Gambogic acid reduced bcl-2 expression via p53 in human breast MCF-7 cancer cells

Gambogic acid induces GSDME dependent pyroptotic signaling pathway via ROS/P53/Mitochondria/Caspase-3 in ovarian cancer cells

Gambogic acid (GA) is a naturally active compound extracted from the Garcinia hanburyi with various anticancer activities. However, whether GA induces pyroptosis (a newly discovered inflammation-mediated programmed cell death mechanism) in ovarian cancer (OC) has not yet been reported. This study revealed that GA treatment reduced cell viability by inducing pyroptosis in OC cell lines. Typical pyroptosis morphological manifestations such as cell swelling with large bubbles and loss of cell membrane integrity, were observed. Cleaved caspase-3 and GSDME-N levels increased after GA treatment, and knocking out GSDME or using a caspase-3 inhibitor could switch GA-induced cell death from pyroptosis to apoptosis, indicating GA induced caspase-3/GSDME-dependent pyroptosis. Furthermore, this research indicated that GA significantly increased reactive oxygen species (ROS) and p53 phosphorylation. OC cells pretreated with ROS inhibitor N-Acetylcysteine (NAC) and the specific p53 inhibitor pifithrin-μ could completely reverse the pyroptosis post-treatment. Elevated p53 and phosphorylated p53 reduced mitochondrial membrane potential (MMP) and Bcl-2, increase the expression of Bax, and damage mitochondria by releasing cytochrome c to activate the downstream pyroptosis pathway. Different doses of GA inhibited tumor growth in ID8 tumor-bearing mice, and high-dose GA increased in tumor-infiltrating lymphocytes CD3, CD4, and CD8 were detected in tumor tissues. Notably, the expressions of GSDME-N, cleaved caspase-3 and other proteins were increased in tumor tissues with high-dose GA groups. These findings demonstrate that GA-treated OC cells could induce GSDME-mediated pyroptosis through the ROS/p53/mitochondria signaling pathway and caspase-3/-9 activation. Thus, GA is a promising therapeutic agent for OC treatment.

Mechanism of anticancer effect of gambogic acid on gastric signet ring cell carcinoma

Gambogic acid has demonstrated inhibitory effects on the growth of various cancer cell types, such as breast cancer, pancreatic cancer, prostate cancer, lung cancer, and osteosarcoma. This study aims to investigate the antiproliferative activity of Gambogic acid on SNU-16 cells derived from gastric signet ring cell carcinoma and elucidate the underlying mechanisms. The cytotoxic effect of gambogic acid was evaluated in SNU-16 cells by treating them with different concentrations of the compound, and the XTT cell viability assay was employed to assess cell viability. ELISA was used to measure bax, BCL-2, caspase 3, PARP, and 8-oxo-dG levels. Additionally, immunofluorescence staining was applied to assess 8-oxo-dG and LC3β levels in SNU-16 cells. It was observed that gambogic acid exerted a dose-dependent and statistically significant antiproliferative effect on SNU-16 cells. The IC50 value of gambogic acid in SNU-16 cells was found to be 655.1 nM for 24 h. Subsequent investigations conducted using the IC50 dose revealed a significant upregulation of apoptotic proteins including cleaved caspase 3, Bax, and cleaved PARP (p < 0.001), along with a downregulation of BCL-2 (p < 0.001), an anti-apoptotic protein. Moreover, the administration of this drug led to an upregulation of 8-oxo-dG (p < 0.001), a widely acknowledged biomarker indicating oxidative damage in DNA, as well as an increase in LC3β levels (p < 0.05), a marker associated with autophagy. The antiproliferative effect of gambogic acid against gastric signet ring cell carcinoma is attributed to its ability to induce apoptosis and autophagy. This discovery highlights the promising potential of gambogic acid as a treatment option for gastric signet ring cell carcinoma.

Optimization of amino acid-based poly(ester urea urethane) nanoparticles for the systemic delivery of gambogic acid for treating triple negative breast cancer

Amino acid-based poly(ester urea urethane) (AA-PEUU) is developed from amino acid-based ester urea building blocks interconnected with urethane blocks functionalized with poly(ethylene glycol) (PEG). Each functional block consists of structural design features that could impact the properties and performances of AA-PEUU as a nanocarrier for the systemic delivery of gambogic acid (GA). The multifunctional AA-PEUU structure provides broad tunability to enable the optimization of nanocarriers. The study investigates the structure-property relationship by fine-tuning the structure of AA-PEUU, including the amino acid type, hydrocarbons, the ratio of functional building blocks, and PEGylation, to identify the nanoparticle candidate with optimized delivery performances. Compared to free GA, the optimized PEUU nanocarrier improves the intratumoral distribution of GA by more than 9-fold, which significantly enhances the bioavailability and persistence of GA after intravenous administration. In an MDA-MB-231 xenograft mouse model, GA delivered by the optimized AA-PEUU nanocarrier exhibits significant tumor inhibition, apoptosis induction, and the anti-angiogenesis effect. The study demonstrates the potency of engineering AA-PEUU nanocarriers with tailor-designed structures and versatile tunability for the systemic delivery of therapeutics in the treatment of triple negative breast tumor.

Multiplexed Isobaric Quantitative Cross-Linking Reveals Drug-Induced Interactome Changes in Breast Cancer Cells

The study of protein structures and interactions is critical to understand their function. Chemical cross-linking of proteins with mass spectrometry (XL-MS) is a rapidly developing structural biology technique able to provide valuable insight into protein conformations and interactions, even as they exist within their native cellular environment. Quantitative analysis of cross-links can reveal protein conformational and interaction changes that occur as a result of altered biological states, environmental conditions, or pharmacological perturbations. Our laboratory recently developed an isobaric quantitative protein interaction reporter (iqPIR) cross-linking strategy for comparative interactome studies. This strategy relies on isotope encoded chemical cross-linkers that have the same molecular mass yet produce unique and specific isotope signatures upon fragmentation in the mass spectrometer which can be used for quantitative analysis of cross-linked peptides. The initial set of iqPIR molecules allowed for binary comparisons. Here, we describe the in vivo application of an extended set of six iqPIR reagents (6-plex iqPIR), allowing multiplexed quantitative interactome analysis of up to six biological samples in a single LC-MS acquisition. Multiplexed iqPIR is demonstrated on MCF-7 breast cancer cells treated with five different Hsp90 inhibitors revealing large scale protein conformational and interaction changes specific to the molecular class of the inhibitors.

Structural diversity and biological activities of caged Garcinia xanthones: recent updates

Caged xanthones are a class of natural compounds with approximately 200 members that are commonly isolated from the Garcinia genus in the Clusiaceae (formerly Guttiferae) family. They are often characterized by a notable 4-oxa-tricyclo[4.3.1.03,7]dec-2-one (caged) architecture with a common xanthone backbone. Because most caged xanthones have potent anticancer properties, they have become a target of interest in natural product chemistry. The unique chemical architectures and increasingly identified biological importance of these compounds have stimulated many studies and intense interest in their isolation, biological evaluation and mechanistic studies. This review summarizes recent progress and development in the chemistry and biological activity of caged Garcinia xanthones and of several compounds of non-Garcinia origin, from the years 2008 to 2021, providing an in-depth discussion of their structural diversity and medicinal potential. A preliminary discussion on structure-activity relationships is also provided.

Traditional Chinese medicine (TCM) as a source of new anticancer drugs

Covering: up to July 2020Drugs derived from traditional Chinese medicine (TCM) include both single chemical entities and multi-component preparations. Drugs of both types play a significant role in the healthcare system in China, but are not well-known outside China. The research and development process, the molecular mechanisms of action, and the clinical evaluation associated with some exemplificative anticancer drugs based on TCM are discussed, along with their potential of integration in western medicine.

