Oleanane triterpenoid CDDO-Me inhibits growth and induces apoptosis in prostate cancer cells by independently targeting pro-survival Akt and mTOR

Enhanced Anti-cancer Potency Using a Combination of Oleanolic Acid and Maslinic Acid to Control Treatment Resistance in Breast Cancer

Purpose

The phosphatidylinositol 3-kinase/AKT/mammalian target of rapamycin (PI3K/AKT/ mTOR) pathway is a complex intracellular metabolic pathway that leads to cell growth and tumor proliferation and plays a key role in drug resistance in breast cancer. Therefore, the anti-cancer effects of oleanolic acid (OA), maslinic acid (MA), and their combination were investigated to improve the performance of the treatment strategy.

Methods

We investigated the effect of OA and MA on cell viability using the WST-1 method. The synergistic effect of the combination was analyzed by isobologram analysis. In addition, the effects of the two compounds, individually and in combination, on apoptosis, autophagy, and the cell cycle were investigated in MCF7 cells. In addition, changes in the expression of PI3K/AKT/mTOR genes involved in apoptosis, cell cycle and metabolism were determined by quantitative RT-PCR.

Results

MA, OA, and a combination of both caused G0/G1 arrest. Apoptosis also increased in all treated groups. The autophagosomal LC3-II formation was induced 1.74-fold in the MA-treated group and 3.25-fold in the MA-OA-treated group. The combination treatment resulted in increased expression of genes such as GSK3B, PTEN, CDKN1B and FOXO3 and decreased expression of IGF1, PRKCB and AKT3 genes.

Conclusion

The results showed that the combination of these two substances showed the highest synergistic effect at the lowest dose and using MA-OA caused cancer cells to undergo apoptosis. The use of combination drugs may reduce the resistance of cancer cells to treatment.

Orthogonal Optimization, Characterization, and In Vitro Anticancer Activity Evaluation of a Hydrogen Peroxide-Responsive and Oxygen-Reserving Nanoemulsion for Hypoxic Tumor Photodynamic Therapy

Tumor hypoxia can seriously impede the effectiveness of photodynamic therapy (PDT). To address this issue, two approaches, termed in situ oxygen generation and oxygen delivery, were developed. The in situ oxygen generation method uses catalysts such as catalase to decompose excess H₂O₂ produced by tumors. It offers specificity for tumors, but its effectiveness is limited by the low H₂O₂ concentration often present in tumors. The oxygen delivery strategy relies on the high oxygen solubility of perfluorocarbon, etc., to transport oxygen. It is effective, but lacks tumor specificity. In an effort to integrate the merits of the two approaches, we designed a multifunctional nanoemulsion system named CCIPN and prepared it using a sonication-phase inversion composition-sonication method with orthogonal optimization. CCIPN included catalase, the methyl ester of 2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oic acid (CDDO-Me), photosensitizer IR780, and perfluoropolyether. Perfluoropolyether may reserve the oxygen generated by catalase within the same nanoformulation for PDT. CCIPN contained spherical droplets below 100 nm and showed reasonable cytocompatibility. It presented a stronger ability to generate cytotoxic reactive oxygen species and consequently destroy tumor cells upon light irradiation, in comparison with its counterpart without catalase or perfluoropolyether. This study contributes to the design and preparation of oxygen-supplementing PDT nanomaterials.

Synthetic oleanane triterpenoid derivative CDDO-Me disrupts cellular bioenergetics to suppress pancreatic ductal adenocarcinoma via targeting SLC1A5

To investigate the potential antitumor activity of synthetic triterpenoid, methyl-2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oate (CDDO-Me) in pancreatic ductal adenocarcinoma (PDAC), MTT cytotoxicity assay, and xenograft nude mice assay were performed to evaluate tumor growth in vitro and in vivo. Seahorse XFe96 bioenergetics analyzer was applied to determine aerobic glycolysis and mitochondrial respiration. Western blot and quantitative reverse transcription-polymerase chain reactions are used to detect protein and messenger RNA transcripts of SLC1A5 and metabolic enzymes. We confirmed the strong antitumor activity of CDDO-Me in suppressing PDAC growth. Mechanistically, we demonstrated CDDO-Me induced mitochondrial respiration and aerobic glycolysis dysfunction. We also verified CDDO-Me downregulated glutamine transporter SLC1A5, resulting in excessive reactive oxygen species (ROS) levels that suppressed tumor growth. Moreover, we confirmed that SLC1A5 depletion reduced the ratio of glutathione/oxidized glutathione. We also found CDDO-Me could inhibit N-linked glycosylation of SLC1A5, which promotes protease-mediated degradation. Finally, we confirmed SLC1A5 was significantly overexpressed in PDAC and closely correlated with the poor prognosis of PDAC patients. Our work uncovers CDDO-Me is effective at suppressing PDAC cell growth in vitro and in vivo and illuminates CDDO-Me caused excessive ROS and cellular bioenergetics disruption which contributed to CDDO-Me inhibited PDAC growth. Our data highlights CDDO-Me could be considered a potential compound for PDAC therapy, and SLC1A5 could be a novel biomarker for PDAC patients.

CDDO-Me Attenuates Clasmatodendrosis in CA1 Astrocyte by Inhibiting HSP25-AKT Mediated DRP1-S637 Phosphorylation in Chronic Epilepsy Rats

Clasmatodendrosis is one of the irreversible astroglial degeneration, which is involved in seizure duration and its progression in the epileptic hippocampus. Although sustained heat shock protein 25 (HSP25) induction leads to this autophagic astroglial death, dysregulation of mitochondrial dynamics (aberrant mitochondrial elongation) is also involved in the pathogenesis in clasmatodendrosis. However, the underlying molecular mechanisms of accumulation of elongated mitochondria in clasmatodendritic astrocytes are elusive. In the present study, we found that clasmatodendritic astrocytes showed up-regulations of HSP25 expression, AKT serine (S) 473 and dynamin-related protein 1 (DRP1) S637 phosphorylations in the hippocampus of chronic epilepsy rats. 2-Cyano-3,12-dioxo-oleana-1,9(11)-dien-28-oic acid methyl ester (CDDO-Me; bardoxolone methyl or RTA 402) abrogated abnormal mitochondrial elongation by reducing HSP25 upregulation, AKT S473- and DRP1 S637 phosphorylations. Furthermore, HSP25 siRNA and 3-chloroacetyl-indole (3CAI, an AKT inhibitor) abolished AKT-DRP1-mediated mitochondrial elongation and attenuated clasmatodendrosis in CA1 astrocytes. These findings indicate that HSP25-AKT-mediated DRP1 S637 hyper-phosphorylation may lead to aberrant mitochondrial elongation, which may result in autophagic astroglial degeneration. Therefore, our findings suggest that the dysregulation of HSP25-AKT-DRP1-mediated mitochondrial dynamics may play an important role in clasmatodendrosis, which would have implications for the development of novel therapies against various neurological diseases related to astroglial degeneration.

Review of novel tissue-based biomarkers for prostate cancer: towards personalised and targeted medicine

Background:

Prostate cancer is the most commonly diagnosed cancer in men and responsible for about 10% of all cancer mortality in both Canadian and American men. Currently, serum PSA level is the most commonly used test for the detection of prostate cancer, though the levels can also be elevated in benign conditions, has limited specificity and has a high rate of overdiagnosis and treatment of indolent disease. Consequently, in recent years, several investigations have been conducted to identify novel cancer biomarkers capable of both effective screening and diagnosis, as well as assisting to shift the diagnostic and treatment paradigm of prostate cancer towards more patient-specific and targeted medicine. The goal of this narrative review paper is to describe eleven novel and promising tissue-based biomarkers for prostate cancer capable to account for individual patient variabilities and have the potential for risk assessment, early detection and diagnosis, identification of patients who will benefit from a particular treatment and monitoring patient response to treatment.

Materials and methods:

We searched several databases from August to December 2020 for relevant studies published in English between 2000 and 2020 and reporting on tissue-based biomarkers for screening and early diagnosis, treatment and monitoring of prostate cancer.

Conclusions:

Emerging prostate cancer biomarkers have the potential to guide clinical decision-making since they have the potential to detect the disease early, measure the risk of developing the disease and the risk of progression, provide accurate information of patient response to a specific treatment and are capable of informing clinicians about the likely outcome of a cancer diagnosis independent of the treatment received. Therefore, the future holds promise for personalised and targeted medicine from prevention to diagnosis and treatment that considers the individual patient’s variabilities in the management of prostate cancer.

