16-hydroxycleroda-3,13-dien-15,16-olide regulates the expression of histone-modifying enzymes PRC2 complex and induces apoptosis in CML K562 cells

The roles of EZH2 in cancer and its inhibitors

The enhancer of zeste homolog 2 (EZH2) is encoded by the Enhancer of zeste 2 polycomb repressive complex 2 subunit gene. EZH2 is involved in the cell cycle, DNA damage repair, cell differentiation, autophagy, apoptosis, and immunological modulation. The main function of EZH2 is to catalyze the methylation of H3 histone of H3K27Me3, which inhibits the transcription of target genes, such as tumor suppressor genes. EZH2 also forms complexes with transcriptions factors or directly binds to the promoters of target genes, leading to regulate gene transcriptions. EZH2 has been as a prominent target for cancer therapy and a growing number of potential targeting medicines have been developed. This review summarized the mechanisms that EZH2 regulates gene transcription and the interactions between EZH2 and important intracellular signaling molecules (Wnt, Notch, MEK, Akt) and as well the clinical applications of EZH2-targeted drugs.

Clerodane diterpene induces apoptosis/anoikis and suppresses migration and invasion of human bladder cancer cells through the histone deacetylases, integrin–focal adhesion kinase, and matrix metalloproteinase 9 signalling pathways

Clerodane diterpene, a class of bicyclic diterpenoids, is found in hundreds of plant species. 16-hydroxycleroda-3,13-dien-15,16-olide (CD) can be isolated from the plant Polyalthia longifolia and has been applied against oral cancer and glioma by xenograft model. In this study, we aim to explore its antitumour action by examining its histone deacetylase (HDAC) activity and integrin-associated intracellular signalling pathway on T24 human bladder cancer (BC) cells. Our results revealed that CD-inhibited colony formation, HDAC activity, HDAC (1, 2 and 3) mRNA and cell spreading on fibronectin-coated surfaces in a concentration-dependent manner. Furthermore, decreased cFLIP and increased caspase-8 cleavage accompanied CD-induced cell death. At non-toxic concentrations, CD blocked the migration and invasion of T24 cells. CD hindered migration and invasion by the downregulation of fibronectin, integrin α5 β1, β-catenin, FAK, vinculin and Rho A, as well as by reduction of phosphorylated glycogen synthase kinase 3 β (pGSK3 β), pSrc, pstat3 and pNF κB. We observed that the MMP9 gene was closely linked with prognosis of patients with bladder cancer. MMP9 protein levels and activity were largely attenuated by CD in a concentration-dependent manner. In conclusion, CD-induced caspase-8-dependent apoptosis and suppressed migration and invasion by blocking several intracellular signalling pathways, including downregulation of HDAC activity and integrin–FAK and MMP9 pathways.

Clerodane Diterpenoids from an Edible Plant Justicia insularis: Discovery, Cytotoxicity, and Apoptosis Induction in Human Ovarian Cancer Cells

OBJECTIVES

The toxicity of chemotherapeutic anticancer drugs is a serious issue in clinics. Drug discovery from edible and medicinal plants represents a promising approach towards finding safer anticancer therapeutics. Justicia insularis T. Anderson (Acanthaceae) is an edible and medicinal plant in Nigeria. This study aims to discover cytotoxic compounds from this rarely explored J. insularis and investigate their underlying mechanism of action.

METHODS

The cytotoxicity of the plant extract was evaluated in human ovarian cancer cell lines and normal human ovarian surface epithelia (HOE) cells using a sulforhodamine B assay. Bioassay-guided isolation was carried out using column chromatography including HPLC, and the isolated natural products were characterized using GC-MS, LC-HRMS, and 1D/2D NMR techniques. Induction of apoptosis was evaluated using Caspase 3/7, 8, and 9, and Annexin V and PI based flow cytometry assays. SwissADME and SwissTargetPrediction web tools were used to predict the molecular properties and possible protein targets of identified active compounds. Key finding: The two cytotoxic compounds were identified as clerodane diterpenoids: 16(α/β)-hydroxy-cleroda-3,13(14)Z-dien-15,16-olide (1) and 16-oxo-cleroda-3,13(14)E-dien-15-oic acid (2) from the Acanthaceous plant for the first time. Compound 1 was a very abundant compound (0.7% per dry weight of plant material) and was shown to be more potent than compound 2 with IC₅₀ values in the micromolar range against OVCAR-4 and OVCAR-8 cancer cells. Compounds 1 and 2 were less cytotoxic to HOE cell line. Both compounds induced apoptosis by increasing caspase 3/7 activities in a concentration dependent manner. Compound 1 further increased caspase 8 and 9 activities and apoptosis cell populations. Compounds 1 and 2 are both drug like, and compound 1 may target various proteins including a kinase.

