To TNF-related Apoptosis-inducing Ligand Research Articles

The Curcuminoid EF24 in Combination with TRAIL Reduces Human Renal Cancer Cell Migration by Decreasing MMP-2/MMP-9 Activity through a Reduction in H2O2.

Cancer cells present high levels of oxidative stress, and although an increase in reactive oxygen species (ROS), such as H2O2, can lead to apoptosis, it can also induce cell invasion and metastasis. As the increase in ROS can lead to an increase in the expression of MMP-2 and MMP-9, thus causing the degradation of the extracellular matrix, an increase in the ROS H2O2 might have an impact on MMP-2/MMP-9 activity. The natural compound curcumin has shown some anticancer effects, although its bioavailability hinders its therapeutic potential. However, curcumin and its analogues were shown to resensitize kidney cancer cells to TNF-related apoptosis-inducing ligand (TRAIL)-induced apoptosis. This study shows that the curcuminoid EF24 in combination with TRAIL increases peroxidase activity in the renal adenocarcinoma cell line ACHN, reducing the level of intracellular H2O2 and MMP-2/MMP-9 activity, a mechanism that is also observed after treatment with curcumin and TRAIL.

NSAIDs-induced oxidative stress sensitizes tumor cells to T cell cytotoxicity through the TRAIL-DR5 axis

Abstract Adoptive T cell therapy (ACT) has shown promising therapeutic outcomes in patients with hematological malignancies. However, the success of ACT is limited to a small fraction of treated patients. Hence, developing new strategies to enhance the potency of ACT are urgently needed for better therapeutic outcomes. Our previous study demonstrated that inducing oxidative stress in tumor cells is critically involved in tumor rejection by ACT. In the current study, we report that indomethacin, a prototypical non-steroidal anti-inflammatory drug (NSAID), can intensify ROS in tumor cells and sensitize them to ACT. Mechanistically, our data indicate that indomethacin treatment leads to enhanced expression of death receptor 5 (DR5) in tumor cells, rendering them more susceptible to TNF-related apoptosis-inducing ligand (TRAIL)-induced cell death. We found that tumor-specific T cells upregulated TRAIL expression upon adoptive transfer. Using genetic-based approaches, we showed that DR5-deficient tumor cells were unresponsive to the beneficial effect of indomethacin, while overexpressing TRAIL in donor T cells led to further improvement in mouse survival. Collectively, our study demonstrates that the pro-oxidative feature of selected NSAIDs can be exploited to augment the efficacy of T cell therapy. Our findings provide a strong rationale for targeting tumor redox to achieve more effective tumor destruction through the combination of pro-oxidants and ACT.

β-Thujaplicin Enhances TRAIL-Induced Apoptosis via the Dual Effects of XIAP Inhibition and Degradation in NCI-H460 Human Lung Cancer Cells.

Background: β-thujaplicin, a natural tropolone derivative, has anticancer effects on various cancer cells via apoptosis. However, the apoptosis regulatory proteins involved in this process have yet to be revealed. Methods: Trypan blue staining, a WST-8 assay, and a caspase-3/7 activity assay were used to investigate whether β-thujaplicin sensitizes cancer cells to TNF-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis. Additionally, western blotting was performed to clarify the effects of β-thujaplicin on X-linked inhibitor of apoptosis protein (XIAP) in NCI-H460 cells and a fluorescence polarization binding assay was used to evaluate the binding-inhibitory activity of β-thujaplicin against XIAP-BIR3. Results: β- and γ-thujaplicins decreased the viability of NCI-H460 cells in a dose-dependent manner; they also sensitized the cells to TRAIL-induced cell growth inhibition and apoptosis. β-thujaplicin significantly potentiated the apoptosis induction effect of TRAIL on NCI-H460 cells, which was accompanied by enhanced caspase-3/7 activity. Interestingly, β-thujaplicin treatment in NCI-H460 cells decreased XIAP levels. Furthermore, β-thujaplicin was able to bind XIAP-BIR3 at the Smac binding site. Conclusions: These findings indicate that β-thujaplicin could enhance TRAIL-induced apoptosis in NCI-H460 cells via XIAP inhibition and degradation. Thus, the tropolone scaffold may be useful for designing novel nonpeptidic small-molecule inhibitors of XIAP and developing new types of anticancer drugs.