Oxidative stress and redox signaling in CRPC progression: therapeutic potential of clinically-tested Nrf2-activators

Androgen deprivation therapy (ADT) is the mainstay regimen in patients with androgen-dependent prostate cancer (PCa). However, the selection of androgen-independent cancer cells leads to castrate resistant prostate cancer (CRPC). The aggressive phenotype of CRPC cells underscores the need to elucidate mechanisms and therapeutic strategies to suppress CRPC outgrowth. Despite ADT, the activation of androgen receptor (AR) transcription factor continues via crosstalk with parallel signaling pathways. Understanding of how these signaling cascades are initiated and amplified post-ADT is lacking. Hormone deprivation can increase oxidative stress and the resultant reactive oxygen species (ROS) may activate both AR and non-AR signaling. Moreover, ROS-induced inflammatory cytokines may further amplify these redox signaling pathways to augment AR function. However, clinical trials using ROS quenching small molecule antioxidants have not suppressed CRPC progression, suggesting that more potent and persistent suppression of redox signaling in CRPC cells will be needed. The transcription factor Nrf2 increases the expression of numerous antioxidant enzymes and downregulates the function of inflammatory transcription factors, e.g., nuclear factor kappa B. We documented that Nrf2 overexpression can suppress AR-mediated transcription in CRPC cell lines. Furthermore, two Nrf2 activating agents, sulforaphane (a phytochemical) and bardoxolone-methyl (a drug in clinical trial) suppress AR levels and sensitize CRPC cells to anti-androgens. These observations implicate the benefits of potent Nrf2-activators to suppress the lethal signaling cascades that lead to CRPC outgrowth. This review article will address the redox signaling networks that augment AR signaling during PCa progression to CRPC, and the possible utility of Nrf2-activating agents as an adjunct to ADT.

Natural Compounds in Sex Hormone-Dependent Cancers: The Role of Triterpenes as Therapeutic Agents

Sex hormone-dependent cancers currently contribute to the high number of cancer-related deaths worldwide. The study and elucidation of the molecular mechanisms underlying the progression of these tumors was a double-edged sword, leading to the expansion and development of new treatment options, with the cost of triggering more aggressive, therapy resistant relapses. The interaction of androgen, estrogen and progesterone hormones with specific receptors (AR, ER, PR) has emerged as a key player in the development and progression of breast, ovarian, prostate and endometrium cancers. Sex hormone-dependent cancers share a common and rather unique carcinogenesis mechanism involving the active role of endogenous and exogenous sex hormones to maintain high mitotic rates and increased cell proliferation thus increasing the probability of aberrant gene occurrence and accumulation highly correlated with abnormal cell division and the occurrence of malignant phenotypes. Cancer related hormone therapy has evolved, currently being associated with the blockade of other signaling pathways often associated with carcinogenesis and tumor progression in cancers, with promising results. However, despite the established developments, there are still several shortcomings to be addressed. Triterpenes are natural occurring secondary metabolites biosynthesized by various pathways starting from squalene cyclization. Due to their versatile therapeutic potential, including the extensively researched antiproliferative effect, these compounds are most definitely a cornerstone in the research and development of new natural/semisynthetic anticancer therapies. The present work thoroughly describes the ongoing research related to the antitumor activity of triterpenes in sex hormone-dependent cancers. Also, the current review highlights both the biological activity of various triterpenoid compounds and their featured mechanisms of action correlated with important chemical structural features.

The role of natural products in revealing NRF2 function

Covering: up to 2020The transcription factor NRF2 is one of the body's major defense mechanisms, driving transcription of >300 antioxidant response element (ARE)-regulated genes that are involved in many critical cellular processes including redox regulation, proteostasis, xenobiotic detoxification, and primary metabolism. The transcription factor NRF2 and natural products have an intimately entwined history, as the discovery of NRF2 and much of its rich biology were revealed using natural products both intentionally and unintentionally. In addition, in the last decade a more sinister aspect of NRF2 biology has been revealed. NRF2 is normally present at very low cellular levels and only activated when needed, however, it has been recently revealed that chronic, high levels of NRF2 can lead to diseases such as diabetes and cancer, and may play a role in other diseases. Again, this "dark side" of NRF2 was revealed and studied largely using a natural product, the quassinoid, brusatol. In the present review, we provide an overview of NRF2 structure and function to orient the general reader, we will discuss the history of NRF2 and NRF2-activating compounds and the biology these have revealed, and we will delve into the dark side of NRF2 and contemporary issues related to the dark side biology and the role of natural products in dissecting this biology.

CDDO-Me Inhibits Microglial Activation and Monocyte Infiltration by Abrogating NFκB- and p38 MAPK-Mediated Signaling Pathways Following Status Epilepticus

Following status epilepticus (SE, a prolonged seizure activity), microglial activation, and monocyte infiltration result in the inflammatory responses in the brain that is involved in the epileptogenesis. Therefore, the regulation of microglia/monocyte-mediated neuroinflammation is one of the therapeutic strategies for avoidance of secondary brain injury induced by SE. 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid methyl ester (CDDO-Me; RTA 402) is an activator of nuclear factor-erythroid 2-related factor 2 (Nrf2), which regulates intracellular redox homeostasis. In addition, CDDO-Me has anti-inflammatory properties that suppress microglial proliferation and its activation, although the underlying mechanisms have not been clarified. In the present study, CDDO-Me ameliorated monocyte infiltration without vasogenic edema formation in the frontoparietal cortex (FPC) following SE, accompanied by abrogating monocyte chemotactic protein-1 (MCP-1)/tumor necrosis factor-α (TNF-α) expressions and p38 mitogen-activated protein kinase (p38 MAPK) phosphorylation. Furthermore, CDDO-Me inhibited nuclear factor-κB (NFκB)-S276 phosphorylation and microglial transformation, independent of Nrf2 expression. Similar to CDDO-Me, SN50 (an NFκB inhibitor) mitigated monocyte infiltration by reducing MCP-1 and p38 MAPK phosphorylation in the FPC following SE. Therefore, these findings suggest, for the first time, that CDDO-Me may attenuate microglia/monocyte-mediated neuroinflammation via modulating NFκB- and p38 MAPK-MCP-1 signaling pathways following SE.

The synthetic oleanane triterpenoid CDDO-Me binds and inhibits pyruvate kinase M2

BACKGROUND

The M2 isoform of the glycolytic enzyme pyruvate kinase (PKM2) is one of the key components in the Warburg effect, and an important regulator of cancer cell metabolism. Elevated PKM2 expression is a hallmark of numerous tumor types, making it a promising target for cancer therapy.

METHODS

Migration of H1299 lung tumor cells treated with synthetic oleanane triterpenoid derivatives CDDO-Me and CDDO-Im was monitored using scratch and transwell assays. Direct binding and inhibition of PKM2 activity by CDDO-Me was demonstrated by pull-down and activity assays. PKM2 localization in the absence and presence of CDDO-Me or CDDO-Im was determined by subcellular fractionation and immunofluorescence microscopy. Involvement of PKM2 in tumor cell migration was assessed using a stable PKM2 knockdown cell line.

RESULTS

We demonstrate that migration of H1299 lung tumor cells is inhibited by CDDO-Me and CDDO-Im in scratch and transwell assays. CDDO-Me binds directly and specifically to recombinant PKM2, leading to a reduction of its catalytic activity. PKM2 knockdown cells exhibit significantly lower migration compared to control cells when subjected to glucose and oxygen deprivation, but not under regular conditions.

CONCLUSIONS

The results suggest that PKM2 expression in a tumor-like environment contributes to cell migration, and that PKM2 activity can be down regulated by synthetic triterpenoid derivatives.

