TRAIL Receptor Research Articles

Tumor Necrosis Factor–Related Apoptosis-Inducing Ligand Receptor Deficiency Promotes the Ductular Reaction, Macrophage Accumulation, and Hepatic Fibrosis in the Abcb4−/− Mouse

The tumor necrosis factor-related apoptosis-inducing ligand (TRAIL; TNFSF10) receptor (TR) is a pro-apoptotic receptor whose contribution to chronic cholestatic liver disease is unclear. Herein, we examined TRAIL receptor signaling in a mouse model of cholestatic liver injury. TRAIL receptor-deficient (Tnsf10 or Tr-/-) mice were crossbred with ATP binding cassette subfamily B member 4-deficient (Abcb4-/-, alias Mdr2-/-) mice. Male and female wild-type, Tr-/-, Mdr2-/-, and Tr-/-Mdr2-/- mice were assessed for liver injury, fibrosis, and ductular reactive (DR) cells. Macrophage subsets were examined by high-dimensional mass cytometry (time-of-flight mass cytometry). Mdr2-/- and Tr-/-Mdr2-/- mice had elevated liver weights and serum alanine transferase values. However, fibrosis was primarily periductular in Mdr2-/- mice, compared with extensive bridging fibrosis in Tr-/-Mdr2-/- mice. DR cell population was greatly expanded in the Tr-/-Mdr2-/- versus Mdr2-/- mice. The expanded DR cell population in Tr-/-Mdr2-/- mice was due to decreased cell loss by apoptosis and not enhanced proliferation. As assessed by time-of-flight mass cytometry, total macrophages were more abundant in Tr-/-Mdr2-/- versus Mdr2-/- mice, suggesting the DR cell population promotes macrophage-associated hepatic inflammation. Inhibition of monocyte-derived recruited macrophages using the CCR2/CCR5 antagonist cenicriviroc in the Mdr2-/- mice resulted in further expansion of the DR cell population. In conclusion, genetic deletion of TRAIL receptor increased the DR cell population, macrophage accumulation, and hepatic fibrosis in the Mdr2-/- model of cholestasis.

Dasatinib prevents skeletal metastasis of osteotropic MDA-MB-231 cells in a xenograft mouse model.

Bone metastasis in breast cancer has been linked to activity of c-Src kinase, one of the extensively explored tyrosine kinases in cell biology. The impact of TNF-related apoptosis inducing ligand (TRAIL) and TRAIL receptors has just recently been integrated into this conception. An osteotropic clone of MDA-MB-231 cells simulated a model for bone metastasis of triple-negative breast cancer (TNBC). The effects of Dasatinib, a clinically established inhibitor of Src kinases family and Abl were evaluated in vitro and in vivo. In vivo effects of Dasatinib treatment on the occurrence of skeletal metastases were tested in a xenograft mouse model after intra-cardiac injection of osteotropic MDA-MB-231-cells. Ex vivo analyses of the bone sections confirmed intraosseous growth of metastases and allowed determination of osteoclastic activity. Treatment of osteotropic MDA-MB-231 cells with Dasatinib inhibited proliferation rates in vitro. A shift in TRAIL-receptor expression towards an induction of oncogenic TRAIL-R2 was observed. In vivo, 15 of 30 mice received an intra-peritoneal treatment with Dasatinib. These mice showed significantly less skeletal metastases in bioluminescence scans. Moreover, a pronounced increase in bone volume was observed in the treatment group, as detected by µ-Computed Tomography. Dasatinib treatment also led to a greater increase in bone density in tibiae without metastatic affection, which was accompanied by reduced recruitment of osteoclasts. Our observations support the concept of utilizing Dasatinib in targeting early-stage bone metastatic TNBC and sustaining bone health.

Curcumin augments therapeutic efficacy of TRAIL-based immunotoxins in leukemia.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL/Apo2L) has been perceived as a promising anti-cancer agent because of its unique ability to kill cancer cells while sparing normal cells. However, translation of TRAIL to clinical studies was less successful as a large number of cancer cells acquire resistance to TRAIL-based monotherapies. An ideal strategy to overcome TRAIL resistance is to combine it with potential sensitizing agents. To investigate the TRAIL-sensitizing effect of curcumin in leukemia. The mechanism underlying TRAIL sensitization by curcumin was studied by flow cytometric analysis of TRAIL receptors in leukemic cell lines and patient samples, and immunoblot detection of TRAIL-apoptosis signaling proteins. Curcumin augments TRAIL-apoptotic signaling in leukemic cells by upregulating the expression of DR4 and DR5 along with suppression of cFLIP and anti-apoptotic proteins Mcl-1, Bcl-xl, and XIAP. Curcumin pre-treatment significantly (p < 0.01) enhanced the sensitivity of leukemic cell lines to TRAIL recombinant proteins. IL2-TRAIL peptide in the presence of curcumin induced potent apoptosis (p <0.001) as compared to TRAIL and IL2-TRAIL protein in leukemic cell lines with IC50 < 0.1 μΜ. Additionally, the combination of IL2-TRAIL peptide and curcumin showed significant cytotoxicity in patient peripheral blood mononuclear cells (PBMCs) with an efficacy of 90% in acute myeloid leukemia (AML), but 100% in acute lymphoblastic leukemia (ALL), chronic lymphocytic leukemia (CLL) and chronic myelomonocytic leukemia (CMML). Overall, our results suggest that curcumin potentiates TRAIL-induced apoptosis through modulation of death receptors and anti-apoptotic proteins which significantly enhances the therapeutic efficacy.