CD13 inhibition augments DR4-induced tumor cell death in a p-ERK1/2-independent manner.

Objective:Death receptor 4 (DR4; TRAIL-R1) critically mediates extrinsic apoptosis cascades via binding to TNF-related apoptosis-inducing ligand (TRAIL). However, intrinsic and/or acquired resistance are observed in the clinical application of TRAIL. The aim of this study was to investigate the function and molecular mechanism of CD13 in the TRAIL/DR4 pathway against tumor cells, and provide a new strategy for improving therapeutic efficacy or overcoming TRAIL-resistance.Methods:TRAIL protein was expressed as a secretory protein in a Pichia pastoris expression system and was isolated and purified by affinity chromatography. The cell viability and apoptosis were evaluated with MTT (thiazolyl blue tetrazolium bromide) assays and annexin V-FITC/PI staining with flow cytometry analysis, respectively. Western blot analysis was used to detect the levels of the indicated proteins in tumor cells. DR4 degradation or stability was examined with cycloheximide chase assays, and cell surface DR4 was assessed with flow cytometric analysis after staining with a FITC-conjugated antibody. The effects of cell migration were determined with Transwell and gelatin zymography assays. A xenograft nude mouse model was used to detect the anti-tumor effect in vivo, and the proliferation in tumor tissues was examined with immunohistochemical staining.Results:CD13 inhibition potently sensitized tumor cells to TRAIL-induced killing, including proliferation inhibition, increased apoptosis, and migration suppression. In addition, the inhibition of CD13 elevated both total cellular expression and cell surface DR4 through stabilizing DR4 by suppressing its degradation. DR4 siRNA attenuated the enhanced anti-tumor effects of TRAIL plus CD13 inhibition. Interestingly, these phenomena were p-ERK1/2 independent, although p-ERK1/2 down-regulation was tightly correlated with the cooperation of TRAIL and CD13 inhibition. Moreover, a synergistic decrease in tumor growth was surprisingly achieved in the xenograft model by treatment of TRAIL with a CD13 inhibitor (**P < 0.01, CDI = 0.47).Conclusions:CD13 inhibition cooperates with TRAIL in enhancing DR4-mediated cell death, through the up-regulation and stabilization of DR4 in a p-ERK1/2-independent manner. Thus CD13 inhibition has emerged as an effective strategy for TRAIL/DR4-based therapy.

JDP2 is directly regulated by ATF4 and modulates TRAIL sensitivity by suppressing the ATF4-DR5 axis.

Jun dimerization protein 2 (JDP2) is a bZip-type transcription factor, which acts as a repressor or activator of several cellular processes, including cell differentiation and chromatin remodeling. Previously, we found that a stress-responsive transcription factor, known as activating transcription factor 4 (ATF4), enhances JDP2 gene expression in human astrocytoma U373MG and cervical cancer HeLa cells; however, the role of JDP2 in the ATF4-mediated stress response remained unclear. Here, we reported that siRNA-mediated JDP2 knockdown enhances the expression of several ATF4 target genes, including ASNS, and death receptors 4 and 5 (DR4 and DR5) in HeLa cells. In addition, the results of a transient reporter assay indicate that JDP2 overexpression represses ER stress-mediated DR5 promoter activation suggesting that JDP2 negatively regulates ATF4-mediated gene expression. Curiously, knockdown of JDP2 increases the sensitivity of cells to TNF-related apoptosis-inducing ligand (TRAIL), which induces apoptosis in cancer cells through DR4 and DR5. These results indicate that JDP2 functions as a negative feedback regulator of the ATF4 pathway and contributes to TRAIL resistance in cancer cells.

Potentiation of TRAIL‑induced cell death by nonsteroidal anti‑inflammatory drug in human hepatocellular carcinoma cells through the ER stress‑dependent autophagy pathway.

