Intracellular Ca2+ release mediates ursolic acid-induced apoptosis in human leukemic HL-60 cells

Progress in discovery and development of natural inhibitors of histone deacetylases (HDACs) as anti-cancer agents

The study of epigenetic translational modifications had drawn great interest for the last few decades. These processes play a vital role in many diseases and cancer is one of them. Histone acetyltransferase (HAT) and histone deacetylases (HDACs) are key enzymes involved in the acetylation and deacetylation of histones and ultimately in post-translational modifications. Cancer frequently exhibits epigenetic changes, particularly disruption in the expression and activity of HDACs. It includes the capacity to regulate proliferative signalling, circumvent growth inhibitors, escape cell death, enable replicative immortality, promote angiogenesis, stimulate invasion and metastasis, prevent immunological destruction, and genomic instability. The majority of tumours develop and spread as a result of HDAC dysregulation. As a result, HDAC inhibitors (HDACis) were developed, and they today stand as a very promising therapeutic approach. One of the most well-known and efficient therapies for practically all cancer types is chemotherapy. However, the efficiency and safety of treatment are constrained by higher toxicity. The same has been observed with the synthetic HDACi. Natural products, owing to many advantages over synthetic compounds for cancer treatment have always been a choice for therapy. Hence, naturally available molecules are of particular interest for HDAC inhibition and HDAC has drawn the attention of the research fraternity due to their potential to offer a diverse array of chemical structures and bioactive compounds. This diversity opens up new avenues for exploring less toxic HDAC inhibitors to reduce side effects associated with conventional synthetic inhibitors. The review presents comprehensive details on natural product HDACi, their mechanism of action and their biological effects. Moreover, this review provides a brief discussion on the structure activity relationship of selected natural HDAC inhibitors and their analogues which can guide future research to discover selective, more potent HDACi with minimal toxicity.

Ligustri Lucidi Fructus, a traditional Chinese Medicine: Comprehensive review of botany, traditional uses, chemical composition, pharmacology, and toxicity

ETHNOPHARMACOLOGICAL RELEVANCE

Ligustri Lucidi Fructus (LLF) is one of the usual Chinese herbs that has long been used with high therapeutic and condition value. LLF is used for the treatment of dizziness and tinnitus, soreness and weakness of the waist and knees, premature greying of the hair, the darkness of the eyes, internal heat and thirst, bone steam and hot flashes and other symptoms.

AIM OF THE STUDY

This review reviews botany, traditional uses, processing, phytochemistry, quality control, pharmacology, toxicity and pharmacokinetics to better understand its therapeutic potential.

MATERIALS AND METHODS

The literature on LLF was obtained from Google Scholar and Baidu Scholar, PubMed, ScienceDirect, SciFinder, Web of Science, China National Knowledge Infrastructure (CNKI), WAN FANG DATA and libraries. Some local books, official websites, PhD or MS's dissertations were also included. Phytochemical constituents' structures were drawn by ChemDraw software.

RESULTS

So far, Multiple chemical components were isolated and identified from LLF, mainly including terpenoids and flavonoids. Modern studies have shown that LLF extracts and compounds have a wide range of pharmacological effects, including antitumor, liver protection, blood glucose, lipid-lowering, immune regulation, and other aspects.

CONCLUSIONS

LLF occupies an important position in the traditional medical system. It is cost-effective and is a significant plant with therapeutic applications in modern medicine. However, further in-depth studies are needed to determine the medical use of this plant and its chemical composition, pharmacological activity, quality control, toxicity and pharmacokinetics.

The Effects of Methanol Extracts of Hyssopus officinalis on Model of Induced Glioblastoma Multiforme (GBM) in Rats

Given the complexity of pathophysiological processes of brain tumors, ineffective therapies, and high mortality rate, new therapeutic options with less toxicity are necessary. Hyssopus officinalis (hyssop) is an aromatic plant with important biological activities. The aim of this study is to assess the anti-cancer effect of hyssop extract on damages of glioblastoma multiforme. In this study, total flavonoids, phenolic content, and quantification of phenolic compound of hyssop extracts were analyzed. In vitro antioxidant properties of hyssop extract were also examined. In addition, cell viability, apoptosis, and cell cycle were evaluated in C6 glioma cell culture. In vivo, the rats were divided randomly into four main groups: intact, control, vehicle, and treatment groups. 1 × 106 C6 rat glioma cells were implanted into the right caudate nucleus of the rat's brain. The treatment group received the methanol extract of hyssop (100 mg/kg) for 7 days. Evolution of locomotor activity, tumor volume, survival rate, activities of antioxidant enzymes (superoxide dismutase (SOD) and catalase (CAT)), vascular endothelial growth factor (VEGF) expression, TUNEL-positive cells, p53 and p21 mRNA expression, and histological alterations were performed. The results showed that the methanol extract of hyssop increased the apoptosis and reduced the cell division of C6 glioma cells in cell culture. Moreover, methanol extract decreased the tumor volume and prolonged survival. Also, the activity of SOD and CAT enzymes was reduced in tumor tissue and enhanced in surrounding tissue. TUNEL-positive cells were increased in methanol extract of hyssop group. The expression of p53 and p21 mRNA was upregulated in the treatment group. Moreover, the histological analysis indicated a considerable decrease in invasion of tumor cells and inflammation in the hyssop-treated rats. According to the achieved results, it can be stated that hyssop has sufficient potential to inhibit damage of brain tumors, at least in part, by affecting the oxidative stress and cell proliferation pathways.

Perspectives on natural compounds in chemoprevention and treatment of cancer: an update with new promising compounds

Cancer is the second deadliest disease worldwide. Although recent advances applying precision treatments with targeted (molecular and immune) agents are promising, the histological and molecular heterogeneity of cancer cells and huge mutational burdens (intrinsic or acquired after therapy) leading to drug resistance and treatment failure are posing continuous challenges. These recent advances do not negate the need for alternative approaches such as chemoprevention, the pharmacological approach to reverse, suppress or prevent the initial phases of carcinogenesis or the progression of premalignant cells to invasive disease by using non-toxic agents. Although data are limited, the success of several clinical trials in preventing cancer in high-risk populations suggests that chemoprevention is a rational, appealing and viable strategy to prevent carcinogenesis. Particularly among higher-risk groups, the use of safe, non-toxic agents is the utmost consideration because these individuals have not yet developed invasive disease. Natural dietary compounds present in fruits, vegetables and spices are especially attractive for chemoprevention and treatment because of their easy availability, high margin of safety, relatively low cost and widespread human consumption. Hundreds of such compounds have been widely investigated for chemoprevention and treatment in the last few decades. Previously, we reviewed the most widely studied natural compounds and their molecular mechanisms, which were highly exploited by the cancer research community. In the time since our initial review, many promising new compounds have been identified. In this review, we critically review these promising new natural compounds, their molecular targets and mechanisms of anticancer activity that may create novel opportunities for further design and conduct of preclinical and clinical studies.

