The receptor for the cytotoxic ligand TRAIL

ONC201 activates ER stress to inhibit the growth of triple-negative breast cancer cells

ONC201 was previously identified as a first-in-class antitumor agent and small-molecule inducer of the TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) gene that induces apoptosis in cancer cells. ONC201 has a safety profile and is currently in phase II clinical trials for the treatment of various malignancies. In the current study, we examine the effect of ONC201 on triple-negative breast cancer cells (TNBC), a subtype of breast cancer that is sensitive to TRAIL. We find that ONC201 inhibits the growth of TNBC cells including TNBC cells that have developed acquired TRAIL resistance. However, TNBC cells that have developed acquired ONC201 resistance are cross-resistant to TRAIL. Mechanistically, ONC201 triggers an integrated stress response (ISR) involving the activation of the transcription factor ATF4. Knockdown of ATF4 impairs ONC201-induced apoptosis of TNBC cells. Importantly, the activation of ATF4 is compromised in ONC201-resistant TNBC cells. Thus, our results indicate that ONC201 induces an ISR to cause TNBC cell death and suggest that TNBC patients may benefit from ONC201-based therapies.

Nanocarriers for TRAIL delivery: driving TRAIL back on track for cancer therapy

Since its initial identification, tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) has been shown to be capable of selectively inducing apoptosis in cancer cells. However, translation of the encouraging preclinical studies of this cytokine into the clinic has been restricted by its extremely short half-life, the presence of resistant cancer cell populations, and its inefficient in vivo delivery. Recently, there has been exceptional progress in developing novel formulations to increase the circulatory half-life of TRAIL and new combinations to treat cancers that are resistant to TRAIL. In particular, TRAIL-based nanotherapies offer the potential to improve the stability of TRAIL and prolong its half-life in plasma, to specifically deliver TRAIL to a particular target site, and to overcome resistance to TRAIL. The aim of this review is to provide an overview of the state-of-the art drug delivery systems that are currently being tested or developed to improve the biological attributes of TRAIL-based therapies.

CD95/Fas, Non-Apoptotic Signaling Pathways, and Kinases

Endothelial cells lining new blood vessels that develop during inflammatory disorders or cancers act as doors that either allow or block access to the tumor or inflamed organ. Recent data show that these endothelial cells in cancer tissues and inflamed tissues of lupus patients overexpress CD95L, the biological role of which is a subject of debate. The receptor CD95 (also named Fas or apoptosis antigen 1) belongs to the tumor necrosis factor (TNF) receptor superfamily. Its cognate ligand, CD95L, is implicated in immune homeostasis and immune surveillance. Because mutations of this receptor or its ligand lead to autoimmune disorders such as systemic lupus erythematosus (SLE) and cancers, CD95 and CD95L were initially thought to play a role in immune homeostasis and tumor elimination via apoptotic signaling pathways. However, recent data reveal that CD95 also evokes non-apoptotic signals, promotes inflammation, and contributes to carcinogenesis; therefore, it is difficult to dissect its apoptotic effects from its non-apoptotic effects during pathogenesis of disease. CD95L is cleaved by metalloproteases and so exists in two different forms: a transmembrane form and a soluble ligand (s-CD95L). We recently observed that the soluble ligand is overexpressed in serum from patients with triple-negative breast cancer or SLE, in whom it contributes to disease severity by activating non-apoptotic signaling pathways and promoting either metastatic dissemination or accumulation of certain T cell subsets in damaged organs. Here, we discuss the roles of CD95 in modulating immune functions via induction of mainly non-apoptotic signaling pathways.

Identification of Novel Epitopes with Agonistic Activity for the Development of Tumor Immunotherapy Targeting TRAIL-R1

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptor-1/2 (TRAIL-R1/R2), also known as death receptors, are expressed in a wide variety of tumor cells. Although TRAIL can induce cell apoptosis by engaging its cognate TRAIL-R1/R2, some tumor cells are or become resistant to TRAIL treatment. Monoclonal antibodies (mAbs) against TRAIL-R1/R2 have been developed to use as potential antitumor therapeutic agents instead of TRAIL. However, TRAIL-R1/R2-based tumor therapy has not yet been realized. We previously generated a series of fully human monoclonal antibodies against TRAIL-R1 (TR1-mAbs) that induced tumor cell apoptosis. In this study, we identified the antigenic binding sites of these TR1-mAbs and proposed two major epitopes on the extracellular domain of TRAIL-R1. The analysis revealed that the epitopes of some TR1-mAbs partially overlaps with the beginning of TRAIL-binding sites, and other epitopes are located within the TRAIL-binding region. Among these mAbs, TR1-422 and TR1-419 mAbs have two antigenic binding sites that bound to the same binding region, but they have different essential amino acid residues and binding site sizes. Furthermore, we investigated the apoptosis activity of TR1-419 and TR1-422 mAbs in the form of IgG and IgM. In contrast to the IgG-type TR1-419 and TR1-422 mAbs, which enhanced and inhibited TRAIL-induced apoptosis, respectively, both IgM-type TR1-419 and TR1-422 mAb strongly induced cell apoptosis with or without soluble TRAIL (sTRAIL). Moreover, the results showed that IgM-type TR1-419 and TR1-422 mAbs alone can sufficiently activate the extrinsic and intrinsic apoptosis signaling pathways and suppress tumor growth in vivo. Consequently, we identified two antigenic binding sites with agonistic activity, and their specific IgM-type mAbs exhibited strong cytotoxic activity in tumor cells in vitro and in vivo. Thus, these agonistic antigenic binding sites may be useful for the development of effective Ab-based drugs or Ab-based cell immunotherapy for various human solid tumors.

SAHA-induced TRAIL-sensitisation of Multiple Myeloma cells is enhanced in 3D cell culture

BACKGROUND

Multiple Myeloma (MM) is currently incurable despite many novel therapies. Tumour Necrosis Factor-Related Apoptosis-Inducing Ligand (TRAIL) is a potential anti-tumour agent although effects as a single agent are limited. In this study, we investigated whether the Histone Deacetylase (HDAC) inhibitor SAHA can enhance TRAIL-induced apoptosis and target TRAIL resistance in both suspension culture, and 3D cell culture as a model of disseminated MM lesions that form in bone.

METHODS

The effects of SAHA and/or TRAIL in 6 Multiple Myeloma cell lines were assessed in both suspension cultures and in an Alginate-based 3D cell culture model. The effect of SAHA and/or TRAIL was assessed on apoptosis by assessment of nuclear morphology using Hoechst 33342/Propidium Iodide staining. Viable cell number was assessed by CellTiter-Glo luminescence assay, Caspase-8 and -9 activities were measured by Caspase-Glo™ assay kit. TRAIL-resistant cells were generated by culture of RPMI 8226 and NCI-H929 by acute exposure to TRAIL followed by selection of TRAIL-resistant cells.

