Cyano Enone Research Articles

Acetylenic tricyclic bis-(cyano enone) interacts with Cys 374 of actin, a residue necessary for stress fiber formation and cell migration

The migratory and invasive potential of tumour cells relies on the actin cytoskeleton. We previously demonstrated that the tricyclic compound, TBE-31, inhibits actin polymerization and here we further examine the precise interaction between TBE-31 and actin. We demonstrate that iodoacetamide, a cysteine (Cys) alkylating agent, interferes with the ability of TBE-31 to interact with actin. In addition, in silico analysis identified Cys 217, Cys 272, Cys 285 and Cys 374 as potential binding sites for TBE-31. Using mass spectrometry analysis, we determined that TBE-31 associates with actin with a stoichiometric ratio of 1:1. We mutated the identified cysteines of actin to alanine and performed a pull-down analysis with a biotin labeled TBE-31 and demonstrated that by mutating Cys 374 to alanine the association between TBE-31 and actin was significantly reduced, suggesting that TBE-31 binds to Cys 374. A characterization of the NIH3T3 cells overexpressing eGFP-actin-C374A showed reduced stress fiber formation, suggesting Cys 374 is necessary for efficient incorporation into filamentous actin. Furthermore, migration of eGFP-Actin-WT expressing cells were observed to be inhibited by TBE-31, however fewer eGFP-Actin-C374A expressing cells were observed to migrate compared to the cells expressing eGFP-Actin-WT in the presence or absence of TBE-31. Taken together, our results suggest that TBE-31 binds to Cys 374 of actin to inhibit actin stress fiber formation and may potentially be a mechanism through which TBE-31 inhibits cell migration.

Trioxolone Methyl, a Novel Cyano Enone-Bearing 18βH-Glycyrrhetinic Acid Derivative, Ameliorates Dextran Sulphate Sodium-Induced Colitis in Mice.

Semi-synthetic triterpenoids, bearing cyano enone functionality in ring A, are considered to be novel promising therapeutic agents with complex inhibitory effects on tissue damage, inflammation and tumor growth. Previously, we showed that the cyano enone-containing 18βH-glycyrrhetinic acid derivative soloxolone methyl (SM) effectively suppressed the inflammatory response of macrophages in vitro and the development of influenza A-induced pneumonia and phlogogen-stimulated paw edema in vivo. In this work, we reported the synthesis of a novel 18βH-glycyrrhetinic acid derivative trioxolone methyl (TM), bearing a 2-cyano-3-oxo-1(2)-en moiety in ring A and a 12,19-dioxo-9(11),13(18)-dien moiety in rings C, D, and E. TM exhibited a high inhibitory effect on nitric oxide (II) production by lipopolysaccharide-stimulated J774 macrophages in vitro and dextran sulfate sodium (DSS)-induced colitis in mice, displaying higher anti-inflammatory activity in comparison with SM. TM effectively suppressed the DSS-induced epithelial damage and inflammatory infiltration of colon tissue, the hyperproduction of colonic neutral mucin and TNFα and increased glutathione synthesis. Our in silico analysis showed that Akt1, STAT3 and dopamine receptor D2 can be considered as mediators of the anti-colitic activity of TM. Our findings provided valuable information for a better understanding of the anti-inflammatory activity of cyano enone-bearing triterpenoids and revealed TM as a promising anti-inflammatory candidate.

Deep insights into the response of human cervical carcinoma cells to a new cyano enone-bearing triterpenoid soloxolone methyl: a transcriptome analysis.

Semisynthetic triterpenoids, bearing cyano enone functionality in ring A, are considered now as novel promising anti-tumor agents. However, despite the large-scale studies, their effects on cervical carcinoma cells and, moreover, mechanisms underlying cell death activation by such compounds in this cell type have not been fully elucidated. In this work, we attempted to reconstitute the key pathways and master regulators involved in the response of human cervical carcinoma KB-3-1 cells to the novel glycyrrhetinic acid derivative soloxolone methyl (SM) by a transcriptomic approach. Functional annotation of differentially expressed genes, analysis of their cis-regulatory sequences and protein-protein interaction network clearly indicated that stress of endoplasmic reticulum (ER) is the central event triggered by SM in the cells. A range of key ER stress sensors and transcription factor AP-1 were identified as upstream transcriptional regulators, controlling the response of the cells to SM. Additionally, by using Gene Expression Omnibus data, we showed the ability of SM to modulate the expression of key genes involved in regulation of the high proliferative rate of cervical carcinoma cells. Further Connectivity Map analysis revealed similarity of SM's effects with known ER stress inducers thapsigargin and geldanamycin, targeting SERCA and Grp94, respectively. According to the molecular docking study, SM could snugly fit into the active sites of these proteins in the positions very close to that of both inhibitors. Taken together, our findings provide a basis for the better understanding of the intracellular processes in tumor cells switched on in response to cyano enone-bearing triterpenoids.

