Fas-FasL Interaction Research Articles

Abstract 3995: A novel chimeric Fas signal redirect receptor enhances the durability of anti-tumor activity and serial killing potential of CAR T cells

Abstract Chimeric antigen receptor (CAR) T-cell therapies have demonstrated remarkable success in hematological malignancies but only modest efficacy in solid tumors. Apoptosis induced by Fas receptor signaling can be a substantial barrier to CAR T-cell antitumor activity, as many solid tumors express high levels of Fas ligand (FasL). Here we describe a novel synthetic construct where the ectodomain of Fas receptor is fused to the signaling endodomain of a stimulatory receptor, creating a Fas signal redirect receptor (Fas-SRR). This unique design not only prevents Fas-dependent cell death, but also augments the long-term killing potential of induced pluripotent stem cell (iPSC)-derived CAR-T (CAR-iT) cells. Fas-SRR constructs with unique T-cell activation signaling endodomains were designed and compared to two control arms: a dominant negative receptor (Fas-DNR), which blocks Fas signal but does not promote activation; and a Fas-41BB fusion receptor, where the 41BB endodomain is fused to FasR ectodomain to direct activation upon FasL:Fas engagement. Fas-SRR designs were validated in Jurkat reporter cells treated with Fas agonist to measure signal redirection via Fas-SRR. To conduct a head-to-head comparison, CAR-iT cells were engineered to express a CAR under the regulation of the TRAC locus and to express either a Fas-DNR, a Fas-41BB, or FAS-SRR constructs at high purity (>90% transgene expression). No major differences were seen in maturation phenotype (>95% TRAC-CAR expression) of these cells, indicating compatibility of the FAS-SRR constructs with CAR-iT cell generation. Functional testing of the Fas-SRR+ CAR-iT cells was performed in a long-term restimulation assay where effector cells were repeatedly exposed to target cells over multiple rounds of co-culture. Complete loss of target cell lysis was observed by round six in the co-cultures with FAS-DNR cells, where loss of CAR-iT cell persistence led to accumulation of target cells. After eight rounds of co-culture, the Fas-41BB cells and the majority of Fas-SSR cell constructs also began to exhibit minimal activity toward target cells. However, the top Fas-SRR cell constructs continued to show durable antitumor activity (>97% cytolysis) through the end of the 9-round rechallenge assay. Of note, GSEA analysis identified significant upregulation of NFkB and RELA target genes in cells having the top FAS-SRR construct versus the less durable designs. These results reinforce the advantage of attenuating Fas-FasL interactions to prevent apoptosis and, more importantly, demonstrate the unique therapeutic value in redirecting Fas signaling to improve T-cell potency over an extended duration. Additional studies are underway to further investigate the implications of Fas signal redirection in CAR T and CAR-iT cells and to further understand the module of genes involved in supporting serial stimulation performance. Citation Format: Christopher Ecker, Eigen Peralta, Hui-Yi Chu, Lorraine Loter, Masanao Tsuda, Earl Avramis, Matthew Denholtz, Alec Witty, Tom Lee, Bahram Valamehr. A novel chimeric Fas signal redirect receptor enhances the durability of anti-tumor activity and serial killing potential of CAR T cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3995.

Utilizing Chemotherapy to Enhance the Anti-Tumor Properties of Ex Vivo Expanded Gamma Delta (γδ) T Cells Against Acute Myeloid Leukemia

