DAPK1 mediates the G1 phase arrest in human nasopharyngeal carcinoma cells induced by grifolin, a potential antitumor natural product

Anticancer potential of grifolin in lung cancer treatment through PI3K/AKT pathway inhibition

Objective

Grifolin is a natural secondary metabolite isolated from edible fruiting bodies of the mushroom Albatrellus confluens. Grifolin has antitumor activities in several types of cancer. We aimed to determine the effects of grifolin on lung cancer.

Methods

We determined the proliferation, migration, invasion, and apoptosis of lung cancer cells using 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, Ethynyl deoxyuridine, colony formation, wound scratch, transwell, flow cytometry, and xenograft mouse assays. Molecular docking evaluated the binding relation between grifolin and phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA). The levels of PIK3CA, AKT, and p-AKT were measured by western blot.

Results

Grifolin (10, 20, or 40 μM) inhibited the proliferation, migration, and invasion of lung cancer cells, and induced cell cycle arrest and apoptosis. Grifolin also decreased CDK4, CDK6, and CyclinD1 expression and significantly decreased PIK3CA and p-AKT expression in lung cancer cells. These anticancer effects were abolished by 740Y-P.

Conclusions

Grifolin regulates the PI3K/AKT pathway, thus inhibiting lung cancer progression.

The efficacy of natural products for the treatment of nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a malignant tumor originating in the nasopharyngeal epithelium with a high incidence in southern China and parts of Southeast Asia. The current treatment methods are mainly radiotherapy and chemotherapy. However, they often have side effects and are not suitable for long-term exposure. Natural products have received more and more attention in cancer prevention and treatment because of their its high efficiency, low toxic side effects, and low toxicity. Natural products can serve as a viable alternative, and this study aimed to review the efficacy and mechanisms of natural products in the treatment of NPC by examining previous literature. Most natural products act by inhibiting cell proliferation, metastasis, inducing cell cycle arrest, and apoptosis. Although further research is needed to verify their effectiveness and safety, natural products can significantly improve the treatment of NPC.

The Role of Death-Associated Protein Kinase-1 in Cell Homeostasis-Related Processes

Tremendous amount of financial resources and manpower have been invested to understand the function of numerous genes that are deregulated during the carcinogenesis process, which can be targeted for anticancer therapeutic interventions. Death-associated protein kinase 1 (DAPK-1) is one of the genes that have shown potential as biomarkers for cancer treatment. It is a member of the kinase family, which also includes Death-associated protein kinase 2 (DAPK-2), Death-associated protein kinase 3 (DAPK-3), Death-associated protein kinase-related apoptosis-inducing kinase 1 (DRAK-1) and Death-associated protein kinase-related apoptosis-inducing kinase 2 (DRAK-2). DAPK-1 is a tumour-suppressor gene that is hypermethylated in most human cancers. Additionally, DAPK-1 regulates a number of cellular processes, including apoptosis, autophagy and the cell cycle. The molecular basis by which DAPK-1 induces these cell homeostasis-related processes for cancer prevention is less understood; hence, they need to be investigated. The purpose of this review is to discuss the current understanding of the mechanisms of DAPK-1 in cell homeostasis-related processes, especially apoptosis, autophagy and the cell cycle. It also explores how the expression of DAPK-1 affects carcinogenesis. Since deregulation of DAPK-1 is implicated in the pathogenesis of cancer, altering DAPK-1 expression or activity may be a promising therapeutic strategy against cancer.

Insights into intricacies of the Latent Membrane Protein-1 (LMP-1) in EBV-associated cancers

Numerous lymphomas, carcinomas, and other disorders have been associated with Epstein-Barr Virus (EBV) infection. EBV's carcinogenic potential can be correlated to latent membrane protein 1 (LMP1), which is essential for fibroblast and primary lymphocyte transformation. LMP1, a transmembrane protein with constitutive activity, belongs to the tumour necrosis factor receptor (TNFR) superfamily. LMP1 performs number of role in the life cycle of EBV and the pathogenesis by interfering with, reprogramming, and influencing a vast range of host cellular activities and functions that are getting well-known but still poorly understood. LMP1, pleiotropically perturbs, reprograms and balances a wide range of various processes of cell such as extracellular vesicles, epigenetics, ubiquitin machinery, metabolism, cell proliferation and survival, and also promotes oncogenic transformation, angiogenesis, anchorage-independent cell growth, metastasis and invasion, tumour microenvironment. By the help of various experiments, it is proven that EBV-encoded LMP1 activates multiple cell signalling pathways which affect antigen presentation, cell-cell interactions, chemokine and cytokine production. Therefore, it is assumed that LMP1 may perform majorly in EBV associated malignancies. For the development of novel techniques toward targeted therapeutic applications, it is essential to have a complete understanding of the LMP1 signalling landscape in order to identify potential targets. The focus of this review is on LMP1-interacting proteins and related signalling processes. We further discuss tactics for using the LMP1 protein as a potential therapeutic for cancers caused by the EBV.

