Amurensin G, a novel SIRT1 inhibitor, sensitizes TRAIL-resistant human leukemic K562 cells to TRAIL-induced apoptosis

EX527, a sirtuins 1 inhibitor, sensitizes T-cell leukemia to death receptor-mediated apoptosis by downregulating cellular FLICE inhibitory protein

Death receptor-mediated extrinsic apoptosis system had been developed as a promising therapeutic strategy in clinical oncology, such as TRAIL therapy. However, multiple studies have demonstrated that TRAIL resistance is the biggest problem for disappointing clinical trials despite preclinical success. Targeting cellular FLICE inhibitory protein (cFLIP) is one strategy of combinatorial therapies to overcome resistance to DR-mediated apoptosis due to its negative regulator of extrinsic apoptosis. E × 527 (Selisistat) is a specific inhibitor of SIRT1 activity with safe and well tolerance in clinical trials. Here, we show that E × 527 could strengthen significantly activation of rhFasL-mediated apoptotic signaling pathway and increased apoptotic rate of T leukemia cells with high expression of cFLIP. Mechanically, Inhibition of SIRT1 by E × 527 increased polyubiquitination level of cFLIP via increasing acetylation of Ku70, which could promote proteosomal degradation of cFLIP protein. It implied that combinatorial therapies of E × 527 plus TRAIL may have a potential as a novel clinical application for TRAIL-resistant hematologic malignancies.

Amurensin G Sensitized Cholangiocarcinoma to the Anti-Cancer Effect of Gemcitabine via the Downregulation of Cancer Stem-like Properties

Cholangiocarcinoma (CCA) is a malignant biliary tract tumor with a high mortality rate and refractoriness to chemotherapy. Gemcitabine is an anti-cancer chemotherapeutic agent used for CCA, but the efficacy of gemcitabine in CCA treatment is limited, due to the acquisition of chemoresistance. The present study evaluated the chemosensitizing effects of Amurensin G (AMG), a natural sirtuin-1 inhibitor derived from Vitis amurensis, in the SNU-478 CCA cells. Treatment with AMG decreased the SNU-478 cell viability and the colony formation ability. Annexin V/ Propidium iodide staining showed that the AMG increased apoptotic death. In addition, AMG downregulated anti-apoptotic Bcl-2 expression, while upregulating pro-apoptotic cleaved caspase-3 expression. Treatment with AMG decreased the migratory ability of the cells in a wound healing assay and transwell migration assay. It was observed that AMG decreased the gemcitabine-induced increase in CD44highCD24highCD133high cell populations, and the expression of the Sox-2 protein was decreased by AMG treatment. Co-treatment of AMG with gemcitabine significantly enhanced the production of reactive oxygen species, as observed through mitochondrial superoxide staining, which might be associated with the downregulation of the Sirt1/Nrf2 pathway by AMG. These results indicate that AMG enhances the chemotherapeutic ability of gemcitabine by downregulating cancer stem-like properties in CCA cells. Hence, a combination therapy of AMG with gemcitabine may be an attractive therapeutic strategy for cholangiocarcinoma.

Apoptosis: a Janus bifrons in T-cell immunotherapy

Immunotherapy has revolutionized the treatment of cancer. In particular, immune checkpoint blockade, bispecific antibodies, and adoptive T-cell transfer have yielded unprecedented clinical results in hematological malignancies and solid cancers. While T cell-based immunotherapies have multiple mechanisms of action, their ultimate goal is achieving apoptosis of cancer cells. Unsurprisingly, apoptosis evasion is a key feature of cancer biology. Therefore, enhancing cancer cells' sensitivity to apoptosis represents a key strategy to improve clinical outcomes in cancer immunotherapy. Indeed, cancer cells are characterized by several intrinsic mechanisms to resist apoptosis, in addition to features to promote apoptosis in T cells and evade therapy. However, apoptosis is double-faced: when it occurs in T cells, it represents a critical mechanism of failure for immunotherapies. This review will summarize the recent efforts to enhance T cell-based immunotherapies by increasing apoptosis susceptibility in cancer cells and discuss the role of apoptosis in modulating the survival of cytotoxic T lymphocytes in the tumor microenvironment and potential strategies to overcome this issue.

Bis(chloroacetamidino)-Derived Heteroarene-Fused Anthraquinones Bind to and Cause Proteasomal Degradation of tNOX, Leading to c-Flip Downregulation and Apoptosis in Oral Cancer Cells

Simple Summary

New-generation anthraquinone derivatives attached with different heterocycles and bearing chloroacetamidines in the side chains have been synthesized to reduce side effects and drug resistance. In this study, we identified the cellular target of the studied compounds through ligand binding assays and in silico simulations. Our results illustrate that the studied compounds bound to and targeted the tumor-associated NADH oxidase (tNOX) in oral cancer cells. tNOX is a growth-related protein and is found to be expressed in cancer cells but not in non-transformed cells, and its knockdown by RNA interference in tumor cells overturns cancer phenotypes, supporting its role in cellular growth. We also identified that tNOX bound to the studied compounds and underwent degradation, which was correlated with apoptosis induction in oral cancer cells.