CDDO-Me Elicits Anti-Breast Cancer Activity by Targeting LRP6 and FZD7 Receptor Complex

Aberrant activation of the Wnt/β-catenin pathway leads to the development of multiple cancers, including breast cancer. Development of therapeutic agents against this signaling pathway is an urgent need. In this study, we found that 2-cyano-3, 12-dioxooleana-1, 9(11)-dien-28-oic acid-methyl ester (CDDO-Me) could inhibit Wnt/β-catenin signaling mainly through targeting the low-density lipoprotein receptor-related protein (LRP) 6 and Frizzled (FZD) 7 receptor complex. This compound induced the degradation and ubiquitination of LRP6 and Fzd7 via the lysosomal pathway. We further showed that CDDO-Me mediated the degradation of FZD7 in an LRP6 ectodomain-dependent manner. In breast cancer cells, treatment with CDDO-Me increased the degradation of LRP6 and FZD7 and reduced the levels of phosphorylated Disheveled (DVL) 2 and active β-catenin, resulting in the downregulation of Wnt target genes and several cancer stem cell (CSC) marker genes. In a murine xenograft bearing mouse mammary tumor virus (MMTV)-Wnt1-driven mammary tumor, administration of CDDO-Me significantly inhibited tumor growth and was accompanied by reduced expression of phosphorylated and total LRP6, phosphorylated and unphosphorylated DVL2, active β-catenin, several Wnt target genes, and CSC marker genes. Collectively, the results of our study present that CDDO-Me is a potent Wnt/β-catenin signaling inhibitor that may be a promising therapeutic agent against breast cancer. SIGNIFICANCE STATEMENT: Blocking the membrane receptor complex consisting of low-density lipoprotein receptor-related protein (LRP) 6 and Frizzled (FZD) 7 may help developing therapeutic approaches for cancers, including breast cancers. Our study indicates that 2-cyano-3, 12-dioxooleana-1, 9(11)-dien-28-oic acid-methyl ester (CDDO-Me) can inhibit Wnt/β-catenin signaling by inducing the ubiquitination and degradation of LRP6/FZD7 membrane receptor complex via a lysosomal pathway. We also found that the ectodomain of LRP6 is essential for CDDO-Me-induced FZD7 degradation. Defining CDDO-Me as a novel inhibitor of Wnt/β-catenin signaling, our results provide insight into the mechanism of its anticancer activity.

Location, Orientation and Aggregation of Bardoxolone-ME, CDDO-ME, in a Complex Phospholipid Bilayer Membrane

Bardoxolone methyl (CDDO-Me), a synthetic derivative of the naturally occurring triterpenoid oleanolic acid, displays strong antioxidant, anticancer and anti-inflammatory activities, according to different bibliographical sources. However, the understanding of its molecular mechanism is missing. Furthermore, CDDO-Me has displayed a significant cytotoxicity against various types of cancer cells. CDDO-Me has a noticeable hydrophobic character and several of its effects could be attributed to its ability to be incorporated inside the biological membrane and therefore modify its structure and specifically interact with its components. In this study, we have used full-atom molecular dynamics to determine the location, orientation and interactions of CDDO-Me in phospholipid model membranes. Our results support the location of CDDO-Me in the middle of the membrane, it specifically orients so that the cyano group lean towards the phospholipid interface and it specifically interacts with particular phospholipids. Significantly, in the membrane the CDDO-Me molecules specifically interact with POPE and POPS. Moreover, CDDO-Me does not aggregates in the membrane but it forms a complex conglomerate in solution. The formation of a complex aggregate in solution might hamper its biological activity and therefore it should be taken into account when intended to be used in clinical assays. This work should aid in the development of these molecules opening new avenues for future therapeutic developments.

Bardoxolone-Methyl (CDDO-Me) Suppresses Androgen Receptor and Its Splice-Variant AR-V7 and Enhances Efficacy of Enzalutamide in Prostate Cancer Cells

Androgen receptor (AR) signaling is fundamental to prostate cancer (PC) progression, and hence, androgen deprivation therapy (ADT) remains a mainstay of treatment. However, augmented AR signaling via both full length AR (AR-FL) and constitutively active AR splice variants, especially AR-V7, is associated with the recurrence of castration resistant prostate cancer (CRPC). Oxidative stress also plays a crucial role in anti-androgen resistance and CRPC outgrowth. We examined whether a triterpenoid antioxidant drug, Bardoxolone-methyl, known as CDDO-Me or RTA 402, can decrease AR-FL and AR-V7 expression in PC cells. Nanomolar (nM) concentrations of CDDO-Me rapidly downregulated AR-FL in LNCaP and C4-2B cells, and both AR-FL and AR-V7 in CWR22Rv1 (22Rv1) cells. The AR-suppressive effect of CDDO-Me was evident at both the mRNA and protein levels. Mechanistically, acute exposure (2 h) to CDDO-Me increased and long-term exposure (24 h) decreased reactive oxygen species (ROS) levels in cells. This was concomitant with an increase in the anti-oxidant transcription factor, Nrf2. The anti-oxidant N-acetyl cysteine (NAC) could overcome this AR-suppressive effect of CDDO-Me. Co-exposure of PC cells to CDDO-Me enhanced the efficacy of a clinically approved anti-androgen, enzalutamide (ENZ), as evident by decreased cell-viability along with migration and colony forming ability of PC cells. Thus, CDDO-Me which is in several late-stage clinical trials, may be used as an adjunct to ADT in PC patients.

Synthesis and Anticancer Activity of CDDO and CDDO-Me, Two Derivatives of Natural Triterpenoids

Triterpenoids are natural compounds synthesized by plants through cyclization of squalene, known for their weak anti-inflammatory activity. 2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oic acid (CDDO), and its C28 modified derivative, methyl-ester (CDDO-Me, also known as bardoxolone methyl), are two synthetic derivatives of oleanolic acid, synthesized more than 20 years ago, in an attempt to enhance the anti-inflammatory behavior of the natural compound. These molecules have been extensively investigated for their strong ability to exert antiproliferative, antiangiogenic, and antimetastatic activities, and to induce apoptosis and differentiation in cancer cells. Here, we discuss the chemical properties of natural triterpenoids, the pathways of synthesis and the biological effects of CDDO and its derivative CDDO-Me. At nanomolar doses, CDDO and CDDO-Me have been shown to protect cells and tissues from oxidative stress by increasing the transcriptional activity of the nuclear factor (erythroid-derived 2)-like 2 (Nrf2). At doses higher than 100 nM, CDDO and CDDO-Me are able to modulate the differentiation of a variety of cell types, both tumor cell lines or primary culture cell, while at micromolar doses these compounds exert an anticancer effect in multiple manners; by inducing extrinsic or intrinsic apoptotic pathways, or autophagic cell death, by inhibiting telomerase activity, by disrupting mitochondrial functions through Lon protease inhibition, and by blocking the deubiquitylating enzyme USP7. CDDO-Me demonstrated its efficacy as anticancer drugs in different mouse models, and versus several types of cancer. Several clinical trials have been started in humans for evaluating CDDO-Me efficacy as anticancer and anti-inflammatory drug; despite promising results, significant increase in heart failure events represented an obstacle for the clinical use of CDDO-Me.

Nutraceuticals and "Repurposed" Drugs of Phytochemical Origin in Prevention and Interception of Chronic Degenerative Diseases and Cancer

BACKGROUND

Chronic, degenerative diseases are often characterized by inflammation and aberrant angiogenesis. For these pathologies, including rheumatoid arthritis, cardiovascular and autoimmune diseases, cancer, diabetes, and obesity, current therapies have limited efficacy.

OBJECTIVES

The validation of novel (chemo)preventive and interceptive approaches, and the use of new or repurposed agents, alone or in combination with registered drugs, are urgently required.

RESULTS

Phytochemicals (triterpenoids, flavonoids, retinoids) and their derivatives, nonsteroidal anti-inflammatory drugs (aspirin) as well as biguanides (metformin and phenformin) originally developed from phytochemical backbones, are multi-target agents showing antiangiogenic and anti-anti-inflammatory proprieties. Many of them target AMPK and metabolic pathways such as the mTOR axis. We summarize the beneficial effects of several compounds in conferring protection and supporting therapy, and as a paradigm, we present data on terpenoids & biquanides on beer hop xanthohumol and hydroxytryrosol from olive mill waste waters.

CONCLUSIONS

These molecules could be employed for combinatorial chemoprevention and interception approaches or chemoprevention/therapy regimens for cancer and other chronic complex diseases.

Synthetic Triterpenoid CDDO-Me Inhibits Proliferation, Migration, and Invasion in GBM8401 and GBM8901

Objectives:

We determined the anticancer potency of CDDO-Me in glioblastoma cell lines and the underlying mechanisms in vitro.

Summary:

CDDO-Me is a synthetic triterpenoid with more potent anticancer and cancer preventive actions compared with the original triterpenoid CDDO.

Methods:

Two glioblastoma cell lines, GBM8401 and GBM8901, were utilized to test the effect of CDDO-Me on cell viability, cell migration, and cell invasion using the MTT, wound healing, and transwell migration assays, respectively. Additionally, Western blotting was used to determine the protein expression levels of N-cadherin, cyclin D1, and vascular endothelial growth factor.

