Phase II trial of mapatumumab, a fully human agonist monoclonal antibody to tumor necrosis factor-related apoptosis-inducing ligand receptor 1 (TRAIL-R1), in combination with paclitaxel and carboplatin in patients with advanced non-small-cell lung cancer

Heparan sulfate promotes TRAIL-induced tumor cell apoptosis

TRAIL (TNF-related apoptosis-inducing ligand) is a potent inducer of tumor cell apoptosis through TRAIL receptors. While it has been previously pursued as a potential anti-tumor therapy, the enthusiasm subsided due to unsuccessful clinical trials and the fact that many tumors are resistant to TRAIL. In this report, we identified heparan sulfate (HS) as an important regulator of TRAIL-induced apoptosis. TRAIL binds HS with high affinity (KD = 73 nM) and HS induces TRAIL to form higher-order oligomers. The HS-binding site of TRAIL is located at the N-terminus of soluble TRAIL, which includes three basic residues. Binding to cell surface HS plays an essential role in promoting the apoptotic activity of TRAIL in both breast cancer and myeloma cells, and this promoting effect can be blocked by heparin, which is commonly administered to cancer patients. We also quantified HS content in several lines of myeloma cells and found that the cell line showing the most resistance to TRAIL has the least expression of HS, which suggests that HS expression in tumor cells could play a role in regulating sensitivity towards TRAIL. We also discovered that death receptor 5 (DR5), TRAIL, and HS can form a ternary complex and that cell surface HS plays an active role in promoting TRAIL-induced cellular internalization of DR5. Combined, our study suggests that TRAIL-HS interactions could play multiple roles in regulating the apoptotic potency of TRAIL and might be an important point of consideration when designing future TRAIL-based anti-tumor therapy.

Killer instincts: natural killer cells as multifactorial cancer immunotherapy

Natural killer (NK) cells integrate heterogeneous signals for activation and inhibition using germline-encoded receptors. These receptors are stochastically co-expressed, and their concurrent engagement and signaling can adjust the sensitivity of individual cells to putative targets. Against cancers, which mutate and evolve under therapeutic and immunologic pressure, the diversity for recognition provided by NK cells may be key to comprehensive cancer control. NK cells are already being trialled as adoptive cell therapy and targets for immunotherapeutic agents. However, strategies to leverage their naturally occurring diversity and agility have not yet been developed. In this review, we discuss the receptors and signaling pathways through which signals for activation or inhibition are generated in NK cells, focusing on their roles in cancer and potential as targets for immunotherapies. Finally, we consider the impacts of receptor co-expression and the potential to engage multiple pathways of NK cell reactivity to maximize the scope and strength of antitumor activities.

Heparan sulfate promotes TRAIL-induced tumor cell apoptosis

TRAIL (TNF-related apoptosis-inducing ligand) is a potent inducer of tumor cell apoptosis through TRAIL receptors. While it has been previously pursued as a potential anti-tumor therapy, the enthusiasm subsided due to unsuccessful clinical trials and the fact that many tumors are resistant to TRAIL. In this report we identified heparan sulfate (HS) as an important regulator of TRAIL-induced apoptosis. TRAIL binds HS with high affinity (KD = 73 nM) and HS induces TRAIL to form higher-order oligomers. The HS-binding site of TRAIL is located at the N-terminus of soluble TRAIL, which includes three basic residues. Binding to cell surface HS plays an essential role in promoting the apoptotic activity of TRAIL in both breast cancer and myeloma cells, and this promoting effect can be blocked by heparin, which is commonly administered to cancer patients. We also quantified HS content in several lines of myeloma cells and found that the cell line showing the most resistance to TRAIL has the least expression of HS, which suggests that HS expression in tumor cells could play a role in regulating sensitivity towards TRAIL. We also discovered that death receptor 5 (DR5), TRAIL and HS can form a ternary complex and that cell surface HS plays an active role in promoting TRAIL-induced cellular internalization of DR5. Combined, our study suggests that TRAIL-HS interactions could play multiple roles in regulating the apoptotic potency of TRAIL and might be an important point of consideration when designing future TRAIL-based anti-tumor therapy.

TRAIL-mediated signaling in bladder cancer: realization of clinical efficacy of TRAIL-based therapeutics in medical oncology

Bladder cancer is a therapeutically challenging disease and wealth of knowledge has enabled researchers to develop a clear understanding of mechanisms which underlie carcinogenesis and metastasis. Excitingly, research over decades has unveiled wide-ranging mechanisms which serve as central engine in progression of bladder cancer. Loss of apoptosis, drug resistance, and pro-survival signaling are some of the highly studied cellular mechanisms. Therefore, restoration of apoptosis in resistant cancers is a valuable and attractive strategy. Discovery of TRAIL-mediated signaling cascade is an intriguing facet of molecular oncology. In this review, we have provided an overview of the translational and foundational advancements in dissecting the genomic and proteomic cartography of TRAIL signaling exclusively in the context of bladder cancer. We have also summarized how different natural products sensitized drug-resistant bladder cancer cells to TRAIL-mediated apoptosis. Interestingly, different death receptors that activate agonistic antibodies have been tested in various phases of clinical trials against different cancers. Certain clues of scientific evidence have provided encouraging results about efficacy of these agonistic antibodies (lexatumumab and mapatumumab) against bladder cancer cell lines. Therefore, multipronged approaches consisting of natural products, chemotherapeutics, and agonistic antibodies will realistically and mechanistically provide proof-of-concept for the translational potential of these combinatorial strategies in well-designed clinical trials.

Nano-TRAIL: a promising path to cancer therapy

Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand, also called apo-2 ligand (TRAIL/Apo-2L), is a cytokine that triggers apoptosis by binding to TRAIL-R1 (DR4) and TRAIL-R2 (DR5) death receptors. Apoptosis occurs through either the extrinsic or intrinsic pathway. The administration of recombinant human TRAIL (rhTRAIL) or TRAIL-receptor (TRAIL-R) agonists promotes apoptosis preferentially in cancerous cells over normal cells in vitro; this phenomenon has also been observed in clinical studies. The limited efficacy of rhTRAIL in clinical trials could be attributed to drug resistance, short half-life, targeted delivery issues, and off-target toxicities. Nanoparticles are excellent drug and gene delivery systems characterized by improved permeability and retention, increased stability and biocompatibility, and precision targeting. In this review, we discuss resistance mechanisms to TRAIL and methods to overcome TRAIL resistance by using nanoparticle-based formulations developed for the delivery of TRAIL peptides, TRAIL-R agonists, and TRAIL genes to cancer cells. We also discuss combinatorial approaches of chemotherapeutic drugs with TRAIL. These studies demonstrate TRAIL's potential as an anticancer agent.

Cannabidiol regulates apoptosis and autophagy in inflammation and cancer: A review

Cannabidiol (CBD) is a terpenoid naturally found in plants. The purified compound is used in the treatment of mental disorders because of its antidepressive, anxiolytic, and antiepileptic effects. CBD can affect the regulation of several pathophysiologic processes, including autophagy, cytokine secretion, apoptosis, and innate and adaptive immune responses. However, several authors have reported contradictory findings concerning the magnitude and direction of CBD-mediated effects. For example, CBD treatment can increase, decrease, or have no significant effect on autophagy and apoptosis. These variable results can be attributed to the differences in the biological models, cell types, and CBD concentration used in these studies. This review focuses on the mechanism of regulation of autophagy and apoptosis in inflammatory response and cancer by CBD. Further, we broadly elaborated on the prospects of using CBD as an anti-inflammatory agent and in cancer therapy in the future.

