Protein-based therapeutic approaches targeting death receptors

Endoplasmic reticulum stress and death receptor-mediated apoptosis in the neuronal differentiation of adult adipose-derived stromal cells

Apoptosis is the primary cause of cell death in the differentiation of Adipose-derived stromal cells (ADSCs) into neurons. However, the relationship between endoplasmic reticulum stress (ERS) and death receptor-mediated apoptosis in ADSC-induced neuronal differentiation is not clear. ADSCs were isolated and induced to differentiate into neurons using β-mercaptoethanol. The expression of neuron-specific enolase (NSE), GRP94, CHOP, Fas/FasL, TNFR1/TNF-α, DR5/TRAIL, Caspase8, and Caspase3 in ADSCs was examined using immunocytochemistry and Western blotting before induction, during pre-induction, and after induction. Transmission electron microscopy (TEM) was used to observe changes in the morphology of the endoplasmic reticulum (ER), and the MTT assay was employed to measure cell viability in the uninduced and induced groups. Additionally, the number of apoptotic cells during the induction process was measured using flow cytometry with Annexin V/PI. With increasing induction time, the positive expression rates of CHOP, Fas/FasL, Caspase8, Caspase-3, and NSE gradually increased, while the positive expression rate of GRP94 decreased. TNFR1/TNF-α and DR5/TRAIL peaked at 5 h post-induction and then decreased at 8 h. TEM revealed swelling and expansion of the ER, vacuolar changes, and degranulation in cells. The MTT assay showed a gradual decrease in the absorbance of surviving cells in all groups. Flow cytometry indicated an increasing rate of apoptosis in cells. Therefore, ERS in the normal culture and growth of ADSCs, manifesting as enhanced unfolded protein response (UPR), maintains the normal survival of ADSCs. However, in the process of ADSC-induced differentiation into neurons, ERS and death receptor-mediated apoptosis are significant causes of cell death.

Chitosan-based nanoscale delivery systems in hepatocellular carcinoma: Versatile bio-platform with theranostic application

The field of nanomedicine has provided a fresh approach to cancer treatment by addressing the limitations of current therapies and offering new perspectives on enhancing patients' prognoses and chances of survival. Chitosan (CS) is isolated from chitin that has been extensively utilized for surface modification and coating of nanocarriers to improve their biocompatibility, cytotoxicity against tumor cells, and stability. HCC is a prevalent kind of liver tumor that cannot be adequately treated with surgical resection in its advanced stages. Furthermore, the development of resistance to chemotherapy and radiotherapy has caused treatment failure. The targeted delivery of drugs and genes can be mediated by nanostructures in treatment of HCC. The current review focuses on the function of CS-based nanostructures in HCC therapy and discusses the newest advances of nanoparticle-mediated treatment of HCC. Nanostructures based on CS have the capacity to escalate the pharmacokinetic profile of both natural and synthetic drugs, thus improving the effectiveness of HCC therapy. Some experiments have displayed that CS nanoparticles can be deployed to co-deliver drugs to disrupt tumorigenesis in a synergistic way. Moreover, the cationic nature of CS makes it a favorable nanocarrier for delivery of genes and plasmids. The use of CS-based nanostructures can be harnessed for phototherapy. Additionally, the incur poration of ligands including arginylglycylaspartic acid (RGD) into CS can elevate the targeted delivery of drugs to HCC cells. Interestingly, smart CS-based nanostructures, including ROS- and pH-sensitive nanoparticles, have been designed to provide cargo release at the tumor site and enhance the potential for HCC suppression.

Anti-apoptosis effect of traditional Chinese medicine in the treatment of cerebral ischemia-reperfusion injury

Cerebral ischemia, one of the leading causes of neurological dysfunction of brain cells, muscle dysfunction, and death, brings great harm and challenges to individual health, families, and society. Blood flow disruption causes decreased glucose and oxygen, insufficient to maintain normal brain tissue metabolism, resulting in intracellular calcium overload, oxidative stress, neurotoxicity of excitatory amino acids, and inflammation, ultimately leading to neuronal cell necrosis, apoptosis, or neurological abnormalities. This paper summarizes the specific mechanism of cell injury that apoptosis triggered by reperfusion after cerebral ischemia, the related proteins involved in apoptosis, and the experimental progress of herbal medicine treatment through searching, analyzing, and summarizing the PubMed and Web Of Science databases, which includes active ingredients of herbal medicine, prescriptions, Chinese patent medicines, and herbal extracts, providing a new target or new strategy for drug treatment, and providing a reference for future experimental directions and using them to develop suitable small molecule drugs for clinical application. With the research of anti-apoptosis as the core, it is important to find highly effective, low toxicity, safe and cheap compounds from natural plants and animals with abundant resources to prevent and treat Cerebral ischemia/reperfusion (I/R) injury (CIR) and solve human suffering. In addition, understanding and summarizing the apoptotic mechanism of cerebral ischemia-reperfusion injury, the microscopic mechanism of CIR treatment, and the cellular pathways involved will help to develop new drugs.

Semisynthetic aurones A14 protects against T-cell acute lymphoblastic leukemia via suppressing proliferation and inducing cell cycle arrest with apoptosis

BACKGROUND

Acute lymphoblastic leukemia is an aggressive neoplasm and seriously threatens human health. A14 is one kind of semisynthetic aurone that exhibits the capability to inhibit prostate cancer, but little is known about the role of A14 on T-cell acute lymphoblastic leukemia.

METHODS

Firstly, the effects of A14 on the ability of leukemia cells to proliferate were measured by Vi-cell counter. Then, we detected the cell cycle and apoptosis by flow cytometry and characterized the related protein expression using immunoblotting. In addition, we constructed stable luciferase expressing cell lines for use in a cell derived xenograft mouse model to measure the effect of A14 on T-cell acute lymphoblastic leukemia.

RESULTS

Results exhibited that A14 markedly suppressed cell proliferation and induced G2/M phase arrest along with cell cycles regulating proteins changes. A14 led to apoptosis in leukemia cells, at least partly, through the cytochrome c signaling pathway. Experiments in cell derived xenograft mouse model also showed that A14 markedly ameliorated the survival rate.

CONCLUSIONS

The present study revealed that semisynthetic aurones A14 can effectively protect against T-cell acute lymphoblastic leukemia progression both in vitro and in vivo, indicating the capability of A14 as a promising drug for the treatment of T-cell acute lymphoblastic leukemia.