Gambogic Acid as a Candidate for Cancer Therapy: A Review

Gambogic acid (GA), a kind of dry resin secreted by the Garcinia hanburyi tree, is a natural active ingredient with various biological activities, such as anti-cancer, anti-inflammatory, antioxidant, anti-bacterial effects, etc. An increasing amount of evidence indicates that GA has obvious anti-cancer effects via various molecular mechanisms, including the induction of apoptosis, autophagy, cell cycle arrest and the inhibition of invasion, metastasis, angiogenesis. In order to improve the efficacy in cancer treatment, nanometer drug delivery systems have been employed to load GA and form micelles, nanoparticles, nanofibers, and so on. In this review, we aim to offer a summary of chemical structure and properties, anti-cancer activities, drug delivery systems and combination therapy of GA, which might provide a reference to promote the development and clinical application of GA.

Gambogic acid: A shining natural compound to nanomedicine for cancer therapeutics

The United States Food and Drug Administration has permitted number of therapeutic agents for cancer treatment. Most of them are expensive and have some degree of systemic toxicity which makes overbearing in clinical settings. Although advanced research continuously applied in cancer therapeutics, but drug resistance, metastasis, and recurrence remain unanswerable. These accounts to an urgent clinical need to discover natural compounds with precisely safe and highly efficient for the cancer prevention and cancer therapy. Gambogic acid (GA) is the principle bioactive and caged xanthone component, a brownish gamboge resin secreted from the of Garcinia hanburyi tree. This molecule showed a spectrum of biological and clinical benefits against various cancers. In this review, we document distinct biological characteristics of GA as a novel anti-cancer agent. This review also delineates specific molecular mechanism(s) of GA that are involved in anti-cancer, anti-metastasis, anti-angiogenesis, and chemo-/radiation sensitizer activities. Furthermore, recent evidence, development, and implementation of various nanoformulations of gambogic acid (nanomedicine) have been described.

CD44 targeted redox-triggered self-assembly with magnetic enhanced EPR effects for effective amplification of gambogic acid to treat triple-negative breast cancer

Gambogic acid (GA) is a natural anti-tumor drug whose application is restricted by its poor aqueous solubility and inefficient bioavailability. Developing nanomaterials with excellent biocompatibility can amplify the therapeutic effects of GA. In this study, a tumor-targeted redox controllable self-assembled nano-system with magnetic enhanced EPR effects (mPEG-HA/CSO-SS-Hex/SPION/GA) was developed to improve the anticancer efficacy of GA. The nano-system is constituted by three layers: the outer layer is mono-aminated poly(ethylene glycol) grafted hyaluronic acid (mPEG-HA), which can target the CD44 receptor in breast cancer cells; the middle layer consists of disulfide linked hexadecanol (Hex) and chitosan oligosaccharide (CSO) to control the drug release by reduction response; the core layer is superparamagnetic iron oxide nanoparticles (SPION), which can enhance the EPR effect by magnetic guidance and contribute to GA entrapment. Different experiments were performed to characterize the complex self-assembly, and the cytotoxicity, pharmacokinetics, and in vivo antitumor activity of the self-assembly were investigated to evaluate its anti-tumor effects. The results revealed that mPEG-HA/CSO-SS-Hex/SPION/GA is an excellent nanosystem with appropriate size and sensitive responsiveness; it can accumulate in tumor sites and achieve excellent therapeutic effects on triple-negative breast cancer (TNBC). In summary, a CD44-targeted redox-triggered self-assembly nanosystem with magnetic enhanced EPR effects was developed for effective amplification of GA; it has potential to act as an effective carrier in drug delivery for chemotherapy of TNBC.

Dual Inhibitors as a New Challenge for Cancer Multidrug Resistance Treatment

BACKGROUND

Dual-targeting in cancer treatment by a single drug is an unconventional approach in relation to drug combinations. The rationale for the development of dualtargeting agents is to overcome incomplete efficacy and drug resistance frequently present when applying individual targeting agents. Consequently, -a more favorable outcome of cancer treatment is expected with dual-targeting strategies.

METHODS

We reviewed the literature, concentrating on the association between clinically relevant and/or novel dual inhibitors with the potential to modulate multidrug resistant phenotype of cancer cells, particularly the activity of P-glycoprotein. A balanced analysis of content was performed to emphasize the most important findings and optimize the structure of this review.

RESULTS

Two-hundred and forty-five papers were included in the review. The introductory part was interpreted by 9 papers. Tyrosine kinase inhibitors' role in the inhibition of Pglycoprotein and chemosensitization was illustrated by 87 papers. The contribution of naturalbased compounds in overcoming multidrug resistance was reviewed using 92 papers, while specific dual inhibitors acting against microtubule assembling and/or topoisomerases were described with 55 papers. Eleven papers gave an insight into a novel and less explored approach with hybrid drugs. Their influence on P-glycoprotein and multidrug resistance was also evaluated.

CONCLUSION

These findings bring into focus rational anticancer strategies with dual-targeting agents. Most evaluated synthetic and natural drugs showed a great potential in chemosensitization. Further steps in this direction are needed for the optimization of anticancer treatment.

A novel redox/pH dual-responsive and hyaluronic acid-decorated multifunctional magnetic complex micelle for targeted gambogic acid delivery for the treatment of triple negative breast cancer

Gambogic acid (GA) is a naturally derived potent anticancer agent with extremely poor biocompatibility. In the present study, a novel of redox/pH dual-responsive multifunctional magnetic complex micelle (sPEG/HA/CSO-SS-Hex/Fe₃O₄/GA), which consisted of a reducible hexadecanol-modified chitosan oligosaccharide polymer micelle (CSO-SS-Hex) coated with hyaluronic acid (HA) and DCA grafted sheddable PEG-PLL (sPEG) copolymers and loaded with gambogic acid (GA) and Fe₃O₄ nanoparticles were developed for parenteral delivery for the treatment of triple negative breast cancer (TNBC). The ex vivo study showed that the sPEG shielded cationic HA/CSO-SS-Hex/Fe₃O₄/GA core at physiological pH but quickly shed off to re-expose the core due to its charge reversible property. The sPEG/HA/CSO-SS-Hex/Fe₃O₄/GA micelles effectively facilitated tumor-targeted GA delivery by HA, which is a targeting ligand for CD44 receptor of TNBC cells, meanwhile increase GA uptake at the acidic condition but diminished the drug uptake at neutral pH. The in vitro cellular uptake study and in vivo biodistribution and antitumor activity of the formulations were determined, all results showed that the complex micelle enhanced TNBC tumor cellular uptake and fast drug release due to the combined effect of magnet targeting, CD44 receptor-mediated internalization and redox/pH dual-responsive drug release. Hence, tumor-targeted delivery of GA with redox/pH dual-responsive multifunctional magnetic complex micelle sPEG/HA/CSO-SS-Hex/Fe₃O₄/GA might have potential implications for the chemotherapy of TNBC.