Abstract

Anthraquinone-based intercalating compounds, namely doxorubicin and mitoxantrone, have been used clinically based on their capacity to bind DNA and induce DNA damage. However, their applications have been limited by side effects and drug resistance. New-generation anthraquinone derivatives fused with different heterocycles have been chemically synthesized and screened for higher anticancer potency. Among the compounds reported in our previous study, 4,11-bis(2-(2-chloroacetamidine)ethylamino)anthra[2,3-b]thiophene-5,10-dione dihydrochloride (designated 2c) was found to be apoptotic, but the direct cellular target responsible for the cytotoxicity remained unknown. Here, we report the synthesis and anticancer properties of two other derivatives, 4,11-bis(2-(2-chloroacetamidine)ethylamino)naphtho[2,3-f]indole-5,10-dione dihydrochloride (2a) and 4,11-bis(2-(2-chloroacetamidine)ethylamino)-2-methylanthra[2,3-b]furan-5,10-dione dihydrochloride (2b). We sought to identify and validate the protein target(s) of these derivatives in oral cancer cells, using molecular docking simulations and cellular thermal shift assays (CETSA). Our CETSA results illustrate that these derivatives targeted the tumor-associated NADH oxidase (tNOX, ENOX2), and their direct binding downregulated tNOX in p53-functional SAS and p53-mutated HSC-3 cells. Interestingly, the compounds targeted and downregulated tNOX to reduce SIRT1 deacetylase activity and increase Ku70 acetylation, which triggers c-Flip ubiquitination and induces apoptosis in oral cancer cells. Together, our data highlight the potential value of these heteroarene-fused anthraquinones in managing cancer by targeting tNOX and augmenting apoptosis.

Regulation of extrinsic apoptotic signaling by c-FLIP: towards targeting cancer networks

The extrinsic pathway is mediated by death receptors (DRs), including CD95 (APO-1/Fas) or TRAILR-1/2. Defects in apoptosis regulation lead to cancer and other malignancies. The master regulator of the DR networks is the cellular FLICE inhibitory protein (c-FLIP). In addition to its key role in apoptosis, c-FLIP may exert other cellular functions, including control of necroptosis, pyroptosis, nuclear factor κB (NF-κB) activation, and tumorigenesis. To gain further insight into the molecular mechanisms of c-FLIP action in cancer networks, we focus on the structure, isoforms, interactions, and post-translational modifications of c-FLIP. We also discuss various avenues to target c-FLIP in cancer cells for therapeutic benefit.

Recent advances in the combination delivery of drug for leukemia and other cancers

Introduction: Combination therapy has been explored for its potential to reduce or eliminate multidrug resistance in treating different types of cancer including leukemia. Nutraceutical, small molecular drugs, and small interfering ribonucleic acid (siRNA) are some of the effective drugs. In order to avoid off-site targeting, reduce the dosage required, and increase the half-life of the drug in the circulation system, drug delivery vehicles, such as nanoparticles and microfibers have been explored.Areas covered: This review summarizes various therapies utilized in treating leukemia based on their effectiveness in inducing protein inhibition and/or apoptosis. In particular, treatment effectiveness using combination therapy using various devices is addressed. Recently explored drug delivery methods are reviewed, providing examples and their applications in cancer treatment. The drug listing, delivery systems classifications, along with the general modeling approach in this review, provide, to a full extent, a basis for cancer drug delivery future studies.Expert opinion: The reviewer's opinion tackles the potential of using a multi-delivery system to deliver multiple drugs, providing better control upon drug release and targeting. Both local and systemic delivery are considered and explored for their potential targets. Researchers are advised to pre-consider all aspects associated with their desired delivery method.

Developing TRAIL/TRAIL death receptor-based cancer therapies

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a member of the TNF superfamily that can initiate the apoptosis pathway by binding to its associated death receptors DR4 and DR5. The activation of the TRAIL pathway in inducing tumor-selective apoptosis leads to the development of TRAIL-based cancer therapies, which include recombinant forms of TRAIL, TRAIL receptor agonists, and other therapeutic agents. Importantly, TRAIL, DR4, and DR5 can all be induced by synthetic and natural agents that activate the TRAIL apoptosis pathway in cancer cells. Thus, understanding the regulation of the TRAIL apoptosis pathway can aid in the development of TRAIL-based therapies for the treatment of human cancer.

Engagement with tNOX (ENOX2) to Inhibit SIRT1 and Activate p53-Dependent and -Independent Apoptotic Pathways by Novel 4,11-Diaminoanthra[2,3-b]furan-5,10-diones in Hepatocellular Carcinoma Cells