CONCLUSIONS

Clerodane diterpenoids (1 and 2) in J. insularis were identified as cytotoxic to ovarian cancer cells via the induction of apoptosis, providing an abundant and valuable source of hit compounds for the treatment of ovarian cancer.

Phytochemicals from Polyalthia Species: Potential and Implication on Anti-Oxidant, Anti-Inflammatory, Anti-Cancer, and Chemoprevention Activities

Polyalthia belong to the Annonaceae family and are a type of evergreen tree distributed across many tropical and subtropical regions. Polyalthia species have been used long term as indigenous medicine to treat certain diseases, including fever, diabetes, infection, digestive disease, etc. Recent studies have demonstrated that not only crude extracts but also the isolated pure compounds exhibit various pharmacological activities, such as anti-oxidant, anti-microbial, anti-tumor, anti-cancer, etc. It is known that the initiation of cancer usually takes several years and is related to unhealthy lifestyle, as well as dietary and environmental factors, such as stress, toxins and smoking. In fact, natural or synthetic substances have been used as cancer chemoprevention to delay, impede, or even stop cancer growing. This review is an attempt to collect current available phytochemicals from Polyalthia species, which exhibit anti-cancer potentials for chemoprevention purposes, providing directions for further research on the interesting agents and possible clinical applications.

Clerodane Diterpene Ameliorates Inflammatory Bowel Disease and Potentiates Cell Apoptosis of Colorectal Cancer

Inflammatory bowel disease (IBD) is general term for ulcerative colitis and Crohn's disease, which is chronic intestinal and colorectal inflammation caused by microbial infiltration or immunocyte attack. IBD is not curable, and is highly susceptible to develop into colorectal cancer. Finding agents to alleviate these symptoms, as well as any progression of IBD, is a critical effort. This study evaluates the anti-inflammation and anti-tumor activity of 16-hydroxycleroda-3,13-dien-15,16-olide (HCD) in in vivo and in vitro assays. The result of an IBD mouse model induced using intraperitoneal chemical azoxymethane (AOM)/dextran sodium sulfate (DSS) injection showed that intraperitoneal HCD adminstration could ameliorate the inflammatory symptoms of IBD mice. In the in vitro assay, cytotoxic characteristics and retained signaling pathways of HCD treatment were analyzed by MTT assay, cell cycle analysis, and Western blotting. From cell viability determination, the IC₅₀ of HCD in Caco-2 was significantly lower in 2.30 μM at 48 h when compared to 5-fluorouracil (5-FU) (66.79 μM). By cell cycle and Western blotting analysis, the cell death characteristics of HCD treatment in Caco-2 exhibited the involvement of extrinsic and intrinsic pathways in cell death, for which intrinsic apoptosis was predominantly activated via the reduction in growth factor signaling. These potential treatments against colon cancer demonstrate that HCD could provide a promising adjuvant as an alternative medicine in combating colorectal cancer and IBD.

Polyalthia Clerodane Diterpene Potentiates Hypoglycemia via Inhibition of Dipeptidyl Peptidase 4

Serine protease dipeptidyl peptidase 4 (DPP-4) is involved in self/non-self-recognition and insulin sensitivity. DPP-4 inhibitors are conventional choices for diabetic treatment; however, side effects such as headache, bronchus infection, and nasopharyngitis might affect the daily lives of diabetic patients. Notably, natural compounds are believed to have a similar efficacy with lower adverse effects. This study aimed to validate the DPP-4 inhibitory activity of clerodane diterpene 16-hydroxycleroda-3,13-dien-15,16-olide (HCD) from Polyalthia longifolia, rutin, quercetin, and berberine, previously selected through molecular docking. The inhibitory potency of natural DPP-4 candidates was further determined by enzymatic, in vitro Caco-2, and ERK/PKA activation in myocyte and pancreatic cells. The hypoglycemic efficacy of the natural compounds was consecutively analyzed by single-dose and multiple-dose administration in diet-induced obese diabetic mice. All the natural-compounds could directly inhibit DPP-4 activity in enzymatic assay and Caco-2 inhibition assay, and HCD showed the highest inhibition of the compounds. HCD down-regulated LPS-induced ERK phosphorylation in myocyte but blocked GLP-1 induced PKA expression. For in vivo tests, HCD showed hypoglycemic efficacy only in single-dose administration. After 28-days administration, HCD exhibited hypolipidemic and hepatoprotective efficacy. These results revealed that HCD performed potential antidiabetic activity via inhibition of single-dose and long-term administrations, and could be a new prospective anti-diabetic drug candidate.

