1-Methoxy-Canthin-6-One Induces c-Jun NH2-Terminal Kinase–Dependent Apoptosis and Synergizes with Tumor Necrosis Factor–Related Apoptosis-Inducing Ligand Activity in Human Neoplastic Cells of Hematopoietic or Endodermal Origin

Methyl Canthin-6-one-2-carboxylate Restrains the Migration/Invasion Properties of Fibroblast-like Synoviocytes by Suppressing the Hippo/YAP Signaling Pathway

Rheumatoid arthritis (RA) is an inflammatory condition that causes severe cartilage degradation and synovial damage in the joints with multiple systemic implications. Previous studies have revealed that fibroblast-like synoviocytes (FLSs) play a pivotal role in the pathogenesis of RA. The appropriate regulation of FLS function is an efficient approach for the treatment of this disease. In the present study, we explored the effects of methyl canthin-6-one-2-carboxylate (Cant), a novel canthin-6-one alkaloid, on the function of FLSs. Our data showed that exposure to Cant significantly suppressed RA-FLS migration and invasion properties in a dose-dependent manner. Meanwhile, pre-treatment with Cant also had an inhibitory effect on the release of several pro-inflammatory cytokines, including IL-6 and IL-1β, as well as the production of MMP1 and MMP3, which are important mediators of FLS invasion. In further mechanistic studies, we found that Cant had an inhibitory effect on the Hippo/YAP signaling pathway. Treatment with Cant suppressed YAP expression and phosphorylation on serine 127 and serine 397 while enhancing LATS1 and MST1 levels, both being important upstream regulators of YAP. Moreover, YAP-specific siRNA or YAP inhibition significantly inhibited wound healing as well as the migration and invasion rate of FLS cells, an impact similar to Cant treatment. Meanwhile, the over-expression of YAP significantly reversed the Cant-induced decline in RA-FLS cell migration and invasion, indicating that YAP was required in the inhibitory effect of Cant on the migration and invasion of RA-FLS cells. Additionally, supplementation of MMP1, but not MMP3, in culture supernatants significantly reversed the inhibitory effect of Cant on RA-FLS cell invasion. Our data collectively demonstrated that Cant may suppress RA-FLS migration and invasion by inhibiting the production of MMP1 via inhibiting the YAP signaling pathway, suggesting a potential of Cant for the further development of anti-RA drugs.

Novel Canthin-6-one Derivatives: Design, Synthesis, and Their Antiproliferative Activities via Inducing Apoptosis, Deoxyribonucleic Acid Damage, and Ferroptosis

A series of novel canthin-6-one (CO) derivatives (8a-l) were designed and synthesized by introducing different amide side chains at the C-2 position, and their water solubility, antiproliferative activity, and preliminary mechanism were investigated. Most compounds displayed high cytotoxicity exhibiting low-micromolar IC50 values against four human cancer cell lines, especially HT29 cells. Meanwhile, the water solubility of active CO derivatives was significantly improved. Among these compounds, compound 8h with the N-methyl piperazine group exhibiting the highest antiproliferative capability with an IC50 value of 1.0 μM against HT29 cells, which was 8.6-fold lower than that of CO. Furthermore, 8h could upregulate the levels of reactive oxygen species, leading to mitochondrial damage. In addition, 8h could promote cell apoptosis and DNA damage by regulating the expression of apoptosis-associated proteins (Bcl-2 and cleaved-caspase 3) and the DNA damage-associated protein (H2AX). Most importantly, 8h also exerted ferroptosis by reducing the GSH level and GPX4 expression as well as increasing the lipid peroxidation level. Thus, the novel CO derivative 8h with N-methylpiperazine represents a promising anticancer candidate and warrants a more intensive study.