Cytochalasin B-Induced Membrane Vesicles from TRAIL-Overexpressing Mesenchymal Stem Cells Induce Extrinsic Pathway of Apoptosis in Breast Cancer Mouse Model

Tumor-necrosis-factor-associated apoptosis-inducing ligand (TRAIL) is one of the most promising therapeutic cytokines that selectively induce apoptosis in tumor cells. It is known that membrane vesicles (MVs) can carry the surface markers of parental cells. Therefore, MVs are of interest as a tool for cell-free cancer therapy. In this study, membrane vesicles were isolated from TRAIL-overexpressing mesenchymal stem cells using cytochalasin B treatment (CIMVs). To evaluate the antitumor effect of CIMVs-TRAIL in vivo, a breast cancer mouse model was produced. The animals were intratumorally injected with 50 µg of native CIMVs or CIMVs-TRAIL for 12 days with an interval of two days. Then, tumor growth rate, tumor necrotic area, the expression of the apoptosis-related genes CASP8, BCL-2, and BAX and the level of CASP8 protein were analyzed. A 1.8-fold increase in the CAS8 gene mRNA and a 1.7-fold increase in the CASP8 protein level were observed in the tumors injected with CIMVs-TRAIL. The expression of the anti-apoptotic BCL-2 gene in the CIMV-TRAIL group remained unchanged, while the mRNA level of the pro-apoptotic BAX gene was increased by 1.4 times, which indicated apoptosis activation in the tumor tissue. Thus, CIMVs-TRAIL were able to activate the extrinsic apoptosis pathway and induce tumor cell death in the breast cancer mouse model.

Targeting TRAIL Death Receptors in Triple-Negative Breast Cancers: Challenges and Strategies for Cancer Therapy

The tumor necrosis factor (TNF) superfamily member TNF-related apoptosis-inducing ligand (TRAIL) induces apoptosis in cancer cells via death receptor (DR) activation with little toxicity to normal cells or tissues. The selectivity for activating apoptosis in cancer cells confers an ideal therapeutic characteristic to TRAIL, which has led to the development and clinical testing of many DR agonists. However, TRAIL/DR targeting therapies have been widely ineffective in clinical trials of various malignancies for reasons that remain poorly understood. Triple negative breast cancer (TNBC) has the worst prognosis among breast cancers. Targeting the TRAIL DR pathway has shown notable efficacy in a subset of TNBC in preclinical models but again has not shown appreciable activity in clinical trials. In this review, we will discuss the signaling components and mechanisms governing TRAIL pathway activation and clinical trial findings discussed with a focus on TNBC. Challenges and potential solutions for using DR agonists in the clinic are also discussed, including consideration of the pharmacokinetic and pharmacodynamic properties of DR agonists, patient selection by predictive biomarkers, and potential combination therapies. Moreover, recent findings on the impact of TRAIL treatment on the immune response, as well as novel strategies to address those challenges, are discussed.

Gigavalent Display of Proteins on Monodisperse Polyacrylamide Hydrogels as a Versatile Modular Platform for Functional Assays and Protein Engineering

The assembly of robust, modular biological components into complex functional systems is central to synthetic biology. Here, we apply modular "plug and play" design principles to a solid-phase protein display system that facilitates protein purification and functional assays. Specifically, we capture proteins on polyacrylamide hydrogel display beads (PHD beads) made in microfluidic droplet generators. These monodisperse PHD beads are decorated with predefined amounts of anchors, methacrylate-PEG-benzylguanine (BG) and methacrylate-PEG-chloroalkane (CA), that react covalently with SNAP-/Halo-tag fusion proteins, respectively, in a specific, orthogonal, and stable fashion. Anchors, and thus proteins, are distributed throughout the entire bead volume, allowing attachment of ∼10⁹ protein molecules per bead (⌀ 20 μm) -a higher density than achievable with commercial surface-modified beads. We showcase a diverse array of protein modules that enable the secondary capture of proteins, either noncovalently (IgG and SUMO-tag) or covalently (SpyCatcher, SpyTag, SnpCatcher, and SnpTag), in mono- and multivalent display formats. Solid-phase protein binding and enzymatic assays are carried out, and incorporating the photocleavable protein PhoCl enables the controlled release of modules via visible-light irradiation for functional assays in solution. We utilize photocleavage for valency engineering of an anti-TRAIL-R1 scFv, enhancing its apoptosis-inducing potency ∼50-fold through pentamerization.

An overview on display systems (phage, bacterial, and yeast display) for production of anticancer antibodies; advantages and disadvantages

Antibodies as ideal therapeutic and diagnostic molecules are among the top-selling drugs providing considerable efficacy in disease treatment, especially in cancer therapy. Limitations of the hybridoma technology as routine antibody generation method in conjunction with numerous developments in molecular biology led to the development of alternative approaches for the streamlined identification of most effective antibodies. In this regard, display selection technologies such as phage display, bacterial display, and yeast display have been widely promoted over the past three decades as ideal alternatives to traditional methods. The display of antibodies on phages is probably the most widespread of these methods, although surface display on bacteria or yeast have been employed successfully, as well. These methods using various sizes of combinatorial antibody libraries and different selection strategies possessing benefits in screening potency, generating, and isolation of high affinity antibodies with low risk of immunogenicity. Knowing the basics of each method assists in the design and retrieval process of antibodies suitable for different diseases, including cancer. In this review, we aim to outline the basics of each library construction and its display method, screening and selection steps. The advantages and disadvantages in comparison to alternative methods, and their applications in antibody engineering will be explained. Finally, we will review approved or non-approved therapeutic antibodies developed by employing these methods, which may serve as therapeutic antibodies in cancer therapy.

Deep exploration of immune function in EGFR wild-type and mutated lung adenocarcinomas by gene expression profiling: role of TRAIL-R2 (TNFRSF10B) in patient treatment and outcome

The tumor microenvironment is important in the initiation and progression of lung adenocarcinoma (LUAD). In this study, we aim to analyze the expression profile of immune-related genes in LUADs, examine the differential expression of immune-related genes in epidermal growth factor receptor (EGFR) wild-type and mutant LUADs, and the clinicopathologic significance of these differentially expressed genes. We used the NanoString PanCancer Immune Profiling Panel to examine 34 cases of LUADs (18 EGFR wild-type, 16 EGFR mutant). In EGFR wild-type LUADs, the macrophage and neutrophil signatures are significantly higher, and significantly higher expression of chemokines, interleukins, leukocyte, macrophage, natural killer cell, pathogen defense, Tumor necrosis factor superfamily, and transporter function signatures are also observed. TNFRSF10B mRNA was preferentially expressed in EGFR wild-type LUADs (p = 6.15e-6^, adjusted p = 0.0244). Immunohistochemical staining for TRAIL-R2 (encoded by TNFRSF10B) on 134 tissue microarray LUAD cases demonstrated strong, moderate, and weak staining in 75 (56.0%), 46 (34.3%), and 13 (9.7%) cases, respectively. Strong TRAIL-R2 expression was significantly associated with poor overall survival (OS) in all stages and EGFR wild-type LUADs, but not in EGFR-mutant tumors. Furthermore, strong TRAIL-R2 expression (p = 0.004) was an independent risk factor for poor OS. In summary, TNFRSF10B mRNA revealed significantly higher expression in EGFR wild-type LUADs, and strong TRAIL-R2 expression predicts an unfavorable prognosis for these tumors. These patients may benefit from additional treatment with TRAIL-R2 targeted therapies.