Targeting the signaling in Epstein-Barr virus-associated diseases: mechanism, regulation, and clinical study

Epstein–Barr virus-associated diseases are important global health concerns. As a group I carcinogen, EBV accounts for 1.5% of human malignances, including both epithelial- and lymphatic-originated tumors. Moreover, EBV plays an etiological and pathogenic role in a number of non-neoplastic diseases, and is even involved in multiple autoimmune diseases (SADs). In this review, we summarize and discuss some recent exciting discoveries in EBV research area, which including DNA methylation alterations, metabolic reprogramming, the changes of mitochondria and ubiquitin-proteasome system (UPS), oxidative stress and EBV lytic reactivation, variations in non-coding RNA (ncRNA), radiochemotherapy and immunotherapy. Understanding and learning from this advancement will further confirm the far-reaching and future value of therapeutic strategies in EBV-associated diseases.

Design and synthesis of water-soluble grifolin prodrugs for DNA methyltransferase 1 (DNMT1) down-regulation

DNA methylation and gene silencing play indispensable roles in the epigenetic landscape and gene expression. DNA methyltransferase 1 (DNMT1), a member of the DNMT family, which catalyzes the addition of methyl groups on DNA has been identified to have a close relationship with tumorigenesis. But DNMT1 inhibitors are rare except for the highly toxic nucleoside derivates. Grifolin is a unique natural product which down-regulates DNMT1 and has low toxicity. However, the poor solubility and stability of grifolin limit its application. Herein, we synthesized PEG5-Grifolin as a water-miscible prodrug of grifolin. The half-life of PEG5-Grifolin at 25 °C was considerably extended, revealing excellent stability. Meanwhile, PEG5-Grifolin suppressed tumor growth of by downregulating DNMT1 and reactivating the expression of several tumor suppressor genes in vivo. PEG5-Grifolin might be a promising demethylation agent for DNMT1 associated diseases and benefit much against various types of DNMT1 associated cancer.

In this work, a series of prodrugs of grifolin with much improved solubility and stability were designed and synthesis, which potently downregulated DNMT1 and inhibited tumor proliferation in vitro and in vivo.

DNMT1 mediates metabolic reprogramming induced by Epstein-Barr virus latent membrane protein 1 and reversed by grifolin in nasopharyngeal carcinoma

Cancer cells frequently adapt fundamentally altered metabolism to support tumorigenicity and malignancy. Epigenetic and metabolic networks are closely interactive, in which DNA methyltransferases (DNMTs) play important roles. Epstein–Barr virus (EBV)-encoded latent membrane protein 1 (EBV-LMP1) is closely associated with nasopharyngeal carcinoma (NPC) pathogenesis because it can trigger multiple cell signaling pathways that promote cell transformation, proliferation, immune escape, invasiveness, epigenetic modification, and metabolic reprogramming. Our current findings reveal for the first time that LMP1 not only upregulates DNMT1 expression and activity, but also promotes its mitochondrial translocation. This induces epigenetic silencing of pten and activation of AKT signaling as well as hypermethylation of the mtDNA D-loop region and downregulation of oxidative phosphorylation (OXPHOS) complexes, consequently, leading to metabolic reprogramming in NPC. Furthermore, we demonstrate that grifolin, a natural farnesyl phenolic compound originated from higher fungi, is able to attenuate glycolytic flux and recover mitochondrial OXPHOS function by inhibiting DNMT1 expression and activity as well as its mitochondrial retention in NPC cells. Therefore, our work establishes a mechanistic connection between epigenetics and metabolism in EBV-positive NPC and provides further evidence for pathological classification based on CpG island methylator phenotype (CIMP) in EBV-associated malignancies. In addition, grifolin might be a promising lead compound in the intervention of high-CIMP tumor types. The availability of this natural product could hamper tumor cell metabolic reprogramming by targeting DNMT1.