RESULTS

TRAIL significantly induced apoptosis in a dose-dependent manner in OPM-2, RPMI 8226, NCI-H929, U266, JJN-3 MM cell lines and ADC-1 plasma cell leukaemia cells. SAHA amplified TRAIL responses in all lines except OPM-2, and enhanced TRAIL responses were both via Caspase-8 and -9. SAHA treatment induced growth inhibition that further increased in the combination treatment with TRAIL in MM cells. The co-treatment of TRAIL and SAHA reduced viable cell numbers all cell lines. TRAIL responses were further potentiated by SAHA in 3D cell culture in NCI-H929, RPMI 8226 and U266 at lower TRAIL + SAHA doses than in suspension culture. However TRAIL responses in cells that had been selected for TRAIL resistance were not further enhanced by SAHA treatment.

CONCLUSIONS

SAHA is a potent sensitizer of TRAIL responses in both TRAIL sensitive and resistant cell lines, in both suspension and 3D culture, however SAHA did not sensitise TRAIL-sensitive cell populations that had been selected for TRAIL-resistance from initially TRAIL-sensitive populations. SAHA may increase TRAIL sensitivity in insensitive cells, but not in cells that have specifically been selected for acquired TRAIL-resistance.

Dual role of DR5 in death and survival signaling leads to TRAIL resistance in cancer cells

Besides its tumor-selective apoptotic activity, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) promotes pro-survival, proliferative or migratory signaling (NF-κB, PI3K/Akt, MAPK and JNK; referred to as 'non-apoptotic' cascades). Indeed, apoptosis and non-apoptotic signaling can be activated in clonal populations of cancer cells in response to treatment and, as a result, only a part of the initial cellular population dies while a fraction survives and develops resistance to TRAIL-induced apoptosis (referred to as 'fractional survival'). Notably, the molecular characterization of the protein platforms streaming into tumoricidal versus tumor-promoting cascades that control fractional survival remained elusive. Here we demonstrate that, in the context of DR4–DR5–DcR2 hetero-oligomeric complexes, a single death receptor (DR5) suffices to assemble composite plasma membrane-proximal pro-apoptotic/pro-survival platforms that propagate TRAIL signaling to both death and survival pathways in clonal populations of cancer cells. Moreover, we show that while all members of TRAIL-induced complexes support survival, none of them acted exclusively pro-apoptotic. Indeed, key apoptotic proteins as FADD and procaspase-8 were also involved in transducing non-apoptotic signaling in response to this cytokine. Collectively, this study reveals the Janus faces of DR5, and the contributions of other death complex components in fractional survival that foster the generation of resistance. Our data highlight a new level of complexity in TRAIL signaling and point to an improved therapeutic rationale in view of hitherto disappointing results.

Cell Death in the Developing Brain after Hypoxia-Ischemia

Perinatal insults such as hypoxia–ischemia induces secondary brain injury. In order to develop the next generation of neuroprotective therapies, we urgently need to understand the underlying molecular mechanisms leading to cell death. The cell death mechanisms have been shown to be quite different in the developing brain compared to that in the adult. The aim of this review is update on what cell death mechanisms that are operating particularly in the setting of the developing CNS. In response to mild stress stimuli a number of compensatory mechanisms will be activated, most often leading to cell survival. Moderate-to-severe insults trigger regulated cell death. Depending on several factors such as the metabolic situation, cell type, nature of the stress stimulus, and which intracellular organelle(s) are affected, the cell undergoes apoptosis (caspase activation) triggered by BAX dependent mitochondrial permeabilzation, necroptosis (mixed lineage kinase domain-like activation), necrosis (via opening of the mitochondrial permeability transition pore), autophagic cell death (autophagy/Na⁺, K⁺-ATPase), or parthanatos (poly(ADP-ribose) polymerase 1, apoptosis-inducing factor). Severe insults cause accidental cell death that cannot be modulated genetically or by pharmacologic means. However, accidental cell death leads to the release of factors (damage-associated molecular patterns) that initiate systemic effects, as well as inflammation and (regulated) secondary brain injury in neighboring tissue. Furthermore, if one mode of cell death is inhibited, another route may step in at least in a scenario when upstream damaging factors predominate over protective responses. The provision of alternative routes through which the cell undergoes death has to be taken into account in the hunt for novel brain protective strategies.

Macrophage Elastase Induces TRAIL-mediated Tumor Cell Death through Its Carboxy-Terminal Domain

RATIONALE

Macrophage elastase (matrix metalloproteinase [MMP]-12) is a potent protease that contributes to the lung destruction that accompanies cigarette smoking; it simultaneously inhibits lung tumor angiogenesis and metastasis by catalyzing the formation of antiangiogenic peptides. Recent studies have revealed novel nonproteolytic functions of MMP12, including antimicrobial activity through a peptide within its C-terminal domain (CTD).

OBJECTIVES

To determine whether the MMP12 CTD contributes to its antitumor activity in lung cancer.

METHODS

We used recombinant MMP12 peptide fragments, including its catalytic domain, CTD, and a 20 amino acid peptide within the CTD (SR20), in an in vitro system to delineate their effects on non-small cell lung cancer cell proliferation and apoptosis. We translated our findings to two murine models of lung cancer, including orthotopic human xenograft and Kras^LSL/G12D mouse models of lung cancer.

MEASUREMENTS AND MAIN RESULTS

We show that SR20 triggers tumor apoptosis by up-regulation of gene expression of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and its receptor, death receptor 4, sensitizing cells to an autocrine loop of TRAIL-mediated cell death. We then demonstrate the therapeutic efficacy of SR20 against two murine models of lung cancer.

CONCLUSIONS

The MMP12 CTD initiates TRAIL-mediated tumor cell death through its conserved SR20 peptide.

