Synthetic Triterpenoid Research Articles

The synthetic triterpenoid RTA dh404 (CDDO-dhTFEA) restores endothelial function impaired by reduced Nrf2 activity in chronic kidney disease

Chronic kidney disease (CKD) is associated with endothelial dysfunction and accelerated cardiovascular disease, which are largely driven by systemic oxidative stress and inflammation. Oxidative stress and inflammation in CKD are associated with and, in part, due to impaired activity of the cytoprotective transcription factor Nrf2. RTA dh404 is a synthetic oleanane triterpenoid compound which potently activates Nrf2 and inhibits the pro-inflammatory transcription factor NF-κB. This study was designed to test the effects of RTA dh404 on endothelial function, inflammation, and the Nrf2-mediated antioxidative system in the aorta of rats with CKD induced by 5/6 nephrectomy. Sham-operated rats served as controls. Subgroups of CKD rats were treated orally with RTA dh404 (2mg/kg/day) or vehicle for 12 weeks. The aortic rings from untreated CKD rats exhibited a significant reduction in the acetylcholine-induced relaxation response which was restored by RTA dh404 administration. Impaired endothelial function in the untreated CKD rats was accompanied by significant reduction of Nrf2 activity (nuclear translocation) and expression of its cytoprotective target genes, as well as accumulation of nitrotyrosine and upregulation of NAD(P)H oxidases, 12-lipoxygenase, MCP-1, and angiotensin II receptors in the aorta. These abnormalities were ameliorated by RTA dh404 administration, as demonstrated by the full or partial restoration of the expression of all the above analytes to sham control levels. Collectively, the data demonstrate that endothelial dysfunction in rats with CKD induced by 5/6 nephrectomy is associated with impaired Nrf2 activity in arterial tissue, which can be reversed with long term administration of RTA dh404.

Effective melanoma inhibition by synthetic pentacyclic triterpenoid 2-(3-phenylprop-2-en-1-ylidene)-22β-hydroxy-3-oxoolean-12-en-28-oic acid: An in vitro and in vivo study

The C-2 arylidene analog (compound 3) of pentacyclic triterpenoid Lantadene A (compound 1) was synthesized and evaluated by the National Cancer Institute, USA, for in vitro cytotoxicity against a panel of melanoma cancer cell lines: LOX IMVI, MALME-3M, M14, MDA-MB-435, SK-MEL-2, SK-MEL-28, SK-MEL-5, UACC-257 UACC-62 and B16F10. Compound 3 showed enhanced cytotoxicity compared with compound 1 and the standard drug cisplatin. At the same time, compound 3 showed selective toxicity toward cancer cells and was inactive (i.e., nontoxic) against normal cells (VERO). Compound 3 induced sub-G1 cell cycle arrest and apoptosis in B16F10 cells by down-regulating NF-κB, c-jun, Bcl-2, and by activating caspase-3 and Bax expression. Compound 3 also demonstrated beneficial effects in a clinically relevant B16F10 allograft mice model, with significant reduction of tumor growth/tumor weight in vivo. Compound 3 improved the survival rate in comparison to the control group and the cisplatin group. At the same time, compound 3 had a better safety profile than cisplatin in terms of hematological parameters and liver enzyme levels.

CDDO-9,11-dihydro-trifluoroethyl amide (CDDO-dhTFEA) induces hepatic cytoprotective genes and increases bile flow in rats