Background: Acute myeloid leukemia (AML) is the second most common type of blood cancer in children with a high rate of treatment failure and aggressive relapse. While allogeneic HSCT offers a cure, limitations arise in achieving remission prior to transplant. Immunotherapy-based approaches can induce remission, gaining interest in AML. Here, we explore the use of gamma delta (γδ) T cells as a promising tool to fulfill this unmet need. Unlike predominant alpha beta (αβ) T cells, γδ T cells do not require antigen presentation and identify their targets in a major histocompatibility complex (MHC) independent manner. Allogeneic γδ T cells thus have minimal risk of causing graft-versus-host disease (GvHD), creating ‘off-the-shelf’ cellular therapeutics. This would be ideal to target AML, especially given the aggressive nature of relapsed disease. Cytotoxic mechanisms used by γδ T cells include recognition of cellular stress molecules such as NKG2D and DNAM-1 receptor ligands on target cells, activation of death receptor pathway through Fas-FasL and TRAIL-R interactions, as well as γδ ΤCR mediated killing through recognition of butyrophilins (BTNs) on target cells. These stress molecules are expressed on AML cells and can be further upregulated through chemotherapeutic agents such as azacitidine (a hypomethylating agent) and venetoclax (BCL-2 antagonist), drugs currently in use to treat relapsed AML. Here, we tested these drugs in combination with γδ T cells to target AML. Methods Our studies explored four different AML cell lines (Kasumi-1, Nomo-1, MV4-11 and MOLM13). Each one was respectively treated at their corresponding inhibitory concentration 25 (IC 25) and 50 (IC 50) of azacitidine and/or venetoclax for 24 hours. After treatment, AML cells were assessed by flow cytometry for expression of NKG2D and DNAM-1 ligands, death receptor pathway molecules (CD95, TRAIL-R1/R2) as well as the butyrophillins (BTN2A and BTN3A1) to elucidate which pathways are over-expressed, aiding in γδ T cell targeting and cytotoxicity. Next, we co-cultured AML cells pre-treated with azacitidine and/or venetoclax with γδ T cells and measured cytotoxicity using a flow cytometry-based assay and a bioluminescence assay. Results: Each cell line expressed a unique pattern of markers at baseline. Cell lines treated with azacitidine had a robust expression of the NKG2D ligands ULBP1, ULBP2/5/6 and ULBP3. Azacitidine also increased CD155 and TRAIL-R2 in Nomo-1 while CD112 increased in MOLM13. Most venetoclax-treated AML cells over-expressed BTN2A and BTN3A1 along with CD95 in MOLM13. Cell lines were then treated with a combination of both drugs. Dual treatment of cells resulted in a significant increase in expression of most NKG2D markers as well the death receptor Fas (CD95). Additionally, increase in CD155 as well as BTNs was seen in several cell lines. Importantly, azacitidine and venetoclax had minimal effects on the viability of γδ Τ cells when treated for 24 hours. In vitro cytotoxicity studies indicate increased cell death across multiple AML cell lines when γδ T cells were co-cultured with cells pretreated with azacitidine and venetoclax. Conclusions: Azacitidine and venetoclax treatment resulted in upregulation of several markers involved in γδ Τ cell-mediated cytotoxicity. Ex vivo expanded γδ Τ cells combined with chemotherapy-treated AML cells resulted in increased overall cytotoxicity, which is likely both additive and synergistic. Our next steps include preclinical validation of this combinatorial approach in an in-vivo mouse study.

IDH2 and TET2 mutations synergize to modulate T Follicular Helper cell functional interaction with the AITL microenvironment.

Angioimmunoblastic Tcell lymphoma (AITL) is a peripheral Tcell lymphoma that originates from T follicular helper (Tfh) cells and exhibits a prominent tumor microenvironment (TME). IDH2 and TET2 mutations co-occur frequently in AITL, but their contribution to tumorigenesis is poorly understood. We developed an AITL mouse model that is driven by Idh2 and Tet2 mutations. Malignant Tfh cells display aberrant transcriptomic and epigenetic programs that impair TCR signaling. Neoplastic Tfh cells bearing combined Idh2 and Tet2 mutations show altered cross-talk with germinal center B cells that promotes B cell clonal expansion while decreasing Fas-FasL interaction and reducing B cell apoptosis. The plasma cell count and angiogenesis are also increased in the Idh2-mutated tumors, implying a major relationship between Idh2 mutation and the characteristic AITL TME. Our mouse model recapitulates several features of human IDH2-mutated AITL and provides a rationale for exploring therapeutic targeting of Tfh-TME cross-talk for AITL patients.