TRAIL regulatory receptors constrain human hepatic stellate cell apoptosis

The TRAIL pathway can mediate apoptosis of hepatic stellate cells to promote the resolution of liver fibrosis. However, TRAIL has the capacity to bind to regulatory receptors in addition to death-inducing receptors; their differential roles in liver fibrosis have not been investigated. Here we have dissected the contribution of regulatory TRAIL receptors to apoptosis resistance in primary human hepatic stellate cells (hHSC). hHSC isolated from healthy margins of liver resections from different donors expressed variable levels of TRAIL-R2/3/4 (but negligible TRAIL-R1) ex vivo and after activation. The apoptotic potential of TRAIL-R2 on hHSC was confirmed by lentiviral-mediated knockdown. A functional inhibitory role for TRAIL-R3/4 was revealed by shRNA knockdown and mAb blockade, showing that these regulatory receptors limit apoptosis of hHSC in response to both oligomerised TRAIL and NK cells. A close inverse ex vivo correlation between hHSC TRAIL-R4 expression and susceptibility to apoptosis underscored its central regulatory role. Our data provide the first demonstration of non-redundant functional roles for the regulatory TRAIL receptors (TRAIL-R3/4) in a physiological setting. The potential for these inhibitory TRAIL receptors to protect hHSC from apoptosis opens new avenues for prognostic and therapeutic approaches to the management of liver fibrosis.

Surface chemistry for cytosolic gene delivery and photothermal transgene expression by gold nanorods

Light-inducible gene regulation has great potential for remote and noninvasive control of the fate and function of target cells. One method to achieve such control is delivery of heat shock protein (HSP) promoter-driven protein expression vectors and photothermal heaters into the cells, followed by activation by illumination. In this study, we show that gold nanorods (AuNRs) functionalized with two conventional lipids, oleate and 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP), are capable of efficient transfection and quick photoactivation of the HSP promoter. Use of our AuNRs (DOTAP-AuNRs) was comparable to Lipofectamine 2000 in terms of transfection efficiency, while lower in cytotoxicity. Subsequent near-infrared laser (NIR) illumination of the cells transfected by DOTAP-AuNRs for 10 s induced time- and site-specific transgene expression without significant phototoxicity, to a degree similar to that of heating the entire culture dish for 30 min. Our mechanistic studies suggest that efficient transfection and quick photoactivation of the HSP promoter (HSP70b’) are due to the promoted endosomal escape of DOTAP-AuNRs. We propose a novel protocol for NIR-inducible, site-directed gene expression using an unprecedented complex of the three conventional components capable of both transfection and photothermal heating.

Cyclopamine sensitizes TRAIL-resistant gastric cancer cells to TRAIL-induced apoptosis via endoplasmic reticulum stress-mediated increase of death receptor 5 and survivin degradation

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is one of the most effective cancer treatments owing to its ability to selectively kill cancer cells, without affecting normal cells. However, it has been reported that several gastric cancer cells show resistance to TRAIL because of a scarcity of death receptor 5 (DR5) expressed on the cell surface. In this study, we show that cyclopamine sensitizes gastric cancer cells to TRAIL-induced apoptosis by elevating the expression of DR5. Interestingly, survivin hampers the existence of DR5 protein under normal conditions and cyclopamine decreases the expression of survivin, thus acting as a TRAIL sensitizer. Mechanistically, cyclopamine induces endoplasmic reticulum (ER) stress via reactive oxygen species (ROS) and CHOP, the last protein of the ER stress pathway and it regulates the proteasome degradation of survivin. Taken together, our results indicate that cyclopamine can be used for combination therapy in TRAIL-resistant gastric cancer cells.

Exploring the TRAILs less travelled: TRAIL in cancer biology and therapy

The discovery that the tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) can induce apoptosis of cancer cells without causing toxicity in mice has led to the in-depth study of pro-apoptotic TRAIL receptor (TRAIL-R) signalling and the development of biotherapeutic drug candidates that activate TRAIL-Rs. The outcome of clinical trials with these TRAIL-R agonists has, however, been disappointing so far. Recent evidence indicates that many cancers, in addition to being TRAIL resistant, use the endogenous TRAIL-TRAIL-R system to their own advantage. However, novel insight on two fronts - how resistance of cancer cells to TRAIL-based pro-apoptotic therapies might be overcome, and how the pro-tumorigenic effects of endogenous TRAIL might be countered - gives reasonable hope that the TRAIL system can be harnessed to treat cancer. In this Review we assess the status quo of our understanding of the biology of the TRAIL-TRAIL-R system - as well as the gaps therein - and discuss the opportunities and challenges in effectively targeting this pathway.

Preclinical evaluation of the imipridone family, analogs of clinical stage anti-cancer small molecule ONC201, reveals potent anti-cancer effects of ONC212

Anti-cancer small molecule ONC201 upregulates the integrated stress response (ISR) and acts as a dual inactivator of Akt/ERK, leading to TRAIL gene activation. ONC201 is under investigation in multiple clinical trials to treat patients with cancer. Given the unique imipridone core chemical structure of ONC201, we synthesized a series of analogs to identify additional compounds with distinct therapeutic properties. Several imipridones with a broad range of in vitro potencies were identified in an exploration of chemical derivatives. Based on in vitro potency in human cancer cell lines and lack of toxicity to normal human fibroblasts, imipridones ONC206 and ONC212 were prioritized for further study. Both analogs inhibited colony formation, and induced apoptosis and downstream signaling that involves the integrated stress response and Akt/ERK, similar to ONC201. Compared to ONC201, ONC206 demonstrated improved inhibition of cell migration while ONC212 exhibited rapid kinetics of activity. ONC212 was further tested in >1000 human cancer cell lines in vitro and evaluated for safety and anti-tumor efficacy in vivo. ONC212 exhibited broad-spectrum efficacy at nanomolar concentrations across solid tumors and hematological malignancies. Skin cancer emerged as a tumor type with improved efficacy relative to ONC201. Orally administered ONC212 displayed potent anti-tumor effects in vivo, a broad therapeutic window and a favorable PK profile. ONC212 was efficacious in vivo in BRAF V600E melanoma models that are less sensitive to ONC201. Based on these findings, ONC212 warrants further development as a drug candidate. It is clear that therapeutic utility extends beyond ONC201 to include additional imipridones.

d-Amino Acid Position Influences the Anticancer Activity of Galaxamide Analogs: An Apoptotic Mechanism Study

Galaxamide, an extract from Galaxaura filamentosa, is a cyclic pentapeptide containing five l-leucines. Due to the particular cyclic structure and the excellent anticancer activity, synthesis of Galaxamide and its analogs and their subsequent bio-applications have attracted great attention. In the present work, we synthesized six Galaxamide analogs by replacing one of the l-leucines with phenylalanine and varying the d-amino acid position. The anticancer effect of the synthesized Galaxamide analogs was tested against four in vitro human cancer cell lines, human hepatocellular cells (HepG₂), human breast cancer cell (MCF-7), human breast adenocarcinoma cells (MDA-MB-435) and a human cervical carcinoma cell line (Hela). Results showed that Galaxamide analogs with different d-amino acid positions displayed distinct anticancer potential. The Galaxamide analog containing d-amino acid at position 5 (Analog-6) presented the strongest anticancer activity. The mechanism study revealed that Analog-6 could cause the early apoptosis of HepG₂ cells by inhibiting their growth in the sub-G1 stage of the cell cycle and induce the chromatin condensation and fragmentation, which can be seen as 68% of HepG₂ cells inhibited in the sub-G1 stage. Moreover, a mitochondria-mediated pathway was found to be involved in the apoptotic process of Analog-6 on HepG₂ cells.