Anticancer peptides mechanisms, simple and complex

Peptide therapy has started since 1920s with the advent of insulin application, and now it has emerged as a new approach in treatment of diseases including cancer. Using anti-cancer peptides (ACPs) is a promising way of cancer therapy as ACPs are continuing to be approved and arrived at major pharmaceutical markets. Traditional cancer treatments face different problems like intensive adverse effects to patient's body, cell resistance to conventional chemical drugs and in some worse cases the occurrence of cell multidrug resistance (MDR) of cancerous tissues against chemotherapy. On the other hand, there are some benefits conceived for peptides usage in treatment of diseases specifically cancer, as these compounds present favorable characteristics such as smaller size, high activity, low immunogenicity, good biocompatibility in vivo, convenient and rapid way of synthesis, amenable to sequence modification and revision and there is no limitation for the type of cargo they carry. It is possible to achieve an optimum molecular and functional structure of peptides based on previous experience and bank of peptide motif data which may result in novel peptide design. Bioactive peptides are able to form pores in cell membrane and induce necrosis or apoptosis of abnormal cells. Moreover, recent researches have focused on the tumor recognizing peptide motifs with the ability to permeate to cancerous cells with the aim of cancer treatment at earlier stages. In this strategy the most important factors for addressing cancer are choosing peptides with easy accessibility to tumor cell without cytotoxicity effect towards normal cells. The peptides must also meet acceptable pharmacokinetic requirements. In this review, the characteristics of peptides and cancer cells are discussed. The various mechanisms of peptides' action proposed against cancer cells make the next part of discussion. It will be followed by giving information on peptides application, various methods of peptide designing along with introducing various databases. Future aspects of peptides for employing in area of cancer treatment come as conclusion at the end.

Blood Biomarkers to Predict Long-Term Mortality after Ischemic Stroke

Stroke is a major cause of disability and death globally, and prediction of mortality represents a crucial challenge. We aimed to identify blood biomarkers measured during acute ischemic stroke that could predict long-term mortality. Nine hundred and forty-one ischemic stroke patients were prospectively recruited in the Stroke-Chip study. Post-stroke mortality was evaluated during a median 4.8-year follow-up. A 14-biomarker panel was analyzed by immunoassays in blood samples obtained at hospital admission. Biomarkers were normalized and standardized using Z-scores. Multiple Cox regression models were used to identify clinical variables and biomarkers independently associated with long-term mortality and mortality due to stroke. In the multivariate analysis, the independent predictors of long-term mortality were age, female sex, hypertension, glycemia, and baseline National Institutes of Health Stroke Scale (NIHSS) score. Independent blood biomarkers predictive of long-term mortality were endostatin > quartile 2, tumor necrosis factor receptor-1 (TNF-R1) > quartile 2, and interleukin (IL)-6 > quartile 2. The risk of mortality when these three biomarkers were combined increased up to 69%. The addition of the biomarkers to clinical predictors improved the discrimination (integrative discriminative improvement (IDI) 0.022 (0.007–0.048), p < 0.001). Moreover, endostatin > quartile 3 was an independent predictor of mortality due to stroke. Altogether, endostatin, TNF-R1, and IL-6 circulating levels may aid in long-term mortality prediction after stroke.

Selective HSP90β inhibition results in TNF and TRAIL mediated HIF1α degradation

Signaling via TNF-R1 mediates pleiotropic biological outcomes ranging from inflammation and proliferation to cell death. Previous reports demonstrated that pro-survival signaling emanates from membrane resident TNF-R1 complexes (complex I) while only internalized TNF-R1 complexes are capable for DISC formation (complex II) and thus, apoptosis induction. Internalized TNF-R1 containing endosomes undergo intracellular maturation towards lysosomes, resulting in activation and release of Cathepsin D (CtsD) into the cytoplasm. We recently revealed HSP90 as target for proteolytic cleavage by CtsD, resulting in cell death amplification. In this study, we show that extrinsic cell death activation via TNF or TRAIL results in HSP90β degradation. Co-incubation of cells with either TNF or TRAIL in combination with the HSP90β inhibitor KUNB105 but not HSP90α selective inhibition promotes apoptosis induction. In an attempt to reveal further downstream targets of combined TNF-R1 or TRAIL-R1/-R2 activation with HSP90β inhibition, we identify HIF1α and validate its ligand:inhibitor triggered degradation. Together, these findings suggest that selective inhibition of HSP90 isoforms together with death ligand stimulation may provide novel strategies for therapy of inflammatory diseases or cancer, in future.

Elevated Concentrations of Soluble Fas and FasL in Multiple Sclerosis Patients with Antinuclear Antibodies

Antinuclear antibodies (ANA) are currently considered as an epiphenomenon of apoptotic processes, possibly in control of autoreactivity in patients with multiple sclerosis (MS). Apoptosis of reactive lymphocytes by the Fas/FasL system is described as an effective control mechanism for autoreactivity in MS. We aimed to provide a context to the potential link between ANA and peripheral lymphocyte apoptosis in MS. The presence of ANA was detected in sera by immunofluorescence assay, and concentrations of sFas and sFasL were determined in the sera of 44 and cerebrospinal fluid (CSF) of 11 relapsing-remitting (RR) MS patients using cytometric bead-based array, and their association with the disease characteristics was determined. ANA were detected in the sera of 43.2% of RRMS patients, and their frequency was the highest in patients with disease duration of less than one year (88,89%). In addition, the number of experienced relapses was lower in ANA-positive patients. Concentrations of sFasL were inversely associated with patients' expanded disability status scale (EDSS) scores. Low concentrations of both soluble factors strongly discriminated patients with moderate to severe disability, from patients with mild or absent disability only in a group of patients with prolonged disease duration (>10 years). Both soluble mediators were significantly higher in ANA-positive patients. FasL concentrations were inversely associated with the number of relapses. There is a potential link between the presence of ANA and peripheral lymphocyte apoptosis mediated by Fas/FasL system in MS, whose precise role and significance needs to be determined by future mechanistic studies.

Improved melanoma suppression with target-delivered TRAIL and Paclitaxel by a multifunctional nanocarrier

Malignant melanoma, a highly dangerous type of skin cancer, is usually resistant to pro-apoptosis agents such as tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) due to low death receptor expression levels. After verifying combination of chemotherapy drug paclitaxel (PTX) and TRAIL could significantly enhance their anti-melanoma effects, we developed a liposomal melanoma target-delivery system with tumor microenvironment responsiveness (TRAIL-[Lip-PTX]^C18-TR) to co-deliver TRAIL and PTX. TRAIL is attached to negatively-charged liposome surface while PTX is encapsulated inside, with final surface modification of a stearyl chain (C18) fused pH-sensitive cell-penetrating peptide (TR). Here, C18-TR could specifically binds to melanoma-rich integrin receptors α_vβ₃ for melanoma targeting, help release TRAIL in low pH microenvironment by reversing the liposomal charge, and facilitate consequent liposome internalization. TRAIL-[Lip-PTX]^C18-TR displayed significantly better in vitro half-maximal inhibitory concentration (IC₅₀) than other formulations, and an in vivo tumor inhibition rate of 93.8%. Mechanistic study revealed that this synergistic effect is associated with the upregulation of death receptors DR4/5 by PTX. This co-delivery system significantly improved TRAIL-based therapy against melanoma, and provided a simple platform to co-deliver other drugs/agents for melanoma treatment.

ITCH-dependent proteasomal degradation of c-FLIP induced by the anti-HER3 antibody 9F7-F11 promotes DR5/caspase 8-mediated apoptosis of tumor cells

Background

HER3/ErbB3 receptor deletion or blockade leads to tumor cell apoptosis, whereas its overexpression confers anti-cancer drug resistance through upregulation of protective mechanisms against apoptosis. We produced the anti-HER3 antibody 9F7-F11 that promotes HER3 ubiquitination and degradation via JNK1/2-dependent activation of the E3 ubiquitin ligase ITCH, and that induces apoptosis of cancer cells. Cellular FLICE-like inhibitory protein (c-FLIP) is a key regulator of apoptotic pathways. Here, we wanted to determine the mechanisms underlying the pro-apoptotic effect of 9F7-F11.