Inhibiting Lysine Demethylase 1A Improves L1CAM-Specific CAR T Cell Therapy by Unleashing Antigen-Independent Killing via the FAS-FASL Axis.

Simple SummarySolid tumor cells can lose or heterogeneously express antigens to become resistant to chimeric antigen receptor (CAR) T cell therapy. Here, we explore whether epigenetic manipulation to unleash antigen-independent killing mechanisms can overcome this hurdle. KDM1A is overexpressed in many cancers and removes lysine methylation on histones that keeps the DNA firmly packed to selectively activate or repress gene activity, depending on the specific lysine target. KDM1A also regulates the expression of nonhistone proteins. We inhibited KDM1A in the childhood tumor, neuroblastoma, to increase FAS expression on tumor cells. The FAS receptor can be triggered to induce cell death when bound by the FAS ligand on CAR and other activated T cells present in the tumor environment, even if the tumor cells lack the target antigen. FAS upregulation via KDM1A inhibition sensitized neuroblastoma cells to FAS-FASL-mediated killing and augmented CAR T cell therapy against antigen-poor or even antigen-negative neuroblastoma. Chimeric antigen receptor (CAR) T cell therapy has emerged as a promising treatment strategy, however, therapeutic success against solid tumors such as neuroblastoma remains modest. Recurrence of antigen-poor tumor variants often ultimately results in treatment failure. Using antigen-independent killing mechanisms such as the FAS receptor (FAS)-FAS ligand (FASL) axis through epigenetic manipulation may be a way to counteract the escape achieved by antigen downregulation. Analysis of public RNA-sequencing data from primary neuroblastomas revealed that a particular epigenetic modifier, the histone lysine demethylase 1A (KDM1A), correlated negatively with FAS expression. KDM1A is known to interact with TP53 to repress TP53-mediated transcriptional activation of genes, including FAS. We showed that pharmacologically blocking KDM1A activity in neuroblastoma cells with the small molecule inhibitor, SP-2509, increased FAS cell-surface expression in a strictly TP53-dependent manner. FAS upregulation sensitized neuroblastoma cells to FAS-FASL-dependent killing and augmented L1CAM-directed CAR T cell therapy against antigen-poor or even antigen-negative tumor cells in vitro. The improved therapeutic response was abrogated when the FAS-FASL interaction was abolished with an antagonistic FAS antibody. Our results show that KDM1A inhibition unleashes an antigen-independent killing mechanism via the FAS-FASL axis to make tumor cell variants that partially or totally suppress antigen expression susceptible to CAR T cell therapy.

Pathophysiology and management of Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis

Background:  Epidermal necrolysis (EN) is an acute mucocutaneous reaction syndrome characterized by extensive necrosis and epidermal exfoliation and can cause death. The initial lesion is in the form of erythematous macules, then progressively grow to sagging blister lesion and subsequent epidermal peeling. The causes of SJS and TEN may vary such as infections, vaccinations, drugs, systemic diseases, and food. However, the main cause is the drug as found in many cases.  Methods:  The pathophysiology of the EN is still unclear. Pathologically, tissue damage in the form of epidermal necrolysis is a picture of mass keratinocyte cell death through apoptosis. The stimuli that can induce apoptosis include cellular stress, DNA damage and intracellular cytokines. It may as a result of the role of cytotoxic T cells against keratinocytes, through perforin-granzyme B or Fas-FasL interactions and granulysin. Another theory of SJS-TEN pathophysiology is the slow acetylation (drug metabolic disorder) and the theory of genetic susceptibility. Result:  Finally, we include a comprehensive review of well-established widely available therapies in SJS-TEN patients.  Discussion:  It requires rapid diagnosis, suspension of suspected drug as soon as possible, supportive therapy and specific therapy Conclusion:  An understanding of the pathophysiology and current management of SJS and TEN is expected to assist in the prevention of disease and early diagnosis and can provide more effective therapy for SJS-TEN treatment   Keywords:  Epidermal necrolysis, SJS-TEN, perforin-granzyme B, Fas-FasL interactions, granulysin

Herpes Zoster Duplex Unilateralis as a manifestation of severe lymphopenia in COVID19

