapoptotic genes including activating transcription factor 3 (ATF3), p21, cystathionase, dual specificity phosphatase 1 and growth differentiation factor 15, RNA interference studies demonstrated that induction of all but the later gene by DIM-C-pPhOCH(3) were TR3-dependent. We also observed that DIM-C-pPhOCH(3) induced Fas ligand and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and induction of TRAIL was ATF3 dependent. Results of this and previous studies demonstrate that TR3 is unique among nuclear receptors since nuclear TR3 is activated or deactivated by diindolylmethane derivatives to induce different apoptotic and growth inhibitory pathways that inhibit pancreatic cancer cell and tumor growth.

Targeting NR4A1 (TR3) in cancer cells and tumors

INTRODUCTION

Nuclear receptor 4A1(NR4A1) (testicular receptor 3 (TR3), nuclear hormone receptor (Nur)77) is a member of the nuclear receptor superfamily of transcription factors and is highly expressed in multiple tumor types. RNA interference studies indicate that NR4A1 exhibits growth-promoting, angiogenic and prosurvival activity in most cancers.

AREAS COVERED

Studies on several apoptosis-inducing agents that activate nuclear export of NR4A1, which subsequently forms a mitochondrial NR4A1-bcl-2 complex that induces the intrinsic pathway for apoptosis are discussed. Cytosporone B and related compounds that induce NR4A1-dependent apoptosis in cancer cells through both modulation of nuclear NR4A1 and nuclear export are discussed. A relatively new class of diindolylmethane analogs (C-DIMs) including 1,1-bis(3'-indolyl)-1-(p-methoxyphenyl)methane (DIM-C-pPhOCH(3)) (NR4A1 activator) and 1,1-bis(3'-indolyl)-1-(p-hydroxyphenyl)methane (DIM-C-pPhOH) (NR4A1 deactivator) are discussed in more detail. These anticancer drugs (C-DIMs) act strictly through nuclear NR4A1 and induce apoptosis in cancer cells and tumors.

EXPERT OPINION

It is clear that NR4A1 plays an important pro-oncogenic role in cancer cells and tumors, and there is increasing evidence that this receptor can be targeted by anticancer drugs that induce cell death via NR4A1-dependent and -independent pathways. Since many of these compounds exhibit relatively low toxicity, they represent an important class of mechanism-based anticancer drugs with excellent potential for clinical applications.

Inhalation delivery of a novel diindolylmethane derivative for the treatment of lung cancer

The purpose of this study was to determine the anticancer efficacy of 1,1-bis (3'-indolyl)-1-(p-biphenyl) methane (DIM-C-pPhC₆H₅) by inhalation delivery alone and in combination with i.v. docetaxel in a murine model for lung cancer. An aqueous DIM-C-pPhC₆H₅ formulation was characterized for its aerodynamic properties. Tumor-bearing athymic nude mice were exposed to nebulized DIM-C-pPhC₆H₅, docetaxel, or combination (DIM-C-pPhC₆H₅ plus docetaxel) using a nose-only exposure technique. The aerodynamic properties included mass median aerodynamic diameter of 1.8 ± 0.3 μm and geometric SD of 2.31 ± 0.02. Lung weight reduction in mice treated with the drug combination was 64% compared with 40% and 47% in mice treated with DIM-C-pPhC₆H₅ aerosol and docetaxel alone, respectively. Combination treatment decreased expression of Akt, cyclin D1, survivin, Mcl-1, NF-κB, IκBα, phospho-IκBα, and vascular endothelial growth factor (VEGF) and increased expression of c-Jun NH₂-terminal kinase 2 and Bad compared with tumors collected from single-agent treatment and control groups. DNA fragmentation was also enhanced in mice treated with the drug combination compared with docetaxel or DIM-C-pPhC₆H₅ alone. Combination treatment decreased expressions of VEGF and CD31 compared with single-agent treated and control groups. These results suggest that DIM-C-pPhC₆H₅ aerosol enhanced the anticancer activity of docetaxel in a lung cancer model by activating multiple signaling pathways. The study provides evidence that DIM-C-pPhC₆H₅ can be used alone or in combination with other drugs for the treatment of lung cancer using the inhalation delivery approach.