Cell penetrating peptides functionalized gambogic acid-nanostructured lipid carrier for cancer treatment

Tumor-targeted delivery is considered a crucial component of current anticancer drug development and is the best approach to increase the efficacy and reduce the toxicity. Nanomedicine, particularly ligand-based nanoparticles have shown a great potential for active targeting of tumor. Cell penetrating peptide is one of the promising ligands in a targeted cancer therapy. In this study, the gambogic acid-loaded nanostructured lipid carrier (GA-NLC) was modified with two kinds of cell penetrating peptides (cRGD and RGERPPR). The GA-NLC was prepared by emulsification and solvent evaporation method and coupled with cRGD, RGERPPR, and combination cRGD and RGERPPR to form GA-NLC-cRGD, GA-NLC-RGE, and GA-NLC-cRGD/RGE, respectively. The formulations were characterized by their particle size and morphology, zeta potential, encapsulation efficiency, and differential scanning calorimetry. In vitro cytotoxicity and cellular uptake study of the formulations were performed against breast cancer cell (MDA-MB-231). Furthermore, in vivo biodistribution and antitumor activity of the formulations were determined by in vivo imaging and in tumor-bearing nude mice, respectively. The result of in vitro cytotoxicity study showed that GA-NLC-RGE exhibited a significantly higher cytotoxicity on MDA-MB-231 as compared with GA-NLC and GA-Sol. Similarly, RGE-Cou-6-NLC showed remarkably higher uptake by the cells than other NLCs over the incubation period. The in vivo imaging study has demonstrated that among the formulations, the RGE-decorated DiR-NLC were more accumulated in the tumor site. The in vivo antitumor activity revealed that RGE-GA-NLC inhibits the tumor growth more efficiently than other formulations. In conclusion, RGERPPR has a potential as an effective carrier in targeting drug delivery of anticancer agents.

Recent advances in inhibitors of sirtuin1/2: an update and perspective

Sirtuins (SIRT) are coenzyme NAD+-dependent histone deacetylases for the transfer of modified acetyl groups. Sirtuins are widely involved in various physiological processes and therefore associated with cardiovascular disease, diabetes, Parkinson's disease, cancer and beyond. Consequently, the development of modulators for  sirtuins has considerable clinical value. To date, a variety of SIRT1/2 inhibitors have been reported and none has been approved for the market. This review summarizes the recent progress in the discovery and development of SIRT1/2 inhibitors including their inhibitory potency, structure–activity relationship and binding mode analysis as well as discusses the perspective for the future development of SIRT1/2 inhibitors.

Therapeutic potential of gambogic acid, a caged xanthone, to target cancer

Natural compounds have enormous biological and clinical activity against dreadful diseases such as cancer, as well as cardiovascular and neurodegenerative disorders. In spite of the widespread research carried out in the field of cancer therapeutics, cancer is one of the most prevalent diseases with no perfect treatment till date. Adverse side effects and the development of chemoresistance are the imperative limiting factors associated with conventional chemotherapeutics. For this reason, there is an urgent need to find compounds that are highly safe and efficacious for the prevention and treatment of cancer. Gambogic acid (GA) is a xanthone structure extracted from the dry, brownish gamboge resin secreted from the Garcinia hanburyi tree in Southeast Asia and has inherent anti-cancer properties. In this review, the molecular mechanisms underlying the targets of GA that are liable for its effective anti-cancer activity are discussed that reveal the potential of GA as a pertinent candidate that can be appropriately developed and designed into a capable anti-cancer drug.

Inclusion complex from cyclodextrin-grafted hyaluronic acid and pseudo protein as biodegradable nano-delivery vehicle for gambogic acid

β-Cyclodextrin can form inclusion complex with a series of guest molecules including phenyl moieties, and has gained considerable popularity in the study of supramolecular nanostructure. In this study, a biodegradable nanocomplex (HA(CD)-4Phe4 nanocomplex) was developed from β-cyclodextrin grafted hyaluronic acid (HA) and phenylalanine based poly(ester amide). The phenylalanine based poly(ester amide) is a biodegradable pseudo protein which provides the encapsulation capacity for gambogic acid (GA), a naturally-derived chemotherapeutic which has been effectively employed to treat multidrug resistant tumor. The therapeutic potency of free GA is limited due to its poor solubility in water and the lack of tumor-selective toxicity. The nanocomplex carrier enhanced the solubility and availability of GA in aqueous media, and the HA component enabled the targeted delivery to tumor cells with overexpression of CD44 receptors. In the presence of hyaluronidase, the release of GA from the nanocomplex was significantly accelerated, due to the enzymatic biodegradation of the carrier. Compared to free GA, GA-loaded nanocomplex exhibited improved cytotoxicity in MDA-MB-435/MDR multidrug resistant melanoma cells, and induced enhanced level of apoptosis and mitochondrial depolarization, at low concentration of GA (1-2µM). The nanocomplex enhanced the therapeutic potency of GA, especially when diluted in physiological environment. In addition, suppressed matrix metalloproteinase activity was also detected in MDA-MB-435/MDR cells treated by GA-loaded nanocomplex, which demonstrated its potency in the inhibition of tumor metastasis. The in vitro data suggested that HA(CD)-4Phe4 nanocomplex could provide a promising alternative in the treatment of multidrug resistant tumor cells.

STATEMENT OF SIGNIFICANCE

Gambogic acid (GA), naturally derived from genus Garcinia trees, exhibited significant cytotoxic activity against multiple types of tumors with resistance to traditional chemotherapeutics. Unfortunately, the poor solubility of GA in conventional pharmaceutical solvents and non-targeted distribution in normal tissues greatly limited its therapeutic potency. To overcome the challenges, we develop a nanoplatform from the supramolecular assembly of β-cyclodextrin grafted hyaluronic acid (HA) and phenylalanine based pseudo protein. The pseudo protein in the nanocomplex provided the hydrophobic interaction and loading capacity for GA, while the HA component targeted the overexpressed CD44 receptor and improved the selective endocytosis in multidrug resistant melanoma cells. The supramolecular nanocomplex provide a promising platform for the delivery of hydrophobic chemotherapeutics to improve the bioavailability and efficiency.

Gambogic Acid Induces Cell Apoptosis and Inhibits MAPK Pathway in PTEN-/-/p53-/- Prostate Cancer Cells In Vitro and Ex Vivo

OBJECTIVE

To investigate the effect of gambogic acid (GA) on the growth and cell death of castrate resistant prostate cancer (PC) with phosphate and tension homology (PTEN) and p53 genes deleted in vitro and ex vivo, and elucidate the underlying possible molecular mechanisms.

METHODS

PTEN^-/-/p53^-/- PC cells and Los Angeles prostate cancer-4 (LAPC-4) cells were treated with GA for 24 h and 48 h, then cell viability was determined by cell proliferation assay. PTEN^-/-/p53^-/- PC cells organoids number was calculated under GA treatment for 1 week. In addition, cell titer glo assay was performed to analyze 3 dimensional cell viability of patients derived xenografts (PDX) 170.2 organoids. Flow cytometry was used to detect apoptotic cells treated with GA. And confocal image was performed to detect the apoptotic mitochondrial morphological changes. Apoptotic cell death related protein levels were measured through Western blot (WB) in GA treated cells and organoids. The expression levels of mitogen-activated protein kinases (MAPKs) pathway related ribonucleic acid (RNAs) and proteins were analyzed by reverse transcription polymerase chain reaction (RT-PCR) and WB, respectively.

RESULTS

The treatment of GA significantly reduced cell viability of PTEN^-/-/p53^-/- PC cells and LAPC-4 in a time- and concentration-dependent manner. In organoids, GA showed strong inhibition towards organoids' numbers and diameters and continuously led to a complete organoids inhibition with GA 150 nmol/L. Ex vivo results validated that GA 1 μmol/L inhibited 44.6% PDX170.2 organoids growth. As for mechanism, flow cytometry detected continuously increased apoptotic portion under GA treatment from 1.98% to 11.78% (6 h) and 29.94% (8 h, P<0.05). In addition, mitochondrial fragmentation emerged in GA treated cells indicated the mitochondrial apoptotic pathway might be involved. Furthermore, WB detected caspases-3, -9 activation and light chain (LC)-3 conversion with GA treatment. WB revealed decreased activity of MAPK pathway and down-regulation of downstream c-fos oncogene RNA level was detected by RT-PCR before undergoing apoptosis (P<0.05).