ER Stress Leaves an Inflammatory TRAIL.

Cell stress often triggers inflammation as a protective response to tissue damage or infection. In this issue of Developmental Cell, Sullivan etal. (2020) reveal an unexpected role for TRAIL receptors in ER-stress-induced inflammation.

TRAIL Receptors Serve as Stress-Associated Molecular Patterns to Promote ER-Stress-Induced Inflammation.

Inflammation triggered by infection or cellular necrosis is initiated by a battery of pattern-recognition receptors, such as Toll-like receptors or IL-1 family receptors. Diverse forms of cell stress, such as ER stress or mitochondrial stress, can also promote inflammatory responses that contribute to the chronic inflammation observed in cancer, obesity, and otherconditions. However, the molecular mechanisms of cell-stress-induced inflammation are poorly understood. Here, we show that ER stress initiated NF-κB activation and inflammation through transcriptional upregulation and ligand-independent activation of TRAIL receptors. ER-stress-induced TRAIL receptor activation resulted in caspase-8/FADD/RIPK1-dependent NF-κB activation and inflammatory cytokine production. Silencing or deletion of TRAIL receptors, or their downstream effectors caspase-8, FADD, or RIPK1, suppressed ER-stress-induced inflammation. Furthermore, chemotherapeutic stress-induced inflammatory responses were blunted in DR5/TRAIL-R null animals. We propose that, upon ER stress, TRAIL receptors serve as "stress-associated molecular patterns (SAMPs)" coupling ER stress to NF-κB-dependent inflammation.

TRAIL receptors are differentially regulated and clinically significant in gallbladder cancer

Deregulation of the receptors of TNF-related apoptosis inducing ligand (TRAIL) has been reported in various cancers. In an effort to define the role of these receptors we profiled their expression in gallbladder cancer (GBC) and explored their clinical significance. Expression of TRAIL receptors' mRNA in GBC was analysed through reverse transcriptase polymerase chain reaction (RT-PCR), and protein through western blotting, immunohistochemistry and enzyme-linked immunosorbent assay (ELISA). mRNA data show frequent higher expression of TRAIL receptors in GBC samples. Death receptors DR4 and DR5 showed significant negative correlation with tumour stage, T stage and tumour grade; DcR1 transcript showed positive correlation with tumour stage, N stage, M stage and tumour grade. Similarly, IHC showed frequent positive staining for DR4, DR5 and DcR1in GBC samples. Cytoplasmic and nuclear DR4 protein showed negative correlation with T stage and tumour grade, whereas cytoplasmic DcR1 protein showed positive correlation with tumour stage and N stage. Nuclear DcR1 showed positive correlation with N stage. ELISA results showed significantly higher expression of secretory DcR1 in GBC patients. Kaplan-Meier analysis demonstrated significantly decreased mean survival of patients with positive staining of cytoplasmic DcR1. High level of death receptors identified the patients with early gallbladder cancer, whereas high DcR1 expression served as a prognostic factor for poor outcome.

Convergence of pathway analysis and pattern recognition predicts sensitization to latest generation TRAIL therapeutics by IAP antagonism

Second generation TRAIL-based therapeutics, combined with sensitising co-treatments, have recently entered clinical trials. However, reliable response predictors for optimal patient selection are not yet available. Here, we demonstrate that a novel and translationally relevant hexavalent TRAIL receptor agonist, IZI1551, in combination with Birinapant, a clinically tested IAP antagonist, efficiently induces cell death in various melanoma models, and that responsiveness can be predicted by combining pathway analysis, data-driven modelling and pattern recognition. Across a panel of 16 melanoma cell lines, responsiveness to IZI1551/Birinapant was heterogeneous, with complete resistance and pronounced synergies observed. Expression patterns of TRAIL pathway regulators allowed us to develop a combinatorial marker that predicts potent cell killing with high accuracy. IZI1551/Birinapant responsiveness could be predicted not only for cell lines, but also for 3D tumour cell spheroids and for cells directly isolated from patient melanoma metastases (80–100% prediction accuracies). Mathematical parameter reduction identified 11 proteins crucial to ensure prediction accuracy, with x-linked inhibitor of apoptosis protein (XIAP) and procaspase-3 scoring highest, and Bcl-2 family members strongly represented. Applied to expression data of a cohort of n = 365 metastatic melanoma patients in a proof of concept in silico trial, the predictor suggested that IZI1551/Birinapant responsiveness could be expected for up to 30% of patient tumours. Overall, response frequencies in melanoma models were very encouraging, and the capability to predict melanoma sensitivity to combinations of latest generation TRAIL-based therapeutics and IAP antagonists can address the need for patient selection strategies in clinical trials based on these novel drugs.