Hepatocellular carcinoma (HCC) is the most commonly diagnosed primary liver malignancy. The limited success with relapse of the disease in HCC therapy is frequently associated with the acquired resistance to anticancer drugs. To develop a strategy and design for overcoming the resistance of HCC cells to TNF-related apoptosis inducing ligand (TRAIL)-induced cell death, we evaluated the efficacy of a non-steroidal anti-inflammatory drug (NSAID) in combination with TRAIL against TRAIL-resistant HCC cells expressing a high level of CD44. We revealed by MTT and western blotting, respectively, that celecoxib (CCB), an NSAID, and 2,5-dimethyl celecoxib (DMC), a non-cyclooxygenase (COX)-2 inhibitor analog of CCB, were able to sensitize TRAIL-resistant HCC cells to TRAIL, implicating a COX-independent mechanism. CCB dose-dependently enhanced LC3-II and reduced p62 levels through AMPK activation and inhibition of the Akt/mTOR pathway and upregulated expression of ATF4/CHOP, leading to activation of endoplasmic reticulum (ER) stress-dependent autophagy. The TRAIL sensitization capacity of CCB in TRAIL-resistant HCC cells was abrogated by an ER stress inhibitor. In addition, we also revealed by flow cytometry and western blotting, respectively, that accelerated downregulation of TRAIL-mediated c-FLIP expression, DR5 activation and CD44 degradation/downregulation by NSAID resulted in activation of caspases and poly(ADP-ribose) polymerase (PARP), leading to the sensitization of TRAIL-resistant HCC cells to TRAIL and thereby reversal of TRAIL resistance. From these results, we propose that NSAID in combination with TRAIL may improve the antitumor activity of TRAIL in TRAIL-resistant HCC, and this approach may serve as a novel strategy that maximizes the therapeutic efficacy of TRAIL for clinical application.

CRISPR-mediated ablation of overexpressed EGFR in combination with sunitinib significantly suppresses renal cell carcinoma proliferation.

Receptor tyrosine kinases, such as VEGFR, PDGFR and EGFR, play important roles in renal cancer. In this study, we investigated EGFR knockout as a therapeutic approach in renal cell carcinoma (RCC). We showed that a renal cell carcinoma cell line (RC21) has higher expression of EGFR as compared to other frequently used cell lines such as HEK293, A549, Hela and DLD1. Ablation of EGFR by CRISPR/Cas9 significantly restrained tumor cell growth and activated the MAPK (pERK1/2) pathway. The VEGFR and PDGFR inhibitor, sunitinib, attenuated the expression of MAPK (pERK1/2) and pAKT induced by EGFR loss and further inhibited EGFR-/- cell proliferation. We showed that loss of EGFR eventually leads to resistance to SAHA and cisplatin. Furthermore, EGFR loss induced G2/M phase arrest and resulted in an increased resistance to TNF-related apoptosis-inducing ligand (TRAIL) in renal cell carcinoma. Thus, ablation of overexpressed EGFR by CRISPR/Cas9 alone or in combination with sunitinib may be a new treatment option for renal cell carcinoma.

In silico modeling of the induction of apoptosis by Cryptotanshinone in osteosarcoma cell lines

Osteosarcoma (OS) is the most common primary malignant bone tumor of both children and pet canines. Its characteristic genomic instability and complexity coupled with the dearth of knowledge about its etiology has made improvement in the current treatment difficult. We use the existing literature about the biological pathways active in OS and combine it with the current research involving natural compounds to identify new targets and design more effective drug therapies. The key components of these pathways are modeled as a Boolean network with multiple inputs and multiple outputs. The combinatorial circuit is employed to theoretically predict the efficacies of various drugs in combination with Cryptotanshinone. We show that the action of the herbal drug, Cryptotanshinone on OS cell lines induces apoptosis by increasing sensitivity to TNF-related apoptosis-inducing ligand (TRAIL) through its multi-pronged action on STAT3, DRP1 and DR5. The Boolean framework is used to detect additional drug intervention points in the pathway that could amplify the action of Cryptotanshinone.