CONCLUSION

GA was a potent anti-tumor compound as for PTEN^-/-/p53^-/- PC, which contributed to cell apoptosis via inhibition of the MAPK pathway and c-fos.

Phaleria macrocarpa (Boerl.) fruit induce G0/G1 and G2/M cell cycle arrest and apoptosis through mitochondria-mediated pathway in MDA-MB-231 human breast cancer cell

ETHNOPHARMACOLOGICAL RELEVANCE

Phaleria macrocarpa (Scheff) Boerl, is a well-known folk medicinal plant in Indonesia. Traditionally, P. macrocarpa has been used to control cancer, impotency, hemorrhoids, diabetes mellitus, allergies, liver and hearth disease, kidney disorders, blood diseases, acne, stroke, migraine, and various skin diseases.

AIM OF THE STUDY

The purpose of this study was to determine the in situ cytotoxicity effect P. macrocarpa fruit ethyl acetate fraction (PMEAF) and the underlying molecular mechanism of cell death.

MATERIALS AND METHODS

MDA-MB-231 cells were incubated with PMEAF for 24h. Cell cycle and viability were examined using flow cytometry analysis. Apoptosis was determined using the Annexin V assay and also by fluorescence microscopy. Apoptosis protein profiling was detected by RayBio® Human Apoptosis Array.

RESULTS

The AO/PI staining and flow cytometric analysis of MDA-MB-231 cells treated with PMEAF were showed apoptotic cell death. The cell cycle analysis by flow cytometry analysis revealed that the accumulation of PMEAF treated MDA-MB-231 cells in G₀/G₁ and G₂/M-phase of the cell cycle. Moreover, the PMEAF exert cytotoxicity by increased the ROS production in MDA-MB-231 cells consistently stimulated the loss of mitochondrial membrane potential (∆_Ψm) and induced apoptosis cell death by activation of numerous signalling proteins. The results from apoptosis protein profiling array evidenced that PMEAF stimulated the expression of 9 pro-apoptotic proteins (Bax, Bid, caspase 3, caspase 8, cytochrome c, p21, p27, p53 and SMAC) and suppressed the 4 anti-apoptotic proteins (Bcl-2, Bcl-w, XIAP and survivin) in MDA-MB-231 cells.

CONCLUSION

The results indicated that PMEAF treatment induced apoptosis in MDA-MB-231 cells through intrinsic mitochondrial related pathway with the participation of pro and anti-apoptotic proteins, caspases, G₀/G₁ and G₂/M-phases cell cycle arrest by p53-mediated mechanism.

Gambogic acid counteracts mutant p53 stability by inducing autophagy

Mutant p53 (mutp53) proteins are frequently present at higher levels than the wild-type (wt) protein in tumors, and some of them can acquire oncogenic properties. Consistently, knockdown of mutp53 protein in human cancer cell lines leads to reduced cell proliferation and invasion as well as to an increased sensitivity to some anticancer drugs. Therefore, the exploitation of cellular pathways and/or molecules that promote mutp53 degradation may have a therapeutic interest. Recently, autophagy is emerging as an important pathway involved in the stability of mutp53. In this paper, we explored the autophagic potential of gambogic acid (GA), a molecule that stimulates the degradation of mutp53 and increases the sensitivity of cancer cells to chemotherapeutic agents. We demonstrated that GA may induce mutp53 degradation through autophagy in cancer cells expressing the p53-R280K (MDA-MB-231) and the p53-S241F (DLD1) proteins. The inhibition of autophagy with bafilomycin A1 or chloroquine counteracted mutp53 degradation by GA. However, the autophagy induction and mutp53 degradation affected cell survival and proliferation only at low GA concentrations. At higher GA concentrations, when cells undergo massive apoptosis, autophagy is no longer detectable by immuno-fluorescence analysis. We concluded that autophagy is a relevant pathway for mutp53 degradation in cancer cells but it contributes only partially to GA-induced cell death, in a time and dose-dependent manner.

Tumor neovasculature-targeted cationic PEGylated liposomes of gambogic acid for the treatment of triple-negative breast cancer

Gambogic acid (GA) is a naturally derived potent anticancer agent with extremely poor aqueous solubility. In the present study, positively charged PEGylated liposomal formulation of GA (GAL) was developed for parenteral delivery for the treatment of triple-negative breast cancer (TNBC). The GAL was formulated with a particle size of 107.3 ± 10.6 nm with +32 mV zeta potential. GAL showed very minimal release of GA over 24 h period confirming the non-leakiness and stability of liposomes. In vitro cytotoxicity assays showed similar cell killing with GA and GAL against MDA-MB-231 cells but significantly higher inhibition of HUVEC growth was observed with GAL. Furthermore, GAL significantly (p < 0.05) inhibited the MDA-MB-231 orthotopic xenograft tumor growth with >50% reduction of tumor volume and reduction in tumor weight by 1.7-fold and 2.2-fold when compared to GA and controls, respectively. Results of western blot analysis indicated that GAL significantly suppressed the expression of apoptotic markers, bcl2, cyclinD1, survivin and microvessel density marker-CD31 and increased the expression of p53 and Bax compared to GA and control. Collectively, these data provide further support for the potential applications of cationic GAL in its intravenous delivery and its significant role in inhibiting angiogenesis against TNBC.

How much successful are the medicinal chemists in modulation of SIRT1: A critical review

Silent information regulator two homologue one (SIRT1) is the most widely studied member of the sirtuin family related to histone deacetylases class III super-family using nicotinamide adenine dinucleotide (NAD(+)) as its cofactor. It is located in the nucleus but also modulates the targets in cytoplasm and mainly acts as transacetylase rather than deacetylase. SIRT1 specifically cleaves the nicotinamide ribosyl bond of NAD(+) and transfers the acetyl group from proteins to their co-substrate through an ADP- ribose-peptidyl imidate intermediate. It has been indicated that SIRT1 and its histone as well as non histone targets are involved in a wide range of biological courses including metabolic diseases, age related diseases, viral infection, inflammation, tumor-cell growth and metastasis. Modulation of SIRT1 expression may present a new insight in the discovery of a number of therapeutics. This review summarizes studies about SIRT1 and mainly focuses on the various modulators of SIRT1 evolved by natural as well as synthetic means.

Apoptotic effect of gambogic acid in esophageal squamous cell carcinoma cells via suppression of the NF-κB pathway

Despite extensive investigations of therapeutic improvements for surgical techniques, chemotherapy and chemoradiotherapy, esophageal squamous cell carcinoma (ESCC) remains one of the most aggressive forms of cancer, and the prognosis for patients with advanced ESCC remains poor. Therefore, effective therapies are urgently required in order to improve the prognosis of patients with ESCC. TE-1 cells were treated with gambogic acid (GA), and then subjected to western blot analysis, TUNEL assay and caspase activity analysis. GA significantly induced apoptosis in ESCC TE-1 cells. In addition, the antitumor activity of GA was accompanied by the decreased expression of phosphorylated-protein kinase B (p-AKT) and nuclear factor of κ light polypeptide gene enhancer in B-cells 1 (NF-κB). The inhibition of protein kinase B (AKT) and NF-κB activation by chemical inhibitors augmented the apoptotic effect responses to GA in the TE-1 cells. The pan-caspase inhibitor z-VAD-fmk (zVAD) decreased GA-induced apoptosis. Furthermore, zVAD attenuated GA-induced growth inhibition in TE-1 cells. GA induced apoptosis in ESCC TE-1 via suppression of NF-κB pathway. The findings of the present study may provide a novel insight into ESCC treatment.