Supramolecular assembly of protein-based nanoparticles based on tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) for cancer therapy

Molecular self-assembly of functional proteins has garnered intense interest for the development of nanomaterials. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), as one of the most promising agents for cancer therapy, could selectively induce the apoptotic cell death in tumor cells while not on normal cells. In this study, protein-based nanoparticles were constructed with TRAIL and a dipeptide, diphenylalanine (FF), through molecular self-assembly. TRAIL-FF nanoparticles with sizes ranging from 60 nm to 500 nm could be prepared by controlling the concentration and the ratio of the two components. These nanoparticles could locate around the cytomembrane of MCF-7 cells due to the specific interaction between TRAIL and death receptors, thus transduce apoptotic signal. Therefore, the TRAIL-FF nanoparticles showed distinct killing effect on the cancer cells, such as MCF-7 and H460 cells, and the IC50 of the nanoparticles on H460 cells was about 260 ng/mL. The approach presented herein may be applicable to the fabrication of an extended range of protein-based functional biomaterials.

TRAIL receptor signaling: From the basics of canonical signal transduction toward its entanglement with ER stress and the unfolded protein response.

The cytokine tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a member of the large TNF superfamily that can trigger apoptosis in transformed or infected cells by binding and activating two receptors, TRAIL receptor 1 (TRAILR1) and TRAIL receptor 2 (TRAILR2). Compared to other death ligands of the same family, TRAIL induces apoptosis preferentially in malignant cells while sparing normal tissue and has therefore been extensively investigated for its suitability as an anti-cancer agent. Recently, it was noticed that TRAIL receptor signaling is also linked to endoplasmic reticulum (ER) stress and the unfolded protein response (UPR). The role of TRAIL receptors in regulating cellular apoptosis susceptibility therefore is broader than previously thought. Here, we provide an overview of TRAIL-induced signaling, covering the core signal transduction during extrinsic apoptosis as well as its link to alternative outcomes, such as necroptosis or NF-κB activation. We discuss how environmental factors, transcriptional regulators, and genetic or epigenetic alterations regulate TRAIL receptors and thus alter cellular TRAIL susceptibility. Finally, we provide insight into the role of TRAIL receptors in signaling scenarios that engage the unfolded protein response and discuss how these findings might be translated into new combination therapies for cancer treatment.

Tianma Gouteng Decoction Exerts Cardiovascular Protection by Upregulating OPG and TRAIL in Spontaneously Hypertensive Rats.

Tianma Gouteng Decoction (TGD) is widely used in traditional Chinese medicine for the treatment of hypertension and its related complications, but its mechanisms remain incompletely defined. We now aim to assess the protective effect of TGD against cardiovascular damage and to investigate its characteristics and underlying mechanisms. Blood pressure was determined in TGD-treated spontaneously hypertensive rats (SHR) by noninvasive measurements. Echocardiography was performed to assess cardiac function and structure and sirius red staining to evaluate cardiac fibrosis, and the degree of vascular remodeling was evaluated. Additionally, vasoconstriction and relaxation factor expression changes were examined by means of ELISA. Protein expression changes were verified by western blot. Compared with untreated SHR, TGD-treated SHR exhibited cardiovascular traits more akin to those of the normotensive Wistar Kyoto (WKY) rats. That is, they had lower diastolic blood pressure, systolic blood pressure and mean BP, and increased expression of vasodilation factor. We also found that TGD reduces ventricular and vascular remodeling and improves cardiac function in SHR. Finally, we tested the antiapoptosis effect TGD exerts in SHR, ostensibly by upregulating the expression of OPG, TRAIL, and death receptor 5 (DR5) and downregulating caspases 8, 7, and 3. TRAIL may also exert antiapoptotic and prosurvival effects by upregulating AKT expression. Therefore, TGD may reverse cardiovascular remodeling in SHR by upregulating the expression of OPG and TRAIL, upregulating AKT, and inhibiting apoptosis, at least in part. For the first time, we have shown that OPG and TRAIL play complimentary cardioprotective roles in SHR.

PDGFRβ-targeted TRAIL specifically induces apoptosis of activated hepatic stellate cells and ameliorates liver fibrosis.

Liver fibrosis usually progresses to liver cirrhosis and even hepatocellular carcinoma. Since activated hepatic stellate cells (aHSCs) are responsible for liver fibrosis, reducing the quantity of aHSCs was considered the essential strategy for clinical antihepatofibrotic therapy. Due to the overexpression of TRAIL receptor 2 (DR5) in aHSCs, human TNF-related apoptosis-inducing ligand (hTRAIL) that could induce aHSCs apoptosis might be feasible for antihepatofibrotic therapy. However, the in vivo aHSCs-apoptosis-induction of hTRAIL is limited by its poor cell-targeting and a short half-life. In this study, we found that platelet-derived growth factor receptor β (PDGFRβ) was co-expressed with DR5 in aHSCs. And the ZPDGFRβ affibody with high affinity for PDGFRβ could bind aHSCs and, thus, accumulate in the fibrotic liver. ZPDGFRβ was fused to hTRAIL to produce the fusion protein Z-hTRAIL. Compared to hTRAIL, Z-hTRAIL showed greater in vitro cell binding and apoptosis-induction in aHSCs. In addition, Z-hTRAIL induced apoptosis of aHSCs but spared other normal liver cells. In vivo, Z-hTRAIL accumulated preferentially in fibrotic livers and exerted greater effects than hTRAIL in inducing aHSCs apoptosis and reducing extracellular matrix (ECM) deposition. These results demonstrated that the antihepatofibrotic effect of hTRAIL was improved by PDGFRβ-targeted delivery. To enhance its pharmacokinetics, Z-hTRAIL was modified with 10kDa polyethylene glycol (PEG), which significantly (30-40 times) prolonged its half-life. The PEGylated long-acting Z-hTRAIL was more potent than the native Z-hTRAIL in regressing liver fibrosis. These results suggest that the aHSC-targeting and long-acting Z-hTRAIL might serve as a novel tool for antihepatofibrotic therapy.