Synthetic modification and cytotoxic evaluation of 2-cyano-3,4-secotriterpenic methylketones

Triterpenic methylketones, known earlier and obtainable as a result of oxidative transformation of double bond(s) in 2-cyano-3,4-secoderivatives of the lupane and 18αH-oleanane types, can be regarded as promising intermediates for synthetic transformation. This study has demonstrated the acid-catalyzed α-bromination of methylketones as capable of providing a series of various bromine-substituted ketones with different degrees of halogenation, as well as the 3,23,24-trinor-3,4-seco-18αH-oleanane acid resulting from the tribromoketone by elimination of a bromoform fragment under the same conditions. The 3,4-seco-acid ester derivative was then transformed, via the base-catalyzed intramolecular nitrile anion cyclization, to a derivative with the ketonitrile fragment in the five-membered A cycle, dehydrogenation of which afforded a cyano enone derivative. With use of the base catalysis, the 3,4-secotriterpenic bromohydrins synthesized via stereoselective reduction of 18αH-oleanane mono- and dibromoketones were transformed to C(4) epimeric terminal 4,23-epoxides. According to cytotoxic screening of the synthesized compounds, the bromoketones showed the most pronounced cytotoxic effect, whereas their derivatives partially or completely lost their cytotoxicity against the tumor cell lines under MTT test. The IC50 values characterizing the proliferation inhibition of HCT116, MS, RD TE32, and PC3 cells for the most active 2-cyano-24,24-dibromo-19β,28-epoxy-3,4-seco-3,23-dinor-18αH-olean-4-one 7 spanned the range 2.06–7.51 μM.

Experimental Nonalcoholic Steatohepatitis and Liver Fibrosis AreAmeliorated by Pharmacologic Activation of Nrf2 (NF-E2 p45-Related Factor 2).

Background & AimsNonalcoholic steatohepatitis (NASH) is associated with oxidative stress. We surmised that pharmacologic activation of NF-E2 p45-related factor 2 (Nrf2) using the acetylenic tricyclic bis(cyano enone) TBE-31 would suppress NASH because Nrf2 is a transcriptional master regulator of intracellular redox homeostasis.MethodsNrf2+/+ and Nrf2-/- C57BL/6 mice were fed a high-fat plus fructose (HFFr) or regular chow diet for 16 weeks or 30 weeks, and then treated for the final 6 weeks, while still being fed the same HFFr or regular chow diets, with either TBE-31 or dimethyl sulfoxide vehicle control. Measures of whole-body glucose homeostasis, histologic assessment of liver, and biochemical and molecular measurements of steatosis, endoplasmic reticulum (ER) stress, inflammation, apoptosis, fibrosis, and oxidative stress were performed in livers from these animals.ResultsTBE-31 treatment reversed insulin resistance in HFFr-fed wild-type mice, but not in HFFr-fed Nrf2-null mice. TBE-31 treatment of HFFr-fed wild-type mice substantially decreased liver steatosis and expression of lipid synthesis genes, while increasing hepatic expression of fatty acid oxidation and lipoprotein assembly genes. Also, TBE-31 treatment decreased ER stress, expression of inflammation genes, and markers of apoptosis, fibrosis, and oxidative stress in the livers of HFFr-fed wild-type mice. By comparison, TBE-31 did not decrease steatosis, ER stress, lipogenesis, inflammation, fibrosis, or oxidative stress in livers of HFFr-fed Nrf2-null mice.ConclusionsPharmacologic activation of Nrf2 in mice that had already been rendered obese and insulin resistant reversed insulin resistance, suppressed hepatic steatosis, and mitigated against NASH and liver fibrosis, effects that we principally attribute to inhibition of ER, inflammatory, and oxidative stress.

