1,1-Bis(3'-indolyl)-1-(p-substituted phenyl)methanes inhibit colon cancer cell and tumor growth through PPARgamma-dependent and PPARgamma-independent pathways

3,3'-Diindolylmethane and indole-3-carbinol: potential therapeutic molecules for cancer chemoprevention and treatment via regulating cellular signaling pathways

Dietary compounds in cancer prevention have gained significant consideration as a viable method. Indole-3-carbinol (I3C) and 3,3'-diindolylmethane (DIM) are heterocyclic and bioactive chemicals found in cruciferous vegetables like broccoli, cauliflower, cabbage, and brussels sprouts. They are synthesized after glycolysis from the glucosinolate structure. Clinical and preclinical trials have evaluated the pharmacokinetic/pharmacodynamic, effectiveness, antioxidant, cancer-preventing (cervical dysplasia, prostate cancer, breast cancer), and anti-tumor activities of I3C and DIM involved with polyphenolic derivatives created in the digestion showing promising results. However, the exact mechanism by which they exert anti-cancer and apoptosis-inducing properties has yet to be entirely understood. Via this study, we update the existing knowledge of the state of anti-cancer investigation concerning I3C and DIM chemicals. We have also summarized; (i) the recent advancements in the use of I3C/DIM as therapeutic molecules since they represent potentially appealing anti-cancer agents, (ii) the available literature on the I3C and DIM characterization, and the challenges related to pharmacologic properties such as low solubility, and poor bioavailability, (iii) the synthesis and semi-synthetic derivatives, (iv) the mechanism of anti-tumor action in vitro/in vivo, (v) the action in cellular signaling pathways related to the regulation of apoptosis and anoikis as well as the cell cycle progression and cell proliferation such as peroxisome proliferator-activated receptor and PPARγ agonists; SR13668, Akt inhibitor, cyclins regulation, ER-dependent-independent pathways, and their current medical applications, to recognize research opportunities to potentially use these compounds instead chemotherapeutic synthetic drugs.

Peroxisome Proliferator-Activated Receptors and the Hallmarks of Cancer

Peroxisome proliferator-activated receptors (PPARs) function as nuclear transcription factors upon the binding of physiological or pharmacological ligands and heterodimerization with retinoic X receptors. Physiological ligands include fatty acids and fatty-acid-derived compounds with low specificity for the different PPAR subtypes (alpha, beta/delta, and gamma). For each of the PPAR subtypes, specific pharmacological agonists and antagonists, as well as pan-agonists, are available. In agreement with their natural ligands, PPARs are mainly focused on as targets for the treatment of metabolic syndrome and its associated complications. Nevertheless, many publications are available that implicate PPARs in malignancies. In several instances, they are controversial for very similar models. Thus, to better predict the potential use of PPAR modulators for personalized medicine in therapies against malignancies, it seems necessary and timely to review the three PPARs in relation to the didactic concept of cancer hallmark capabilities. We previously described the functions of PPAR beta/delta with respect to the cancer hallmarks and reviewed the implications of all PPARs in angiogenesis. Thus, the current review updates our knowledge on PPAR beta and the hallmarks of cancer and extends the concept to PPAR alpha and PPAR gamma.

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.

Antihyperglycaemic therapies and cancer risk

AIMS

This review is aimed at highlighting the potential mitogenic/tumour growth-promoting or antimitogenic/tumour growth-inhibiting effects of the main antihyperglycaemic drug classes.

METHODS

We review and discuss the most current studies evaluating the association between antidiabetic medications used in clinical practice and malignancies as described so far.

RESULTS

Metformin seems to be the only antidiabetic drug to exert protective effects both on monotherapy and also when combined with other oral antidiabetic drugs or insulins in several site-specific cancers. In contrast, several other drug classes may increase cancer risk. Some reason for concern remains regarding sulphonylureas and also the incretin-based therapies regarding pancreas and thyroid cancers and the sodium glucose cotransporter-2 inhibitors as well as pioglitazone regarding bladder cancer. The majority of meta-analyses suggest that there is no evidence for a causal relationship between insulin glargine and elevated cancer risk, although the studies have been controversially discussed. For α-glucosidase inhibitors and glinides, neutral or only few data upon cancer risk exist.

CONCLUSION

Although the molecular mechanisms are not fully understood, a potential risk of mitogenicity and tumour growth promotion cannot be excluded in case of several antidiabetic drug classes. However, more large-scale, randomized, well-designed clinical studies with especially long follow-up time periods are needed to get reliable answers to these safety issues.

EphA2 targeting pegylated nanocarrier drug delivery system for treatment of lung cancer

PURPOSE

Evaluation of tumor targeting pegylated EphA2 peptide coated nanoparticles (ENDDs) of a novel anticancer agent DIM-C-pPhC6H5 (DIM-P) and Docetaxel (DOC) and investigate its antitumor activity and potential for treatment of lung cancer.

METHODS

Nanoparticles were prepared with DIM-P and DOC (NDDs) using Nano-DeBEE. ENDDs were prepared by conjugating NDDs with 6His-PEG2K-EphA2 peptide and characterized for physicochemical properties, binding assay, cytotoxicity, cellular uptake studies, drug release and pharmacokinetic parameters. Anti-tumor activity of ENDDs was evaluated using a metastatic H1650 and orthotopic A549 tumor models in nude mice and tumor tissue were analyzed by RT-PCR and immunohistochemistry.

RESULTS

Particle size and entrapment efficiency of ENDDs were 197 ± 21 nm and 95 ± 2%. ENDDs showed 32.5 ± 3.5% more cellular uptake than NDDs in tumor cells. ENDDs showed 23 ± 3% and 26 ± 4% more tumor reduction compared to NDDs in metastatic and orthotopic tumor models, respectively. In-vivo imaging studies using the Care stream MX FX Pro system showed (p < 0.001) 40-60 fold higher flux for ENDDs compared to NDDs at tumor site.