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.

Disulfide bond-disrupting agents activate the tumor necrosis family-related apoptosis-inducing ligand/death receptor 5 pathway

Disulfide bond-disrupting agents (DDAs) are a new chemical class of agents recently shown to have activity against breast tumors in animal models. Blockade of tumor growth is associated with downregulation of EGFR, HER2, and HER3 and reduced Akt phosphorylation, as well as the induction of endoplasmic reticulum stress. However, it is not known how DDAs trigger cancer cell death without affecting nontransformed cells. As demonstrated here, DDAs are the first compounds identified that upregulate the TRAIL receptor DR5 through transcriptional and post-transcriptional mechanisms to activate the extrinsic cell death pathway. At the protein level, DDAs alter DR5 disulfide bonding to increase steady-state DR5 levels and oligomerization, leading to downstream caspase 8 and 3 activation. DDAs and TRAIL synergize to kill cancer cells and are cytotoxic to HER2+ cancer cells with acquired resistance to the EGFR/HER2 tyrosine kinase inhibitor Lapatinib. Investigation of the mechanisms responsible for DDA selectivity for cancer cells reveals that DDA-induced upregulation of DR5 is enhanced in the context of EGFR overexpression. DDA-induced cytotoxicity is strongly amplified by MYC overexpression. This is consistent with the known potentiation of TRAIL-mediated cell death by MYC. Together, the results demonstrate selective DDA lethality against oncogene-transformed cells, DDA-mediated DR5 upregulation, and protein stabilization, and that DDAs have activity against drug-resistant cancer cells. Our results indicate that DDAs are unique in causing DR5 accumulation and oligomerization and inducing downstream caspase activation and cancer cell death through mechanisms involving altered DR5 disulfide bonding. DDAs thus represent a new therapeutic approach to cancer therapy.

The Impact and Modulation of Microenvironment-Induced Immune Resistance Against CAR T Cell and Antibody Treatments in Multiple Myeloma

The tumor microenvironment of multiple myeloma (MM) is known to play a critical role in disease pathogenesis, MM cell survival, and drug resistance. In addition, we have previously demonstrated the impact of the microenvironment also on immunotherapies. We discovered that bone marrow mesenchymal stromal cells (BMMSCs) protected MM cells from HLA restricted CD4 and CD8 cytotoxic T cells and NK cell-mediated daratumumab dependent cytotoxicity through a cell-adhesion mediated immune resistance (CAM-IR). This CAM-IR corresponded with the upregulation of anti-apoptotic proteins Survivin and Mcl-1 in MM cells and could be modulated by small inhibitors of these molecules. We now extended our studies to investigate the impact of the microenvironment on novel immunotherapeutic approaches such as chimeric antigen receptor-transduced T cells (CAR T cells) and death receptor mediated antibody treatments, which can induce direct apoptosis in MM cells. We also investigated the possibility to modulate CAM-IR with small molecule inhibitors of Survivin, XIAP, and Mcl-1. To this end, we tested a panel of MM reactive CAR T cells directed against CD38, BCMA, and CD138, with different target affinities, for their potential to kill MM cells in the absence or presence of BMMSCs. We observed no effect of BMMSCs on the cytotoxic capacity of BCMA- and CD38-targeting CAR T cells with high affinity for the target and that were capable of inducing high levels of MM cell lysis at very low effector to target ratios. In contrast, BMMSCs effectively protected MM cells against killing by BCMA- and CD38-targeting CAR T cells with relative low affinity, or CD138-targeting CAR T cells that were less powerful in their lytic activity. Taken together, we discovered a significant inverse correlation between the lytic capacity of the CAR T cells and the extent of BMMSC-mediated protection. Additionally, we found that BMMSCs protected MM cells from apoptosis induction by death receptor 5 (DR5; or TRAIL receptor 2) antibodies. In all cases of BMMSC-mediated protection against CAR T cells as well as DR5 antibodies or daratumumab, the protection could be abrogated by an inhibitor of Survivin, XIAP, and Mcl-1. This indicates that BMMSC-mediated protection against CAR T cell or antibody-mediated lysis is indeed associated with an upregulation of anti-apoptotic proteins, similarly to the well-described cell adhesion mediated drug resistance. In conclusion, our results confirm the potential negative impact of the tumor microenvironment in the development of an adaptive resistance of MM cells against immunotherapies. Our data further suggest that this microenvironmental shielding of MM cells can be overcome either by increasing the avidity of immune killer cells or through combination of immunotherapy with inhibitors of anti-apoptotic mediators. Figure 1 Disclosures Li: Canget Bio Tekpharma LLC: Membership on an entity's Board of Directors or advisory committees. Zweegman:Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Research Funding. Themeli:Covagen: Consultancy. Van De Donk:Janssen Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Research Funding; Bristol-Myers Squibb: Membership on an entity's Board of Directors or advisory committees, Research Funding; AMGEN: Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Membership on an entity's Board of Directors or advisory committees; Servier: Membership on an entity's Board of Directors or advisory committees; Celgene Corporation: Membership on an entity's Board of Directors or advisory committees, Research Funding; Bayer: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees. Mutis:Aduro: Research Funding; Celgene: Research Funding; BMS: Research Funding; Amgen: Research Funding; Onkimmune: Research Funding; Janssen Pharmaceuticals: Research Funding; Novartis: Research Funding.