Hepatocellular carcinoma (HCC) is the most frequent primary malignancy of the liver and is among the top three causes of cancer-associated death worldwide. However, the clinical use of chemotherapy for HCC has been limited by various challenges, emphasizing the urgent need for novel agents with improved anticancer properties. We recently synthesized and characterized a series of 4,11-diaminoanthra[2,3-b]furan-5,10-dione derivatives that exhibit potent apoptotic activity against an array of cancer cell lines, including variants with multidrug resistance. Their effect on liver cancer cells, however, was unknown. Here, we investigated three selected 4,11-diaminoanthra[2,3-b]furan-5,10-dione derivatives (compounds 1–3) for their cytotoxicity and the underlying molecular mechanisms in wild-type or p53-deficient HCC cells. Cytotoxicity was determined by WST-1 assays and cell impedance measurements and apoptosis was analyzed by flow cytometry. The interaction between compounds and tumor-associated NADH oxidase (tNOX, ENOX2) was studied by cellular thermal shift assay (CETSA). We found that compound 1 and 2 induced significant cytotoxicity in both HepG2 and Hep3B lines. CETSA revealed that compounds 1 and 2 directly engaged with tNOX, leading to a decrease in the cellular NAD⁺/NADH ratio. This decreased the NAD⁺-dependent activity of Sirtuin 1 (SIRT1) deacetylase. In p53-wild-type HepG2 cells, p53 acetylation/activation was enhanced, possibly due to the reduction in SIRT1 activity, and apoptosis was observed. In p53-deficient Hep3B cells, the reduction in SIRT1 activity increased the acetylation of c-Myc, thereby reactivating the TRAIL pathway and, ultimately leading to apoptosis. These compounds thus trigger apoptosis in both cell types, but via different pathways. Taken together, our data show that derivatives 1 and 2 of 4,11-diaminoanthra[2,3-b]furan-5,10-diones engage with tNOX and inhibit its oxidase activity. This results in cytotoxicity via apoptosis through tNOX-SIRT1 axis to enhance the acetylation of p53 or c-Myc in HCC cells, depending on their p53 status.

Inhibition of SIRT1 deacetylase and p53 activation uncouples the anti-inflammatory and chemopreventive actions of NSAIDs

Background

Nonsteroidal anti-inflammatory drugs (NSAIDs) have been proposed as chemopreventive agents for many tumours; however, the mechanism responsible for their anti-neoplastic activity remains elusive and the side effects due to cyclooxygenase (COX) inhibition prevent this clinical application.

Methods

Molecular biology, in silico, cellular and in vivo tools, including innovative in vivo imaging and classical biochemical assays, were applied to identify and characterise the COX-independent anti-cancer mechanism of NSAIDs.

Results

Here, we show that tumour-protective functions of NSAIDs and exisulind (a sulindac metabolite lacking anti-inflammatory activity) occur through a COX-independent mechanism. We demonstrate these NSAIDs counteract carcinogen-induced proliferation by inhibiting the sirtuin 1 (SIRT1) deacetylase activity, augmenting acetylation and activity of the tumour suppressor p53 and increasing the expression of the antiproliferative gene p21. These properties are shared by all NSAIDs except for ketoprofen lacking anti-cancer properties. The clinical interest of the mechanism identified is underlined by our finding that p53 is activated in mastectomy patients undergoing intraoperative ketorolac, a treatment associated with decreased relapse risk and increased survival.

Conclusion

Our study, for the first-time, links NSAID chemopreventive activity with direct SIRT1 inhibition and activation of the p53/p21 anti-oncogenic pathway, suggesting a novel strategy for the design of tumour-protective drugs.

Vitis amurensis Rupr: A review of chemistry and pharmacology

PURPOSE

Vitis amurensis Rupr. from the family Vitaceae, is a grape species native to the Asian continent. It is a highly attractive plant, used widely worldwide. It has been used for several hundred years as a traditional Chinese herb. The review focuses on the botanical description, traditional uses, phytochemistry, and the biological activities of Vitis amurensis Rupr. to evaluate its therapeutic potential uses.

METHODS

This review summarizes the published data concerning the botanical aspects, traditional usage, phytochemistry, and pharmacology of Vitis amurensis Rupr., to evaluate its therapeutic potential as an important source of natural compounds with effect activities that benefit human health.

RESULTS

Vitis amurensis Rupr. has been used for several hundred years as a traditional Chinese herb to treat stranguria, rheumatoid arthritis-associated edema, chronic hepatitis, nephritis, chronic arthritis and traumatic hemorrhage. It is a particularly rich source of the oligostilbenes, flavonoids, and anthocyanins, phytochemicals that are associated with antioxidant, anti-inflammatory, antibacterial and cardioprotective activities. Due to the presence of a multitude of bioactives, a wide array of pharmacological activities have been ascribed to different parts of this herb and individual compounds, which include antioxidant, antimicrobial, anti-inflammatory, anticancer, anti-aging, anti-melanogenic, anti-allergic and anti-viral.

CONCLUSION

From a health perspective, Vitis amurensis Rupr. presents excellent options for treating various diseases due to its bioactive compounds (drug candidates) that exhibit important activities or for developing new products.

FLIP as a therapeutic target in cancer

One of the classic hallmarks of cancer is disruption of cell death signalling. Inhibition of cell death promotes tumour growth and metastasis, causes resistance to chemo- and radiotherapies as well as targeted agents, and is frequently due to overexpression of antiapoptotic proteins rather than loss of pro-apoptotic effectors. FLIP is a major apoptosis-regulatory protein frequently overexpressed in solid and haematological cancers, in which its high expression is often correlated with poor prognosis. FLIP, which is expressed as long (FLIP(L)) and short (FLIP(S)) splice forms, achieves its cell death regulatory functions by binding to FADD, a critical adaptor protein which links FLIP to the apical caspase in the extrinsic apoptotic pathway, caspase-8, in a number of cell death regulating complexes, such as the death-inducing signalling complexes (DISCs) formed by death receptors. FLIP also plays a key role (together with caspase-8) in regulating another form of cell death termed programmed necrosis or 'necroptosis', as well as in other key cellular processes that impact cell survival, including autophagy. In addition, FLIP impacts activation of the intrinsic mitochondrial-mediated apoptotic pathway by regulating caspase-8-mediated activation of the pro-apoptotic Bcl-2 family member Bid. It has been demonstrated that FLIP can not only inhibit death receptor-mediated apoptosis, but also cell death induced by a range of clinically relevant chemotherapeutic and targeted agents as well as ionizing radiation. More recently, key roles for FLIP in promoting the survival of immunosuppressive tumour-promoting immune cells have been discovered. Thus, FLIP is of significant interest as an anticancer therapeutic target. In this article, we review FLIP's biology and potential ways of targeting this important tumour and immune cell death regulator.

