PI-3K/Akt and NF-kappaB/IkappaBalpha pathways are activated in Jurkat T cells in response to TRAIL treatment

Metformin induces apoptosis in TRAIL-resistant colorectal cancer cells

Resistance to chemotherapy drugs, which commonly occurs during the treatment of colorectal cancer (CRC), can lead to tumor recurrence and metastasis, so combinational treatment strategies according to the cancer cell type are urgently needed to overcome drug resistance and increase therapeutic efficiency. To this end, the tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a promising anticancer strategy. Some CRC cell lines such as SW620 have low sensitivity to TRAIL, so additional sensitizers are required to make the strategy effective. Therefore, we focused on the apoptotic effect of combinational metformin and TRAIL treatment on TRAIL-resistant SW620 cells. Treatment with TRAIL alone did not induce apoptosis whereas combined treatment with metformin and TRAIL significantly increased it. TRAIL activated caspases through an extrinsic pathway but increased resistance to apoptosis through the protein kinase B or AKT (PKB/AKT)/mammalian target of rapamycin (mTOR) pathway. On the other hand, metformin reduced the inhibitory effect of X-linked inhibitor of apoptosis (XIAP) by blocking the AKT and nuclear factor kappa B (NF-κB) pathways and activated CCAAT-enhancer-binding protein homologous protein (CHOP) via endoplasmic reticulum (ER) stress but without inducing apoptosis. In addition, metformin induced cell-cycle arrest, thereby blocking cell proliferation and growth. These results were also confirmed through an in vivo mouse xenograft CRC model, in which combined treatment with metformin and TRAIL induced tumor cell death, thus demonstrating the anticancer effect of their coadministration. Therefore, cotreatment of metformin and TRAIL could be an effective anticancer treatment strategy for TRAIL-resistant CRC.

TRAIL/DR5 pathway promotes AKT phosphorylation, skeletal muscle differentiation, and glucose uptake

TNF-related apoptosis-inducing ligand (TRAIL) is a protein that induces apoptosis in cancer cells but not in normal ones, where its effects remain to be fully understood. Previous studies have shown that in high-fat diet (HFD)-fed mice, TRAIL treatment reduced body weight gain, insulin resistance, and inflammation. TRAIL was also able to increase skeletal muscle free fatty acid oxidation. The aim of the present work was to evaluate TRAIL actions on skeletal muscle. Our in vitro data on C2C12 cells showed that TRAIL treatment significantly increased myogenin and MyHC and other hallmarks of myogenic differentiation, which were reduced by Dr5 (TRAIL receptor) silencing. In addition, TRAIL treatment significantly increased AKT phosphorylation, which was reduced by Dr5 silencing, as well as glucose uptake (alone and in combination with insulin). Our in vivo data showed that TRAIL increased myofiber size in HFD-fed mice as well as in db/db mice. This was associated with increased myogenin and PCG1α expression. In conclusion, TRAIL/DR5 pathway promotes AKT phosphorylation, skeletal muscle differentiation, and glucose uptake. These data shed light onto a pathway that might hold therapeutic potential not only for the metabolic disturbances but also for the muscle mass loss that are associated with diabetes.

TRAIL-receptor 2-a novel negative regulator of p53

TNF-related apoptosis-inducing ligand (TRAIL) receptor 2 (TRAIL-R2) can induce apoptosis in cancer cells upon crosslinking by TRAIL. However, TRAIL-R2 is highly expressed by many cancers suggesting pro-tumor functions. Indeed, TRAIL/TRAIL-R2 also activate pro-inflammatory pathways enhancing tumor cell invasion, migration, and proliferation. In addition, nuclear TRAIL-R2 (nTRAIL-R2) promotes malignancy by inhibiting miRNA let-7-maturation. Here, we show that TRAIL-R2 interacts with the tumor suppressor protein p53 in the nucleus, assigning a novel pro-tumor function to TRAIL-R2. Knockdown of TRAIL-R2 in p53 wild-type cells increases the half-life of p53 and the expression of its target genes, whereas its re-expression decreases p53 protein levels. Interestingly, TRAIL-R2 also interacts with promyelocytic leukemia protein (PML), a major regulator of p53 stability. PML-nuclear bodies are also the main sites of TRAIL-R2/p53 co-localization. Notably, knockdown or destruction of PML abolishes the TRAIL-R2-mediated regulation of p53 levels. In summary, our finding that nTRAIL-R2 facilitates p53 degradation and thereby negatively regulates p53 target gene expression provides insight into an oncogenic role of TRAIL-R2 in tumorigenesis that particularly manifests in p53 wild-type tumors.

The immune system on the TRAIL of Alzheimer's disease

Alzheimer's disease (AD) is the most common form of dementia, characterized by progressive degeneration and loss of neurons in specific regions of the central nervous system. Chronic activation of the immune cells resident in the brain, peripheral immune cell trafficking across the blood-brain barrier, and release of inflammatory and neurotoxic factors, appear critical contributors of the neuroinflammatory response that drives the progression of neurodegenerative processes in AD. As the neuro-immune network is impaired in course of AD, this review is aimed to point out the essential supportive role of innate and adaptive immune response either in normal brain as well as in brain recovery from injury. Since a fine-tuning of the immune response appears crucial to ensure proper nervous system functioning, we focused on the role of the TNF superfamily member, TNF-related apoptosis-inducing ligand (TRAIL), which modulates both the innate and adaptive immune response in the pathogenesis of several immunological disorders and, in particular, in AD-related neuroinflammation. We here summarized mounting evidence of potential involvement of TRAIL signaling in AD pathogenesis, with the aim to provide clearer insights about potential novel therapeutic approaches in AD.

Non-apoptotic TRAIL function modulates NK cell activity during viral infection

The role of death receptor signaling for pathogen control and infection-associated pathogenesis is multifaceted and controversial. Here, we show that during viral infection, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) modulates NK cell activity independently of its pro-apoptotic function. In mice infected with lymphocytic choriomeningitis virus (LCMV), Trail deficiency led to improved specific CD8+ T-cell responses, resulting in faster pathogen clearance and reduced liver pathology. Depletion experiments indicated that this effect was mediated by NK cells. Mechanistically, TRAIL expressed by immune cells positively and dose-dependently modulates IL-15 signaling-induced granzyme B production in NK cells, leading to enhanced NK cell-mediated T cell killing. TRAIL also regulates the signaling downstream of IL-15 receptor in human NK cells. In addition, TRAIL restricts NK1.1-triggered IFNγ production by NK cells. Our study reveals a hitherto unappreciated immunoregulatory role of TRAIL signaling on NK cells for the granzyme B-dependent elimination of antiviral T cells.

TRAIL-induced variation of cell signaling states provides nonheritable resistance to apoptosis

TNFα-related apoptosis-inducing ligand (TRAIL), specifically initiates programmed cell death, but often fails to eradicate all cells, making it an ineffective therapy for cancer. This fractional killing is linked to cellular variation that bulk assays cannot capture. Here, we quantify the diversity in cellular signaling responses to TRAIL, linking it to apoptotic frequency across numerous cell systems with single-cell mass cytometry (CyTOF). Although all cells respond to TRAIL, a variable fraction persists without apoptotic progression. This cell-specific behavior is nonheritable where both the TRAIL-induced signaling responses and frequency of apoptotic resistance remain unaffected by prior exposure. The diversity of signaling states upon exposure is correlated to TRAIL resistance. Concomitantly, constricting the variation in signaling response with kinase inhibitors proportionally decreases TRAIL resistance. Simultaneously, TRAIL-induced de novo translation in resistant cells, when blocked by cycloheximide, abrogated all TRAIL resistance. This work highlights how cell signaling diversity, and subsequent translation response, relates to nonheritable fractional escape from TRAIL-induced apoptosis. This refined view of TRAIL resistance provides new avenues to study death ligands in general.