Canthin-6-Ones: Potential Drugs for Chronic Inflammatory Diseases by Targeting Multiple Inflammatory Mediators

Chronic inflammatory disease (CID) is a category of medical conditions that causes recurrent inflammatory attacks in multiple tissues. The occurrence of CID is related to inappropriate immune responses to normal tissue substances and invading microbes due to many factors, such as defects in the immune system and imbalanced regulation of commensal microbes. Thus, effectively keeping the immune-associated cells and their products in check and inhibiting aberrant activation of the immune system is a key strategy for the management of CID. Canthin-6-ones are a subclass of β-carboline alkaloids isolated from a wide range of species. Several emerging studies based on in vitro and in vivo experiments reveal that canthin-6-ones may have potential therapeutic effects on many inflammatory diseases. However, no study has yet summarized the anti-inflammatory functions and the underlying mechanisms of this class of compounds. This review provides an overview of these studies, focusing on the disease entities and the inflammatory mediators that have been shown to be affected by canthin-6-ones. In particular, the major signaling pathways affected by canthin-6-ones, such as the NLR family pyrin domain containing 3 (NLRP3) inflammasome and the NF-κB signaling pathway, and their roles in several CIDs are discussed. Moreover, we discuss the limitations in studies of canthin-6-ones and provide possible solutions. In addition, a perspective that may suggest possible future research directions is provided. This work may be helpful for further mechanistic studies and possible therapeutic applications of canthin-6-ones in the treatment of CID.

Biological Activity of Naturally Derived Naphthyridines

Marine and terrestrial environments are rich sources of various bioactive substances, which have been used by humans since prehistoric times. Nowadays, due to advances in chemical sciences, new substances are still discovered, and their chemical structures and biological properties are constantly explored. Drugs obtained from natural sources are used commonly in medicine, particularly in cancer and infectious diseases treatment. Naphthyridines, isolated mainly from marine organisms and terrestrial plants, represent prominent examples of naturally derived agents. They are a class of heterocyclic compounds containing a fused system of two pyridine rings, possessing six isomers depending on the nitrogen atom's location. In this review, biological activity of naphthyridines obtained from various natural sources was summarized. According to previous studies, the naphthyridine alkaloids displayed multiple activities, i.a., antiinfectious, anticancer, neurological, psychotropic, affecting cardiovascular system, and immune response. Their wide range of activity makes them a fascinating object of research with prospects for use in therapeutic purposes.

Traditional uses, phytochemistry, and pharmacology of Ailanthus altissima (Mill.) Swingle bark: A comprehensive review

ETHNOPHARMACOLOGICAL RELEVANCE

The dried bark of Ailanthus altissima (Mill.) Swingle (BAA), commonly designated as "Chunpi" in Chinese, is extensively used as a common traditional medicine in China, Korea, and India. It has been used to treat multiple ailments, including asthma, epilepsy, spermatorrhea, bleeding, and ophthalmic diseases, for thousands of years.

AIM OF THE REVIEW

To present a comprehensive and constructive review on the phytochemistry, pharmacology, pharmacokinetics, traditional uses, quality control, and toxicology of BAA; to aid the assessment of the therapeutic potential of BAA; to guide researchers working on the development of novel therapeutic agents.

MATERIALS AND METHODS

Information related to BAA (from 1960 to 2020) was retrieved from a wide variety of electronic databases, such as PubMed, Web of Science, China Knowledge Resource Integrated Database, ScienceDirect, SciFinder, and Google Scholar. Additional information and materials were acquired from Chinese Medicine Monographs, the 2020 edition of the Chinese Pharmacopoeia, and several web sources, such as the official website of The Plant List and Flora of China. Additionally, perspectives for future investigations and applications of BAA were extensively explored.

RESULTS

Approximately 221 chemical compounds, including alkaloids, quassinoids, phenylpropanoids, triterpenoids, volatile oils, and other compounds, have been isolated and characterized from BAA; among these, the quassinoid ailanthone is the most typical. The crude extracts and active compounds of BAA have been reported to exert a wide range of pharmacological activities, such as antitumor, anti-inflammatory, antiviral, herbicidal, and insecticidal activities. Although BAA is safe when administered at a conventional dose, at higher doses, it exhibits toxicity due to the presence of quassinoids. Thus, more studies are required to evaluate the efficacy and safety of BAA.