CONCLUSIONS

The results emanating from these studies demonstrate anti-cancer potential of DIM-P and the role of ENDDs as effective tumor targeting drug delivery systems for lung cancer treatment.

Targeted regulation of PI3K/Akt/mTOR/NF-κB signaling by indole compounds and their derivatives: mechanistic details and biological implications for cancer therapy

Indole compounds, found in cruciferous vegetables, are potent anti-cancer agents. Studies with indole-3-carbinol (I3C) and its dimeric product, 3,3'-diindolylmethane (DIM) suggest that these compounds have the ability to deregulate multiple cellular signaling pathways, including PI3K/Akt/mTOR signaling pathway. These natural compounds are also effective modulators of downstream transcription factor NF-κB signaling which might help explain their ability to inhibit invasion and angiogenesis, and the reversal of epithelial-to-mesenchymal transition (EMT) phenotype and drug resistance. Signaling through PI3K/Akt/mTOR and NF-κB pathway is increasingly being realized to play important role in EMT through the regulation of novel miRNAs which further validates the importance of this signaling network and its regulations by indole compounds. Here we will review the available literature on the modulation of PI3K/Akt/mTOR/NF-κB signaling by both parental I3C and DIM, as well as their analogs/derivatives, in an attempt to catalog their anticancer activity.

Chemoprevention of skin cancer with 1,1-Bis (3'-indolyl)-1-(aromatic) methane analog through induction of the orphan nuclear receptor, NR4A2 (Nurr1)

Background

The objective of this study was to demonstrate the anti-skin cancer and chemopreventive potential of 1,1-bis(3′-indolyl)-1-(p-chlorophenyl methane) (DIM-D) using an in vitro model.

Methods

In vitro cell cytotoxicity and viability assays were carried out in A431 human epidermoid carcinoma cell line and normal human epidermal keratinocytes (NHEK) respectively by crystal violet staining. Apoptosis induction in A431 cells (DIM-D treated) and NHEK cells pretreated with DIM-D (2 hr) prior to UVB irradiation, were assessed. The accumulation of reactive oxygen species (ROS) in DIM-D pretreated NHEK cells (2 hr) prior to UVB exposure was also determined. Immunocytochemistry and western blot analysis was performed to determine cleaved caspase 3 and DNA damage markers in DIM-D treated A431 cells and in DIM-D pretreated NHEK cells prior to UVB irradiation.

Results

The IC50 values of DIM-D were 68.7±7.3, 48.3±10.1 and 11.5±3.1 μM whilst for Epigallocatechin gallate (EGCG) were 419.1±8.3, 186.1±5.2 and 56.7±3.1 μM for 24, 48 and 72 hr treatments respectively. DIM-D exhibited a significantly (p<0.05) greater induction of DNA fragmentation in A431 cells compared to EGCG with percent cell death of 38.9. In addition, DIM-D induced higher expression in A431 cells compared to EGCG of cleaved caspase 3 (3.0-fold vs. 2.4-fold changes), Nurr1 (2.7-fold vs. 1.7-fold changes) and NFκB (1.3-fold vs. 1.1-fold changes). DIM-D also exhibited chemopreventive activity in UVB-irradiated NHEK cells by significantly (p<0.05) reducing UVB-induced ROS formation and apoptosis compared to EGCG. Additionally, DIM-D induced expression of Nurr1 but reduced expression of 8-OHdG significantly in UVB-irradiated NHEK cells compared to EGCG and UV only.

Conclusion

Our results suggest that DIM-D exhibits Nurr1-dependent transactivation in the induction of apoptosis in A431 cells and it protects NHEK cells against UVB-induced ROS formation and DNA damage.

Ring-substituted analogs of 3,3'-diindolylmethane (DIM) induce apoptosis and necrosis in androgen-dependent and -independent prostate cancer cells

We recently reported that novel ring-substituted analogs of 3,3'-diindolylmethane (ring-DIMs) have anti-androgenic and growth inhibitory effects in androgen-dependent prostate cancer cells. The objectives of this study were to confirm the ability of 4,4'- and 7,7'-dibromo- and dichloro-substituted ring-DIMs to inhibit androgen-stimulated proliferation of androgen-dependent LNCaP human prostate cancer cells using a non-invasive, real-time monitoring technique. In addition, their ability to induce apoptotic and necrotic cell death in androgen-dependent as well as -independent (PC-3) prostate cancer cells was studied. Prostate cancer cells were treated with increasing concentrations of DIM and ring-DIMs (0.3-30 μM) and effects on cell proliferation were measured in real-time using an xCELLigence cellular analysis system. Chromatin condensation and loss of membrane integrity were determined by Hoechst and propidium iodide staining, respectively. Apoptotic protein markers were measured by immunoblotting and activation of caspases determined using selective fluorogenic substrates. Intra- and extracellular concentrations of DIM and ring-DIMs were assessed by electrospray ionization tandem mass spectrometry. Ring-DIMs inhibited androgen-stimulated LNCaP cell proliferation and induced apoptosis and necrosis in LNCaP and PC-3 cells with 2-4 fold greater potencies than DIM. DIM and the ring-DIMs increased caspases -3, -8 and -9 activity, elevated expression of Fas, FasL, DR4 and DR5 protein, and induced PARP cleavage in both cell lines. The cytotoxicity of the most potent ring-DIM, 4,4'-dibromoDIM, but not the other compounds was decreased by an inhibitor of caspase -3. The 4,4'-dibromoDIM was primarily found in the extracellular medium, whereas all other compounds were present to a much larger extent in the cell. In conclusion, ring-DIMs inhibited prostate cancer cell growth and induced cell death in LNCaP and PC-3 cells with greater potencies than DIM; they also structure-dependently activated different cell death pathways suggesting that these compounds have clinical potential as chemopreventive and chemotherapeutic agents in prostate cancer, regardless of hormone-dependency.