Abstract LB-345: Acetylenic tricyclic bis-(cyano enone) interacts with cysteine residues of actin and inhibits non-small cell lung cancer cell migration

Abstract During epithelial-to-mesenchymal transition (EMT), epithelial cells lose their cell-cell junctions, apical-basal polarity, and reorganize their actin cytoskeleton. These changes, among others, increase the motility of individual cells and promote a highly invasive phenotype. The actin cytoskeleton is also key in cell migration and invasion, as the polymerization of actin at the leading edge provides the necessary driving force for translocation and protrusions. Therefore, the actin cytoskeleton is a potential target for inhibiting tumour progression. In this study we characterized a novel tri-cyclic synthetic triterpenoid derivative, TBE-31, in its ability to associate with actin and inhibit cell migration. Using a pull-down approach, we demonstrate that TBE-31 binds directly to actin. Furthermore, TBE-31 inhibited branched and linear actin polymerization in vitro, and stress fibre formation in cultured cells. Actin cytoskeleton reorganization and stress fiber formation was also inhibited in TGFβ-dependent EMT of non-small cell lung cancer cells. We next used SwissDock software to investigate the potential molecular interaction between TBE-31 and actin. Swissdock predicted that TBE-31 would have a high affinity for binding to the same cleft as Cytochalasin D, a bona-fide actin polymerization inhibitor. As triterpenoids associate with cysteine residues in target proteins, we generated cysteine to alanine mutants of actin and verified TBE-31 binding using pull-down assays. We identified that cysteine 374 is important for TBE-31 interaction with actin. Finally, we observed that TBE-31 inhibited fibroblast and non-small cell lung tumour cell migration with an IC50 of 1.0 and 2.5 μM, respectively. Taken together, our results suggest that TBE-31 targets actin polymerization to alter cell morphology and inhibit cell migration. Citation Format: Eddie Chan, Akira Saito, Tadashi Honda, John Di Guglielmo. Acetylenic tricyclic bis-(cyano enone) interacts with cysteine residues of actin and inhibits non-small cell lung cancer cell migration. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-345.

The acetylenic tricyclic bis(cyano enone), TBE-31, targets microtubule dynamics and cell polarity in migrating cells

Cell migration is dependent on the microtubule network for structural support as well as for the proper delivery and positioning of polarity proteins at the leading edge of migrating cells. Identification of drugs that target cytoskeletal-dependent cell migration and protein transport in polarized migrating cells is important in understanding the cell biology of normal and tumor cells and can lead to new therapeutic targets in disease processes. Here, we show that the tricyclic compound TBE-31 directly binds to tubulin and interferes with microtubule dynamics, as assessed by end binding 1 (EB1) live cell imaging. Interestingly, this interference is independent of in vitro tubulin polymerization. Using immunofluorescence microscopy, we also observed that TBE-31 interferes with the polarity of migratory cells. The polarity proteins Rac1, IQGAP and Tiam1 were localized at the leading edge of DMSO-treated migrating cell, but were observed to be in multiple protrusions around the cell periphery of TBE-31-treated cells. Finally, we observed that TBE-31 inhibits the migration of Rat2 fibroblasts with an IC50 of 0.75μM. Taken together, our results suggest that the inhibition of cell migration by TBE-31 may result from the improper maintenance of cell polarity of migrating cells.

Abstract 524: Assessing the interaction between acetylenic tricyclic bis-(cyano enone) and cysteine residues of actin to inhibit non-small cell lung cancer cell migration