Kallikreins on steroids: structure, function, and hormonal regulation of prostate-specific antigen and the extended kallikrein locus

The 15 members of the kallikrein-related serine peptidase (KLK) family have diverse tissue-specific expression profiles and putative proteolytic functions. The kallikrein family is also emerging as a rich source of disease biomarkers with KLK3, commonly known as prostate-specific antigen, being the current serum biomarker for prostate cancer. The kallikrein locus is also notable because it is extraordinarily responsive to steroids and other hormones. Indeed, at least 14 functional hormone response elements have been identified in the kallikrein locus. A more comprehensive understanding of the transcriptional regulation of kallikreins may help the field make more informed hypotheses about the physiological functions of kallikreins and their effectiveness as biomarkers. In this review, we describe the organization of the kallikrein locus and the structure of kallikrein genes and proteins. We also focus on the transcriptional regulation of kallikreins by androgens, progestins, glucocorticoids, mineralocorticoids, estrogens, and other hormones in animal models and human prostate, breast, and reproductive tract tissues. The interaction of the androgen receptor with androgen response elements in the promoter and enhancer of KLK2 and KLK3 is also summarized in detail. There is evidence that all kallikreins are regulated by multiple nuclear receptors. Yet, apart from KLK2 and KLK3, it is not clear whether all kallikreins are direct transcriptional targets. Therefore, we argue that gaining more detailed information about the mechanisms that regulate kallikrein expression should be a priority of future studies and that the kallikrein locus will continue to be an important model in the era of genome-wide analyses.

Activation of nerve growth factor-induced B alpha by methylene-substituted diindolylmethanes in bladder cancer cells induces apoptosis and inhibits tumor growth

Nerve growth factor-induced B (NGFI-B) genes are orphan nuclear receptors, and NGFI-B alpha (Nur77, TR3) is overexpressed in bladder tumors and bladder cancer cells compared with nontumorous bladder tissue. 1,1-Bis(3'-indolyl)-1-(p-methoxyphenyl)-methane (DIM-C-pPhOCH(3)) and 1,1-bis(3'-indolyl)-1-(p-phenyl)methane have previously been identified as activators of Nur77, and both compounds inhibited growth and induced apoptosis of UC-5 and KU7 bladder cancer cells. The proapoptotic effects of methylene-substituted diindolylmethanes (C-DIMs) were unaffected by cotreatment with leptomycin B and were dependent on nuclear Nur77, and RNA interference with a small inhibitory RNA for Nur77 (iNur77) demonstrated that C-DIM-induced activation of apoptosis was Nur77-dependent. Microarray analysis of DIM-C-pPhOCH(3)-induced genes in UC-5 bladder cancer cells showed that this compound induced multiple Nur77-dependent proapoptotic or growth inhibitory genes including tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), cystathionase, p21, p8, and sestrin-2. DIM-C-pPhOCH(3) (25 mg/kg/d) also induced apoptosis and inhibited tumor growth in athymic nude mice bearing KU7 cells as xenografts, demonstrating that Nur77-active C-DIMs exhibit potential for bladder cancer chemotherapy by targeting Nur77, which is overexpressed in this tumor type.

Minireview: modulation of hormone receptor signaling by dietary anticancer indoles

Indole-3-carbinol and its diindole condensation product 3-3'-diindolylmethane are dietary phytochemicals that have striking anticarcinogenic properties in human cancer cells. Molecular, cellular, physiological, and clinical studies have documented that both indole-3-carbinol and 3-3'-diindolylmethane have potent endocrine modulating activities through a myriad of mechanisms. The focus of this review is to discuss the evidence that directly links the anticancer actions of these two indole compounds to the control of steroid receptor and growth factor receptor signaling.