Peroxisome proliferator-activated receptor gamma overexpression suppresses proliferation of human colon cancer cells

Peroxisome proliferator-activated receptor gamma (PPARγ) plays an important role in the differentiation of intestinal cells and tissues. Our previous reports indicate that PPARγ is expressed at considerable levels in human colon cancer cells. This suggests that PPARγ expression may be an important factor for cell growth regulation in colon cancer. In this study, we investigated PPARγ expression in 4 human colon cancer cell lines, HT-29, LOVO, DLD-1, and Caco-2. Real-time polymerase chain reaction (PCR) and Western blot analysis revealed that the relative levels of PPARγ mRNA and protein in these cells were in the order HT-29>LOVO>Caco-2>DLD-1. We also found that PPARγ overexpression promoted cell growth inhibition in PPARγ lower-expressing cell lines (Caco-2 and DLD-1), but not in higher-expressing cells (HT-29 and LOVO). We observed a correlation between the level of PPARγ expression and the cells' sensitivity for proliferation.

Rosiglitazone and AS601245 decrease cell adhesion and migration through modulation of specific gene expression in human colon cancer cells

PPARs are nuclear receptors activated by ligands. Activation of PPARγ leads to a reduction of adhesion and motility in some cancer models. PPARγ transcriptional activity can be negatively regulated by JNK-mediated phosphorylation. We postulated that the use of agents able to inhibit JNK activity could increase the effectiveness of PPARγ ligands. We analysed the effects of rosiglitazone (PPARγ ligand) and AS601245 (a selective JNK inhibitor) alone or in association on adhesion and migration of CaCo-2, HT29, and SW480 human colon cancer cells and investigated, through microarray analysis, the genes involved in these processes. Cell adhesion and migration was strongly inhibited by rosiglitazone and AS601245. Combined treatment with the two compounds resulted in a greater reduction of the adhesion and migration capacity. Affymetrix analysis in CaCo-2 cells revealed that some genes which were highly modulated by the combined treatment could be involved in these biological responses. Rosiglitazone, AS601245 and combined treatment down-regulated the expression of fibrinogen chains in all three cell lines. Moreover, rosiglitazone, alone or in association with AS601245, caused a decrease in the fibrinogen release. ARHGEF7/β-PIX gene was highly down-regulated by combined treatment, and western blot analysis revealed that β-PIX protein is down-modulated in CaCo-2, HT29 and SW480 cells, also. Transfection of cells with β-PIX gene completely abrogated the inhibitory effect on cell migration, determined by rosiglitazone, AS601245 and combined treatment. Results demonstrated that β-PIX protein is involved in the inhibition of cell migration and sustaining the positive interaction between PPARγ ligands and anti-inflammatory agents in humans.

Association of thiazolidinediones with liver cancer and colorectal cancer in type 2 diabetes mellitus

The objective of this nationwide case-control study was to evaluate the risk of specific malignancy in diabetic patients who received thiazolidinediones (TZDs). A total of 606,583 type 2 diabetic patients, age 30 years and above, without a history of cancer were identified from the Taiwan National Health Insurance claims database during the period between January 1 2000 and December 31 2000. As of December 31 2007, patients with incident cancer of liver, colorectal, lung, and urinary bladder were included as cases and up to four age- and sex-matched controls were selected by risk-set sampling. Logistic regression models were applied to estimate the odds ratio (OR) and 95% confidence interval (CI) between TZDs and cancer incidence. A total of 10,741 liver cancer cases, 7,200 colorectal cancer cases, and 70,559 diabetic controls were included. A significantly lower risk of liver cancer incidence was found for any use of rosiglitazone (OR: 0.73, 95% CI: 0.65-0.81) or pioglitazone (OR: 0.83, 95% CI: 0.72-0.95), respectively. The protective effects were stronger for higher cumulative dosage and longer duration. For colorectal cancer, rosiglitazone, but not pioglitazone, was associated with a significantly reduced risk (OR: 0.86; 95% CI: 0.76-0.96). TZDs were not associated with lung and bladder cancer incidence, although a potential increased risk for bladder cancer with pioglitazone use ≥3 years could not be excluded (OR: 1.56; 95% CI: 0.51-4.74).

CONCLUSION

The use of pioglitazone and rosiglitazone is associated with a decreased liver cancer incidence in diabetic patients. The effects on occurrence of specific cancer types may be different for pioglitazone and rosiglitazone.

Synergistic anti-tumor activity of isochaihulactone and paclitaxel on human lung cancer cells

Drug resistance frequently develops in tumors during chemotherapy. Therefore, to improve the clinical outcome, more effective and tolerable combination treatment strategies are needed. Here, we show that isochaihulactone (K8) enhanced paclitaxel-induced apoptotic death in human lung cancer cells, and the enhancing effect was related to increased NSAID-activated gene-1 (NAG-1) expression. CalcuSyn software was used to evaluate the synergistic interaction of K8 and paclitaxel on human lung cancer cells; the synergistic effect of K8 in combination with paclitaxel was increased more than either of these drugs alone. Furthermore, the activity of ERK1/2 was enhanced by the combination of K8 and paclitaxel, and an ERK1/2 inhibitor dramatically inhibited NAG-1 expression in human lung cancer cells. Therefore, this synergistic apoptotic effect in human lung cancer cells may be directly associated with K8-induced NAG-1 expression through ERK1/2 activation. Moreover, over-expression of NAG-1 enhanced K8/paclitaxel-induced apoptosis in human lung cancer cells. In addition, treatment of nude mice with K8 combined with paclitaxel induced phospho-ERK1/2 and NAG-1 expression in vivo. Targeting of NAG-1 signaling could enhance therapeutic efficacy in lung cancer. Our results reveal that activation of NAG-1 by K8 enhanced the therapeutic efficacy of paclitaxel in human lung cancer cells via the ERK1/2 signaling pathway.