Apoptosis and Pharmacological Therapies for Targeting Thereof for Cancer Therapeutics

Apoptosis is an evolutionarily conserved sequential process of cell death to maintain a homeostatic balance between cell formation and cell death. It is a vital process for normal eukaryotic development as it contributes to the renewal of cells and tissues. Further, it plays a crucial role in the elimination of unnecessary cells through phagocytosis and prevents undesirable immune responses. Apoptosis is regulated by a complex signaling mechanism, which is driven by interactions among several protein families such as caspases, inhibitors of apoptosis proteins, B-cell lymphoma 2 (BCL-2) family proteins, and several other proteases such as perforins and granzyme. The signaling pathway consists of both pro-apoptotic and pro-survival members, which stabilize the selection of cellular survival or death. However, any aberration in this pathway can lead to abnormal cell proliferation, ultimately leading to the development of cancer, autoimmune disorders, etc. This review aims to elaborate on apoptotic signaling pathways and mechanisms, interacting members involved in signaling, and how apoptosis is associated with carcinogenesis, along with insights into targeting apoptosis for disease resolution.

Combating Cancer Stem-Like Cell-Derived Resistance to Anticancer Protein by Liposome-Mediated Acclimatization Strategy

Antibody-based therapeutics, which induce apoptosis of malignant cells by selectively binding to their receptors, hold tremendous promise for clinical cancer therapy. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has received considerable interest due to its favorable capability of activating apoptosis in cancer cells by interacting with death receptors (DRs). However, cancer stem-like cells (CSCs) show deficient or lower DR and are highly resistant to TRAIL-mediated apoptosis limiting the therapeutic efficacy. Here, we report a liposome-mediated acclimatization strategy to overcome the CSC-emanated TRAIL resistance. The liposomal assemblies coencapsulating plasmid DNA encoding TRAIL and salinomycin enable cancer cells as protein generators to express TRAIL, and more importantly, can acclimatize resistant CSCs to be sensitized to the TRAIL-triggered apoptosis by salinomycin-induced upregulation of DR expression on CSCs. This programmable liposome-based drug codelivery system shows the potential to efficiently eliminate CSCs and inhibit CSC-enriched tumor growth in the orthotopic colon tumor mouse model.

Selectively targeting myeloid-derived suppressor cells through TRAIL receptor 2 to enhance the efficacy of CAR T cell therapy for treatment of breast cancer

BACKGROUND

Successful targeting of solid tumors such as breast cancer (BC) using chimeric antigen receptor (CAR) T cells has proven challenging, largely attributed to the immunosuppressive tumor microenvironment (TME). Myeloid-derived suppressor cells (MDSCs) inhibit CAR T cell function and persistence within the breast TME. To overcome this challenge, we have developed CAR T cells targeting tumor-associated mucin 1 (MUC1) with a novel chimeric costimulatory receptor that targets tumor necrosis factor-related apoptosis-inducing ligand receptor 2 (TR2) expressed on MDSCs.

METHODS

The function of the TR2.41BB costimulatory receptor was assessed by exposing non-transduced (NT) and TR2.41BB transduced T cells to recombinant TR2, after which nuclear translocation of NFκB was measured by ELISA and western blot. The cytolytic activity of CAR.MUC1/TR2.41BB T cells was measured in a 5-hour cytotoxicity assay using MUC1+ tumor cells as targets in the presence or absence of MDSCs. In vivo antitumor activity was assessed using MDSC-enriched tumor-bearing mice treated with CAR T cells with or without TR2.41BB.

RESULTS

Nuclear translocation of NFκB in response to recombinant TR2 was detected only in TR2.41BB T cells. The presence of MDSCs diminished the cytotoxic potential of CAR.MUC1 T cells against MUC1+ BC cell lines by 25%. However, TR2.41BB expression on CAR.MUC1 T cells induced MDSC apoptosis, thereby restoring the cytotoxic activity of CAR.MUC1 T cells against MUC1+ BC lines. The presence of MDSCs resulted in an approximately twofold increase in tumor growth due to enhanced angiogenesis and fibroblast accumulation compared with mice with tumor alone. Treatment of these MDSC-enriched tumors with CAR.MUC1.TR2.41BB T cells led to superior tumor cell killing and significant reduction in tumor growth (24.54±8.55 mm³) compared with CAR.MUC1 (469.79±81.46 mm³) or TR2.41BB (434.86±64.25 mm³) T cells alone. CAR.MUC1.TR2.41BB T cells also demonstrated improved T cell proliferation and persistence at the tumor site, thereby preventing metastases. We observed similar results using CAR.HER2.TR2.41BB T cells in a HER2+ BC model.

CONCLUSIONS

Our findings demonstrate that CAR T cells that coexpress the TR2.4-1BB receptor exhibit superior antitumor potential against breast tumors containing immunosuppressive and tumor promoting MDSCs, resulting in TME remodeling and improved T cell proliferation at the tumor site.

Review of cancer cell resistance mechanisms to apoptosis and actual targeted therapies

The apoptosis pathway is a programmed cell death mechanism that is crucial for cellular and tissue homeostasis and organ development. There are three major caspase-dependent pathways of apoptosis that ultimately lead to DNA fragmentation. Cancerous cells are known to highly regulate the apoptotic pathway and its role in cancer hallmark acquisition has been discussed over the past decades. Numerous mutations in cancer cell types have been reported to be implicated in chemoresistance and treatment outcome. In this review, we summarize the mutations of the caspase-dependant apoptotic pathways that are the source of cancer development and the targeted therapies currently available or in trial.

TRAIL produced by SAM-1-activated CD4+ and CD8+ subgroup T cells induces apoptosis in human tumor cells through upregulation of death receptors

Bacterial superantigens potently activate conventional T-cells to induce massive cytokine production and mediate tumor cell death. To engineer superantigens for immunotherapy against tumors in clinic, we previously generated SAM-1, a staphylococcal enterotoxins C2 (SEC2) mutant, that exhibited significantly reduced toxicity but maintained the superantigen activity in animal models. This present study aimed to investigate whether SAM-1 activates T cells and induces apoptosis in human tumor cells. We found that SAM-1 induced the maturation of dendritic cells (DCs) with upregulating expression of the surface markers CD80, CD86 and HLA-DR, which secreted high levels of IL-12p70 by activating TLR2-NF-κB signaling pathways. SAM-1 could activate human CD4⁺ subgroup T cells and CD8⁺ subgroup T cells in the presence of mature dendritic cells (DCs), leading to the productions of cytokines TRAIL, IL-2, IFN-γ and TNF-α. We observed that TRAIL mediated the apoptosis and S-phase and G2/M-phase arrest in HGC-27 tumor cells via binding to upregulated death receptors DR4 and DR5. Using shRNA knockdown in HGC-27 cells or constitutive overexpression in ES2 cells for DR4 and DR5, we demonstrated the vital requirement of DR4 and DR5 in apoptosis of tumor cells in response to TRAIL secreted from SAM-1-activated T cells. Collectively, our results will facilitate better understanding of SAM-1-based immunotherapies for cancer.