1. The transcription factor Nrf2 is important for hepatoprotection against oxidative stress, as it regulates many cytoprotective genes, including several important for glutathione (GSH) homeostasis. In addition to being an important endogenous antioxidant, GSH is also critical for the maintenance of bile acid-independent bile flow. While it has been well-established that synthetic oleanane triterpenoids pharmacologically activate Nrf2, their effects on bile flow and hepatic cytoprotective capacity have not been fully explored.2. The present studies were conducted to evaluate the effects of a compound in this class, CDDO-9,11-dihydro-trifluoroethyl amide (CDDO-dhTFEA), on these parameters. CDDO-dhTFEA at 3, 10 or 30 mg/kg was orally administered to bile duct-cannulated rats once daily for 7 days, with bile collected 5 h after each dose for 1 h. Livers were harvested after the final bile collection for the evaluation of histology and Nrf2 targets.3. CDDO-dhTFEA did not affect liver histology. CDDO-dhTFEA markedly and dose-dependently increased bile flow, as well as the biliary excretion of GSH, cholesterol and phospholipids without affecting biliary excretion of bile acids. This was accompanied by dose-dependent increases in mRNA expression and/or enzyme activity of a broad panel of cytoprotective Nrf2 target genes, including NAD(P)H quinone oxidoreductase 1 (Nqo1), thioredoxin reductase (Txnrd), sulfiredoxin 1(Srxn1), glutamate cysteine ligase catalytic and modifier subunits (Gclc and Gclm), glutathione reductase (Gsr), gamma-glutamyl transpeptidase 1 (Ggt1), heme oxygenase-1 (Ho-1) and epoxide hydrolase-1 (Eh-1).4. These data further demonstrate the important hepatobiliary attributes of oleanane synthetic triterpenoids and support their continued investigation for liver diseases.

Telomerase Reverse Transcriptase (TERT) is a Therapeutic Target of Oleanane Triterpenoid CDDO-Me in Prostate Cancer

Methyl-2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oate (CDDO-Me) is an synthetic oleanane triterpenoid with strong antiprolifertive and proapoptotic activities in cancer cells. However, the effect of CDDO-Me on human telomerase reverse transcriptase (hTERT) and its telomerase activity in prostate cancer cells has not been studied. We investigated the role of hTERT in mediating the anticancer activity of CDDO-Me in prostate cancer cells in vitro and in vivo. The inhibition of cell proliferation and induction of apoptosis by CDDO-Me in LNCaP and PC-3 prostate cancer cell lines was associated with the inhibition of hTERT gene expression, hTERT telomerase activity and a number of proteins that regulate hTERT transcriptionally and post-translationally. Furthermore, ablation of hTERT protein increased the sensitivity of cancer cells to CDDO-Me, whereas its overexpression rendered them resistant to CDDO-Me. In addition, inhibition of progression of preneoplastic lesions (i.e., low and high-grade prostate intraepithelial neoplasms, PINs) to adenocarcinoma of the prostate by CDDO-Me in TRAMP mice was associated with significant decrease in TERT and its regulatory proteins in the prostate gland. These data provide evidence that telomerase is a potential target of CDDO-Me for the prevention and treatment of prostate cancer.

Analogs of bardoxolone methyl worsen diabetic nephropathy in rats with additional adverse effects

Bardoxolone methyl is an antioxidant inflammation modulator acting through induction of Keap1-Nrf2 pathway. Results from a recent phase IIb clinical trial reported that bardoxolone methyl was associated with improvement in the estimated glomerular filtration rate in patients with advanced chronic kidney disease and Type 2 diabetes. However, increases in albuminuria, serum transaminase, and frequency of adverse events were noted. We studied the effect of 3-mo treatment with RTA 405, a synthetic triterpenoid analog of bardoxolone methyl in Zucker diabetic fatty rats with overt Type 2 diabetes. Rats were treated from 3 mo of age with vehicle, RTA 405, ramipril, or RTA 405 plus ramipril. RTA 405 caused severe changes in food intake and diuresis with decline in body weight, worsening of dyslipidemia, and increase in blood pressure. Early elevation in serum transaminase was followed by liver injury. RTA 405 worsened proteinuria, glomerulosclerosis, and tubular damage. Ramipril was renoprotective, but when given with RTA 405 it was not able to limit its worsening effects. These data could be due to degradation products in the drug substance used, as disclosed by the company once the study was concluded. To overcome such a drawback, the company offered to test dh404, a variant of RTA 405, in Zucker diabetic fatty rats. The dh404 did not display beneficial effects on proteinuria, glomerulosclerosis, and interstitial inflammation. Rather, kidneys from three rats receiving dh404 showed the presence of a granulomatous and inflammatory process reminiscent of a pseudotumor. Altogether these data raise serious concerns on the use of bardoxolone analogs in Type 2 diabetic nephropathy.