TRAIL Induces Nuclear Translocation and Chromatin Localization of TRAIL Death Receptors

Binding of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) to the plasma membrane TRAIL-R1/-R2 selectively kills tumor cells. This discovery led to evaluation of TRAIL-R1/-R2 as targets for anti-cancer therapy, yet the corresponding clinical trials were disappointing. Meanwhile, it emerged that many cancer cells are TRAIL-resistant and that TRAIL-R1/-R2-triggering may lead to tumor-promoting effects. Intriguingly, recent studies uncovered specific functions of long ignored intracellular TRAIL-R1/-R2, with tumor-promoting functions of nuclear (n)TRAIL-R2 as the regulator of let-7-maturation. As nuclear trafficking of TRAIL-Rs is not well understood, we addressed this issue in our present study. Cell surface biotinylation and tracking of biotinylated proteins in intracellular compartments revealed that nTRAIL-Rs originate from the plasma membrane. Nuclear TRAIL-Rs-trafficking is a fast process, requiring clathrin-dependent endocytosis and it is TRAIL-dependent. Immunoprecipitation and immunofluorescence approaches revealed an interaction of nTRAIL-R2 with the nucleo-cytoplasmic shuttle protein Exportin-1/CRM-1. Mutation of a putative nuclear export sequence (NES) in TRAIL-R2 or the inhibition of CRM-1 by Leptomycin-B resulted in the nuclear accumulation of TRAIL-R2. In addition, TRAIL-R1 and TRAIL-R2 constitutively localize to chromatin, which is strongly enhanced by TRAIL-treatment. Our data highlight the novel role for surface-activated TRAIL-Rs by direct trafficking and signaling into the nucleus, a previously unknown signaling principle for cell surface receptors that belong to the TNF-superfamily.

The Hepatic Microenvironment and TRAIL-R2 Impact Outgrowth of Liver Metastases in Pancreatic Cancer after Surgical Resection

Most patients with pancreatic ductal adenocarcinoma (PDAC) undergoing curative resection relapse within months, often with liver metastases. The hepatic microenvironment determines induction and reversal of dormancy during metastasis. Both tumor growth and metastasis depend on the Tumor necrosis factor (TNF)-related apoptosis-inducing ligand-receptor 2 (TRAIL-R2). This study investigated the interplay of TRAIL-R2 and the hepatic microenvironment in liver metastases formation and the impact of surgical resection. Although TRAIL-R2-knockdown (PancTu-I shTR2) decreased local relapses and number of macroscopic liver metastases after primary tumor resection in an orthotopic PDAC model, the number of micrometastases was increased. Moreover, abdominal surgery induced liver inflammation involving activation of hepatic stellate cells (HSCs) into hepatic myofibroblasts (HMFs). In coculture with HSCs, proliferation of PancTu-I shTR2 cells was significantly lower compared to PancTu-I shCtrl cells, an effect still observed after switching coculture from HSC to HMF, mimicking surgery-mediated liver inflammation and enhancing cell proliferation. CXCL-8/IL-8 blockade diminished HSC-mediated growth inhibition in PancTu-I shTR2 cells, while Vascular Endothelial Growth Factor (VEGF) neutralization decreased HMF-mediated proliferation. Overall, this study points to an important role of TRAIL-R2 in PDAC cells in the interplay with the hepatic microenvironment during metastasis. Resection of primary PDAC seems to induce liver inflammation, which might contribute to outgrowth of liver metastases.

TRAIL, OPG, and TWEAK in kidney disease: biomarkers or therapeutic targets?

Ligands and receptors of the tumor necrosis factor (TNF) superfamily regulate immune responses and homeostatic functions with potential diagnostic and therapeutic implications. Kidney disease represents a global public health problem, whose prevalence is rising worldwide, due to the aging of the population and the increasing prevalence of diabetes, hypertension, obesity, and immune disorders. In addition, chronic kidney disease is an independent risk factor for the development of cardiovascular disease, which further increases kidney-related morbidity and mortality. Recently, it has been shown that some TNF superfamily members are actively implicated in renal pathophysiology. These members include TNF-related apoptosis-inducing ligand (TRAIL), its decoy receptor osteoprotegerin (OPG), and TNF-like weaker inducer of apoptosis (TWEAK). All of them have shown the ability to activate crucial pathways involved in kidney disease development and progression (e.g. canonical and non-canonical pathways of the transcription factor nuclear factor-kappa B), as well as the ability to regulate cell proliferation, differentiation, apoptosis, necrosis, inflammation, angiogenesis, and fibrosis with double-edged effects depending on the type and stage of kidney injury. Here we will review the actions of TRAIL, OPG, and TWEAK on diabetic and non-diabetic kidney disease, in order to provide insights into their full clinical potential as biomarkers and/or therapeutic options against kidney disease.

Impact of p53 status on TRAIL-mediated apoptotic and non-apoptotic signaling in cancer cells

Due to their ability to preferentially induce cell death in tumor cells, while sparing healthy cells, TNF-related apoptosis-inducing ligand (TRAIL) and agonistic anti-TRAIL-R1 or anti-TRAIL-R2-specific antibodies are under clinical investigations for cancer-treatment. However, TRAIL-Rs may also induce signaling pathways, which result in malignant progression. TRAIL receptors are transcriptionally upregulated via wild-type p53 following radio- or chemotherapy. Nevertheless, the impact of p53 status on the expression and signaling of TRAIL-Rs is not fully understood. Therefore, we analyzed side by side apoptotic and non-apoptotic signaling induced by TRAIL or the agonistic TRAIL-R-specific antibodies Mapatumumab (anti-TRAIL-R1) and Lexatumumab (anti-TRAIL-R2) in the two isogenic colon carcinoma cell lines HCT116 p53^+/+ and p53^-/-. We found that HCT116 p53^+/+ cells were significantly more sensitive to TRAIL-R-triggering than p53^-/- cells. Similarly, A549 lung cancer cells expressing wild-type p53 were more sensitive to TRAIL-R-mediated cell death than their derivatives with knockdown of p53. Our data demonstrate that the contribution of p53 in regulating TRAIL-R-induced apoptosis does not correlate to the levels of TRAIL-Rs at the plasma membrane, but rather to p53-mediated upregulation of Bax, favouring the mitochondrial amplification loop. Consistently, stronger caspase-9 and caspase-3 activation as well as PARP-cleavage was observed following TRAIL-R-triggering in HCT116 p53^+/+ compared to HCT116 p53^-/- cells. Interestingly, HCT116 p53^+/+ cells showed also a more potent activation of non-canonical TRAIL-R-induced signal transduction pathways like JNK, p38 and ERK1/ERK2 than p53^-/- cells. Likewise, these cells induced IL-8 expression in response to TRAIL, Mapatumumab or Lexatumumab significantly stronger than p53^-/- cells. We obtained similar results in A549 cells with or without p53-knockdown and in the two isogenic colon cancer cell lines RKO p53^+/+ and p53^-/-. In both cellular systems, we could clearly demonstrate the potentiating effects of p53 on TRAIL-R-mediated IL-8 induction. In conclusion, we found that wild-type p53 increases TRAIL-R-mediated apoptosis but simultaneously augments non-apoptotic signaling.

TRAIL pathway targeting therapeutics

Introduction

Despite decades of focused research efforts, cancer remains a significant cause of morbidity and mortality. Tumor necrosis factor(TNF)-related apoptosis-inducing ligand (TRAIL) is capable of inducing cell death selectively in cancer cells while sparing normal cells.

Areas covered

In this review, the authors cover TRA therapy and strategies that have been undertaken to improve their efficacy, as well as unconventional approaches to TRAIL pathway activation including TRAIL-inducing small molecules. They also discuss mechanisms of resistance to TRAIL and the use of combination strategies to overcome it.

Expert commentary

Targeting the TRAIL pathway has been of interest in oncology, and although initial clinical trials of TRAIL receptor agonists (TRAs) showed limitations, novel approaches represent the future of TRAIL-based therapy.