Voltage-Dependent Anion Channels Influence Cytotoxicity of ME-344, a Therapeutic Isoflavone

ME-344 is a second-generation cytotoxic isoflavone with anticancer activity promulgated through interference with mitochondrial functions. Using a click chemistry version of the drug together with affinity-enriched mass spectrometry, voltage-dependent anion channels (VDACs) 1 and 2 were identified as drug targets. To determine the importance of VDAC1 or 2 to cytotoxicity, we used lung cancer cells that were either sensitive (H460) or intrinsically resistant (H596) to the drug. In H460 cells, depletion of VDAC1 and VDAC2 by small interfering RNA impacted ME-344 effects by diminishing generation of reactive oxygen species (ROS), preventing mitochondrial membrane potential dissipation, and moderating ME-344-induced cytotoxicity and mitochondrial-mediated apoptosis. Mechanistically, VDAC1 and VDAC2 knockdown prevented ME-344-induced apoptosis by inhibiting Bax mitochondrial translocation and cytochrome c release as well as apoptosis in these H460 cells. We conclude that VDAC1 and 2, as mediators of the response to oxidative stress, have roles in modulating ROS generation, Bax translocation, and cytochrome c release during mitochondrial-mediated apoptosis caused by ME-344. SIGNIFICANCE STATEMENT: Dissecting preclinical drug mechanisms are of significance in development of a drug toward eventual Food and Drug Administration approval.

Antioxidant and Antiproliferative Potential of Bioactive Molecules Ursolic Acid and Thujone Isolated from Memecylon edule and Elaeagnus indica and Their Inhibitory Effect on Topoisomerase II by Molecular Docking Approach

The present study aimed to evaluate the antioxidant and antiproliferative potential of ursolic acid and thujone isolated from leaves of Elaeagnus indica and Memecylon edule and their inhibitory effect on topoisomerase II using molecular docking study. The isolated ursolic acid and thujone were examined for different types of free radicals scavenging activity, the antiproliferative potential on U-937 and HT-60 cell lines by adopting standard methods. Further, these compounds were docked with the active site of the ATPase region of topoisomerase II. The findings of the research revealed that ursolic acid harbor strong antioxidant and antiproliferative capacity with low IC50 values than the thujone in all tested methods. Moreover, ursolic acid shows significant inhibition effect on topoisomerase II with a considerable docking score (-8.0312) and GLIDE energy (-51.86 kca/mol). The present outcome concludes that ursolic acid possesses significant antioxidant and antiproliferative potential, which can be used in the development of novel antioxidant and antiproliferative agents in the future.

Inhibition of Proliferation of SGC7901 and BGC823 Human Gastric Cancer Cells by Ursolic Acid Occurs Through a Caspase-Dependent Apoptotic Pathway

BACKGROUND Worldwide, gastric cancer is one of the most common malignant tumors. Ursolic acid is a plant metabolite and pentacyclic triterpenoid used in traditional Chinese medicine. This study aimed to investigate the effects of ursolic acid the growth and apoptosis of SGC7901 and BGC823 human gastric cancer cells in vitro. MATERIAL AND METHODS SGC7901 and BGC823 human gastric cancer cells and normal GES-1 gastric epithelial cells were cultured with increasing doses of ursolic acid at 50, 60, and 100 µM. Cell viability and proliferation were assessed using an MTT assay. Flow cytometry was used to assess cell apoptosis. Western blot was used to measure procaspase-8, procaspase-9, procaspase-3, and cleaved poly (ADP-ribose) polymerase (PARP) expression. The expression of receptor interaction protein 3 (RIP3) was examined by Western blot and reverse transcription polymerase chain reaction (RT-PCR). Morphological changes in the gastric cancer cells were determined using Hoechst 33342 staining following ursolic acid treatment. RESULTS Ursolic acid inhibited the viability of SGC7901 and BGC823 cells but not GES-1 cells. Ursolic acid treatment significantly induced apoptosis in SGC7901 and BGC823 cells when compared with GES-1 cells (P<0.05), and significantly increased the activation of caspase-3, caspase-8, caspase-9, poly ADPribose polymerase (PARP), and the production of reactive oxygen species (ROS). Treatment of SGC7901 and BGC823 cells with ursolic acid for 72 h did not induce necroptosis. CONCLUSIONS Ursolic acid inhibited the proliferation of SGC7901 and BGC823 human gastric cancer cells in vitro through a caspase-dependent apoptotic pathway.

Triterpenes from the fruit of Camptotheca acuminata suppress human hepatocellular carcinoma cell proliferation through apoptosis induction

The fruit of Camptotheca acuminata, a kind of mainly medicinal plant, possesses good antitumor properties. In order to explore the bioactive compounds for the treatment of hepatocellular carcinoma, the study focused on the isolation of cytotoxic compounds from the fruit of Camptotheca acuminata, which led to the discovery of fourteen compounds, including one new triterpene, 3β,20-dihydroxy-30α-methyl,17(29)-β-epoxy-28-norlupane (1), together with thirteen known compounds (2-14). The structures of isolated compounds were demonstrated by spectroscopic methods including 1D and 2D NMR spectroscopy. Moreover, all triterpenes were evaluated for antiproliferative activities against two human hepatocellular carcinoma cell lines, HepG2 and Hep3B. Compound 3 showed the strongest cytotoxic activity against the HepG2 with IC₅₀ value at 29.6 μM. Further study demonstrated that compound 3 exhibited cytotoxic activity through the induction of apoptosis.

A smart pH-responsive nano-carrier as a drug delivery system for the targeted delivery of ursolic acid: suppresses cancer growth and metastasis by modulating P53/MMP-9/PTEN/CD44 mediated multiple signaling pathways

Ursolic acid (UA) has been recently used as a promising anti-tumor and cancer metastatic chemo-preventive agent due to its low toxicity and liver-protecting property. However, the low bioavailability and nonspecific tumor targeting restrict its further clinical application. To address the problem, a silica-based mesoporous nanosphere (MSN) controlled-release drug delivery system (denoted UA@M-CS-FA) was designed and successfully synthesized, and was functionalized with folic acid (FA) and pH-sensitive chitosan (CS) for the targeted delivery of UA to folate receptor (FR) positive tumor cells. UA@M-CS-FA were spherical with mean diameter below 150 nm, and showed about -20 mV potential. Meanwhile, UA@M-CS-FA exhibited a pH-sensitive release manner and high cellular uptake in FR over-expressing HeLa cancer cells. Also, in vitro cellular assays suggested that UA@M-CS-FA inhibited cancer cell growth, invasion and migration. Mechanistically, UA@M-CS-FA induced cancer cell apoptosis and inhibited migration via cell cycle arrest in the G0/G1 stage, regulating the PARP/Bcl-2/MMP-9/CD44/PTEN/P53. Importantly, in vivo experiments further confirmed that UA@M-CS-FA significantly suppressed the tumor progression and lung metastasis in tumor-bearing nude mice. Immunohistochemical analysis revealed that UA@M-CS-FA treatment regulated CD44, a biomarker of cancer metastasis. Overall, our data demonstrated that a CS and FA modified MSN controlled-release drug delivery system could help broaden the usage of UA and reflect the great application potential of the UA as an anticancer or cancer metastatic chemopreventive agent.