Methods

Anti-HER3 antibody-induced apoptosis was assessed by western blot, and by flow cytometry measurement of Annexin V/7-AAD-labelled tumor cells (BxPC3, MDA-MB-468 and DU145 cell lines). c-FLIP/ITCH interaction and subsequent degradation/ubiquitination were investigated by co-immunoprecipitation of ITCH-silenced vs scramble control cells. The relationship between ITCH-mediated c-FLIP degradation and antibody-induced apoptosis was examined by western blot and flow cytometry of tumor cells, after ITCH RNA interference or by pre-treatment with ITCH chemical inhibitor chlorimipramine (CI).

Results

Following incubation with 9F7-F11, cancer cell apoptosis occurs through activation of caspase-8, − 9 and − 3 and the subsequent cleavage of poly (ADP-ribose) polymerase (PARP). Moreover we showed that ubiquitination and proteasomal degradation of the anti-apoptotic protein c-FLIP was mediated by USP8-regulated ITCH recruitment. This effect was abrogated by ITCH- and USP8-specific RNA interference (siRNA), or by the ITCH chemical inhibitor CI. Specifically, ITCH silencing or CI blocked 9F7-F11-induced caspase-8-mediated apoptosis of tumor cells, and restored c-FLIP expression. ITCH-silencing or CI concomitantly abrogated HER3-specific antibody-induced apoptosis of Annexin V/7-AAD-labelled BxPC3 cells. 9F7-F11 favored the extrinsic apoptosis pathway by inducing TRAIL-R2/DR5 upregulation and TRAIL expression that promoted the formation of death-inducing signaling complex (DISC), leading to caspase-8-mediated apoptosis. Incubation with 9F7-F11 also induced BID cleavage, BAX upregulation and BIM expression, which initiated the caspase-9/3-mediated mitochondrial death pathway. The anti-HER3 antibody pro-apoptotic effect occurred concomitantly with downregulation of the pro-survival proteins c-IAP2 and XIAP.

Conclusions

The allosteric non-neuregulin competing modulator 9F7-F11, sensitizes tumor cells to DR5/caspase-8-mediated apoptosis through ITCH-dependent downregulation of c-FLIP.

Graphical abstract

Electronic supplementary material

The online version of this article (10.1186/s12964-019-0413-8) contains supplementary material, which is available to authorized users.

The Role of Inflammatory Response in Stroke Associated Programmed Cell Death

Stroke represents devastating pathology which is associated with a high morbidity and mortality. Initial damage caused directly by the onset of stroke, primary injury, may be eclipsed by secondary injury which may have a much more devastating effect on the brain. Primary injury is predominantly associated with necrotic cell death due to fatal insufficiency of oxygen and glucose. Secondary injury may on the contrary, lead apoptotic cell death due to structural damage which is not compatible with cellular functions or which may even represent the danger of malign transformation. The immune system is responsible for surveillance, defense and healing processes and the immune system plays a major role in triggering programmed cell death. Severe pathologies, such as stroke, are often associated with deregulation of the immune system, resulting in aggravation of secondary brain injury. The goal of this article is to overview the current knowledge about the role of immune system in the pathophysiology of stroke with respect to programmed neuronal cell death as well as to discuss current therapeutic strategies targeting inflammation after stroke.

Inhibition of NF-κB Pathway and Modulation of MAPK Signaling Pathways in Glioblastoma and Implications for Lovastatin and Tumor Necrosis Factor-Related Apoptosis Inducing Ligand (TRAIL) Combination Therapy

Glioblastoma is a common malignant brain tumor and it is refractory to therapy because it usually contains a mixture of cell types. The tumor necrosis factor-related apoptosis inducing ligand (TRAIL) has been shown to induce apoptosis in a range of tumor cell types. Previously, we found that two human glioblastoma cell lines are resistant to TRAIL, while lovastatin sensitizes these glioblastoma cells to TRAIL-induced cell death. In this study, we investigated the mechanisms underlying the TRAIL-induced apoptosis in human glioblastoma cell lines by lovastatin. Furthermore, we have confirmed the anti-tumor effect of combination therapy with lovastatin and TRAIL in the subcutaneous brain tumor model. We showed that lovastatin significantly up-regulated the expression of death receptor 5 (DR5) in glioblastoma cell lines as well as in tumor-bearing mice with peri-tumoral administration of lovastatin. Further study in glioblastoma cell lines suggested that lovastatin treatment could inhibit NF-κB and Erk/MAPK pathways but activates JNK pathway. These results suggest that lovastatin sensitizes TRAIL-induced apoptosis by up-regulation of DR5 level via NF-κB inactivation, but also directly induces apoptosis by dysregulation of MAPK pathway. Our in vivo study showed that local peri-tumoral co-injection of lovastatin and TRAIL substantially reduced tumor growth compared with single injection of lovastatin or TRAIL in subcutaneous nude mice model. This study suggests that combined treatment of lovastatin and TRAIL is a promising therapeutic strategy to TRAIL-resistant glioblastoma.

Cloning, characterization and comparative analysis of four death receptorTNFRs from the oyster Crassostrea hongkongensis

Apoptosis plays an important role in homeostasis of the immune systems. The tumor necrosis factor receptors (TNFRs) play critical roles in the extrinsic apoptosis pathways and in determining cell fate. In this study, four death receptors (DR) named ChEDAR, ChTNFR27, ChTNFR5, and ChTNFR16 were identified from the oyster Crassostrea hongkongensis. These ChDRs proteins had 382, 396, 414 and 384 amino acids, respectively, with the typical domains of death receptors, such as the signal peptide (SP), transmembrane helix region (TM) and death domains. Phylogenetic analysis showed that the ChDR proteins clustered into three distinct groups, indicating that these subfamilies had common ancestors. mRNA expression of the ChDRs were detected in all 8 of the selected oyster tissues and at different stages of development. Furthermore, expression of all the genes was increased in the hemocytes of oysters challenged with pathogens or air stress. Fluorescence microscopy revealed that the full-length proteins of the ChDRs were located in the plasma membrane of HEK293T cells. Over-expression of the ChDRs activated the NF-κB-Luc reporter in HEK293T cells in a dose-dependent manner. These results indicate that the ChDRs may play important roles in the extrinsic apoptotic pathways in oysters.

Cryo-EM Structure of Caspase-8 Tandem DED Filament Reveals Assembly and Regulation Mechanisms of the Death-Inducing Signaling Complex

Caspase-8 activation can be triggered by death receptor-mediated formation of the death-inducing signaling complex (DISC) and by the inflammasome adaptor ASC. Caspase-8 assembles with FADD at the DISC and with ASC at the inflammasome through its tandem death effector domain (tDED), which is regulated by the tDED-containing cellular inhibitor cFLIP and the viral inhibitor MC159. Here we present the caspase-8 tDED filament structure determined by cryoelectron microscopy. Extensive assembly interfaces not predicted by the previously proposed linear DED chain model were uncovered, and were further confirmed by structure-based mutagenesis in filament formation in vitro and Fas-induced apoptosis and ASC-mediated caspase-8 recruitment in cells. Structurally, the two DEDs in caspase-8 use quasi-equivalent contacts to enable assembly. Using the tDED filament structure as a template, structural analyses reveal the interaction surfaces between FADD and caspase-8 and the distinct mechanisms of regulation by cFLIP and MC159 through comingling and capping, respectively.