Peroxisome proliferator-activated receptor gamma-dependent activity of indole ring-substituted 1,1-bis(3'-indolyl)-1-(p-biphenyl)methanes in cancer cells

PURPOSE

1,1-Bis(3-indolyl)-1-(p-substituted phenyl)methanes (C-DIMs) substituted in the phenyl ring with a para-, t-butyl, trifluoromethyl (DIM-C-pPhCF(3)) or phenyl (DIM-C-pPhC(6)H(5)) group activate peroxisome proliferator-activated receptor gamma (PPARgamma) in several cancer cell lines, and DIM-C-pPhCF(3) also activates the orphan receptor Nur77. In this study, we have examined the effects of 5,5'-dihydroxy, 5,5'-dimethyl, 5,5'-dibromo, 5,5'-dinitro and 5,5'-dimethoxyindole ring-substituted analogs of DIM-C-pPhC(6)H(5) on their activity as PPARgamma agonists.

METHODS

Various substituted C-DIM analogs were used to investigate their growth-inhibitory activities and activation of PPARgamma-mediated transactivation in colon and pancreatic cancer cells. Their structure-dependent induction of putative PPARgamma-responsive genes/proteins including p21, KLF-4 and caveolin1 were also determined by Western and Northern blot analysis.

RESULTS

Introduction of the 5,5'-dihydroxy and 5,5'-dimethyl substituents enhanced activation of PPARgamma in colon and pancreatic cancer cells. However, activation of p21 in Panc28 pancreatic cancer cells and induction of caveolin-1 and KLF4 in colon cancer cells by the C-DIM compounds were structure- and cell context-dependent.

CONCLUSIONS

The results demonstrate that DIM-C-pPhC(6)H(5) and indole ring-substituted analogs are selective PPARgamma modulators.

Derivation of a retinoid X receptor scaffold from peroxisome proliferator-activated receptor gamma ligand 1-Di(1H-indol-3-yl)methyl-4-trifluoromethylbenzene

PPARgamma agonist DIM-Ph-4-CF(3), a template for RXRalpha agonist (E)-3-[5-di(1-methyl-1H-indol-3-yl)methyl-2-thienyl] acrylic acid: DIM-Ph-CF(3) is reported to inhibit cancer growth independent of PPARgamma and to interact with NR4A1. As both receptors dimerize with RXR, and natural PPARgamma ligands activate RXR, DIM-Ph-4-CF(3) was investigated as an RXR ligand. It displaces 9-cis-retinoic acid from RXRalpha but does not activate RXRalpha. Structure-based direct design led to an RXRalpha agonist.1-Di(1H-indol-3-yl)methyl-4-trifluoromethylbenzene (DIM-Ph-4-CF(3)) is reported to inhibit cancer cell growth and to act as a transcriptional agonist of peroxisome proliferator-activated receptor gamma (PPARgamma) and nuclear receptor 4A subfamily member 1 (NR4A1). In addition, DIM-Ph-4-CF(3) exerts anticancer effects independent of these receptors because PPARgamma antagonists do not block its inhibition of cell growth, and the small pocket in the NR4A1 crystal structure suggests no ligand can bind. Because PPARgamma and NR4A1 heterodimerize with retinoid X receptor (RXR), and several PPARgamma ligands transcriptionally activate RXR, DIM-Ph-4-CF(3) was investigated as an RXR ligand. DIM-Ph-4-CF(3) displaces 9-cis-retinoic acid from RXRalpha but does not transactivate RXRalpha. Structure-based design using DIM-Ph-4-CF(3) as a template led to the RXRalpha transcriptional agonist (E)-3-[5-di(1-methyl-1H-indol-3-yl)methyl-2-thienyl]acrylic acid. Its docked pose in the RXRalpha ligand binding domain suggests that binding is stabilized by interactions of its carboxylate group with arginine 316, its indoles with cysteines 269 and 432, and its 1-methyl groups with hydrophobic residues lining the binding pocket. As is expected of a selective activator of RXRalpha, but not of RARs and PPARgamma, this RXRalpha agonist, unlike DIM-Ph-4-CF(3), does not appreciably decrease cancer cell growth or induce apoptosis at pharmacologically relevant concentrations.