Accelerated degradation of cFLIPL and sensitization of the TRAIL DISC-mediated apoptotic cascade by pinoresinol, a lignan isolated from Rubia philippinensis

Plant-derived lignans have numerous biological effects including anti-tumor and anti-inflammatory activities. Screening of purified constituents of Rubia philippinensis from human glioblastoma cells resistant to TNF-related apoptosis-inducing ligand (TRAIL) has suggested that the lignan pinoresinol was a highly active TRAIL sensitizer. Here we show that treatment with nontoxic doses of pinoresinol in combination with TRAIL induced rapid apoptosis and caspase activation in many types of glioblastoma cells, but not in normal astrocytes. Analyses of apoptotic signaling events revealed that pinoresinol enhanced the formation of TRAIL-mediated death-inducing signaling complex (DISC) and complete processing of procaspase-8 within the DISC in glioblastoma cells, in which caspase-8 was inactivated. Mechanistically, pinoresinol downregulated the expression of cellular FLICE-inhibitory protein (cFLIPL) and survivin through proteasome-mediated degradation, without affecting death receptors or downstream intracellular apoptosis-related proteins. Furthermore, the sensitization of TRAIL-mediated apoptosis by pinoresinol strictly depended on the expression level of cFLIPL, which was regulated through de novo protein synthesis, rather than by NF-κB or p53 signaling. Taken together, our results indicate that pinoresinol facilitates DISC-mediated caspase-8 activation by targeting cFLIPL in an early event in apoptotic signaling, which provides a potential therapeutic module for TRAIL-based chemotherapy.

Abstract 990: Improving TRAIL therapy response in pancreatic cancer by replenishment of miR-145

Abstract Background: Pancreatic cancer (PanCa) is a third leading cause of cancer related deaths in US. Unlike other cancers, PanCa is highly resistant to TNF-related apoptosis-inducing ligand (TRAIL) that emerges as one of the most-promising therapy in clinical trials. Our group has previously identified microRNA-145 (miR-145) is downregulated in PanCa, the restoration of which inhibits tumor growth and enhances gemcitabine sensitivity. In this study, we have observed that miR-145 restoration in PanCa cells renders them sensitive to TRAIL treatment. Therefore, we have engineered unique superparamagnetic nanoparticles (SPs) for co-delivering miR-145 and TRAIL for improving TRAIL response in PanCa cells. Methods: PanCa cells, HPAF-II and AsPC1 were used in the study. A precipitation approach was employed to develop the SP formulation, which was conjugated with miR-145 and pEGFP-TRAIL. Particles were investigated for size, physico-chemical characterization (Dynamic light scattering) and the complexation of miR-145 and pEGFP-TRAIL by gel retardation assay. The formulation was investigated for functional assays, such as, proliferation (MTT), invasion (Matrigel), migration (Boyden chamber), colony and spheroid formation assays. Western blotting and immunofluorescence assays were used to investigate the effects of miR-145 restoration and death receptor activation in cells. The effect of nanoformulation on the tumor growth was investigated using xenograft mice model. Results: The results in this study demonstrate that acquired resistance to TRAIL in PanCa cells can be minimized with the replenishment of miR-145 expression. Our SP nanoparticles were engineered to co-deliver miR-145 and TRAIL to PanCa cells, which resulted in simultaneous restoration of miR-145 and inhibition of acquired resistance to TRAIL. Combined actions of miR-145 and TRAIL markedly improve TRAIL-induced apoptotic effects in PanCa cells through the activation of an extrinsic apoptosis pathway as indicated by activation of DR5, FLIP, FADD and enhanced expression of caspase-8/3. The co-delivery of miR-145 and TRAIL using SP nanoparticles inhibited tumorigenic characteristics of PanCa cells, which include proliferation, invasion, migration and clonogenicity. The results were reciprocated and got further confirmed with the inhibition of tumorsphere formation and in vivo tumorigenicity in xenograft mice. Immunohistochemical staining of excised tumor tissues demonstrate an activation of death receptor pathway and subsequent expression of apoptotic markers. Conclusion: The study provides novel insights on two facades- how resistance of cancer cells to TRAIL-based pro-apoptotic therapies can be tackled, and how efficient intracellular delivery of TRAIL can be achieved using a nanotechnology platform. Our results suggest that TRAIL resistance can be overcome by co-delivery of miR-145 and TRAIL using SP nanoparticles. Citation Format: Saini Setua, Sheema Khan, Nirnoy Dan, Murali M. Yallapu, Sonam Kumari, Stephen W. Behrman, Meena Jaggi, Subhash C. Chauhan. Improving TRAIL therapy response in pancreatic cancer by replenishment of miR-145 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 990.