The triterpenoid pristimerin induces U87 glioma cell apoptosis through reactive oxygen species-mediated mitochondrial dysfunction

It has become evident that some of the natural or synthetic triterpenoids are natural proteasome inhibitors that have great potential for use in cancer prevention and treatment. However, the mechanisms for the antitumor activity of triterpenoids remain to be elucidated. In the present study, we investigated the anticancer activities of a natural triterpenoid, pristimerin, and the signaling pathways affected. Pristimerin was found to possess potent cytotoxic effects, inducing apoptosis and inhibiting proliferation in U87 human glioma cells. Hoechst 33258 staining and Annexin V/PI double staining exhibited the typical nuclear features of apoptosis and increased the proportion of apoptotic Annexin V-positive cells in a dose-dependent manner, respectively. Moreover, western blotting assay revealed that this apoptotic induction was associated with activated caspase-9, caspase-3, PARP cleavage and downregulation of Bcl-xl/Bax in a concentration-dependent manner. Pristimerin also increased the generation of reactive oxygen species and induced the subsequent release of cytochrome c from the mitochondria into the cytosol. Additionally, pristimerin downregulated EGFR protein expression and inhibited downstream signaling pathways in U87 cells. Our results suggest that pristimerin may have potential as a new targeting therapeutic strategy in the treatment of EGFR-overexpressing gliomas.

Targeting of Nrf2 induces DNA damage signaling and protects colonic epithelial cells from ionizing radiation

Nuclear factor-erythroid 2-related factor 2 (Nrf2) is a key transcriptional regulator for antioxidant and anti-inflammation enzymes that binds to its endogenous inhibitor protein, Kelch-like ECH (erythroid cell-derived protein with CNC homology)-associated protein 1, in the cytoplasm under normal conditions. Various endogenous or environmental oxidative stresses, such as ionizing radiation (IR), can disrupt the Nrf2-Kelch-like ECH-associated protein 1 complex. This allows Nrf2 to translocate from the cytoplasm into the nucleus to induce transcription of heme oxygenase-1 and other cytoprotective enzymes through binding to antioxidant responsive elements. However, how Nrf2 protects cells from IR-induced damage remains unclear. Here, we report that Nrf2 activation by the synthetic triterpenoids, bardoxolone methyl (BARD) and 2-cyano-3,12-dioxooleana-1,9 (11)-dien-28-oic acid-ethyl amide, protects colonic epithelial cells against IR-induced damage, in part, by enhancing signaling of the DNA damage response. Pretreatment with BARD reduced the frequency of both G1 and S/G2 chromosome aberrations and enhanced the disappearance of repairosomes (C-terminal binding protein interacting protein, Rad51, and p53 binding protein-1 foci) after IR. BARD protected cells from IR toxicity in a Nrf2-dependent manner. The p53 binding protein-1 promoter contains three antioxidant responsive elements in which Nrf2 directly binds following BARD treatment. In addition, 2-cyano-3,12-dioxooleana-1,9 (11)-dien-28-oic acid-ethyl amide provided before exposure to a lethal dose of whole-body irradiation protected WT mice from DNA damage and acute gastrointestinal toxicity, which resulted in improved overall survival. These results demonstrate that Nrf2 activation by synthetic triterpenoids is a promising candidate target to protect the gastrointestinal tract against acute IR in vitro and in vivo.

The combination of the histone deacetylase inhibitor vorinostat and synthetic triterpenoids reduces tumorigenesis in mouse models of cancer

Novel drugs and drug combinations are needed for the chemoprevention and treatment of cancer. We show that the histone deacetylase inhibitor vorinostat [suberoylanilide hydroxamic acid (SAHA)] and the methyl ester or ethyl amide derivatives of the synthetic triterpenoid 2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oic acid (CDDO-Me and CDDO-Ea, respectively) cooperated to inhibit the de novo synthesis of nitric oxide in RAW 264.7 macrophage-like cells and in primary mouse peritoneal macrophages. Additionally, SAHA enhanced the ability of synthetic triterpenoids to delay formation of estrogen receptor-negative mammary tumors in MMTV-polyoma middle T (PyMT) mice. CDDO-Me (50 mg/kg diet) and SAHA (250 mg/kg diet) each significantly delayed the initial development of tumors by 4 (P < 0.001) and 2 (P < 0.05) weeks, respectively, compared with the control group in the time required to reach 50% tumor incidence. CDDO-Ea (400 mg/kg diet), as a single agent, did not delay tumor development. The combination of either triterpenoid with SAHA was significantly more potent than the individual drugs for delaying tumor development, with a 7 week (P < 0.001) delay before 50% tumor incidence was reached. SAHA, alone and in combination with CDDO-Me, also significantly (P < 0.05) inhibited the infiltration of tumor-associated macrophages into the mammary glands of PyMT mice and levels of the chemokine macrophage colony-stimulating factor in primary PyMT tumor cells. In addition, SAHA and the synthetic triterpenoids cooperated to suppress secreted levels of the pro-angiogenic factor matrix metalloproteinase-9. Similar results were observed in mouse models of pancreatic and lung cancer. At concentrations that were anti-inflammatory, SAHA had no effect on histone acetylation. These studies suggest that both SAHA and triterpenoids effectively delay tumorigenesis, thereby demonstrating a promising, novel drug combination for chemoprevention.