Enhancement of docetaxel anticancer activity by a novel diindolylmethane compound in human non-small cell lung cancer

PURPOSE

This study was conducted to examine the cytotoxic effects of a peroxisome proliferator-activated receptor gamma (PPARgamma) agonist, 1,1-bis (3'-indolyl)-1-(p-biphenyl) methane (DIM-C-pPhC(6)H(5)), alone and in combination with docetaxel in vitro in A549 lung cancer cells and in vivo in nude mice bearing A549 orthotopic lung tumors.

EXPERIMENTAL DESIGN

Isobolographic method was used to calculate combination index values from cell viability data. Apoptosis was evaluated in A549 cells by terminal deoxynucleotidyl transferase-mediated nick end labeling assay and measurement of cleaved poly(ADP-ribose) polymerase level. Expression of proteins was studied by Western blotting. A549 cells were implanted to induce orthotopic lung tumors in nude mice and the efficacy of docetaxel, DIM-C-pPhC(6)H(5), or combination was determined. Apoptosis and cleaved caspase-3 expression in the harvested tissues were studied by terminal deoxynucleotidyl transferase-mediated nick end labeling and immunohistochemistry, respectively.

RESULTS

The combination index values (0.36-0.9) suggested synergistic to additive effects of docetaxel + DIM-C-pPhC(6)H(5) and resulted in the highest increase in percentage of apoptotic cells and expression of cleaved poly(ADP-ribose) polymerase, Bax, and N-cadherin compared with treatment with either agent. The combination also enhanced procaspase-3 and -9 cleavage. In vivo, docetaxel + DIM-C-pPhC(6)H(5) reduced lung weights by 57% compared with 39% by docetaxel or 22% by DIM-C-pPhC(6)H(5) alone, induced apoptosis in 43% of the tumor cells compared with 29% and 22% in tumors treated with docetaxel and DIM-C-pPhC(6)H(5), respectively, and increased procaspase-3 cleavage compared with either agent alone.

CONCLUSIONS

These findings suggest potential benefit for use of docetaxel and DIM-C-pPhC(6)H(5) combination in lung cancer treatment.

Pyrimidinyl-arylpropionic acid derivatives: viable resources in the development of new antineoplastic agents

Numerous studies have documented that various naturally derived ligands or synthetic non-thiazolidinediones (TZD) as peroxisome proliferator-activated receptor gamma (PPARgamma) agonists have shown moderate or potent antitumor activities, which is PPARgamma independent or partially dependent. However, the PPARgamma agonistic or glucose-lowering activity is ranked first more often than antitumor activity to determine promising novel PPARgamma agonists for potential clinical use. In this study, we hypothesized that there might exist some compounds with less PPARgamma agonistic activity but potent antitumor activity. Thereafter, we evaluated the PPARgamma agonistic and antitumor activity of a novel series of alpha-aryloxy-alpha-methylhydrocinnamic acid derivatives synthesized with the initial aim of developing novel PPARgamma agonists as hypoglycemic agents. MTT assay results revealed that several compounds were able to inhibit cell proliferation in a dose-dependent manner with IC(50) 12.7-29.7 microM, better than that of rosiglitazone (45.9-141 microM), although the PPARgamma agonistic activity of most compounds is much lower than rosiglitazone. Some compounds induced cell cycle arrest and apoptosis tested by Flow Cytometry. Oral administration of DH9 (100 mg/kg/d) for 21 days to BALB/c nude mice bearing xenografts including MGC-803, NCI-H460, HT-29 and OS-RC-2 cells significantly retarded tumor growth. DG8 and DJ5 showed benefits in some of the above four xenografts. Our findings demonstrate that these compounds have potent antitumor activity in vitro and in vivo and pyrimidinyl-arylpropionic acid derivatives might be viable resources in the development of new antineoplastic agents.