16-Hydroxycleroda-3,13-dien-15,16-olide and N-Methyl-Actinodaphine Potentiate Tamoxifen-Induced Cell Death in Breast Cancer

In this study, we investigated whether 16-hydroxycleroda-3,13-dien-15,16-olide (HCD) and N-methyl-actinodaphine (MA) could sensitize breast cancer cells to Tamoxifen (TMX) treatment. MA or HCD alone or in combination with TMX dose-dependently inhibited MCF-7 and MDA-MB-231 cell growth, with a more potent inhibition on MDA-MB 231 cells. Furthermore, this novel combination significantly induced S and G2/M cell cycle phase in MDA-MB 231 than MCF-7 cells. Further determination of the apoptotic induction showed that MA or HCD and TMX combination inhibited MDA-MB-231 and MCF-7 cancer cells by upregulating Bax and by downregulating Bcl-2 mRNA and protein expression without altering Caspase-8 and Caspase-12 expression. These results suggest that MA or HCD pretreatment may potentiate the anti-tumor effect of tamoxifen on breast cancer.

Epigenetic regulation of cancer biology and anti-tumor immunity by EZH2

Polycomb group proteins regulate chromatin structure and have an important regulatory role on gene expression in various cell types. Two polycomb group complexes (Polycomb repressive complex 1 (PRC1) and 2 (PRC2)) have been identified in mammalian cells. Both PRC1 and PRC2 compact chromatin, and also catalyze histone modifications. PRC1 mediates monoubiquitination of histone H2A, whereas PRC2 catalyzes methylation of histone H3 on lysine 27. These alterations of histones can lead to altered gene expression patterns by regulating chromatin structure. Numerous studies have highlighted the role of the PRC2 catalytic component enhancer of zeste homolog 2 (EZH2) in neoplastic development and progression, and EZH2 mutations have been identified in various malignancies. Through modulating the expression of critical genes, EZH2 is actively involved in fundamental cellular processes such as cell cycle progression, cell proliferation, differentiation and apoptosis. In addition to cancer cells, EZH2 also has a decisive role in the differentiation and function of T effector and T regulatory cells. In this review we summarize the recent progress regarding the role of EZH2 in human malignancies, highlight the molecular mechanisms by which EZH2 aberrations promote the pathogenesis of cancer, and discuss the anti-tumor effects of EZH2 targeting via activating direct anti-cancer mechanisms and anti-tumor immunity.

16-Hydroxycleroda-3, 13-dien-15, 16-olide inhibits the proliferation and induces mitochondrial-dependent apoptosis through Akt, mTOR, and MEK-ERK pathways in human renal carcinoma cells

BACKGROUND

Renal cell carcinoma (RCC) is well known that it cannot be treated with traditional chemotherapy or radiotherapy. 16-Hydroxycleroda-3,13-dien-15,16-olide (CD), isolated from Polyalthia longifolia Benth. & Hook. f. var. pendula had been reported to display significant efficacy against cancer cell lines.

PURPOSE

To determine the anti-tumour activities of CD in two clear cell type RCC (ccRCC) cell lines (A-498 and 786-O). In addition, the underlying mechanisms were also examined.

METHODS

The cell viabilities of CD-treated ccRCC cells were examined by MTT assay. The apoptotic features were confirmed by acridine orange and ethidium bromide staining. 2',7'-dichlorofluorescin diacetate was used to check reactive oxygen species (ROS) involvement. Mitochondria membrane potential (MMP) were determined by using fluorescent dyes, rhodamine 123 and 5',6,6'-tetrachloro-1,1',3,3'-tetraethyl benzimidazolylcarbocyanine iodide (JC-1). Proapoptotic, anti-apoptotic proteins and intracellular signaling molecules involved in CD-induced apoptosis were examined by Western blot analysis.