Results:

At nanomolar concentrations, CDDO-Me inhibited proliferation, migration, and invasion in both cell lines. In addition, CDDO-Me exhibited a dose-dependent downregulation in the protein levels of N-cadherin, cyclin D1, and vascular endothelial growth factor in GBM8401 and GBM8901 cells.

Conclusions:

CDDO-Me exhibited anticancer effects at low nanomolar concentrations and should be considered as a potential chemotherapeutic agent for glioblastoma.

HDAC and Ku70 axis- an effective target for apoptosis induction by a new 2-cyano-3-oxo-1,9-dien glycyrrhetinic acid analogue

Methyl 2-cyano-3,12-dioxo-18β-olean-1,9(11)-dien-30-oate (CDODO-Me, 10d) derived from glycyrrhetinic acid and methyl-2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid (CDDO-Me) derived from oleanoic acid are potent apoptosis inducers developed to clinical trials. Both compounds have high affinity for reduced  glutathione (GSH), which needs to be overcome to improve their target selectivity. We generated a new 10d analogue methyl 2-cyano-3-oxo-18β-olean-1,9(11), 12-trien-30-oate (COOTO, 10e), which retains high apoptosis inducing ability, while displaying decreased affinity for GSH, and explored the acting targets. We found that it induces Noxa level, reduces c-Flip level and causes Bax/Bak activation. Silencing of either Noxa or Bak significantly attenuated apoptosis induction of 10e. We linked these events due to targeting HDAC3/HDAC6 and Ku70 axis. 10e treatment reduced the levels of HDAC3 and HDAC6 with increased DNA damage/repair marker gamma-H2AX (γ-H2AX) and acetylated Ku70. c-Flip dissociates from acetylated Ku70 undergoing degradation, while Bax dissociates from acetylated Ku70 undergoing activation. Silencing of either HDAC3 or HDAC6 enhanced 10e-induced apoptosis. We reveal a new action cascade of this category of compounds that involves targeting of HADC3/6 proteins and Ku70 acetylation.

Bardoxolone methyl induces neuritogenesis in Neuro2a cells

BACKGROUND

Bardoxolone methyl (RTA 402, CDDOMe) has been long known for its anti-inflammatory and exceptional cytotoxic activity. The biological responses to CDDOMe are truly dose dependent. And owing to the structural modifications introduced in its parent molecule oleanolic acid, CDDOMe is able to form reversible adducts with cellular proteins containing redox sensitive cysteine residues. This nature of CDDOMe makes it a multifunctional molecule targeting multiple signaling pathways. This study was initiated to study the response of Neuro2a, a mouse neuroblastoma cell line to CDDOMe.

METHODS

Neuro2a cells were treated with CDDOMe and all trans retinoic acid (ATRA) for 4days and observed for neurite outgrowth. The neurite length was estimated using ImageJ software (Neuron growth plugin). Cell viability was investigated using MTT dye reduction and trypan blue dye exclusion method. Gene expression of differentiation markers was analyzed using quantitative PCR. Cellular localization of Tuj1 and synaptophysin in differentiated Neuro2a cells was observed using immunofluorescence.

RESULTS

CDDOMe ceased proliferation and induced dramatic neurite outgrowth in Neuro2a cells. These morphological changes were accompanied by time dependent increase in the mRNA levels of tyrosine hydroxylase, neurofilament 200 and synaptophysin. Besides, cytoskeleton protein Tuj1 and the synaptic vesicle protein synaptophysin were also observed to be localized in the neurites induced by CDDOMe.

CONCLUSIONS

These early shreds of evidence suggest that CDDOMe induces differentiation in Neuro2a cells at concentrations ranging from 0.2 to 0.4μM and indeed contributes the existing knowledge on CDDOMe induced activities in cells.

Bardoxolone methyl (CDDO-Me or RTA402) induces cell cycle arrest, apoptosis and autophagy via PI3K/Akt/mTOR and p38 MAPK/Erk1/2 signaling pathways in K562 cells

Chronic myeloid leukemia (CML) treatment remains a challenge due to drug resistance and severe side effect, rendering the need on the development of novel therapeutics. CDDO-Me (Bardoxolone methyl), a potent Nrf2 activator and NF-κB inhibitor, is a promising candidate for cancer treatment including leukemia. However, the underlying mechanism for CDDO-Me in CML treatment is unclear. This study aimed to evaluate the molecular interactome of CDDO-Me in K562 cells using the quantitative proteomics approach stable-isotope labeling by amino acids in cell culture (SILAC) and explore the underlying mechanisms using cell-based functional assays. A total of 1,555 proteins responded to CDDO-Me exposure, including FANCI, SRPK2, XPO5, HP1BP3, NELFCD, Na⁺,K⁺-ATPase 1, etc. in K562 cells. A total of 246 signaling pathways and 25 networks regulating cell survival and death, cellular function and maintenance, energy production, protein synthesis, response to oxidative stress, and nucleic acid metabolism were involved. Our verification experiments confirmed that CDDO-Me down-regulated Na⁺,K⁺-ATPase α1 in K562 cells, and significantly arrested cells in G₂/M and S phases, accompanied by remarkable alterations in the expression of key cell cycle regulators. CDDO-Me caused mitochondria-, death receptor-dependent and ER stress-mediated apoptosis in K562 cells, also induced autophagy with the suppression of PI3K/Akt/mTOR signaling pathway. p38 MAPK/Erk1/2 signaling pathways contributed to both apoptosis- and autophagy-inducing effects of CDDO-Me in K562 cells. Taken together, these data demonstrate that CDDO-Me is a potential anti-cancer agent that targets cell cycle, apoptosis, and autophagy in the treatment of CML.

Transcriptomic and proteomic insight into the effects of a defined European mistletoe extract in Ewing sarcoma cells reveals cellular stress responses

BACKGROUND

The hydrophobic triterpenes, oleanolic and betulinic acid as well as the hydrophilic mistletoe lectins and viscotoxins possess anticancer properties. They do all occur in combination in European mistletoe (Viscum album L.). Commercial Viscum album L. extracts are aqueous, excluding the insoluble triterpenes. We have previously shown that mistletoe lectins and triterpene acids are effective against Ewing sarcoma in vitro, ex vivo and in vivo.

METHODS

We recreated a total mistletoe effect (viscumTT) by combining an aqueous extract (viscum) and a triterpene extract (TT) solubilised with cyclodextrins and analysed the effects of viscumTT and the single extracts on TC-71 Ewing sarcoma cells in vitro by transcriptomic and proteomic profiling.

RESULTS

Treatment with the extracts strongly impacted Ewing sarcoma cell gene and protein expression. Apoptosis-associated and stress-activated genes were upregulated, proteasomal protein abundance enhanced and ribosomal and spliceosomal proteins downregulated. The mechanism of action of viscum, TT and viscumTT in TC-71 and MHH-ES-1 cells suggests the involvement of the unfolded protein response. While viscum and viscumTT extract treatment indicate response to oxidative stress and activation of stress-mediated MAPK signalling, TT extract treatment suggests the involvement of TLR signalling and autophagy.

CONCLUSIONS

Since the combinatory extract viscumTT exerts highly effective pro-apoptotic effects on Ewing sarcoma cells in vitro, this phytopolychemotherapy could be a promising adjuvant therapeutic option for paediatric patients with Ewing sarcoma.

CDDO-Me inhibits tumor growth and prevents recurrence of pancreatic ductal adenocarcinoma

Methyl-2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oate (CDDO-Me) has shown potent antitumorigenic activity against a wide range of cancer cell lines in vitro and inhibited the growth of liver, lung and prostate cancer in vivo. In the present study, we examined the antitumor activity of CDDO-Me for pancreatic ductal adenocarcinoma (PDAC) cells with and without activating K-ras mutations. Treatment of K-ras mutant MiaPaCa-2 and K-ras normal BxPC-3 cells with CDDO-Me elicited strong antiproliferative and proapop-topic responses in both cell lines in culture. The inhibition of cell proliferation and induction of apoptosis was accompanied by the inhibition of antiapoptotic/prosurvival p-Akt, NF-κB and p-mTOR signaling proteins. For testing efficacy of CDDO-Me in vivo heterotopic and orthotopic xenografts were generated by implanting BxPC-3 and MiaPaCa-2 cells subcutaneously and in the pancreatic tail, respectively. Treatment with CDDO-Me significantly inhibited the growth of BxPC-3 xenografts and reduced the levels of p-Akt and p-mTOR in tumor tissue. In mice with orthotopic MiaPaCa-2 xenografts, treatment with CDDO-Me prolonged the survival of mice when administered following the surgical resection of tumors. The latter was attributed to the eradication of residual PDAC remaining after resection of tumors. These preclinical data demonstrate the potential of CDDO-Me for treating primary PDAC tumors and for preventing relapse/recurrence through the destruction of residual disease.