Functional TRAIL receptors in monocytes and tumor-associated macrophages: A possible targeting pathway in the tumor microenvironment

Despite the accepted dogma that TRAIL kills only tumor cells and spares normal ones, we show in this study that mononuclear phagocytes are susceptible to recombinant TRAIL via caspase-dependent apoptosis. Human resting monocytes and in vitro-differentiated macrophages expressed substantial levels of the functional TRAIL receptors (TRAIL-R1 and TRAIL-R2), while neutrophils and lymphocytes mostly expressed the non-signaling decoy receptor (TRAIL-R3). Accordingly, exclusively monocytes and macrophages activated caspase-8 and underwent apoptosis upon recombinant TRAIL treatment. TRAIL-Rs were up-regulated by anti-inflammatory agents (IL-10, glucocorticoids) and by natural compounds (Apigenin, Quercetin, Palmitate) and their treatment resulted in increased TRAIL-induced apoptosis. In mice, the only signaling TRAIL-R (DR5) was preferentially expressed by blood monocytes rather than neutrophils or lymphocytes. In both mice and humans, Tumor-Associated Macrophages (TAM) expressed functional TRAIL-R, while resident macrophages in normal tissues did not. As a proof of principle, we treated mice bearing a murine TRAIL-resistant fibrosarcoma with recombinant TRAIL. We observed significant decrease of circulating monocytes and infiltrating TAM, as well as reduced tumor growth and lower metastasis formation. Overall, these findings demonstrate that human and murine monocytes/macrophages are, among leukocytes, uniquely susceptible to TRAIL-mediated killing. This differential susceptibility to TRAIL could be exploited to selectively target macrophages in tumors.

MiR-942 decreased before 20 weeks gestation in women with preeclampsia and was associated with the pathophysiology of preeclampsia in vitro

OBJECTIVE

To investigate the possible relationship between miR-942 levels and the pathogenesis of preeclampsia using in vitro assays and to investigate circulating miR-942 levels in the early phase of mid-of pregnancy in women who later developed preeclampsia and in women with uncomplicated pregnancies.

METHODS

Plasma samples were collected from pregnant women between 12 and 20 weeks of gestation. MiR-942 levels were determined by stem-loop real-time PCR for 26 cases who subsequently developed preeclampsia as well as for 52 controls. Bioinformatics software was used to predict the target genes of miR-942, and a dual-luciferase reporter system was utilized to validate target gene regulation. Finally, MTT proliferation assays, transwell invasion assays, and endothelial cell tube formation assays were performed to further explore the function of miR-942 using a human extravillous trophoblast cell line (TEV-1).

RESULT

Circulating miR-942 levels were significantly lower in mid-pregnancy (12-20 weeks gestation) in women who later developed preeclampsia compared with those with an uncomplicated pregnancy (p < 0.05). Endoglin (ENG) is an miR-942 target gene. MiR-942 had a sensitivity of 0.673, a specificity of 0.875, and an area under the receiver operating characteristic curve (AUC) of 0.718 [95% CI, 0.594-0.822] for the possible screening of preeclampsia. In vitro, decreased miR-942 expression decreased the invasive ability of TEV-1 cells, and inhibited the HUVEC angiogenesis assay, both effects that are similar to what is observed in preeclampsia (both p <0.05).

CONCLUSION

MiR-942 may be involved in the pathogenesis of preeclampsia via the regulation of its target gene ENG. Multicenter studies must be performed and a greater number of samples must be analyzed to ascertain whether circulating miR-942 levels can serve as a novel early diagnostic marker for preeclampsia.

Identification of the zinc finger 216 (ZNF216) in human carcinoma cells: a potential regulator of EGFR activity

Epidermal Growth Factor Receptor (EGFR), a member of the ErbB family of receptor tyrosine kinase (RTK) proteins, is aberrantly expressed or deregulated in tumors and plays pivotal roles in cancer onset and metastatic progression. ZNF216 gene has been identified as one of Immediate Early Genes (IEGs) induced by RTKs. Overexpression of ZNF216 protein sensitizes 293 cell line to TNF-α induced apoptosis. However, ZNF216 overexpression has been reported in medulloblastomas and metastatic nasopharyngeal carcinomas. Thus, the role of this protein is still not clearly understood. In this study, the inverse correlation between EGFR and ZNF216 expression was confirmed in various human cancer cell lines differently expressing EGFR. EGF treatment of NIH3T3 cells overexpressing both EGFR and ZNF216 (NIH3T3-EGFR/ZNF216), induced a long lasting activation of EGFR in the cytosolic fraction and an accumulation of phosphorylated EGFR (pEGFR) more in the nuclear than in the cytosolic fraction compared to NIH3T3-EGFR cells. Moreover, EGF was able to stimulate an increased expression of ZNF216 in the cytosolic compartment and its nuclear translocation in a time-dependent manner in NIH3T3-EGFR/ZNF216. A similar trend was observed in A431 cells endogenously expressing the EGFR and transfected with Znf216. The increased levels of pEGFR and ZNF216 in the nuclear fraction of NIH3T3-EGFR/ZNF216 cells were paralleled by increased levels of phospho-MAPK and phospho-Akt. Surprisingly, EGF treatment of NIH3T3-EGFR/ZNF216 cells induced a significant increase of apoptosis thus indicating that ZNF216 could sensitize cells to EGF-induced apoptosis and suggesting that it may be involved in the regulation and effects of EGFR signaling.

Redox signaling and oxidative stress: Cross talk with TNF-related apoptosis inducing ligand activity

Redox regulation plays a key role in several physiopathological contexts and free radicals, from nitric oxide and superoxide anion up to other forms of reactive oxygen species (ROS), have been demonstrated to be involved in different biological and regulatory processes. The data reported in the current literature describe a link between ROS, inflammation and programmed cell death that is attracting interest as new pathways to be explored and targeted for therapeutic purposes. In this light, there is also growing attention to the involvement of this link in the activity of the TNF-related apoptosis inducing ligand (TRAIL). TRAIL is a member of the TNF ligands super family able to mediate multiple intracellular signals, with the potential to lead to a range of biological effects in different cell types. In particular, the hallmark of TRAIL is the ability to induce selective apoptosis in transformed cells leaving normal cells almost unaffected and this feature has already opened the door to several clinical studies for cancer treatment. Moreover, TRAIL plays a role in several physiological and pathological processes of both innate and adaptive immune systems and of the cardiovascular context, with a strong clinical potential. Nonetheless, several issues still need to be clarified about the signaling mediated by TRAIL to gain deeper insight into its therapeutic potential. In this light, the aim of this review is to summarize the main preclinical evidences about the interplay between TRAIL and redox signaling, with particular emphasis to the implications in vascular physiopathology and cancer.

Clinical perspectives of TRAIL: insights into central nervous system disorders

The TNF-related apoptosis inducing ligand TRAIL is a member of the TNF superfamily that has been firstly studied and evaluated for its anti-cancer activity, and the insights into its biology have already led to the identification of several TRAIL-based anticancer strategies with strong clinical therapeutic potentials. Nonetheless, the TRAIL system is far more complex and it can lead to a wider range of biological effects other than the ability of inducing apoptosis in cancer cells. By virtue of the different receptors and the different signalling pathways involved, TRAIL plays indeed a role in the regulation of different processes of the innate and adaptive immune system and this feature makes it an intriguing molecule under consideration in the development/progression/treatment of several immunological disorders. In this context, central nervous system represents a peculiar anatomic site where, despite its "status" of immune-privileged site, both innate and adaptive inflammatory responses occur and are involved in several pathological conditions. A number of studies have evaluated the role of TRAIL and of TRAIL-related pathways as pro-inflammatory or protective stimuli, depending on the specific pathological condition, confirming a twofold nature of this molecule. In this light, the aim of this review is to summarize the main preclinical evidences of the potential/involvement of TRAIL molecule and TRAIL pathways for the treatment of central nervous system disorders and the key suggestions coming from their assessment in preclinical models as proof of concept for future clinical studies.