Recent research on bioactive xanthones from natural medicine: Garcinia hanburyi

Garcinia hanburyi, a tropical plant found in south Asia, has a special long history in the development of both medicine and art. This review mainly focuses on the pharmacy research of the bioactive compounds from the plant in recent years. Preparative and analysis separation methods were introduced. Moreover, the chemical structure of the isolated compounds was included. The studies of biological activities of the caged xanthones from the plant, including antitumor, anti-HIV-1, antibacterial, and neurotrophic activities, were reviewed in detail. Furthermore, the mechanisms of its antitumor activity were also reviewed. As mentioned above, some of the xanthones from G. hanburyi can be promising drug candidates, which is worth studying. However, we still need much evidence to prove their efficacy and safety. So, further research is critical for the future application of xanthones from G. hanburyi.

Gambogic acid induces apoptosis and inhibits colorectal tumor growth via mitochondrial pathways

AIM: To investigate the effect of gambogic acid (GA) on apoptosis in the HT-29 human colon cancer cell line.

METHODS: H-29 cells were used for in vitro experiments in this study. Relative cell viability was assessed using MTT assays. Cell apoptosis was detected by terminal deoxynucleotidyl transferase dUTP nick end labeling and Hoechst 33342 staining, and quantified by flow cytometry. Cellular ultrastructure was observed by transmission electron microscopy. Real-time PCR and Western blot analyses were used to evaluate gene and protein expression levels. For in vivo experiments, BALB/c nude mice received subcutaneous injections of HT-29 cells in the right armpit. When well-established xenografts were palpable with a tumor size of 75 mm³, mice were randomly assigned to a vehicle (negative) control, positive control or GA treatment group (n = 6 each). The animals in the treatment group received one of three dosages of GA (in saline; 5, 10 or 20 mg/kg) via the caudal vein twice weekly, whereas animals in the negative and positive control groups were given equal volumes of 0.9% saline or 10 mg/kg docetaxel, respectively, via the caudal vein once weekly.

RESULTS: The cell viability assay showed that GA inhibited proliferation of HT-29 cells in a dose- and time-dependent manner after treatment with GA (0.00, 0.31, 0.62, 1.25, 2.50, 5.00 or 10.00 μmol/L) for 24, 48 or 72 h. After 48 h, the percentage of apoptotic cells in cells treated with 0.00, 1.25, 2.50 and 5.00 μmol/L GA was 1.4% ± 0.3%, 9.8% ± 1.2%, 25.7% ± 3.3% and 49.3% ± 5.8%, respectively. Ultrastructural analysis of HT-29 cells treated for 48 h with 2.5μmol/L GA revealed apoptotic bodies and condensed and fragmented nuclei. Levels of caspase-8, -9 and -3 mRNAs were significantly increased after treatment with GA (1.25, 2.50 or 5.00 μmol/L) for 48 h (P < 0.05 for all). Protein levels of apoptosis-related factors Fas, FasL, FADD, cytochrome c, and Apaf-1 were increased in GA-treated cells, whereas levels of pro-caspase-8, -9 and -3 were significantly decreased (P < 0.05 for all). Furthermore, GA significantly and dose-dependently inhibited the growth of HT-29 tumors in a mouse xenograft model (P < 0.05).

CONCLUSION: GA inhibits HT-29 proliferation via induction of apoptosis. The anti-cancer effects are likely mediated by death receptor (extrinsic) and mitochondrial (intrinsic) pathways.

Resveratrol inhibits the proliferation of human melanoma cells by inducing G1/S cell cycle arrest and apoptosis

Resveratrol (Res), a natural plant extract, is an effective inducer of cell apoptosis and cell cycle arrest in multiple carcinoma cell types, which has been demonstrated by its ability to inhibit the proliferation of multiple human tumor cells in vitro. Although Res possesses chemopreventive properties against several types of cancer, the molecular mechanism underlying its anticancer activity remains to be fully elucidated. The present study demonstrated that Res induced cell cycle arrest and inhibited the proliferation of human melanoma A375 (IC50=23 µM after 48 h; P<0.05) and SK-MEL-31 (IC50=15 µM after 48 h; P<0.05) cells. Western blot analysis demonstrated that Res induced the apoptosis of human melanoma A375 and SK-MEL-31 cells by upregulating the expression of Bcl-2-associated X protein and B-cell lymphoma 2, possibly via the p53 pathway and activation of caspase-9 and caspase-3.

Apoptosis in glioma-bearing rats after neural stem cell transplantation

Abnormal activation of the Ras/Raf/Mek/Erk signaling cascade plays an important role in glioma. Inhibition of this aberrant activity could effectively hinder glioma cell proliferation and promote cell apoptosis. To investigate the mechanism of glioblastoma treatment by neural stem cell transplantation with respect to the Ras/Raf/Mek/Erk pathway, C6 glioma cells were prepared in suspension and then infused into the rat brain to establish a glioblastoma model. Neural stem cells isolated from fetal rats were then injected into the brain of this glioblastoma model. Results showed that Raf-1, Erk and Bcl-2 protein expression significantly increased, while Caspase-3 protein expression decreased. After transplantation of neural stem cells, Raf-1, Erk and Bcl-2 protein expression significantly decreased, while Caspase-3 protein expression significantly increased. Our findings indicate that transplantation of neural stem cells may promote apoptosis of glioma cells by inhibiting Ras/Raf/Mek/Erk signaling, and thus may represent a novel treatment approach for glioblastoma.

Gambogic acid inhibits multiple myeloma mediated osteoclastogenesis through suppression of chemokine receptor CXCR4 signaling pathways

Bone disease, characterized by the presence of lytic lesions and osteoporosis is the hallmark of multiple myeloma (MM). Stromal cell-derived factor 1α (SDF-1α) and its receptor, CXC chemokine receptor 4 (CXCR4), has been implicated as a regulator of bone resorption, suggesting that agents that can suppress SDF1α/CXCR4 signaling might inhibit osteoclastogenesis, a process closely linked to bone resorption. We, therefore, investigated whether gambogic acid (GA), a xanthone, could inhibit CXCR4 signaling and suppress osteoclastogenesis induced by MM cells. Through docking studies we predicted that GA directly interacts with CXCR4. This xanthone down-regulates the expression of CXCR4 on MM cells in a dose- and time-dependent manner. The down-regulation of CXCR4 was not due to proteolytic degradation, but rather GA suppresses CXCR4 mRNA expression by inhibiting nuclear factor-kappa B (NF-κB) DNA binding. This was further confirmed by quantitative chromatin immunoprecipitation assay, as GA inhibits p65 binding at the CXCR4 promoter. GA suppressed SDF-1α-induced chemotaxis of MM cells and downstream signaling of CXCR4 by inhibiting phosphorylation of Akt, p38, and Erk1/2 in MM cells. GA abrogated the RANKL-induced differentiation of macrophages to osteoclasts in a dose- and time-dependent manner. In addition, we found that MM cells induced differentiation of macrophages to osteoclasts, and that GA suppressed this process. Importantly, suppression of osteoclastogenesis by GA was mediated through IL-6 inhibition. Overall, our results show that GA is a novel inhibitor of CXCR4 expression and has a strong potential to suppress osteoclastogenesis mediated by MM cells.