USP8 suppresses death receptor-mediated apoptosis by enhancing FLIPL stability

FLICE-like inhibitory protein (FLIP) is a critical regulator of death receptor-mediated apoptosis. Here, we found ubiquitin-specific peptidase 8 (USP8) to be a novel deubiquitylase of the long isoform of FLIP (FLIP_L). USP8 directly deubiquitylates and stabilizes FLIP_L, but not the short isoform. USP8 depletion induces FLIP_L destabilization, promoting anti-Fas-, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)- and tumor necrosis factor alpha-induced extrinsic apoptosis by facilitating death-inducing signaling complex or TNFR1 complex II formation, which results in the activation of caspase-8 and caspase-3. USP8 mRNA levels are elevated in melanoma and cervical cancers, and the protein levels of USP8 and FLIP_L are positively correlated in these cancer cell lines. Xenograft analyses using ME-180 cervical cancer cells showed that USP8 depletion attenuated tumor growth upon TRAIL injection. Taken together, our data indicate that USP8 functions as a novel deubiquitylase of FLIP_L and inhibits extrinsic apoptosis by stabilizing FLIP_L.

The pyrrolo-1,5-benzoxazepine, PBOX-15, enhances TRAIL‑induced apoptosis by upregulation of DR5 and downregulation of core cell survival proteins in acute lymphoblastic leukaemia cells

Apoptotic defects are frequently associated with poor outcome in pediatric acute lymphoblastic leukaemia (ALL) hence there is an ongoing demand for novel strategies that counteract apoptotic resistance. The death ligand TRAIL (tumour necrosis factor-related apoptosis-inducing ligand) and its selective tumour receptor system has attracted exceptional clinical interest. However, many malignancies including ALL are resistant to TRAIL monotherapy. Tumour resistance can be overcome by drug combination therapy. TRAIL and its agonist antibodies are currently undergoing phase II clinical trials with established chemotherapeutics. Herein, we present promising therapeutic benefits in combining TRAIL with the selective anti-leukaemic agents, the pyrrolo-1,5-benzoxazepines (PBOXs) for the treatment of ALL. PBOX-15 synergistically enhanced apoptosis induced by TRAIL and a DR5-selective TRAIL variant in ALL-derived cells. PBOX-15 enhanced TRAIL-induced apoptosis by dual activation of extrinsic and intrinsic apoptotic pathways. The specific caspase-8 inhibitor, Z-IETD-FMK, identified the extrinsic pathway as the principal mode of apoptosis. We demonstrate that PBOX-15 can enhance TRAIL-induced apoptosis by upregulation of DR5, reduction of cellular mitochondrial potential, activation of the caspase cascade and downregulation of PI3K/Akt, c-FLIP, Mcl-1 and IAP survival pathways. Of note, the PI3K pathway inhibitor LY-294002 significantly enhanced the apoptotic potential of TRAIL and PBOX-15 validating the importance of Akt downregulation in the TRAIL/PBOX-15 synergistic combination. Considering the lack of cytotoxicity to normal cells and ability to downregulate several survival pathways, PBOX-15 may represent an effective agent for use in combination with TRAIL for the treatment of ALL.

Bee venom inhibits growth of human cervical tumors in mice

We studied whether bee venom (BV) inhibits cervical tumor growth through enhancement of death receptor (DR) expressions and inactivation of nuclear factor kappa B (NF-κB) in mice. In vivo study showed that BV (1 mg/kg) inhibited tumor growth. Similar inhibitory effects of BV on cancer growth in primary human cervical cancer cells were also found. BV (1–5 μg/ml) also inhibited the growth of cancer cells, Ca Ski and C33Aby the induction of apoptotic cell death in a dose dependent manner. Agreed with cancer cell growth inhibition, expression of death receptors; FAS, DR3 and DR6, and DR downstream pro-apoptotic proteins including caspase-3 and Bax was concomitantly increased, but the NF-κB activity and the expression of Bcl-2 were inhibited by treatment with BV in tumor mice, human cancer cell and human tumor samples as well as cultured cancer cells. In addition, deletion of FAS, DR3 and DR6 by small interfering RNA significantly reversed BV-induced cell growth inhibitory effects as well as NF-κB inactivation. These results suggest that BV inhibits cervical tumor growth through enhancement of FAS, DR3 and DR6 expression via inhibition of NF-κB pathway.

Cell death at the intestinal epithelial front line

The intestinal epithelium represents the largest epithelial surface in our body. This single-cell-layer epithelium mediates important functions in the absorption of nutrients and in the maintenance of barrier function, preventing luminal microorganisms from invading the body. Due to its constant regeneration the intestinal epithelium is a tissue not only with very high proliferation rates but also with very prominent physiological and pathophysiological cell death induction. The normal physiological differentiation and maturation of intestinal epithelial cells leads to their shedding and apoptotic cell death within a few days, without disturbing the epithelial barrier integrity. In contrast excessive intestinal epithelial cell death induced by irradiation, drugs and inflammation severely impairs the vital functions of this tissue. In this review we discuss cell death processes in the intestinal epithelium in health and disease, with special emphasis on cell death triggered by the tumour necrosis factor receptor family.

Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis--A Comprehensive Review and Guide to Therapy. I. Systemic Disease

The intent of this review is to comprehensively appraise the state of the art with regard to Stevens Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN), with particular attention to the ocular surface complications and their management. SJS and TEN represent two ends of a spectrum of immune-mediated, dermatobullous disease, characterized in the acute phase by a febrile illness followed by skin and mucous membrane necrosis and detachment. The widespread keratinocyte death seen in SJS/TEN is rapid and irreversible, and even with early and aggressive intervention, morbidity is severe and mortality not uncommon. We have divided this review into two parts. Part I summarizes the epidemiology and immunopathogenesis of SJS/TEN and discusses systemic therapy and its possible benefits. We hope this review will help the ophthalmologist better understand the mechanisms of disease in SJS/TEN and enhance their care of patients with this complex and often debilitating disease. Part II (April 2016 issue) will focus on ophthalmic manifestations.

Apoptotic and autophagic pathways with relevant small-molecule compounds, in cancer stem cells

Accumulating evidence demonstrates existence of cancer stem cells (CSCs), which are suspected of contributing to cancer cell self-renewal capacity and resistance to radiation and/or chemotherapy. Including evasion of apoptosis and autophagic cell death, CSCs have revealed abilities to resist cell death, making them appealing targets for cancer therapy. Recently, molecular mechanisms of apoptosis and of autophagy in CSCs have been gradually explored, comparing them in stem cells and in cancer cells; distinct expression of these systems in CSCs may elucidate how these cells exert their capacity of unlimited self-renewal and hierarchical differentiation. Due to their proposed ability to drive tumour initiation and progression, CSCs may be considered to be potentially useful pharmacological targets. Further, multiple compounds have been verified as triggering apoptosis and/or autophagy, suppressing tumour growth, thus providing new strategies for cancer therapy. In this review, we summarized regulation of apoptosis and autophagy in CSCs to elucidate how key proteins participate in control of survival and death; in addition, currently well-studied compounds that target CSC apoptosis and autophagy are selectively presented. With increasing attention to CSCs in cancer therapy, researchers are now trying to find responses to unsolved questions as unambiguous as possible, which may provide novel insight into future anti-cancer regimes.