Abstract During epithelial-to-mesenchymal transition (EMT), epithelial cells lose their cell-cell junctions, apical-basal polarity, and reorganize their actin cytoskeleton. These changes, among others, increase the motility of individual cells and promote a highly invasive phenotype. The actin cytoskeleton is also key in cell migration and invasion, as the polymerization of actin at the leading edge provides the necessary driving force for translocation and protrusions. Therefore, the actin cytoskeleton is a potential target for inhibiting tumour progression. In this study we characterized a novel tri-cyclic synthetic triterpenoid derivative, TBE-31, in its ability to associate with actin and inhibit cell migration. Using a pull-down approach, we demonstrate that TBE-31 binds directly to actin. Furthermore, TBE-31 inhibited branched and linear actin polymerization in vitro, and stress fibre formation in cultured cells. Actin cytoskeleton reorganization and stress fiber formation was also inhibited in TGFβ-dependent EMT of non-small cell lung cancer cells. We next used SwissDock software to investigate the potential molecular interaction between TBE-31 and actin. Swissdock predicted that TBE-31 would have a high affinity for binding to the same cleft as Cytochalasin D, a bona-fide actin polymerization inhibitor. As triterpenoids associate with cysteine residues in target proteins, we generated cysteine to alanine mutants of actin and verified TBE-31 binding using pull-down assays. Finally, we observed that TBE-31 inhibited fibroblast and non-small cell lung tumor cell migration with an IC50 of 1.0 and 2.5 μM, respectively. Taken together, our results suggest that TBE-31 targets actin polymerization to alter cell morphology and inhibit cell migration. Citation Format: Eddie Chan, Akira Saito, Tadashi Honda, John Di Guglielmo. Assessing the interaction between acetylenic tricyclic bis-(cyano enone) and cysteine residues of actin to inhibit non-small cell lung cancer cell migration. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 524. doi:10.1158/1538-7445.AM2015-524

Nrf2 Activation Protects against Solar-Simulated Ultraviolet Radiation in Mice and Humans.

The transcription factor Nrf2 determines the ability to adapt and survive under conditions of electrophilic, oxidative, and inflammatory stress by regulating the expression of elaborate networks comprising nearly 500 genes encoding proteins with versatile cytoprotective functions. In mice, disruption of Nrf2 increases susceptibility to carcinogens and accelerates disease pathogenesis. Paradoxically, Nrf2 is upregulated in established human tumors, but whether this upregulation drives carcinogenesis is not known. Here we show that the incidence, multiplicity, and burden of solar-simulated UV radiation-mediated cutaneous tumors that form in SKH-1 hairless mice in which Nrf2 is genetically constitutively activated are lower than those that arise in their wild-type counterparts. Pharmacologic Nrf2 activation by topical biweekly applications of small (40 nmol) quantities of the potent bis(cyano enone) inducer TBE-31 has a similar protective effect against solar-simulated UV radiation in animals receiving long-term treatment with the immunosuppressive agent azathioprine. Genetic or pharmacologic Nrf2 activation lowers the expression of the pro-inflammatory factors IL6 and IL1β, and COX2 after acute exposure of mice to UV radiation. In healthy human subjects, topical applications of extracts delivering the Nrf2 activator sulforaphane reduced the degree of solar-simulated UV radiation-induced skin erythema, a quantifiable surrogate endpoint for cutaneous damage and skin cancer risk. Collectively, these data show that Nrf2 is not a driver for tumorigenesis even upon exposure to a very potent and complete carcinogen and strongly suggest that the frequent activation of Nrf2 in established human tumors is a marker of metabolic adaptation.

The acetylenic tricyclic bis(cyano enone), TBE-31 inhibits non-small cell lung cancer cell migration through direct binding with actin.

The migratory and invasive potential of the epithelial-derived tumor cells depends on epithelial-to-mesenchymal transition (EMT) as well as the reorganization of the cell cytoskeleton. Here, we show that the tricyclic compound acetylenic tricyclic bis(cyano enone), TBE-31, directly binds to actin and inhibits linear and branched actin polymerization in vitro. Furthermore, we observed that TBE-31 inhibits stress fiber formation in fibroblasts as well as in non-small cell lung cancer cells during TGFβ-dependent EMT. Interestingly, TBE-31 does not interfere with TGFβ-dependent signaling or changes in E-cadherin and N-cadherin protein levels during EMT. Finally, we observed that TBE-31 inhibits fibroblast and non-small cell lung tumor cell migration with an IC50 of 1.0 and 2.5 μmol/L, respectively. Taken together, our results suggest that TBE-31 targets linear actin polymerization to alter cell morphology and inhibit cell migration.

Synthesis of a furano abietane cyano enone—A new scaffold for biological exploration

A six step synthesis of furano abietane cyano enone 12 is described, in which the key step is a palladium-catalyzed intramolecular Heck reaction of bromo 3-phenoxyacrylate 17, prepared from enone phenol 13 in high yield.