EBV based cancer prevention and therapy in nasopharyngeal carcinoma

Epstein-Barr virus is an important cancer causing virus. Nasopharyngeal carcinoma is an infection-related cancer strongly driven by Epstein-Barr virus. In this cancer model, we identified the major host targets of latent membrane protein 1 which is a driving oncogene encoded by Epstein-Barr virus in latency infection. latent membrane protein 1 activates several oncogenic signaling axes causing multiple malignant phenotypes and therapeutic resistance. Also, Epstein-Barr virus up-regulates DNA methyltransferase 1 and mediates onco-epigenetic effects in the carcinogenesis. The collaborating pathways activated by latent membrane protein 1 constructs an oncogenic signaling network, which makes latent membrane protein 1 an important potential target for effective treatment or preventive intervention. In Epstein-Barr virus lytic phase, the plasma level of Epstein-Barr virus DNA is considered as a distinguishing marker for nasopharyngeal carcinoma in subjects from healthy high-risk populations and is also a novel prognostic marker in Epstein-Barr virus-positive nasopharyngeal carcinoma. Now the early detection and screening of the lytic proteins and Epstein-Barr virus DNA have been applied to clinical and high-risk population. The knowledge generated regarding Epstein-Barr virus can be used in Epstein-Barr virus based precision cancer prevention and therapy in the near future.

Grifolin inhibits tumor cells adhesion and migration via suppressing interplay between PGC1α and Fra-1 / LSF- MMP2 / CD44 axes

Grifolin, a farnesyl phenolic compound isolated from the fresh fruiting bodies of the mushroom Albatrellus confluens, exhibits effective antitumor bioactivity in previous study of our group and other lab. In this study, we observed that grifolin inhibited tumor cells adhesion and migration. Moreover, grifolin reduced reactive oxygen species (ROS) production and caused cellular ATP depletion in high-metastatic tumor cells. PGC1α (Peroxisome proliferator-activated receptor γ, coactivator 1α) encodes a transcriptional co-activator involved in mitochondrial biogenesis and respiration and play a critical role in the maintenance of energy homeostasis. Interestingly, grifolin suppressed the mRNA as well as protein level of PGC1α. We further identified that MMP2 and CD44 expressions were PGC1α inducible. PGC1α can bind with metastatic-associated transcription factors: Fra-1 and LSF and the protein-protein interaction was attenuated by grifolin treatment. Overall, these findings suggest that grifolin decreased ROS generation and intracellular ATP to suppress tumor cell adhesion/migration via impeding the interplay between PGC1α and Fra-1 /LSF-MMP2/CD44 axes. Grifolin may develop as a promising lead compound for antitumor therapies by targeting energy metabolism regulator PGC1α signaling.

Grifolin directly targets ERK1/2 to epigenetically suppress cancer cell metastasis

Grifolin, a secondary metabolite isolated from the fresh fruiting bodies of the mushroom Albatrellus confluens, has been reported by us and others to display potent antitumor effects. However, the molecular target of grifolin has not been identified and the underlying mechanism of action is not fully understood. Here, we report that the ERK1/2 protein kinases are direct molecular targets of grifolin. Molecular modeling, affinity chromatography and fluorescence quenching analyses showed that grifolin directly binds to ERK1/2. And in vitro and ex vivo kinase assay data further demonstrated that grifolin inhibited the kinase activities of ERK1/2. We found that grifolin suppressed adhesion, migration and invasion of high-metastatic cancer cells. The inhibitory effect of grifolin against tumor metastasis was further confirmed in a metastatic mouse model. We found that grifolin decreased phosphorylation of Elk1 at Ser383, and the protein as well as the mRNA level of DNMT1 was also down-regulated. By luciferase reporter and ChIP assay analyses, we confirmed that grifolin inhibited the transcription activity of Elk1 as well as its binding to the dnmt1 promoter region. Moreover, we report that significant increases in the mRNA levels of Timp2 and pten were induced by grifolin. Thus, our data suggest that grifolin exerts its anti-tumor activity by epigenetic reactivation of metastasis inhibitory-related genes through ERK1/2-Elk1-DNMT1 signaling. Grifolin may represent a promising therapeutic lead compound for intervention of cancer metastasis, and it may also be useful as an ERK1/2 kinase inhibitor as well as an epigenetic agent to further our understanding of DNMT1 function.