Ursolic acid-mediated apoptosis of K562 cells involves Stat5/Akt pathway inhibition through the induction of Gfi-1

Ursolic acid (UA) is a promising natural compound for cancer prevention and therapy. We previously reported that UA induced apoptosis in CML-derived K562 cells. Here we show that the apoptotic process is accompanied by down-regulation of Bcl-xL and Mcl-1 expression and dephosphorylation of Bad. These events are associated with Stat5 inhibition, which is partially mediated through elevated expression of transcriptional repressor Gfi-1. Gfi-1 knockdown using siRNA abrogates the ability of UA to decrease Stat5b expression and attenuates apoptosis induction by UA. We also demonstrate that UA suppresses the Akt kinase activity by inhibiting Akt1/2 expression, which correlates with Stat5 inhibition. Stat5 activity inhibited by a chemical inhibitor or siRNA, Akt1/2 mRNA expression is suppressed. Moreover, we show that UA exerts growth-inhibition in Imatinib-resistant K562/G01. UA has synergistic effects when used in combination with Imatinib in both K562 and K562/G01. Altogether, the data provide evidence that UA's pro-apoptotic effect in K562 cells is associated with the Gfi-1/Stat5/Akt pathway. The findings indicate that UA could potentially be a useful agent in the treatment of CML.

Ursolic acid (UA): A metabolite with promising therapeutic potential

Plants are known to produce a variety of bioactive metabolites which are being used to cure various life threatening and chronic diseases. The molecular mechanism of action of such bioactive molecules, may open up new avenues for the scientific community to develop or improve novel therapeutic approaches to tackle dreadful diseases such as cancer and cardiovascular and neurodegenerative disorders. Ursolic acid (UA) is one among the categories of such plant-based therapeutic metabolites having multiple intracellular and extracellular targets that play role in apoptosis, metastasis, angiogenesis and inflammatory processes. Moreover, the synthetic derivatives of UA have also been seen to be involved in a range of pharmacological applications, which are associated with prevention of diseases. Evidences suggest that UA could be used as a potential candidate to develop a comprehensive competent strategy towards the treatment and prevention of health disorders. The review article herein describes the possible therapeutic effects of UA along with putative mechanism of action.

Ursolic Acid--A Pentacyclic Triterpenoid with a Wide Spectrum of Pharmacological Activities

Ursolic acid (UA) is a natural terpene compound exhibiting many pharmaceutical properties. In this review the current state of knowledge about the health-promoting properties of this widespread, biologically active compound, as well as information about its occurrence and biosynthesis are presented. Particular attention has been paid to the application of ursolic acid as an anti-cancer agent; it is worth noticing that clinical tests suggesting the possibility of practical use of UA have already been conducted. Amongst other pharmacological properties of UA one can mention protective effect on lungs, kidneys, liver and brain, anti-inflammatory properties, anabolic effects on skeletal muscles and the ability to suppress bone density loss leading to osteoporosis. Ursolic acid also exhibits anti-microbial features against numerous strains of bacteria, HIV and HCV viruses and Plasmodium protozoa causing malaria.

Synthesis, anti-tumor and anti-angiogenic activity evaluations of asiatic Acid amino Acid derivatives

Fifteen semi-synthetic derivatives of asiatic acid (AA) have been synthesized and evaluated for their biological activities. The successful modification of these compounds at the C-2, C-3, C-23 and C-28 positions was confirmed using NMR, MS and IR spectra. Further, their anti-tumor effects were evaluated in vitro using different cancer cell lines (HeLa, HepG2, B16F10, SGC7901, A549, MCF7 and PC3), while their anti-angiogenic activities were evaluated in vivo using a larval zebrafish model. Among the derivatives, compounds 4–10 showed more potent cytotoxic and anti-angiogenic effects than AA, while compounds 11–17 had significantly less effects. The new derivative 10 was also included in finished formulations to evaluate its stability using HPLC due to its potential topical use. The derivative 10 had markedly better anti-tumor activities than both AA and other derivatives, with similar stability as its parent compound AA.

Corosolic Acid Exhibits Anti-angiogenic and Anti-lymphangiogenic Effects on In Vitro Endothelial Cells and on an In Vivo CT-26 Colon Carcinoma Animal Model

We describe the anti-angiogenic and anti-lymphangiogenic effects of corosolic acid, a pentacyclic triterpenoid isolated from Cornus kousa Burg. A mouse colon carcinoma CT-26 animal model was employed to determine the in vivo anti-angiogenic and anti-lymphangiogenic effects of corosolic acid. Corosolic acid induced apoptosis in CT-26 cells, mediated by the activation of caspase-3. In addition, it reduced the final tumor volume and the blood and lymphatic vessel densities of tumors, indicating that it suppresses in vivo angiogenesis and lymphangiogenesis. Corosolic acid inhibited the proliferation and tube formation of human umbilical vein endothelial cells and human dermal lymphatic microvascular endothelial cells. In addition, corosolic acid decreased the proliferation and migration of human umbilical vein endothelial cells stimulated by angiopoietin-1. Pretreatment with corosolic acid decreased the phosphorylation of focal adhesion kinase (FAK) and ERK1/2, suggesting that corosolic acid contains anti-angiogenic activity that can suppress FAK signaling induced by angiopoietin-1.

Ursolic acid and its natural derivative corosolic acid suppress the proliferation of APC-mutated colon cancer cells through promotion of β-catenin degradation

Ursolic acid (UA) and corosolic acid (CA), naturally occurring pentacyclic triterpene acids, exhibit antiproliferative activities against various cancer cells, but a clear chemopreventive mechanism of these triterpenoids in colon cancer cells remains to be answered. Here we used a cell-based reporter system for detection of β-catenin response transcription (CRT) to identify UA as an antagonist of the Wnt/β-catenin pathway. UA promoted the degradation of intracellular β-catenin that was accompanied by its N-terminal phosphorylation at Ser33/37/Thr41 residues, marking it for proteasomal degradation. Consistently, UA down-regulated the intracellular β-catenin level in colon cancer cells with inactivating mutations of adenomatous polyposis coli (APC). In addition, UA repressed the expression of β-catenin/T-cell factor (TCF)-dependent genes, thereby inhibiting cell proliferation in colon cancer cells. The functional group analysis revealed that the major structural requirements for UA-mediated β-catenin degradation are a carboxyl group at position 17 and a methyl group at position 19. Notably, CA (2α-hydroxyursolic acid) was also found to decrease the level of intracellular β-catenin and to suppress the growth of APC-mutated colon cancer cells. Our findings suggest that UA and CA exert their anticancer activities against colon cancer cells by promoting the N-terminal phosphorylation and subsequent proteasomal degradation of β-catenin.