CONCLUSION

Modern pharmacological studies have revealed that BAA, as a valuable medicinal resource, possesses the potential to treat a wide variety of ailments, especially, cancer and gastrointestinal inflammation. These studies present a wide range of perspectives for the development of new drugs related to BAA. However, only a few traditional uses are associated with the reported pharmacological activities of BAA and have been confirmed by preclinical and clinical studies. Moreover, the pharmacokinetics, toxicology, and quality control of BAA should be considered indispensable research topics.

Anticancer properties and mechanism of action of the quassinoid ailanthone

Ailanthone (AIT) is a quassinoid natural product isolated from the worldwide-distributed plant Ailanthus altissima. The drug displays multiple pharmacological properties, in particular significant antitumor effects against a variety of cancer cell lines in vitro. Potent in vivo activities have been evidenced in mice bearing hepatocellular carcinoma, nonsmall cell lung cancer and castration-resistant prostate cancer. This review focusses on the mechanism of action of AIT, notably to highlight the capacity of the drug to activate DNA damage responses, to inhibit the Hsp90 co-chaperone p23 and to modulate the expression of several microRNA. The interconnexion between these effects is discussed. The unique capacity of AIT to downregulate oncogenic miR-21 and to upregulate the tumor suppressor miRNAs miR-126, miR-148a, miR-195, and miR-449a is presented. AIT exploits several microRNAs to exert its anticancer effects in distinct tumor types. AIT is one of the rare antitumor natural products that binds to and strongly inhibits cochaperone p23, opening interesting perspectives to treat cancers. However, the toxicity profile of the molecule may limit its development as an anticancer drug, unless it can be properly formulated to prevent AIT-induced gastro-intestinal damages in particular. The antitumor properties of AIT and analogs are underlined, with the aim to encourage further pharmacological studies with this underexplored natural product and related quassinoids. HIGHLIGHTS: Ailanthone (AIT) is an anticancer quassinoid isolated from Ailanthus altissima It inhibits proliferation and induces cell death of many cancer cell types The drug activates DNA damage response and targets p23 cochaperone Up or downregulation of several microRNA by AIT contributes to the anticancer activity Analogs or specific formulations must be developed to prevent the toxicity of AIT.

Fluorescent Canthin-6-one Alkaloids from Simaba bahiensis: Isolation, Identification, and Cell-Labeling Properties

Canthin-6-one alkaloids, which are present in plants of the genus Simaba, are natural compounds that are capable of acting as fluorescent probes. However, the chemical composition and fluorescent properties of most species of this genus have not been analyzed. The objective of this study was to characterize the fluorescent properties of an extract of S. bahiensis and identify the chemical entities responsible for these properties. In addition, the cell-labeling properties of the fluorescent dye from A and of the isolated compounds were characterized by confocal fluorescence microscopy and flow cytometry. One quassinoid and three fluorescent alkaloids were isolated from S. bahiensis, all compounds were identified by using NMR spectroscopy and high-resolution mass spectrometry. Staining experiments and HPLC-FL analysis shown that canthin-6-one alkaloids are the main green fluorescent compounds in the analyzed dyes. All compounds evaluated showed a cytoplasmic marker with a residence time of 24 h. The present study is the first to describe the presence of canthin-6-one alkaloids in S. bahiensis, in addition to demonstrating promising cell-labeling properties of fluorescent compounds from S. bahiensis with broad emission wavelengths.

Anticancer Activity of Methanol Extract of Ficus carica Leaves and Fruits Against Proliferation, Apoptosis, and Necrosis in Huh7it Cells