The role of targeting kinase activity by natural products in cancer chemoprevention and chemotherapy (Review)

The WHO clearly identifies tumors as a curable or a chronic disease. The use of natural agents in cancer prevention and therapy is currently playing an important role. Our laboratory has been investigating various natural phenolic compounds, including grifolin, neoalbaconol and epigallocatechin-3-gallate (EGCG). In the present review, we focus on the anticancer activities and the molecular mechanisms of these compounds. Grifolin, a secondary metabolite isolated from the mushroom Albatrellus confluens, has been shown to inhibit cell growth and induce cell cycle arrest in multiple cancer cell lines by targeting extracellular signal-regulated kinase 1 or by upregulating death-associated protein kinase 1 (DAPK1) via p53. We also demonstrated that neoalbaconol, a novel small-molecular compound with a drimane-type sesquiterpenoid structure obtained from Albatrellus confluens, regulates cell metabolism by targeting 3-phosphoinositide-dependent protein kinase 1 (PDK1) and inhibits cancer cell growth. EGCG, a well known catechin found in tea, has gained much attention for its anticancer effects. Previously, we found that it regulates EBV lytic infection through the phosphoinositide-3 kinase/Akt (PI3K/Akt) and mitogen-activated protein kinase (MAPK) pathways in EBV-positive cancer cells. Therefore, these natural agents could be used as potential leading compounds in the prevention of tumor progression and/or EBV-related cancer.

Tissue invasion and metastasis: Molecular, biological and clinical perspectives

Cancer is a key health issue across the world, causing substantial patient morbidity and mortality. Patient prognosis is tightly linked with metastatic dissemination of the disease to distant sites, with metastatic diseases accounting for a vast percentage of cancer patient mortality. While advances in this area have been made, the process of cancer metastasis and the factors governing cancer spread and establishment at secondary locations is still poorly understood. The current article summarizes recent progress in this area of research, both in the understanding of the underlying biological processes and in the therapeutic strategies for the management of metastasis. This review lists the disruption of E-cadherin and tight junctions, key signaling pathways, including urokinase type plasminogen activator (uPA), phosphatidylinositol 3-kinase/v-akt murine thymoma viral oncogene (PI3K/AKT), focal adhesion kinase (FAK), β-catenin/zinc finger E-box binding homeobox 1 (ZEB-1) and transforming growth factor beta (TGF-β), together with inactivation of activator protein-1 (AP-1) and suppression of matrix metalloproteinase-9 (MMP-9) activity as key targets and the use of phytochemicals, or natural products, such as those from Agaricus blazei, Albatrellus confluens, Cordyceps militaris, Ganoderma lucidum, Poria cocos and Silybum marianum, together with diet derived fatty acids gamma linolenic acid (GLA) and eicosapentanoic acid (EPA) and inhibitory compounds as useful approaches to target tissue invasion and metastasis as well as other hallmark areas of cancer. Together, these strategies could represent new, inexpensive, low toxicity strategies to aid in the management of cancer metastasis as well as having holistic effects against other cancer hallmarks.

One new ergostane-type steroid and three new phthalide derivatives from cultures of the basidiomycete Albatrellus confluens

One new ergostane-type steroid, (12β,15β,22R,23S,24S)-22,25-epoxy-12,15,23-trihydroxyergost-4,6,8(14)-trien-3-one (1), three new phthalide derivatives, 5-(2',3'-epoxy-3',3'-dimethylpropoxy)-7-methoxy-6-methylphthalide (2), (2')-(Z)-5-(3'-hydroxymethyl-3'-methylallyloxy)-7-methoxy-6-methylphthalide (3), and 5-(3',3'-dimethylallyloxy)-7-hydroxy-6-methylphthalide (4), along with one known phthalide derivative, 5-(3',3'-dimethylallyloxy)-7-methoxy-6-methylphthalide (5), were isolated from cultures of the basidiomycete Albatrellus confluens. The structures of the new compounds were established on the basis of extensive spectroscopic data (IR, MS, 1D, and 2D NMR) analyses. All compounds were evaluated for their cytotoxic activities on five tumor cell lines.