Pharmacological Targeting of Cell Cycle, Apoptotic and Cell Adhesion Signaling Pathways Implicated in Chemoresistance of Cancer Cells

Chemotherapeutic drugs target a physiological differentiating feature of cancer cells as they tend to actively proliferate more than normal cells. They have well-known side-effects resulting from the death of highly proliferative normal cells in the gut and immune system. Cancer treatment has changed dramatically over the years owing to rapid advances in oncology research. Developments in cancer therapies, namely surgery, radiotherapy, cytotoxic chemotherapy and selective treatment methods due to better understanding of tumor characteristics, have significantly increased cancer survival. However, many chemotherapeutic regimes still fail, with 90% of the drug failures in metastatic cancer treatment due to chemoresistance, as cancer cells eventually develop resistance to chemotherapeutic drugs. Chemoresistance is caused through genetic mutations in various proteins involved in cellular mechanisms such as cell cycle, apoptosis and cell adhesion, and targeting those mechanisms could improve outcomes of cancer therapy. Recent developments in cancer treatment are focused on combination therapy, whereby cells are sensitized to chemotherapeutic agents using inhibitors of target pathways inducing chemoresistance thus, hopefully, overcoming the problems of drug resistance. In this review, we discuss the role of cell cycle, apoptosis and cell adhesion in cancer chemoresistance mechanisms, possible drugs to target these pathways and, thus, novel therapeutic approaches for cancer treatment.

Novel indazole-based small compounds enhance TRAIL-induced apoptosis by inhibiting the MKK7-TIPRL interaction in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most malignant tumors. Although various treatments, such as surgery and chemotherapy, have been developed, a novel alternative therapeutic approach for HCC therapy is urgently needed. Tumor necrosis factor-related apoptosis inducing ligand (TRAIL) is a promising anti-cancer agent, but many cancer cells are resistant to TRAIL-induced apoptosis. To help overcome TRAIL resistance in HCC cancer cells, we have identified novel chemical compounds that act as TRAIL sensitizers. We first identified the hit compound, TRT-0002, from a chemical library of 6,000 compounds using a previously developed high-throughput enzyme-linked immunosorbent assay (ELISA) screening system, which was based on the interaction of mitogen-activated protein kinase kinase 7 (MKK7) and TOR signaling pathway regulator-like (TIPRL) proteins and a cell viability assay. To increase the efficacy of this TRAIL sensitizer, we synthesized 280 analogs of TRT-0002 and finally identified two lead compounds (TRT-0029 and TRT-0173). Co-treating cultured Huh7 cells with either TRT-0029 or TRT-0173 and TRAIL resulted in TRAIL-induced apoptosis due to the inhibition of the MKK7-TIPRL interaction and subsequent phosphorylation of MKK7 and c-Jun N-terminal kinase (JNK). In vivo, injection of these compounds and TRAIL into HCC xenograft tumors resulted in tumor regression. Taken together, our results suggest that the identified lead compounds serve as TRAIL sensitizers and represent a novel strategy to overcome TRAIL resistance in HCC.

Gnetin-C and other resveratrol oligomers with cancer chemopreventive potential

Resveratrol has been extensively studied to investigate its biological effects, including its chemopreventive potential against cancer. Over the past decade, various resveratrol oligomers, both naturally occurring and synthetic, have been described. These resveratrol oligomers result from the polymerization of two or more resveratrol units to form dimers, trimers, tetramers, or even more complex derivatives. Some oligomers appear to have antitumor activities that are similar or superior to monomeric resveratrol. In this review, we discuss resveratrol oligomers with anticancer potential, with emphasis on well-characterized compounds, such as the dimer gnetin-C and other oligomers from Gnetum gnemon, whose safety, pharmacokinetic, and biological activities have been studied in humans.