Journey of TRAIL from Bench to Bedside and its Potential Role in Immuno-Oncology

Induction of apoptosis in cancer cells has increasingly been the focus of many therapeutic approaches in oncology field. Since its identification as a TNF family member, TRAIL (TNF-related apoptosis-inducing ligand) paved a new path in apoptosis inducing cancer therapies. Its selective ability to activate extrinsic and intrinsic cell death pathways in cancer cells only, independently from p53 mutations responsible for conventional therapeutics resistance, spotted TRAIL as a potent cancer apoptotic agent. Many recombinant preparations of TRAIL and death receptor targeting monoclonal antibodies have been developed and being tested pre-clinically and clinically both as a single agent and in combinations. Of note, the monoclonal antibodies were not the only type of antibodies developed to target TRAIL receptors. Recent technology has brought forth several single chain variable domains (scFv) designs fused recombinantly to TRAIL as well. Also, it is becoming progressively more understandable that field of nanotechnology has revolutionized cancer diagnosis and therapy. The recent breakthroughs in materials science and protein engineering have helped considerably in strategically loading drugs into nanoparticles or conjugating drugs to their surface. In this review we aim to comprehensively highlight the molecular knowledge of TRAIL in the context of its pathway, receptors and resistance factors. We also aim to review the clinical trials that have been done using TRAIL based therapies and to review various scFv designs, the arsenal of nano-carriers and molecules available to selectively target tumor cells with TRAIL.

Improved antitumor activity of TRAIL fusion protein via formation of self-assembling nanoparticle

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has been known as a promising agent for cancer therapy due to its specific apoptosis-inducing effect on tumor cells rather than most normal cells. However, systemically delivered TRAIL suffers from a rapid clearance from the body with an extremely short half-life. Thermally responsive elastin-like polypeptides (ELPs) are a promising class of temperature sensitive biopolymers based on the structural motif found in mammalian tropoelastin and retain the advantages of polymeric drug delivery systems. We therefore expressed RGD-TRAIL fused with ELP (RGD-TRAIL-ELP) in E. coli. Purification of RGD-TRAIL-ELP was achieved by the conveniently inverse transition cycling (ITC). The purified RGD-TRAIL-ELP without any chemical conjugation was able to self-assemble into nanoparticle under physiological condition. Non-reducing SDS-PAGE results showed that trimer content of RGD-TRAIL-ELP increased 3.4-fold than RGD-TRAIL. Flow cytometry confirmed that RGD-TRAIL-ELP 3-fold enhanced apoptosis-inducing capacity than RGD-TRAIL. Single intraperitoneal injection of the RGD-TRAIL-ELP nanoparticle induced nearly complete tumor regression in the COLO-205 tumor xenograft model. Histological observation confirmed that RGD-TRAIL-ELP induced significant tumor cell apoptosis without apparent liver toxicity. These findings suggested that a great potential application of the RGD-TRAIL-ELP nanoparticle system as a safe and efficient delivery strategy for cancer therapy.

Icaritin Sensitizes Human Glioblastoma Cells to TRAIL-Induced Apoptosis

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has been considered to be one of the most promising candidates in research on treatments for cancer, because it induces apoptosis in a wide variety of cancer cells but not in most normal human cell types. However, many cells including glioblastoma (GBM) cells are resistant to TRAIL-induced apoptosis, which limits the potential application of TRAIL in cancer therapy. Icaritin, a hydrolytic product of icariin from Epimedium Genus, has been identified as a potential therapeutic and preventive agent in renal cell carcinoma and breast cancer. In this study, we investigated whether Icaritin treatment could modulate TRAIL-induced apoptosis in GBM. The effect of icaritin on TRAIL sensitivity was assessed in human GBM U87 and U373 cells. The underlying regulatory cascades were approached by biochemical and pharmacological strategies. We found that nontoxic concentration of icaritin alone had no significant effect on the level of apoptosis, but a combination treatment of TRAIL and icaritin caused a significantly more profound apoptosis. The sensitization was accompanied by c-FLIP down-regulation and inhibition of NF-κB activity. Studies have further demonstrated that silencing NF-κB alone was sufficient to down-regulate c-FLIP expression and sensitized both tested cells to TRAIL-induced apoptosis. These data suggest that icaritin sensitizes TRAIL-induced tumor cell apoptosis via suppression of NF-κB-dependent c-FLIP expression, providing in vitro evidence supporting the notion that icaritin is a potential sensitizer of TRAIL in anticancer therapy against human GBM.

Paclitaxel-loaded pluronic F127/P123 silica nanocapsules with surface conjugated rhTRAIL for targeted cancer therapy

A novel anticancer drug PFPSNT, paclitaxel (PTX)-loaded polymeric F127/P123 silica nanocapsules conjugated with TRAIL (tumor necrosis factor (TNF)-related apoptosis-inducing ligand), was designed and synthesized.

Intracellular localization of DR5 and related regulatory pathways as a mechanism of resistance to TRAIL in cancer

TNF-related apoptosis-inducing ligand (TRAIL) is a prominent cytokine capable of inducing apoptosis. It can bind to five different cognate receptors, through which diverse intracellular pathways can be activated. TRAIL's ability to preferentially kill transformed cells makes it a promising potential weapon for targeted tumor therapy. However, recognition of several resistance mechanisms to TRAIL-induced apoptosis has indicated that a thorough understanding of the details of TRAIL biology is still essential before this weapon can be confidently unleashed. Critical to this aim is revealing the functions and regulation mechanisms of TRAIL's potent death receptor DR5. Although expression and signaling mechanisms of DR5 have been extensively studied, other aspects, such as its subcellular localization, non-signaling functions, and regulation of its membrane transport, have only recently attracted attention. Here, we discuss different aspects of TRAIL/DR5 biology, with a particular emphasis on the factors that seem to influence the cell surface expression pattern of DR5, along with factors that lead to its nuclear localization. Disturbance of this balance apparently affects the sensitivity of cancer cells to TRAIL-mediated apoptosis, thus constituting an eligible target for potential new therapeutic agents.