The polyphenol plant extracts have previously been demonstrated to act as chemopreventive and anticancer agents. Ficus carica is a rich source of polyphenols, yet its antioxidant and anticancer activities remain poorly characterized. This study aimed to determine the anticancer activity of F carica leaf and fruit extracts by investigating their impact on proliferation, apoptosis, and Huh7it cell necrosis. Leaves and fruits were extracted using methanol, and the phytochemical contents were analyzed using Fourier-transform infrared spectroscopy. The antioxidant activity was measured using the 2,2-diphenyl-1-picrylhydrazyl method. Anticancer activities were examined through MTT (3-(4,5-dimethylthiazol-2yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay on Huh7it liver cancer cells. The apoptosis and necrosis conditions were examined using Annexin biomarkers V-PI and later analyzed in flow cytometry. F carica leaves and fruit examined were found to have strong antioxidant activities with IC₅₀ values of 7.9875 µg/mL and 13.402 µg/mL, respectively. MTT assay results indicated F carica leaves and fruit had IC₅₀ values >653 μg/mL and >2000 μg/mL, respectively. The flow cytometry analysis indicated a higher percentage of Huh7it apoptosis and necrosis in leaf extracts compared with fruit extracts. The difference in anticancer activity was attributed to differing compounds present in each extract.

Phytoelectrochemical analysis of Zanthoxylum chiloperone

INTRODUCTION

An innovative application of the voltammetry of microparticles methodology to characterize the phytochemical composition of extracts of different parts of Zanthoxylum chiloperone var. angustifolium Engl. is described.

OBJECTIVE

Characterize the phytochemical composition of extracts of different parts of plants by electrochemical methodologies.

METHODS

The voltammetry of microparticles methodology was applied to alcoholic extracts from leaves, seeds, fruits, roots and stem bark of Zanthoxylum chiloperone.

RESULTS

In contact with aqueous phosphate buffer, characteristic cathodic signals of its main natural products (canthin-6-one, 5-methoxycanthin-6-one and trans-avicennol) were recorded. The study of the voltammograns allows the estimation of the relative amounts of canthin-6-one, 5-methoxycanthin-6-one and trans-avicennol from the different parts of Zanthoxylum chiloperone.

CONCLUSION

The voltammetric responses of alcoholic extracts from different parts of Zanthoxylum chiloperone var. angustifolium allows their phytochemical characterization without need of sample pretreatment thus illustrating the capabilities of the voltammetry of microparticles methodology to increase the tools applied to phytochemical analysis. Copyright © 2016 John Wiley & Sons, Ltd.

Canthin-6-one induces cell death, cell cycle arrest and differentiation in human myeloid leukemia cells

BACKGROUND

Canthin-6-one is a natural product isolated from various plant genera and from fungi with potential antitumor activity. In the present study, we evaluate the antitumor effects of canthin-6-one in human myeloid leukemia lineages.

METHODS

Kasumi-1 lineage was used as a model for acute myeloid leukemia. Cells were treated with canthin-6-one and cell death, cell cycle and differentiation were evaluated in both total cells (Lin⁺) and leukemia stem cell population (CD34⁺CD38^-Lin^-/low).

RESULTS

Among the human lineages tested, Kasumi-1 was the most sensitive to canthin-6-one. Canthin-6-one induced cell death with apoptotic (caspase activation, decrease of mitochondrial potential) and necrotic (lysosomal permeabilization, double labeling of annexin V/propidium iodide) characteristics. Moreover, canthin-6-one induced cell cycle arrest at G₀/G₁ (7μM) and G₂ (45μM) evidenced by DNA content, BrdU incorporation and cyclin B1/histone 3 quantification. Canthin-6-one also promoted differentiation of Kasumi-1, evidenced by an increase in the expression of myeloid markers (CD11b and CD15) and the transcription factor PU.1. Furthermore, a reduction of the leukemic stem cell population and clonogenic capability of stem cells were observed.

CONCLUSIONS

These results show that canthin-6-one can affect Kasumi-1 cells by promoting cell death, cell cycle arrest and cell differentiation depending on concentration used.

GENERAL SIGNIFICANCE

Canthin-6-one presents an interesting cytotoxic activity against leukemic cells and represents a promising scaffold for the development of molecules for anti-leukemic applications, especially by its anti-leukemic stem cell activity.

Fruitful Decades for Canthin-6-ones from 1952 to 2015: Biosynthesis, Chemistry, and Biological Activities

In this review, more than 60 natural canthin-6-one alkaloids and their structures are considered. The biosynthesis, efficient and classic synthetic approaches, and biological activities of canthin-6-one alkaloids, from 1952 to 2015, are discussed. From an analysis of their structural properties and an investigation of the literature, possible future trends for canthin-6-one alkaloids are proposed. The information reported will be helpful in future research on canthin-6-one alkaloids.