Stevens-Johnson syndrome and toxic epidermal necrolysis (SJS/TEN): could retinoids play a causative role?

Stevens-Johnson syndrome and toxic epidermal necrolysis (SJS/TEN) are overlapping manifestations on a spectrum of acute drug-induced conditions associated with severe blistering, skin peeling, and multi-organ damage. TEN is an eruption resembling severe scalding, with ≥30% skin detachment. SJS is a mild form of TEN, characterized histologically by epidermal keratinocyte apoptosis with dermo-epidermal separation and extensive small blisters with <10% body surface skin detachment. The syndrome can be induced by numerous medications and typically occurs 1–4 weeks after the initiation of therapy. Granulysin is found in the lesions of patients with SJS/TEN and plays a significant pathogenic role in the condition, but the overall mechanisms linking medications, granulysin, and disease manifestations remain obscure. This paper reviews evidence suggesting that the different medications implicated in SJS/TEN have the common property of interacting and synergizing with endogenous retinoids (vitamin A and its congeners), in many instances causing the latter to accumulate in and damage the liver, the main storage organ for vitamin A. It is hypothesized that liver damage leads to the spillage of toxic retinoid compounds into the circulation, resulting in an endogenous form of hypervitaminosis A and cytotoxicity with widespread apoptosis, mediated by granulysin and recognized as SJS/TEN. Subject to testing, the model suggests that symptom worsening could be arrested at onset by lowering the concentration of circulating retinoids and/or granulysin via phlebotomy or plasmapheresis or by pharmacological measures to limit their expression.

Modulation of specificity protein 1 by mithramycin A as a novel therapeutic strategy for cervical cancer

Cervical cancer is the third most common cancer and the third leading cause of death among women. However, the standard treatment for cervical cancer includes cisplatin, which can cause side effects such as hematological damage or renal toxicity. New innovations in cervical cancer treatment focus on developing more effective and better-tolerated therapies such as Sp1-targeting drugs. Previous studies suggested that mithramycin A (Mith) inhibits the growth of various cancers by decreasing Sp1 protein. However, how Sp1 protein is decreased by Mith is not clear. Few studies have investigated the regulation of Sp1 protein by proteasome-dependent degradation as a possible control mechanism for the regulation of Sp1 in cancer cells. Here, we show that Mith decreased Sp1 protein by inducing proteasome-dependent degradation, thereby suppressing cervical cancer growth through a DR5/caspase-8/Bid signaling pathway. We found that prolonged Mith treatment was well tolerated after systemic administration to mice carrying cervical cancer cells. Reduction of body weight was minimal, indicating that Mith was a good therapeutic candidate for treatment of cancers in which Sp1 is involved in promoting and developing disease.

Preparation and functional studies of hydroxyethyl chitosan nanoparticles loaded with anti-human death receptor 5 single-chain antibody

Objective

To prepare hydroxyethyl chitosan nanoparticles loaded with anti-human death receptor 5 single-chain antibody, and study their characteristics, functions, and mechanisms of action.

Materials and methods

The anti-human death receptor 5 single-chain antibody was constructed and expressed. Protein-loaded hydroxyethyl chitosan nanoparticles were prepared, and their size, morphology, particle-size distribution and surface zeta potential were measured by scanning electron microscopy and laser particle-size analysis. Mouse H22 hepatocellular carcinoma cells were cultured, and growth inhibition was examined using the CellTiter-Blue cell-viability assay. Flow cytometry and Hoechst 33342 were employed to measure cell apoptosis. Kunming mice with H22 tumor models were treated with protein-loaded hydroxyethyl chitosan nanoparticles, and their body weight and tumor size were measured, while hematoxylin and eosin staining was used to detect antitumor effects in vivo and side effects from tumors.

Results

The protein-loaded hydroxyethyl chitosan nanoparticles had good stability; the zeta potential was −24.2±0.205, and the dispersion index was 0.203. The inhibition of the protein-loaded hydroxyethyl chitosan nanoparticles on H22 growth was both time- and dose-dependent. Increased expressions of active caspase 8, active caspase 3, and BAX were detected following treatment. The average weight gain, tumor weight, and mean tumor volume of the protein and protein-loaded hydroxyethyl chitosan nanoparticle groups were significantly different (P<0.05) compared with the phosphate-buffered saline group.

Conclusion

The protein-loaded hydroxyethyl chitosan nanoparticles effectively suppressed tumor growth, indicating that nanotechnology has the potential for broad application in cancer therapy.

FAS/FASL expression profile as a prognostic marker in squamous cell carcinoma of the oral cavity

FAS/FASL altered expression may cause tumor protecting immunomodulation, with a direct impact on patient prognosis. FAS expression was studied in 60 squamous cell carcinomas of the oral cavity. FAS expression did not show a significant association with tumor histopathological characteristics, but was significantly associated with lymph node positivity. FAS expression was significantly associated with disease specific death and negative FAS expression was an independent risk factor, increasing risk 4 times when compared to positive expression. When FAS and FASL expression results were combined, we were able to define high, intermediate and low risk profiles. Disease-free and disease-specific survival were significantly correlated with FAS/FASL expression profiles. The high risk category was an independent marker for earlier disease relapse and disease-specific death, with approximately 4- and 6-fold increased risk, respectively, when compared to the low risk profile. Risk profiles based on FAS/FASL expression showed that high risk was significantly associated with increased disease relapse and death, as well as shorter disease-free or disease-specific survival. This categorization, added to patient clinical data, may facilitate the choice of therapy, minimizing treatment failure and increasing disease control.

A DR6/p75(NTR) complex is responsible for β-amyloid-induced cortical neuron death

The p75 neurotrophin receptor (p75(NTR)) is a known mediator of β-amyloid (Aβ)-induced neurotoxicity implicated in Alzheimer's disease (AD). Here, we demonstrate that death receptor 6 (DR6) binds to p75(NTR) and is a component of the p75(NTR) signaling complex responsible for Aβ-induced cortical neuron death. Cortical neurons isolated from either DR6 or p75(NTR) null mice are resistant to Aβ-induced neurotoxicity. Blocking DR6 function in cortical neurons by anti-DR6 antibodies that block the binding of DR6 to p75(NTR) receptor complex or by a dominant negative DR6 construct lacking the cytoplasmic signaling death domain attenuates Aβ-induced caspase 3 activation and cell death. DR6 expression is upregulated in AD cortex and correlates with elevated neuronal death. Targeting the disruption of the DR6/p75(NTR) complex to prevent Aβ cytotoxicity represents a new approach for the treatment of neurodegenerative disorders such as AD.