Natural Agents-Mediated Targeting of Histone Deacetylases

In the past few years, basic and clinical scientists have witnessed landmark achievements in many research projects, such as those conducted by the US National Institutes of Health Roadmap Epigenomics Mapping Consortium, the International Human Epigenome Consortium, The Cancer Genome Atlas Network and the International Cancer Genome Consortium, which have provided near-complete resolution of epigenetic landscape in different diseases. Furthermore, genome sequencing of tumors has provided compelling evidence related to frequent existence of mutations in readers, erasers and writers of epigenome in different cancers. Histone acetylation is an intricate mechanism modulated by two opposing sets of enzymes and deeply studied as a key biological phenomenon in 1964 by Vincent Allfrey and colleagues. The research group suggested that this protein modification contributed substantially in transcriptional regulation. Subsequently, histone deacetylases (HDACs), histone acetyltransferases and acetyl-Lys-binding proteins were identified as transcriptional mediators, which further deepened our comprehension regarding biochemical modifications. Overwhelmingly increasing high-impact research is improving our understanding of this molecularly controlled mechanism; moreover, quantification and identification of lysine acetylation by mass spectrometry has added new layers of information. We partition this multi-component review into how both activity and expression of HDAC are targeted using natural agents. We also set spotlight on how oncogenic fusion proteins tactfully utilize HDAC-associated nano-machinery to modulate expression of different genes and how HDAC inhibitors regulate TRAIL-induced apoptosis in cancer cells. HDAC inhibitors have been reported to upregulate expression of TRAIL receptors and protect TRAIL from proteasomal degradation. Deeper understanding of HDAC biology will be useful for stratification and selection of patients who are responders, non-responders and poor-responders for HDACi therapy, and for the rational design of combination studies using HDACi.

Tumor-associated NADH oxidase (tNOX)-NAD+-sirtuin 1 axis contributes to oxaliplatin-induced apoptosis of gastric cancer cells

Oxaliplatin belongs to the platinum-based drug family and has shown promise in cancer treatment. The major mechanism of action of platinum compounds is to form platinum–DNA adducts, leading to DNA damage and apoptosis. Accumulating evidence suggests that they might also target non-DNA molecules for their apoptotic activity. We explored the effects of oxaliplatin on a tumor-associated NADH oxidase (tNOX) in gastric cancer lines. In AGS cells, we found that the oxaliplatin-inhibited tNOX effectively attenuated the NAD⁺/NADH ratio and reduced the deacetylase activity of an NAD⁺-dependent sirtuin 1, thereby enhancing p53 acetylation and apoptosis. Similar results were also observed in tNOX-knockdown AGS cells. In the more aggressive MKN45 and TMK-1 lines, oxaliplatin did not inhibit tNOX, and induced only minimal apoptosis and cytotoxicity. However, the downregulation of either sirtuin 1 or tNOX sensitized TMK-1 cells to oxaliplatin-induced apoptosis. Moreover, tNOX-depletion in these resistant cells enhanced spontaneous apoptosis, reduced cyclin D expression and prolonged the cell cycle, resulting in diminished cancer cell growth. Together, our results demonstrate that oxaliplatin targets tNOX and SIRT1, and that the tNOX-NAD⁺-sirtuin 1 axis is essential for oxaliplatin-induced apoptosis.

Knockdown of TNF receptor-associated factor 2 (TRAF2) modulates in vitro growth of TRAIL-treated prostate cancer cells

TNF receptor-associated factor 2 (TRAF2) is documented to regulate tumor development and progression. Currently, the effect of TRAF2 on growth of androgen-refractory prostate cancer in response to TRAIL and the molecular mechanisms are not well understood. Here, we aim to investigate the effect of TRAF2 on in vitro growth of human androgen-insensitive prostate cancer DU-145 cells in the presence of TRAIL. Bioinformatics analysis of the Cancer Genome Atlas (TCGA) data was performed to examine TRAF2 expression and the prognostic value in prostate cancer. Microarray data of GSE21032 dataset were downloaded from Gene Expression Omnibus (GEO) to explore TRAF2 expression in metastatic prostate cancer. Bioinformatics analysis was further conducted to investigate the association of TRAF2 expression with recurrence-free survival in prostate cancer patients. Colony formation, cell viability, and Annexin V/PI apoptosis assays were performed to investigate the effect of TRAF2 on in vitro growth and apoptosis in TRAIL-treated DU-145 cells. The expression levels of mRNA and protein were detected by quantitative RT-PCR and immunoblotting assays. Bioinformatics analysis indicated that TRAF2 expression is significantly upregulated in prostate cancer patients with high Gleason scores (GS>7) compared with those with low Gleason scores (GS≤7). Upregulation of TRAF2 expression is significantly associated with recurrence-free survival in patients. In addition, TRAF2 knockdown can enhance apoptosis and downregulate SIRT1 expression in TRAIL-treated DU-145 cells. In vitro experiments further showed that SIRT1 knockdown can inhibit growth, and promote apoptosis in TRAIL-treated DU-145 cells. Overall, TRAF2 can influence in vitro growth of TRAIL-treated DU-145 cells at least partially via regulating SIRT1 expression, and may be a potentially valuable biomarker predicting recurrence-free survival in prostate cancer patients.