Triterpenoid dihydro-CDDO-trifluoroethyl amide protects against maladaptive cardiac remodeling and dysfunction in mice: a critical role of Nrf2.

Background and AimsNuclear factor E2-related factor 2 (Nrf2) appears to be an attractive therapeutic target for the treatment of cardiac disease. We investigated whether a synthetic triterpenoid derivative of dihydro-CDDO-trifluoroethylamide (dh404), a novel Nrf2 activator, protects against pathological cardiac responses to hemodynamic stress in mice.MethodsCardiac maladaptive remodeling and dysfunction were established by transverse aortic constriction (TAC) in mice. Hypertrophic growth of rat neonatal cardiomyocytes was induced by angiotensin II (Ang II). Cell death of rat neonatal cardiomyocytes was induced with hydrogen peroxide (H2O2). Cellular proliferation of rat neonatal cardiac fibroblasts was induced by Ang II, norepinephrine (NE) and phenylephrine (PE). Protein expression was assessed by immunochemical staining and Western blots. Gene expression was determined by real time reverse transcription-polymerase chain reaction (Q-PCR).ResultsTAC suppressed myocardial Nrf2 expression, increased myocardial 4-hydroxy-2-nonenal and 8-hydroxydeoxyguanosine levels, and induced cardiac hypertrophy, fibrosis and apoptosis, and overt heart failure and death in mice. Administration of dh404 inhibited the pathological cardiac remodeling and dysfunction, and reduced the mortality. Moreover, dhd404 elevated myocardial levels of Nrf2 and Nrf2 nuclear translocation with a dramatic suppression of the oxidative stress in the heart. Dh404 inhibited hypertrophic growth and death in primary culture of rat neonatal cardiomyocytes and suppressed proliferation in primary culture of rat neonatal cardiac fibroblasts. However, these effects of dh404 were blunted by knocking down of Nrf2.ConclusionThese findings demonstrate that dh404 prevents pathological cardiac remodeling and dysfunction by activating Nrf2, indicating a therapeutic potential of dh404 for cardiac disease.

Synthetic Oleanane Triterpenoids: Multifunctional Drugs with a Broad Range of Applications for Prevention and Treatment of Chronic Disease

We review the rationale for the use of synthetic oleanane triterpenoids (SOs) for prevention and treatment of disease, as well as extensive biological data on this topic resulting from both cell culture and in vivo studies. Emphasis is placed on understanding mechanisms of action. SOs are noncytotoxic drugs with an excellent safety profile. Several hundred SOs have now been synthesized and in vitro have been shown to: 1) suppress inflammation and oxidative stress and therefore be cytoprotective, especially at low nanomolar doses, 2) induce differentiation, and 3) block cell proliferation and induce apoptosis at higher micromolar doses. Animal data on the use of SOs in neurodegenerative diseases and in diseases of the eye, lung, cardiovascular system, liver, gastrointestinal tract, and kidney, as well as in cancer and in metabolic and inflammatory/autoimmune disorders, are reviewed. The importance of the cytoprotective Kelch-like erythroid cell-derived protein with CNC homology-associated protein 1/nuclear factor (erythroid-derived 2)-like 2/antioxidant response element (Keap1/Nrf2/ARE) pathway as a mechanism of action is explained, but interactions with peroxisome proliferator-activated receptor γ (PARPγ), inhibitor of nuclear factor-κB kinase complex (IKK), janus tyrosine kinase/signal transducer and activator of transcription (JAK/STAT), human epidermal growth factor receptor 2 (HER2)/ErbB2/neu, phosphatase and tensin homolog (PTEN), the phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) pathway, mammalian target of rapamycin (mTOR), and the thiol proteome are also described. In these interactions, Michael addition of SOs to reactive cysteine residues in specific molecular targets triggers biological activity. Ultimately, SOs are multifunctional drugs that regulate the activity of entire networks. Recent progress in the earliest clinical trials with 2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oic acid (CDDO) methyl ester (bardoxolone methyl) is also summarized.