Ezrin dephosphorylation/downregulation contributes to ursolic acid-mediated cell death in human leukemia cells

Ezrin links the actin filaments with the cell membrane and has a functional role in the apoptotic process. It appears clear that ezrin is directly associated with Fas, leading to activation of caspase cascade and cell death. However, the exact role of ezrin in ursolic acid (UA)-induced apoptosis remains unclear. In this study, we show for the first time that UA induces apoptosis in both transformed and primary leukemia cells through dephosphorylation/downregulation of ezrin, association and polarized colocalization of Fas and ezrin, as well as formation of death-inducing signaling complex. These events are dependent on Rho-ROCK1 signaling pathway. Knockdown of ezrin enhanced cell death mediated by UA, whereas overexpression of ezrin attenuated UA-induced apoptosis. Our in vivo study also showed that UA-mediated inhibition of tumor growth of mouse leukemia xenograft model is in association with the dephosphorylation/downregulation of ezrin. Such findings suggest that the cytoskeletal protein ezrin may represent an attractive target for UA-mediated lethality in human leukemia cells.

The role of calcium in VDAC1 oligomerization and mitochondria-mediated apoptosis

The voltage-dependent anion channel (VDAC), located at the outer mitochondria membrane (OMM), mediates interactions between mitochondria and other parts of the cell by transporting anions, cations, ATP, Ca(2+), and metabolites. Substantial evidence points to VDAC1 as being a key player in apoptosis, regulating the release of apoptogenic proteins from mitochondria, such as cytochrome c, and interacting with anti-apoptotic proteins. Recently, we demonstrated that VDAC1 oligomerization is a general mechanism common to numerous apoptogens acting via different initiating cascades and proposed that a protein-conducting channel formed within a VDAC1 homo/hetero oligomer mediates cytochrome c release. However, the molecular mechanism responsible for VDAC1 oligomerization remains unclear. Several studies have shown that mitochondrial Ca(2+) is involved in apoptosis induction and that VDAC1 possesses Ca(2+)-binding sites and mediates Ca(2+) transport across the OMM. Here, the relationship between the cellular Ca(2+) level, [Ca(2+)]i, VDAC1 oligomerization and apoptosis was studied. Decreasing [Ca(2+)]i using the cell-permeable Ca(2+) chelating reagent BAPTA-AM was found to inhibit VDAC1 oligomerization and apoptosis, while increasing [Ca(2+)]i using Ca(2+) ionophore resulted in VDAC1 oligomerization and apoptosis induction in the absence of apoptotic stimuli. Moreover, induction of apoptosis elevated [Ca(2+)]i, concomitantly with VDAC1 oligomerization. AzRu-mediated inhibition of mitochondrial Ca(2+) transport decreased VDAC1 oligomerization, suggesting that mitochondrial Ca(2+) is required for VDAC1 oligomerization. In addition, increased [Ca(2+)]i levels up-regulate VDAC1 expression. These results suggest that Ca(2+) promotes VDAC1 oligomerization via activation of a yet unknown signaling pathway or by increasing VDAC1 expression, leading to apoptosis. This article is part of a Special Issue entitled: 12th European Symposium on Calcium.

A phase I pharmacokinetic study of ursolic acid nanoliposomes in healthy volunteers and patients with advanced solid tumors

BACKGROUND

Ursolic acid is a promising anticancer agent. The current study aims to evaluate the single- and multiple-dose pharmacokinetics (PK) as well as the safety of ursolic acid nanoliposomes (UANL) in healthy volunteers and in patients with advanced solid tumors.

METHODS

Twenty-four healthy volunteers in the single-dose PK study were divided into three different groups, which received 37, 74, and 98 mg/m(2) of UANL. Eight patients in the multiple-dose PK study were administered with 74 mg/m(2) of UANL daily for 14 days. The UA plasma concentrations were determined using ultra-performance liquid chromatograph-tandem mass spectrometry.

RESULTS

The plasma concentration profiles of all subjects were characterized by a biexponential decline after infusion. The mean peak plasma concentration (C(max)) increased linearly as a function of the dose (r = 0.999). The mean area under the plasma concentration-time curve (AUC) from 0 to 16 hours also increased proportionally with dose escalation (r = 0.998). However, the clearance was constant over the specific dose interval. In the multiple-dose PK study, the trough and average concentrations remained low. The mean AUC, half-life, C(max), time to C(max), and the volume of distribution on the first day were similar to those on the last day. All subjects tolerated the treatments well. Most UANL-associated adverse events varied from mild to moderate.

CONCLUSIONS

UANL exhibits relatively linear PK behavior with dose levels from 37 mg/m(2) to 98 mg/m(2). No drug accumulation was observed with repeated doses of UANL. The intravenous infusion of UANL was well tolerated by healthy volunteers and patients with advanced tumors.

VDAC1: from structure to cancer therapy

Here, we review current evidence pointing to the function of VDAC1 in cell life and death, and highlight these functions in relation to cancer. Found at the outer mitochondrial membrane, VDAC1 assumes a crucial position in the cell, controlling the metabolic cross-talk between mitochondria and the rest of the cell. Moreover, its location at the boundary between the mitochondria and the cytosol enables VDAC1 to interact with proteins that mediate and regulate the integration of mitochondrial functions with other cellular activities. As a metabolite transporter, VDAC1 contributes to the metabolic phenotype of cancer cells. This is reflected by VDAC1 over-expression in many cancer types, and by inhibition of tumor development upon silencing VDAC1 expression. Along with regulating cellular energy production and metabolism, VDAC1 is also a key protein in mitochondria-mediated apoptosis, participating in the release of apoptotic proteins and interacting with anti-apoptotic proteins. The involvement of VDAC1 in the release of apoptotic proteins located in the inter-membranal space is discussed, as is VDAC1 oligomerization as an important step in apoptosis induction. VDAC also serves as an anchor point for mitochondria-interacting proteins, some of which are also highly expressed in many cancers, such as hexokinase (HK), Bcl2, and Bcl-xL. By binding to VDAC, HK provides both metabolic benefit and apoptosis-suppressive capacity that offers the cell a proliferative advantage and increases its resistance to chemotherapy. VDAC1-based peptides that bind specifically to HK, Bcl2, or Bcl-xL abolished the cell’s abilities to bypass the apoptotic pathway. Moreover, these peptides promote cell death in a panel of genetically characterized cell lines derived from different human cancers. These and other functions point to VDAC1 as a rational target for the development of a new generation of therapeutics.

Pomolic acid induces apoptosis in SK-OV-3 human ovarian adenocarcinoma cells through the mitochondrial-mediated intrinsic and death receptor-induced extrinsic pathways

The cytotoxic effect of pomolic acid (PA), a pentacyclic triterpene isolated from flowers of Osmanthus fragrans var. aurantiacus Makino, was investigated in SK-OV-3 human ovarian adenocarcinoma cells. PA dose-dependently inhibited the viability of SK-OV-3 cells. PA-induced apoptosis was further characterized by detection of cell surface annexin V and sub-G1 apoptotic cell populations. The number of cells immunostained with annexin V-fluorescein isothiocyanate (FITC) increased following treatment with PA. The sub-G1 cell populations also increased in PA-treated SK-OV-3 cells. PA induced the activation of caspase-8, -9 and -3, critical mediators of apoptosis signaling. PA decreased the mitochondrial transmembrane potential (ΔΨ(m)), resulting in the activation of caspase-9. In addition, PA increased the expression of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis signaling-related death receptor 5 (DR5), mediating caspase-8-involved extrinsic pathway. Taken together, our results indicate that PA induces apoptosis in SK-OV-3 cells, which is mediated by the mitochondrial-mediated intrinsic and death receptor-induced extrinsic pathways.