Canthin-6-one displays antiproliferative activity and causes accumulation of cancer cells in the G2/M phase

Canthinones are natural substances with a wide range of biological activities, including antipyretic, antiparasitic, and antimicrobial. Antiproliferative and/or cytotoxic effects of canthinones on cancer cells have also been described, although their mechanism of action remains ill defined. To gain better insight into this mechanism, the antiproliferative effect of a commercially available canthin-6-one (1) was examined dose-dependently on six cancer cell lines (human prostate, PC-3; human colon, HT-29; human lymphocyte, Jurkat; human cervix, HeLa; rat glioma, C6; and mouse embryonic fibroblasts, NIH-3T3). Cytotoxic effects of 1 were investigated on the same cancer cell lines by procaspase-3 cleavage and on normal human skin fibroblasts. Strong antiproliferative effects of the compound were observed in all cell lines, whereas cytotoxic effects were very dependent on cell type. A better definition of the mechanism of action of 1 was obtained on PC-3 cells, by showing that it decreases BrdU incorporation into DNA by 60% to 80% and mitotic spindle formation by 70% and that it causes a 2-fold accumulation of cells in the G2/M phase of the cell cycle. Together, the data suggest that the primary effect of canthin-6-one (1) is antiproliferative, possibly by interfering with the G2/M transition. Proapoptotic effects might result from this disturbance of the cell cycle.

Enzymatic Characterization of ER Stress-Dependent Kinase, PERK, and Development of a High-Throughput Assay for Identification of PERK Inhibitors

PERK is serine/threonine kinase localized to the endoplasmic reticulum (ER) membrane. PERK is activated and contributes to cell survival in response to a variety of physiological stresses that affect protein quality control in the ER, such as hypoxia, glucose depravation, increased lipid biosynthesis, and increased protein translation. Pro-survival functions of PERK are triggered by such stresses, suggesting that development of small-molecule inhibitors of PERK may be efficacious in a variety of disease scenarios. Hence, we have conducted a detailed enzymatic characterization of the PERK kinase to develop a high-throughput-screening assay (HTS) that will permit the identification of small-molecule PERK inhibitors. In addition to establishing the K(m) of PERK for both its primary substrate, eIF2α, and for adenosine triphosphate, further mechanistic studies revealed that PERK targets its substrate via either a random/steady-state ordered mechanism. For HTS, we developed a time-resolved fluorescence resonance energy transfer-based assay that yielded a robust Z' factor and percent coefficient of variation value, enabling the successful screening of 79,552 compounds. This approach yielded one compound that exhibited good in vitro and cellular activity. These results demonstrate the validity of this screen and represent starting points for drug discovery efforts.

Multicomponent phytotherapeutic approach gaining momentum: Is the "one drug to fit all" model breaking down?

Natural product based drugs constitute a substantial proportion of the pharmaceutical market particularly in the therapeutic areas of infectious diseases and oncology. The primary focus of any drug development program so far has been to design selective ligands (drugs) that act on single selective disease targets to obtain highly efficacious and safe drugs with minimal side effects. Although this approach has been successful for many diseases, yet there is a significant decline in the number of new drug candidates being introduced into clinical practice over the past few decades. This serious innovation deficit that the pharmaceutical industries are facing is due primarily to the post-marketing failures of blockbuster drugs. Many analysts believe that the current capital-intensive model-"the one drug to fit all" approach will be unsustainable in future and that a new "less investment, more drugs" model is necessary for further scientific growth. It is now well established that many diseases are multi-factorial in nature and that cellular pathways operate more like webs than highways. There are often multiple ways or alternate routes that may be switched on in response to the inhibition of a specific target. This gives rise to the resistant cells or resistant organisms under the specific pressure of a targeted agent, resulting in drug resistance and clinical failure of the drug. Drugs designed to act against individual molecular targets cannot usually combat multifactorial diseases like cancer, or diseases that affect multiple tissues or cell types such as diabetes and immunoinflammatory diseases. Combination drugs that affect multiple targets simultaneously are better at controlling complex disease systems and are less prone to drug resistance. This multicomponent therapy forms the basis of phytotherapy or phytomedicine where the holistic therapeutic effect arises as a result of complex positive (synergistic) or negative (antagonistic) interactions between different components of a cocktail. In this approach, multicomponent therapy is considered to be advantageous for multifactorial diseases, instead of a "magic bullet" the metaphor of a "herbal shotgun" might better explain the state of affairs. The different interactions between various components might involve the protection of an active substance from decomposition by enzymes, modification of transport across membranes of cells or organelles, evasion of multidrug resistance mechanisms among others.