Ten new aurovertins from cultures of the basidiomycete Albatrellus confluens

Aurovertins J-S (1–10), together with four known metabolites, aurovertins B, C, E, and I (11–14), were isolated from cultures of the basidiomycete Albatrellus confluens. The structures of compounds 1–10 were elucidated on the basis of extensive spectroscopic analysis. All compounds were evaluated for their cytotoxic activities on five tumor cell lines.

MiR-328 expression is decreased in high-grade gliomas and is associated with worse survival in primary glioblastoma

MicroRNAs, a group of small endogenous, noncoding RNAs, are aberrantly expressed in many human cancers and can act as oncogene or anti-oncogene. Recent evidence suggests that some miRNAs have prognostic value for tumors. MiR-328 is known as a tumor suppressor; however, its relationship with the clinicopathological features of glioblastoma (GBM) and its prognostic value has yet not been investigated. We found that expression of miR-328 was significantly decreased both in anaplastic and GBM cohorts and that low miR-328 expression also conferred poor survival in primary GBM (PGBM) patients. MiR-328 might, therefore, serve as an independent prognostic marker. Furthermore, expression profiles of miR-328-associated mRNAs were established via microarrays for 60 GBM samples. The ontology of the miR-328-associated genes was then analyzed, which identified gene sets tightly related to cell mitosis. In addition, ectopic expression of miR-328 inhibited U87 cell proliferation and induced U87 cell cycle arrest. In conclusion, this is the first report showing that miR-328 is associated with patient’s survival time and that miR-328 might serve as an independent prognostic biomarker for GBM.

Differential regulation of p21 (waf1) protein half-life by DNA damage and Nutlin-3 in p53 wild-type tumors and its therapeutic implications

DNA damage induces the canonical p53 pathway including elevation of p21 (waf1) resulting in arrest of cell cycle progression. This can protect cells from subsequent Chk1 inhibition. Some p53 wild-type cancer cells such as HCT116 and U2OS exhibit attenuated p21 (waf1) induction upon DNA damage due to translational inhibition, and are incapable of maintaining arrest upon Chk1 inhibition. The purpose of this study was to determine whether this attenuated p21 (waf1) induction also occurred with the non-DNA damaging agent Nutlin-3 which induces p53 by disrupting binding to its negative regulator MDM2. We find that Nutlin-3 circumvented the attenuated induction of p21 (waf1) protein by increasing its half-life which led to G 1 and G 2 arrest in both cell lines. Interestingly, the p21 (waf1) protein half-life remained short on Nutlin-3 in p53 wild-type MCF10A cells; these cells achieve high p21 (waf1) levels through transcriptional upregulation. Consequently, all three p53 wild-type cells but not p53 mutant MDA-MB-231 cancer cells were protected from subsequent incubation with a combination of DNA damage plus a checkpoint inhibitor.

Increased aldehyde reductase expression mediates acquired radioresistance of laryngeal cancer cells via modulating p53

The main obstacle to cure tumors by radiotherapy has been ascribed to tumor radioresistance. To determine the mechanisms underlying resistance to irradiation, it is essential to compare proteins differentially expressed from radiotherapy-sensitive and -resistant cancer cells. Aldehyde reductase (AKR1A1) was recently identified as increased in radioresistant laryngeal cancer cells by comparative proteomics approach. Here, we provide the mechanism of AKR1A1-mediated radioresistance via p53 regulation in laryngeal cancer cells. AKR1A1 induction was correlated with the radioresistant phenotype of laryngeal cancer HEp-2 cells. AKR1A1 depletion with siRNA significantly enhanced radiation sensitivity of radioresistant HEp-2 cells by promoting radiation-induced cell death and accelerated radiation-mediated inhibition of cell proliferation, without affecting either the PI3K-Akt or MAPK-ERK pathways. Intriguingly, AKR1A1 depletion induced phosphorylation of p53 at serine 15 and G 2/M transition in response to irradiation. We further found that AKR1A1 interacted with p53 and this interaction was dramatically increased in the irradiated radioresistant cells compared with the control cells. AKR1A1 expression also regulated p53 stability in response to irradiation. Furthermore, AKR1A1 depletion only sensitized HCT116 cells expressing p53 to irradiation and not p53-deficient cells. Therefore, our data suggest that radiation-inducible AKR1A1 contributes to acquired radioresistance of laryngeal cancer cells by suppressing p53 activation through inhibitory interaction.