RESULTS

CD inhibited both 786-O and A-498 cell proliferation and induced a series apoptotic characteristics expressions, ROS accumulation, caspase-3 activation as well as poly-(ADP-ribose) polymerase cleavage in both ccRCC cells. Additionally, CD caused MMP reduction and cytochrome c release from mitochondria as well as inhibition of anti-apoptotic proteins, including B cell lymphoma 2 and heat shock protein 70. Mechanically, we address that CD suppressed cell proliferation and induced apoptosis via induction of FOXO3a as well as decreased phosphorylation of Akt, mTOR, MEK/ERK and their downstream molecules, cMyc and hypoxia inducible factor 2α expression in a concentration- and time-dependent trend.

CONCLUSION

CD caused cell death through ROS overproduction and induction of mitochondria-dependent apoptotic pathway in ccRCC cells that accompanied with multiple oncogenic signals inactivation.

Epigenetic dysregulation in chronic myeloid leukaemia: A myriad of mechanisms and therapeutic options

The onset of global epigenetic changes in chromatin that drive tumor proliferation and heterogeneity is a hallmark of many forms of cancer. Identifying the epigenetic mechanisms that govern these changes and developing therapeutic approaches to modulate them, is a well-established avenue pursued in translational cancer medicine. Chronic myeloid leukemia (CML) arises clonally when a hematopoietic stem cell (HSC) acquires the capacity to produce the constitutively active tyrosine kinase BCR-ABL1 fusion protein which drives tumor development. Treatment with tyrosine kinase inhibitors (TKI) that target BCR-ABL1 has been transformative in CML management but it does not lead to cure in the vast majority of patients. Thus novel therapeutic approaches are required and these must target changes to biological pathways that are aberrant in CML - including those that occur when epigenetic mechanisms are altered. These changes may be due to alterations in DNA or histones, their biochemical modifications and requisite 'writer' proteins, or to dysregulation of various types of non-coding RNAs that collectively function as modulators of transcriptional control and DNA integrity. Here, we review the evidence for subverted epigenetic mechanisms in CML and how these impact on a diverse set of biological pathways, on disease progression, prognosis and drug resistance. We will also discuss recent progress towards developing epigenetic therapies that show promise to improve CML patient care and may lead to improved cure rates.

The autophagic inhibition oral squamous cell carcinoma cancer growth of 16-hydroxy-cleroda-3,14-dine-15,16-olide

16-hydroxycleroda-3, 13-dine-15, 16-olide (HCD) isolated from Polyalthia longifolia possesses numerous biological activities. Previous studies have reported that HCD can block phosphorylation activity of cancer cells to inhibit tumor cell growth, but the anti-tumor activity in oral squamous cell carcinoma is unrevealed. This study investigates the inhibiting effect of HCD on human OSCC cell growth; thereby, developing a new oral cancer drug. In in vitro cultured human OSCC cells (OECM1 and SAS) were employed to test the inhibitory growth of HCD via cell cytotoxic effect using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay, Western blotting, and further determining of the inhibitory efficacy of tumor growth by a xenograft tumor on BALB/c male nude mice (in vivo test). Under various concentrations of HCD and time course treatments were shown to effectively cause cell death and cell-cycle arrest in OECM1 and SAS cells, which was confirmed via a clinical drug (cisplatin) as a positive control. In addition, HCD induced the autophagic cell death in OECM1 and SAS cells by LC3-mediated LC3-I/LC3-II/p62 pathway at the in vitro level. An in vivo assay indicated that HCD could treat oral cancer by deferring tumor growth. These findings provide a favorable assessment for further elucidating the role of HCD that targets autophagic cell death pathways as a potential agent for cancer therapy.

Natural Compounds from Herbs that can Potentially Execute as Autophagy Inducers for Cancer Therapy

Accumulated evidence indicates that autophagy is a response of cancer cells to various anti-cancer therapies. Autophagy is designated as programmed cell death type II, and is characterized by the formation of autophagic vacuoles in the cytoplasm. Numerous herbs, including Chinese herbs, have been applied to cancer treatments as complementary and alternative medicines, supplements, or nutraceuticals to dampen the side or adverse effects of chemotherapy drugs. Moreover, the tumor suppressive actions of herbs and natural products induced autophagy that may lead to cell senescence, increase apoptosis-independent cell death or complement apoptotic processes. Hereby, the underlying mechanisms of natural autophagy inducers are cautiously reviewed in this article. Additionally, three natural compounds—curcumin, 16-hydroxycleroda-3,13-dien-15,16-olide, and prodigiosin—are presented as candidates for autophagy inducers that can trigger cell death in a supplement or alternative medicine for cancer therapy. Despite recent advancements in therapeutic drugs or agents of natural products in several cancers, it warrants further investigation in preclinical and clinical studies.