Mitomycin C induces apoptosis in human epidural scar fibroblasts after surgical decompression for spinal cord injury

Numerous studies have shown that topical application of mitomycin C after surgical decompression effectively reduces scar adhesion. However, the underlying mechanisms remain unclear. In this study, we investigated the effect of mitomycin C on the proliferation and apoptosis of human epidural scar fibroblasts. Human epidural scar fibroblasts were treated with various concentrations of mitomycin C (1, 5, 10, 20, 40 μg/mL) for 12, 24 and 48 hours. Mitomycin C suppressed the growth of these cells in a dose- and time-dependent manner. Mitomycin C upregulated the expression levels of Fas, DR4, DR5, cleaved caspase-8/9, Bax, Bim and cleaved caspase-3 proteins, and it downregulated Bcl-2 and Bcl-xL expression. In addition, inhibitors of caspase-8 and caspase-9 (Z-IETD-FMK and Z-LEHD-FMK, respectively) did not fully inhibit mitomycin C-induced apoptosis. Furthermore, mitomycin C induced endoplasmic reticulum stress by increasing the expression of glucose-regulated protein 78, CAAT/enhancer-binding protein homologous protein (CHOP) and caspase-4 in a dose-dependent manner. Salubrinal significantly inhibited the mitomycin C-induced cell viability loss and apoptosis, and these effects were accompanied by a reduction in CHOP expression. Our results support the hypothesis that mitomycin C induces human epidural scar fibroblast apoptosis, at least in part, via the endoplasmic reticulum stress pathway.

Epigallocatechin-3-gallate Sensitizes Human 786-O Renal Cell Carcinoma Cells to TRAIL-Induced Apoptosis

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising anticancer agent. Epigallocatechin-3-gallate (EGCG) is a polyphenolic constituent of green tea. In this study, potentiating effect of EGCG on TRAIL-induced apoptosis human renal carcinoma cell line 786-O which is relatively resistant to TRAIL was examined, and the possible mechanism was investigated. Here, we show that co-treatment with EGCG and TRAIL induced significantly more profound apoptosis in 786-O cells. Treatment of 786-O cells with EGCG and TRAIL downregulated c-FLIP, Mcl-1, and Bcl-2 proteins in a caspase-dependent pathway. Moreover, we found that pretreatment with NAC markedly inhibited the expression levels of c-FLIP, Mcl-1, and Bcl-2 downregulated by the combinatory treatment, suggesting that the regulating effect of EGCG on these above apoptosis-relevant molecules was partially mediated by generation of ROS. Taken together, the present study demonstrates that EGCG sensitizes human 786-O renal cell carcinoma cells to TRAIL-induced apoptosis by downregulation of c-FLIP, Mcl-1, and Bcl-2.

CD8+ T cells of chronic HCV-infected patients express multiple negative immune checkpoints following stimulation with HCV peptides

Hepatitis C virus (HCV)-specific CD4+ and CD8+ T cells are key to successful viral clearance in HCV disease. Accumulation of exhausted HCV-specific T cells during chronic infection results in considerable loss of protective functional immune responses. The role of T-cell exhaustion in chronic HCV disease remains poorly understood. Here, we studied the frequency of HCV peptide-stimulated T cells expressing negative immune checkpoints (PD-1, CTLA-4, TRAIL, TIM-3 and BTLA) by flow cytometry, and measured the levels of Th1/Th2/Th17 cytokines secreted by T cells by a commercial Multi-Analyte ELISArray™ following in vitro stimulation of T cells using HCV peptides and phytohemagglutinin (PHA). HCV peptide-stimulated CD4+ and CD8+ T cells of chronic HCV (CHC) patients showed significant increase of CTLA-4. Furthermore, HCV peptide-stimulated CD4+ T cells of CHC patients also displayed relatively higher levels of PD-1 and TRAIL, whereas TIM-3 was up-regulated on HCV peptide-stimulated CD8+ T cells. Whereas the levels of IL-10 and TGF-β1 were significantly increased, the levels of pro-inflammatory cytokines IL-2, TNF-α, IL-17A and IL-6 were markedly decreased in the T cell cultures of CHC patients. Chronic HCV infection results in functional exhaustion of CD4+ and CD8+ T cells likely contributing to viral persistence.

Analysis of aDR5scFv with Specific Identification and Function

Death receptor 5 (DR5) can selectively induce cell death in a wide variety of tumor cells. However, at least certain versions of the recombinant soluble TRAIL (sTRAIL) or anti-DR5 monoclonal antibody (mAb) are also shown to cause apoptosis in normal cells (especially in hepatocytes), hampering its clinical use for cancer therapy. Recently, the development of small recombinant antibody fragments as high-affinity therapeutic reagents with reduced immunogenicity has come under the spotlight. A popular format of engineered recombinant antibody fragment is the single-chain fixed-variable (scFv) molecule, in which the VH and VL regions of the parental antibody are joined by a polypeptide linker. The scFv fragment retains the target specificity and antigen binding affinity of the intact antibody, whereas it can be genetically designed and produced in large quantities by ectopically expressing both VH and VL regions from a single cDNA in cells. In this study, an aDR5scFv was constructed and expressed, and it was conformed so that it could recognize and bind eDR5 specifically. The therapeutic effects on human lung adenocarcinoma cells lines 973 in vitro and in vivo were detected by MTT assay, flow cytometry, hematoxylin and eosin staining, and TUNEL assay. aDR5scFv was able to induce 973 cell apoptosis in an in vitro system. The protein expressions of caspase-3, Bax, and cytochrome c were raised, and aDR5scFv also inhibited tumor growth in mice with its effect as well as with radiotherapy. It is concluded that aDR5scFv could possibly be considered as a novel therapeutic candidate for the treatment of tumors.

Tumour-associated mesenchymal stem/stromal cells: emerging therapeutic targets

Mesenchymal stem cells, also known as mesenchymal stromal cells (MSCs), exist in many tissues and are known to actively migrate to sites of tissue injury, where they participate in wound repair. Tumours can be considered "wounds that never heal" and, in response to cues from a tumour, MSCs are continuously recruited to and become integral components of the tumour microenvironment. Recently, it has become apparent that such tumour-associated MSCs (TA-MSCs) have an active role in tumour initiation, promotion, progression and metastasis. In this Review, we discuss recent advances in our understanding of the pathogenic role of TA-MSCs in regulating the survival, proliferation, migration and drug resistance of tumour cells, as well as the influence of MSCs on the immune status of the tumour microenvironment. Moreover, we discuss therapeutic approaches that target TA-MSC upstream or downstream modulators or use MSCs as vehicles for the delivery of tumoricidal agents. It is anticipated that new insights into the functions of TA-MSCs will lead to the development of novel therapeutic strategies against tumours.