Ursolic acid inhibits growth and metastasis of human colorectal cancer in an orthotopic nude mouse model by targeting multiple cell signaling pathways: chemosensitization with capecitabine

PURPOSE

Development of chemoresistance, poor prognosis, and metastasis often renders the current treatments for colorectal cancer (CRC) ineffective. Whether ursolic acid, a component of numerous medicinal plants, either alone or in combination with capecitabine, can inhibit the growth and metastasis of human CRC was investigated.

EXPERIMENTAL DESIGN

The effect of ursolic acid on proliferation of CRC cell lines was examined by mitochondrial dye uptake assay, apoptosis by esterase staining, NF-κB activation by DNA-binding assay, and protein expression by Western blot. The effect of ursolic acid on the growth and chemosensitization was also examined in orthotopically implanted CRC in nude mice.

RESULTS

We found that ursolic acid inhibited the proliferation of different colon cancer cell lines. This is correlated with inhibition of constitutive NF-κB activation and downregulation of cell survival (Bcl-xL, Bcl-2, cFLIP, and survivin), proliferative (cyclin D1), and metastatic (MMP-9, VEGF, and ICAM-1) proteins. When examined in an orthotopic nude mouse model, ursolic acid significantly inhibited tumor volume, ascites formation, and distant organ metastasis, and this effect was enhanced with capecitabine. Immunohistochemistry of tumor tissue indicated that ursolic acid downregulated biomarkers of proliferation (Ki-67) and microvessel density (CD31). This effect was accompanied by suppression of NF-κB, STAT3, and β-catenin. In addition, ursolic acid suppressed EGF receptor (EGFR) and induced p53 and p21 expression. We also observed bioavailability of ursolic acid in the serum and tissue of animals.

CONCLUSION

Overall, our results show that ursolic acid can inhibit the growth and metastasis of CRC and further enhance the therapeutic effects of capecitabine through the suppression of multiple biomarkers linked to inflammation, proliferation, invasion, angiogenesis, and metastasis.

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.

Ursolic acid induces apoptosis in human leukaemia cells and exhibits anti-leukaemic activity in nude mice through the PKB pathway

BACKGROUND AND PURPOSE

Ursolic acid (UA) has been extensively used as an anti-leukaemic agent in traditional Chinese medicine. In the present study, we investigated the ability of UA to induce apoptosis in human leukaemia cells in relation to its effects on caspase activation, Mcl-1 down-regulation and perturbations in stress-induced signalling pathways such as PKB and JNK.

EXPERIMENTAL APPROACH

Leukaemia cells were treated with UA after which apoptosis, caspase activation, PKB and JNK signalling pathways were evaluated. The anti-tumour activity of UA was evaluated using xenograft mouse model.

KEY RESULTS

UA induced apoptosis in human leukaemia cells in a dose- and time-dependent manner; this was associated with caspase activation, down-regulation of Mcl-1 and inactivation of PKB accompanied by activation of JNK. Enforced activation of PKB by a constitutively active PKB construct prevented UA-mediated JNK activation, Mcl-1 down-regulation, caspase activation and apoptosis. Conversely, UA lethality was potentiated by the PI3-kinase inhibitor LY294002. Interruption of the JNK pathway by pharmacological or genetic (e.g. siRNA) attenuated UA-induced apoptosis. Furthermore, UA-mediated inhibition of tumour growth in vivo was associated with induction of apoptosis, inactivation of PKB as well as activation of JNK.

CONCLUSIONS AND IMPLICATIONS

Collectively, these findings suggest a hierarchical model of UA-induced apoptosis in human leukaemia cells in which UA induces PKB inactivation, leading to JNK activation and culminating in Mcl-1 down-regulation, caspase activation and apoptosis. These findings indicate that interruption of PKB/JNK pathways may represent a novel therapeutic strategy in haematological malignancies.

3-O-acetyloleanolic acid induces apoptosis in human colon carcinoma HCT-116 cells

The cytotoxic effect of 3-O-acetyloleanolic acid, an oleanolic acid derivative isolated from the seeds of Vigna sinensis K., was investigated in human colon carcinoma HCT-116 cells. 3-O-acetyloleanolic acid dose-dependently inhibited the viability of HCT-116 cells. Apoptosis was characterized by detection of cell surface annexin V and sub-G1 apoptotic cell populations. The number of immunostained cells with annexin V-FITC was increased after treatment with 3-O-acetyloleanolic acid. The sub-G1 cell population was also increased. Expression of TRAIL-mediated apoptosis signaling-related death receptor DR5 was increased in 3-O-acetyloleanolic acid-treated HCT-116 cells. Activation of caspase-8 and caspase-3, critical mediators of extrinsic apoptosis signaling, was also increased by 3-O-acetyloleanolic acid. The results indicate that 3-O-acetyloleanolic acid induces apoptosis in HCT-116 cells mediated by an extrinsic apoptosis signaling cascade via up-regulation of DR5.

Clinically useful anticancer, antitumor, and antiwrinkle agent, ursolic acid and related derivatives as medicinally important natural product

Medicinal plants are becoming an important research area for novel and bioactive molecules for drug discovery. Novel therapeutic strategies and agents are urgently needed to treat different incurable diseases. Many plant derived active compounds are in human clinical trials. Currently ursolic acid is in human clinical trial for treating cancer, tumor, and skin wrinkles. This review includes the clinical use of ursolic acid in various diseases including anticancer, antitumor, and antiwrinkle chemotherapies, and the isolation and purification of this tritepernoid from various plants to update current knowledge on the rapid analysis of ursolic acid by using analytical methods. In addition, the chemical modifications of ursolic acid to make more effective and water soluble derivatives, previous and current information regarding, its natural and semisynthetic analogs, focusing on its anticancer, cytotoxic, antitumor, antioxidant, anti-inflammatory, anti-HIV, acetyl cholinesterase, α-glucosidase, antimicrobial, and hepatoprotective activities, briefly discussion is attempted here for its research perspectives. This review article contains fourteen medicinally important ursolic acid derivatives and 351 references.

Inhibition of tumor progression by naturally occurring terpenoids

CONTEXT

Cancer is a major public health problem in India and many other parts of the world. Its two main characteristics are uncontrolled cell growth and metastasis. Natural products represent a rich source of compounds that have found many applications in various fields of medicines and therapy including cancer therapy. Effective ingredients in several plant-derived medicinal extracts are terpenoid compounds and many terpenes have biological activities and are used for the treatment of human diseases.

OBJECTIVES

This review attempted to collect all available published scientific literature of eight naturally occurring terpenoids and their effect on inhibition of tumor progression.

METHODS

The present review is about eight potent naturally occurring terpenoids that have been studied for their pharmacological properties in our lab and this review includes 130 references compiled from all major databases.