Roles and Clinical Applications of OPG and TRAIL as Biomarkers in Cardiovascular Disease

Cardiovascular diseases (CVD) remain the major cause of death and premature disability in Western societies. Assessing the risk of CVD is an important aspect in clinical decision-making. Among the growing number of molecules that are studied for their potential utility as CVD biomarkers, a lot of attention has been focused on osteoprotegerin (OPG) and its ligands, which are receptor activator of nuclear factor κB ligand (RANKL) and TNF-related apoptosis-inducing ligand. Based on the existing literature and on our experience in this field, here we review what the possible roles of OPG and TRAIL in CVD are and their potential utility as CVD biomarkers.

Distinct roles of TNF-related apoptosis-inducing ligand (TRAIL) in viral and bacterial infections: from pathogenesis to pathogen clearance

INTRODUCTION

Apoptotic death of different cells observed during infection is thought to limit overwhelming inflammation in response to microbial challenge. However, the underlying apoptotic death mechanisms have not been well defined. Tumor necrosis factor (TNF) related apoptosis-inducing ligand (TRAIL) is a type II transmembrane protein belonging to the TNF superfamily, which is involved not only in tumor growth suppression but in infection control and also in the regulation of both innate and adaptive immune responses.

FINDINGS

In this review, we have summarized data of recent studies on the influence of the TRAIL/TRAIL receptor (TRAIL-R) system on the development of viral and bacterial infections. TRAIL may have a dual function in the immune system being able to kill infected cells and also to participate in the pathogenesis of multiple infections. Moreover, many pathogens have evolved mechanisms to manipulate TRAIL signaling thus increasing pathogen replication.

CONCLUSION

Present data highlight an essential role for the TRAIL/TRAIL-R system in the regulation and modulation of apoptosis and show that TRAIL has distinct roles in pathogenesis and pathogen elimination. Knowledge of the factors that determine whether TRAIL is helpful or harmful supposes its potential therapeutic implications that are only beginning to be explored.

Involvement of cyclic-nucleotide response element-binding family members in the radiation response of Ramos B lymphoma cells

The aim of the present study was to investigate the role of Cyclic-nucleotide Response Element-Binding (CREB) family members and related nuclear transcription factors in the radiation response of human B lymphoma cell lines (Daudi and Ramos). Unlike the more radiosensitive Daudi cells, Ramos cells demonstrated only a moderate increase in early apoptosis after 3-5 Gy irradiation doses, which was detected with Annexin V/PI staining. Moreover, a significant and dose-dependent G2/M phase accumulation was observed in the same cell line at 24 h after both ionizing radiation (IR) doses. Western blot analysis showed an early increase in CREB protein expression that was still present at 3 h and more evident after 3 Gy IR in Ramos cells, along with the dose-dependent upregulation of p53 and NF-κB. These findings were consistent with real-time RT-PCR analysis that showed an early- and dose-dependent upregulation of NFKB1, IKBKB and XIAP gene expression. Unexpectedly, pre-treatment with SN50 did not increase cell death, but cell viability. Taken together, these findings let us hypothesise that the early induction and activation of NF-κB1 in Ramos cells could mediate necrotic cell death and be linked to other molecules belonging to CREB family and involved in the cell cycle regulation.

Marine Drugs Regulating Apoptosis Induced by Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand (TRAIL)

Marine biomass diversity is a tremendous source of potential anticancer compounds. Several natural marine products have been described to restore tumor cell sensitivity to TNF-related apoptosis inducing ligand (TRAIL)-induced cell death. TRAIL is involved during tumor immune surveillance. Its selectivity for cancer cells has attracted much attention in oncology. This review aims at discussing the main mechanisms by which TRAIL signaling is regulated and presenting how marine bioactive compounds have been found, so far, to overcome TRAIL resistance in tumor cells.

Tumor Necrosis Factor Related Apoptosis Inducing Ligand (Trail) in endothelial response to biomechanical and biochemical stresses in arteries

Shear stress is determined by three physical components described in a famous triad: blood flow, blood viscosity and vessel geometry. Through the direct action on endothelium, shear stress is able to radically interfere with endothelial properties and the physiology of the vascular wall. Endothelial cells (ECs) have also to sustain biochemical stresses represented by chemokines, growth factors, cytokines, complement, hormones, nitric oxide (NO), oxygen and reactive oxygen species (ROS). Many growth factors, cytokines, chemokines, hormones, and chemical substances, like NO, act and regulate endothelium functions and homeostasis. Among these cytokines Tumor Necrosis Factor Related Apoptosis Inducing Ligand (TRAIL) has been assigned a regulatory role in ECs physiology and physiopathology. Thus, the aim of this review is to provide a general overview of the endothelial response pathways after different types of biomechanical and biochemical stress in in vitro models and to analyze the crucial role of TRAIL under pathological conditions of the cardiocirculatory system like atherosclerosis, coronary artery disease, and diabetes.

Surviving apoptosis: life-death signaling in single cells

Tissue development and homeostasis are regulated by opposing pro-survival and pro-death signals. An interesting feature of the Tumor Necrosis Factor (TNF) family of ligands is that they simultaneously activate opposing signals within a single cell via the same ligand-receptor complex. The magnitude of pro-death events such as caspase activation and pro-survival events such as Nuclear Factor (NF)-κB activation vary not only from one cell type to the next but also among individual cells of the same type due to intrinsic and extrinsic noise. The molecules involved in these pro-survival and/or pro-death pathways, and the different phenotypes that result from their activities, have been recently reviewed. Here we focus on the impact of cell-to-cell variability in the strength of these opposing signals on shaping cell fate decisions.

Potential role of circulating microRNAs as early markers of preeclampsia

OBJECTIVE

To identify microRNAs (miRNAs) differentially expressed at early stages of gestation (12-14 weeks) in the serum of pregnant women, who later developed severe preeclampsia (sPE) in the third trimester of pregnancy (n = 24) compared to women with normal pregnancy (n = 24).

MATERIALS AND METHODS

Sera from 12-14-week-gestation whole blood were subjected to microarray analysis with TaqMan Low Density Array chips (human microRNA panel V3.0), and to quantitative real-time polymerase chain reaction.

RESULTS

By using the TaqMan Low Density Array chip technology, 19 mature miRNAs appeared differentially expressed in the group of women who later developed sPE as compared to normal women. The expression of four miRNAs (miR-1233, miR-520, miR-210, miR-144) was validated by quantitative real-time polymerase chain reaction analysis. MiR-1233 was the most overexpressed in the serum of women who later developed sPE.

CONCLUSION

Circulating miRNAs deserve further investigation in order to explore their potential role in the pathogenesis of preeclampsia. In particular, miR-1233 might represent a potential marker of early sPE.

TNF-related apoptosis inducing ligand in ocular cancers and ocular diabetic complications

TNF-related apoptosis inducing ligand (TRAIL) is an intensively studied cytokine, in particular for its anticancer activity. The discovery that conjunctival sac fluid contains extremely high levels of soluble TRAIL as compared to other body fluids suggested important implications in the context of the immunological surveillance of the eye, in particular of the anterior surface. In this review, we discuss the potential physiopathologic and therapeutic role of the TRAIL/TRAIL receptor system in a variety of ocular cancers. Moreover, since an increasing amount of data has indicated the important biological activities of the TRAIL/TRAIL receptor systems also in a completely different pathologic context such as diabetes mellitus, in the second part of this review we summarize the currently available data on the involvement of TRAIL in the ocular complications of diabetes mellitus as modulator of the inflammatory and angiogenic response in the eye.

TRAIL modulates the immune system and protects against the development of diabetes

TRAIL or tumor necrosis factor (TNF) related apoptosis-inducing ligand is a member of the TNF superfamily of proteins, whose best characterized function is the induction of apoptosis in tumor, infected, or transformed cells through activation of specific receptors. In nontransformed cells, however, the actions of TRAIL are less well characterized. Recent studies suggest that TRAIL may be implicated in the development and progression of diabetes. Here we review TRAIL biological actions, its effects on the immune system, and how and to what extent it has been shown to protect against diabetes.