Capilliposide Isolated from Lysimachia capillipes Hemsl. Induces ROS Generation, Cell Cycle Arrest, and Apoptosis in Human Nonsmall Cell Lung Cancer Cell Lines

Several data has reported that capilliposide, extracted from a traditional Chinese medicine, Lysimachia capillipes Hemsl. (LC) could exhibit inhibitory effect on cell proliferation in various cancers. The current study investigated the antitumor efficacy of Capilliposide and elucidated its potential molecular mechanism involved in vivo and vitro. Our results indicated that LC capilliposide inhibited proliferation of lung cancer cells in a dose-dependent manner. LC capilliposide induced cell cycle arrest at the S stage and enhanced apoptosis in NSCLC cells. Treatment with LC capilliposide increased the intracellular level of ROS, which activated the mitochondrial apoptotic pathway. Blockage of ROS by NAC highly reversed the effect of LC capilliposide on apoptosis. Xenograft tumor growth was significantly lower in the LC-treated group compared with the untreated control group (P < 0.05). The results also show that LC treatment does not produce any overt signs of acute toxicity in vivo. These findings demonstrate that LC capilliposide could exert an anti-tumor effect on NSCLC through mitochondrial-mediated apoptotic pathway and the activation of ROS is involved.

Dihydromyricetin reduced Bcl-2 expression via p53 in human hepatoma HepG2 cells

Dihydromyricetin (DHM) is a major active ingredient of flavonoids compounds. It exhibited anticancer activity and induced apoptosis in human hepatocellular carcinoma HepG2 cells according to our previous data. In this study, we investigated whether p53 is involved in DHM-triggered viability inhibition and apoptosis induction in cancer cells. MTT [3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide] assay was employed to evaluate the viability of HepG2 cells after DHM treatment. Meanwhile, p53 small interfering RNA (siRNA) was adopted to silence p53 expression. Protein level of p53 and Bax/Bcl-2 were evaluated by western blot analysis. Cell counting assay showed that DHM inhibited HepG2 cell growth effectively in a time- and dose-dependent manner. P53 expression was significantly increased after DHM treatment, whereas Bcl-2 was reduced potently. Furthermore, after co-treatment with Pifithrin-α (PFT-α, p53 inhibitor), Bcl-2 expression was reversed. The expression of Bax was no significant change, which was also observed after p53 silence. These findings defined and supported a novel function that DHM could induce human hepatocellular carcinoma HepG2 cells apoptosis by up-regulating Bax/Bcl-2 expression via p53 signal pathway.

Synergetic effect of functional cadmium-tellurium quantum dots conjugated with gambogic acid for HepG2 cell-labeling and proliferation inhibition

We prepared and studied novel fluorescent nanocomposites based on gambogic acid (GA) and cadmium–tellurium (CdTe) quantum dots (CdTe QDs) modified with cysteamine for purpose of cancer cell labeling and combined treatment. The nanocomposites were denoted as GA-CdTe. Characterization results indicated that the CdTe QDs can readily bind onto cell plasma membranes and then be internalized into cancer cells for real-time labeling and tracing of human liver hepatocellular carcinoma cell line (HepG2) cells. GA-CdTe significantly enhanced drug accumulation in HepG2 cells and inhibited cancer cell proliferation. GA-CdTe nanocomposites also improved the drug action of GA molecules in HepG2 cells and induced the G₂/M phase arrest of the cancer cell cycle, promoting cell apoptosis. Given the sensitive, pH-triggered release of GA-CdTe, the side effects of GA anticancer agents on normal cells/tissues in the blood circulation markedly decreased. Efficient drug release and accumulation in target tumor cells were also facilitated. Thus, the fluorescent GA-CdTe offered a new strategy for potential multimode cancer therapy and provided new channels for research into naturally-active compounds extracted from traditional Chinese medicinal plants.

N-octyl-N-arginine-chitosan (OACS) micelles for gambogic acid oral delivery: preparation, characterization and its study on in situ intestinal perfusion

CONTEXT

Gambogic acid (GA) can inhibit the growth of various cancer cells. However, the low bioavailability caused by insolubility, limits its clinical application. L-arginine is always used with GA to form a complex to obtain the higher solubility. Moreover, guanidyl group from arginine, which can facilitate the cellular uptake, was identified.

OBJECTIVE

In this study, L-arginine and chitosan (CS) were used for the first time to prepare N-octyl-N-arginine CS (OACS), a novel amphiphilic carrier for GA with solubility- and absorption-enhancing functions; the characterization of the GA loaded OACS micelles (GA-OACS) and its absorption-enhancing effect were also investigated.

MATERIALS AND METHODS

GA-OACS were prepared by the dialysis method. The formed micelles were characterized and evaluated by atomic force microscope (AFM), dynamic light scattering, differential scanning calorimeter (DSC), solubility test, in vitro release and in situ intestinal perfusion.

RESULTS

The GA-OACS micelles were successfully prepared attaining a 35.3% drug loading and 82.2% entrapment efficiency. GA-OACS had a homogeneous particle size of 160.3 nm; +21.8 mv zeta potential with smooth continuous surface was observed by using AFM. DSC diagram suggested that GA was encapsulated in the micelles. Meanwhile, GA encapsulated in micelles exhibited a desirable slow release in vitro experiment. The solubility of GA in OACS micelles was increased up to 3.16 ± 0.13 mg/mL, 2320 times than that of free GA. The single pass perfusion showed that the absorption of GA-OACS micelles was enhanced 3.6-fold, 2.1-fold and 2.2-fold for jejunum, ileum and colon, respectively.

DISCUSSION AND CONCLUSION

OACS provided excellent ability of drug loading, increasing solubility and enhanced absorption for GA, which indicated that OACS micelles as an oral drug delivery carrier may have potential research and application values.

Gambogic acid induces mitochondria-dependent apoptosis by modulation of Bcl-2 and Bax in mantle cell lymphoma JeKo-1 cells

OBJECTIVE

To study the mechanisms in gambogic acid (GA) -induced JeKo-1 human Mantle Cell Lymphoma cell apoptosis in vitro.

METHODS

The proliferation of GA-treated JeKo-1 cells was measured by CCK-8 assay and Ki-67 immunocytochemical detection. Apoptosis, cell cycle and mitochondrial membrane potential were measured by flow cytometric analysis. Caspase-3, -8 and -9 were detected by colorimetric assay. Bcl-2 and Bax were analyzed by Western blotting.

RESULTS

GA inhibited cell growth in a time- and dose- dependent manner. GA induces apoptosis in JeKo-1 cells but not in normal bone marrow cells, which was involved in reducing the membrane potential of mitochondria, activating caspases-3, -8 and -9 and decreasing the ratio of Bcl-2 and Bax without cell cycle arresting.

CONCLUSIONS

GA induced apoptosis in human MCL JeKo-1 cells by regulating Bcl-2/Bax and activating caspase-3, -8 and -9 via mitochondrial pathway without affecting cell cycle.

Studies on lactoferrin nanoparticles of gambogic acid for oral delivery

PURPOSE

Lactoferrin (Lf), a mammalian cationic iron-binding glycoprotein belonging to the transferrin (Tf) family, has been widely used in a variety of fields ranging from treating infant diarrhea and supporting newborn growth to food and pharmaceutical applications. In this study, Lf nanoparticles were firstly used as carriers of gambogic acid (GA) to enhance oral absorption and anti-cancer activity, hence reducing the related toxic effect.

METHODS

Gambogic acid-lactoferrin nanoparticles (GL-NPs) were prepared by the nanoparticle albumin-bound (NAB) technology. The formed nanoparticles were characterized by DSC, TEM, etc. In situ intestinal perfusion experiment was performed to clarify the absorption mechanism of GL-NPs. Furthermore in vivo and in vitro anti-tumor activities of GL-NPs were also investigated.

RESULTS

GL-NPs was successfully prepared with about 150 nm mean size, +20 mV ζ potential, 92.3 ± 7.2% encapsulation efficiency and 9.04 ± 0.7% DL; GL-NPs also exhibited a better stability and a desirable slow release in vitro experiment. The results of in situ intestinal perfusion showed a transformation of GA absorption from passive diffusion into active transport or facilitated diffusion by GL-NPs. MTT assay of GL-NPs showed almost an equal anti-proliferative effect with arginine solution of GA (Arg-GA) in HepG2 cell. The inhibitory rate against S180 tumor mice after oral administration of GL-NPs was up to 86.01% which was 1.39-folds of intravenous injection of Arg-GA.