RESULTS

Literature survey revealed that triterpenoids, such as glycyrrhizic acid, ursolic acid, oleanolic acid, and nomilin, the diterpene andrographolide, and the monoterpenoids like limonene and perillic acid had shown immunomodulatory and antitumor activities. All of them could induce apoptosis in various cancer cells by activating various proapoptotic signaling cascades. Many of these terpenoids found to inhibit metastatic progression and tumor-induced angiogenesis. The molecular mechanisms that involved in these activities include inhibition of various oncogenic and anti-apoptotic signaling pathways and suppression or nuclear translocation of various transcription factors including nuclear factor kappa B (NF-κB).

CONCLUSION

The chemopreventive and chemoprotective effects of these compounds point toward their possible role in modern anticancer therapies.

Ursolic acid and its esters: occurrence in cranberries and other Vaccinium fruit and effects on matrix metalloproteinase activity in DU145 prostate tumor cells

BACKGROUND

Ursolic acid and its cis- and trans-3-O-p-hydroxycinnamoyl esters have been identified as constituents of American cranberries (Vaccinium macrocarpon), which inhibit tumor cell proliferation. Since the compounds may contribute to berry anticancer properties, their content in cranberries, selected cranberry products, and three other Vaccinium species (V. oxycoccus, V. vitis-idaea and V. angustifolium) was determined by liquid chromatography-mass spectroscopy. The ability of these compounds to inhibit growth in a panel of tumor cell lines and inhibit matrix metalloproteinase (MMP) activity associated with tumor invasion and metastasis was determined in DU145 prostate tumor cells.

RESULTS

The highest content of ursolic acid and esters was found in V. macrocarpon berries (0.460-1.090 g ursolic acid and 0.040-0.160 g each ester kg(-1) fresh weight). V. vitis-idaea and V. angustifolium contained ursolic acid (0.230-0.260 g kg(-1) ), but the esters were not detected. V. oxycoccus was lowest (0.129 g ursolic acid and esters per kg). Ursolic acid content was highest in cranberry products prepared from whole fruit. Ursolic acid and its esters inhibited tumor cell growth at micromolar concentrations, and inhibited MMP-2 and MMP-9 activity at concentrations below those previously reported for cranberry polyphenolics.

CONCLUSION

Cranberries (V. macrocarpon) were the best source of ursolic acid and its esters among the fruit and products tested. These compounds may limit prostate carcinogenesis through matrix metalloproteinase inhibition.

Ursolic acid, a pentacyclin triterpene, potentiates TRAIL-induced apoptosis through p53-independent up-regulation of death receptors: evidence for the role of reactive oxygen species and JNK

Discovery of the molecular targets of traditional medicine and its chemical footprints can validate the use of such medicine. In the present report, we investigated the effect of ursolic acid (UA), a pentacyclic triterpenoid found in rosemary and holy basil, on apoptosis induced by TRAIL. We found that UA potentiated TRAIL-induced apoptosis in cancer cells. In addition, UA also sensitized TRAIL-resistant cancer cells to the cytokine. When we investigated the mechanism, we found that UA down-regulated cell survival proteins and induced the cell surface expression of both TRAIL receptors, death receptors 4 and 5 (DR4 and -5). Induction of receptors by UA occurred independently of cell type. Gene silencing of either receptor by small interfering RNA reduced the apoptosis induced by UA and the effect of TRAIL. In addition, UA also decreased the expression of decoy receptor 2 (DcR2) but not DcR1. Induction of DRs was independent of p53 because UA induced DR4 and DR5 in HCT116 p53(-/-) cells. Induction of DRs, however, was dependent on JNK because UA induced JNK, and its pharmacologic inhibition abolished the induction of the receptors. The down-regulation of survival proteins and up-regulation of the DRs required reactive oxygen species (ROS) because UA induced ROS, and its quenching abolished the effect of the terpene. Also, potentiation of TRAIL-induced apoptosis by UA was significantly reduced by both ROS quenchers and JNK inhibitor. In addition, UA was also found to induce the expression of DRs, down-regulate cell survival proteins, and activate JNK in orthotopically implanted human colorectal cancer in a nude mouse model. Overall, our results showed that UA potentiates TRAIL-induced apoptosis through activation of ROS and JNK-mediated up-regulation of DRs and down-regulation of DcR2 and cell survival proteins.

Dominant-negative VDAC1 mutants reveal oligomeric VDAC1 to be the active unit in mitochondria-mediated apoptosis

Mitochondria play a central role in the intrinsic pathway of apoptosis. Oligomerization of the mitochondrial protein VDAC1 (voltage-dependent anion channel 1) has been proposed to play a role in apoptosis in various studies. In the present study, we have generated dimeric fusion proteins consisting of tandem-linked wild-type and RuR (Ruthenium Red)-insensitive mutant VDAC1 monomers and studied the capacity of RuR to protect against apoptosis, as induced by various means. Fusion proteins composed of wild-type and/or E72Q-VDAC1 were successfully expressed in T-REx-293 cells. Bilayer-reconstituted dimeric rVDAC1 (rat VDAC1) functions as a channel-forming protein, showing typical voltage-dependence conductance, but with a unitary conductance higher than that of monomeric VDAC. As with wild-type VDAC1, overexpression of either the wild-type or mutated VDAC1 dimeric fusion protein induced apoptotic cell death. In addition, as shown previously, the anti-apoptotic effect of RuR was not observed in cells expressing E72Q-VDAC1, despite endogenous VDAC1 being present in these cells. Similar RuR insensitivity governed the VDAC1 fusion proteins comprising the E72Q mutation in either the first, second or both VDAC1 monomers of the same dimer. RuR-mediated protection against apoptosis in T-REx-293 cells, as induced by staurosporine, was observed in cells expressing VDAC1 or dimeric wild-type VDAC1. However, RuR offered no protection against staurosporine-induced apoptosis in cells expressing E72Q-VDAC1 or E72Q-containing dimeric VDAC1. These results suggest that E72Q-VDAC1 has a dominant-negative effect and implies that VDAC1 homo-oligomerization, involving intermolecular interactions, might be involved in the apoptotic process.

Ursolic acid induces PC-3 cell apoptosis via activation of JNK and inhibition of Akt pathways in vitro

Ursolic acid (UA), a pentacyclic triterpenoid compound, has been demonstrated to have an antiproliferative effect in various tumors. We investigated the cell killing effects of UA in the human hormone refractory prostate cancer cell line, PC-3 cells. Also, the molecular mechanisms underlying its antigrowth effect were explored. We found that UA treatment in vitro can effectively inhibit PC-3 cell viability in a dose-dependent manner by inducing apoptosis, demonstrated by annexin V-FITC/propidium iodide staining. Both extrinsic and intrinsic apoptotic pathways appear to be triggered by UA treatment, because inhibiting activation of both caspase-8 and -9 could prevent UA-induced apoptosis in PC-3 cells. The c-Jun N-terminal kinase (JNK) was found to be activated, followed by Bcl-2 phosphorylation and activation of caspase-9. On the other hand, UA inhibited the Akt pathway, subsequently upregulating the expression of Fas ligand (FasL), which initiates death receptor-mediated apoptosis in PC-3 cells. Importantly, experimentally lowering FasL expression by siRNA significantly inhibited UA-induced caspase-8 activation and at least partly attenuated the consequent apoptosis, suggesting an involvement of FasL and its regulating pathway in the cell killing effect of UA. UA also inhibited cell invasion by downregulating matrix metalloproteinase-9 via inhibition of Akt in PC-3 cells. Although further evaluation of the UA effects in vivo is needed, the present results suggest the potential utility of UA as a novel therapeutic agent in advanced prostate cancer.