Structure-dependent activation of endoplasmic reticulum stress-mediated apoptosis in pancreatic cancer by 1,1-bis(3'-indoly)-1-(p-substituted phenyl)methanes

1,1-Bis(3'-indoly)-1-(p-substituted phenyl)methanes (C-DIM) exhibit structure-dependent activation of peroxisome proliferator-activated receptor gamma and nerve growth factor-induced Balpha (Nur77) and induce receptor-dependent and receptor-independent apoptosis in cancer cells and tumors. In this study, we investigated the activation of apoptosis in pancreatic cancer cells by p-bromo (DIM-C-pPhBr) and p-fluoro (DIM-C-pPhF) and structurally related analogues that do not activate either peroxisome proliferator-activated receptor gamma or Nur77. The ortho, meta, and para-bromo and -fluoro isomers all activated endoplasmic reticulum (ER) stress-dependent apoptosis in pancreatic cancer cells; however, methylation of the indole N group significantly decreased activity, suggesting that a free N was important for activation of ER stress. Both DIM-C-pPhBr and DIM-C-pPhF resembled the classic ER stress inducer thapsigargin in pancreatic cancer cells and activated ER stress markers, such as glucose-related protein 78 and the c-Jun NH(2) kinase pathway, resulting in the induction of CCAAT/enhancer-binding protein homologous protein, death receptor 5, and the extrinsic apoptotic pathway. Moreover, DIM-C-pPhBr also inhibited tumor growth in an orthotopic model for pancreatic cancer, demonstrating the clinical potential for this C-DIM compound in pancreatic cancer chemotherapy.

Suppression of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced nitric-oxide synthase 2 expression in astrocytes by a novel diindolylmethane analog protects striatal neurons against apoptosis

The progressive debilitation of motor functions in Parkinson's disease (PD) results from degeneration of dopaminergic neurons within the substantia nigra pars compacta of the midbrain. Long-term inflammatory activation of microglia and astrocytes plays a central role in the progression of PD and is characterized by activation of the nuclear factor-kappaB (NF-kappaB) signaling cascade and subsequent overproduction of inflammatory cytokines and nitric oxide (NO). Suppression of this neuroinflammatory phenotype has received considerable attention as a potential target for chemotherapy, but there are no currently approved drugs that sufficiently address this problem. The data presented here demonstrate the efficacy of a novel anti-inflammatory diindolylmethane class compound, 1,1-bis(3'-indolyl)-1-(p-t-butylphenyl)methane (DIM-C-pPhtBu), in suppressing NF-kappaB-dependent expression of inducible nitric-oxide synthase (NOS2) and NO production in astrocytes exposed to the parkinsonian neurotoxicant 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) through a mechanism distinct from that described for the thiazolidinedione-class compound, rosiglitazone. Chromatin immunoprecipitations revealed that micromolar concentrations of DIM-C-pPhtBu prevented association of the p65 subunit of NF-kappaB with enhancer elements in the Nos2 promoter but had little effect on DNA binding of either peroxisome proliferator-activated receptor-gamma (PPAR-gamma) or the nuclear corepressor NCoR2. Treatment with DIM-C-pPhtBu concomitantly suppressed NO production and protein nitration in MPTP-activated astrocytes and completely protected cocultured primary striatal neurons from astrocyte-dependent apoptosis. These data demonstrate the efficacy of DIM-C-pPhtBu in preventing the activation of NF-kappaB-dependent inflammatory genes in primary astrocytes and suggest that this class of compounds may be effective neuroprotective anti-inflammatory agents in vivo.