Ca2+ influx-mediated dilation of the endoplasmic reticulum and c-FLIPL downregulation trigger CDDO-Me-induced apoptosis in breast cancer cells

The synthetic triterpenoid 2-cyano-3, 12-dioxooleana-1, 9(11)-dien-C28-methyl ester (CDDO-Me) is considered a promising anti-tumorigenic compound. In this study, we show that treatment with CDDO-Me induces progressive endoplasmic reticulum (ER)-derived vacuolation in various breast cancer cells and ultimately kills these cells by inducing apoptosis. We found that CDDO-Me-induced increases in intracellular Ca2+ levels, reflecting influx from the extracellular milieu, make a critical contribution to ER-derived vacuolation and subsequent cell death. In parallel with increasing Ca2+ levels, CDDO-Me markedly increased the generation of reactive oxygen species (ROS). Interestingly, there exists a reciprocal positive-regulatory loop between Ca2+ influx and ROS generation that triggers ER stress and ER dilation in response to CDDO-Me. In addition, CDDO-Me rapidly reduced the protein levels of c-FLIPL (cellular FLICE-inhibitory protein) and overexpression of c-FLIPL blocked CDDO-Me-induced cell death, but not vacuolation. These results suggest that c-FLIPL downregulation is a key contributor to CDDO-Me-induced apoptotic cell death, independent of ER-derived vacuolation. Taken together, our results show that ER-derived vacuolation via Ca2+ influx and ROS generation as well as caspase activation via c-FLIPL downregulation are responsible for the potent anticancer effects of CDDO-Me on breast cancer cells.

A Natural Combination Extract of Viscum album L. Containing Both Triterpene Acids and Lectins Is Highly Effective against AML In Vivo

Aqueous Viscum album L. extracts are widely used in complementary cancer medicine. Hydrophobic triterpene acids also possess anti-cancer properties, but due to their low solubility they do not occur in significant amounts in aqueous extracts. Using cyclodextrins we solubilised mistletoe triterpenes (mainly oleanolic acid) and investigated the effect of a mistletoe whole plant extract on human acute myeloid leukaemia cells in vitro, ex vivo and in vivo. Single Viscum album L. extracts containing only solubilised triterpene acids (TT) or lectins (viscum) inhibited cell proliferation and induced apoptosis in a dose-dependent manner in vitro and ex vivo. The combination of viscum and TT extracts (viscumTT) enhanced the induction of apoptosis synergistically. The experiments demonstrated that all three extracts are able to induce apoptosis via caspase-8 and -9 dependent pathways with down-regulation of members of the inhibitor of apoptosis and Bcl-2 families of proteins. Finally, the acute myeloid leukaemia mouse model experiment confirmed the therapeutic effectiveness of viscumTT-treatment resulting in significant tumour weight reduction, comparable to the effect in cytarabine-treated mice. These results suggest that the combination viscumTT may have a potential therapeutic value for the treatment AML.

Nanoparticle delivery of CDDO-Me remodels the tumor microenvironment and enhances vaccine therapy for melanoma

Lipid-calcium-phosphate nanoparticle (NP) delivery of Trp2 peptide vaccine is one of the most effective vaccine strategies against melanoma. However, due to the immunosuppressive microenvironment in the tumor, the achievement of potent immune responses remains a major challenge. NP delivery systems provide an opportunity to deliver chemotherapy agent to modulate the tumor microenvironment (TME) and improve the vaccine activity. Anti-inflammatory triterpenoid methyl-2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oate (CDDO-Me) is a broad spectrum inhibitor of several signaling pathways that are important in both cancer cells and cells in the TME. Intravenous delivery of CDDO-Me using poly-lactic-glycolic-acid NP combination with subcutaneous Trp2 vaccine resulted in an increase of antitumor efficacy and apoptotic tumor tissue than Trp2 vaccine alone in B16F10 melanoma. There was a significant decrease of both Treg cells and MDSCs and a concomitant increase in the cytotoxic T-lymphocyte infiltration in TEM of the vaccinated animals. Also, CDDO-Me remodeled the tumor associated fibroblasts, collagen and vessel in TME, meanwhile, enhanced the Fas signaling pathway which could sensitize the tumor cells for cytotoxic T lymphocyte mediated killing. The combination of systemic induction of antigen-specific immune response using Trp2 nanovaccine and targeted modification of the TME with the NP delivered CDDO-Me offers a powerful combination therapy for melanoma.

Prevention of murine lupus nephritis by targeting multiple signaling axes and oxidative stress using a synthetic triterpenoid

OBJECTIVE

Current treatment options for lupus are far from optimal. Previously, we reported that phosphatidylinositol 3-kinase/Akt/mammalian target of rapamycin, MEK-1/ERK-1,2, p38, STAT-3, STAT-5, NF-κB, multiple Bcl-2 family members, and various cell cycle molecules were overexpressed in splenic B cells in an age-dependent and gene dose-dependent manner in mouse strains with spontaneous lupus. Since the synthetic triterpenoid methyl-2-cyano-3,12-dioxooleana-1,9-dien-28-oate (CDDO-Me) has been shown to inhibit AKT, MEK-1/2, and NF-κB, and to induce caspase-mediated apoptosis, we tested the therapeutic potential of this agent in murine lupus nephritis.

METHODS

The synthetic triterpenoid CDDO-Me or placebo was administered to 2-month-old B6.Sle1.Sle3 mice or MRL/lpr mice, which develop spontaneous lupus. All mice were phenotyped for disease.

RESULTS

CDDO-Me-treated mice exhibited significantly reduced splenic cellularity, with decreased numbers of both CD4+ T cells and activated CD69+/CD4+ T cells compared to the placebo-treated mice. These mice also exhibited a significant reduction in serum autoantibody levels, including anti-double-stranded DNA (anti-dsDNA) and antiglomerular antibodies. Finally, CDDO-Me treatment attenuated renal disease in mice, as indicated by reduced 24-hour proteinuria, blood urea nitrogen, and glomerulonephritis. At the mechanistic level, CDDO-Me treatment dampened MEK-1/2, ERK, and STAT-3 signaling within lymphocytes and oxidative stress. Importantly, the NF-E2-related factor 2 pathway was activated after CDDO-Me treatment, indicating that CDDO-Me may modulate renal damage in lupus via the inhibition of oxidative stress.

CONCLUSION

These findings underscore the importance of AKT/MEK-1/2/NF-κB signaling in engendering murine lupus. Our findings indicate that the blockade of multiple signaling nodes and oxidative stress may effectively prevent and reverse the hematologic, autoimmune, and pathologic manifestations of lupus.

Bardoxolone methyl (CDDO-Me) as a therapeutic agent: an update on its pharmacokinetic and pharmacodynamic properties

Triterpenoids have been used for medicinal purposes in many Asian countries because of their anti-inflammatory, antioxidant, antiproliferative, anticancer, and anticarcinogenic properties. Bardoxolone methyl, the C-28 methyl ester of 2-cyano-3,12-dioxoolean-1,9-dien-28-oic acid (CDDO) known as CDDO-Me or RTA 402, is one of the derivatives of synthetic triterpenoids. CDDO-Me has been used for the treatment of chronic kidney disease, cancer (including leukemia and solid tumors), and other diseases. In this review, we will update our knowledge of the clinical pharmacokinetics and pharmacodynamics of CDDO-Me, highlighting its clinical benefits and the underlying mechanisms involved. The role of the Kelch-like erythroid cell-derived protein with CNC homology-associated protein 1 (Keap1)/the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway in the therapeutic activities of CDDO-Me will be discussed. CDDO-Me contains α,β-unsaturated carbonyl groups on rings A and C that can generate reversible adducts with the thiol groups of Cys residues in target proteins such as Keap1 and IκB kinase. At low nanomolar concentrations, CDDO-Me protects the cells against oxidative stress via inhibition of reactive oxygen species generation, while CDDO-Me at low micromolar concentrations induces apoptosis by increasing reactive oxygen species and decreasinging intracellular glutathione levels. Through Keap1/Nrf2 and nuclear factor-κB pathways, this agent can modulate the activities of a number of important proteins that regulate inflammation, redox balance, cell proliferation and programmed cell death. In a Phase I trial in cancer patients, CDDO-Me was found to have a slow and saturable oral absorption, a relatively long terminal phase half-life (39 hours at 900 mg/day), nonlinearity (dose-dependent) at high doses (600-1,300 mg/day), and high interpatient variability. As a multifunctional agent, CDDO-Me has improved the renal function in patients with chronic kidney disease associated with type 2 diabetes. CDDO-Me has shown a promising anticancer effect in a Phase I trial. This agent is generally well tolerated, but it may increase adverse cardiovascular events. Presently, it is being further tested for the treatment of patients with chronic kidney disease, cancer, and pulmonary arterial hypertension.