Phage-display screening identifies LMP1-binding peptides targeting the C-terminus region of the EBV oncoprotein

Latent membrane protein 1 (LMP1), a major oncoprotein of Epstein Barr Virus (EBV) is responsible for transforming B lymphocytes in vitro. LMP1 is overexpressed in several EBV-associated malignancies, and different approaches have been developed to reduce its level and accordingly its oncogenic function in tumor tissues. This study aimed to use phage display peptide library to obtain peptides which could specifically bind to the cytoplasmic region of LMP1 to prevent its interaction with signaling proteins. The LMP1 C-terminus region was produced in bacterial E. coli and used as target for the phage library panning. After 3 rounds, 20 phage clones were randomly selected and 8 showed high binding affinity to the recombinant C-terminus LMP1 protein. The most interesting candidates are the FO5 "QPTKDSSPPLRV" and NO4 "STTSPPAVPHNN" peptides since both bind the C-terminus LMP1 as showed by molecular docking. Furthermore, sequence alignment revealed that the FO5 peptide shared sequence similarity with the Death Receptor 4 which belongs to the tumor necrosis factor-related apoptosis-inducing receptor which plays key role in anti-tumor immunity.

Ultraviolet Light (UV) Regulation of the TNF Family Decoy Receptors DcR2 and DcR3 in Human Keratinocytes

Background:

Several additional members of the tumor necrosis factor (TNF) receptor family were recently identified. The existence of such receptors, which may play distinct and unique regulatory roles, suggests that complex regulatory mechanisms are involved in apoptosis.

Objective:

This study examines the expression of several members of the TNF receptor family in human keratinocytes exposed to ultraviolet B (UVB) irradiation.

Methods:

Human keratinocytes were exposed to increasing doses of UVB, total RNA was harvested, and a quantitative RNase protection assay was performed.

Results:

Decoy receptor-3 (DcR3), a nonfunctional receptor that binds to Fas ligand (FasL), was constitutively expressed at high level in keratinocytes but decreased rapidly in cells exposed to UVB. Decoy receptor-2 (DcR2), a nonfunctional receptor that binds to TNF-related apoptosis-inducing ligand (TRAIL)/APO-2L, showed the opposite expression pattern. DcR2 was undetectable in unirradiated keratinocytes and was markedly up-regulated after exposure to UVB. Although the response showed significant delays at higher UVB doses, the patterns observed for DcR3 and DcR2 were consistent in this set of experiments.

Conclusion:

We conclude that UVB regulates expression of these two TNF decoy receptors in keratinocytes. This pathway may represent a novel mechanism for regulation of apoptosis in the skin.

Autosomal Dominant Polycystic Disease is Associated with Depressed Levels of Soluble Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by multiple, large renal cysts and impaired kidney function. Although the reason for the development of kidney cysts is unknown, ADPKD is associated with cell cycle arrest and abundant apoptosis of renal tubular epithelial cells.

AIMS

We asked whether serum-soluble TNF-related apoptosis-inducing ligand (sTRAIL) might underlie ADPKD.

STUDY DESIGN

Case-control study.

METHODS

Serum sTRAIL levels were measured in 44 patients with ADPKD and 18 healthy volunteers. The human soluble TRAIL/Apo2L ELISA kit was used for the in vitro quantitative determination of sTRAIL in serum samples.

RESULTS

Mean serum sTRAIL levels were lower in patients with ADPKD as compared to the control group (446.9±103.1 and 875.9±349.6 pg/mL, p<0.001). Serum sTRAIL levels did not differ among stages of renal failure in patients with ADPKD. There was no correlation between serum sTRAIL levels and estimated glomerular filtration rate in patients with ADPKD (p>0.05).

CONCLUSION

Our results show that ADPKD patients have depressed sTRAIL levels, indicating apoptosis unrelated to the stage of chronic renal failure.

Molecular Aspects of Ultraviolet Radiation-Induced Apoptosis in the Skin

Background:

Apoptosis, or programmed cell death, is an essential physiological process that controls cell numbers during physiological processes, and eliminates abnormal cells that can potentially harm an organism.

Objective:

This review summarizes our current state of knowledge of apoptosis induction in skin by UV radiation.

Methods:

A review of the literature was undertaken focusing on cell death in the skin secondary to UV radiation.

Results:

It is evident that a number of apoptotic pathways, both intrinsic and extrinsic, are induced following exposure to damaging UV radiation.

Conclusion:

Although our understanding of the apoptotic processes is gradually increasing, many important aspects remain obscure. These include interconnections between pathways, wavelength-specific differences and cell type differences.

TRAIL-mediated killing of acute lymphoblastic leukemia by plasmacytoid dendritic cell-activated natural killer cells

Acute lymphoblastic leukemia (ALL) still frequently recurs after hematopoietic stem cell transplantation (HSCT), underscoring the need to improve the graft-versus-leukemia (GvL) effect. Natural killer (NK) cells reconstitute in the first months following HSCT when leukemia burden is at its lowest, but ALL cells have been shown to be resistant to NK cell-mediated killing. We show here that this resistance is overcome by NK cell stimulation with TLR-9-activated plasmacytoid dendritic cells (pDCs). NK cell priming with activated pDCs resulted in TRAIL and CD69 up-regulation on NK cells and IFN-γ production. NK cell activation was dependent on IFN-α produced by pDCs, but was not reproduced by IFN-α alone. ALL killing was further enhanced by inhibition of KIR engagement. We showed that ALL lysis was mainly mediated by TRAIL engagement, while the release of cytolytic granules was involved when ALL expressed NK cell activating receptor ligands. Finally, adoptive transfers of activated-pDCs in ALL-bearing humanized mice delayed the leukemia onset and cure 30% of mice. Our data therefore demonstrate that TLR-9 activated pDCs are a powerful tool to overcome ALL resistance to NK cell-mediated killing and to reinforce the GvL effect of HSCT. These results open new therapeutic avenues to prevent relapse in children with ALL.