5,5'-Dibromo-bis(3'-indolyl)methane induces Kruppel-like factor 4 and p21 in colon cancer cells

Bis(3'-indolyl)methane (DIM) is a metabolite of the phytochemical indole-3-carbinol, and both compounds exhibit a broad spectrum of anticancer activities. We have developed a series of synthetic symmetrical ring-substituted DIM analogues, including 5,5'-dibromoDIM, which are more potent than DIM as inhibitors of cancer cell and tumor growth. In colon cancer cells, 5,5'-dibromoDIM decreased cell proliferation and inhibited G(0)-G(1)- to S-phase progression, and this was accompanied by induction of the cyclin-dependent kinase inhibitor p21 in HT-29 and RKO colon cancer cells. Mechanistic studies showed that induction of p21 in both RKO (p53 wild-type) and HT-29 (p53 mutant) cells by 5,5'-dibromoDIM was Krüppel-like factor 4 (KLF4) dependent, and induction of p53 in RKO cells was also KLF4 dependent. Analysis of the p21 promoter in p53-dependent RKO cells showed that 5,5'-dibromoDIM activated p21 gene expression through the proximal GC-rich sites 1 and 2, and chromatin immunoprecipitation assays showed that KLF4 and p53 bound to this region of the promoter, whereas in HT-29 cells unidentified upstream cis-elements were required for induction of p21. 5,5'-DibromoDIM (30 mg/kg/d) also inhibited tumor growth and induced p21 in athymic nude mice bearing RKO cells as xenografts, showing that ring-substituted DIM such as 5,5'-dibromoDIM represent a novel class of mechanism-based drugs for clinical treatment of colon cancer.

Cancer chemotherapy with indole-3-carbinol, bis(3'-indolyl)methane and synthetic analogs

Indole-3-carbinol (I3C) conjugates are phytochemicals expressed in brassica vegetables and have been associated with the anticancer activities of vegetable consumption. I3C and its metabolite bis(3'-indolyl)methane (DIM) induce overlapping and unique responses in multiple cancer cell lines and tumors, and these include growth inhibition, apoptosis and antiangiogenic activities. The mechanisms of these responses are complex and dependent on cell context. I3C and/or DIM activate or inactivate multiple nuclear receptors, induce endoplasmic reticulum stress, decrease mitochondrial membrane potential, and modulate multiple signaling pathways including kinases. DIM has been used as a template to synthesize a series of 1,1-bis(3'indolyl)-1-(substituted aromatic)methanes (i.e. C-DIMs) which are also cytotoxic to cancer cells and tumors. Some of the effects of C-DIMs resemble those reported for DIM analogs; however, structure-activity studies with the aromatic ring has resulted in generation of highly unique receptor agonists. For example, p-trifluoromethylphenyl, p-t-butylphenyl and p-biphenyl analogs activate peroxisome proliferator-activated receptor gamma (PPARgamma), and p-methoxyphenyl and p-phenyl compounds activate nerve growth factor-induced-Balpha (NGFI-Balpha, Nur77) orphan nuclear receptor. The effects of C-DIMs on PPARgamma and Nur77 coupled with their receptor-independent activities has resulted in the development of a novel group of multi-targeted anticancer drugs with excellent potential for clinical treatment of cancer.

CXCR4 and CXCL12 down-regulation: a novel mechanism for the chemoprotection of 3,3'-diindolylmethane for breast and ovarian cancers

Cruciferous vegetables are thought to protect against numerous types of cancer. 3,3'-Diindolylmethane (DIM) is an acid-catalyzed product generated during the consumption of cruciferous vegetables and appears to be chemoprotective for breast cancer. The interaction between the chemokine receptor, CXCR4, and its unique ligand, CXCL12, is known to mediate the progression and metastasis of breast and other cancers. Organs to which these cancers metastasize secrete CXCL12, which binds to CXCR4 expressed on the surface of primary cancer cells. This process subsequently stimulates the invasive properties of the cancer cells and attracts them to the preferred organ sites of metastases. We have found that DIM down-regulates both CXCR4 and CXCL12 in MCF-7 and MDA-MB-231 breast cancer cells as well as in BG-1 ovarian cancer cells at the transcriptional level and in an estrogen-independent manner. We demonstrate that the potential of MDA-MB-231 and BG-1 cells for chemotaxis and invasion towards CXCL12, but not towards IL-6 or fetal bovine serum, respectively, is inhibited by DIM. Furthermore, we show that DIM down-regulates CXCR4 under hypoxia and CXCL12 under estradiol-inducing conditions. Our data suggest that one mechanism whereby DIM protects against breast, ovarian, and possibly other cancers is through the repression of CXCR4 and/or CXCL12, thereby lowering the invasive and metastatic potential of these cells.