Preclinical evidences toward the use of triterpenoid CDDO-Me for solid cancer prevention and treatment

Solid cancer remains a major cause of death in the world. As limited treatment options are currently available to patients with solid cancer, novel preventive control and effective therapeutic approaches are considered to be reasonable and decisive measures to combat this disease. The plant-derived triterpenoids, commonly used for medicinal purposes in many Asian countries, poses various pharmacological properties. A large number of triterpenoids exhibit cytotoxicity against a variety of cancer cells, and cancer preventive, as well as anticancer efficacy in preclinical animal models. To improve antitumor activity, some synthetic triterpenoid derivatives have been synthesized, including cyano-3,12-dioxooleana-1,9(11)- dien-28-oic (CDDO), its methyl ester (CDDO-Me), and imidazolide (CDDO-Im) derivatives. In this review, we will critically examine the current preclinical evidences of cancer preventive and therapeutic activity about one of the synthetic triterpenoids, CDDO-Me. Both in vitro and in vivo effects of this agent and related molecular mechanisms are presented.

Oleanolic acid and its synthetic derivatives for the prevention and therapy of cancer: preclinical and clinical evidence

Oleanolic acid (OA, 3β-hydroxyolean-12-en-28-oic acid) is a ubiquitous pentacyclic multifunctional triterpenoid, widely found in several dietary and medicinal plants. Natural and synthetic OA derivatives can modulate multiple signaling pathways including nuclear factor-κB, AKT, signal transducer and activator of transcription 3, mammalian target of rapamycin, caspases, intercellular adhesion molecule 1, vascular endothelial growth factor, and poly (ADP-ribose) polymerase in a variety of tumor cells. Importantly, synthetic derivative of OA, 2-cyano-3,12-dioxoolean-1,9-dien-28-oic acid (CDDO), and its C-28 methyl ester (CDDO-Me) and C28 imidazole (CDDO-Im) have demonstrated potent antiangiogenic and antitumor activities in rodent cancer models. These agents are presently under evaluation in phase I studies in cancer patients. This review summarizes the diverse molecular targets of OA and its derivatives and also provides clear evidence on their promising potential in preclinical and clinical situations.

Induction of Apoptosis in Pancreatic Cancer Cells by CDDO-Me Involves Repression of Telomerase through Epigenetic Pathways

Reactivation of telomerase in cancers provides an attractive target for developing novel agents to selectively destroy tumor cells. Methyl-2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oate (CDDO-Me), a synthetic oleanane triterpenoid, inhibited cell proliferation and induced apoptosis in pancreatic cancer cells at very low concentrations. The antiproliferative and apoptosis-inducing effects of CDDO-Me were associated with the inhibition of human telomerase reverse transcriptase (hTERT) mRNA, hTERT protein and reduction in hTERT telomerase activity. CDDO-Me inhibited multiple transcription factors that regulate hTERT expression positively (Sp1, c-Myc and NF-κB) and negatively (CTCF, E2F-1 and MAD1). CDDO-Me inhibited protein levels of DNA methyl transferases DNMT1 and DNMT3a, which also resulted in hypomethylation of hTERT promoter. In addition, transcriptionally active chromatin markers, such as acetylated histone H3 (Lys 9), acetylated histone H4, di-methyl H3 (Lys 4) and tri-methyl H3 (Lys 9) were all reduced in pancreatic cancer cells treated with CDDO-Me. Chromatin immunoprecipitation analysis showed decreased histone deacetylation and histone demethylation at hTERT promoter. Collectively, these results indicate that down-regulation of telomerase through epigenetic mechanisms plays a critical role in induction of apoptosis in pancreatic cancer cells by CDDO-Me.

Multifunctional pentacyclic triterpenoids as adjuvants in cancer chemotherapy: a review

The protective adjuvants in chemotherapy.

CDDO-Me: A Novel Synthetic Triterpenoid for the Treatment of Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDA) is one of the most lethal human malignancy with dismal prognosis and few effective therapeutic options. Novel agents that are safe and effective are urgently needed. Oleanolic acid-derived synthetic triterpenoids are potent antitumorigenic agents, but their efficacy or the mechanism of action for pancreatic cancer has not been adequately investigated. In this study, we evaluated the antitumor activity and the mechanism of action of methyl-2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oate (CDDO-Me), a oleanane-derived synthetic triterpenoid for human pancreatic cancer cell lines. CDDO-Me inhibited the growth of both K-ras mutated (MiaPaca2, Panc1 and Capan2) and wild-type K-ras (BxPC3) pancreatic cancer cells at very low concentrations. The growth inhibitory activity of CDDO-Me was attributed to the induction of apoptosis characterized by increased annexin-V-FITC binding and cleavage of PARP-1 and procaspases-3, -8 and-9. In addition, CDDO-Me induced the loss of mitochondrial membrane potential and release of cytochrome C. The antitumor activity of CDDO-Me was associated with the inhibition of prosurvival p-Akt, NF-κB and mammalian target of rapamycin (mTOR) signaling proteins and the downstream targets of Akt and mTOR, such as p-Foxo3a (Akt) and p-S6K1, p-eIF-4E and p-4E-BP1 (mTOR). Silencing of Akt or mTOR with gene specific-siRNA sensitized the pancreatic cancer cells to CDDO-Me, demonstrating Akt and mTOR as molecular targets of CDDO-Me for its growth inhibitory and apoptosis-inducing activity.

Prevention of Prostate Cancer with Oleanane Synthetic Triterpenoid CDDO-Me in the TRAMP Mouse Model of Prostate Cancer

2-Cyano-3,12-dioxooleana-1,9(11)-dien-28-oic acid (CDDO), a synthetic analog of oleanolic acid, and its C28 methyl ester derivative (CDDO-Me), have shown potent antitumorigenic activity against a wide range of cancer cell lines, including prostate cancer cells in vitro, and inhibited the development of liver and lung cancer in vivo. In the present study, we examined the efficacy of CDDO-Me in preventing the development and progression of prostate cancer in the transgenic adenocarinoma of the mouse prostate (TRAMP) model. CDDO-Me inhibited the growth of murine TRAMPC-1 prostate cancer cells by inducing apoptosis through the inhibition of antiapoptotic p-Akt, p-mTOR and NF-κB. Early intervention with CDDO-Me (7.5 mg/kg) initiated at five weeks of age for 20 wk inhibited the progression of the preneoplastic lesions (low-grade PIN and high-grade-PIN) to adenocarcinoma in the dorsolateral prostate (DLP) and ventral prostate (VP) lobes of TRAMP mice. Even delayed administration of CDDO-Me started at 12 wk of age for 12 wk inhibited the development of adenocarcimona of the prostate. Both early and late treatment with CDDO-Me inhibited the metastasis of tumor to the distant organs. Treatment with CDDO-Me inhibited the expression of prosurvival p-Akt and NF-κB in the prostate and knocking-down Akt in TRAMPC-1 tumor cells sensitized them to CDDO-Me. These findings indicated that Akt is a target for apoptoxicity in TRAMPC-1 cells in vitro and potentially a target of CDDO-Me for inhibition of prostate cancer in vivo.

The Antitumor Effects of Triterpenoid Saponins from the Anemone flaccida and the Underlying Mechanism

Anemone flaccida Fr. Schmidt, a family of ancient hopanoids, have been used as traditional Asian herbs for the treatments of inflammation and convulsant diseases. Previous study on HeLa cells suggested that triterpenoid saponins from Anemone flaccida Fr. Schmidt may have potential antitumor effect due to their apoptotic activities. Here, we confirmed the apoptotic activities of the following five triterpenoid saponins: glycoside St-I4a (1), glycoside St-J (2), anhuienoside E (3), hedera saponin B (4), and flaccidoside II (5) on human BEL-7402 and HepG2 hepatoma cell lines, as well as the model of HeLa cells treated with lipopolysaccharide (LPS). We found that COX-2/PGE2 signaling pathway, which plays key roles in the development of cancer, is involved in the antitumor activities of these saponins. These data provide the evidence that triterpenoid saponins can induce apoptosis via COX-2/PGE2 pathway, implying a preventive role of saponins from Anemone flaccida in tumor.