To the editor in chief, SARS-CoV2 (severe acute respiratory syndrome coronavirus-2), a novel coronavirus was first reported in December of 2019 from Wuhan, China as an aetiological agent causing a new infectious respiratory disease (coronavirus disease 2019- COVID-19). The main clinical manifestations of COVID-19 are fever, cough, fatigue, dyspnoea and muscle aches. Herpes zoster is characterized by several groups of painful vesicles on an erythematous base with a distribution in a unilateral dermatome involving the skin and/or mucosa. Herpes zoster is caused by varicella zoster virus which remains dormant in the sensory root ganglion contained by the immune system particularly CD lymphocytes (Wollina, 2017). This characteristic presentation is seen in an immunocompetent host. Severe forms of Herpes zoster not respecting the borders of a dermatome have been described. They are (a) Disseminated Herpes zoster that is, lesions extending over three contiguous dermatomes or lesions going outside the original dermatome. (b) Herpes zoster Duplex—here the lesions involve two non-contiguous dermatomes. If the dermatome involved are unilateral then it is known as Herpes Zoster Duplex Unilateralis and if present bilaterally then—Herpes Zoster Duplex Bilateralis (Jung et al., 2000). The non-contiguous variants are rare in both immunocompetent and immunocompromised host and represent a viraemic spread of VZV due to decrease in lymphocyte count and/or function. Classical Dermatomal Herpes Zoster has been described as a marker of subclinical COVID19 infection (Tartari et al., 2020). We are presenting a case of Herpes Zoster Duplex Unilateralis involving left ophthalmic division of trigeminal nerve (V1) and left Thoracic 10 (T10) dermatome in a patient of COVID19 with severe lymphopenia. A 62-year-old otherwise healthy male presented with highly painful vesicular lesions on an erythematous base involving the left ophthalmic division of trigeminal nerve (Day 6) and left thoracic 10 (T10) (Day 8) dermatome occurring 2 days apart. The vesicles ranged from 0.3 mm to 1 cm in size and had necrotic element at some places. Hutchinson sign was positive. A diagnosis of Herpes Zoster Duplex Unilateralis involving left ophthalmic division of trigeminal nerve and left Thoracic 10 (T10) dermatome was observed. The patient had fever (101–103°F) with malaise for preceding 5 days of appearance of vesicles. His COVID19 RT PCR test was positive (Day 8), however, evaluation for HIV status, diabetes, any immunosuppressive state and malignancy was negative. HRCT thorax showed multiple ground glass opacities in both the lungs with CT severity score being 18/30. His LDH levels were 229 units/L (normal range 135–225 U/L), D-dimer 3,422.26 (0–500 ng/ml), IL-6 levels 23 (normal range 0–7 pg/ml). Troponin-T levels determined by Card test, serum ferritin levels and liver function tests were normal. Total leucocyte count was 7,100 cells/mm3 (4000–11000 cells/mm3 normal range). However differential eucocyte count showed neutrophilia (90%) and relative lymphopenia (2.2%), whereas the normal range is 20%–40%. The patient was treated according to institutional COVID19 protocol and was given piperacillin tazobactam 4.5 mg thrice a day injection, remdesivir 200 mg slow iv infusion and dexamethasone injection 4 mg once daily , low molecular weight heparin 6 mg twice a day subcutaneously for 5 days. For VZV lesions, oral acyclovir was given at a dose of 800mg five times a day for 10 days after which he recovered with mild post herpetic neuralgia. Herpes Zoster Duplex Unilateralis represents a viraemic spread of VZV, probably due to decreased immune protection. In our patient lymphocyte percentage was 2.2% representing a severe lymphopenia. We tried to look into the possible explanations: In COVID 19 patients, the inflammatory cytokine storm is likely a key factor behind the observed lymphopenia. The serum level of pro-inflammatory cytokines, such as TNF-α and IL-6, have been closely correlated with lymphopenia, while recovered patients show close to normal levels of such cytokines (Mazzoni et al., 2020). Autopsy studies on lymphoid organs collected from several patients who succumbed to the disease revealed massive lymphocyte death, which was attributed to high levels of IL-6 as well as Fas–FasL interactions. Our patient also had high IL 6 levels and clinical features suggestive of cytokine storm. COVID-19 infection can result in exhaustion of T cells. A recent study has found both CD4+ and CD8+ T cells from COVID-19 patients had increased cell surface expression of programmed cell death protein 1 (PD-1) and T cell immunoglobulin and mucin domain 3 (Tim-3), the two markers of T cell exhaustion (Diao et al., 2020). The SARS-CoV-2 can directly infect T cells. This infection can interfere with T cell expansion. A report suggests that some genes involved in T cell activation and function, such as MAP2K7 and SOS1 are downregulated in the T cells of severe COVID-19 patients (Ouyang et al., 2020). All these mechanisms may be an explanation to the relative lymphopenia in our patient with an unusual presentation of Herpes Zoster. Nil. None declared.