Encapsulation of 16-Hydroxycleroda-3,13-Dine-16,15-Olide in Mesoporous Silica Nanoparticles as a Natural Dipeptidyl Peptidase-4 Inhibitor Potentiated Hypoglycemia in Diabetic Mice

Natural supplements comprise good efficacy with less adverse effects as against diabetic therapy, but their advancement as anti-diabetic agents is unsatisfactory with regard to the delivery system. Dipeptidyl peptidase-4 (DPP4)/CD26) can degrade glucagon-like pepetide-1 (GLP-1) which renders a decrease of blood glucose levels. 16-hydroxycleroda-3,13-dine-16,15-olide (HCD) extracted from Polyalthia longifolia, exhibits numerous medicinal potentials including hypoglycemic potential. On consideration of HCD application, the bioavailability is affected by low solubility. Extended experiments of anti-diabetic efficacy confirmed HCD biocompatible with mesoporous silica nanoparticles (MSNs) encapsulation resulted in a sustained release property in delivering HCD for the inhibition of DPP4 via the activity and protein levels of DPP4 analysis. In the enzymatic activity assay, MSN-HCD directly changed DPP4 activity. Moreover, MSN-HCD nanoparticles were treated with Caco-2 cells and the protein levels of DPP4 determined within the cells. The results revealed that MSN-HCD caused reduction of DPP4 activity in a time- and dose-dependent fashion. Orally administered MSN-HCD in diet-induced diabetic mice alleviated blood glucose via an oral glucose tolerance test. In addition, administration of MSN-HCD for five weeks revealed that the biochemical cues such as pyruvate transaminase (GPT), glutamate oxaloacetate transaminase (GOT), triglycerides (TG), cholesterol (CHO), and glycated hemoglobin (HbA1c) in mice were commendable as further confirmation of MSN-HCD efficacy and less adverse effects in down-regulation of hyperglycemia. Furthermore, this formulation effectively controlled blood glucose and significantly decreased the body weight of mice, suggesting that MSN-HCD exerts natural DPP4 inhibitor as a potential clinical drug for the treatment of diabetes.

16-hydroxy-cleroda-3,13-dien-16,15-olide induced glioma cell autophagy via ROS generation and activation of p38 MAPK and ERK-1/2

16-hydroxy-cleroda-3,13-dien-16,15-olide (HCD), a natural product isolated from medicinal plant Polyalthia longifolia exhibits anticancer activity through caspase-independent apoptosis in brain tumors, as previously reported. This study further attempted to investigate the involvement of HCD-induced autophagy in brain tumor cell lines neuroblastoma N18 and glioma C6 through the induction of reactive oxygen species (ROS) and the activation of p38 and ERK-1/2 pathway. The results demonstrated that HCD increased the hyper-generation of ROS and decreased cellular antioxidant enzymes, such as superoxide dismutase (SOD), glutathione (GSH), glutathione peroxidase (GPx), and glutathione s transferase (GST). Furthermore, HCD increased the expressions of autophagic marker proteins LC3-II and Beclin-1 in a time- and dose-dependent manner. Additionally, HCD was found to significantly induce p-p38 MAPK and p-ERK-1/2 proteins by Western blot, which implies that HCD is a potential therapeutic anticancer agent that exerts its activity through inducing ROS-mediation for the autophagy of brain tumor cells.

Wedelolactone disrupts the interaction of EZH2-EED complex and inhibits PRC2-dependent cancer

Polycomb repressive complex 2 (PRC2), which is responsible for the trimethylation of H3K27 (H3K27me3), plays a part in tumorigenesis, development and/or maintenance of adult tissue specificity. The pivotal role of PRC2 in cancer makes it a therapeutic target for epigenetic cancer therapy. However, natural compounds targeting the enhancer of zeste homolog 2 (EZH2) - embryonic ectoderm development (EED) interaction to disable PRC2 complex are scarcely reported. Here, we reported the screening and identification of natural compounds which could disrupt the EZH2-EED interaction. One of these compounds, wedelolactone, binds to EED with a high affinity (KD = 2.82 μM), blocks the EZH2-EED interaction in vitro, induces the degradation of PRC2 core components and modulates the expression of detected PRC2 downstream targets and cancer-related genes. Furthermore, some PRC2-dependent cancer cells undergone growth arrest upon treatment with wedelolactone. Thus, wedelolactone and its derivatives which target the EZH2-EED interaction could be candidates for the treatment of PRC2-dependent cancer.