The roles of FADD in extrinsic apoptosis and necroptosis

Fas-associated protein with death domain (FADD), an adaptor that bridges death receptor signaling to the caspase cascade, is indispensible for the induction of extrinsic apoptotic cell death. Interest in the non-apoptotic function of FADD has greatly increased due to evidence that FADD-deficient mice or dominant-negative FADD transgenic mice result in embryonic lethality and an immune defect without showing apoptotic features. Numerous studies have suggested that FADD regulates cell cycle progression, proliferation, and autophagy, affecting these phenomena. Recently, programmed necrosis, also called necroptosis, was shown to be a key mechanism that induces embryonic lethality and an immune defect. Supporting these findings, FADD was shown to be involved in various necroptosis models. In this review, we summarize the mechanism of extrinsic apoptosis and necroptosis, and discuss the in vivo and in vitro roles of FADD in necroptosis induced by various stimuli.

Self-assembled DNA-based giant thrombin nanoparticles for controlled release

Protein-aptamer interactions have been used in a wide range of fields, including medical diagnosis and protein delivery. Herein, we report a method for thrombin delivery with thrombin-binding aptamer (TBA), which is one of the well-known aptamers for thrombin, by generating giant thrombin nanoparticles (GTNPs). GTNPs can be synthesized by crosslinking thrombin with DNA nanostructures that possess several TBA molecules. To generate GTNPs, two different DNA nanostructures were used. Y-shaped DNA with TBA and X-shaped DNA with TBA were used for 250 and 650 nm GTNPs, respectively. Controlled release of thrombin from GTNPs was performed by adding complementary DNA (cDNA) to TBA. To investigate thrombin release from GTNPs, the sizes of the GTNPs were measured using dynamic light scattering, atomic force microscopy (AFM), and scanning electron microscopy (SEM). We confirmed a decrease in the size of GTNPs with various concentrations of cDNA, suggesting the release of thrombin. Based on these results, we expect that our method can be used to control the amount of thrombin released effectively. Our method is also widely applicable for effective protein delivery.

Apoptosis in health and disease and modulation of apoptosis for therapy: An overview

Apoptosis a physiological mechanism that eliminates excessive, damaged or unwanted cells, is a highly regulated pathway important for maintaining homeostasis in multicellular organisms. It can be initiated through various signals via the extrinsic pathway which involves death receptors, or via the intrinsic pathway which is initiated by intracellular damage and involves the mitochondria and release of cytochrome c from it to further activate caspases. The Bcl-2 family of proteins is situated upstream to the irreversible damage of cellular constituents and is an important checkpoint in the fate of a cell. The pro-apoptotic members, BH3 only members include BID, BAD and BIM. They directly or indirectly activate multidomain BAX/BAK that constitute the requisite gateway to the intrinsic pathway which operates at the mitochondrial surface and endoplasmic reticulum. In contrast, antiapoptotic members such as Bcl-2, Bcl-XL bind and sequester activation. Downstream of mitochondria, the apoptosome involvement is seen to generate caspase activity. Post mitochondria regulation involves IAPs, and their inhibitors. The pathogenesis of several diseases such as cancer, neurodegenerative disorders, autoimmune disorders, heart disease, infectious diseases including AIDS is closely related to aberrant apoptosis. Consequently interest has emerged in employing various the rapeutic approaches such as gene therapy, antisense therapy, recombinant biologicals, organic and combinatorial chemistry, to specifically target apoptosis signaling pathways such as death receptors FAS/TRAIL, Bcl-2, p53, IAPs, SMAC and caspases, etc. and are now advancing from preclinical to clinical phase.

Simultaneous modulation of the intrinsic and extrinsic pathways by simvastatin in mediating prostate cancer cell apoptosis

Background

Recent studies suggest the potential benefits of statins as anti-cancer agents. Mechanisms by which statins induce apoptosis in cancer cells are not clear. We previously showed that simvastatin inhibit prostate cancer cell functions and tumor growth. Molecular mechanisms by which simvastatin induce apoptosis in prostate cancer cells is not completely understood.

Methods

Effect of simvastatin on PC3 cell apoptosis was compared with docetaxel using apoptosis, TUNEL and trypan blue viability assays. Protein expression of major candidates of the intrinsic pathway downstream of simvastatin-mediated Akt inactivation was analyzed. Gene arrays and western analysis of PC3 cells and tumor lysates were performed to identify the candidate genes mediating extrinsic apoptosis pathway by simvastatin.

Results

Data indicated that simvastatin inhibited intrinsic cell survival pathway in PC3 cells by enhancing phosphorylation of Bad, reducing the protein expression of Bcl-2, Bcl-xL and cleaved caspases 9/3. Over-expression of PC3 cells with Bcl-2 or DN-caspase 9 did not rescue the simvastatin-induced apoptosis. Simvastatin treatment resulted in increased mRNA and protein expression of molecules such as TNF, Fas-L, Traf1 and cleaved caspase 8, major mediators of intrinsic apoptosis pathway and reduced protein levels of pro-survival genes Lhx4 and Nme5.

Conclusions

Our study provides the first report that simvastatin simultaneously modulates intrinsic and extrinsic pathways in the regulation of prostate cancer cell apoptosis in vitro and in vivo, and render reasonable optimism that statins could become an attractive anti-cancer agent.

The Role of the Transmembrane RING Finger Proteins in Cellular and Organelle Function

A large number of RING finger (RNF) proteins are present in eukaryotic cells and the majority of them are believed to act as E3 ubiquitin ligases. In humans, 49 RNF proteins are predicted to contain transmembrane domains, several of which are specifically localized to membrane compartments in the secretory and endocytic pathways, as well as to mitochondria and peroxisomes. They are thought to be molecular regulators of the organization and integrity of the functions and dynamic architecture of cellular membrane and membranous organelles. Emerging evidence has suggested that transmembrane RNF proteins control the stability, trafficking and activity of proteins that are involved in many aspects of cellular and physiological processes. This review summarizes the current knowledge of mammalian transmembrane RNF proteins, focusing on their roles and significance.

Death receptor signalling in central nervous system inflammation and demyelination

Death receptors (DRs) are members of the tumor necrosis factor receptor (TNF-R) superfamily that are characterised by the presence of a conserved intracellular death domain and are able to trigger a signalling pathway leading to apoptosis. Strong evidence suggests that DRs contribute to the pathology of tissue destructive diseases, including multiple sclerosis (MS), the most common inflammatory demyelinating disease of the central nervous system (CNS). Here, we review the evidence supporting a role for DRs in MS pathology and its implications for the development of therapeutic strategies for MS and other demyelinating pathologies of the CNS.

MicroRNA-21 protects neurons from ischemic death

MicroRNAs are small RNAs that attenuate protein expression by complementary binding to the 3'-UTR of a target mRNA. Currently, very little is known about microRNAs after cerebral ischemia. In particular, microRNA-21 (miR-21) is a strong antiapoptotic factor in some biological systems. We investigated the role of miR-21 after stroke in the rat. We employed in situ hybridization and laser capture microdissection in combination with real-time RT-PCR to investigate the expression of miR-21 after stroke. In situ hybridization revealed that miR-21 expression was upregulated in neurons of the ischemic boundary zone, and quantitative real-time RT-PCR analysis revealed that stroke increased mature miR-21 levels by approximately threefold in neurons isolated from the ischemic boundary zone by laser capture microdissection as compared with homologous contralateral neurons 2 days (n = 4; P < 0.05) and 7 days (n = 3; P < 0.05) after stroke. In vitro, overexpression of miR-21 in cultured cortical neurons substantially suppressed oxygen and glucose deprivation-induced apoptotic cell death, whereas attenuation of endogenous miR-21 by antisense inhibition exacerbated cell death after oxygen and glucose deprivation. Moreover, overexpression of miR-21 in neurons significantly reduced FASLG levels, and introduction of an miR-21 mimic into 293-HEK cells substantially reduced luciferase activity in a reporter system containing the 3'-UTR of Faslg. Our data indicate that overexpression of miR-21 protects against ischemic neuronal death, and that downregulation of FASLG, a tumor necrosis factor-α family member and an important cell death-inducing ligand whose gene is targeted by miR-21, probably mediates the neuroprotective effect. These novel findings suggest that miR-21 may be an attractive therapeutic molecule for treatment of stroke.