Anticancer Effects of a New SIRT Inhibitor, MHY2256, against Human Breast Cancer MCF-7 Cells via Regulation of MDM2-p53 Binding

The sirtuins (SIRTs), a family of NAD⁺-dependent class III histone deacetylase, are involved in various biological processes including cell survival, division, senescence, and metabolism via activation of the stress-response pathway. Recently, inhibition of SIRTs has been considered a promising anticancer strategy, but their precise mechanisms of action are not well understood. In particular, the relevance of p53 to SIRT-induced effects has not been fully elucidated. We investigated the anticancer effects of a novel SIRT inhibitor, MHY2256, and its efficacy was compared to that of salermide in MCF-7 (wild-type p53) and SKOV-3 (null-type p53) cells. Cell viability, SIRT1 enzyme activity, cell cycle regulation, apoptosis, and autophagic cell death were measured. We compared sensitivity to cytotoxicity in MCF-7 and SKOV-3 cells. MHY2256 significantly decreased the viability of MCF-7 (IC₅₀, 4.8 μM) and SKOV-3 (IC₅₀, 5.6 μM) cells after a 48 h treatment period. MHY2256 showed potent inhibition (IC₅₀, 0.27 mM) against SIRT1 enzyme activity compared with nicotinamide (IC_50, >1 mM). Moreover, expression of SIRT (1, 2, or 3) protein levels was significantly reduced by MHY2256 treatment in both MCF-7 and SKOV-3 cells. Flow cytometry analysis revealed that MHY2256 significantly induced cell cycle arrest in the G1 phase, leading to an effective increase in apoptotic cell death in MCF-7 and SKOV-3 cells. A significant increase in acetylated p53, a target protein of SIRT, was observed in MCF-7 cells after MHY2256 treatment. MHY2256 up-regulated LC3-II and induced autophagic cell death in MCF-7 cells. Furthermore, MHY2256 markedly inhibited tumor growth in a tumor xenograft model of MCF-7 cells. These results suggest that a new SIRT inhibitor, MHY2256, has anticancer activity through p53 acetylation in MCF-7 human breast cancer cells.

Honokiol inhibits EMT-mediated motility and migration of human non-small cell lung cancer cells in vitro by targeting c-FLIP

AIM

Honokiol (HNK) is a natural compound isolated from the magnolia plant with numerous pharmacological activities, including inhibiting epithelial-mesenchymal transition (EMT), which has been proposed as an attractive target for anti-tumor drugs to prevent tumor migration. In this study we investigated the effects of HNK on EMT in human NSCLC cells in vitro and the related signaling mechanisms.

METHODS

TNF-α (25 ng/mL) in combination with TGF-β1 (5 ng/mL) was used to stimulate EMT of human NSCLC A549 and H460 cells. Cell proliferation was analyzed using a sulforhodamine B assay. A wound-healing assay and a transwell assay were performed to examine cell motility. Western blotting was used to detect the expression levels of relevant proteins. siRNAs were used to knock down the gene expression of c-FLIP and N-cadherin. Stable overexpression of c-FLIP L (H157-FLIP L) or Lac Z (H157-Lac Z) was also performed.

RESULTS

Treatment with TNF-α+TGF-β1 significantly enhanced the migration of A549 and H460 cells, increased c-FLIP, N-cadherin (a mesenchymal marker), snail (a transcriptional modulator) and p-Smad2/3 expression, and decreased IκB levels in the cells; these changes were abrogated by co-treatment with HNK (30 μmol/L). Further studies demonstrated that expression level of c-FLIP was highly correlated with the movement and migration of NSCLC cells, and the downstream effectors of c-FLIP signaling were NF-κB signaling and N-cadherin/snail signaling, while Smad signaling might lie upstream of c-FLIP.

CONCLUSION

HNK inhibits EMT-mediated motility and migration of human NSCLC cells in vitro by targeting c-FLIP, which can be utilized as a promising target for cancer therapy, while HNK may become a potential anti-metastasis drug or lead compound.

Hypericin-mediated photodynamic therapy induces apoptosis in K562 human leukemia cells through JNK pathway modulation

Hypericin (Hyp) is traditionally used as an antidepressant and antiviral agent. It selectively accumulates in spheroids and is also used as a photosensitizer in the photodynamic therapy of cancer. The present study aimed to investigate the cytotoxic effect of Hyp-mediated photodynamic therapy (Hyp-PDT) on cell growth and apoptosis of K562 leukemia cells, and to examine the underlying mechanisms. Hyp-PDT was performed with different light intensities (0.1, 0.3 and 0.5 mW/cm²), different concentrations of Hyp (0, 0.2, 0.4 and 0.8 µg/ml) and different durations of irradiation (0, 2, 4 and 8 min) in order to select the optimal conditions for subsequent experiments. A concentration of 0.4 µg/ml Hyp with a 5 h drug-light interval and 4 min irradiation at 0.3 mW/cm² light intensity was selected as the optimal conditions. The effects of Hyp-PDT on apoptosis were determined by detecting morphological changes under microscopy and by performing western blot analysis. The results revealed that Hyp-PDT suppressed cell viability in a light intensity-, dose- and irradiation duration-dependent manner. The expression levels of cleaved caspase-9, cleaved caspase-3 and phosphorylated-C-Jun N terminal kinase (JNK) l were significantly upregulated following Hyp-PDT. These results indicated that Hyp-PDT decreased cell viability and induced mitochondria-caspase-dependent apoptosis in the K562 cells through regulation of the JNK pathway. These findings suggest that Hyp-PDT may be developed as an effective treatment for leukemia.

Correlation between Polymorphism of TRAIL Gene and Condition of Intervertebral Disc Degeneration

Background

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has been suggested to be related with the pathogenesis and progression of osteoarticular degenerations. This study therefore aimed to investigate the relationship between the polymorphism of the TRAIL gene and the pathogenesis and severity of intervertebral disc degeneration (IDD) via detection of serum TRAIL expression levels.