Targeting Enhancer of Zeste Homolog 2 as a promising strategy for cancer treatment

Polycomb group proteins represent a global silencing system involved in development regulation. In specific, they regulate the transition from proliferation to differentiation, contributing to stem-cell maintenance and inhibiting an inappropriate activation of differentiation programs. Enhancer of Zeste Homolog 2 (EZH2) is the catalytic subunit of Polycomb repressive complex 2, which induces transcriptional inhibition through the tri-methylation of histone H3, an epigenetic change associated with gene silencing. EZH2 expression is high in precursor cells while its level decreases in differentiated cells. EZH2 is upregulated in various cancers with high levels associated with metastatic cancer and poor prognosis. Indeed, aberrant expression of EZH2 causes the inhibition of several tumor suppressors and differentiation genes, resulting in an uncontrolled proliferation and tumor formation. This editorial explores the role of Polycomb repressive complex 2 in cancer, focusing in particular on EZH2. The canonical function of EZH2 in gene silencing, the non-canonical activities as the methylation of other proteins and the role in gene transcriptional activation, were summarized. Moreover, mutations of EZH2, responsible for an increased methyltransferase activity in cancer, were recapitulated. Finally, various drugs able to inhibit EZH2 with different mechanism were described, specifically underscoring the effects in several cancers, in order to clarify the role of EZH2 and understand if EZH2 blockade could be a new strategy for developing specific therapies or a way to increase sensitivity of cancer cells to standard therapies.

Electrical stimulation of adipose-derived mesenchymal stem cells in conductive scaffolds and the roles of voltage-gated ion channels

Since electrical stimulation (ES) can significantly accelerate bone healing, a conductive scaffold that can deliver ES locally at the defect site is desirable for bone defect therapy. Herein, an electrically conductive scaffold was prepared via incorporation of polypyrrole (PPY) in a polycaprolactone (PCL) template scaffold. In vitro tests with mouse osteoblasts indicate that the PPY/PCL scaffold has good biocompatibility, and is suitable for use as an ES substrate. When human adipose-derived mesenchymal stem cells (AD-MSCs) were cultured in the PPY/PCL scaffold and subjected to 200 μA of direct current for 4h per day for 21 days, the amount of calcium deposited was 100% higher than that without ES. When these cells were subjected to ES together with blockers of voltage-gated calcium (Ca(2+)v), sodium (Na(+)v), potassium (K(+)v), or chloride (Cl(-)v) channels, the ES-induced enhancement of AD-MSCs' functions was reduced with Na(+)v, K(+)v, or Cl(-)v blockers and completely nullified with Ca(2+)v blocker. These results indicate that ion fluxes through these channels activated by ES induce different cascades of reactions in the cells, which subsequently regulate AD-MSCs' functions, and Ca(2+)v plays a more critical role than the other three channels. Our results further the current understanding of the mechanisms by which ES regulates stem cells' behavior, and also showed that the conductive PPY/PCL scaffold with application of ES has good potential in bone defect therapy.

STATEMENT OF SIGNIFICANCE

In this work, an electrically conductive and biocompatible scaffold was prepared by incorporating polypyrrole in a polycaprolactone template scaffold. Application of 200 μA direct current for 4h per day to human adipose derived-mesenchymal stem cells cultured on this scaffold promoted migration of these cells into the inner region of the scaffold and enhanced their osteogenic differentiation. The roles of voltage-gated ion channels (Ca(2+)v, Na(+)v, K(+)v and Cl(-)v) in osteogenic differentiation stimulated by the electric current were investigated. The results from these experiments further the current understanding of the mechanisms by which electrical stimulation regulates stem cells' behavior, and also show that the polypyrrole-polycaprolactone scaffold with application of electrical stimulation has good potential in bone defect therapy.