2-Methoxyestradiol blocks cell-cycle progression at the G2/M phase and induces apoptosis in human acute T lymphoblastic leukemia CEM cells

2-Methoxyestradiol (2-ME2) is an endogenous metabolite of 17beta-estradiol (E2) with estrogen receptor-independent anti-cancer activity. The current study sought to determine the mechanism of anti-cancer activity of 2-ME2 in human acute T lymphoblastic leukemia CEM cells. Results showed that 2-ME2 markedly suppressed proliferation of CEM cells in a time- and dose-dependent manner. 2-ME2-treated CEM cells underwent typical apoptotic changes. Exposure to 2-ME2 led to G(2)/M phase cell-cycle arrest, which preceded apoptosis characterized by the appearance of a sub-G(1) cell population. In addition, cytosolic cytochrome c release, increased procaspase-9 and -3 expressions, poly(ADP-ribose) polymerase (PARP) cleavage, and induced expression of caspase-8 were detected, suggesting that both the intrinsic apoptotic pathway and extrinsic apoptotic pathway were involved in 2-ME2-induced apoptosis. Moreover, the expression level of p21 protein was upregulated, whereas Bcl-2 and dysfunctional p53 protein were downregulated, which also contributed to 2-ME2-induced apoptosis. Our findings revealed that 2-ME2 might be a potent natural candidate for chemotherapeutic treatment of human acute T lymphoblastic leukemia when the precise effects of 2-ME2 were investigated further in other T leukemia cell lines and in primary T-cell leukemias.

Efficient production of human Fas receptor extracellular domain-human IgG1 heavy chain Fc domain fusion protein using baculovirus/silkworm expression system

The fusion protein consisting of human Fas receptor extracellular domain and human IgG1 heavy chain Fc domain (hFasRECD-Fc) is a medically important protein that potentially has therapeutic uses. The fusion gene composed of a synthetic human Fas receptor extracellular domain gene and the cDNA encoding human IgG1 heavy chain Fc domain was investigated on the secretory expression using two baculovirus systems which employed either Spodoptera frugiperda 9 (Sf9) cell line or Bombyx mori (silkworm) larvae as the host organism. Both expression systems produced the functional hFasRECD-Fc as a dimer molecule linked by disulfide bridges. The secretion level per unit volume was much higher in the case of silkworm larvae as compared to Sf9 cell line, and was estimated to be more than 150 times. A substantially pure hFasRECD-Fc sample from silkworm larvae was obtained by single step Protein G-agarose affinity column chromatography. The affinity purified sample was further fractionated by anion-exchange chromatography with the final purification yield of 22.5 mg from 26 ml hemolymph. The hFasRECD-Fc from silkworm larvae and the tag-free human Fas ligand extracellular domain derivative from Pichia pastoris formed a stable complex in solution, which was verified by size-exclusion chromatography. This study demonstrated that the baculovirus/silkworm expression system provided the means for efficient production of highly pure hFasRECD-Fc with functional activity.

The lysosome and neurodegenerative diseases

It has long been believed that the lysosome is an important digestive organelle. There is increasing evidence that the lysosome is also involved in pathogenesis of a variety of neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. Abnormal protein degradation and deposition induced by lysosomal dysfunction may be the primary contributor to age-related neurodegeneration. In this review, the possible relationship between lysosome and various neurodegenerative diseases is described.

Death receptor pathways mediate targeted and non-targeted effects of ionizing radiations in breast cancer cells

Delayed cell death by mitotic catastrophe is a frequent mode of solid tumor cell death after γ-irradiation, a widely used treatment of cancer. Whereas the mechanisms that underlie the early γ-irradiation-induced cell death are well documented, those that drive the delayed cell death are largely unknown. Here we show that the Fas, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and tumor necrosis factor (TNF)-α death receptor pathways mediate the delayed cell death observed after γ-irradiation of breast cancer cells. Early after irradiation, we observe the increased expression of Fas, TRAIL-R and TNF-R that first sensitizes cells to apoptosis. Later, the increased expression of FasL, TRAIL and TNF-α permit the apoptosis engagement linked to mitotic catastrophe. Treatments with TNF-α, TRAIL or anti-Fas antibody, early after radiation exposure, induce apoptosis, whereas the neutralization of the three death receptors pathways impairs the delayed cell death. We also show for the first time that irradiated breast cancer cells excrete soluble forms of the three ligands that can induce the death of sensitive bystander cells. Overall, these results define the molecular basis of the delayed cell death of irradiated cancer cells and identify the death receptors pathways as crucial actors in apoptosis induced by targeted as well as non-targeted effects of ionizing radiation.

FLIP as an anti-cancer therapeutic target

Suppression of apoptosis is one of the hallmarks of carcinogenesis. Tumor cells endure apoptotic pressure by overexpressing several antiapoptotic proteins, and FLICE inhibitory protein (FLIP) is one of the important antiapoptotic proteins that have been shown to be overexpressed in various primary tumor cells. FLIP has two death-effector domains in tandem, mimicking the prodomain of procaspase-8. It is recruited to Fadd in death-inducing signaling complex, thereby preventing the activation of procaspase-8. To date, three isoforms of human cytosolic FLIP (c-FLIP) and six viral homologs (v-FLIP) have been identified. Recently, the crystal structure of v-FLIP MC159 was determined for the first time as an atomic-detail FLIP structure, which revealed that two death effector domains are packed tightly against each other mainly through conserved hydrophobic interactions. The overexpression of c-FLIP in tumor cells has been shown to be the determinant of the tumor's resistance to death ligands such as FasL and TRAIL. It has also been shown that the down-regulation of c-FLIP results in sensitizing resistant tumor cells. Therefore, the agents directly targeting c-FLIP at mRNA and protein levels are expected to be developed in near future and tested for the potential as a new class of anti-cancer drugs.