STAT-6 mediates TRAIL induced RANK ligand expression in stromal/preosteoblast cells

Receptor activator of nuclear factor kappa-B ligand (RANKL) is a critical osteoclastogenic factor expressed in bone marrow stromal/osteoblast lineage cells. Tumor necrosis factor (TNF) related apoptosis-inducing ligand (TRAIL) levels are elevated in pathologic conditions such as multiple myeloma and inflammatory arthritis, and have been positively correlated with osteolytic markers. Osteoprotegerin (OPG) which inhibits osteoclastogenesis is a decoy receptor for RANKL and also known to interact with TRAIL. Herein, we show that TRAIL increases DR5 and DcR1 receptors but no change in the levels of DR4 and DcR2 expression in human bone marrow derived stromal/preosteoblast (SAKA-T) cell line. We further demonstrated that TRAIL treatment significantly decreased OPG mRNA expression. Interestingly, TRAIL treatment induced RANKL mRNA expression in these cells. In addition, TRAIL significantly increased NF-kB and c-Jun N-terminal kinase (JNK) activity. Human transcription factor array screening by real-time RT-PCR identified TRAIL up-regulation of the signal transducers and activators of the transcription (STAT)-6 expression in SAKA-T cells. TRAIL stimulation induced p-STAT-6 expression in human bone marrow derived primary stromal/preosteoblast cells. Confocal microscopy analysis further revealed p-STAT-6 nuclear localization in SAKA-T cells. Chromatin immunoprecipitation (ChIP) assay confirmed p-STAT-6 binding to the hRANKL gene distal promoter region. In addition, siRNA suppression of STAT-6 expression inhibits TRAIL increased hRANKL gene promoter activity. Thus, our results suggest that TRAIL induces RANKL expression through a STAT-6 dependent transcriptional regulatory mechanism in bone marrow stromal/preosteoblast cells.

Intranasal administration of recombinant TRAIL down-regulates CXCL-1/KC in an ovalbumin-induced airway inflammation murine model

Ovalbumin (OVA)-sensitized BALB/c mice were i.n. instilled with recombinant TNF-related apoptosis inducing ligand (TRAIL) 24 hours before OVA challenge. The total number of leukocytes and the levels of the chemokine CXCL-1/KC significantly increased in the bronchoalveolar lavage (BAL) fluids of allergic animals with respect to control littermates, but not in the BAL of mice i.n. pretreated with recombinant TRAIL before OVA challenge. In particular, TRAIL pretreatment significantly reduced the BAL percentage of both eosinophils and neutrophils. On the other hand, when TRAIL was administrated simultaneously to OVA challenge its effect on BAL infiltration was attenuated. Overall, the results show that the i.n. pretreatment with TRAIL down-modulated allergic airway inflammation.

Compartmentalization of TNF-related apoptosis-inducing ligand (TRAIL) death receptor functions: emerging role of nuclear TRAIL-R2

Localized in the plasma membrane, death domain-containing TNF-related apoptosis-inducing ligand (TRAIL) receptors, TRAIL-R1 and TRAIL-R2, induce apoptosis and non-apoptotic signaling when crosslinked by the ligand TRAIL or by agonistic receptor-specific antibodies. Recently, an increasing body of evidence has accumulated that TRAIL receptors are additionally found in noncanonical intracellular locations in a wide range of cell types, preferentially cancer cells. Thus, besides their canonical locations in the plasma membrane and in intracellular membranes of the secretory pathway as well as endosomes and lysosomes, TRAIL receptors may also exist in autophagosomes, in nonmembraneous cytosolic compartment as well as in the nucleus. Such intracellular locations have been mainly regarded as hide-outs for these receptors representing a strategy for cancer cells to resist TRAIL-mediated apoptosis. Recently, a novel function of intracellular TRAIL-R2 has been revealed. When present in the nuclei of tumor cells, TRAIL-R2 inhibits the processing of the primary let-7 miRNA (pri-let-7) via interaction with accessory proteins of the Microprocessor complex. The nuclear TRAIL-R2-driven decrease in mature let-7 enhances the malignancy of cancer cells. This finding represents a new example of nuclear activity of typically plasma membrane-located cytokine and growth factor receptors. Furthermore, this extends the list of nucleic acid targets of the cell surface receptors by pri-miRNA in addition to DNA and mRNA. Here we review the diverse functions of TRAIL-R2 depending on its intracellular localization and we particularly discuss the nuclear TRAIL-R2 (nTRAIL-R2) function in the context of known nuclear activities of other normally plasma membrane-localized receptors.

Soluble TRAIL is present at high concentrations in seminal plasma and promotes spermatozoa survival

The expression of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL(TNFSF10)) and of its receptors (TRAILR1, TRAILR2, TRAILR3, and TRAILR4) have been documented in testis, but the presence of soluble TRAIL in seminal fluid, as well as the potential physiopathological role of the TRAIL/TRAILR system in spermatozoa, has not been previously investigated. Male donors (n=123) among couples presenting for infertility evaluation were consecutively enrolled in this study. The presence of soluble TRAIL was analyzed in seminal samples by ELISA, while the surface expression of TRAIL receptors was investigated by flow cytometry. High levels of soluble TRAIL were detected in seminal plasma (median, 11 621 pg/ml and mean±s.d., 13 371±8367 pg/ml) and flow cytometric analysis revealed a variable expression of TRAIL receptors in the sperm cellular fraction among different subjects. In addition, the effect of physiologically relevant concentrations of recombinant TRAIL was investigated on survival and motility of spermatozoa. Of interest, the in vitro exposure of capacitated spermatozoa to recombinant TRAIL (10 ng/ml) significantly preserved their overall survival. Therefore, the present study demonstrates for the first time the presence of elevated levels of the anti-inflammatory cytokine TRAIL in seminal fluids. Moreover, the demonstration that recombinant TRAIL promotes spermatozoa survival after capacitation suggests potential therapeutic implications.

NF-κB pathways in hematological malignancies

The nuclear factor κB or NF-κB transcription factor family plays a key role in several cellular functions, i.e. inflammation, apoptosis, cell survival, proliferation, angiogenesis, and innate and acquired immunity. The constitutive activation of NF-κB is typical of most malignancies and plays a major role in tumorigenesis. In this review, we describe NF-κB and its two pathways: the canonical pathway (RelA/p50) and the non-canonical pathway (RelB/p50 or RelB/p52). We then consider the role of the NF-κB subunits in the development and functional activity of B cells, T cells, macrophages and dendritic cells, which are the targets of hematological malignancies. The relevance of the two pathways is described in normal B and T cells and in hematological malignancies, acute and chronic leukemias (ALL, AML, CLL, CML), B lymphomas (DLBCLs, Hodgkin's lymphoma), T lymphomas (ATLL, ALCL) and multiple myeloma. We describe the interaction of NF-κB with the apoptotic pathways induced by TRAIL and the transcription factor p53. Finally, we discuss therapeutic anti-tumoral approaches as mono-therapies or combination therapies aimed to block NF-κB activity and to induce apoptosis (PARAs and Nutlin-3).

Nuclear death receptor TRAIL-R2 inhibits maturation of let-7 and promotes proliferation of pancreatic and other tumor cells

BACKGROUND & AIMS

Tumor necrosis factor-related apoptosis inducing ligand (TRAIL-R1) (TNFRSF10A) and TRAIL-R2 (TNFRSF10B) on the plasma membrane bind ligands that activate apoptotic and other signaling pathways. Cancer cells also might have TRAIL-R2 in the cytoplasm or nucleus, although little is known about its activities in these locations. We investigated the functions of nuclear TRAIL-R2 in cancer cell lines.

METHODS

Proteins that interact with TRAIL-R2 initially were identified in pancreatic cancer cells by immunoprecipitation, mass spectrometry, and immunofluorescence analyses. Findings were validated in colon, renal, lung, and breast cancer cells. Functions of TRAIL-R2 were determined from small interfering RNA knockdown, real-time polymerase chain reaction, Drosha-activity, microRNA array, proliferation, differentiation, and immunoblot experiments. We assessed the effects of TRAIL-R2 overexpression or knockdown in human pancreatic ductal adenocarcinoma (PDAC) cells and their ability to form tumors in mice. We also analyzed levels of TRAIL-R2 in sections of PDACs and non-neoplastic peritumoral ducts from patients.