Targeting Nrf2-Mediated Gene Transcription by Extremely Potent Synthetic Triterpenoids Attenuate Dopaminergic Neurotoxicity in the MPTP Mouse Model of Parkinson's Disease

Although the etiology of Parkinson's disease (PD) remains unclear, ample empirical evidence suggests that oxidative stress is a major player in the development of PD and in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) neurotoxicity. Nuclear factor E2-related factor 2 (Nrf2) is a redox-sensitive transcription factor that upregulates a battery of antioxidant response element (ARE)-driven antioxidative and cytoprotective genes that defend against oxidative stress. We evaluated whether the strategy of activation of Nrf2 and its downstream network of cytoprotective genes with small molecule synthetic triterpenoids (TP) attenuate MPTP-induced PD in mice. We show that synthetic TP are thus far the most potent and direct activators of the Nrf2 pathway using a novel Neh2-luciferase reporter. They upregulate several cytoprotective genes, including those involved in glutathione biosynthesis in vitro. Oral administration of TP that were structurally modified to penetrate the brain-induced messenger RNA and protein levels for a battery of Nrf2-dependent cytoprotective genes reduced MPTP-induced oxidative stress and inflammation, and ameliorated dopaminergic neurotoxicity in mice. The neuroprotective effect of these TP against MPTP neurotoxicity was dependent on Nrf2, since treatment with TP in Nrf2 knockout mice failed to block against MPTP neurotoxicity and induce Nrf2-dependent cytoprotective genes. Extremely potent synthetic TP that are direct activators of the Nrf2 pathway block dopaminergic neurodegeneration in the MPTP mouse model of PD. Our results indicate that activation of Nrf2/antioxidant response element (ARE) signaling by synthetic TP is directly associated with their neuroprotective effects against MPTP neurotoxicity and suggest that targeting the Nrf2/ARE pathway is a promising approach for therapeutic intervention in PD.

A Phase I First-in-Human Trial of Bardoxolone Methyl in Patients with Advanced Solid Tumors and Lymphomas

Bardoxolone methyl, a novel synthetic triterpenoid and antioxidant inflammation modulator, potently induces Nrf2 and inhibits NF-κB and Janus-activated kinase/STAT signaling. This first-in-human phase I clinical trial aimed to determine the dose-limiting toxicities (DLT), maximum tolerated dose (MTD), and appropriate dose for phase II studies; characterize pharmacokinetic and pharmacodynamic parameters; and assess antitumor activity. Bardoxolone methyl was administered orally once daily for 21 days of a 28-day cycle. An accelerated titration design was employed until a grade 2-related adverse event occurred. A standard 3 + 3 dose escalation was then employed until the MTD was reached. Single dose and steady-state plasma pharmacokinetics of the drug were characterized. Assessment of Nrf2 activation was examined in peripheral blood mononuclear cells (PBMC) by measuring NAD(P)H:quinone oxidoreductase (NQO1) mRNA levels. Immunohistochemical assessment of markers of inflammation, cell cycle, and apoptosis was carried out on tumor biopsies. The DLTs were grade 3 reversible liver transaminase elevations. The MTD was established as 900 mg/d. A complete tumor response occurred in a mantle cell lymphoma patient, and a partial response was observed in an anaplastic thyroid carcinoma patient. NQO1 mRNA levels increased in PBMCs, and NF-κB and cyclin D1 levels decreased in tumor biopsies. Estimated glomerular filtration rate (eGFR) was also increased. Bardoxolone methyl was well tolerated with an MTD of 900 mg/d. The increase in eGFR suggests that bardoxolone methyl might be beneficial in chronic kidney disease. Objective tumor responses and pharmacodynamic effects were observed, supporting continued development of other synthetic triterpenoids in cancer.