CRISPR Screens Identify Mechanisms of Natural Killer Cell Evasion across Blood Cancers

Natural killer (NK) cells have been suggested to control progression and relapse in several hematological malignancies. Enhancing NK cell reactivity represents an attractive approach to improve treatment responses. However, mechanisms enabling evasion of hematologic cancer cells from NK cells are incompletely understood. To identify cancer cell-intrinsic factors enabling resistance to NK cell cytotoxicity, we conducted genome-wide CRISPR screens in a range of hematological malignancies. Cas9-expressing cancer cells from diverse hematological malignancies, including acute and chronic myeloid leukemia (AML and CML), multiple myeloma (MM), diffuse large B-cell lymphoma (DLBCL), and B cell acute lymphoblastic leukemia were infected with a genome-scale lentiviral sgRNA library and exposed to primary human NK cells. Genes essential for NK cell cytotoxicity were discovered from surviving cancer cells which were enriched with gene knockouts inducing reduced sensitivity to NK cell killing. Additional data from a gain-of-function screen using a genome-scale CRISPR activation system were generated using the MM.1S myeloma cell line. Results from the functional genomic screens were integrated with transcriptomic data from &amp;gt; 9,000 patients across hematological cancers, as well as multi-omics data from AML and DLBCL, and both public and in-house single-cell RNA-sequencing data from AML patients. Knockout of genes encoding components involved in antigen presentation (B2M, HLA-A, HLA-C, HLA-E, TAP1, TAP2) sensitized multiple blood cancer cell lines to NK cell cytotoxicity, consistent with the inhibitory effect of MHC I on NK cells. Furthermore, knockout of interferon and JAK-STAT signaling components sensitized cancer cells to NK cell lysis, suggesting that MHC class I induction in response to interferon promotes NK cell resistance across cancer types. Interestingly, genes and pathways whose disruption conferred resistance for NK cell-mediated lysis exhibited partial overlap but also substantial variability across blood cancer types. Knockout of NCR3LG1 (B7-H6, ligand for the NKp30 activating NK cell receptor), resulted in resistance of K562 CML cells to NK cell cytotoxicity. In contrast, disruption of genes encoding apoptotic mediators (FADD, PMAIP1, BID) and TRAIL receptors (TNFRSF10B) conferred resistance to NK cell cytotoxicity in SUDHL4 DLBCL cells. The same pathways were identified in the MM cell line MM.1S, in which knockout of FAS, CASP2, and CASP8 as well as the TRAIL receptor TNFRSF10A induced NK cell resistance. Furthermore, loss of CD48, a ligand of the non-MHC binding receptor CD244 on NK cell surface, resulted in resistance and a genome-scale CRISPR gain-of-function screen in the same cell line showed sensitization upon CD48 overexpression. A CRISPR screen in the AML cell line MOLM14 identified disruption of TNFRSF1B encoding TNFR2 as strongly conferring NK cell resistance. Interestingly, TNFRSF1B overexpression sensitized the MM cell line MM.1S to NK cell treatment in the gain-of-function screen. Integration with genomic data from patients with hematological malignancies revealed selective expression of TNFRSF1B in AML. Within AML, TNFRSF1B expression was enriched in myelomonocytic and monocytic subtypes as well as in MLL-rearranged cases represented by the MOLM14 cell line. Further dissection at the single-cell level revealed increased expression of TNFRSF1B with differentiation of AML cells along the monocytic lineage. Consistently, the less differentiated MOLM13 cell line established from the same patient as MOLM14 was resistant to NK cell killing, suggesting that a less differentiated phenotype of AML cells confers resistance to NK cell cytotoxicity through lack of TNFRSF1B expression. Our data suggest that different lineages of hematological malignancies may be susceptible to NK cells through distinct mechanisms. In some cases, this heterogeneity is governed by lineage-specific expression of susceptibility genes, such as TNFRSF1B in monocytic AML. Particularly, our data identify a mechanism of NK cell evasion in less differentiated AML cells, suggesting potential for enhancing immune clearance of AML cells through differentiating therapies. figure Disclosures Lee: Kiadis Pharma: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents &amp; Royalties, Research Funding. Mitsiades:Takeda: Other: employment of a relative ; Ionis Pharmaceuticals: Honoraria; Fate Therapeutics: Honoraria; Arch Oncology: Research Funding; Sanofi: Research Funding; Karyopharm: Research Funding; Abbvie: Research Funding; TEVA: Research Funding; EMD Serono: Research Funding; Janssen/Johnson &amp; Johnson: Research Funding. Mustjoki:BMS: Honoraria, Research Funding; Novartis: Research Funding; Pfizer: Research Funding.