Highly Potent Activation of Nrf2 by Topical Tricyclic Bis(Cyano Enone): Implications for Protection against UV Radiation during Thiopurine Therapy

Chronic treatment with azathioprine, a highly effective anti-inflammatory and immunosuppressive agent, profoundly increases the risk for development of unusually aggressive cutaneous squamous cell carcinoma. Its ultimate metabolite, 6-thioguanine (6-TG) nucleotide, is incorporated in DNA of skin cells, and upon exposure to UVA radiation, causes oxidative stress, followed by damage of DNA and associated proteins. The acetylenic tricyclic bis(cyano enone) TBE-31 is a strong inhibitor of inflammation and a potent inducer of the Keap1/Nrf2/ARE pathway, which orchestrates the expression of a large network of cytoprotective genes. We now report that long-term (five days per week for four weeks) topical daily applications of small (200 nmol) quantities of TBE-31 cause a robust systemic induction of the Keap1/Nrf2/ARE pathway and decreases the 6-TG incorporation in DNA of skin, blood, and liver of azathioprine-treated mice, indicating extraordinary bioavailability and efficacy. In addition, TBE-31, at nanomolar concentrations, protects cells with 6-TG in their genomic DNA against oxidative stress caused by UVA radiation through induction of the Keap1/Nrf2/ARE pathway. At the same 6-TG DNA levels, Keap1-knockout cells, in which the pathway is constitutively upregulated, are highly resistant to UVA radiation-induced oxidative stress. The protective effects of both the Keap1-knockout genotype and TBE-31 are completely lost in the absence of transcription factor Nrf2. Our findings suggest that compounds of this kind are excellent candidates for mechanism-based chemoprotective agents against conditions in which oxidative stress and inflammation underlie disease pathogenesis. Moreover, their potential skin patch incorporation for transdermal delivery is an exciting possibility.

Abstract 476: The effects of the synthetic triterpenoid acetylenic tricyclic bis-(cyano enone) on cell migration and epithelial-to-mesenchymal transition

Abstract During metastasis, epithelial tumor cells undergo epithelial to mesenchymal transition (EMT) allowing them to migrate to distant organs to establish secondary tumors. Cell migration is initiated by the asymmetrical localization of polarity proteins towards the leading edge. This stimulates the reorganization and polymerization of the microtubule and actin cytoskeletons, which form protrusions in the plasma membrane to drive the cell forwards. Metastasis accounts for over 90% of cancer related deaths, thus a reduction in cancer mortality will require therapies aimed at preventing or delaying the events of metastasis. Our lab has identified the synthetic triterpenoid, CDDO-Im, as a potent inhibitor of cell migration by inhibiting the polymerization of branched actin and disrupting the organization of the microtubule network (To et al., J Biol Chem. 2008, 2010). Recently, TBE-31 has been developed, which is a smaller 3-ring compound that contains the same active functional groups as CDDO-Im. Here we assessed the effects of TBE-31 on cell migration and EMT. TBE-31 was found to displace the polarity proteins from the leading edge of migrating cells and induce multiple cell protrusions. The microtubule network was also observed to be disorganized and the rate of polymerization for both tubulin and actin were lowered in the presence of TBE-31. These effects are believed to allow submicromolar concentrations TBE-31 to inhibit cell migration by as much as 60%. Finally, the reorganization of actin and formation of stress fibers normally associated with EMT was also inhibited by TBE-31 in A549 tumor cells. We are now confirming our results in a panel of lung tumor cell lines. In conclusion, TBE-31 disrupts the cytoskeleton and inhibits cell migration and preliminary data suggest TBE-31 may also hinder EMT. Further research will be needed to determine the overall impact these effects have on the progression of metastasis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 476. doi:1538-7445.AM2012-476

Synthetic Triterpenoid Cyano Enone of Methyl Boswellate Activates Intrinsic, Extrinsic, and Endoplasmic Reticulum Stress Cell Death Pathways in Tumor Cell Lines