Inhibition of cell proliferation and induction of apoptosis by oleanane triterpenoid (CDDO-Me) in pancreatic cancer cells is associated with the suppression of hTERT gene expression and its telomerase activity

Methyl-2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oate (CDDO-Me) is a multifunctional oleanane synthetic triterpenoid with potent anti-inflammatory and antitumorigenic properties. The mechanisms of the antisurvival and apoptosis-inducing activities of CDDO-Me and related derivatives of oleanolic acid have been defined; however, to date, no study has been carried out on the effect of CDDOs on human telomerase reverse transcriptase (hTERT) gene or telomerase activity. Here we report for the first time that inhibition of cell proliferation and induction of apoptosis by CDDO-Me in pancreatic cancer cell lines is associated with the inhibition of hTERT gene expression, hTERT telomerase activity and a number of proteins that regulate hTERT expression and activity. Furthermore, abrogation or overexpression of hTERT protein altered the susceptibility of tumor cells to CDDO-Me. These findings suggest that telomerase (hTERT) is a relevant target of CDDO-Me in pancreatic cancer cells.

The Synthetic Triterpenoid CDDO-Methyl Ester Delays Estrogen Receptor–Negative Mammary Carcinogenesis in Polyoma Middle T Mice

Novel drugs are needed for the prevention and treatment of breast cancer. Synthetic triterpenoids are a promising new class of compounds with activity in a variety of preclinical cancer models. We tested activity of the methyl ester derivative of the synthetic triterpenoid, 2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oic acid (CDDO-Me), in a relevant model of estrogen receptor-negative breast cancer, the polyoma-middle T (PyMT), in which the oncoprotein drives carcinogenesis. The developing tumors recapitulate key features of the human disease. Mice were fed CDDO-Me (50 mg/kg diet), starting at 4 weeks of age. CDDO-Me significantly increased the age of mice at onset of first tumor (P < 0.001) by an average of 4.3 weeks and overall survival (P < 0.001) by 5.2 weeks. The drug also inhibited the infiltration of tumor-associated macrophages into mammary glands of PyMT mice at 12 weeks of age and reduced levels of the chemokines CXCL12 and CCL2 in primary PyMT mammary tumor cells. Treatment with this multifunctional drug also inhibited secretion of matrix metalloproteinase-9 in primary tumor cells from PyMT mice and decreased proliferation of these cells by inhibiting cyclin D1 and decreasing phosphorylation of epidermal growth factor receptor and STAT3.

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

Abstract 1833: A large-scale synthetic lethal RNAi screening identifies unique sensitizing targets for anti-inflammatory CDDO-Me in metastatic melanoma

Abstract Metastatic melanoma is the most lethal form of skin cancer strongly associated with the inflammatory process by secreting high levels of proinflammatory cytokines and producing reactive oxygen and nitrogen species. Chronic inflammation is considered as a major factor to promote the tumor microenvironment in advantage of resistance to radiation, chemotherapy, and biotherapy for metastatic melanoma. CDDO-Me, a novel synthetic triterpenoid, has been shown to exert potent anti-inflammatory and antitumor activity by decreasing oxidative stress and the production of pro-inflammatory molecules, such as Nrf2 and iNOS, in several tumor models. CDDO-Me is presently under evaluation in clinical studies for chronic kidney disease and pancreatic cancer. Here, we used CDDO-Me as a primary agent to inhibit metastatic melanoma growth. In order to improve CDDO-Me response in melanoma cells, we utilized a large-scale synthetic lethal RNAi screen with 24,000 siRNAs targeting ∼6,000 human druggable genes to identify targets that when silenced would sensitize melanoma cells to CDDO-Me. Results from the screens identified twenty of siRNA pools that significantly potentiated the growth inhibitory effects of CDDO-Me in A375 cells. We selected five unique genes, GNPAT, SUMO1, SPUNT2, FLI1, and SSX1, which have not been addressed as drug targets in melanoma before, for target validation and functional analysis in four metastatic melanoma and control cell lines. Specific siRNA against each of these five genes could substantially sensitize four tested melanoma cells to CDDO-me by increasing the growth inhibition and induction of apoptosis, while treatment with nontarget siRNA resulted in no change compared to the treatment with CDDO-Me only. Further studies of downstream signaling revealed that these five genes involved in regulating melanoma cell proliferation and cell death. We identified for the first time that the levels of phosphorylated Erk1/2, Akt, GSK-2, and PRAS40, were dramatically decreased by individual siRNA against GNPAT, SUMO1, SPUNT2, FLI1, and SSX1. Our findings indicate that GNPAT, SUMO1, SPUNT2, FLI1, and SSX1 may play critical roles in synergy with inflammation pathways in modulating melanoma cell survival, which could serve as sensitizing targets to enhance CDDO-Me efficacy in melanoma. Supported by MDACC SPORE in Melanoma P50CA093459. 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 1833. doi:1538-7445.AM2012-1833