A Novel Combination of Drugs Which Target Both the Intrinsic and Extrinsic Apoptotic Pathways to Eliminate Myelofibrosis CD34+ Cells

Introduction: P53 is negatively regulated by MDM2 and increased expression of MDM2 in PV and MF CD34+ cells and megakaryocytes has been observed. Recently, we have shown that MDM2 antagonists termed nutlins can selectively eliminate MPN CD34+ cells (1-2). We have reported a phase 1 trial of PV patients treated with an oral nutlin, RG7388, which resulted in hematological responses and an improvement in symptoms in a substantial subset of PV patients intolerant or refracting to frontline therapy (3). Nutlins, however only target malignant cells with wild type p53, cannot completely eliminate the MPN stem cell pool and are associated with gastrointestinal toxicity. We therefore searched for another class of compounds to combine with nutlins to more effectively eliminate MF stem cells. Recently, an oral imipridone compound, ONC201, has been evaluated in clinical trials of patients with hematological malignancies (leukemia/lymphoma) and solid tumors. ONC201 was discovered by screening drug libraries for compounds that transcriptionally induced the TNF-related apoptosis inducing ligand (TRAIL) which triggers apoptosis through the extrinsic pathway which is independent of p53. ONC201 is also as potent allosteric agonist of mitochondrial caseinolytic protease P (ClpP) (4). Hyperactivation of ClpP by ONC201 increases mitochondrial proteolysis and leads to mitochondrial dysfunction and triggers the extrinsic apoptotic pathway. We hypothesized that combination treatment with nutlin (RG7112/RG7388) and ONC201 might provide an effective therapeutic strategy to selectively induce apoptosis of MF CD34+ cells by activating both intrinsic and extrinsic apoptosis pathways. Results: We tested whether RG7112 combined with ONC201 was capable of specifically targeting MF CD34+ cells. Treatment with ONC201 alone decreased total hematopoietic colonies generated by MF CD34+ cells in a dose dependent fashion. Treatment with ONC201 at dose of 10 uM decreased MF colony numbers by 50%, and a 500nM dose of RG7112 decreased MF colony numbers by 30%. Combination therapy with RG7112 and ONC201, however, decreased MF colony numbers by 70% (ONC201 vs RG-ONC201: p=0.005 and RG vs RG-ONC201: p=0.001, respectively). By contrast, treatment with these agents alone or in combination did not decrease colony formation by normal CD34+ cells. ONC201 or RG7112 alone at the doses utilized did not alter the genotype of the MF colonies; however, combination therapy decreased the numbers of JAK2V617F+ colonies by 20%, and increased wild type colony numbers by 24%. These data suggest that combination treatment with RG7112 and ONC201 can specifically deplete MF malignant CD34+ cells. We next tried to understand the mechanism by which combination therapy with RG7112 and ONC201 specifically targeted MF CD34+ cells. We found increased transcript levels of ClpP in untreated MF CD34+ cells as compared to normal CD34+ cells (p=0.03). Exposure of MF CD34+ cells to this drug combination significantly induced apoptosis of MF CD34+ cell (p=0.04), but did not induce apoptosis of normal CD34+ cells. Treatment of MF CD34+ cells with ONC201 alone increased transcript levels of TRAIL and death receptor 5 (DR5), but treatment with RG7112 alone did not have a similar effect. Furthermore, a combination of RG7112 and ONC201 synergistically increased not only TRAIL and DR5 but also ClpP transcript levels to a far greater extent. Treatment with RG7112 and ONC201, however, alone or in combination did not elevate ClpP, DR5 or TRAIL transcripts level in normal CD34+ cells. Treatment of MF CD34+ cells with either RG7112 or ONC201 alone increased TRAIL and DR5 protein levels to a modest degree but the degree of elevation was far greater with a combination of these two drugs. Treatment with RG7112 and ONC201 alone or in combination also increased FOXO3a, ClpP and ATF4 protein levels which are the upstream regulators of TRAIL and DR5, respectively (Figure 1). Summary: These data indicate that ONC201 combined with RG7112 is a potentially effective strategy for the treatment of MF. This drug combination selectively targets MF CD34+ cells by activating different apoptotic pathways that are both p53 dependent and p53 independent. Such a therapeutic approach would be anticipated to promote the elimination of both p53 wild type and p53 mutated MPN stem cell clones resulting in a greater depletion of MF but not normal stem cells. Disclosures Hoffman: Merus: Research Funding.