RESULTS

TRAIL-R2 was found to interact with the core microprocessor components Drosha and DGCR8 and the associated regulatory proteins p68, hnRNPA1, NF45, and NF90 in nuclei of PDAC and other tumor cells. Knockdown of TRAIL-R2 increased Drosha-mediated processing of the let-7 microRNA precursor primary let-7 (resulting in increased levels of mature let-7), reduced levels of the let-7 targets (LIN28B and HMGA2), and inhibited cell proliferation. PDAC tissues from patients had higher levels of nuclear TRAIL-R2 than non-neoplastic pancreatic tissue, which correlated with increased nuclear levels of HMGA2 and poor outcomes. Knockdown of TRAIL-R2 in PDAC cells slowed their growth as orthotopic tumors in mice. Reduced nuclear levels of TRAIL-R2 in cultured pancreatic epithelial cells promoted their differentiation.

CONCLUSIONS

Nuclear TRAIL-R2 inhibits maturation of the microRNA let-7 in pancreatic cancer cell lines and increases their proliferation. Pancreatic tumor samples have increased levels of nuclear TRAIL-R2, which correlate with poor outcome of patients. These findings indicate that in the nucleus, death receptors can function as tumor promoters and might be therapeutic targets.

Small molecule sensitization to TRAIL is mediated via nuclear localization, phosphorylation and inhibition of chaperone activity of Hsp27

The small chaperone protein Hsp27 confers resistance to apoptosis, and therefore is an attractive anticancer drug target. We report here a novel mechanism underlying the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) sensitizing activity of the small molecule LY303511, an inactive analog of the phosphoinositide 3-kinase inhibitor inhibitor LY294002, in HeLa cells that are refractory to TRAIL-induced apoptosis. On the basis of the fact that LY303511 is derived from LY294002, itself derived from quercetin, and earlier findings indicating that quercetin and LY294002 affected Hsp27 expression, we investigated whether LY303511 sensitized cancer cells to TRAIL via a conserved inhibitory effect on Hsp27. We provide evidence that upon treatment with LY303511, Hsp27 is progressively sequestered in the nucleus, thus reducing its protective effect in the cytosol during the apoptotic process. LY303511-induced nuclear translocation of Hsp27 is linked to its sustained phosphorylation via activation of p38 kinase and MAPKAP kinase 2 and the inhibition of PP2A. Furthermore, Hsp27 phosphorylation leads to the subsequent dissociation of its large oligomers and a decrease in its chaperone activity, thereby further compromising the death inhibitory activity of Hsp27. Furthermore, genetic manipulation of Hsp27 expression significantly affected the TRAIL sensitizing activity of LY303511, which corroborated the Hsp27 targeting activity of LY303511. Taken together, these data indicate a novel mechanism of small molecule sensitization to TRAIL through targeting of Hsp27 functions, rather than its overall expression, leading to decreased cellular protection, which could have therapeutic implications for overcoming chemotherapy resistance in tumor cells.

Cells surviving fractional killing by TRAIL exhibit transient but sustainable resistance and inflammatory phenotypes

Cells that survive fractional killing by TRAIL or FasR agonists enter a state of resistance accompanied by inflammatory phenotypes. This state is transient, decaying over the course of several days, but can be sustained by periodic TRAIL treatments. This finding has implications for optimal dosing strategies of extrinsic cell death agents.

When clonal populations of human cells are exposed to apoptosis-inducing agents, some cells die and others survive. This fractional killing arises not from mutation but from preexisting, stochastic differences in the levels and activities of proteins regulating apoptosis. Here we examine the properties of cells that survive treatment with agonists of two distinct death receptors, tumor necrosis factor–related apoptosis-inducing ligand (TRAIL) and anti-FasR antibodies. We find that “survivor” cells are highly resistant to a second ligand dose applied 1 d later. Resistance is reversible, resetting after several days of culture in the absence of death ligand. “Reset” cells appear identical to drug-naive cells with respect to death ligand sensitivity and gene expression profiles. TRAIL survivors are cross-resistant to activators of FasR and vice versa and exhibit an NF-κB–dependent inflammatory phenotype. Remarkably, reversible resistance is induced in the absence of cell death when caspase inhibitors are present and can be sustained for 1 wk or more, also without cell death, by periodic ligand exposure. Thus stochastic differences in cell state can have sustained consequences for sen­sitivity to prodeath ligands and acquisition of proinflammatory phenotypes. The important role played by periodicity in TRAIL exposure for induction of opposing apoptosis and survival mechanisms has implications for the design of optimal therapeutic agents and protocols.

Non-canonical kinase signaling by the death ligand TRAIL in cancer cells: discord in the death receptor family

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-based therapy is currently evaluated in clinical studies as a tumor cell selective pro-apoptotic approach. However, besides activating canonical caspase-dependent apoptosis by binding to TRAIL-specific death receptors, the TRAIL ligand can activate non-canonical cell survival or proliferation pathways in resistant tumor cells through the same death receptors, which is counterproductive for therapy. Even more, recent studies indicate metastases-promoting activity of TRAIL. In this review, the remarkable dichotomy in TRAIL signaling is highlighted. An overview of the currently known mechanisms involved in non-canonical TRAIL signaling and the subsequent activation of various kinases is provided. These kinases include RIP1, IκB/ NF-κB, MAPK p38, JNK, ERK1/2, MAP3K TAK1, PKC, PI3K/Akt and Src. The functional consequences of their activation, often being stimulation of tumor cell survival and in some cases enhancement of their invasive behavior, are discussed. Interestingly, the non-canonical responses triggered by TRAIL in resistant tumor cells resemble that of TRAIL-induced signals in non-transformed cells. Better knowledge of the mechanism underlying the dichotomy in TRAIL receptor signaling may provide markers for selecting patients who will likely benefit from TRAIL-based therapy and could provide a rationalized basis for combination therapies with TRAIL death receptor-targeting drugs.

TRAIL-R4 promotes tumor growth and resistance to apoptosis in cervical carcinoma HeLa cells through AKT

Background

TRAIL/Apo2L is a pro-apoptotic ligand of the TNF family that engages the apoptotic machinery through two pro-apoptotic receptors, TRAIL-R1 and TRAIL-R2. This cell death program is tightly controlled by two antagonistic receptors, TRAIL-R3 and TRAIL-R4, both devoid of a functional death domain, an intracellular region of the receptor, required for the recruitment and the activation of initiator caspases. Upon TRAIL-binding, TRAIL-R4 forms a heteromeric complex with the agonistic receptor TRAIL-R2 leading to reduced caspase-8 activation and apoptosis.

Methodology/Principal Findings

We provide evidence that TRAIL-R4 can also exhibit, in a ligand independent manner, signaling properties in the cervical carcinoma cell line HeLa, through Akt. Ectopic expression of TRAIL-R4 in HeLa cells induced morphological changes, with cell rounding, loss of adherence and markedly enhanced cell proliferation in vitro and tumor growth in vivo. Disruption of the PI3K/Akt pathway using the pharmacological inhibitor LY294002, siRNA targeting the p85 regulatory subunit of phosphatidylinositol-3 kinase, or by PTEN over-expression, partially restored TRAIL-mediated apoptosis in these cells. Moreover, the Akt inhibitor, LY294002, restituted normal cell proliferation index in HeLa cells expressing TRAIL-R4.

Conclusions/Significance

Altogether, these results indicate that, besides its ability to directly inhibit TRAIL-induced cell death at the membrane, TRAIL-R4 can also trigger the activation of signaling pathways leading to cell survival and proliferation in HeLa cells. Our findings raise the possibility that TRAIL-R4 may contribute to cervical carcinogenesis.

c-Cbl acts as a mediator of Src-induced activation of the PI3K-Akt signal transduction pathway during TRAIL treatment

We have previously observed that TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) induces acquired TRAIL resistance by increasing Akt phosphorylation and Bcl-xL expression. In this study, we report that Src, c-Cbl, and PI3K are involved in the phosphorylation of Akt during TRAIL treatment. Data from immunoprecipitation and immunoblotting assay reveal that Src interacts with c-Cbl and PI3K. Data from immune complex kinase assay demonstrate that Src can directly phosphorylate c-Cbl and PI3K p85 subunit protein. Data from gene knockdown experiments with an RNA interference (RNAi) technique show that c-Cbl is involved in the interaction between Src and PI3K p85 during TRAIL treatment, playing an important role in TRAIL-induced Akt phosphorylation. Taken together, c-Cbl may act as a mediator to regulate the Src-PI3K-Akt signal transduction pathway during TRAIL treatment.