Abstract 466: Synthetic triterpenoids target cell migration and cell adhesion via GSK3β

Abstract Synthetic triterpenoids are a class of anti-tumor compounds that target various cellular functions including apoptosis, growth inhibition, anti-inflammation and cytoprotection. Previously, we have shown that triterpenoids also inhibit cell migration and the objective of our current study is to examine the molecular mechanisms. Since cellular adhesion dynamics play a critical role in cell migration, we investigated the effects of triterpenoids on focal adhesion morphology. Using immunofluorescence microscopic analysis of focal adhesion markers, paxillin and Focal Adhesion Kinase (FAK), we found that cells that were treated with synthetic triterpenoids possessed enlarged focal adhesions. Interestingly, numerous focal adhesion related proteins including IQGAP1, paxillin, FAK and Glycogen Synthase Kinase 3 (GSK3) were identified as drug-binding proteins using pull down and mass spectrometry approaches. Therefore, we investigated if triterpenoids target these proteins and affect cell adhesion turnover to inhibit cell migration. We found that focal adhesion re-establishment was altered by triterpenoids while pre-existing focal adhesions remained largely unaffected. To further explore the underlying mechanism of triterpenoids on GSK3β dependent cell adhesion dynamics, we analyzed GSK3β activity. We found that triterpenoids stimulate the phosphorylation of GSK3β at serine 9, however, both FAK and paxillin phosphorylation was largely unaffected by the triterpenoids. In parallel studies, we observed that focal adhesion staining was enlarged with cells that were treated with the GSK3β inhibitors, lithium chloride and SB216763. In addition, GSK3β inhibition affected the localization of not only GSK3β but also IQGAP1, an important scaffolding protein involved in cell polarity. From our results, we postulate that synthetic triterpenoids may affect cell migration by targeting GSK3β, which in turns, inhibits its activity and displaces its localization from the leading edge. More importantly, GSK3β inhibition by the triterpenoids and by GSK3β inhibitors also lead to the displacement of IQGAP1 from the leading edge, which further suggests that triterpenoids may act via a GSK3β mechanism to affect focal adhesions and cell migration. 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 466. doi:1538-7445.AM2012-466

Abstract 5303: The role of the anti-hyperglycemic drug metformin in regulating tumor angiogenesis

Abstract Metformin (dimethylbiguanide) is used as a first-line therapy for the management of type 2 diabetes. Recently, metformin has hit the headlines as anti-cancer drug. Metformin is known to work in part through activation of AMP-activated protein kinase (AMPK). AMPK is involved in cancer cell growth and metabolism by modulation of gene expression and translation through the AMPK/ mTOR/S6K1 axis. In order for a solid tumor to grow and to disseminate, an efficient angiogenesis is required, becoming in this way one of the most successful targets not only in cancer therapy but also in prevention. Angiogenesis is the formation of new blood vessels from pre-existing ones. Some evidences have been collected that metformin activates AMPK in human umbilical vein endothelial cells (HUVEC). We aimed to better characterize the mechanism of action by which metformin can affect neo-angiogenesis. We carried out HUVEC morphogenesis assay in matrigel in presence of metformin. We found that the compound affects normal tube formation. Moreover we assessed the effect of metformin on cell viability by a MTT assay in presence of different doses of the drug. We also observed that this compound affected endothelial cell proliferation. This finding was corroborated by real time PCR data showing that in HUVEC metformin treatment induced downregulation of Cyclin D1. The lower proliferation rate was not associated to the induction of apoptotic pathway, as indicated by Annexin V/7AAD staining and FACS analysis. In order to evaluate to what extent this compound can effect endothelial cell migration and invasion of a reconstitute basement membrane in vitro, HUVEC were cultured in a Boyden chamber and showed less invasiveness in presence of metformin compare to untreated cells. Futhertrmore we investigated the effect of the drug when administered to the cells along with other antiangiogenic compounds used in chemotherapy, e.g. the synthetic triterpenoid CDDO. The combination of two drugs demonstrated synergistic effects on cells organizing in tubule-like structures in a morphogenesis assay. Finally, we examined the activity of metformin on endothelial cells by microarray gene expression profiling. Although we are still in the validation process, preliminary results suggest that metformin decrease the expression of several genes involved in biosynthetic process and in the response to stimuli, supporting its anti-proliferative effect. On the other hand it also seems to induce a pro-inflammatory setting. This result hints that the effect of the chemotherapy can be potentiated by metformin, suggesting a possible use of metformin in combination with chemotherapeutic agent in order to lower the risk of side effect following high dosage treatments. Our results indicate an effective role of metformin in inhibiting neoangiogenesis by which it may exert or, at least, support its anti-tumor effect. 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 5303. doi:1538-7445.AM2012-5303