1,1-bis(3'-indolyl)-1-(p-methoxyphenyl)methane activates Nur77-independent proapoptotic responses in colon cancer cells

1,1-Bis(3'-indolyl)-1-(p-methoxyphenyl)methane (DIM-C-pPhOCH(3)) is a methylene-substituted diindolylmethane (C-DIM) analog that activates the orphan receptor nerve growth factor-induced-Balpha (NGFI-Balpha, Nur77). RNA interference studies with small inhibitory RNA for Nur77 demonstrate that DIM-C-pPhOCH(3) induces Nur77-dependent and -independent apoptosis, and this study has focused on delineating the Nur77-independent proapoptotic pathways induced by the C-DIM analog. DIM-C-pPhOCH(3) induced caspase-dependent apoptosis in RKO colon cancer cells through decreased mitochondrial membrane potential which is accompanied by increased mitochondrial bax/bcl-2 ratios and release of cytochrome c into the cytosol. DIM-C-pPhOCH(3) also induced phosphatidylinositol-3-kinase-dependent activation of early growth response gene-1 which, in turn, induced expression of the proapoptotic nonsteroidal anti-inflammatory drug-activated gene-1 (NAG1) in RKO and SW480 colon cancer cells. Moreover, DIM-C-pPhOCH(3) also induced NAG-1 expression in colon tumors in athymic nude mice bearing RKO cells as xenografts. DIM-C-pPhOCH(3) also activated the extrinsic apoptosis pathway through increased phosphorylation of c-jun N-terminal kinase which, in turn, activated C/EBP homologous transcription factor (CHOP) and death receptor 5 (DR5). Thus, the effectiveness of DIM-C-pPhOCH(3) as a tumor growth inhibitor is through activation of Nur77-dependent and -independent pathways.

1,1-Bis(3'-indolyl)-1-(p-biphenyl)methane inhibits basal-like breast cancer growth in athymic nude mice

Introduction

1,1-Bis (3'-indolyl)-1-(p-biphenyl) methane (CDIM9) has been identified as a new peroxisome proliferator-activated receptor (PPAR)-γ agonist that exhibits both receptor dependent and independent antitumor activities. CDIM9 has not previously been studied with respect to its effects against basal-like breast cancer. Our goal in the present study was to investigate the anti-basal-like breast tumor activity of CDIM9 in vitro and in vivo.

Methods

The effects of CDIM9 on cell protein and DNA syntheses were determined in basal-like breast cancer MDA-MB231 and BT549 cells in vitro. Maximum tolerated dose and dose-limited toxicity were determined in BalB/c mice, and antitumor growth activities were assessed in MDA-MB231 basal-like breast tumor xenografts in athymic nude mice.

Results

CDIM9 exhibited selective cell cytotoxicity and anti-proliferation effects on basal-like breast cancer lines. In MDA-MB231 cell, CDIM9 induced caveolin-1 and p27 expression, which was significantly downregulated by co-treatment with the PPAR-γ antagonist GW9662. Nonsteroidal anti-inflammatory drug-activated gene-1 and activating transcription factor-3 were upregulated by CDIM9 through a PPAR-γ independent pathway. CDIM9 (40 mg/kg daily, intraperitoneally, for 35 days) inhibited the growth of subcutaneous MDA-MB231 tumor xenografts by 87%, and produced a corresponding decrease in proliferation index. Nearly half of the treated mice (46%) had complete durable remissions, confirmed by histology. The growth of an established tumor was inhibited by CDIM9 treatment (64 mg/kg daily, intraperitoneally, for 10 days), with a mean tumor growth inhibition of 67% as compared with controls. CDIM9 induced increases in tumor caveolin-1 and p27 in vivo, which may contribute to its antitumor activity in basal-like breast cancer.