TRAILing death in cancer

The observation that certain types of cancer express death receptors on their cell surface has triggered heightened interest in exploring the potential of receptor ligation as a novel anti-cancer modality, and since the expression is somewhat restricted to cancer cells the therapeutic implications are very promising. One such death receptor ligand belonging to the tumor necrosis receptor (TNF) superfamily, TNF-related apoptosis-inducing ligand (TRAIL), has been in the limelight as a tumor selective molecule that transmits death signal via ligation to its receptors (TRAIL-R1 and TRAIL-R2 or death receptors 4 and 5; DR4 and DR5). Interestingly, TRAIL-induced apoptosis exhibits hallmarks of extrinsic as well as intrinsic death pathways, and, therefore, is subject to regulation both at the cell surface receptor level as well as more downstream at the post-mitochondrial level. Despite the remarkable selectivity of DR expression on cancer cell surface, development of resistance to TRAIL-induced apoptosis remains a major challenge. Therefore, unraveling the cellular and molecular mechanisms of TRAIL resistance as well as identifying strategies to overcome this problem for an effective therapeutic response remains the cornerstone of many research endeavors. This review aims at presenting an overview of the biology, function and translational relevance of TRAIL with a specific view to discussing the various regulatory mechanisms and the current trends in reverting TRAIL resistance of cancer cells with the obvious implication of an improved clinical outcome.

Oligomerized tumor necrosis factor-related apoptosis inducing ligand strongly induces cell death in myeloma cells, but also activates proinflammatory signaling pathways

The oligomerization status of soluble tumor necrosis factor-related apoptosis inducing ligand (TRAIL) trimers has an overwhelming impact on cell death induction in a cell-type dependent fashion. Thus, we evaluated the ability of single and oligomerized TRAIL trimers to induce cell death in human myeloma cells. In all myeloma cell lines analyzed, oligomerized TRAIL trimers induced caspase activation and complete cell death, whereas non-oligomerized TRAIL trimers showed no or only a modest effect. Caspase activation induced by oligomerized TRAIL was blocked in all cell lines by the pan-caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp(OMe)-fluoromethylketone (z-VAD-fmk). Cell death induction was largely blocked in two cell lines by z-VAD-fmk, but was only marginally attenuated in three other cell lines, indicating that TRAIL induces caspase-dependent and caspase-independent cell death in myeloma cells. Preceding cell death, TRAIL activated nuclear factor kappaB, c-Jun N-terminal kinase, p38 and p42/44. Although TRAIL-induced stimulation of c-Jun N-terminal kinase and p38 was caspase-dependent in a cell type-specific fashion, activation of nuclear factor kappaB and p42/44 was caspase-independent in all cases. In accordance with activation of the nuclear factor kappaB pathway, we observed transcriptional up-regulation of several well established nuclear factor kappaB target genes. Furthermore, we found that TRAIL activates proinflammatory pathways in approximately 50% of primary myeloma samples. Taken together, our data suggest (a) that oligomerized TRAIL variants are necessary to ensure maximal cell death induction in myeloma cells and (b) TRAIL should be used in combination with anti-inflammatory drugs for treatment of myeloma to avoid and/or minimize any potential side-effects arising from the proinflammatory properties of the molecule.

Cl-IB-MECA enhances TRAIL-induced apoptosis via the modulation of NF-kappaB signalling pathway in thyroid cancer cells

Apoptosis is an endogenous process that can be a useful anti-cancer tool. This study aimed to investigate the effect of Cl-IB-MECA, adenosine receptor A3 agonist, on TRAIL-induced apoptosis of thyroid carcinoma cells. Cl-IB-MECA enhanced TRAIL-mediated apoptosis in FRO but not in ARO cells. This effect was correlated to higher expression levels of DR5 on FRO than ARO cells, that instead presented higher levels of decoy receptors, DcR1 and DcR2. To understand the cross-talk between the effect of Cl-IB-MECA and TRAIL, we evaluated the nuclear translocation of p65 and c-Rel. Since the dependency by NF-kappaB, TRAIL promoted the nuclear translocation of both p65 and c-Rel subunits. However, the addition of Cl-IB-MECA led to the predominant translocation of c-Rel after TRAIL addition. Furthermore, Bcl-2, cFLIP and pAkt were lower induced than caspase-3 and -9 in FRO cells. To discriminate a specific effect of TRAIL, we used tumour necrosis factor-alpha (TNF-alpha) with Cl-IB-MECA. In this case, no synergism was observed. In addition, the effect of Cl-IB-MECA was not A3 receptor-dependent since its antagonists, MRS1191 and FA385, failed to block Cl-IB-MECA activity on TRAIL-treated FRO cells. In conclusion, Cl-IB-MECA enhanced TRAIL-mediated apoptosis via NF-kappaB/c-Rel activation and DR5-dependent manner. This study may shed light on a potential drug cocktail that may prove useful as anti-cancer in an in vivo animal model.

TRAIL, DR4 and DR5 are upregulated in kidneys from patients with lupus nephritis and exert proliferative and proinflammatory effects

We have previously reported that TRAIL is upregulated on T cells from patients with lupus and that T cell associated TRAIL enhances autoimmune parameters in a murine model of lupus. Whether TRAIL/TRAIL-R interaction plays a role in organ involvement such as lupus nephritis has not yet been assessed. We demonstrate here that TRAIL, DR4 and DR5 are upregulated in proximal and distal tubules of patients with proliferative lupus nephritis. In vitro, expression of TRAIL, DR4 and DR5 on primary proximal tubular epithelial cells (PTEC) was induced by TNFalpha and IFNgamma. Functionally, TRAIL did not induce apoptosis but rather enhanced the proliferation of PTEC through activation of PI3 kinase/AKT and ERK1/2, increased IL-8 production and upregulated ICAM-1 expression. These data demonstrate that cytokine induced upregulation of TRAIL, DR4 and DR5 in tubules from patients with proliferative lupus nephritis may play a protective role by enhancing PTEC survival while also exerting a proinflammatory effect that may contribute to local inflammation and injury.

The TRAIL apoptotic pathway in cancer onset, progression and therapy

Triggering of tumour cell apoptosis is the foundation of many cancer therapies. Death receptors of the tumour necrosis factor (TNF) superfamily have been largely characterized, as have the signals that are generated when these receptors are activated. TNF-related apoptosis-inducing ligand (TRAIL) receptors (TRAILR1 and TRAILR2) are promising targets for cancer therapy. Herein we review what is known about the molecular control of TRAIL-mediated apoptosis, the role of TRAIL in carcinogenesis and the potential therapeutic utility of recombinant TRAIL and agonistic antibodies against TRAILR1 and TRAILR2.