β2 adrenergic receptor-mediated signaling regulates the immunosuppressive potential of myeloid-derived suppressor cells.

Catecholamines released by sympathetic nerves can activate adrenergic receptors present on nearly every cell type, including myeloid-derived suppressor cells (MDSCs). Using in vitro systems, murine tumor models in wild-type and genetically modified (β2-AR-/-) mice, and adoptive transfer approaches, we found that the degree of β2-AR signaling significantly influences MDSC frequency and survival in tumors and other tissues. It also modulates their expression of immunosuppressive molecules such as arginase-I and PD-L1 and alters their ability to suppress the proliferation of T cells. The regulatory functions of β2-AR signaling in MDSCs were also found to be dependent upon STAT3 phosphorylation. Moreover, we observed that the β2-AR-mediated increase in MDSC survival is dependent upon Fas-FasL interactions, and this is consistent with gene expression analyses, which reveal a greater expression of apoptosis-related genes in β2-AR-/- MDSCs. Our data reveal the potential of β2-AR signaling to increase the generation of MDSCs from both murine and human peripheral blood cells and that the immunosuppressive function of MDSCs can be mitigated by treatment with β-AR antagonists, or enhanced by β-AR agonists. This strongly supports the possibility that reducing stress-induced activation of β2-ARs could help to overcome immune suppression and enhance the efficacy of immunotherapy and other cancer therapies.

Steven-Johnson Syndrome in Child

Steven-Johnson Syndrome and NET (toxic epidermal necrolysis), different expressions of the same condition were named according to the percentage of affected skin: [10% in Steven-Johnson Syndrome and]30% in NET. Small ages may be a target for these rare diseases, in direct relation to drug abuse (antibiotics, NSAIDs, antiepileptics, etc.). Survival depends on the rapid response of the causative agent, the early investigation of the therapy to block Fas-FasL interaction and to reestablish skin integrity (Fas-receptor on the surface of cells involved in apoptosis). Massive skin damage is associated with a severe prognosis, as is the age of the baby.It is necessary to use wise the medication or automedication for a complete and effective prevention of Steven-Johnson Syndrome.

T cells genetically engineered to overcome death signaling enhance adoptive cancer immunotherapy.

Across clinical trials, T cell expansion and persistence following adoptive cell transfer (ACT) have correlated with superior patient outcomes. Herein, we undertook a pan-cancer analysis to identify actionable ligand-receptor pairs capable of compromising T cell durability following ACT. We discovered that FASLG, the gene encoding the apoptosis-inducing ligand FasL, is overexpressed within the majority of human tumor microenvironments (TMEs). Further, we uncovered that Fas, the receptor for FasL, is highly expressed on patient-derived T cells used for clinical ACT. We hypothesized that a cognate Fas-FasL interaction within the TME might limit both T cell persistence and antitumor efficacy. We discovered that genetic engineering of Fas variants impaired in the ability to bind FADD functioned as dominant negative receptors (DNRs), preventing FasL-induced apoptosis in Fas-competent T cells. T cells coengineered with a Fas DNR and either a T cell receptor or chimeric antigen receptor exhibited enhanced persistence following ACT, resulting in superior antitumor efficacy against established solid and hematologic cancers. Despite increased longevity, Fas DNR-engineered T cells did not undergo aberrant expansion or mediate autoimmunity. Thus, T cell-intrinsic disruption of Fas signaling through genetic engineering represents a potentially universal strategy to enhance ACT efficacy across a broad range of human malignancies.