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.

1,1-Bis(3'-indolyl)-1-(p-substituted phenyl)methanes induce autophagic cell death in estrogen receptor negative breast cancer

BACKGROUND

A novel series of methylene-substituted DIMs (C-DIMs), namely 1,1-bis(3'-indolyl)-1-(p-substituted phenyl)methanes containing t-butyl (DIM-C-pPhtBu) and phenyl (DIM-C-pPhC6H5) groups inhibit proliferation of invasive estrogen receptor-negative MDA-MB-231 and MDA-MB-453 human breast cancer cell lines with IC50 values between 1-5 uM. The main purpose of this study was to investigate the pathways of C-DIM-induced cell death.

METHODS

The effects of the C-DIMs on apoptotic, necrotic and autophagic cell death were determined using caspase inhibitors, measurement of lactate dehydrogenase release, and several markers of autophagy including Beclin and light chain associated protein 3 expression (LC3).

RESULTS

The C-DIM compounds did not induce apoptosis and only DIM-C-pPhCF3 exhibited necrotic effects. However, treatment of MDA-MB-231 and MDA-MB-453 cells with C-DIMs resulted in accumulation of LC3-II compared to LC3-I protein, a characteristic marker of autophagy, and transient transfection of green fluorescent protein-LC3 also revealed that treatment with C-DIMs induced a redistribution of LC3 to autophagosomes after C-DIM treatment. In addition, the autofluorescent drug monodansylcadaverine (MDC), a specific autophagolysosome marker, accumulated in vacuoles after C-DIM treatment, and western blot analysis of lysates from cells treated with C-DIMs showed that the Beclin 1/Bcl-2 protein ratio increased.

CONCLUSION

The results suggest that C-DIM compounds may represent a new mechanism-based agent for treating drug-resistant ER-negative breast tumors through induction of autophagy.

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.

1,1-Bis(3'-indolyl)-1-(p-bromophenyl)methane and related compounds repress survivin and decrease gamma-radiation-induced survivin in colon and pancreatic cancer cells

1,1-Bis(3'-indolyl)-1-(p-bromophenyl)methane (DIM-C-pPhBr) and the 2,2'-dimethyl analog (2,2'-diMeDIM-C-pPhBr) inhibit proliferation and induce apoptosis in SW480 colon and Panc28 pancreatic cancer cells. In this study, treatment with 10-20 microM concentrations of these compounds for 24 h induced cleaved PARP and decreased survivin protein and mRNA expression in both cell lines. However, results of time course studies show that DIM-C-pPhBr and 2,2'-diMeDIM-C-pPhBr decrease survivin protein within 2 h after treatment, whereas survivin mRNA levels were decreased only at later time-points indicating activation of transcription-independent and -dependent pathways for downregulation of survivin. In addition, we also observed that gamma-radiation inhibited pancreatic and colon cancer cell growth and this was associated with enhanced expression of survivin after 24 (SW480) or 24 and 48 h (Panc28) and correlated with previous studies on the role of survivin in radiation-resistance. However, in cells co-treated with gamma-radiation plus DIM-C-pPhBr or 2,2'-diMeDIM-C-pPhBr, induction of survivin by gamma-radiation was inhibited after co-treatment with both compounds, suggesting applications for these drugs in combination cancer chemotherapy with gamma-radiation.

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.

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.

Ciglitazone induces apoptosis via activation of p38 MAPK and AIF nuclear translocation mediated by reactive oxygen species and Ca(2+) in opossum kidney cells

We have previously demonstrated that the synthetic peroxisome proliferator-activated receptor-gamma (PPARgamma) agonist ciglitazone induces apoptosis accompanied by activation of p38 mitogen-activated protein kinase (MAPK) and nuclear translocation of apoptosis inducing factor (AIF) in opossum kidney (OK) renal epithelial cells. However, the precise mechanism by which ciglitazone induces activation of p38 MAPK and the role of AIF in the induction of the apoptosis are not defined. This study was therefore undertaken to determine whether the roles of reactive oxygen species (ROS) generation and intracellular Ca(2+) in the ciglitazone-induced activation of p38 MAPK and whether AIF nuclear translocation is responsible for the ciglitazone-induced apoptosis in OK renal epithelial cells. Ciglitazone caused generation of ROS and an increase in intracellular Ca(2+). Ciglitazone-induced cell death was reduced by the antioxidant Trolox, the Ca(2+) chelator EGTA, and the store-operated Ca(2+) channels (SOCC) blocker lanthanum chloride (La(3+)), indicating involvement of ROS and Ca(2+) in the ciglitazone-induced cell death. Ciglitazone-induced intracellular Ca(2+) increase was decreased by Trolox, while ROS generation was not affected by EGTA and La(3+), suggesting that ROS generation promote the increase of intracellular Ca(2+). Transfection of small interfering RNA (siRNA) of p38 MAPK or vector expressing microRNA (miRNA) of AIF prevented the ciglitazone-induced cell death. Activation of p38 MAPK, mitochondrial membrane depolarization, and AIF nuclear translocation induced by ciglitazone were inhibited by Trolox, EGTA and La(3+). Taken together, these results suggest that ROS-dependent intracellular Ca(2+) increase is responsible for activation of p38 MAPK and nuclear translocation of AIF by ciglitazone.

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.