Targeting CD38high Acute Myeloid Leukaemia with “Affinity Optimized” Chimeric Antigen Receptor and Membrane Bound TRAIL Expressing Natural Killer Cells

Targeting CD38high Acute Myeloid Leukaemia with “Affinity Optimized” Chimeric Antigen Receptor and Membrane Bound TRAIL Expressing Natural Killer Cells

First-in-Human Study of Abbv-621, a TRAIL Receptor Agonist Fusion Protein, in Patients (Pts) with Relapsed/Refractory (RR) Acute Myeloid Leukemia (AML) and Diffuse Large B-Cell Lymphoma (DLBCL)

Background: Apoptotic cell death can be triggered by activation of extrinsic and intrinsic signaling pathways. Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), a member of the TNF superfamily, binds to its death receptors TRAIL-R1 (DR4) and TRAIL-R2 (DR5) to selectively activate the extrinsic apoptotic pathway in cancer cells. ABBV-621 is a second-generation TRAIL receptor agonist with antitumor activity as monotherapy (621-mono) in preclinical models of AML and DLBCL. The intrinsic apoptotic pathway is regulated by the BCL2 protein family, commonly overexpressed in hematologic malignancies. Venetoclax (VEN), a highly selective small-molecule BCL2 inhibitor, has shown antitumor activity in combination therapy in AML and DLBCL. In preclinical and xenograft models of AML and DLBCL, the ABBV-621 and VEN combination (621-VEN) had antitumor activity superior to either agent alone. This first-in-human study evaluated ABBV-621 as single agent and in combination in pts with advanced solid tumors and hematologic malignancies (NCT03082209). Safety and tolerability of ABBV-621 in advanced solid tumors have previously been presented (Ratain et al. J Clin Oncol 2019;37[suppl]: abstr 3013). Here, we report preliminary data for 621-mono in pts with RR AML and for 621-VEN in pts with RR AML and DLBCL. Methods: Adult pts with RR AML or DLBCL (ECOG 0-2) were enrolled. Pts with AML received ABBV-621 at 1.25-, 3.75-, 7.5-mg/kg doses in the 621-mono and at 3.75-mg/kg dose in the 621-VEN arms. Pts in the DLBCL 621-VEN arm received ABBV-621 at 3.75- and 7.5-mg/kg doses. ABBV-621 was administered intravenously on D1, 8, and 15 of a 21-D cycle; in 621-VEN cohorts pts received 400 mg oral VEN daily, and could be escalated to 800 mg. The primary endpoint was safety. In addition, preliminary antitumor efficacy and ABBV-621 binding to decoy receptors on neutrophils from peripheral blood were assessed. Results: As of Jun 2019, 17 pts were enrolled. Pts in AML 621-mono arm (1.25 [1], 3.75 [1], 7.5 [2] mg/kg): 1 male; median (med) age, 75 yr (range 71-82); med prior treatments, 2.5 (range 1-4); med time on treatment, 15 D (range 1-70). Pts in AML 621-VEN arm (3.75 mg/kg [7]): 5 male; med age, 71 yr (60-79); med prior treatments, 2 (1-2); med time on treatment, 26 D (1-77). Pts in DLBCL 621-VEN arm (3.75 [3], 7.5 [3] mg/kg): 4 male; med age, 57 yr (40-75); stage 4 (3); med prior treatments, 2.5 (1 to ≥5); med time on treatment, 26 D (8-36). One pt in the AML 621-VEN 3.75-mg/kg dose cohort had increases in alanine aminotransferase, aspartate aminotransferase and bilirubin as dose-limiting toxicities. Sixteen pts experienced adverse events (AEs) irrespective of causality. A summary of AEs is shown in Table. One pt in the AML 621-mono 7.5-mg/kg dose cohort died due to AML progression, unrelated to ABBV-621. Antitumor activity was observed in 1 pt in the AML 621-VEN arm (with complex cytogenetics and TP53 mutation) who reached complete remission (CR). One pt in the DLBCL 621-VEN 3.75-mg/kg cohort had stable disease, 2 with AML had resistant disease (1 in 621-mono [7.5 mg/kg] and 1 in 621-VEN), and 7 had progressive disease (PD; 1 in AML 621-mono [1.25 mg/kg], 2 in AML 621-VEN, and 4 in DLBCL 621-VEN [2 each in 3.75- and 7.5-mg/kg] cohorts). Using flow cytometry, saturation of ABBV-621 binding to decoy receptors on neutrophils was observed at 2 h postdosing, followed by dose-dependent desaturation of receptors in pts with DLBCL at 48-168 h. In AML 621-VEN pts, ABBV-621 remained bound to decoy receptors for up to 168 h; in DLBCL 621-VEN pts, the duration of binding was higher at ABBV-621 7.5 mg/kg compared with 3.75 mg/kg. In AML, the baseline frequency of myeloblasts was higher in pts with PD than CR, while that of myelomonocytes was higher in the pt with CR. The frequency of myeloblasts and myelomonocytes expressing DR4 and DR5 at baseline was highest in the pt with CR (Figure). Conclusions: ABBV-621 was tolerated and showed antitumor activity in combination with VEN in pts with RR AML. Disclosures de Jonge: Faron Pharmaceuticals Ltd.: Consultancy. Carneiro:Actuate Therapeutics: Research Funding; Bayer: Research Funding; Pfizer: Research Funding; AstraZeneca: Research Funding; Medimmune: Research Funding; Astellas: Research Funding; AbbVie: Research Funding. Devriese:MSD: Consultancy. Penugonda:AbbVie: Employment, Other: Stock/stock options. Petrich:Abbvie: Employment, Equity Ownership. Nuthalapati:AbbVie: Employment, Other: Stock/stock options. Motwani:AbbVie: Employment, Other: Stock/stock options. Modi:AbbVie: Employment, Other: Stock/stock options. Chang:AbbVie: Employment, Other: Stock/stock options. Calvo:Celgene: Consultancy; Roche/Genentech: Consultancy, Other: travel/accommodations/expenses; Seattle Genetics: Consultancy; AstraZeneca: Consultancy, Research Funding; PsiOxus: Consultancy; Amcure: Consultancy; START: Other: stock/ownership interests, Research Funding; Janssen-Cilag: Consultancy; EUSA Pharma: Consultancy; Novartis: Consultancy, Research Funding, Speakers Bureau; Oncoart Associated: Other: stock/ownership interests; Guidepoint Global: Consultancy; Nanobiotix: Consultancy; HM Hospitales Group: Honoraria; AbbVie: Consultancy; BeiGene: Research Funding; Servier: Consultancy; International Cancer Consultants: Other: stock/ownership interests; Foundation INTHEOS: Other: president and founder; Gerson Lehrman Group: Consultancy; Pfizer: Consultancy. Moreno:Puma Biotechnology: Consultancy; Sanofi/Regeneron: Other: travel/accommodations/expenses.