Abstract 1866: Sea cucumber (Stichopus japonicas) F2 enhanced TRAIL-induced apoptosis via XIAP ubiquitination-ER stress in colorectal cancer cells

Abstract Natural products have shown great promise in sensitizing cells to TNF-related apoptosis-inducing ligand (TRAIL) therapy. Sea cucumber (SC) extracts possess antitumor activity, and hence their potential to sensitize CRC cells to TRAIL therapy was evaluated. This study used Western blotting to evaluate the combination effects of SC and TRAIL in CRC and determined the molecular mechanism underlying these effects. SC fractions and TRAIL alone had no effect on apoptosis; however, combined treatment dramatically induced apoptosis of CRC cells, but not normal colon cells. Combined treatment induced expression of apoptotic proteins (poly (ADP-ribose) polymerase (PARP), caspase 3, and 8), and this effect was markedly inhibited by ubiquitination of X-linked inhibitor of apoptosis protein (XIAP). SC did not affect the mRNA levels, but increased proteasomal degradation and ubiquitination of XIAP protein. Furthermore, SC induced reactive oxygen species (ROS) production, thereby activating c-Jun N-terminal kinase (JNK) and endoplasmic reticulum (ER) stress-related apoptotic pathways in CRC. Taken together, our results demonstrate that the SC fraction may sensitize CRC cells to TRAIL-induced apoptosis through XIAP ubiquitination-ER stress. Citation Format: Jung lim Kim, Seong Hye Park, Soyeon Jeong, Bo Ram Kim, Yoo Jin Na, Min Jee Jo, Yoon A Jeong, Hye Kyeong Yun, Dae Yeong Kim, Bu Gyeom Kim, Sang Cheul Oh, Dae-Hee Lee. Sea cucumber (Stichopus japonicas) F2 enhanced TRAIL-induced apoptosis via XIAP ubiquitination-ER stress in colorectal cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1866.

The XIAP inhibitor embelin sensitises malignant rhabdoid tumour cells to TRAIL treatment via enhanced activation of the extrinsic apoptotic pathway.

Malignant rhabdoid tumour (MRT) is a rare, aggressive paediatric neoplasm, primarily diagnosed in those below the age of three. MRTs most commonly arise in the central nervous system and kidneys. A poor prognosis accompanies the MRT diagnosis, with a reported 2‑year survival rate of30%. Thus, there is an urgent need for the development of new therapies for this malignancy. Members of the inhibitor of apoptosis protein (IAP) family have previously been reported to be overexpressed in various cancers. As such, small molecule inhibitors of these family members have entered clinical trials. However, the role of IAPs in MRT has not been examined yet. The present study is the first report of the expression of a range of IAPs, including X‑linked inhibitor of apoptosis (XIAP), cellular inhibitor of apoptosis protein1 (cIAP1), cellular inhibitor of apoptosis protein2 (cIAP2), livin and survivin in MRT cell lines. Furthermore, the results demonstrated the ability of the XIAP inhibitor, embelin, to sensitise MRT cell lines to TNF‑related apoptosis‑inducing ligand (TRAIL) treatment. The enhanced cell death detected upon cotreatment was dependent on caspase‑8 and co‑occurred with caspase‑8 and caspase‑3 cleavage, suggesting engagement of the extrinsic apoptotic pathway. Sensitisation to TRAIL was accompanied by livin cleavage, alongside downregulation of survivin and the caspase‑8 inhibitor FLIPL. In addition, knockdown of XIAP using siRNA enhanced TRAIL‑mediated cell death, suggesting that this process may in part mediate sensitisation. In conclusion, the present results suggested that IAP inhibition may present a novel avenue for the treatment of MRT.