Therapeutics Targeting the Core Apoptotic Machinery

Simple Summary

Cancer develops when the balance between cell death and cell division in tissues is dysregulated. A key focus of cancer drug discovery is identifying therapeutic agents which will selectively kill and eliminate cancer cells from the body. A number of proteins can prevent the death of cancer cells and developing inhibitors against these proteins to promote cancer cell death is a focus of recent drug discovery efforts. This review aims to summarize the key targets being explored, the drug development approaches being adopted, and the success or limitations of agents currently approved or in clinical development.

Abstract

Therapeutic targeting of the apoptotic pathways for the treatment of cancer is emerging as a valid and exciting approach in anti-cancer therapeutics. Accumulating evidence demonstrates that cancer cells are typically “addicted” to a small number of anti-apoptotic proteins for their survival, and direct targeting of these proteins could provide valuable approaches for directly killing cancer cells. Several approaches and agents are in clinical development targeting either the intrinsic mitochondrial apoptotic pathway or the extrinsic death receptor mediated pathways. In this review, we discuss the main apoptosis pathways and the key molecular targets which are the subject of several drug development approaches, the clinical development of these agents and the emerging resistance factors and combinatorial treatment approaches for this class of agents with existing and emerging novel targeted anti-cancer therapeutics.

Apoptosis-Inducing TNF Superfamily Ligands for Cancer Therapy

Cancer is a complex disease with apoptosis evasion as one of its hallmarks; therefore, apoptosis induction in transformed cells seems a promising approach as a cancer treatment. TNF apoptosis-inducing ligands, which are naturally present in the body and possess tumoricidal activity, are attractive candidates. The most studied proteins are TNF-α, FasL, and TNF-related apoptosis-inducing ligand (TRAIL). Over the years, different recombinant TNF family-derived apoptosis-inducing ligands and agonists have been designed. Their stability, specificity, and half-life have been improved because most of the TNF ligands have the disadvantages of having a short half-life and affinity to more than one receptor. Here, we review the outlook on apoptosis-inducing ligands as cancer treatments in diverse preclinical and clinical stages and summarize strategies of overcoming their natural limitations to improve their effectiveness.

Cytotoxic Efficacy and Resistance Mechanism of a TRAIL and VEGFA-Peptide Fusion Protein in Colorectal Cancer Models

TNF-related apoptosis-inducing ligand (TRAIL) is a type II transmembrane protein capable of selectively inducing apoptosis in cancer cells by binding to its cognate receptors. Here, we examined the anticancer efficacy of a recently developed chimeric AD-O51.4 protein, a TRAIL fused to the VEGFA-originating peptide. We tested AD-O51.4 protein activity against human colorectal cancer (CRC) models and investigated the resistance mechanism in the non-responsive CRC models. The quantitative comparison of apoptotic activity between AD-O51.4 and the native TRAIL in nine human colorectal cancer cell lines revealed dose-dependent toxicity in seven of them; the immunofluorescence-captured receptor abundance correlated with the extent of apoptosis. AD-O51.4 reduced the growth of CRC patient-derived xenografts (PDXs) with good efficacy. Cell lines that acquired AD-O51.4 resistance showed a significant decrease in surface TRAIL receptor expression and apoptosis-related proteins, including Caspase-8, HSP60, and p53. These results demonstrate the effectiveness of AD-O51.4 protein in CRC preclinical models and identify the potential mechanism underlying acquired resistance. Progression of AD-O51.4 to clinical trials is expected.

Revisiting the role of TRAIL/TRAIL-R in cancer biology and therapy

TNF-related apoptosis-inducing ligand (TRAIL), a member of the TNF superfamily, can induce apoptosis in cancer cells, sparing normal cells when bound to its associated death receptors (DR4/DR5). This unique mechanism makes TRAIL a potential anticancer therapeutic agent. However, clinical trials of recombinant TRAIL protein and TRAIL receptor agonist monoclonal antibodies have shown disappointing results due to its short half-life, poor pharmacokinetics and the resistance of the cancer cells. This review summarizes TRAIL-induced apoptotic and survival pathways as well as mechanisms leading to apoptotic resistance. Recent development of methods to overcome cancer cell resistance to TRAIL-induced apoptosis, such as protein modification, combination therapy and TRAIL-based gene therapy, appear promising. We also discuss the challenges and opportunities in the development of TRAIL-based therapies for the treatment of human cancers.

Phage Display Derived Monoclonal Antibodies: From Bench to Bedside

Monoclonal antibodies (mAbs) have become one of the most important classes of biopharmaceutical products, and they continue to dominate the universe of biopharmaceutical markets in terms of approval and sales. They are the most profitable single product class, where they represent six of the top ten selling drugs. At the beginning of the 1990s, an in vitro antibody selection technology known as antibody phage display was developed by John McCafferty and Sir. Gregory Winter that enabled the discovery of human antibodies for diverse applications, particularly antibody-based drugs. They created combinatorial antibody libraries on filamentous phage to be utilized for generating antigen specific antibodies in a matter of weeks. Since then, more than 70 phage–derived antibodies entered clinical studies and 14 of them have been approved. These antibodies are indicated for cancer, and non-cancer medical conditions, such as inflammatory, optical, infectious, or immunological diseases. This review will illustrate the utility of phage display as a powerful platform for therapeutic antibodies discovery and describe in detail all the approved mAbs derived from phage display.

TRAIL therapy and prospective developments for cancer treatment

Tumor Necrosis Factor (TNF) Related Apoptosis-Inducing Ligand (TRAIL), an immune cytokine of TNF-family, has received much attention in late 1990s as a potential cancer therapeutics due to its selective ability to induce apoptosis in cancer cells. TRAIL binds to cell surface death receptors, TRAIL-R1 (DR4) and TRAIL-R2 (DR5) and facilitates formation of death-inducing signaling complex (DISC), eventually activating the p53-independent apoptotic cascade. This unique mechanism makes the TRAIL a potential anticancer therapeutic especially for p53-mutated tumors. However, recombinant human TRAIL protein (rhTRAIL) and TRAIL-R agonist monoclonal antibodies (mAb) failed to exert robust anticancer activities due to inherent and/or acquired resistance, poor pharmacokinetics and weak potencies for apoptosis induction. To get TRAIL back on track as a cancer therapeutic, multiple strategies including protein modification, combinatorial approach and TRAIL gene therapy are being extensively explored. These strategies aim to enhance the half-life and bioavailability of TRAIL and synergize with TRAIL action ultimately sensitizing the resistant and non-responsive cells. We summarize emerging strategies for enhanced TRAIL therapy in this review and cover a wide range of recent technologies that will provide impetus to rejuvenate the TRAIL therapeutics in the clinical realm.

Targeting apoptosis in cancer therapy

For over three decades, a mainstay and goal of clinical oncology has been the development of therapies promoting the effective elimination of cancer cells by apoptosis. This programmed cell death process is mediated by several signalling pathways (referred to as intrinsic and extrinsic) triggered by multiple factors, including cellular stress, DNA damage and immune surveillance. The interaction of apoptosis pathways with other signalling mechanisms can also affect cell death. The clinical translation of effective pro-apoptotic agents involves drug discovery studies (addressing the bioavailability, stability, tumour penetration, toxicity profile in non-malignant tissues, drug interactions and off-target effects) as well as an understanding of tumour biology (including heterogeneity and evolution of resistant clones). While tumour cell death can result in response to therapy, the selection, growth and dissemination of resistant cells can ultimately be fatal. In this Review, we present the main apoptosis pathways and other signalling pathways that interact with them, and discuss actionable molecular targets, therapeutic agents in clinical translation and known mechanisms of resistance to these agents.