CONCLUSION

The in vitro results showed that the NAB technology was feasible for industrial production of Lf nanoparticles and the in vivo results proved that the effective GL-NPs is a promising approach for the oral delivery of GA. These obtained research works have also paved the preliminary way for the study of Lf as an oral drug delivery carrier.

Gambogic acid promotes apoptosis and resistance to metastatic potential in MDA-MB-231 human breast carcinoma cells

Gambogic acid (GA) is considered a potent anti-tumor agent for its multiple effects on cancer cells in vitro and in vivo. Low concentrations of GA (0.3-1.2 µmol/L) can suppress invasion of human breast carcinoma cells without affecting cell viability. To get a whole profile of the inhibition on breast cancers, higher concentrations of GA and spontaneous metastatic animal models were employed. Treatment with GA (3 and 6 µmol/L) induced apoptosis in MDA-MB-231 cells and the accumulation of reactive oxygen species (ROS). Furthermore, GA induced PARP cleavage, activation of caspase-3, caspase-8, and caspase-9, as well as an increased ratio of Bax/Bcl-2. Moreover, the translocation of apoptotic inducing factor (AIF) and the release of cytochrome c (Cyt c) from mitochondria were observed, indicating that GA induced apoptosis through accumulation of ROS and mitochondrial apoptotic pathway. GA also inhibited cell survival via blocking Akt/mTOR signaling. In vivo, GA significantly inhibited the xenograft tumor growth and lung metastases in athymic BALB/c nude mice bearing MDA-MB-231 cells. Collectively, these data provide further support for the multiple effects of GA on human breast cancer cells, as well as for its potential application to inhibit tumor growth and prevent metastasis in human cancers.

Synergistic effect of a combination of nanoparticulate Fe3O4 and gambogic acid on phosphatidylinositol 3-kinase/Akt/Bad pathway of LOVO cells

Background:

The present study evaluated whether magnetic nanoparticles containing Fe₃O₄ could enhance the activity of gambogic acid in human colon cancer cells, and explored the potential mechanisms involved.

Methods:

Cytotoxicity was evaluated by MTT assay. The percentage of cells undergoing apoptosis was analyzed by flow cytometry, and cell morphology was observed under both an optical microscope and a fluorescence microscope. Reverse transcriptase polymerase chain reaction and Western blot assay were performed to determine the transcription of genes and expression of proteins, respectively.

Results:

Gambogic acid could inhibit proliferation of LOVO cells in a dose-dependent and time-dependent manner and induce apoptosis, which was dramatically enhanced by magnetic nanoparticles containing Fe₃O₄. The typical morphological features of apoptosis in LOVO cells were observed after treatment comprising gambogic acid with and without magnetic nanoparticles containing Fe₃O₄. Transcription of cytochrome c, caspase 9, and caspase 3 genes was higher in the group treated with magnetic nanoparticles containing Fe₃O₄ and gambogic acid than in the groups that received gambogic acid or magnetic nanoparticles containing Fe₃O₄, but transcription of phosphatidylinositol 3-kinase, Akt, and Bad genes decreased. Notably, expression of cytochrome c, caspase 9, and caspase 3 proteins in the group treated with gambogic acid and magnetic nanoparticles containing Fe₃O₄ was higher than in the groups receiving magnetic nanoparticles containing Fe₃O₄ or gambogic acid, while expression of p-PI3K, p-Akt, p-Bad, pro-caspase 9, and pro-caspase 3 degraded.

Conclusion:

Magnetic nanoparticles containing Fe₃O₄ can enhance apoptosis induced by gambogic acid which may be closely related to regulation of the PI3K/Akt/Bad pathway in the treatment of human colon cancer.

Effects of gambogic acid on the activation of caspase-3 and downregulation of SIRT1 in RPMI-8226 multiple myeloma cells via the accumulation of ROS

Multiple myeloma (MM) is the second most commonly diagnosed hematologic malignancy. Although new drugs, including bortezomib and lenalidomide, have improved the treatment landscape for MM patients, MM remains incurable. Therefore, screening for novel anti-myeloma drugs is necessary. Gambogic acid (GA), the main active ingredient of gamboges secreted from the Garcinia hanburryi tree, has been reported to exhibit potent anticancer activity in certain solid tumors and hematological malignancies, while there are few studies that are available concerning its effects on MM cells. In the present study, we investigated the anticancer activity of GA on the MM RPMI-8226 cells and further studied the underlying mechanisms by which GA affected the cells. RPMI-8226 cells were cultured and the effect of GA on cell proliferation was analyzed using MTT assay. Hoechst 33258 staining was used to visualize nuclear fragmentation, and reactive oxygen species (ROS) levels were detected. GA was found to have a significant, dose-dependent effect on growth inhibition and apoptosis induction in RPMI-8226 cells. This activity is associated with the accumulation of ROS, which contributes to the activation of caspase-3 and the cleavage of poly (ADP-ribose) polymerase (PARP), accompanied with apoptosis in RPMI-8226 cells treated with GA. Mammalian SIRT1, as the closest homolog of the yeast Sir2, was extensively involved in regulating cell processes, including cell senescence, aging and neuronal protection, as well as having anti-apoptotic properties. Moreover, SIRT1 overexpression has been shown to protect cancer cells from chemotherapy and ionizing radiation. In the present study, we demonstrated that GA has the potential to downregulate the expression of SIRT1 via ROS accumulation. In conclusion, our study found that GA is able to induce apoptosis in RPMI-8226 cells via ROS accumulation followed by caspase-3 activation, PARP cleavage and SIRT1 downregulation. These results suggest that GA may have the potential to not only induce apoptosis in MM cells, but also to decrease the relapse rate of MM.

Poloxamer 407/TPGS mixed micelles for delivery of gambogic acid to breast and multidrug-resistant cancer

Background

Delivery of a high concentration of anticancer drugs specifically to cancer cells remains the biggest challenge for the treatment of multidrug-resistant cancer. Poloxamers and D-α-Tocopheryl polyethylene glycol 1000 succinate (TPGS) are known inhibitors of P-glycoprotein (P-gp). Mixed micelles prepared from Poloxamer 407 and TPGS may increase the therapeutic efficacy of the drug by delivering high concentrations inside the cells and inhibiting P-gp. Gambogic acid (GA) is a naturally derived novel anticancer agent, but poor solubility and toxic side effects limit its use. In this study, we have developed Poloxamer 407 and TPGS mixed micelle-encapsulating GA for the treatment of breast and multidrug-resistant cancer.

Methods

GA-loaded Poloxamer 407/TPGS mixed micelles were prepared using a thin film hydration method, and their physicochemical properties were characterized. Cellular accumulation and cytotoxicity of the GA-loaded Poloxamer 407/TPGS mixed micelles were studied in breast cancer cells, MCF-7 cells, and multidrug-resistant NCI/ADR-RES cells.

Results

The diameter of GA-loaded Poloxamer 407/TPGS mixed micelles was about 17.4 ± 0.5 nm and the zeta potential −13.57 mV. The entrapment efficiency of GA was 93.1% ± 0.5% and drug loading was about 9.38% ± 0.29%. Differential scanning calorimetry and X-ray powder diffraction studies confirmed that GA is encapsulated by the polymers. The in vitro release studies showed that mixed micelles sustained the release of GA for more than 4 days. Results from cellular uptake studies indicated that GA-loaded Poloxamer 407/TPGS mixed micelles had increased cellular uptake of GA in NCI/ADR-RES cells. Cytotoxicity of GA-loaded Poloxamer 407/TPGS mixed micelles was found to be 2.9 times higher in multidrug-resistant NCI/ADR-RES cells, and 1.6 times higher in MCF-7 cells, as compared with unencapsulated GA.