Sea Cucumber (Stichopus japonicas) F2 Enhanced TRAIL-Induced Apoptosis via XIAP Ubiquitination and ER Stress in Colorectal Cancer Cells.

Natural products have shown great promise in sensitizing cells to TNF-related apoptosis-inducing ligand (TRAIL) therapy. Sea cucumber (SC) extracts possess antitumor activity, and hence their potential to sensitize colorectal cancer (CRC) cells to TRAIL therapy was evaluated. This study used Western blotting to evaluate the combination effects of SC and TRAIL in CRC, and determined the molecular mechanism underlying these effects. SC fractions and TRAIL alone did not affect apoptosis; however, combined treatment dramatically induced the apoptosis of CRC cells, but not of normal colon cells. Combined treatment induced the expression of apoptotic proteins (poly (ADP-ribose) polymerase (PARP), caspase 3, and 8), and this effect was markedly inhibited by the ubiquitination of X-linked inhibitor of apoptosis protein (XIAP). SC did not affect the mRNA levels, but it increased proteasomal degradation and ubiquitination of the XIAP protein. Furthermore, SC induced reactive oxygen species (ROS) production, thereby activating c-Jun N-terminal kinase (JNK) and endoplasmic reticulum (ER) stress-related apoptotic pathways in CRC. Altogether, our results demonstrate that the SC F2 fraction may sensitize CRC cells to TRAIL-induced apoptosis through XIAP ubiquitination and ER stress.

Mitochondrial origins of fractional control in regulated cell death

Individual cells in clonal populations often respond differently to environmental changes; for binary phenotypes, such as cell death, this can be measured as a fractional response. These types of responses have been attributed to cell-intrinsic stochastic processes and variable abundances of biochemical constituents, such as proteins, but the influence of organelles is still under investigation. We use the response to TNF-related apoptosis inducing ligand (TRAIL) and a new statistical framework for determining parameter influence on cell-to-cell variability through the inference of variance explained, DEPICTIVE, to demonstrate that variable mitochondria abundance correlates with cell survival and determines the fractional cell death response. By quantitative data analysis and modeling we attribute this effect to variable effective concentrations at the mitochondria surface of the pro-apoptotic proteins Bax/Bak. Further, our study suggests that inhibitors of anti-apoptotic Bcl-2 family proteins, used in cancer treatment, may increase the diversity of cellular responses, enhancing resistance to treatment.

Circulating Tumor Cells Develop Resistance to TRAIL-Induced Apoptosis Through Autophagic Removal of Death Receptor 5: Evidence from an In Vitro Model.

Circulating tumor cells (CTCs) in the peripheral blood are the precursors to distant metastasis but the underlying mechanisms are poorly understood. This study aims at understanding the molecular features within CTCs, in relation to their metastatic potential. Using in vitro CTC models, in which breast cancer cell lines were cultured in non-adherent conditions simulating the microenvironment in the blood stream, we found that the suspension culture resulted in resistance to TNF-related apoptosis inducing ligand (TRAIL)-mediated cell death. Such a resistance was directly correlated with a reduction in surface and total levels of DR5 protein. In the non-adherent state, the cells underwent a rapid autophagic flux, characterized by an accumulation of autophagosome organelles. Notably, DR5 was translocated to the autophagosomes and underwent a lysosomal degradation. Our data suggest that CTCs may evade the TNF cytokine-mediated immune surveillance through a downregulation of the death receptor (DR) expression. The data warrants further studies in cancer patients to find the status of DRs and other molecular features within primary CTCs, in relation to disease progression or chemoresistance.