VDAC, a multi-functional mitochondrial protein regulating cell life and death

Research over the past decade has extended the prevailing view of the mitochondrion to include functions well beyond the generation of cellular energy. It is now recognized that mitochondria play a crucial role in cell signaling events, inter-organellar communication, aging, cell proliferation, diseases and cell death. Thus, mitochondria play a central role in the regulation of apoptosis (programmed cell death) and serve as the venue for cellular decisions leading to cell life or death. One of the mitochondrial proteins controlling cell life and death is the voltage-dependent anion channel (VDAC), also known as mitochondrial porin. VDAC, located in the mitochondrial outer membrane, functions as gatekeeper for the entry and exit of mitochondrial metabolites, thereby controlling cross-talk between mitochondria and the rest of the cell. VDAC is also a key player in mitochondria-mediated apoptosis. Thus, in addition to regulating the metabolic and energetic functions of mitochondria, VDAC appears to be a convergence point for a variety of cell survival and cell death signals mediated by its association with various ligands and proteins. In this article, we review what is known about the VDAC channel in terms of its structure, relevance to ATP rationing, Ca(2+) homeostasis, protection against oxidative stress, regulation of apoptosis, involvement in several diseases and its role in the action of different drugs. In light of our recent findings and the recently solved NMR- and crystallography-based 3D structures of VDAC1, the focus of this review will be on the central role of VDAC in cell life and death, addressing VDAC function in the regulation of mitochondria-mediated apoptosis with an emphasis on structure-function relations. Understanding structure-function relationships of VDAC is critical for deciphering how this channel can perform such a variety of functions, all important for cell life and death. This review also provides insight into the potential of VDAC1 as a rational target for new therapeutics.

Apoptosis is regulated by the VDAC1 N-terminal region and by VDAC oligomerization: release of cytochrome c, AIF and Smac/Diablo

Mitochondria, central to basic life functions due to their generation of cellular energy, also serve as the venue for cellular decisions leading to apoptosis. A key protein in mitochondria-mediated apoptosis is the voltage-dependent anion channel (VDAC), which also mediates the exchange of metabolites and energy between the cytosol and the mitochondria. In this study, the functions played by the N-terminal region of VDAC1 and by VDAC1 oligomerization in the release of cytochrome c, Smac/Diablo and apoptosis-inducing factor (AIF) and subsequent apoptosis were addressed. We demonstrate that cells undergoing apoptosis induced by STS or cisplatin and expressing N-terminally truncated VDAC1 do not release cytochrome c, Smac/Diablo or AIF. Ruthenium red (RuR), AzRu, DIDS and hexokinase-I (HK-I), all known to interact with VDAC, inhibited the release of cytochrome c, Smac/Diablo and AIF, while RuR-mediated inhibition was not observed in cells expressing RuR-insensitive E72Q-VDAC1. These findings suggest that VDAC1 is involved in the release of not only cytochrome c but also of Smac/Diablo and AIF. We also demonstrate that apoptosis induction is associated with VDAC oligomerization, as revealed by chemical cross-linking and monitoring in living cells using Bioluminescence Resonance Energy Transfer. Apoptosis induction by STS, H2O2 or selenite augmented the formation of VDAC oligomers several fold. The results show VDAC1 to be a component of the apoptosis machinery and offer new insight into the functions of VDAC1 oligomerization in apoptosis and of the VDAC1 N-terminal domain in the release of apoptogenic proteins as well as into regulation of VDAC by anti-apoptotic proteins, such as HK and Bcl2.

Ursolic acid overcomes Bcl-2-mediated resistance to apoptosis in prostate cancer cells involving activation of JNK-induced Bcl-2 phosphorylation and degradation

Androgen-independent prostate cancers express high levels of Bcl-2, and this over-expression of Bcl-2 protects prostate cancer cells from undergoing apoptosis. Ursolic acid (UA) has demonstrated an anti-proliferative effect in various tumor types. The aim of this study is to evaluate the difference between UA-induced apoptosis in androgen-dependent prostate cancer cell line LNCaP cells and androgen-independent prostate cancer cell line LNCaP-AI cells and to reveal the molecular mechanisms underlying the apoptosis. We found that UA treatment in vitro can effectively induce apoptosis in LNCaP and LNCaP-AI cells. UA can overcome Bcl-2-mediated resistance to apoptosis in LNCaP-AI cells. Intrinsic apoptotic pathways can be triggered by UA treatment because c-Jun N-terminal kinase (JNK) is activated and subsequently provokes Bcl-2 phosphorylation and degradation, inducing activation of caspase-9. Although further evaluation is clearly needed, the present results suggest the potential utility of UA as a novel therapeutic agent in advanced prostate cancer.

Asiatic acid induces colon cancer cell growth inhibition and apoptosis through mitochondrial death cascade

Cancer is one of the leading causes of death in the world. The triterpenoid compound asiatic acid derived from the tropical medicinal plant Centella asiatica displays cytotoxic activity on fibroblast cells and several other kinds of cells. The present work studies asiatic acid-mediated growth inhibition of cancer cells and the underlying mechanism. Asiatic acid markedly inhibited cancer cell proliferation. Apoptosis of SW480 human colon cancer cells was induced by asiatic acid as shown by flow cytometry, DNA fragmentation and nuclear chromatin condensation experiments. Through increasing mitochondrial membrane permeability and cytochrome c release from mitochondria into cytosol, asiatic acid induced caspase-9 activity, which further activated caspase-3 and poly(ADP-ribose) polymerase cleavage resulting in irreversible apoptotic death in the tumor cells. Taken together, these results suggest that mitochondrial death apoptosis cascade plays very important roles in asiatic acid-induced cancer apoptosis.

Uncovering the role of VDAC in the regulation of cell life and death

Proper cell activity requires an efficient exchange of molecules between mitochondria and cytoplasm. Lying in the outer mitochondrial membrane, VDAC assumes a crucial position in the cell, forming the main interface between the mitochondrial and the cellular metabolisms. As such, it has been recognized that VDAC plays a crucial role in regulating the metabolic and energetic functions of mitochondria. Indeed, down-regulation of VDAC1 expression by shRNA leads to a decrease in energy production and cell growth. VDAC has also been recognized as a key protein in mitochondria-mediated apoptosis through its involvement in the release of apoptotic proteins located in the inter-membranal space and as the proposed target of pro- and anti-apoptotic members of the Bcl2-family and of hexokinase. Questions, however, remain as to if and how VDAC mediates the transfer of apoptotic proteins from the inter-membranal space to the cytosol. The diameter of the VDAC pore is only about 2.5-3 nm, insufficient for the passage of a folded protein like cytochrome c. New work, however, suggests that pore formation involves the assembly of homo-oligomers of VDAC or hetero-oligomers composed of VDAC and pro-apoptotic proteins, such as Bax. Thus, VDAC appears to represent a convergence point for a variety of cell survival and cell death signals. This review provides insight into the central role of VDAC in mammalian cell life and death, emphasizing VDAC function in the regulation of mitochondria-mediated apoptosis and, as such, its potential as a rational target for new therapeutics.