Mechanisms of Apoptosis Resistance to NK Cell-Mediated Cytotoxicity in Cancer

Natural killer (NK) cells are major contributors to immunosurveillance and control of tumor development by inducing apoptosis of malignant cells. Among the main mechanisms involved in NK cell-mediated cytotoxicity, the death receptor pathway and the release of granules containing perforin/granzymes stand out due to their efficacy in eliminating tumor cells. However, accumulated evidence suggest a profound immune suppression in the context of tumor progression affecting effector cells, such as NK cells, leading to decreased cytotoxicity. This diminished capability, together with the development of resistance to apoptosis by cancer cells, favor the loss of immunogenicity and promote immunosuppression, thus partially inducing NK cell-mediated killing resistance. Altered expression patterns of pro- and anti-apoptotic proteins along with genetic background comprise the main mechanisms of resistance to NK cell-related apoptosis. Herein, we summarize the main effector cytotoxic mechanisms against tumor cells, as well as the major resistance strategies acquired by tumor cells that hamper the extrinsic and intrinsic apoptotic pathways related to NK cell-mediated killing.

Phage Display Derived Monoclonal Antibodies: From Bench to Bedside

Monoclonal antibodies (mAbs) have become one of the most important classes of biopharmaceutical products, and they continue to dominate the universe of biopharmaceutical markets in terms of approval and sales. They are the most profitable single product class, where they represent six of the top ten selling drugs. At the beginning of the 1990s, an in vitro antibody selection technology known as antibody phage display was developed by John McCafferty and Sir. Gregory Winter that enabled the discovery of human antibodies for diverse applications, particularly antibody-based drugs. They created combinatorial antibody libraries on filamentous phage to be utilized for generating antigen specific antibodies in a matter of weeks. Since then, more than 70 phage-derived antibodies entered clinical studies and 14 of them have been approved. These antibodies are indicated for cancer, and non-cancer medical conditions, such as inflammatory, optical, infectious, or immunological diseases. This review will illustrate the utility of phage display as a powerful platform for therapeutic antibodies discovery and describe in detail all the approved mAbs derived from phage display.

Oxidative stress-driven DR5 upregulation restores TRAIL/Apo2L sensitivity induced by iron oxide nanoparticles in colorectal cancer

There exists an emergency clinical demand to overcome TRAIL/Apo2L (tumor necrosis factor-related apoptosis-inducing ligand) resistance, which is a major obstacle attributed to insufficient level or mutation of TRAIL receptors. Here, we developed an iron oxide cluster-based nanoplatform for both sensitization and MR image-guided evaluation to improve TRAIL/Apo2L efficacy in colorectal cancer, which has an inadequate response to TRAIL/Apo2L or chemotherapy. Specifically, NanoTRAIL (TRAIL/Apo2L-iron oxide nanoparticles) generated ROS (reactive oxygen species)-triggered JNK (c-Jun N-terminal kinase) activation and induced subsequent autophagy-assisted DR5 upregulation, resulting in a significant enhanced antitumor efficacy of TRAIL/Apo2L, which confirmed in both TRAIL-resistant HT-29, intermediately resistant SW-480 and sensitive HCT-116 cells. Furthermore, in a subcutaneous colorectal cancer mouse model, the in vivo tumor retention of NanoTRAIL can be demonstrated by MR T₂ weighted contrast imaging, and NanoTRAIL significantly suppressed tumor growth and prolonged the survival time without observable adverse effects compared with control and TRAIL/Apo2L monotherapy. Importantly, in the study of colorectal cancer patient-derived xenograft models, we found that the NanoTRAIL treatment could significantly improve the survival outcome with consistent ROS-dependent autophagy-assisted DR5 upregulation and tumor apoptosis. Our results describe a transformative design that can be applied clinically to sensitize Apo2L/TRAIL-resistant patients using FDA-approved iron oxide nanoparticles.

The TRAIL to cancer therapy: Hindrances and potential solutions

Apoptosis is an ordered and orchestrated cellular process that occurs in physiological and pathological conditions. Resistance to apoptosis is a hallmark of virtually all malignancies. Despite being a cause of pathological conditions, apoptosis could be a promising target in cancer treatment. Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), also known as Apo-2 ligand (Apo2L), is a member of TNF cytokine superfamily. It is a potent anti-cancer agent owing to its specific targeting towards cancerous cells, while sparing normal cells, to induce apoptosis. However, resistance occurs either intrinsically or after multiple treatments which may explain why cancer therapy fails. This review summarizes the apoptotic mechanisms via extrinsic and intrinsic apoptotic pathways, as well as the apoptotic resistance mechanisms. It also reviews the current clinically tested recombinant human TRAIL (rhTRAIL) and TRAIL receptor agonists (TRAs) against TRAIL-Receptors, TRAIL-R1 and TRAIL-R2, in which the outcomes of the clinical trials have not been satisfactory. Finally, this review discusses the current strategies in overcoming resistance to TRAIL-induced apoptosis in pre-clinical and clinical settings.

Novel Apoptosis-Inducing Agents for the Treatment of Cancer, a New Arsenal in the Toolbox

Evasion from apoptosis is an important hallmark of cancer cells. Alterations of apoptosis pathways are especially critical as they confer resistance to conventional anti-cancer therapeutics, e.g., chemotherapy, radiotherapy, and targeted therapeutics. Thus, successful induction of apoptosis using novel therapeutics may be a key strategy for preventing recurrence and metastasis. Inhibitors of anti-apoptotic molecules and enhancers of pro-apoptotic molecules are being actively developed for hematologic malignancies and solid tumors in particular over the last decade. However, due to the complicated apoptosis process caused by a multifaceted connection with cross-talk pathways, protein–protein interaction, and diverse resistance mechanisms, drug development within the category has been extremely challenging. Careful design and development of clinical trials incorporating predictive biomarkers along with novel apoptosis-inducing agents based on rational combination strategies are needed to ensure the successful development of these molecules. Here, we review the landscape of currently available direct apoptosis-targeting agents in clinical development for cancer treatment and update the related biomarker advancement to detect and validate the efficacy of apoptosis-targeted therapies, along with strategies to combine them with other agents.

Developing TRAIL/TRAIL death receptor-based cancer therapies

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

Antitumor Effect of Periplocin in TRAIL-Resistant gastric cancer cells via upregulation of death receptor through activating ERK1/2-EGR1 pathway

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), a member of the tumor necrosis factor family, induces apoptosis in a variety of cancer cells. However, gastric cancer (GC) cells are insensitive to TRAIL usually. In the previous study, we showed that Periplocin could induce apoptosis in GC cells via the activation of ERK1/2-EGR1 pathway. In the present study, we have shown that the combination of Periplocin and TRAIL had a greater inhibitory effect on gastric cancer cell viability in vitro and in vivo than Periplocin or TRAIL alone. Through upregulating the expression of DR4 and DR5 at transcriptional and protein levels, Periplocin enhanced the sensitivity of gastric cancer cells to TRAIL. Furthermore, enhanced activity of ERK1/2-EGR1 pathway was responsible for upregulating of DR4 and DR5 uponPeriplocin treatment, subsequently reducing the expression of Mcl-1 and Bcl2 and activating Bid and caspase-3/8. Collectively, these data implied that Periplocin might act as a sensitizer of TRAIL and could be a potential strategy for the treatment of GC.