Survival of aging CD264+ and CD264- populations of human bone marrow mesenchymal stem cells is independent of colony-forming efficiency.

In vivo mesenchymal stem cell (MSC) survival is relevant to therapeutic applications requiring engraftment and potentially to nonengraftment applications as well. MSCs are a mixture of progenitors at different stages of cellular aging, but the contribution of this heterogeneity to the survival of MSC implants is unknown. Here, we employ a biomarker of cellular aging, the decoy TRAIL receptor CD264, to compare the survival kinetics of two cell populations in human bone marrow MSC (hBM-MSC) cultures. Sorted CD264+ hBM-MSCs from two age-matched donors have elevated β-galactosidase activity, decreased differentiation potential and form in vitro colonies inefficiently relative to CD264- hBM-MSCs. Counterintuitive to their aging phenotype, CD264+ hBM-MSCs exhibited comparable survival to matched CD264- hBM-MSCs from the same culture during in vitro colony formation and in vivo when implanted ectopically in immunodeficient NIH III mice. In vitro and in vivo survival of these two cell populations were independent of colony-forming efficiency. These findings have ramifications for the preparation of hBM-MSC therapies given the prevalence of aging CD264+ cells in hBM-MSC cultures and the popularity of colony-forming efficiency as a quality control metric in preclinical and clinical studies with MSCs.

EXTH-57. PRECLINICAL COMBINATION OF ONC201 WITH RADIOTHERAPY OR TEMOZOLOMIDE IN GBM, DIPG AND ATRT CELL LINES RESULTS IN DOPAMINE RECEPTOR ANTAGONISM, ATF4 INDUCTION AND CELL DEATH

Abstract CNS tumors are one of the most lethal cancers in children and young adults. We previously reported that first-in-class small-molecule imipridone ONC201 can antagonize dopamine receptor D2 (DRD2), inactivate ERK/AKT, induce the integrated stress response (ISR), upregulate pro-apoptotic TRAIL receptor DR5, deplete cancer stem cells, and induce growth arrest or cell death in tumor cells. ONC201 crosses the blood-brain barrier and has induced durable tumor regressions in adult and pediatric H3K27M-mutant glioma patients. We hypothesized that ONC201 may synergize with radiotherapy or temozolomide in brain tumors. Glioblastoma (GBM: SNB19, T98G and U251), diffuse intrinsic pontine glioma (DIPG: SF8628) and atypical teratoid rhabdoid tumor (ATRT: BT-12, BT-16) cell lines were tested using cell viability or colony formation assays with ONC201 up to 20 μM alone or in combination with radiotherapy up to 8 Gy or temozolomide up to 100 μM. We observed synergy between ONC201 and radiation or temozolomide by multiple assays. We observed induction of PKA substrate phosphorylation as a marker of DRD2 antagonism, induction of ATF4 as a marker of ISR activation, and multiple markers of cell death in treated brain tumor cells. We are evaluating the relevance of mitochondrial protease ClpP, a recently described binding target of ONC201, in ONC201-induced glioma cell death. We have observed that knockdown of ClpP strongly protects multiple human cancer cell lines from ONC201-mediated cytotoxicity. Thus, we are exploring the potential interplay between ClpP, dopamine receptors, the ISR and TRAIL signaling pathways after single agent or combinatorial treatments. Our data suggests that ONC201 may be combined synergistically with temozolomide or radiation to address gliomas, along with potential pharmacodynamic biomarkers.