Peroxisome proliferator-activated receptor ligand MCC-555 suppresses intestinal polyps in ApcMin/+ mice via extracellular signal-regulated kinase and peroxisome proliferator-activated receptor-dependent pathways

A large body of studies has suggested that peroxisome proliferator-activated receptor gamma (PPARgamma) ligands, such as thiazolidinedione, are potent candidates for chemopreventive agents. MCC-555 is a PPARgamma/alpha dual agonist and has been shown previously to induce apoptosis in vitro; however, the molecular mechanisms by which MCC-555 affects antitumorigenesis in vivo are poorly understood. In this study, we explored the antitumorigenic effects of MCC-555 both in cell culture and in Apc-deficient mice, an animal model for human familial adenomatous polyposis. MCC-555 increased MUC2 expression in colorectal and lung cancer cells, and treatment with the PPARgamma antagonist GW9662 revealed that MUC2 induction by MCC-555 was mediated in a PPARgamma-dependent manner. Moreover, MCC-555 increased transcriptional activity of human and mouse MUC2 promoters. Subsequently, treatment with MCC-555 (30 mg/kg/d) for 4 weeks reduced the number of small intestinal polyps to 54.8% of that in control mice. In agreement with in vitro studies, enhanced Muc2 expression was observed in the small intestinal tumors of Min mice treated with MCC-555, suggesting that MUC2 expression may be associated at least in part with the antitumorigenic action of MCC-555. In addition, highly phosphorylated extracellular signal-regulated kinase (ERK) was found in the intestinal tumors of MCC-555-treated Min mice, and inhibition of the ERK pathway by a specific inhibitor markedly suppressed MCC-555-induced Muc2 expression in vitro. Overall, these results indicate that MCC-555 has a potent tumor suppressor activity in intestinal tumorigenesis, likely involving MUC2 up-regulation by ERK and PPARgamma pathways.

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.

An endogenous prostaglandin enhances environmental phthalate-induced apoptosis in bone marrow B cells: activation of distinct but overlapping pathways

Phthalate esters are ubiquitous environmental contaminants that are produced for a variety of common industrial and commercial purposes. We have shown that mono-(2-ethylhexyl) phthalate (MEHP), the toxic metabolite of di-(2-ethylhexyl) phthalate, induces bone marrow B cell apoptosis that is enhanced in the presence of the endogenous prostaglandin 15-deoxy-Delta((12, 14))-PGJ(2) (15d-PGJ(2)). Here, studies were performed to determine whether 15d-PGJ(2)-mediated enhancement of MEHP-induced apoptosis represents activation of an overlapping or complementary apoptosis pathway. MEHP and 15d-PGJ(2) induced significant apoptosis within 8 and 5 h, respectively, in a pro/pre-B cell line and acted cooperatively to induce apoptosis in primary pro-B cells. Apoptosis induced with each chemical was accompanied by activation of a combination of initiator caspases (caspases-2, -8, and -9) and executed by caspase-3. Apoptosis induced with MEHP and 15d-PGJ(2) was reduced in APAF1 null primary pro-B cells and accompanied by alteration of mitochondrial membranes, albeit with different kinetics, indicating an intrinsically activated apoptosis pathway. Significant Bax translocation to the mitochondria supports its role in initiating release of cytochrome c. Both chemicals induced Bid cleavage, a result consistent with a truncated Bid-mediated release of cytochrome c in an apoptosis amplification feedback loop; however, significantly more Bid was cleaved following 15d-PGJ(2) treatment, potentially differentiating the two pathways. Indeed, Bid cleavage and cytochrome c release following 15d-PGJ(2) but not MEHP treatment was profoundly inhibited by Z-VAD-FMK, suggesting that 15d-PGJ(2) activates apoptosis via two pathways, Bax mobilization and protease-dependent Bid cleavage. Thus, endogenous 15d-PGJ(2)-mediated enhancement of environmental chemical-induced apoptosis represents activation of an overlapping but distinct signaling pathway.

1,1-bis(3'-indolyl)-1-(p-substituted phenyl)methanes decrease mitochondrial membrane potential and induce apoptosis in endometrial and other cancer cell lines

1,1-Bis(3'-indolyl)-1-(p-substituted phenyl)methanes, containing p-t-butyl (DIM-C-pPhtBu) and phenyl (DIM-C-pPhC(6)H(5)) substituents, are peroxisome proliferator-activated receptor gamma (PPARgamma) agonists; however, DIM-C-pPhtBu-induced growth inhibition and cell death in human HEC1A endometrial cancer cells is PPARgamma-independent. DIM-C-pPhtBu decreased mitochondrial membrane potential (MMP) and promoted the release of cytochrome c and caspase activation and nuclear uptake of endonuclease G leading to apoptosis of HEC1A cells. DIM-C-pPhtBu specifically targeted the mitochondrial permeability transition pore complex (PTPC) because the DIM-C-pPhtBu-induced pro-apoptotic responses were inhibited by atractyloside (Atra), a compound that specifically interacts with the inner mitochondrial membrane adenine nucleotide transport (ANT) proteins. At the dose of Atra used in this study (300 microM), this compound alone did not alter the PTPC but inhibited the mitochondriotoxic effects of DIM-C-pPhtBu. DIM-C-pPhtBu/DIM-C-pPhC(6)H(5) and Atra also differentially affected the ability of eosin-5-maleimide (EMA) to alkylate Cys160 in the ANT protein and Atra, but not DIM-C-pPhtBu, inhibited the exchange of ATP/ADP in isolated mitochondria suggesting that these pharmacophores act on different sites on the ANT protein. Results of this study show that the receptor-independent proapoptotic activity of DIM-C-pPhtBu and DIM-C-pPhC(6)H(5) were related to novel mitochondriotoxic activities involving inner mitochondrial ANT proteins.

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.