Inhibition of telomerase activity by oleanane triterpenoid CDDO-Me in pancreatic cancer cells is ROS-dependent

Methyl-2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oate (CDDO-Me) is a synthetic derivative of oleanolic acid, a triterpene, with apoptosis-inducing activity in a wide range of cancer cells. Induction of apoptosis by CDDO-Me is associated with the generation of reactive oxygen species (ROS) and inhibition of telomerase activity. In the present study, we investigated the role of ROS in inhibition of telomerase by CDDO-me. Treatment of MiaPaCa-2 and Panc-1 pancreatic cancer cell lines with CDDO-Me induced the production of hydrogen peroxide and superoxide anions and inhibited the telomerase activity. Pretreatment of cells with N-acetylcycsteine, a general purpose antioxidant or overexpression of glutathione peroxidase (GPx) or superoxide dismutase-1 (SOD-1) blocked the telomerase inhibitory activity of CDDO-Me. Furthermore, blocking ROS generation also prevented the inhibition of hTERT gene expression, hTERT protein production and expression of a number of hTERT-regulatory proteins by CDDO-Me (e.g., c-Myc, Sp1, NF-κB and p-Akt). Data also showed that Akt plays an important role in the activation of telomerase activity. Together, these data suggest that inhibition of telomerase activity by CDDO-Me is mediated through a ROS-dependent mechanism; however, more work is needed to fully understand the role of ROS in down-regulation of hTERT gene and hTERT-regulatory proteins by CDDO-Me.

Identification of unique sensitizing targets for anti-inflammatory CDDO-Me in metastatic melanoma by a large-scale synthetic lethal RNAi screening

CDDO-Me has been shown to exert potent anti-inflammatory activity for chronic kidney disease and antitumor activity for several tumors, including melanoma, in early clinical trials. To improve CDDO-Me response in melanoma, we utilized a large-scale synthetic lethal RNAi screen targeting 6000 human druggable genes to identify targets that would sensitize melanoma cells to CDDO-Me. Based on screening results, five unique genes (GNPAT, SUMO1, SPINT2, FLI1, and SSX1) significantly potentiated the growth inhibitory effects of CDDO-Me and induced apoptosis in A375, a BRAF mutated melanoma line (P < 0.001). These five genes were then individually validated as targets to potentiate CDDO-Me activity, and related downstream signaling pathways of these genes were analyzed. In addition, the levels of phosphorylated Erk1/2, Akt, GSK-2, and PRAS40 were dramatically decreased by downregulating each of these five genes separately, suggesting a set of common mediators. Our findings indicate that GNPAT, SUMO1, SPINT2, FLI1, and SSX1 play critical roles in synergy with inflammation pathways in modulating melanoma cell survival and could serve as sensitizing targets to enhance CDDO-Me efficacy in melanoma growth control.

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.

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.

A new development of triterpene acid-containing extracts from Viscum album L. displays synergistic induction of apoptosis in acute lymphoblastic leukaemia

OBJECTIVES

Aqueous Viscum album L. extracts are widely used for anti-cancer therapies. Due to their low solubility, triterpenes (which are known to act on cancers), do not occur in aqueous extracts in significant amounts. Using cyclodextrins, we have found it possible to solubilize mistletoe triterpene acids and to determine their effects on acute lymphoblastic leukaemia (ALL) in vitro and in vivo.

MATERIALS AND METHODS

A C.B-17/SCID model of pre-B ALL (NALM-6) was used to test efficacy and mechanisms of treatment with lectin- and triterpene acid containing preparations in vivo. Cytotoxicity of increasing concentrations of V. album L. preparations was assessed in vitro. Apoptosis was determined using mitochondrial membrane potential measurements, annexin V/PI, western blot analyses and caspase inhibitor assays.

RESULTS

Solubilized triterpene acid- or lectin-containing V. album L. extracts inhibited cell proliferation and demonstrated cytotoxic properties in vitro. Annexin V/PI and mitochondrial membrane potential assays indicated that dose-dependent induction of apoptosis was the main mechanism. Combination (viscumTT) of lectin- (viscum) and triterpene-containing (TT) extracts resulted in greatest induction of apoptosis. Furthermore, caspase activity demonstrated that these extracts were able to induce apoptosis through both caspase-8 and -9 dependent pathways. In vivo experimentation showed that treatment of mice with viscumTT combination prolonged mean survival to 50.5 days compared to 39.3 days in the phosphate-buffered saline group.

CONCLUSION

Here for the first time, we have demonstrated that either solubilized triterpene acids or lectins and combinations thereof, induce dose-dependent apoptosis in the ALL cell line NALM-6 via caspase-8 and -9 dependent pathways.

Inhibition of cell proliferation and induction of apoptosis by CDDO-Me in pancreatic cancer cells is ROS-dependent

Oleanolic acid-derived synthetic triterpenoids are broad spectrum antiproliferative and antitumorigenic agents. In this study, we investigated the role of reactive oxygen species (ROS) in induction of apoptosis and inhibition of prosurvival Akt, NF-kappaB and mTOR signaling pro-teins by methyl-2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oate (CDDO-Me) in pancreatic cancer cells. Micromolar concentrations of CDDO-Me inhibited proliferation and induced apoptosis in MiaPaCa-2 and Panc-1 pancreatic cancer cells. Treatment with CDDO-Me caused the generation of hydrogen peroxide and superoxide anion and pretreatment of cells with NADPH oxidase inhibitor diphylene iodonium (DPI) or respiratory chain complex 1 inhibitor rotenone prevented ROS generation. Pretreatment with N-acetylcysteine (NAC) or overexpression of glutathione peroxidase (GPx) or superoxide dismutase-1 (SOD-1) blocked the antiproliferative effects of CDDO-Me. Likewise, NAC prevented the induction of apoptosis (annexin V-FITC binding and cleavage of PARP-1 and procaspases-3,-8 and -9) and reversed the loss of mitochondrial membrane potential and release of cytochrome c from mitochondria by CDDO-Me. CDDO-Me down-regulated p-Akt, p-mTOR and NF-kappaB (p65) but increased the activation of Erk1/2 and NAC blocked the modulation of these cell signaling proteins by CDDO-Me. Thus, the results of this study indicate that the antiproliferative and apoptosis inducing effects of CDDO-Me are mediated through a ROS-dependent mechanism and the role of ROS in modulation of signaling proteins by CDDO-Me warrants further investigation.

Oleanane triterpenoid CDDO-Me inhibits Akt activity without affecting PDK1 kinase or PP2A phosphatase activity in cancer cells

Our previous studies have shown that methyl-2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oate (CDDO-Me), a oleanane synthetic triterpenoid induces apoptosis in prostate cancer cells by inhibiting the Akt/NF-κB/mTOR signaling cascade; however, the mechanism by which CDDO-Me inhibits Akt/NF-κB/mTOR signaling has remained undetermined. Present studies show that Akt plays a critical role in the response of prostate cancer cells to CDDO-Me. Silencing of Akt sensitized PC-3 cells to CDDO-Me, whereas its overexpression rendered them resistant to CDDO-Me. Evaluation of the effect of CDDO-Me on Akt which lies upstream of NF-κB and mTOR showed that CDDO-Me directly inhibits the Akt kinase activity in cell-free kinase activity assay and in vivo without modulating the activity of PDK1, the upstream kinase that phosphorylates and activates Akt. The inhibition of Akt activity resulted in inhibition of phosphorylation/inactivation of proapoptotic procaspase-9, Bad and Foxo3a. Further, inhibition of p-Akt by CDDO-Me was not attributable to an increase in the activity of protein phosphatase 2A (PP2A) or PH domain/leucine-rich repeat protein phosphatase1 (PHLPP1) both of which dephosphorylate p-Akt. These findings show that Akt is a direct target of CDDO-Me in the Akt/NF-κB/mTOR prosurvival signaling axis.