The MFS-type efflux pump Flr1 induced by Yap1 promotes canthin-6-one resistance in yeast

Screening for suppressors of canthin-6-one toxicity in yeast identified Yap1, a transcription factor involved in cell response to a broad range of injuries. Although canthin-6-one did not promote a significant oxidative stress, overexpression of YAP1 gene clearly increased resistance to this drug. We demonstrated that Yap1-mediated resistance involves the plasma membrane major-facilitator-superfamily efflux pump Flr1 but not the vacuolar ATP-binding-cassette transporter Ycf1. FLR1 overexpression was sufficient to reduce sensitivity to the drug, but strictly dependent on a functional YAP1 gene.

Synthesis, antitumor, antitrypanosomal and antileishmanial activities of benzo[4,5]canthin-6-ones bearing the N'-(Substituted benzylidene)-carbohydrazide and N-Alkylcarboxamide groups at C-2

A series of novel benzo[4,5]canthin-6-ones, bearing the N'-(substituted benzylidene)-carbohydrazide (11a-e) and N-alkylcarboxamide (13a-g) moieties at position-2, were synthesized and screened for their in vitro antitumor activity, against seven human cancer cell lines, and for antitrypanosomal and antileishmanial activities against Trypanosoma cruzi and Leishmania amazonensis. The results indicated that N-methylpiperazyl-6-oxobenzo[4,5]canthine-2-carboxamide (13f) displayed potent antitumor activity with IC(50) values in the range of 1.15-8.46 µM for all cell lines tested. Compounds 13f and 13g bearing an N-methylpiperazylcarboxamide and N-morpholylcarboxamide at C-2, respectively, showed potent activities towards both Trypanosoma cruzi and Leishmania amazonensis parasites, with IC(50) in the range of 0.4 to 16.70 µM.

Retinoic acid enhances TRAIL-induced apoptosis in cancer cells by upregulating TRAIL receptor 1 expression

Many human cancer cells are sensitive to killing by the proapoptotic ligand TNF-related apoptosis-inducing ligand (TRAIL), which is under study for cancer treatment in clinical trials. The TRAIL receptor (TRAIL-R1; also known as death receptor 4) is a transmembrane receptor that mediates TRAIL-induced apoptosis in cancer cells. In this study, we show that retinoids sensitize cancer cells to TRAIL-induced apoptosis by upregulating expression of TRAIL-R1. All-trans retinoic acid (ATRA) upregulated TRAIL-R1 expression in human cancer cells at the transcriptional level. The ability of ATRA to activate TRAIL-R1 expression was inhibited by retinoic acid receptor (RAR) antagonists or siRNAs, but augmented by several RAR agonists. In analyzing how ATRA induces RAR-dependent transcriptional upregulation of TRAIL-R1, we identified 2 putative retinoic acid response elements termed Pal-17 (a palindrome separated by 17 bases) and DR-11 (a direct repeat separated by 11 bases) in the 5'-flanking region of TRAIL-R1 gene. Deletion of DR-11, but not Pal-17, abrogated the ability of ATRA to stimulate TRAIL-R1 promoter activity. Consistent with this observation, RAR binding to DR-11, but not to Pal-17, was detected by chromatin immunoprecipitation assay in ATRA-treated cells, arguing that DR-11 was responsible for ATRA-mediated activation of the TRAIL-R1 gene. ATRA augmented TRAIL-induced apoptosis of cancer cells, and this activity was attenuated by a blockade to upregulation of TRAIL-R1 expression. Taken together, our findings establish that ATRA accentuates TRAIL-induced apoptosis, reveal a novel mechanism by which retinoids modulate apoptosis, and suggest a novel strategy to augment the anti-cancer activity of TRAIL.