Suppression of SOCS3 enhances TRAIL-induced cell growth inhibition through the upregulation of DR4 expression in renal cell carcinoma cells

Background

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a tumor-selective apoptosis inducer that is expressed in natural killer cells, whose cytotoxicity is activated by interferon (IFN). We investigated the effect of suppressor of cytokine signaling (SOCS) 3 on the expression of TRAIL receptors (DR4) and on TRAIL sensitivity in renal cell carcinoma (RCC) cells.

Methods

Vector expression, RNA interference and IL-6 receptor antibody tocilizumab were used to investigate the functional role of SOCS3 in DR4 expression. Immunoprecipitation was employed to detect the biochemical interaction between SOCS3 and DR4. The expression of DR4 induced by combination with IFN-α and tocilizumab was also examined by immunohistochemical staining using mice xenograft model.

Results

DR4 expression was up-regulated by IFN stimulation in RCC cells. 786-O cells were resistant to TRAIL and showed higher SOCS3 expression. ACHN cells showed higher DR4 expression and lower SOCS3 expression. Suppression of SOCS3 up-regulated DR4 expression and enhanced the TRAIL sensitivity in 786-O cells. In ACHN cells, DR4 expression was down-regulated by transfection with pCI-SOCS3, and the cells became resistant to TRAIL. Immunoprecipitation revealed the biochemical interaction between SOCS3 and DR4. A marked increase in IFN-induced DR4 protein expression after tocilizumab treatment was observed by immunohistochemical staining in the tumor from the mice xenograft model.

Conclusions

Our results indicate that IFN and SOCS3 regulate DR4 expression in RCC cells. Combination therapy with IFN-α, tocilizumab and an anti-DR4 agonistic ligand appears to effectively inhibit advanced RCC cell growth.

Restoring the switch for cancer cell death: Targeting the apoptosis signaling pathway

PURPOSE

The relevance of apoptosis to cancer development and pharmacologic agents that target this pathway in selected malignancies are described.

SUMMARY

Apoptosis is a tightly regulated biological process mediated by both proapoptotic (i.e., prodeath) and antiapoptotic (i.e., prosurvival) proteins. While apoptosis represents a well-established effector mechanism induced by conventional chemotherapy in many malignancies, the development of apoptosis-based targeted therapy is relatively new. The pharmacologic restoration of apoptotic functions, either by blocking the action of antiapoptotic proteins/regulators (e.g., through investigational therapies such as inhibitors of apoptosis proteins, SMAC [second mitochondria-derived activator of caspases] mimetics, MDM2 [murine double minute 2] antagonists) or by inducing apoptosis (e.g., through investigational agonistic monoclonal antibodies or fusion proteins), holds robust potential for cancer pharmacotherapy. Notably, BH domain 3 (BH3) mimetics, a new class of small molecules that block the action antiapoptotic proteins, are touted a success for apoptosis-based targeted therapy. Venetoclax, a synthetic peptide that belongs to this class of BH3 mimetics, is currently approved by the Food and Drug Administration for the treatment of relapsed/refractory chronic lymphocytic leukemia in patients with 17p deletion as a single agent. This agent has been increasingly used either alone or as part of combination therapy for diverse hematologic malignancies in clinical trials.

CONCLUSION

Advances in the understanding of molecular mechanisms of apoptosis have given rise to more-refined targeted therapies for diverse malignancies, with the goal to improve survival outcome while sparing treatment-related toxicities.

Combined application of Embelin and tumor necrosis factor-related apoptosis-inducing ligand inhibits proliferation and invasion in osteosarcoma cells via caspase-induced apoptosis

Embelin, as an inhibitor of the X-linked inhibitor of apoptosis protein (XIAP), may induce apoptosis in various types of cancer cells. The present study aimed to determine the effect of Embelin on the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis of osteosarcoma cells. Embelin and TRAIL were applied to U2OS and MG63 cells, respectively or in combination. MTT was initially used to detect the difference in survival rates between the group receiving combined application of 100 ng/ml TRAIL and 20 µmol/l Embelin and the individual application groups. Light microscopic quantification was used to detect the morphology of the osteosarcoma cells in each group. Determination of cell apoptosis was subsequently performed using flow cytometry. The invasive ability of the cells was detected by a Transwell assay, prior to relative protein expression being determined by western blot analysis. Based on all the test data, it was revealed that the survival rates and the invasive ability were significantly lower following the combined application of 100 ng/ml TRAIL and 20 µmol/l Embelin than following the individual application of either (P<0.01). Additionally, upregulating expression of caspases, as well as death receptor 5, and downregulating expression of XIAP and matrix metalloproteinase 9 (MMP-9), had more significant effects in the combined group compared with the individual group and the control group. All these results suggested that Embelin may enhance TRAIL-induced apoptosis and inhibit the invasion of human osteosarcoma cells.

Nanoparticles for Immune Cytokine TRAIL-Based Cancer Therapy

The immune cytokine tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has received significant attention as a cancer therapeutic due to its ability to selectively trigger cancer cell apoptosis without causing toxicity in vivo. While TRAIL has demonstrated significant promise in preclinical studies in mice as a cancer therapeutic, challenges including poor circulation half-life, inefficient delivery to target sites, and TRAIL resistance have hindered clinical translation. Recent advances in drug delivery, materials science, and nanotechnology are now being exploited to develop next-generation nanoparticle platforms to overcome barriers to TRAIL therapeutic delivery. Here, we review the design and implementation of nanoparticles to enhance TRAIL-based cancer therapy. The platforms we discuss are diverse in their approaches to the delivery problem and provide valuable insight into guiding the design of future nanoparticle-based TRAIL cancer therapeutics to potentially enable future translation into the clinic.

Loss of functional BAP1 augments sensitivity to TRAIL in cancer cells

Malignant mesothelioma (MM) is poorly responsive to systemic cytotoxic chemotherapy and invariably fatal. Here we describe a screen of 94 drugs in 15 exome-sequenced MM lines and the discovery of a subset defined by loss of function of the nuclear deubiquitinase BRCA associated protein-1 (BAP1) that demonstrate heightened sensitivity to TRAIL (tumour necrosis factor-related apoptosis-inducing ligand). This association is observed across human early passage MM cultures, mouse xenografts and human tumour explants. We demonstrate that BAP1 deubiquitinase activity and its association with ASXL1 to form the Polycomb repressive deubiquitinase complex (PR-DUB) impacts TRAIL sensitivity implicating transcriptional modulation as an underlying mechanism. Death receptor agonists are well-tolerated anti-cancer agents demonstrating limited therapeutic benefit in trials without a targeting biomarker. We identify BAP1 loss-of-function mutations, which are frequent in MM, as a potential genomic stratification tool for TRAIL sensitivity with immediate and actionable therapeutic implications.