Material/Methods

A total of 100 IDD patients in our hospital were recruited in the experimental group, while another cohort of 100 healthy individuals was employed as the control group. Blood samples collected from all people were quantified for TRAIL level using enzyme-linked immunosorbent assay (ELISA), in addition to allele and genotype frequency analysis via fluorescent PCR for TRAIL gene.

Results

At loci 1525 and 1529 in 3′-untranslated region (UTR) of 5^th exon of TRAIL gene, 3 different genotypes were identified: experimental group had higher frequency of 1525CG/1595CC, 1525G and 1595C alleles, compared to the control group (p<0.05). Patients under Schneiderman grade IV had significantly higher allele frequency compared to those at grade II or III. Serum TRAIL level was also higher in the experimental group compared to the control group, and in grade IV patients compared to grade II or III patients (p<0.05).

Conclusions

The G/C mutation at loci 1525/1595 of TRAIL gene may induce the progression of IDD, as the down-regulation of TRAIL can aggravate the severity of the disease.

Urokinase-type plasminogen activator receptor regulates apoptotic sensitivity of colon cancer HCT116 cell line to TRAIL via JNK-p53 pathway

The urokinase-type plasminogen activator receptor (uPAR) serves not only as an anchor for urokinase-type plasminogen activator but also participates in intracellular signal transduction events. In this study, we investigated whether uPAR could modulate TRAIL-induced apoptosis in human colon cancer cells HCT116. Using an antisense strategy, we established a stable HCT116 cell line with down-regulated uPAR. The sensitivity to TRAIL-induced apoptosis was evaluated by FACS analysis. Our results show that the inhibition of uPAR could sensitize HCT116 to TRAIL-induced apoptosis. uPAR inhibition changed the expression of mitochondrial apoptotic pathway proteins, including Bcl-2, Bax, Bid and p53, in a pro-apoptotic manner. We also found that the inhibition of uPAR down-regulated the phosphorylation of FAK, ERK and JNK. The inhibition of p53 by RNA interference rescued cells from enhanced apoptosis, thus indicating that p53 is critical for enhancing TRAIL-induced apoptosis. Furthermore, JNK, but not ERK, inhibition involved in the up-regulation of p53. JNK negatively regulated p53 protein level. Overall, our results show that uPAR inhibition can sensitize colon cancer cells HCT116 to TRAIL-induced apoptosis via active p53 and mitochondrial apoptotic pathways that JNK inhibition is involved.

Histone acetyltransferases and histone deacetylases in B- and T-cell development, physiology and malignancy

The development of B and T cells from hematopoietic precursors and the regulation of the functions of these immune cells are complex processes that involve highly regulated signaling pathways and transcriptional control. The signaling pathways and gene expression patterns that give rise to these developmental processes are coordinated, in part, by two opposing classes of broad-based enzymatic regulators: histone acetyltransferases (HATs) and histone deacetylases (HDACs). HATs and HDACs can modulate gene transcription by altering histone acetylation to modify chromatin structure, and by regulating the activity of non-histone substrates, including an array of immune-cell transcription factors. In addition to their role in normal B and T cells, dysregulation of HAT and HDAC activity is associated with a variety of B- and T-cell malignancies. In this review, we describe the roles of HATs and HDACs in normal B- and T-cell physiology, describe mutations and dysregulation of HATs and HDACs that are implicated lymphoma and leukemia, and discuss HAT and HDAC inhibitors that have been explored as treatment options for leukemias and lymphomas.

Trailing TRAIL Resistance: Novel Targets for TRAIL Sensitization in Cancer Cells

Resistance to chemotherapeutic drugs is the major hindrance in the successful cancer therapy. The tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a member of the tumor necrosis factor (TNF) family of ligands, which initiates apoptosis in cancer cells through interaction with the death receptors DR4 and DR5. TRAIL is perceived as an attractive chemotherapeutic agent as it specifically targets cancer cells while sparing the normal cells. However, TRAIL therapy has a major limitation as a large number of the cancer develop resistance toward TRAIL and escape from the destruction by the immune system. Therefore, elucidation of the molecular targets and signaling pathways responsible for TRAIL resistance is imperative for devising effective therapeutic strategies for TRAIL resistant cancers. Although, various molecular targets leading to TRAIL resistance are well-studied, recent studies have implicated that the contribution of some key cellular processes toward TRAIL resistance need to be fully elucidated. These processes primarily include aberrant protein synthesis, protein misfolding, ubiquitin regulated death receptor expression, metabolic pathways, epigenetic deregulation, and metastasis. Novel synthetic/natural compounds that could inhibit these defective cellular processes may restore the TRAIL sensitivity and combination therapies with such compounds may resensitize TRAIL resistant cancer cells toward TRAIL-induced apoptosis. In this review, we have summarized the key cellular processes associated with TRAIL resistance and their status as therapeutic targets for novel TRAIL-sensitizing agents.

Anticancer agents targeted to sirtuins

Sirtuins are nicotinamide adenine dinucleotide⁺-dependent deacetylases of which there are seven isoforms (SIRT1–7). Sirtuin activity is linked to gene expression, lifespan extension, neurodegeneration, and age-related disorders. Numerous studies have suggested that sirtuins could be of great significance with regard to both antiaging and tumorigenesis, depending on its targets in specific signaling pathways or in specific cancers. Recent studies have identified small chemical compounds that modulate sirtuins, and these modulators have enabled a greater understanding of the biological function and molecular mechanisms of sirtuins. This review highlights the possibility of sirtuins, especially SIRT1 and SIRT2, for cancer therapy targets, and focuses on the therapeutic potential of sirtuin modulators both in cancer prevention and treatment.