Three-step synthesis of Ethyl Canthinone-1-carboxylates from ethyl 4-bromo-6-methoxy-1,5-naphthyridine-3-carboxylate via a Pd-catalyzed Suzuki-Miyaura coupling and a Cu-catalyzed amidation reaction [corrected]

Ethyl canthin-6-one-1-carboxylate (1b) and nine analogues 1c-k were prepared from readily prepared ethyl 4-bromo-6-methoxy-1,5-naphthyridine-3-carboxylate (2b) via a three-step non-classical approach that focused on construction of the central pyrrole (ring B) using Pd-catalyzed Suzuki-Miyaura coupling followed by Cu-catalyzed C-N coupling. Furthermore, treatment of the ethyl canthinone-1-carboxylate 1b with NaOH in DCM/MeOH (9:1) gave the canthin-6-one-1-carboxylic acid (6) in high yield. All compounds are fully characterized.

c-Jun NH2-terminal kinase-dependent upregulation of DR5 mediates cooperative induction of apoptosis by perifosine and TRAIL

BACKGROUND

Perifosine, an alkylphospholipid tested in phase II clinical trials, modulates the extrinsic apoptotic pathway and cooperates with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) to augment apoptosis. The current study focuses on revealing the mechanisms by which perifosine enhances TRAIL-induced apoptosis.

RESULTS

The combination of perifosine and TRAIL was more active than each single agent alone in inducing apoptosis of head and neck squamous cell carcinoma cells and inhibiting the growth of xenografts. Interestingly, perifosine primarily increased cell surface levels of DR5 although it elevated the expression of both DR4 and DR5. Blockade of DR5, but not DR4 upregulation, via small interfering RNA (siRNA) inhibited perifosine/TRAIL-induced apoptosis. Perifosine increased phosphorylated c-Jun NH2-terminal kinase (JNK) and c-Jun levels, which were paralleled with DR4 and DR5 induction. However, only DR5 upregulaiton induced by perifosine could be abrogated by both the JNK inhibitor SP600125 and JNK siRNA. The antioxidants, N-acetylcysteine and glutathione, but not vitamin C or tiron, inhibited perifosine-induced elevation of p-c-Jun, DR4 and DR5. Moreover, no increased production of reactive oxygen species was detected in perifosine-treated cells although reduced levels of intracellular GSH were measured.

CONCLUSIONS

DR5 induction plays a critical role in mediating perifosine/TRAIL-induced apoptosis. Perifosine induces DR5 expression through a JNK-dependent mechanism independent of reactive oxygen species.

Glycogen synthase kinase-3 inhibitors augment TRAIL-induced apoptotic death in human hepatoma cells

Hepatocellular carcinoma (HCC) displays a striking resistance to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). Therefore, the characterization of pharmacological agents that overcome this resistance may provide new therapeutic modalities for HCC. Here, we examined whether glycogen synthase kinase-3 (GSK-3) inhibitors could restore TRAIL sensitivity in hepatoma cells. To this aim, the effects of two GSK-3 inhibitors, lithium and SB-415286, were analyzed on TRAIL apoptotic signaling in human hepatoma cell lines in comparison with normal hepatocytes. We observed that both inhibitors sensitized hepatoma cells, but not normal hepatocytes, to TRAIL-induced apoptosis by enhancing caspase-8 activity and the downstream recruitment of the mitochondrial machinery. GSK-3 inhibitors also stabilized p53 and the down-regulation of p53 by RNA interference abolished the sensitizing effect of lithium on caspase-3 activation. Concomitantly, GSK-3 inhibitors strongly activated c-Jun N-terminal kinases (JNKs). The pharmacological inhibition of JNKs with AS601245 or SP600125 resulted in an earlier and stronger induction of apoptosis indicating that activated JNKs transduced protective signals and provided an anti-apoptotic balance to the pro-apoptotic effects of GSK-3 inhibitors. These findings demonstrate that GSK-3 exerts a negative and complex constraint on TRAIL apoptotic signaling in hepatoma cells, which can be greatly alleviated by GSK-3 inhibitors. Therefore, GSK-3 inhibitors may open new perspectives to enhance the anti-tumor activity of TRAIL in HCC.