Antibodies and Derivatives Targeting DR4 and DR5 for Cancer Therapy

Developing therapeutics that induce apoptosis in cancer cells has become an increasingly attractive approach for the past 30 years. The discovery of tumor necrosis factor (TNF) superfamily members and more specifically TNF-related apoptosis-inducing ligand (TRAIL), the only cytokine of the family capable of eradicating selectively cancer cells, led to the development of numerous TRAIL derivatives targeting death receptor 4 (DR4) and death receptor 5 (DR5) for cancer therapy. With a few exceptions, preliminary attempts to use recombinant TRAIL, agonistic antibodies, or derivatives to target TRAIL agonist receptors in the clinic have been fairly disappointing. Nonetheless, a tremendous effort, worldwide, is being put into the development of novel strategic options to target TRAIL receptors. Antibodies and derivatives allow for the design of novel and efficient agonists. We summarize and discuss here the advantages and drawbacks of the soar of TRAIL therapeutics, from the first developments to the next generation of agonistic products, with a particular insight on new concepts.

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

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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

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

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

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

[Thioridazine Sensitizes Apoptotic Effect of TRAIL in Human Lung Cancer PC9 Cells Through ER Stress Mediated Up-regulation of DR5]

背景与目的

肿瘤坏死因子相关凋亡诱导配体（tumor necrosis factor-related apoptosis-inducting ligand, TRAIL）可诱导肿瘤细胞发生凋亡，然而相当数量的肿瘤细胞可耐受TRAIL诱导的凋亡而得以存活。本实验观察硫利达嗪（thioridazine, THZ）通过诱导内质网应激（endoplasmic reticulum stress, ER stress）介导的死亡受体5（death receptor 5, DR5）表达上调，继而增敏TRAIL对肺腺癌细胞PC9的生长抑制及凋亡诱导效应，探讨其机制。

方法

不同浓度硫利达嗪及TRAIL单独或联合处理PC9细胞，MTT法检测细胞活性变化，流式细胞术检测细胞表面DR5表达及细胞凋亡率，Western blotting检测内质网应激相关蛋白GRP78（glucose regulated protein 78）、C/EBP环磷酸腺苷反应元件结合转录因子同源蛋白（C/EBP homologous protein, CHOP）、p-PERK（PKR-like ER kinase）、p-eIF2α（eukaryotic initiation factor-2α, eIF2α）、ATF4（activating transcription factor 4, ATF4）及凋亡相关蛋白Caspase-3、Caspase-9、Caspase-8、PARP、DR5表达变化。

结果

硫利达嗪对PC9细胞的增殖抑制效应呈浓度依赖性（P < 0.05），硫利达嗪可增加TRAIL对PC9细胞的抑制作用及凋亡诱导作用且可上调PC9细胞表面DR5表达水平，流式细胞术结果显示：TRAIL联合硫利达嗪组细胞凋亡率较单独TRAIL组显著增加（P < 0.05），Western blotting结果显示：TRAIL联合硫利达嗪组细胞Cleaved-caspase-8、Cleaved-PARP、DR5表达水平较单独TRAIL组明显上调。DR5表达上调及促凋亡效应是通过诱导内质网应激发生，并伴随着GRP78及CHOP表达上调发生的，且该效应可被4-苯基丁酸（4-phenylbutyric acid, 4-PBA）可抑制（P < 0.05）。

结论

硫利达嗪增敏TRAIL对PC9细胞的增殖抑制效应显著，其机制可能与硫利达嗪内质网应激介导的DR5上调有关。

A Genome-Wide Loss-of-Function Screen Identifies SLC26A2 as a Novel Mediator of TRAIL Resistance

TRAIL is a potent death-inducing ligand that mediates apoptosis through the extrinsic pathway and serves as an important endogenous tumor suppressor mechanism. Because tumor cells are often killed by TRAIL and normal cells are not, drugs that activate the TRAIL pathway have been thought to have potential clinical value. However, to date, most TRAIL-related clinical trials have largely failed due to the tumor cells having intrinsic or acquired resistance to TRAIL-induced apoptosis. Previous studies to identify resistance mechanisms have focused on targeted analysis of the canonical apoptosis pathway and other known regulators of TRAIL receptor signaling. To identify novel mechanisms of TRAIL resistance in an unbiased way, we performed a genome-wide shRNA screen for genes that regulate TRAIL sensitivity in sublines that had been selected for acquired TRAIL resistance. This screen identified previously unknown mediators of TRAIL resistance including angiotensin II receptor 2, Crk-like protein, T-Box Transcription Factor 2, and solute carrier family 26 member 2 (SLC26A2). SLC26A2 downregulates the TRAIL receptors, DR4 and DR5, and this downregulation is associated with resistance to TRAIL. Its expression is high in numerous tumor types compared with normal cells, and in breast cancer, SLC26A2 is associated with a significant decrease in relapse-free survival.Implication: Our results shed light on novel resistance mechanisms that could affect the efficacy of TRAIL agonist therapies and highlight the possibility of using these proteins as biomarkers to identify TRAIL-resistant tumors, or as potential therapeutic targets in combination with TRAIL. Mol Cancer Res; 15(4); 382-94. ©2017 AACR.

hvTRA, a novel TRAIL receptor agonist, induces apoptosis and sustained growth retardation in melanoma

In recent years, new treatment options for malignant melanoma patients have enhanced the overall survival for selected patients. Despite new hope, most melanoma patients still relapse with drug-resistant tumors or experience intrinsic resistance to the therapy. Therefore, novel treatment modalities beneficial for subgroups of patients are needed. TRAIL receptor agonists have been suggested as promising candidates for use in cancer treatment as they preferentially induce apoptosis in cancer cells. Unfortunately, the first generation of TRAIL receptor agonists showed poor clinical efficacy. hvTRA is a second-generation TRAIL receptor agonist with improved composition giving increased potency, and in the present study, we showed hvTRA-induced activation of apoptosis leading to an efficient and sustained reduction in melanoma cell growth in cell lines and xenograft models. Furthermore, the potential of hvTRA in a clinical setting was demonstrated by showing efficacy on tumor cells harvested from melanoma patients with lymph node metastasis in an ex vivo drug sensitivity assay. Inhibition of mutated BRAF has been shown to regulate proteins in the intrinsic apoptotic pathway, making the cells more susceptible for apoptosis induction. In an attempt to increase the efficacy of hvTRA, combination treatment with the mutated BRAF inhibitor vemurafenib was investigated. A synergistic effect by the combination was observed for several cell lines in vitro, and an initial cytotoxic effect was observed in vivo. Unfortunately, the initial increased reduction in tumor growth compared with hvTRA mono treatment was not sustained, and this was related to downregulation of the DR5 level by vemurafenib. Altogether, the presented data imply that hvTRA efficiently induce apoptosis and growth delay in melanoma models and patient material, and the potential of this TRAIL receptor agonist should be further evaluated for treatment of subgroups of melanoma patients.

TRAIL (TNF-related apoptosis-inducing ligand) inhibits human adipocyte differentiation via caspase-mediated downregulation of adipogenic transcription factors

Tumor necrosis factor-α (TNFα) and other ligands of the TNF superfamily are potent regulators of adipose tissue metabolism and play a crucial role in the obesity-induced inflammation of adipose tissue. Adipose tissue expression levels of TRAIL (TNF-related apoptosis-inducing ligand) and its receptor were shown to be upregulated by overfeeding and decreased by fasting in mice. In the present study we aimed to elucidate the impact of TRAIL on adipogenesis. To this end, human Simpson-Golabi-Behmel syndrome (SGBS) preadipocytes as well as stromal-vascular cells isolated from human white adipose tissue were used as model systems. Human recombinant TRAIL inhibited adipogenic differentiation in a dose-dependent manner. It activated the cleavage of caspase-8 and -3, which in turn resulted in a downregulation of the key adipogenic transcription factors C/EBPα, C/EBPδ, and PPARγ. The effect was completely blocked by pharmacological or genetic inhibition of caspases. Taken together we discovered a so far unrecognized function of TRAIL in the regulation of adipogenesis. Targeting the TRAIL/TRAIL receptor system might provide a novel strategy to interfere with adipose tissue homeostasis.