Phosphorylation of Bcl-2 and activation of caspase-3 via the c-Jun N-terminal kinase pathway in ursolic acid-induced DU145 cells apoptosis

There is currently no successful therapy for androgen-independent prostate cancer. Ursolic acid (UA), a pentacyclic triterpenoid compound, has been shown to have an anti-proliferative effect on various tumors. We investigated the effect of UA on cell viability in the human hormone-refractory prostate cancer cell line DU145, as well as the molecular mechanisms underlying its growth inhibiting effect. We demonstrated that UA induces apoptosis and the activation of caspase-3 in DU145 cells. UA also causes the activation of c-Jun N-terminal kinase (JNK), but has no effect on extracellular signal-regulated protein kinases (ERK1/2) and p38 MAP kinases (p38). UA-induced JNK activation could result in Bcl-2 phosphorylation (Ser70) and degradation in DU145 cells, which may be one of the molecular mechanisms by which it induces apoptosis. Although further evaluation, such as in vivo testing, is clearly needed, the present results suggest the potential utility of UA as a novel therapeutic agent in advanced prostate cancer.

Characterization of a rare triterpenoid and minor phenolic compounds in the root bark of Anisophyllea dichostyla R. Br

Anisophyllea dichostyla R. Br. (Anisophylleaceae), is a small shrub which grows widely in regions of the Democratic Republic of Congo (DRC) where its root barks are used in folk medicine for the treatment of many debilitating diseases. In a previous work [Khallouki, F., Haubner, R., Hull, W.E., Erben, G., Spiegelhalder, B., Bartsch, H., Owen, R.W., 2007. Isolation, purification and identification of ellagic acid derivatives, catechins and procyanidins from the root barks of Anisophyllea dichostyla R. Br. Food and Chemical Toxicology 45, 472-485] on this species, an appreciable number (16) of phenolic antioxidants (3.32 g/kg) such as ellagitannins (27%) and polyhydroxyflavan-3-ols (catechins and procyanidins; 73%) were isolated and identified. Two fractions, as well as containing minor phenolic compounds also showed evidence of a secondary plant substance similar to a triterpenoid. Following purification of the triterpenoid by semi-preparative HPLC, and recrystallization, the structure was elucidated as bryonolic acid as evinced by comprehensive spectroscopic analyses including (1)H and (13)C NMR, DEPT, COSY, ROESY, HMQC, HMBC, HPLC-ESI-MS and GC-MS experiments. Bryonolic acid, which is extremely rare in nature, is therefore reported in the family Anisophylleaceae for the first time. Furthermore, the following minor phenolic compounds namely tyrosol, 2-(3-methoxy, 4-hydroxyphenyl)-ethanol, vanillin, syringaldehyde, vanillic acid, syringic acid, gallic acid and ferulic acid were also identified by GC-MS in this species for the first time.

Anticancer activities of cranberry phytochemicals: an update

Studies employing mainly in vitro tumor models show that extracts and compounds isolated from cranberry fruit (Vaccinium macrocarpon) inhibit the growth and proliferation of several types of tumor including breast, colon, prostate, and lung. Proanthocyanidin oligomers, flavonol and anthocyanin glycosides and triterpenoids are all likely contributors to the observed anticancer properties and may act in a complementary fashion to limit carcinogenesis. Possible chemopreventive mechanisms of action by cranberry phytochemicals include induction of apoptosis in tumor cells, reduced ornithine decarboxylase activity, decreased expression of matrix metalloproteinases associated with prostate tumor metastasis, and anti-inflammatory activities including inhibition of cyclooxygenases. A review of recent studies suggests a potential role for cranberry as a dietary chemopreventive and provides direction for future research.

Kalopanaxsaponin A induces apoptosis in human leukemia U937 cells through extracellular Ca2+ influx and caspase-8 dependent pathways

In the present study, we investigated the effect of KPS-A on the apoptotic activity and the molecular mechanism of the action in human leukemia. Treatment with KPS-A significantly increased apoptotic DNA fragmentation in human histiocytic lymphoma U937 cells as shown by DAPI staining, flow cytometry, and agarose gel electrophoresis. In addition, stimulation of U937 cell with KPS-A induced a series of intracellular events: (1) the activations of caspase-8, caspase-9, and caspase-3; (2) the translocations of Bid and Bax proteins to mitochondria; (3) the loss of mitochondrial membrane potential; and (4) the increased release of cytochrome c to the cytosol. Pretreatment with a specific caspases-8, -9 or -3 inhibitor, neutralized the pro-apoptotic activity of KPS-A in U937 cells. We further demonstrated that KPS-A markedly induced an increase in intracellular Ca2+ level, which was reversed by EGTA, a general calcium chelator, but not by TMB-8 and dantrolene, intracellular Ca2+ release blockers. Moreover, KPS-A-induced DNA fragmentation and caspase activation were substantially reduced in the presence of EGTA. Taken together, these results suggest that KPS-A may play therapeutic role for leukemia via the potent apoptotic activity through Ca2+/caspases-8/MPT/caspases-9/caspases-3 signaling pathway.

Anti-inflammatory and Cytotoxic Cycloartanes from Guayule (Parthenium Argentatum)

The need for the discovery and development of new pharmaceuticals for the treatment of cancer demands that all approaches to drug discovery should be exploited. Among the possible approaches, the one from natural products has made many unique and vital contributions to drug discovery. This mini review focuses on researches made in our laboratory on cycloartanes isolated from Parthenium argentatum, as well as some of its derivatives, in order to obtain potential anti-inflammatory and anti-cancer agents.

Mapping the ruthenium red-binding site of the voltage-dependent anion channel-1

We have previously shown that ruthenium red (RuR) binds to the voltage-dependent anion channel (VDAC) in the outer mitochondrial membrane, decreasing channel conductance and protecting against apoptotic cell death. In this report, we define the murine and yeast VDAC1 amino acid residues involved in the interaction with RuR. Binding of RuR to bilayer-reconstituted mVDAC1 and the resulting channel closure was inhibited upon mutation of specific VDAC1 residues. RuR protection against cell death, as induced by overexpression of native or mutated mVDAC1, was also diminished upon mutation of these amino acids. Moreover, RuR-mediated inhibition of cytochrome c release normally induced by staurosporine was not observed in cells expressing mutants VDAC1. We found that four glutamate residues, two each located in the first and third mVDAC1 cytosolic loops, are required for the interaction of VDAC1 with RuR and subsequent protection against cell death. Similar results were obtained with Q72E-yeast VDAC1, except that only three glutamate residues, located in two cytosolic loops were required. As a hexavalent reagent, RuR is expected to bind to more than one negatively charged group. Our results thus clearly indicate that RuR protects against cell death via a direct interaction with VDAC1 to inhibit cytochrome c release and subsequent cell death.