Abstract 375: Origins of fractional control in regulated cell death

Abstract Fractional killing of a population of cancer cells is often linked to cell-to-cell variability due to stochastic gene expression and fluctuations in protein levels. We found that mitochondria abundance is a major source of cell-to-cell variability that determines the fraction of cells that live or die in response to TNF-related apoptosis-inducing ligand (TRAIL). We show that the IC50 of TRAIL of clonogenic cancer cell populations correlates with mitochondria abundance, and cell-to-cell variability in mitochondria abundance controls up to 40% of the response to TRAIL. Our coarse-grained quantitative model of apoptosis reveals that increasing the mitochondrial surface area decreases the density of proapoptotic Bax pores, which in turn decreases the sensitivity of cells to TRAIL. We demonstrate that the clinically relevant small-molecule inhibitor of antiapoptotic Bcl-2 proteins ABT-263 reduces the IC50 of TRAIL by reducing the contribution of mitochondria to variability in apoptosis. Citation Format: Luis C. Santos, Robert Vogel, Jerry E. Chipuk, Marc Birtwistle, Gustavo Stolovitzky, Pablo Meyer. Origins of fractional control in regulated cell death [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 375.

Abstract A063: Identification of an integrated stress response-inducing agent (NH125) that modulates DR5-dependent TRAIL synergy and ATF3-driven cell death in gliomaspheres

Abstract Purpose: The high incidence of glioblastoma recurrence necessitates additional therapeutic strategies to improve outcomes. One potential strategy targets treatment resistant cells via the integrated stress response (ISR) pathway as a means of sensitizing these cells to TNF-related apoptosis-inducing ligand (TRAIL). Methods: We generated a novel cell-based death receptor assay and used this assay to screen compounds from three commercially available libraries (total of 223 compounds) at 2 or 10 μM (Z prime = 0.64). A single hit was identified that was further characterized by immunoblotting and immunofluorescence. A compound dilution series was applied to a panel of cell lines including patient-derived glioma stem cells (GSC). IC50 values were calculated by fitting normalized viability data to a modified Hill Equation. TRAIL synergy was assessed using the combination index method following treatment with compound and TRAIL. Knockout of C/EBP Homologous Protein (CHOP) was used to determine the role of integrated stress in TRAIL synergy. GSC were also treated with temozolomide followed by assessment of cell viability. RNA-seq analysis was performed on compound treated GSC, U251, and Normal Human Astrocytes. Short hairpin RNAs were used to establish the role of ATF3 in compound-treated GSC. Results: Using a novel cell-based death receptor we identified 1-Benzyl-3-cetyl-2-methylimidazolium iodide (NH125) as a potent inducer of DR5 expression. NH125 signals through the EIF2α-ATF4-CHOP axis, culminating in DR5 expression at low micromolar doses. CHOP is required for NH125-mediated TRAIL synergy. Compared to other cancer cell lines, GSC demonstrate an increased sensitivity to NH125 treatment, and synergize with TRAIL at lower doses than U251. NH125 produced a significant decrease in GSC viability when compared to temozolomide treatment (p &amp;lt; 0.05). This enhanced sensitivity of GSC is partially due to increased expression of ATF3 following NH125 treatment. Conclusions: NH125 generates an integrated stress response leading to CHOP-mediated TRAIL synergy. Patient-derived glioma stem cells demonstrate increased sensitivity to NH125 treatment that is partially driven by increased ATF3 expression. Engaging the ISR to enhance the efficacy of TRAIL represents a promising strategy to target the treatment refractory GSC that have been implicated in glioblastoma recurrence. IC50 valuesCell LineIC50 (μM)Adj R2T4213-GSC0.89 ± 0.110.99NS039-GSC1.95 ± 0.350.99HK2962.51 ± 0.410.97U2513.30 ± 0.160.99Ovcar34.68 ± 0.340.97A5496.06 ± 0.230.99GL2616.20 ± 0.400.97U87-MG7.15 ± 0.160.98H129911.02 ± 0.430.99 Citation Format: Saad Sheikh, Xiaobing Tian, Deeksha Saxena, Xiangsheng Xu, Gary Kao, Jay F. Dorsey. Identification of an integrated stress response-inducing agent (NH125) that modulates DR5-dependent TRAIL synergy and ATF3-driven cell death in gliomaspheres [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr A063.