PI3-K/Akt-dependent activation of cAMP-response element-binding (CREB) protein in Jurkat T leukemia cells treated with TRAIL

We recently demonstrated the activation of phosphatidylinositol 3-kinase (PI3-K/Akt) survival pathway in Jurkat T leukemia cells known for their sensitivity to the tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL)/Apo2L cytotoxic action. The present investigation was done to elucidate the role of cAMP-response element-binding (CREB) protein in this system. Jurkat T cells were treated with 100-1,000 ng/ml TRAIL for time intervals up to 24 h in the presence or absence of selective pharmacologic inhibitors of PI3-K/Akt (LY294002) or p38 MAPK (SB253580) pathways. Upon TRAIL treatment, a dose-dependent increase in the percentage of apoptotic cells as well as in caspase-3 activity was observed. A further enhancement of apoptotic cell death was obtained with the use of CREB1 siRNA technology, as demonstrated by flow cytometry. Western blot analysis showed a high constitutive level of CREB phosphorylation at Ser(133) in Jurkat T cells under normal serum culture conditions. Under low serum culture conditions, an early (within 1 h) and transient increase in CREB phosphorylation was detected in response to both TRAIL doses and reduced upon pre-treatment with LY294002 or SB253580, demonstrating the PI3-K/Akt- and p38 MAPK-dependency of this effect. The parallel analysis in immune fluorescence demonstrated the nuclear translocation of the phosphorylated form upon treatment with 100 ng/ml TRAIL, whereas the immune labeling was mainly detectable in the cytoplasm compartment upon the higher more cytotoxic dose. These results let us hypothesize that CREB activation can be an important player in the complex cross-talk among pro- and anti-apoptotic pathways in this peculiar cell model.

Bortezomib sensitizes non-Hodgkin's lymphoma cells to apoptosis induced by antibodies to tumor necrosis factor related apoptosis-inducing ligand (TRAIL) receptors TRAIL-R1 and TRAIL-R2

Non-Hodgkin's lymphoma (NHL) is an increasingly common disease that, despite advances in antibody-targeted therapy, still requires novel therapeutic approaches. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) activates a major nonmitochondrial pathway for tumor cell killing through binding to a receptor family, some activating and some decoy. Agonistic antibodies to the receptors TRAIL-R1 and TRAIL-R2 can mimic many of the effects of TRAIL. We are investigating the effects of such agonistic antibodies, mapatumumab directed at TRAIL-R1 and lexatumumab directed at TRAIL-R2, on NHL cell lines. These antibodies induce apoptosis through caspase-8 but also activate BID to involve the mitochondrial pathway and activate caspase-9. In addition, we find signaling through both the nuclear factor-kappaB and c-Jun NH2-terminal kinase pathways. Because the proteasome inhibitor bortezomib also affects these pathways, we have investigated the combination of TRAIL-R antibodies and bortezomib and show enhanced apoptosis and signaling as well as enhanced killing of NHL cells in a severe combined immunodeficient mouse/human NHL cell line xenograft system. The combination of bortezomib and TRAIL signaling warrants further investigation as a therapeutic regimen. Understanding the multiple intracellular pathways of TRAIL activation may lead to rationally designed therapeutic trials.

Eliminating established tumor in nu/nu nude mice by a tumor necrosis factor-alpha-related apoptosis-inducing ligand-armed oncolytic adenovirus

PURPOSE

The tumor necrosis factor-alpha-related apoptosis-inducing ligand (TRAIL) and oncolytic viruses have recently been investigated extensively for cancer therapy. However, preclinical and clinical studies have revealed that their clinical application is hampered by either weak anticancer activity or systemic toxicity. We examined whether the weaknesses of the two strategies can be overcome by integrating the TRAIL gene into an oncolytic vector.

EXPERIMENTAL DESIGN

We constructed a TRAIL-expressing oncolytic adenovector designated as Ad/TRAIL-E1. The expression of both the TRAIL and viral E1A genes is under the control of a synthetic promoter consisting of sequences from the human telomerase reverse transcriptase promoter and a minimal cytomegalovirus early promoter. The transgene expression, apoptosis induction, viral replication, antitumor activity, and toxicity of Ad/TRAIL-E1 were determined in vitro and in vivo in comparison with control vectors.

RESULTS

Ad/TRAIL-E1 elicited enhanced viral replication and/or stronger oncolytic effect in vitro in various human cancer cell lines than a TRAIL-expressing, replication-defective adenovector or an oncolytic adenovector-expressing green fluorescent protein. Intralesional administration of Ad/TRAIL-E1 eliminated all s.c. xenograft tumors established from a human non-small cell lung cancer cell line, H1299, on nu/nu nude mice, resulting in long-term, tumor-free survival. Furthermore, we found no treatment-related toxicity.

CONCLUSIONS

Viral replication and antitumor activity of oncolytic adenovirus can be enhanced by the TRAIL gene and Ad/TRAIL-E1 could become a potent therapeutic agent for cancer therapy.

The cytotoxicity induced by brucine from the seed of Strychnos nux-vomica proceeds via apoptosis and is mediated by cyclooxygenase 2 and caspase 3 in SMMC 7221 cells

To study the cytotoxicity of four alkaloids: brucine, strychnine, brucine N-oxide and isostrychnine from nux vomica on SMMC 7721 cells and their possible mechanisms, MET assay was used to examine the growth inhibitory effects of these alkaloids. Brucine revealed the strongest growth inhibitory effect on SMMC-7721 cells. Furthermore, as directly observed under an inverted microscope, fluorescent microscope and transmission electronic microscope, brucine caused SMMC-7721 cell shrinkage, membrane blobbing, formation of apoptotic body as well as nucleus condensation, all of which are typical characteristics of apoptotic programmed cell death. In addition, brucine dose-dependently caused SMMC-7721 cells apoptosis via formation of subdipolid DNA and phosphatidylserine externalization, as evidenced by flow cytometry analysis. The brucine-induced apoptosis was partially attributed to the activation of caspase 3 as well as cyclooxygenase 2 inhibition, since neither caspase 3 specific inhibitor, z-DEVD-fmk nor was exogenous addition of prostaglandin E(2) able to completely abrogate the brucine-induced SMMC 7721 cell apoptosis. In sum, this paper indicate that the major alkaloids present in the seed of Strychnos nux-vomica are effective against SMMC-7721 cells proliferation, among which brucine proceeds SMMC-7721 cells death via apoptosis, probably through the participation of caspase 3 and cyclooxygenase 2.

Tumoricidal activity of TLR7/8-activated inflammatory dendritic cells

Imiquimod (IMQ), a synthetic agonist to Toll-like receptor (TLR) 7, is being successfully used for the treatment of certain skin neoplasms, but the exact mechanisms by which this compound induces tumor regression are not yet understood. While treating basal cell carcinoma (BCC) patients with topical IMQ, we detected, by immunohistochemistry, sizable numbers of both myeloid dendritic cells (mDCs) and plasmacytoid DCs (pDCs) within the inflammatory infiltrate. Surprisingly, peritumoral mDCs stained positive for perforin and granzyme B, whereas infiltrating pDCs expressed tumor necrosis factor–related apoptosis-inducing ligand (TRAIL). The biological relevance of this observation can be deduced from our further findings that peripheral blood–derived CD11c⁺ mDCs acquired antiperforin and anti–granzyme B reactivity upon TLR7/8 stimulation and could use these molecules to effectively lyse major histocompatibility complex (MHC) class I^lo cancer cell lines. The same activation protocol led pDCs to kill MHC class I–bearing Jurkat cells in a TRAIL-dependent fashion. While suggesting that mDCs and pDCs are directly involved in the IMQ-induced destruction of BCC lesions, our data also add a new facet to the functional spectrum of DCs, ascribing to them a major role not only in the initiation but also in the effector phase of the immune response.

TRAIL signalling: decisions between life and death

The TNF-related apoptosis-inducing ligand, TRAIL, has been shown to selectively kill tumour cells. This property has made TRAIL and agonistic antibodies against its death inducing receptors (TRAIL-R1 and TRAIL-R2) to some of the most promising novel biotherapeutic agents for cancer therapy. Here we review the signalling pathways initiated by the apoptosis- as well as the non-apoptosis-inducing receptors, TRAIL-R3 and TRAIL-R4. The TRAIL "death-inducing signalling complex" (DISC) transmits the apoptotic signal. DISC formation leads to activation of a protease cascade, finally resulting in cell death. The TRAIL death receptor-mediated "extrinsic" pathway and the "intrinsic" pathway, which is controlled by the interaction of members of the Bcl-2 family, interact with each other in the decision about life or death of a cell. Apoptotic and non-apoptotic signalling is influenced by the NF-kappaB, PKB/Akt and the MAPK signalling pathways. In this review we intend to summarise the most important findings on the TRAIL signalling network and the interplay in the decisions between life and death of a tumor cell.