Ginsenoside compound K sensitizes human colon cancer cells to TRAIL-induced apoptosis via autophagy-dependent and -independent DR5 upregulation

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a potent cancer cell-specific apoptosis-inducing cytokine with little toxicity to most normal cells. However, acquired resistance of cancer cells to TRAIL is a roadblock. Agents that can either potentiate the effect of TRAIL or overcome resistance to TRAIL are urgently needed. This article reports that ginsenoside compound K (CK) potentiates TRAIL-induced apoptosis in HCT116 colon cancer cells and sensitizes TRAIL-resistant colon cancer HT-29 cells to TRAIL. On a cellular mechanistic level, CK downregulated cell survival proteins including Mcl-1, Bcl-2, surviving, X-linked inhibitor of apoptosis protein and Fas-associated death domain-like IL-1-converting enzyme-inhibitory protein, upregulated cell pro-apoptotic proteins including Bax, tBid and cytochrome c, and induced the cell surface expression of TRAIL death receptor DR5. Reduction of DR5 levels by siRNAs significantly decreases CK- and TRAIL-mediated apoptosis. Importantly, our results indicate, for the first time, that DR5 upregulation is mediated by autophagy, as blockade of CK-induced autophagy by 3-MA, LY294002 or Atg7 siRNAs substantially decreases DR5 upregulation and reduces the synergistic effect. Furthermore, CK-stimulated autophagy is mediated by the reactive oxygen species–c-Jun NH2-terminal kinase pathway. Moreover, we found that p53 and the C/EBP homologous (CHOP) protein is also required for DR5 upregulation but not related with autophagy. Our findings contribute significantly to the understanding of the mechanism accounted for the synergistic anticancer activity of CK and TRAIL, and showed a novel mechanism related with DR5 upregulation.

Effect of vitamin E succinate on the expression of the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptor in gastric cancer cells and CD4(+) T cells

Gastric malignancy, which shows poor prognosis, is one of the most frequent causes of cancer-associated deaths. Vitamin E succinate (VES) inhibits cell proliferation and induces apoptosis in a concentration- and time-dependent manner. We explored the effect of VES on the expression of the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptor in gastric cancer cells and CD4(+) T cells. On one hand, VES dose-dependently regulated the expression of the TRAIL receptor in gastric cancer cells. Moreover, the activation of the TRAIL receptor, death receptor 4 (DR4), and death receptor 5 (DR5) in gastric cancer cells increased for up to 12 h. On the other hand, the expression of TRAIL protein in human CD4(+) T cells was obviously upregulated in the presence of VES. On the basis of these findings, we combined VES and human CD4(+) T cells to induce apoptosis of MKN28 human gastric cancer cells. The results showed that VES induced higher gastric cancer cell apoptosis when combined with human CD4(+) T cells than when applied alone. We conclude that VES can induce the expression of TRAIL receptor in gastric cancer cells, as well as the expression of TRAIL in CD4(+) T cells. Overall, our results provide a theoretical basis for future immunotherapy studies.

Osteoprotegerin: A novel biomarker for inflammatory bowel disease and gastrointestinal carcinoma

Osteoprotegerin (OPG) is a member of the tumor necrosis factor receptor superfamily of proteins. Although initial data illustrated the key role that OPG plays in bone turnover, numerous recent reports indicate that OPG is also an important factor in inflammatory pathways and tumor cell survival. OPG contributes directly to inflammatory processes and has been evaluated as a novel non-invasive biomarker of gut inflammation. Furthermore, OPG affects cell turn-over, differentiation, death, and survival via extracellular pathways, correlating with worse prognosis in inflammatory bowel diseases and several gastrointestinal carcinomas. It is now clear that OPG has multiple functions and characteristics. This review gives an overview of OPG, highlights its roles in different extracellular pathways, and outlines how OPG could be used as a novel non-invasive biological marker in inflammatory bowel diseases and gastrointestinal carcinomas.

Role of nanotechnology and gene delivery systems in TRAIL-based therapies

Since its identification as a member of the tumour necrosis factor (TNF) family, TRAIL (TNF-related apoptosis-inducing ligand) has emerged as a new avenue in apoptosis-inducing cancer therapies. Its ability to circumvent the chemoresistance of conventional therapeutics and to interact with cancer stem cells (CSCs) self-renewal pathways, amplified its potential as a cancer apoptotic agent. Many recombinant preparations of this death ligand and monoclonal antibodies targeting its death receptors have been tested in monotherapy and combinational clinical trials. Gene therapy is a new approach for cancer treatment which implies viral or non-viral functional transgene induction of apoptosis in cancer cells or repair of the underlying genetic abnormality on a molecular level. The role of this approach in overcoming the traditional barriers of radiation and chemotherapeutics systemic toxicity, risk of recurrence, and metastasis made it a promising platform for cancer treatment. The recent first Food Drug Administration (FDA) approved oncolytic herpes virus for melanoma treatment brings forth the potency of the cancer gene therapy approach in the future. Many gene delivery systems have been studied for intratumoural TRAIL gene delivery alone or in combination with chemotherapeutic agents to produce synergistic cancer cytotoxicity. However, there still remain many obstacles to be conquered for this different gene delivery systems. Nanomedicine on the other hand offers a new frontier for clinical trials and biomedical research. The FDA approved nanodrugs motivates horizon exploration for other nanoscale designed particles’ implications in gene delivery. In this review we aim to highlight the molecular role of TRAIL in apoptosis and interaction with cancer stem cells (CSCs) self-renewal pathways. Finally, we also aim to discuss the different roles of gene delivery systems, mesenchymal cells, and nanotechnology designs in TRAIL gene delivery.

A pathogenic role for tumor necrosis factor-related apoptosis-inducing ligand in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a life-threatening inflammatory respiratory disorder, often induced by cigarette smoke (CS) exposure. The development of effective therapies is impaired by a lack of understanding of the underlining mechanisms. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a cytokine with inflammatory and apoptotic properties. We interrogated a mouse model of CS-induced experimental COPD and human tissues to identify a novel role for TRAIL in COPD pathogenesis. CS exposure of wild-type mice increased TRAIL and its receptor messenger RNA (mRNA) expression and protein levels, as well as the number of TRAIL(+)CD11b(+) monocytes in the lung. TRAIL and its receptor mRNA were also increased in human COPD. CS-exposed TRAIL-deficient mice had decreased pulmonary inflammation, pro-inflammatory mediators, emphysema-like alveolar enlargement, and improved lung function. TRAIL-deficient mice also developed spontaneous small airway changes with increased epithelial cell thickness and collagen deposition, independent of CS exposure. Importantly, therapeutic neutralization of TRAIL, after the establishment of early-stage experimental COPD, reduced pulmonary inflammation, emphysema-like alveolar enlargement, and small airway changes. These data provide further evidence for TRAIL being a pivotal inflammatory factor in respiratory diseases, and the first preclinical evidence to suggest that therapeutic agents that target TRAIL may be effective in COPD therapy.