Apoptosis inhibition in cancer cells: A novel molecular pathway that involves BAG3 protein

Stress-induced apoptosis regulates neoplasia pathogenesis and response to therapy. Indeed, cell transformation induces a stress response, that is overcome, in neoplastic cells, by alterations in apoptosis modulators; on the other hand, antineoplastic therapies largely trigger the apoptosis stress pathway, whose impairment results in resistance. Therefore, the study of the roles of apoptosis-modulating molecules in neoplasia development and response to therapy is of key relevance for our understanding of these processes. Among molecules that regulate apoptosis, a role is emerging for BAG3, a member of the BAG co-chaperone protein family. Proteins that share the BAG domain are characterized by their interaction with a variety of partners (heat shock proteins, steroid hormone receptors, Raf-1 and others), involved in regulating a number of cellular processes, including proliferation and apoptosis. BAG3, also known as CAIR-1 or Bis, forms a complex with the heat shock protein (Hsp) 70. This assists polypeptide folding, can mediate protein delivery to proteasome and is able to modulate apoptosis by interfering with cytochrome c release, apoptosome assembly and other events in the death process. It has been recently shown that, in human primary lymphoid and myeloblastic leukemias and other neoplastic cell types, BAG3 expression sustains cell survival and underlies resistance to therapy, through downmodulation of apoptosis. This review summarizes findings that assign an apoptotic role to BAG3 in some neoplastic cell types and identify the protein as a candidate target of therapy.

The antiapoptotic protein BAG3 is expressed in thyroid carcinomas and modulates apoptosis mediated by tumor necrosis factor-related apoptosis-inducing ligand

CONTEXT

We previously showed that BAG3 protein, a member of the BAG (Bcl-2-associated athanogene) co-chaperone family, modulates apoptosis in human leukemias. The expression of BAG3 in other tumor types has not been extensively investigated so far.

OBJECTIVE

The objective of this study was to analyze BAG3 expression in thyroid neoplastic cells and investigate its influence in cell apoptotic response to TNF-related apoptosis-inducing ligand (TRAIL).

DESIGN, SETTING, AND PATIENTS

We investigated BAG3 expression in human thyroid carcinoma cell lines, including NPA, and the effect of BAG3-specific small interfering RNA on TRAIL-induced apoptosis in NPA cells. Subsequently, we analyzed BAG3 expression in 30 benign lesions and 56 carcinomas from patients of the Naples Tumor Institute Fondazione Senatore Pascale.

MAIN OUTCOME MEASURES

The main outcome measures were: analysis of BAG3 protein in NPA cells by Western blot and immunocytochemistry; analysis of apoptosis in TRAIL-stimulated NPA cells by flow cytometry; and evaluation of BAG3 expression in specimens from thyroid lesions by immunohistochemistry.

RESULTS

BAG3 was expressed in human thyroid carcinoma cell lines; small interfering RNA-mediated downmodulation of its levels significantly (P < 0.0195) enhanced NPA cell apoptotic response to TRAIL. The protein was not detectable in 19 of 20 specimens of normal thyroid or goiters, whereas 54 of 56 analyzed carcinomas (15 follicular, 28 papillary, and 13 anaplastic) were clearly positive for BAG3 expression.

CONCLUSIONS

BAG3 downmodulates the apoptotic response to TRAIL in human neoplastic thyroid cells. The protein is specifically expressed in thyroid carcinomas and not in normal thyroid tissue or goiter.