We explored the effect of a novel synthetic triterpenoid compound cyano enone of methyl boswellates (CEMB) on various prostate cancer and glioma cancer cell lines. CEMB displayed concentration-dependent cytotoxic activity with submicromolar lethal dose 50% (LD(50)) values in 10 of 10 tumor cell lines tested. CEMB-induced cytotoxicity is accompanied by activation of downstream effector caspases (caspases 3 and 7) and by upstream initiator caspases involved in both the extrinsic (caspase 8) and intrinsic (caspase 9) apoptotic pathways. By using short interfering RNAs (siRNA), we show evidence that knockdown of caspase 8, DR4, Apaf-1, and Bid impairs CEMB-induced cell death. Similar to other proapoptotic synthetic triterpenoid compounds, CEMB-induced apoptosis involved endoplasmic reticulum stress, as shown by partial rescue of tumor cells by siRNA-mediated knockdown of expression of genes involved in the unfolded protein response such as IRE1α, PERK, and ATF6. Altogether, our results suggest that CEMB stimulates several apoptotic pathways in cancer cells, suggesting that this compound should be evaluated further as a potential agent for cancer therapy.

Growth inhibitory, apoptotic and anti-inflammatory activities displayed by a novel modified triterpenoid, cyano enone of methyl boswellates

Triterpenoids are pentacyclic secondary metabolites present in many terrestrial plants. Natural triterpenoids have been reported to exhibit anti-inflammatory and anti-carcinogenic activities. Here, we show that modifications of ring A of boswellic acid (2 cyano, 3 enone) resulted in a highly active growth inhibitory, anti-inflammatory, prodifferentiative and anti-tumour triterpenoid compound called cyano enone of methyl boswellates (CEMB). This compound showed cytotoxic activity on a number of cancer cell lines with IC₅₀ ranging from 0.2 to 0.6 μM. CEMB inhibits DNA synthesis and induces apoptosis in A549 cell line at 0.25 μM and 1 μM concentrations, respectively. CEMB induces adipogenic differentiation in 3T3-L1 cells at a concentration of 0.1 μM. Finally, administration of CEMB intra-tumourally significantly inhibited the growth of C6 glioma tumour xenograft in immuno-compromised mice. Collectively, these results suggest that CEMB is a very potent anti-tumour compound.

Abstract 1400: Inhibition of cell migration by the synthetic triterpenoid acetylenic tricyclic bis-(cyano enone)

Abstract Triterpenoids are a family of naturally occurring compounds that have multiple anti-tumorigenic effects, including the ability to induce cell differentiation, apoptosis and inhibit proliferation. Research in our lab has demonstrated that a synthetically derived 5 ring triterpenoid, 2-cyano-3, 12-dioxooleana-1,9-dien-28-oic acid-imidazolide (CDDO-Im), inhibits cell migration (To et al., 2008, J. Biol. Chem. 283:11700), which is essential in numerous physiological processes including tumor metastasis. Recently, a smaller 3 ring compound containing the same active functional groups as CDDO-Im has been derived; acetylenic tricyclic bis-(cyano enone) [(+/-)-(4aa,8aa,10ab)-1,2,4a,6,8a,9,10,10a-octahydro-8a-ethynyl-1,1,4a-trimethyl-2,6 dioxophenanthrene-3,7-dicarbonitrile] (TBE-31). Here we examined the effect of TBE-31 on cell migration. Using scratch assays with Rat2 fibroblasts we demonstrated that concentrations of TBE-31 above 0.75 µM were effective in inhibiting fibroblast migration. To elucidate the mechanism(s) for this inhibition we examined different components of the cytoskeleton and the polarity complex, which are both crucial for cell migration. To examine cell polarity, we used immunofluorescence microscopy to assess the localization of two proteins involved in the polarization of migrating cells, IQGAP1 and RAC1. Similar to CDDO-Im, TBE-31 was observed to reduce the elongation and polarity of cells, however unlike CDDO-Im, IQGAP1 and RAC1 in TBE-31 treated cells were localized in punctate fashion around the cell perimeter instead of at the leading edge. Using immunofluorescence imaging, the cytoskeleton of Mv1Lu mink lung cells or COS7 cells treated with TBE-31 were analyzed. The microtubule network of treated cells displayed a unique cross-hatched phenotype and were resistant to nocodazole depolymerization. In addition, the intermediate filament cytoskeleton was observed to retract towards the nucleus. Lastly, in vitro actin polymerization assays revealed that TBE-31 inhibits linear but not branched actin polymerization. We conclude that TBE-31 is an effective inhibitor of cell migration and further research will shed light on the mechanisms that TBE-31 uses to modulate the cell migration machinery. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1400. doi:10.1158/1538-7445.AM2011-1400