Triptolide sensitizes AML cells to TRAIL-induced apoptosis via decrease of XIAP and p53-mediated increase of DR5

Acute myeloid leukemia (AML) cells are relatively resistant to tumor necrosis factor alpha-related apoptosis-inducing ligand (TRAIL). We previously reported that triptolide, a potent anticancer agent from a Chinese herb, decreases XIAP in leukemic cells. We evaluated the combination of triptolide and TRAIL and found synergistic promotion of apoptosis in AML cells. XIAP-overexpressing U937 cells (U937XIAP) were more resistant to TRAIL than U937neo cells, and inhibition of XIAP with the small-molecule inhibitor 1396-11 enhanced TRAIL-induced apoptosis, implying XIAP as a resistance factor in AML. Furthermore, triptolide increased DR5 levels in OCI-AML3, while the DR5 increase was blunted in p53-knockdown OCI-AML3 and p53-mutated U937 cells, confirming a role for p53 in the regulation of DR5. In support of this finding, disruption of MDM2-p53 binding with subsequent increase in p53 levels by nutlin3a increased DR5 levels and sensitized OCI-AML3 cells to TRAIL. The combination of 1396-11 plus nutlin3a plus TRAIL was more effective than either the 1396-11 and TRAIL or nutlin3a and TRAIL combinations in OCI-AML3 cells, further supporting the role of triptolide as a sensitizer to TRAIL-induced apoptosis in part by independent modulation of XIAP expression and p53 signaling. Thus, the combination of triptolide and TRAIL may provide a novel strategy for treating AML by overcoming critical mechanisms of apoptosis resistance.

Tissue inhibitor of metalloproteinases-3 facilitates Fas-mediated neuronal cell death following mild ischemia

Tissue inhibitor of metalloproteinase-3 (TIMP-3) is a natural inhibitor of metalloproteinases involved in matrix degradation and ectodomain shedding of many cell-surface proteins, including death receptors and/or their ligands. In the present study, we examined the role of TIMP-3 in Fas-mediated neuronal cell death following cerebral ischemia, using both gene deletion and pharmacological approaches. In culture, exposure of primary cortical neurons to 2 h of oxygen-glucose deprivation (OGD) resulted in delayed neuronal cell death that was dependent on activation of the death receptor, Fas. Cortical cultures derived from timp-3(-/-) mice displayed partial resistance against OGD-induced neuronal cell death and also displayed increased shedding of Fas ligand (FasL) into the culture media, compared to wild-type control cultures. Both the increased neuroprotection and increased FasL shedding in timp-3(-/-) cultures were reversed by addition of exogenous metalloproteinase inhibitors, recombinant TIMP-3 or GM6001. In vivo, timp-3(-/-) mice showed marked resistance to a brief (30 min) middle cerebral artery occlusion (MCAO), but were not protected against more severe lesions induced by 90 min of MCAO. These studies demonstrate that TIMP-3 facilitates Fas-mediated neuronal cell death following OGD and plays a pro-apoptotic role in mild cerebral ischemia.

Enhancement of Apo2L/TRAIL-mediated cytotoxicity in esophageal cancer cells by cisplatin

Although expressing adequate levels of functional tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptors DR4/DR5, significant proportion of cancer cells exhibit resistance to the cytotoxic effect of this ligand. Exposure of Apo2L/TRAIL-refractory cancer cells to cytotoxic chemotherapeutic agents enhances their sensitivity to Apo2L/TRAIL cytotoxicity. This study aims to elucidate the molecular mechanism responsible for the cisplatin-mediated enhancement of Apo2L/TRAIL sensitivity in cultured esophageal cancer cells. Exposure of cancer cells to sublethal concentrations of cisplatin resulted in profound potentiation of their susceptibility to Apo2L/TRAIL cytotoxicity as indicated by 2- to >20-fold reduction in Apo2L/TRAIL IC50 values. Significant activation of caspase-8, caspase-9, and caspase-3 was observed only in cells treated with cisplatin/Apo2L/TRAIL combination and not in those exposed to either agent alone. More importantly, activation of these key caspases was significantly abrogated by overexpression of Bcl2 or by the selective caspase-9 inhibitor. This observation strongly suggested that caspase-8 activation in cells treated with the cisplatin/Apo2L/TRAIL combination was secondary to the mitochondria-mediated amplification feedback loop and activation of the executioner caspase-3 was dependent on the recruitment of the intrinsic pathway characteristic of the type II cell. Profound combination-mediated cytotoxicity and induction of apoptosis was completely suppressed either by Bcl2 overexpression or by inhibition of caspase-9 activity, which conclusively pointed to the essential role of the mitochondria-dependent death signaling cascade in this process. Cisplatin sensitizes esophageal cancer cells to Apo2L/TRAIL cytotoxicity by potentiation of the mitochondria-dependent death signaling pathway that leads to amplification of caspase activation, particularly caspase-8, by the feedback loop to efficiently induce apoptosis.

The role of death receptor ligands in shaping tumor microenvironment

Death receptor ligands (FasL, TRAIL) activate apoptosis in cells expressing the cognate receptors. Evidence suggests that these ligands also deliver pro-inflammatory signals. In the tumor microenvironment, "Fas counterattack" mounted by tumors against immune cells is mediated by tumor-associated FasL. But death ligands crosslinking their receptors also induce inhibition of apoptosis and activation of the transcription factor, NFkappaB, with a subsequent burst of pro-inflammatory cytokine production and tumor growth promotion. NFkappaB, a key link between inflammation and cancer, regulates dual activities of death ligands, depending on molecular signals in the tumor microenvironment. This paper focuses on death ligands as an example of the extensive repertoire of strategies devised by tumors for escape from immune control.

Toxic epidermal necrolysis

Toxic epidermal necrolysis (TEN) is an unpredictable, life-threatening drug reaction associated with a 30% mortality. Massive keratinocyte apoptosis is the hallmark of TEN. Cytotoxic T lymphocytes appear to be the main effector cells and there is experimental evidence for involvement of both the Fas-Fas ligand and perforin/granzyme pathways. Optimal treatment for these patients remains to be clarified. Discontinuation of the offending drug and prompt referral to a burn unit are generally agreed upon steps. Beyond that, however, considerable controversy exists. Evidence both pro and con exists for the use of IVIG, systemic corticosteroid, and other measures. There is also evidence suggesting that combination therapies may be of value. All the clinical data, however, is anecdotal or based on observational or retrospective studies. Definitive answers are not yet available. Given the rarity of TEN and the large number of patients required for a study to be statistically meaningful, placebo controlled trials are logistically difficult to accomplish. The absence of an animal model further hampers research into this condition. This article reviews recent data concerning clinical presentation, pathogenesis and treatment of TEN.

LEARNING OBJECTIVES

At the conclusion of this learning activity, participants should have acquired a more comprehensive knowledge of our current understanding of the classification, clinical presentation, etiology, pathophysiology, prognosis, and treatment of TEN.

“Systemic apoptotic response” after thermal burns

The systemic pathophysiologic changes following thermal injuries affect multiple organs and body systems leading to clinical manifestations including shock, intestinal alterations, respiratory and renal failure, immunosuppression and others. Recent advances in the comprehension of mechanisms underlying systemic complications of thermal injuries have contributed to uncover part of the cellular and molecular basis that underlie such changes. Recently, programmed cell death (apoptosis) has been considered playing an important role in the development of such pathological events. Therefore, investigators utilizing animal models and clinical studies involving human primates have produced a large body of information suggesting that apoptosis is associated with most of the tissue damages triggered by severe thermal injuries. In order to draw the attention on the important role of apoptosis on systemic complications of thermal injuries, in this review we describe most of these studies, discuss possible cellular and molecular mechanisms and indicate ways to utilize them for the development of therapeutic strategies by which apoptosis may be prevented or counteracted.