A focal adhesion kinase inhibitor 16-hydroxy-cleroda-3,13-dien-16,15-olide incorporated into enteric-coated nanoparticles for controlled anti-glioma drug delivery

16-Hydroxy-cleroda-3,13-dien-16,15-olide (HCD) which is extracted from a medicinal plant, Polyalthia longifolia, was shown to exhibit anticancer activity through apoptosis and FAK inhibition in our previous study. To improve its solubility and efficacy, a novel HCD delivery system using copper-substituted mesoporous silica nanoparticles (MSNs) was designed as a delivery vehicle, and the outer surfaces of MSNs were further coated with enteric polymers to prevent the drug from leaching in the stomach acid. All the data regarding synthesis and physical characterization, including Zeta potential, FT-IR spectra, N2 adsorption-desorption isotherms (BET), drug loading, powder X-ray diffraction, Thermo gravimetric analysis (TGA), Transmission electron microscopy (TEM), and Scanning electron microscopy (SEM) were well characterized. The non-coated MSN-HCD exposed to acidic pH (1.2) showed a rapid degradation of the drug, whereas the enteric-coated samples presented a sustained release profile in the gastrointestinal pHs. Cell cytotoxicity was further confirmed by the MTT-C6 Glioma cell line, in vitro. When compared with the control and pure HCD, the MSN-HCD revealed a potential anti-proliferation effect via the synergistic effect of the drug and the MSN vehicle. Additionally, this MSN-HCD had the effect of increasing the reactive oxygen species (ROS) levels and altered the Mitochondria membrane potential (MMP) in C6 cell line. The in vivo anti-tumor efficacy of enteric-coated MSN-HCD was evaluated by C6 Glioma bearing xenograft nude mice, and enteric-coated MSN-HCD clearly exhibited the greatest anti-glioma activity, as compared to the pure HCD and the untreated control. In terms of the effective treatment of brain glioma, this study provides conclusive evidence of the successful development of the anti-cancer agent HCD conjugated with enteric-coated MSN as a delivery control mechanism with enhanced dissolution characteristics.

Spiroquinazolinone-induced cytotoxicity and apoptosis in K562 human leukemia cells: alteration in expression levels of Bcl-2 and Bax

Spiroquinazolinone compounds have been considered as a new series of potent apoptosis-inducing agents. In this study, anti-proliferative and apoptotic effects of the derivatives from the spiroquinazolinone family were investigated in the human chronic myeloid leukemia K562 cells. The K562 cells were treated with various concentrations of the spiroquinazolinone (10-300 µM) for 3 days and cell viability was determined by MTT growth inhibition assay. 4t-QTC was more active among these compounds with IC50 of 50 ± 3.6 µM and was selected for further studies. Apoptosis, as the mechanism of cell death was investigated morphologically by acridine orange/ethidium bromide (AO/EtBr) double staining, cell surface expression assay of phosphatidyl serine by Annexin V/PI technique, as well as the formation of DNA ladder. The K562 cells underwent apoptosis upon a single dose (at IC50 value) of the 4t-QTC compound, and over-expressed caspase-3 expression by more than 1.7-fold, following a 72 hr treatment. Furthermore, RT-PCR and Western blot analysis revealed that treatment of the K562 cells with 4t-QTC down-regulates and up-regulates the expression of Bcl-2 (anti-apoptotic) and Bax (pro-apoptotic), respectively. Based on the present data, it seems that these compounds from the spiroquinazolinone family are good candidates for further evaluation as an effective chemotherapeutic family acting through induction of apoptosis in chronic myeloid leukemia.

A derivative of epigallocatechin-3-gallate induces apoptosis via SHP-1-mediated suppression of BCR-ABL and STAT3 signalling in chronic myelogenous leukaemia

BACKGROUND AND PURPOSE

Epigallocatechin-3-gallate (EGCG) is a component of green tea known to have chemo-preventative effects on several cancers. However, EGCG has limited clinical application, which necessitates the development of a more effective EGCG prodrug as an anticancer agent.

EXPERIMENTAL APPROACH

Derivatives of EGCG were evaluated for their stability and anti-tumour activity in human chronic myeloid leukaemia (CML) K562 and KBM5 cells.