Amurensin G enhances the susceptibility to tumor necrosis factor-related apoptosis-inducing ligand-mediated cytotoxicity of cancer stem-like cells of HCT-15 cells

Cancer stem cells (CSCs) are resistant to radiotherapy and chemotherapy and play a significant role in cancer recurrence. Design of better treatment strategies that can eliminate or otherwise control CSC populations in tumors is necessary. In this study, the sensitivity to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced cytotoxicity and the effect of amurensin G, a novel sirtuin 1 (SIRT1) inhibitor, were examined using the CSC-enriched fraction of HCT-15 human colon cancer cells. Cancer stem cell-enriched HCT-15 colony cells were paradoxically less sensitive to doxorubicin, and more sensitive to TRAIL-induced cytotoxicity, than their parental cells. Also, CD44(+) HCT-15 cells were more susceptible to TRAIL-mediated cytotoxicity than CD44(-) HCT-15 cells, possibly due to increased levels of death receptors DR4 and DR5 as well as c-Myc, and decreased levels of c-FLIPL /S in CD44(+) cells compared with CD44(-) HCT-15 cells. The combination effect of amurensin G on TRAIL-mediated cytotoxicity was much more apparent in CD44(+) cells than in CD44(-) HCT-15 cells, and this was associated with more prominent downregulation of c-FLIP(L/S) in CD44(+) cells than in CD44(-) HCT-15 cells. These results indicate that HCT-15 colony or CD44(+) cells, which may have CSC properties, are more sensitive to TRAIL than parental or CD44(-) HCT-15 cells. Amurensin G may be effective in eliminating colon CSCs and be applicable to potentiate the sensitivity of colon CSCs to TRAIL.

Resveratrol and related stilbenes: their anti-aging and anti-angiogenic properties

Dietary stilbenes comprise a class of natural compounds that display significant biological activities of medicinal interest. Among them, their antioxidant, anti-aging and anti-angiogenesic properties are well established and subjects of numerous research endeavors. This mini-review aspires to account and present the literature reports published on research concerning various natural and synthetic stilbenes, such as trans-resveratrol. Special focus was given to most recent research findings, while the mechanisms underlying their anti-aging and anti-angiogenic effects as well as the respective signaling pathways involved were also presented and discussed.

Amurensin G induces autophagy and attenuates cellular toxicities in a rotenone model of Parkinson's disease

Although Parkinson's disease is a common neurodegenerative disorder its cause is still unknown. Recently, several reports showed that inducers of autophagy attenuate cellular toxicities in Parkinson's disease models. In this report we screened HEK293 cells that stably express GFP-LC3, a marker of autophagy, for autophagy inducers and identified amurensin G, a compound isolated from the wild grape (Vitis amurensis). Amurensin G treatment induced punctate cytoplasmic expression of GFP-LC3 and increased the expression level of endogenous LC3-II. Incubation of human dopaminergic SH-SY5Y cells with amurensin G attenuated the cellular toxicities of rotenone in a model of Parkinson's disease. Amurensin G inhibited rotenone-induced apoptosis and interfered with rotenone-induced G2/M cell cycle arrest. In addition, knockdown of beclin1, a regulator of autophagy, abolished the effect of amurensin G. These data collectively indicate that amurensin G attenuates cellular toxicities through the induction of autophagy.

While at Rome miRNA and TRAIL do whatever BCR-ABL commands to do

It is a well-acclaimed fact that proteins expressed as a consequence of oncogenic fusions, mutations or amplifications can facilitate ectopic protein-protein interactions that re-wire signal dissemination pathways, in a manner that escalates malignancy. BCR-ABL-mediated signal transduction cascades in leukemic cells are assembled and modulated by a finely controlled network of protein-protein interactions, mediated by characteristic signaling domains and their respective binding motifs. BCR-ABL functions in a cell context-specific and cell type-specific manner to integrate signals that affect uncontrolled cellular proliferation. In this review, we draw attention to the recent progress made in outlining resistance against TRAIL-mediated apoptosis and diametrically opposed roles of miRNAs in BCR-ABL-positive leukemic cells. BCR-ABL governs carcinogenesis through well-organized web of antiapoptotic proteins and over-expressed oncomirs which target death receptors and pro-apoptotic genes. Set of oncomirs which inversely correlate with expression of TRAIL via suppression of SMAD is an important dimension which is gradually gaining attention of the researchers. Contrary to this, some current findings show a new role of BCR-ABL in nucleus with spotlight on apoptosis. It seems obvious that genetic heterogeneity of leukemias poses therapeutic challenges, and pharmacological agents that target components of the cancer promoting nano-machinery still need broad experimental validation to be considered competent as a component of the therapeutic arsenal for this group of diseases. Rapidly developing technologies are empowering us to explain the molecular "nature" of a patient and/or tumor and with this integration of personalized medicine, with maximized efficacy, cost effectiveness will hopefully improve survival chances of the patient.