Androgen-induced Long Noncoding RNA (lncRNA) SOCS2-AS1 Promotes Cell Growth and Inhibits Apoptosis in Prostate Cancer Cells

Long noncoding RNAs (lncRNA) have been associated with the development of cancer. However, the interplay between lncRNAs and androgen receptor (AR) signaling in prostate cancer is still unclear. Here, we identified lncRNAs induced by androgen in AR-positive prostate cancer cells, where induction was abolished by AR knockdown as well as an anti-androgen, bicalutamide. By combining these data, we identified an androgen-regulated lncRNA, suppressor of cytokine signaling 2-antisense transcript 1 (SOCS2-AS1), the expression of which was higher in castration-resistant prostate cancer model cells, i.e long-term androgen-deprived (LTAD) cells, than in parental androgen-dependent LNCaP cells. SOCS2-AS1 promoted castration-resistant and androgen-dependent cell growth. We found that SOCS2-AS1 knockdown up-regulated genes related to the apoptosis pathway, including tumor necrosis factor superfamily 10 (TNFSF10), and sensitized prostate cancer cells to docetaxel treatment. Moreover, we also demonstrated that SOCS2-AS1 promotes androgen signaling by modulating the epigenetic control for AR target genes including TNFSF10 These findings suggest that SOCS2-AS1 plays an important role in the development of castration-resistant prostate cancer by repressing apoptosis.

Systemically administered AAV9-sTRAIL combats invasive glioblastoma in a patient-derived orthotopic xenograft model

Adeno-associated virus (AAV) vectors expressing tumoricidal genes injected directly into brain tumors have shown some promise, however, invasive tumor cells are relatively unaffected. Systemic injection of AAV9 vectors provides widespread delivery to the brain and potentially the tumor/microenvironment. Here we assessed AAV9 for potential glioblastoma therapy using two different promoters driving the expression of the secreted anti-cancer agent sTRAIL as a transgene model; the ubiquitously active chicken β-actin (CBA) promoter and the neuron-specific enolase (NSE) promoter to restrict expression in brain. Intravenous injection of AAV9 vectors encoding a bioluminescent reporter showed similar distribution patterns, although the NSE promoter yielded 100-fold lower expression in the abdomen (liver), with the brain-to-liver expression ratio remaining the same. The main cell types targeted by the CBA promoter were astrocytes, neurons and endothelial cells, while expression by NSE promoter mostly occurred in neurons. Intravenous administration of either AAV9-CBA-sTRAIL or AAV9-NSE-sTRAIL vectors to mice bearing intracranial patient-derived glioblastoma xenografts led to a slower tumor growth and significantly increased survival, with the CBA promoter having higher efficacy. To our knowledge, this is the first report showing the potential of systemic injection of AAV9 vector encoding a therapeutic gene for the treatment of brain tumors.

Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand-Induced Apoptosis in Prostate Cancer Cells after Treatment with Xanthohumol-A Natural Compound Present in Humulus lupulus L

TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) is an endogenous ligand, which plays role in immune surveillance and anti-tumor immunity. It has ability to selectively kill tumor cells showing no toxicity to normal cells. We tested the apoptotic and cytotoxic activities of xanthohumol, a prenylated chalcone found in Humulus lupulus on androgen-sensitive human prostate adenocarcinoma cells (LNCaP) in combination with TRAIL. Cytotoxicity was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide tetrazolium reduction assay (MTT) and lactate dehydrogenase assay (LDH). The expression of death receptors (DR4/TRAIL-R1 and DR5/TRAIL-R2) and apoptosis were detected using flow cytometry. We examined mitochondrial membrane potential (ΔΨm) by DePsipher reagent using fluorescence microscopy. The intracellular expression of proteins was evaluated by Western blotting. Our study showed that xanthohumol enhanced cytotoxic and apoptotic effects of TRAIL. The tested compounds activated caspases-3, -8, -9, Bid, and increased the expression of Bax. They also decreased expression of Bcl-xL and decreased mitochondrial membrane potential, while the expression of death receptors was not changed. The findings suggest that xanthohumol is a compound of potential use in chemoprevention of prostate cancer due to its sensitization of cancer cells to TRAIL-mediated apoptosis.

Non-viral nucleic acid containing nanoparticles as cancer therapeutics

INTRODUCTION

The delivery of nucleic acids such as DNA and short interfering RNA (siRNA) is promising for the treatment of many diseases, including cancer, by enabling novel biological mechanisms of action. Non-viral nanoparticles are a promising class of nucleic acid carriers that can be designed to be safer and more versatile than traditional viral vectors.

AREAS COVERED

In this review, recent advances in the intracellular delivery of DNA and siRNA are described with a focus on non-viral nanoparticle-based delivery methods. Material properties that have enabled successful delivery are discussed as well as applications that have directly been applied to cancer therapy. Strategies to co-deliver different nucleic acids are highlighted, as are novel targets for nucleic acid co-delivery.

EXPERT OPINION

The treatment of complex genetically-based diseases such as cancer can be enabled by safe and effective intracellular delivery of multiple nucleic acids. Non-viral nanoparticles can be fabricated to deliver multiple nucleic acids to the same cell simultaneously to prevent tumor cells from easily compensating for the knockdown or overexpression of one genetic target. The continued innovation of new therapeutic modalities and non-viral nanotechnologies to provide target-specific and personalized forms of gene therapy hold promise for genetic medicine to treat diseases like cancer in the clinic.

Proteasome inhibitor MG132 potentiates TRAIL-induced apoptosis in gallbladder carcinoma GBC-SD cells via DR5-dependent pathway

TRAIL is a tumor-selective apoptosis-inducing cytokine playing a vital role in the surveillance and elimination of some tumor cells. However, some tumors are resistant to TRAIL treatment. Proteasome inhibitor MG132 exhibits anti-proliferative and pro-apoptotic properties in many tumors. In this study, we demonstrated that proteasome inhibitor MG132 in vitro and in vivo potentiates TRAIL-induced apoptosis in gallbladder carcinoma GBC-SD cells. MG132 was able to inhibit the proliferation of GBC-SD cells and induce apoptosis in a dose-dependent manner. The induction of apoptosis by proteasome inhibitor MG132 was mainly through the extrinsic apoptotic pathways of caspase activation such as caspase-8, caspase-3 and PARP cleavage. In addition, this process was also dependent on the upregulation of death receptor 5 (DR5), which promoted TRAIL-induced apoptosis in GBC-SD cells. Taken together, these findings indicate that MG132 possesses anti-gallbladder cancer potential that correlate with regulation of DR5-dependent pathway, and suggest that MG132 may be a promising agent for sensitizing GBC-SD cells to TRAIL-induced apoptosis.