Loss of XIAP sensitizes colon cancer cells to PPARgamma independent antitumor effects of troglitazone and 15-PGJ2

We investigated whether the anticancer effect of a combination of XIAP down-regulation and PPAR gamma activation on colon cancer is PPARgamma receptor dependent. HCT116-XIAP(+/+) cells and HCT116-XIAP(-/-) cells were treated with troglitazone or 15-deoxy-Delta(12,14)-prostaglandin J2 (15-PGJ2) with or without prior exposure to PPARgamma inhibitor GW9662. Cell proliferation and apoptosis was evaluated. Athymic mice carrying HCT116-XIAP(-/-) cells-derived tumors were treated with troglitazone in the presence or absence of GW9662. Inhibition of cell proliferation and induction of apoptosis by troglitazone and 15-PGJ2 were more prominent in HCT116-XIAP(-/-) cells. PPARgamma ligand-induced growth inhibition, apoptosis, caspase and PARP cleavage could not be blocked by GW9662. Troglitazone significantly retarded growth of xenograft tumors and this effect was not blocked by GW9662. Marked apoptosis and an up-regulation of E-cadherin were observed in xenograft tumor tissues, and GW9662 did not affect these effects. Thus, a combination of XIAP down-regulation and PPARgamma ligands exert a significant anticancer effect in colon cancer via a PPARgamma independent pathway.

1,1-Bis(3'-indolyl)-1-(p-substituted phenyl)methanes inhibit colon cancer cell and tumor growth through activation of c-jun N-terminal kinase

1,1-Bis(3'-indolyl)-1-(p-substituted phenyl)methanes (C-DIMs) activate the orphan receptors peroxisome proliferator-activated receptor gamma (PPARgamma) and Nur77 and induce receptor-dependent and -independent apoptotic pathways in colon and other cancer cells. Structure-activity studies show that the p-bromo (DIM-C-pPhBr) and p-fluoro (DIM-C-pPhF) analogs, which exhibit minimal activation of Nur77 and PPARgamma, induce expression of CCAAT/enhancer-binding protein homologous protein (CHOP/GADD153) in colon cancer cells. Moreover, among a series of bromo and fluoro C-DIM analogs, their induction of CHOP was dependent on the position of the phenyl substituents (para >/= meta >/= ortho) and required a free indole group. DIM-C-pPhBr and DIM-C-pPhF not only induced CHOP but also activated death receptor 5 (CHOP dependent), cleavage of caspase 8 and poly (ADP ribose) polymerase (PARP) that is consistent with activation of the extrinsic pathway of apoptosis. These responses were associated with the activation of c-jun N-terminal kinase (JNK) pathway since inhibition of JNK inhibited induction of the extrinsic apoptotic pathway by these C-DIMs. However, in contrast to classical inducers of endoplasmic reticulum (ER) stress such as tunicamycin and thapsigargin, the C-DIM compounds did not induce glucose-related protein 78 that is a marker of ER stress. Proapoptotic and anticarcinogenic effects were also observed in athymic nude mice bearing RKO cell xenografts and treated with 30 mg/kg/day DIM-C-pPhBr and this was accompanied by increased JNK phosphorylation in the tumors. Thus, the anticarcinogenic activity of DIM-C-pPhBr in colon cancer cells and tumors is related to a novel ER stress-independent activation of JNK.

The peroxisome proliferator-activated receptor-gamma agonist 1,1-bis(3'-indolyl)-1-(p-trifluoromethylphenyl)methane suppresses manganese-induced production of nitric oxide in astrocytes and inhibits apoptosis in cocultured PC12 cells

Reactive astrogliosis is a prominent neuropathologic feature of manganism, a neurodegenerative disorder caused by excessive accumulation of manganese (Mn) in the basal ganglia. Activation of astrocytes has been linked to neuronal injury in manganism resulting from overproduction of inflammatory mediators, including tumor necrosis factor-alpha (TNFalpha), interferon-gamma (IFNgamma), interleukin-1beta (IL-1beta), and nitric oxide (NO), but the signaling mechanisms by which Mn regulates these factors remain poorly understood. We previously reported that Mn enhances production of NO in activated astrocytes that promotes apoptosis in cocultured neuronal cells by a mechanism involving the transcription factor nuclear factor-kappaB (NF-kappaB) (Liu et al., 2005). Because NF-kappaB-dependent expression of inducible nitric oxide synthase (NOS2) can be antagonized by the nuclear orphan receptor peroxisome proliferator-activated receptor-gamma (PPARgamma), we postulated that a novel agonist of this receptor, 1,1-bis(3'-indolyl)-1-(p-trifluoromethylphenyl)methane (cDIM1), would suppress expression of NOS2 in astrocytes and protect cocultured neuronal cells from apoptosis. Submicromolar concentrations of cDIM1 potently suppressed production of NO and expression of NOS2 in cultured astrocytes exposed to Mn and IFNgamma/TNFalpha and prevented apoptosis in cocultures of differentiated PC12 cells, but this neuroprotective effect was lost in the absence of astrocytes. By using fluorescence reporter and chromatin immunoprecipitation (ChIP) assays, we found that cDIM1 prevented activation of NF-kappaB in astrocytes by a mechanism involving stabilization of the nuclear corepressor 2 (NCoR2) on the proximal NF-kappaB binding site of the NOS2 promoter. These data suggest that PPARgamma may be an effective target for limiting inflammatory activation of astrocytes during neurologic injury.

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.