Knockdown of miR-27a sensitizes colorectal cancer stem cells to TRAIL by promoting the formation of Apaf-1-caspase-9 complex.

MicroRNAs have been proved to participate in multiple biological processes in cancers. For developing resistance to cytotoxic drug, cancer cells, especially the cancer stem cells, usually change their microRNA expression profile to survive in hostile environments. In the present study, we found that expression of microRNA-27a was increased in colorectal cancer stem cells. High level of microRNA-27a was indicated to induce the resistance to TNF-related apoptosis-inducing ligand (TRAIL). Knockdown of microRNA-27a resensitized colorectal cancer stem cells to TRAIL-induced cell death. Mechanically, the gene of Apaf-1, which is associated with the mitochondrial apoptosis, was demonstrated to be the target of microRNA-27a in colorectal cancer stem cells. Knockdown of microRNA-27a increased the expression level of Apaf-1, thus enhancing the formation of Apaf-1-caspase-9 complex and subsequently promoting the TRAIL-induced apoptosis in colorectal cancer stem cells. These findings suggested that knockdown of microRNA-27a in colorectal cancer stem cells by the specific antioligonucleotides was potential to reverse the chemoresistance to TRAIL. It may represent a novel therapeutic strategy for treating the colorectal cancer more effectively.

Bay 61-3606 Sensitizes TRAIL-Induced Apoptosis by Downregulating Mcl-1 in Breast Cancer Cells.

Breast cancer cells generally develop resistance to TNF-Related Apoptosis-Inducing Ligand (TRAIL) and, therefore, assistance from sensitizers is required. In our study, we have demonstrated that Spleen tyrosine kinase (Syk) inhibitor Bay 61–3606 was identified as a TRAIL sensitizer. Amplification of TRAIL-induced apoptosis by Bay 61–3606 was accompanied by the strong activation of Bak, caspases, and DNA fragmentation. In mechanism of action, Bay 61–3606 sensitized cells to TRAIL via two mechanisms regulating myeloid cell leukemia sequence-1 (Mcl-1). First, Bay 61–3606 triggered ubiquitin-dependent degradation of Mcl-1 by regulating Mcl-1 phosphorylation. Second, Bay 61–3606 downregulates Mcl-1 expression at the transcription level. In this context, Bay 61–3606 acted as an inhibitor of Cyclin-Dependent Kinase (CDK) 9 rather than Syk. In summary, Bay 61–3606 downregulates Mcl-1 expression in breast cancer cells and sensitizes cancer cells to TRAIL-mediated apoptosis.

The secreted protein acidic and rich in cysteine is a critical mediator of cell death program induced by WIN/TRAIL combined treatment in osteosarcoma cells.

Secreted protein acidic and rich in cysteine (SPARC) is a multi-functional protein which modulates cell-cell and cell-matrix interactions. In cancer cells, SPARC behaves as a tumor promoter in a number of tumors, but it can also act as a tumor suppressor factor. Our previous results showed that the synthetic cannabinoid WIN55,212-2 (WIN), a potent cannabinoid receptor agonist, is able to sensitize osteosarcoma MG63 cells to TNF-related apoptosis-inducing ligand (TRAIL)-induced apoptosis which is accompanied with endoplasmic reticulum (ER)-stress induction and the increase in autophagic markers. In the present investigation, we studied the role of SPARC in WIN/TRAIL-induced apoptosis demonstrating that WIN increased the level of SPARC protein and mRNA in a time-dependent manner. This event was functional to WIN/TRAIL-dependent apoptosis as demonstrated by RNA interfering analysis which indicated that SPARC-silenced cells were less sensitive to cytotoxic effects induced by the combined treatment. Our experiments also demonstrate that SPARC interacts with caspase-8 thus probably favoring its translocation to plasma membrane and the activation of extrinsic apoptotic pathway. In conclusion, to the best of our knowledge, our results are the first to show that WIN-dependent increase in the level of SPARC plays a critical role in sensitizing osteosarcoma cells to TRAIL action.