KEY RESULTS

EGCG-mono-palmitate (EGCG-MP) showed most prolonged stability compared with other EGCG derivatives. EGCG-MP exerted greater cytotoxicity and apoptosis in K562 and KBM5 cells than the other EGCG derivatives. EGCG-MP induced Src-homology 2 domain-containing tyrosine phosphatase 1 (SHP-1) leading decreased oncogenic protein BCR-ABL and STAT3 phosphorylation in CML cells, compared with treatment with EGCG. Furthermore, EGCG-MP reduced phosphorylation of STAT3 and survival genes in K562 cells, compared with EGCG. Conversely, depletion of SHP-1 or application of the tyrosine phosphatase inhibitor pervanadate blocked the ability of EGCG-MP to suppress phosphorylation of BCR-ABL and STAT3, and the expression of survival genes downstream of STAT3. In addition, EGCG-MP treatment more effectively suppressed tumour growth in BALB/c athymic nude mice compared with untreated controls or EGCG treatment. Immunohistochemistry revealed increased caspase 3 and SHP-1 activity and decreased phosphorylation of BCR-ABL in the EGCG-MP-treated group relative to that in the EGCG-treated group.

CONCLUSIONS AND IMPLICATIONS

EGCG-MP induced SHP-1-mediated inhibition of BCR-ABL and STAT3 signalling in vitro and in vivo more effectively than EGCG. This derivative may be a potent chemotherapeutic agent for CML treatment.

Roles of enhancer of zeste homolog 2: from skeletal muscle differentiation to rhabdomyosarcoma carcinogenesis

Polycomb group proteins represent a global silencing system involved in embryonic development and stem-cell maintenance that regulates the transition from proliferation to differentiation during organogenesis. Two main complexes have been discovered: the polycomb repressive complex (PRC) 1 and 2, able to induce gene silencing by a synergistic mechanism or independently by each other. Enhancer of zeste homolog 2 (EZH2), the catalytic subunit of PRC2, represses gene transcription through the tri-methylation of histone H3 lysine 27. EZH2 deregulation is frequently associated with tumorigenesis, metastatic character, and poor prognosis in various cancer types. This review explores the role of EZH2 in normal development and in carcinogenesis. We reviewed the polycomb-mediated silencing mechanisms, the regulation of EZH2 activity and its recruitment to target genes. We also analyzed the role of EZH2 in normal muscle differentiation and in rhabdomyosarcoma, considering EZH2 blockade as a new strategy for developing specific therapies.

EZH2, an epigenetic driver of prostate cancer

The histone methyltransferase EZH2 has been in the limelight of the field of cancer epigenetics for a decade now since it was first discovered to exhibit an elevated expression in metastatic prostate cancer. It persists to attract much scientific attention due to its important role in the process of cancer development and its potential of being an effective therapeutic target. Thus here we review the dysregulation of EZH2 in prostate cancer, its function, upstream regulators, downstream effectors, and current status of EZH2-targeting approaches. This review therefore provides a comprehensive overview of EZH2 in the context of prostate cancer.

ERK inhibition enhances TSA-induced gastric cancer cell apoptosis via NF-κB-dependent and Notch-independent mechanism

AIMS

To analyze the combined impact of the histone deacetylase inhibitor (HDACI) Trichostatin A (TSA) and the extracellular-signal-regulated kinase 1/2 (ERK1/2) inhibitor PD98059 on gastric cancer (GC) cell line SGC7901 growth.

MAIN METHODS

SGC7901 cells were treated with TSA, PD98059 or with a TSA-PD98059 combination. Effects of drug treatment on tumor cell proliferation, apoptosis, cell cycle progression, and cell signaling pathways were investigated by MTS assay, flow cytometry, Western blotting, chromatin immunoprecipitation (ChIP) assay, electrophoretic mobility shift assay (EMSA), and luciferase reporter assay, respectively.

KEY FINDINGS

PD98059 enhanced TSA-induced cell growth arrest, apoptosis and activation of p21(WAF1/CIP1), but reversed TSA-induced activation of ERK1/2 and nuclear factor-κB (NF-κB). TSA alone up-regulated Notch1 and Hes1, and down-regulated Notch2, but PD98059 did not affect the trends of Notch1 and Notch2 induced by TSA. Particularly, PD98059 did potentiate the ability of TSA to down-regulate phospho-histone H3 protein, but increased levels of the acetylated forms of histone H3 bound to the p21(WAF1/CIP1) promoter, leading to enhanced expression of p21(WAF1/CIP1) in SGC7901 cells.

SIGNIFICANCE

PD98059 synergistically potentiates TSA-induced GC growth arrest and apoptosis by manipulating NF-κB and p21(WAF1/CIP1) independent of Notch. Therefore, concomitant administration of HDACIs and ERK1/2 inhibitors may be a promising treatment strategy for individuals with GC.