A Role for the PPARgamma in Cancer Therapy

In 1997, the first published reports highlighted PPARgamma as a novel cancer therapeutic target regulating differentiation of cancer cells. A subsequent flurry of papers described these activities more widely and fuelled further enthusiasm for differentiation therapy, as the ligands for the PPARgamma were seen as well tolerated and in several cases well-established in other therapeutic contexts. This initial enthusiasm and promise was somewhat tempered by contradictory findings in several murine cancer models and equivocal trial findings. As more understanding has emerged in recent years, a renaissance has occurred in targeting PPARgamma within the context of either chemoprevention or chemotherapy. This clarity has arisen in part through a clearer understanding of PPARgamma biology, how the receptor interacts with other proteins and signaling events, and the mechanisms that modulate its transcriptional actions. Equally greater translational understanding of this target has arisen from a clearer understanding of in vivo murine cancer models. Clinical exploitation will most likely require precise and quantifiable description of PPARgamma actions, and resolution of which targets are the most beneficial to target combined with an understanding of the mechanisms that limits its anticancer effectiveness.

Activation of Nonsteroidal Anti-Inflammatory Drug-Activated Gene-1 via Extracellular Signal-Regulated Kinase 1/2 Mitogen-Activated Protein Kinase Revealed a Isochaihulactone-Triggered Apoptotic Pathway in Human Lung Cancer A549 Cells

The novel lignan isochaihulactone inhibits cell proliferation and is an effective inducer of apoptosis in a variety of carcinoma cell lines. To determine the mechanisms underlying these effects, we examined isochaihulactone-induced changes in gene expression using oligodeoxynucleotide-based microarray screening of a human lung carcinoma cell line, A549. Isochaihulactone-inducible genes included the early growth response gene-1 (EGR-1) and nonsteroidal anti-inflammatory drug-activated gene (NAG-1). Isochaihulactone increased EGR-1 and then NAG-1 mRNA and protein expression. Pure isochaihulactone induced phosphorylation of extracellular signal-regulated kinase (ERK) 1/2. Isochaihulactone-induced increases in EGR-1 and NAG-1 expression were reduced by the mitogen-activated protein kinase kinase 1/2 inhibitor 2'-amino-3'-methoxyflavone (PD98059), and this effect was not blocked by the phosphatidylinositol 3-kinase/protein kinase B pathway inhibitor 2-(4-morpholinyl)-8-phenyl-1(4H)-benzopyran-4-one hydrochloride (LY294002). Inhibition of isochaihulactone-induced NAG-1 expression by EGR-1 small interfering RNA blocked isochaihulactone-induced apoptosis in A549 cells, suggesting that induction of EGR-1 expression decreases survival of A549 cells. RNA interference using double-stranded RNA specific for NAG-1 also inhibited isochaihulactone-induced apoptosis, and cells transfected to increased NAG-1 expression had a greater apoptotic response to isochaihulactone and reduced colony formation efficiency. In addition, treatment of nude mice with isochaihulactone increased the in vivo NAG-1 expression as examined by immunohistochemistry from tumor biopsy. Isochaihulactone treatment increased the luciferase activity of NAG-1 in A549 cells transfected with the NAG-1 promoter construct. This induction increased expression of NAG-1 that was p53-independent and Sp1-dependent. Our findings suggest that NAG-1 expression is up-regulated by isochaihulactone through an ERK-dependent pathway involving the activation of EGR-1.

1,1-Bis(3′-indolyl)-1-(p-substituted phenyl)methanes inhibit proliferation of estrogen receptor-negative breast cancer cells by activation of multiple pathways

1,1-Bis(3'-indolyl)-1-(p-substituted phenyl)methanes containing para-trifluoromethyl (DIM-C-pPhCF(3)), t-butyl (DIM-C-pPhtBu), and phenyl (DIM-C-pPhC(6)H(5)) groups are methylene-substituted diindolylmetyhanes (C-DIMs) that activate peroxisome proliferator-activated receptor gamma (PPARgamma) in estrogen receptor alpha-negative MDA-MB-231 and MDA-MB-453 breast cancer cells. C-DIMs inhibit breast cancer cell proliferation; however, inhibition of G(0)/G(1) to S phase progression and cyclin D1 downregulation was observed in MDA-MB-231 but not MDA-MB-453 cells. Nonsteroidal anti-inflammatory drug-activated gene 1 (NAG-1), a transforming growth factor beta-like peptide, was also induced by these compounds, and the response was dependent on cell-context dependent activation of kinase pathways. However, inhibition of cell growth, induction of NAG-1 and activation of kinases by C-DIMs were not inhibited by PPARgamma antagonists. Despite the induction of NAG-1 and downregulation of the antiapoptotic protein survivin by C-DIMs in both MDA-MB-231 and MDA-MB-453 cells, apoptotic cell death was not observed. Nevertheless, the cytotoxicity of C-DIMs in vitro was complemented by inhibition of tumor growth in athymic nude mice bearing MDA-MB-231 cells as xenografts and treated with DIM-C-pPhC(6)H(5) (40 mg/kg/day). The growth inhibition of tumors derived from highly aggressive MDA-MB-231 cells suggests a potential role for the C-DIM compounds in the clinical treatment of ER-negative breast cancer.

Nur77 agonists induce proapoptotic genes and responses in colon cancer cells through nuclear receptor-dependent and nuclear receptor-independent pathways

Nerve growth factor-induced Balpha (NGFI-Balpha, Nur77) is an orphan nuclear receptor with no known endogenous ligands; however, recent studies on a series of methylene-substituted diindolylmethanes (C-DIM) have identified 1,1-bis(3'-indolyl)-1-(phenyl)methane (DIM-C-Ph) and 1,1-bis(3'-indolyl)-1-(p-anisyl)methane (DIM-C-pPhOCH3) as Nur77 agonists. Nur77 is expressed in several colon cancer cell lines (RKO, SW480, HCT-116, HT-29, and HCT-15), and we also observed by immunostaining that Nur77 was overexpressed in colon tumors compared with normal colon tissue. DIM-C-Ph and DIM-C-pPhOCH3 decreased survival and induced apoptosis in RKO colon cancer cells, and this was accompanied by induction of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) protein. The induction of apoptosis and TRAIL by DIM-C-pPhOCH3 was significantly inhibited by a small inhibitory RNA for Nur77 (iNur77); however, it was evident from RNA interference studies that DIM-C-pPhOCH3 also induced Nur77-independent apoptosis. Analysis of DIM-C-pPhOCH3-induced gene expression using microarrays identified several proapoptotic genes, and analysis by reverse transcription-PCR in the presence or absence of iNur77 showed that induction of programmed cell death gene 1 was Nur77 dependent, whereas induction of cystathionase and activating transcription factor 3 was Nur77 independent. DIM-C-pPhOCH3 (25 mg/kg/d) also inhibited tumor growth in athymic nude mice bearing RKO cell xenografts. These results show that Nur77-active C-DIM compounds represent a new class of anti-colon cancer drugs that act through receptor-dependent and receptor-independent pathways.