Proteomic analysis shows synthetic oleanane triterpenoid binds to mTOR

New multifunctional drugs that target multiple disease-relevant networks offer a novel approach to the prevention and treatment of many diseases. New synthetic oleanane triterpenoids (SO), such as CDDO (2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid) and its derivatives, are multifunctional compounds originally developed for the prevention and treatment of inflammation and oxidative stress. However, the protein binding partners and mechanisms of action of these SO are not yet fully understood. Here we characterize the putative target profile of one SO, CDDO-Imidazolide (CDDO-Im), by combining affinity purification with mass spectroscopic proteomic analysis to identify 577 candidate binding proteins in whole cells. This SO pharmaco-interactome consists of a diverse but interconnected set of signaling networks; bioinformatic analysis of the protein interactome identified canonical signaling pathways targeted by the SO, including retinoic acid receptor (RAR), estrogen receptor (ER), insulin receptor (IR), janus kinase/signal transducers and activators of transcription (JAK/STAT), and phosphatase and tensin homolog (PTEN). Pull-down studies then further validated a subset of the putative targets. In addition, we now show for the first time that the mammalian target of rapamycin (mTOR) is a direct target of CDDO-Im. We also show that CDDO-Im blocks insulin-induced activation of this pathway by binding to mTOR and inhibiting its kinase activity. Our basic studies confirm that the SO, CDDO-Im, acts on a protein network to elicit its pharmacological activity.

CDDO-imidazolide induces DNA damage, G2/M arrest and apoptosis in BRCA1-mutated breast cancer cells

Breast cancer-associated gene 1 (BRCA1) protein plays important roles in DNA damage and repair, homologous recombination, cell-cycle regulation, and apoptosis. The synthetic triterpenoid 1-[2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oyl]imidazole (CDDO-Imidazolide, CDDO-Im) is a promising anticancer and chemopreventive agent with potent antiproliferative and apoptotic activities against a wide variety of cancer types. However, the mechanisms responsible for the selective apoptotic effects of CDDO-Im in cancer cells remain elusive. In the present work, CDDO-Im induced G2/M arrest and apoptosis in BRCA1-mutated mammary tumor cell lines. Prior to the induction of apoptosis, CDDO-Im induced DNA damage and the phosphorylation of H2AX followed by activation of the DNA damage response. Moreover, CDDO-Im also induced the generation of reactive oxygen species (ROS), which is associated with the induction of DNA damage, in both mouse and human tumor cells containing a BRCA1 mutation. The inhibition of ROS generation by uric acid prevented the induction of DNA damage by CDDO-Im. Furthermore, treatment with CDDO-Im did not induce ROS in nonmalignant MCF-10A breast epithelial cells or in E18-14C-27 breast cancer cells with wild-type BRCA1 genes and was not cytotoxic to normal mouse 3T3 fibroblasts, highlighting a selective therapeutic potential of CDDO-Im for BRCA1-associated breast cancer cells. Altogether, our results show that CDDO-Im induces ROS and subsequent DNA damage, thereby facilitating the activation of the DNA damage checkpoint, G2/M arrest, and finally apoptosis in BRCA1-mutated cancer cells. The particular relevance of these findings to the chemoprevention of cancer is discussed. Cancer Prev Res; 4(3); 425-34. ©2011 AACR.

Inhibition of mTOR signaling by oleanolic acid contributes to its anti-tumor activity in osteosarcoma cells

Oleanolic acid (OA), a pentacyclic triterpenoid exhibits potent anti-tumor activity against many tumor cell lines. But the mechanisms through which OA inhibits osteosarcoma cells are not known. The mammalian target of rapamycin (mTOR) serves as a central regulator of cell growth, proliferation, survival, and metabolism by integrating intracellular and extracellular signals. In this study, we examined effects of OA on proliferation, cell cycle progression, apoptosis in osteosarcoma cells, and involvement of mTOR signaling in this process. OA inhibited cell proliferation and colony formation, induced G1 arrest in osteosarcoma MG63 and Saos-2 cells dose and time dependently. The protein level of cyclin D1, which plays critical role in G1 to S phase transition and servers as a downstream target of mTOR complex 1 (mTORC1) was down-regulated by OA. Phosphorylation of p70 ribosomal S6 kinase 1 (p70 S6K1) (T389) and S6 (S235/236), mediators of mTORC1 signaling in controlling protein translation and cell growth, was also inhibited by OA. Furthermore, OA inhibited phosphorylation of Akt, a pro-survival factor and substrate for mTORC2. Inactivation of Akt correlated with pro-apoptotic role of OA in osteosarcoma cells, as manifested by an increase in annexin V-FITC binding, cleavage of poly (ADP-ribose) polymerase (PARP) and activation of caspases 3. Our results suggest that OA is a promising agent for treatment of osteosarcoma and mTOR signaling may contribute to its anti-tumor effects on osteosarcoma cells.

Optimization of the balanced steady state free precession (bSSFP) pulse sequence for magnetic resonance imaging of the mouse prostate at 3T

INTRODUCTION

MRI can be used to non-invasively monitor tumour growth and response to treatment in mouse models of prostate cancer, particularly for longitudinal studies of orthotopically-implanted models. We have optimized the balanced steady-state free precession (bSSFP) pulse sequence for mouse prostate imaging.

METHODS

Phase cycling, excitations, flip angle and receiver bandwidth parameters were optimized for signal to noise ratio and contrast to noise ratio of the prostate. The optimized bSSFP sequence was compared to T1- and T2-weighted spin echo sequences.

RESULTS

SNR and CNR increased with flip angle. As bandwidth increased, SNR, CNR and artifacts such as chemical shift decreased. The final optimized sequence was 4 PC, 2 NEX, FA 50°, BW ±62.5 kHz and took 14-26 minutes with 200 µm isotropic resolution. The SNR efficiency of the bSSFP images was higher than for T1WSE and T2WSE. CNR was highest for T1WSE, followed closely by bSSFP, with the T2WSE having the lowest CNR. With the bSSFP images the whole body and organs of interest including renal, iliac, inguinal and popliteal lymph nodes were visible.

CONCLUSION

We were able to obtain fast, high-resolution, high CNR images of the healthy mouse prostate with an optimized bSSFP sequence.

Synthetic triterpenoid CDDO prevents the progression and metastasis of prostate cancer in TRAMP mice by inhibiting survival signaling

In an extension of our previous studies showing potent antitumorigenic activity of synthetic triterpenoids of oleanolic acid against prostate cancer cell lines, we examined the efficacy of 2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oic acid (CDDO) in preventing the development and/or progression of prostate cancer in the transgenic adenocarcinoma of the mouse prostate (TRAMP) model. Data show that oral gavage with CDDO (10 μmol/kg) for 20 weeks resulted in inhibition of the progression of preneoplastic lesions in the dorsolateral prostate and ventral prostate to adenocarcinoma without toxicity. CDDO also inhibited metastasis of tumor to the distant organs. Treatment with CDDO significantly inhibited cell proliferation, reduced the density of blood vessels and promoted apoptosis in the prostatic tissue. Further, Akt, NF-κB and NF-κB regulated Bcl-2, Bcl-xL, survivin and cIAP1 appear to be the molecular targets of CDDO for inhibiting the progression of prostate cancer in TRAMP mice. Thus, these studies show for the first time the potential of CDDO for chemoprevention of human prostate cancer.

The synthetic triterpenoid CDDO-Imidazolide suppresses experimental liver metastasis

Survival following diagnosis of liver metastasis remains poor and improved treatment strategies to combat liver metastases are needed. Synthetic triterpenoids, including 1-[2-cyano-3-,12-dioxooleana-1,9(11)-dien-28-oyl]imidazole (CDDO-Imidazolide or CDDO-Im), have been shown to inhibit primary tumor growth and lung metastasis in experimental models. Oral administration of CDDO-Im results in relatively high liver concentrations, suggesting that CDDO-Im may provide an approach to treatment of liver metastases. Here we assessed the effect of CDDO-Im on liver metastasis, using B16F1 (mouse melanoma) and HT-29 (human colon carcinoma) cells. In vitro, nanomolar concentrations of CDDO-Im arrested proliferation or induced cell death in both cell lines. In vivo, cells were injected via a surgically exposed mesenteric vein to target cells to the liver of mice. Mice were then treated with CDDO-Im (800 mg/kg diet) or vehicle control. Livers were removed at endpoint and metastatic burden was quantified by standard histology. In addition, a novel whole liver magnetic resonance imaging (MRI) technique was used to assess the effect of CDDO-Im on growing metastases as well as on non-dividing, solitary cancer cells present in the same livers. CDDO-Im treatment significantly decreased liver metastasis burden in both HT-29 (n = 8 treated, 10 control) and B16F1 (n = 15 treated, 16 control) injected mice (>60%, P < 0.05), but did not reduce the numbers of solitary B16F1 cancer cells (hypo-intensity) in the same livers (P = 0.9). This study demonstrates that CDDO-Im may be useful for the treatment metastatic liver disease as it successfully inhibits growth of actively proliferating liver metastases.