The mitochondrial ATP-dependent Lon protease: a novel target in lymphoma death mediated by the synthetic triterpenoid CDDO and its derivatives

AbstractSynthetic triterpenoids are multitarget compounds exhibiting promise as preventative and therapeutic agents for cancer. Their proposed mechanism of action is by forming Michael adducts with reactive nucleophilic groups on target proteins. Our previous work demonstrates that the 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid (CDDO) and its derivatives promote B-lymphoid cell apoptosis through a mitochondria-mediated pathway linked to mitochondrial protein aggregation. As one function of the Lon protease is to eliminate abnormal mitochondrial proteins, we hypothesized that CDDO-induced protein aggregation and lymphoma apoptosis occur by inactivating this enzyme. Here, we show that CDDO and its derivatives directly and selectively inhibit Lon. CDDO blocks Lon-mediated proteolysis in biochemical and cellular assays, but does not inhibit the 20S proteasome. Furthermore, a biotinylated-CDDO conjugate modifies mitochondrial Lon. A striking common phenotype of CDDO-treated lymphoma cells and Lon-knockdown cells is the accumulation of electron-dense aggregates within mitochondria. We also show that Lon protein levels are substantially elevated in malignant lymphoma cells, compared with resting or activated B cells. Finally, we demonstrate that Lon knockdown leads to lymphoma cell death. Together, these findings suggest that Lon inhibition plays a contributory role in CDDO-induced lymphoma cell death, and support the concept that mitochondrial Lon is a novel anticancer drug target.

Targeted inhibition of tumor proliferation, survival, and metastasis by pentacyclic triterpenoids: Potential role in prevention and therapy of cancer

Over the last two decades, extensive research on plant-based medicinal compounds has revealed exciting and important pharmacological properties and activities of triterpenoids. Fruits, vegetables, cereals, pulses, herbs and medicinal plants are all considered to be biological sources of these triterpenoids, which have attracted great attention especially for their potent anti-inflammatory and anti-cancer activities. Published reports in the past have described the molecular mechanism(s) underlying the various biological activities of triterpenoids which range from inhibition of acute and chronic inflammation, inhibition of tumor cell proliferation, induction of apoptosis, suppression of angiogenesis and metastasis. However systematic analysis of various pharmacological properties of these important classes of compounds has not been done. In this review, we describe in detail the pre-clinical chemopreventive and therapeutic properties of selected triterpenoids that inhibit multiple intracellular signaling molecules and transcription factors involved in the initiation, progression and promotion of various cancers. Molecular targets modulated by these triterpenoids comprise, cytokines, chemokines, reactive oxygen intermediates, oncogenes, inflammatory enzymes such as COX-2, 5-LOX and MMPs, anti-apoptotic proteins, transcription factors such as NF-κB, STAT3, AP-1, CREB, and Nrf2 (nuclear factor erythroid 2-related factor) that regulate tumor cell proliferation, transformation, survival, invasion, angiogenesis, metastasis, chemoresistance and radioresistance. Finally, this review also analyzes the potential role of novel synthetic triterpenoids identified recently which mimic natural triterpenoids in physical and chemical properties and are moving rapidly from bench to bedside research.