1,1-Bis(3'-indolyl)-1-(p-substituted phenyl)methanes inhibit ovarian cancer cell growth through peroxisome proliferator-activated receptor-dependent and independent pathways

1,1-Bis(3'-indolyl)-1-(p-t-butylphenyl)methane (DIM-C-pPhtBu) is a peroxisome proliferator-activated receptor gamma (PPARgamma) agonist, and treatment of SKOV3 ovarian cancer cells with this compound (5 micromol/L) inhibits cell proliferation, whereas up to 15 micromol/L rosiglitazone had no effect on cell growth. DIM-C-pPhtBu also inhibits G0-G1 to S phase cell cycle progression and this is linked, in part, to PPARgamma-dependent induction of the cyclin-dependent kinase inhibitor p21. DIM-C-pPhtBu induces PPARgamma-independent down-regulation of cyclin D1 and we therefore further investigated activation of receptor-independent pathways. DIM-C-pPhtBu also induced apoptosis in SKOV3 cells and this was related to induction of glucose-related protein 78, which is typically up-regulated as part of the unfolded protein response during endoplasmic reticulum (ER) stress. Activation of ER stress was also observed in other ovarian cancer cell lines treated with DIM-C-pPhtBu. In addition, DIM-C-pPhtBu induced CCAAT/enhancer binding protein homologous protein through both ER stress and c-jun NH2-terminal kinase-dependent pathways, and CCAAT/enhancer binding protein homologous protein activated death receptor 5 and the extrinsic pathway of apoptosis. These results show that DIM-C-pPhtBu inhibits growth and induces apoptosis in ovarian cancer cells through both PPARgamma-dependent and PPARgamma-independent pathways, and this complex mechanism of action will be advantageous for future clinical development of these compounds for treatment of ovarian cancer.

Effect of ligand troglitazone on peroxisome proliferator-activated receptor γ expression and cellular growth in human colon cancer cells

AIM: To investigate the effect of troglitazone on pe-roxisome proliferator-activated receptor γ (PPARγ) expression and cellular growth in human colon cancer HCT-116 and HCT-15 cells and to explore the related molecular mechanism.

METHODS: Human colon cancer HCT-116 and HCT-15 cells cultured in vitro were treated with troglitazone. Reverse transcription-polymerase chain reaction (RT-PCR) and Western blot were employed to detect the effect of troglitazone on PPARγ expression. The proliferative activity was determined by MTT assay, cell cycle and apoptosis were detected by flow cytometry. Apoptosis-related genes, cell cycle regulatory genes and p53 were examined by RT-PCR and Western blot respectively.

RESULTS: The expression of PPARγ in colon cancer HCT-116 and HCT-15 cells was up-regulated by troglitazone. Troglitazone inhibited proliferation, induced apoptosis and cell cycle G1 arrest in colon cancer cells. Troglitazone induced p53 expression in HCT-116 cells, but not in HCT-15 cells. The down-regulation of survivin and bcl-2 was found in both cell lines and up-regulation of bax was found only in HCT-116 cells, being consistent with growth inhibition in HCT-116 cells but not in HCT-15 cells. Troglitazone increased expression of p21^WAF1/CIP1 (p21), p27^KIP1 (p27) and reduced cyclin D1 in HCT-116 cells while only a minor decrease of cyclin D1 was found in HCT-15 cells.

CONCLUSION: Troglitazone is an inductor of PPARγ in colon cancer cells and inhibits PPARγ-dependently proliferation, which may attribute to cell cycle G1 arrest and apoptosis in colon cancer cells. Troglitazone may induce p53-independent apoptosis and p53-dependent expression of p21 and p27. Depending on cell background, different activation pathways may exist in colon cancer cells.

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

1,1-bis(3'-indolyl)-1-(p-substitutedphenyl)methanes (C-DIMs) containing para-trifluoromethyl, t-butyl, and phenyl groups are a novel class of peroxisome proliferator-activated receptor (PPAR)gamma agonists. In LNCaP prostate cancer cells, these compounds induce PPARgamma-dependent transactivation, inhibit cell proliferation, and induce apoptosis. In addition, these PPARgamma agonists modulate a number of antiproliferative and proapoptotic responses, including induction of p27, activating transcription factor 3, and nonsteroidal anti-inflammatory drug-activated gene-1 and down-regulation of cyclin D1 and caveolin-1. Moreover, the PPARgamma antagonist 2-chloro-5-nitrobenzanilide (GW9662) does not inhibit these effects. The C-DIM compounds also abrogate androgen receptor (AR)-mediated signaling and decrease prostate-specific antigen (PSA) and AR protein expression, and these responses were PPARgamma-independent. The effects of C-DIMs on AR and PSA were due to decreased AR and PSA mRNA expression in LNCaP cells. Thus, this series of methylene-substituted diindolylmethane derivatives simultaneously activate multiple pathways in LNCaP cells, including ablation of androgen-responsiveness and down-regulation of caveolin-1. Both of these responses are associated with activation of proapoptotic pathways in this cell line.