Tricyclic Compounds Containing Nonenolizable Cyano Enones. A Novel Class of Highly Potent Anti-Inflammatory and Cytoprotective Agents

Forty-four novel tricycles containing nonenolizable cyano enones (TCEs) were designed and synthesized on the basis of a semisynthetic pentacyclic triterpenoid, bardoxolone methyl, which is currently being developed in phase II clinical trials for the treatment of severe chronic kidney disease in diabetic patients. Most of the TCEs having two different kinds of nonenolizable cyano enones in rings A and C are highly potent suppressors of induction of inducible nitric oxide synthase stimulated with interferon-γ and are highly potent inducers of the cytoprotective enzymes heme oxygenase-1 and NAD(P)H:quinone oxidoreductase-1. Among these compounds, (±)-(4bS,8aR,10aS)-10a-ethynyl-4b,8,8-trimethyl-3,7-dioxo-3,4b,7,8,8a,9,10,10a-octahydrophenanthrene-2,6-dicarbonitrile ((±)-31) is the most potent in these bioassays in our pool of drug candidates including semisynthetic triterpenoids and synthetic tricycles. These facts strongly suggest that an essential factor for potency is not a triterpenoid skeleton but the cyano enone functionality. Notably, TCE 31 reduces hepatic tumorigenesis induced with aflatoxin in rats. Further preclinical studies and detailed mechanism studies on 31 are in progress.

An Exceptionally Potent Inducer of Cytoprotective Enzymes: ELUCIDATION OF THE STRUCTURAL FEATURES THAT DETERMINE INDUCER POTENCY AND REACTIVITY WITH Keap1*

The Keap1/Nrf2/ARE pathway controls a network of cytoprotective genes that defend against the damaging effects of oxidative and electrophilic stress, and inflammation. Induction of this pathway is a highly effective strategy in combating the risk of cancer and chronic degenerative diseases, including atherosclerosis and neurodegeneration. An acetylenic tricyclic bis(cyano enone) bearing two highly electrophilic Michael acceptors is an extremely potent inducer in cells and in vivo. We demonstrate spectroscopically that both cyano enone functions of the tricyclic molecule react with cysteine residues of Keap1 and activate transcription of cytoprotective genes. Novel monocyclic cyano enones, representing fragments of rings A and C of the tricyclic compound, reveal that the contribution to inducer potency of the ring C Michael acceptor is much greater than that of ring A, and that potency is further enhanced by spatial proximity of an acetylenic function. Critically, the simultaneous presence of two cyano enone functions in rings A and C within a rigid three-ring system results in exceptionally high inducer potency. Detailed understanding of the structural elements that contribute to the reactivity with the protein sensor Keap1 and to high potency of induction is essential for the development of specific and selective lead compounds as clinically relevant chemoprotective agents.

A Novel Acetylenic Tricyclic bis-(Cyano Enone) Potently Induces Phase 2 Cytoprotective Pathways and Blocks Liver Carcinogenesis Induced by Aflatoxin

A novel acetylenic tricyclic bis-(cyano enone), TBE-31, is a lead compound in a series of tricyclic compounds with enone functionalities in rings A and C. Nanomolar concentrations of this potent multifunctional molecule suppress the induction of the inflammatory protein, inducible nitric oxide synthase, activate phase 2 cytoprotective enzymes in vitro and in vivo, block cell proliferation, and induce differentiation and apoptosis of leukemia cells. Oral administration of TBE-31 also significantly reduces formation of aflatoxin-DNA adducts and decreases size and number of aflatoxin-induced preneoplastic hepatic lesions in rats by >90%. Because of the two cyano enones in rings A and C, TBE-31 may directly interact with DTT and protein targets such as Keap1 that contain reactive cysteine residues. The above findings suggest that TBE-31 should also be tested for chemoprevention and chemotherapy in relevant models of cancer and against other chronic, degenerative diseases in which inflammation and oxidative stress contribute to disease pathogenesis.