The fibronectin III-1 domain activates a PI3-Kinase/Akt signaling pathway leading to αvβ5 integrin activation and TRAIL resistance in human lung cancer cells

Background

Fibronectin is a mechanically sensitive protein which is organized in the extracellular matrix as a network of interacting fibrils. The lung tumor stroma is enriched for fibronectin which is thought to contribute to metastasis and drug resistance. Fibronectin is an elastic, multi-modular protein made up of individually folded domains, some of which can stretch in response to increased mechanical tension. Very little is known about the relationship of fibronectin’s unfolded domains to lung cancer resistance to chemotherapy. In the present study, we evaluated the impact of unfolding the first Type III domain of fibronectin (FnIII-1c) on TNF-related apoptosis inducing ligand (TRAIL) resistance.

Methods

NCI-H460 non-small cell lung cancer cells were treated with FnIII-1c then assessed for TRAIL-induced apoptosis. Subsequent analysis of FnIII-1c-mediated signaling pathways was also completed. Human non-small cell lung cancer tissue sections were assessed for the expression of vitronectin by immunohistochemistry.

Results

FnIII-1c inhibited TRAIL-induced activation of caspase 8 and subsequent apoptosis in NCI-H460 lung cancer cells. FnIII-1c treatment was associated with the activation of the phosphatidylinositol-3-kinase/alpha serine/threonine kinase (PI3K/Akt) pathway and the αvβ5 integrin receptor for vitronectin, both of which were required for TRAIL resistance. Immunohistochemical staining of sections from non-small cell lung cancers showed that vitronectin was localized around blood vessels and in the tumor-stroma interface.

Conclusions

Unfolding of Type III domains within the fibronectin matrix may promote TRAIL resistance through the activation of a PI3K/Akt/αvβ5 signaling axis and point to a novel mechanism by which changes in secondary structure of fibronectin contribute to cancer cell resistance to apoptosis.

Antidrug Antibody Formation in Oncology: Clinical Relevance and Challenges

: In oncology, an increasing number of targeted anticancer agents and immunotherapies are of biological origin. These biological drugs may trigger immune responses that lead to the formation of antidrug antibodies (ADAs). ADAs are directed against immunogenic parts of the drug and may affect efficacy and safety. In other medical fields, such as rheumatology and hematology, the relevance of ADA formation is well established. However, the relevance of ADAs in oncology is just starting to be recognized, and literature on this topic is scarce. In an attempt to fill this gap in the literature, we provide an up-to-date status of ADA formation in oncology. In this focused review, data on ADAs was extracted from 81 clinical trials with biological anticancer agents. We found that most biological anticancer drugs in these trials are immunogenic and induce ADAs (63%). However, it is difficult to establish the clinical relevance of these ADAs. In order to determine this relevance, the possible effects of ADAs on pharmacokinetics, efficacy, and safety parameters need to be investigated. Our data show that this was done in fewer than 50% of the trials. In addition, we describe the incidence and consequences of ADAs for registered agents. We highlight the challenges in ADA detection and argue for the importance of validating, standardizing, and describing well the used assays. Finally, we discuss prevention strategies such as immunosuppression and regimen adaptations. We encourage the launch of clinical trials that explore these strategies in oncology.

IMPLICATIONS FOR PRACTICE

Because of the increasing use of biologicals in oncology, many patients are at risk of developing antidrug antibodies (ADAs) during therapy. Although clinical consequences are uncertain, ADAs may affect pharmacokinetics, patient safety, and treatment efficacy. ADA detection and reporting is currently highly inconsistent, which makes it difficult to evaluate the clinical consequences. Standardized reporting of ADA investigations in the context of the aforementioned parameters is critical to understanding the relevance of ADA formation for each drug. Furthermore, the development of trials that specifically aim to investigate clinical prevention strategies in oncology is needed.

TRAIL-receptor 1 IgM antibodies strongly induce apoptosis in human cancer cells in vitro and in vivo

Agonistic tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL)-receptor-specific antibodies are attractive antitumor therapeutics. Recently, our group has generated several human monoclonal antibodies (mAbs) to TRAIL-receptor-1 (TRAIL-R1) (TR1-IgGs) using ISAAC technology. However, these TR1-IgGs did not demonstrate ideal apoptosis-inducing capacity in the absence of additional antibodies. To overcome this limitation, we class-switched the TR1-IgGs to TRAIL-R1 IgM antibodies (TR1-IgMs); TR1-IgMs might possess high valency and facilitate the crosslinking of the cell surface receptors. We showed that the TR1-IgMs bound TRAIL-R1, activated the caspase signal, and induced strong apoptosis (100-fold higher compared with the IgG form in one case) in human tumor cell lines without any additional crosslinking in vitro. We further demonstrated that these TR1-IgMs dramatically inhibited tumor growth in a xenograft model through the caspase activation cascade. These data suggest that TR1-IgMs may become potential immunotherapeutic agents for cancer therapy.

TNF-Related Apoptosis-Inducing Ligand (TRAIL)-Armed Exosomes Deliver Proapoptotic Signals to Tumor Site

PURPOSE

Exosomes deliver signals to target cells and could thus be exploited as an innovative therapeutic tool. We investigated the ability of membrane TRAIL-armed exosomes to deliver proapoptotic signals to cancer cells and mediate growth inhibition in different tumor models.

EXPERIMENTAL METHODS AND RESULTS

K562 cells, transduced with lentiviral human membrane TRAIL, were used for the production of TRAIL(+) exosomes, which were studied by nanoparticle tracking analysis, cytofluorimetry, immunoelectronmicroscopy, Western blot, and ELISA. In vitro, TRAIL(+) exosomes induced more pronounced apoptosis (detected by Annexin V/propidium iodide and activated caspase-3) in TRAIL-death receptor (DR)5(+) cells (SUDHL4 lymphoma and INT12 melanoma), with respect to the DR5(-)DR4(+)KMS11 multiple myeloma. Intratumor injection of TRAIL(+) exosomes, but not mock exosomes, induced growth inhibition of SUDHL4 (68%) and INT12 (51%), and necrosis in KMS11 tumors. After rapid blood clearance, systemically administered TRAIL(+) exosomes accumulated in the liver, lungs, and spleen and homed to the tumor site, leading to a significant reduction of tumor growth (58%) in SUDHL4-bearing mice. The treatment of INT12-bearing animals promoted tumor necrosis and a not statistically significant tumor volume reduction. In KMS11-bearing mice, despite massive perivascular necrosis, no significant tumor growth inhibition was detected.

CONCLUSIONS

TRAIL-armed exosomes can induce apoptosis in cancer cells and control tumor progression in vivo Therapeutic efficacy was particularly evident in intratumor setting, while depended on tumor model upon systemic administration. Thanks to their ability to deliver multiple signals, exosomes thus represent a promising therapeutic tool in cancer. Clin Cancer Res; 22(14); 3499-512. ©2016 AACR.