Conclusion

This study suggests that Poloxamer 407/TPGS mixed micelles can be used as a delivery system for GA to treat breast and multidrug-resistant cancer.

Synergistic antitumor efficiency of docetaxel and curcumin against lung cancer

Curcumin (Cum), the principal polyphenolic curcuminoid, obtained from the turmeric rhizome Curcuma longa, is recently reported to have potential antitumor effects in vitro and in vivo. Docetaxel (Doc) is considered as first-line chemotherapy for the treatment of non-small cell lung cancer. Here we report for the first time that Cum could synergistically enhance the in vitro and in vivo antitumor efficacy of Doc against lung cancer. In the current study, combination index (CI) is calculated in both in vitro and in vivo studies to determine the interaction between Cum and Doc. In the in vitro cytotoxicity test, media-effect analysis clearly indicated a synergistic interaction between Cum and Doc in certain concentrations. Moreover, in vivo evaluation further demonstrated the superior anticancer efficacy of Cum + Doc compared with Doc alone by intravenous delivery in an established A549 transplanted xenograft model. Results showed that Cum synergistically increased the efficacy of Doc immediately after 4 days of the initial treatment. Additionally, simultaneous administration of Cum and Doc showed little toxicity to normal tissues including bone marrow and liver at the therapeutic doses. Therefore, in vitro and in vivo evaluations demonstrated the satisfying synergistic antitumor efficacy of Cum and Doc against lung cancer and the introduction of Cum in traditional chemotherapy is a most promising way to counter the spread of non-small cell lung cancer.

Gambogenic acid inhibits proliferation of A549 cells through apoptosis inducing through up-regulation of the p38 MAPK cascade

Gamboge is a dry resin secreted from Garcinia hanburryi, and gambogenic acid (GNA) is one of the main active compounds of gamboge. We have previously demonstrated the anticancer activity of GNA in A549 cells and pointed out its potential effects in anticancer therapies. Previous studies reported that GNA induced apoptosis in many cancer cell lines and inhibited A549 tumor growth in xenograft of nude mice in vivo. However, the anticancer mechanism of GNA has still not been well studied. In this paper, we have investigated whether GNA-induced apoptosis is critically mediated by the p38 mitogen-activated protein kinase (MAPK) pathway. Our findings revealed that GNA could induce apoptosis, inhibit proliferation, down-regulate the expression of p38 and MAPK, increase the activations of caspase-9, caspase-3, and cytochrome c release. Furthermore, using SB203580, an adenosine triphosphate-competitive inhibitor of p38 MAPK, inhibit the expression of p-p38 and the experimental results show that it may promote the occurrence of apoptosis induced by GNA. Taken together, these results suggested that up-regulation of the p38 MAPK cascade may account for the activation of GNA-induced apoptosis.

Gambogic acid-induced degradation of mutant p53 is mediated by proteasome and related to CHIP

As an oncoprotein, mutant p53 is a potential tumor-specific target for cancer therapy. Most mutated forms of the protein are largely accumulated in cancer cells due to their increased stability. In the present study, we demonstrate that mutant p53 protein stability is regulated by gambogic acid (GA). Following GA exposure, protein levels of mutant p53 decreased while the mRNA levels were not affected in MDA-MB-435 cells, which indicate that GA down-regulates mutant p53 at post-transcription level. Co-treatment with GA and cycloheximide, a protein synthesis inhibitor, induced a decrease of half-life of mutant p53 protein. These findings indicated that the reduction of mutant p53 by GA was due to the destabilization and degradation of the protein. Furthermore, inhibition of proteasome activity by MG132 blocked GA-induced down-regulation of mutant p53, causing mutant p53 accumulation in detergent-insoluble cellular fractions. Further studies revealed that mutant p53 was ubiquitinated and it was chaperones related ubiquitin ligase carboxy terminus of Hsp70-interacting protein (CHIP) rather than MDM2 involved in the degradation of mutant p53. In addition, GA prevented Hsp90/mutant p53 complex formation and enhanced interaction of mutant p53 with Hsp70. Depletion of CHIP stabilized mutant p53 in GA treated cells. In conclusion, mutant p53 may be down-regulated by GA through chaperones-assisted ubiquitin/proteasome degradation pathway in cancer cells.

Gambogic acid inhibits STAT3 phosphorylation through activation of protein tyrosine phosphatase SHP-1: potential role in proliferation and apoptosis

The transcription factor, STAT3, is associated with proliferation, survival, and metastasis of cancer cells. We investigated whether gambogic acid (GA), a xanthone derived from the resin of traditional Chinese medicine, Garcinia hanburyi (mangosteen), can regulate the STAT3 pathway, leading to suppression of growth and sensitization of cancer cells. We found that GA induced apoptosis in human multiple myeloma cells that correlated with the inhibition of both constitutive and inducible STAT3 activation. STAT3 phosphorylation at both tyrosine residue 705 and serine residue 727 was inhibited by GA. STAT3 suppression was mediated through the inhibition of activation of the protein tyrosine kinases Janus-activated kinase 1 (JAK1) and JAK2. Treatment with the protein tyrosine phosphatase (PTP) inhibitor pervanadate reversed the GA-induced downregulation of STAT3, suggesting the involvement of a PTP. We also found that GA induced the expression of the PTP SHP-1. Deletion of the SHP-1 gene by siRNA suppressed the ability of GA to inhibit STAT3 activation and to induce apoptosis, suggesting the critical role of SHP-1 in its action. Moreover, GA downregulated the expression of STAT3-regulated antiapoptotic (Bcl-2, Bcl-xL, and Mcl-1), proliferative (cyclin D1), and angiogenic (VEGF) proteins, and this correlated with suppression of proliferation and induction of apoptosis. Overall, these results suggest that GA blocks STAT3 activation, leading to suppression of tumor cell proliferation and induction of apoptosis.

Regulation of survival, proliferation, invasion, angiogenesis, and metastasis of tumor cells through modulation of inflammatory pathways by nutraceuticals

Almost 25 centuries ago, Hippocrates, the father of medicine, proclaimed "Let food be thy medicine and medicine be thy food." Exploring the association between diet and health continues today. For example, we now know that as many as 35% of all cancers can be prevented by dietary changes. Carcinogenesis is a multistep process involving the transformation, survival, proliferation, invasion, angiogenesis, and metastasis of the tumor and may take up to 30 years. The pathways associated with this process have been linked to chronic inflammation, a major mediator of tumor progression. The human body consists of about 13 trillion cells, almost all of which are turned over within 100 days, indicating that 70,000 cells undergo apoptosis every minute. Thus, apoptosis/cell death is a normal physiological process, and it is rare that a lack of apoptosis kills the patient. Almost 90% of all deaths due to cancer are linked to metastasis of the tumor. How our diet can prevent cancer is the focus of this review. Specifically, we will discuss how nutraceuticals, such as allicin, apigenin, berberine, butein, caffeic acid, capsaicin, catechin gallate, celastrol, curcumin, epigallocatechin gallate, fisetin, flavopiridol, gambogic acid, genistein, plumbagin, quercetin, resveratrol, sanguinarine, silibinin, sulforaphane, taxol, gamma-tocotrienol, and zerumbone, derived from spices, legumes, fruits, nuts, and vegetables, can modulate inflammatory pathways and thus affect the survival, proliferation, invasion, angiogenesis, and metastasis of the tumor. Various cell signaling pathways that are modulated by these agents will also be discussed.