Conclusion

CDIM9 showed potent antiproliferative effects on basal-like breast cancer cell in tissue culture and dramatic growth inhibition in animal models at safe doses. These findings justify further development of this drug for treatment of basal-like breast cancer.

1,1-bis(3'-indolyl)-1-(p-substitutedphenyl)methanes induce apoptosis and inhibit renal cell carcinoma growth

PURPOSE

1,1-Bis(3'-indolyl)-1-(p-substitutedphenyl)methanes [methylene-substituted diindolylmethanes (C-DIM)] containing p-trifluoromethyl, p-t-butyl, and p-phenyl substituents activate peroxisome proliferator-activated receptor gamma (PPARgamma) and inhibit growth of several different cancer cell lines through receptor-dependent and receptor-independent pathways. The purpose of this study is to investigate the anticancer activity of these compounds in renal cell carcinoma.

EXPERIMENTAL DESIGN

The anticancer activity of the p-t-butyl-substituted C-DIM compound (DIM-C-pPhtBu) was investigated in ACHN and 786-0 renal cell carcinoma cell lines and in an orthotopic model for renal carcinogenesis using ACHN cells injected directly into the kidney.

RESULTS

PPARgamma is overexpressed in ACHN cells and barely detectable in 786-0 cells, and treatment with DIM-C-pPhtBu induces proteasome-dependent degradation of cyclin D1 and variable effects on p21 and p27 expression in both cell lines. DIM-C-pPhtBu also induced several common proapoptotic responses in ACHN and 786-0 cells, including increased expression of nonsteroidal anti-inflammatory drug-activated gene-1 and endoplasmic reticulum stress, which activates death receptor 5 and the extrinsic pathway of apoptosis. Activation of these responses was PPARgamma independent. In addition, DIM-C-pPhtBu (40 mg/kg/d) also inhibited tumor growth in an orthotopic mouse model for renal carcinogenesis, and this was accompanied by induction of apoptosis in renal tumors treated with DIM-C-pPhtBu but not in tumors treated with the corn oil vehicle (control).

CONCLUSIONS

DIM-C-pPhtBu and related compounds are cytotoxic to renal cancer cells and activate multiple proapoptotic and growth-inhibitory pathways. The results coupled with in vivo anticancer activity show the potential of DIM-C-pPhtBu and related C-DIMs for clinical treatment of renal adenocarcinoma.

3,3'-Diindolylmethane suppresses the inflammatory response to lipopolysaccharide in murine macrophages

3,3'-Diindolylmethane (DIM), a major acid-condensation product of indole-3-carbinol, has been shown to have multiple anticancer effects in experimental models. Because recurrent or chronic inflammation has been implicated in the development of a variety of human cancers, this study examined the antiinflammatory effects of DIM and the underlying mechanisms using lipopolysaccharide (LPS)-stimulated RAW264.7 murine macrophages. DIM significantly decreased the release of nitric oxide (NO), prostaglandin (PG)E2, tumor necrosis factor alpha, interleukin (IL)-6, and IL-1beta by RAW264.7 cells treated with LPS. DIM inhibited LPS-induced increases in protein levels of inducible NO synthase (iNOS), which were accompanied by decreased iNOS mRNA levels and transcriptional activity. The mRNA levels of phospholipase A2 decreased, whereas neither cyclooxygenases-2 protein nor transcript was altered by DIM. In addition, DIM suppressed LPS-induced nuclear factor-kappaB (NF-kappaB) transcriptional activity, NF-kappaB DNA-binding activity, translocation of p65 (RelA) to the nucleus, and degradation of inhibitor of kappaB alpha. Furthermore, DIM decreased LPS-induced transcriptional activity of activator protein (AP)-1, AP-1 DNA-binding activity, and phosphorylation of stress-activated protein kinase/Jun-N-terminal kinase and c-Jun. We demonstrate that DIM inhibits LPS-induced release of proinflammatory mediators in murine macrophages. Downregulation of NF-kappaB and AP-1 signaling may be one of the mechanisms by which DIM inhibits inflammatory responses.