Abstract PR05: T-cells engineered to overcome death signaling within the tumor microenvironment enhance adoptive cancer immunotherapy

Abstract Across clinical trials, T-cell expansion and persistence following adoptive cell transfer (ACT) has correlated with superior patient outcomes. Herein, we undertook a pan-cancer analysis across human tumors to identify potentially actionable ligand/receptor pairs that might limit T-cell function and persistence following ACT. We discovered that FASLG, the gene encoding the apoptosis-inducing ligand FasL, is overexpressed within the majority of human tumor microenvironments. Further, we uncovered that Fas, the receptor for FasL, is highly expressed on patient-derived T-cells used for ACT. We hypothesized that a cognate Fas-FasL interaction within the tumor microenvironment might limit both T-cell persistence and antitumor efficacy. We discovered that genetic engineering of Fas variants impaired the ability to bind FADD function as dominant negative receptors (DNRs) in Fas-competent mouse and human T-cells, rescuing cells from FasL-induced apoptosis. Fas DNR-engineered T-cells exhibited enhanced persistence within tumors following ACT, resulting in superior cancer regression and overall survival in solid and hematologic malignancies treated with TCR or CAR-modified cells. Despite enhanced longevity, Fas DNR-engineered T-cells did not undergo aberrant clonal expansion, demonstrating the safety of this approach. Thus, cell-intrinsic “insulation” of T-cells from the negative influence of FasL is a potentially universal strategy to enhance ACT efficacy across a broad range of human malignancies. Citation Format: Christopher A. Klebanoff. T-cells engineered to overcome death signaling within the tumor microenvironment enhance adoptive cancer immunotherapy [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr PR05.

Targeted deletion of the aryl hydrocarbon receptor in dendritic cells prevents thymic atrophy in response to dioxin.

In nearly every species examined, administration of the persistent environmental pollutant, 2,3,7,8-tetrachlorodibenzo-p-dioxin (dioxin, TCDD) causes profound immune suppression and thymic atrophy in an aryl hydrocarbon receptor (AhR) dependent manner. Moreover, TCDD alters the development and differentiation of thymocytes, resulting in decreases in the relative proportion and absolute number of double positive (DP, CD4+CD8+) thymocytes, as well as a relative enrichment in the relative proportion and absolute number of double negative (DN, CD4-CD8-) and single-positive (SP) CD4+CD8- and CD4-CD8+ thymocytes. Previous studies suggested that the target for TCDD-induced thymic atrophy resides within the hemopoietic compartment and implicated apoptosis, proliferation arrest of thymic progenitors, and emigration of DN thymocytes to the periphery as potential contributors to TCDD-induced thymic atrophy. However, the precise cellular and molecular mechanisms involved remain largely unknown. Our results show that administration of 10 µg/kg TCDD and 8mg/kg 2-(1H-indol-3-ylcarbonyl)-4-thiazolecarboxylic acid methyl ester (ITE) induced AhR-dependent thymic atrophy in mice on day 7, whereas 100mg/kg indole 3-carbinol (I3C) did not. Though our studies demonstrate that TCDD triggers a twofold increase in the frequency of apoptotic thymocytes, TCDD-induced thymic atrophy is not dependent on Fas-FasL interactions, and thus, enhanced apoptosis is unlikely to be a major mechanistic contributor. Finally, our results show that activation of the AhR in CD11c+ dendritic cells is directly responsible for TCDD-induced alterations in the development and differentiation of thymocytes, which results in thymic atrophy. Collectively, these results suggest that CD11c+ dendritic cells play a critical role in mediating TCDD-induced thymic atrophy and disruption of T lymphocyte development and differentiation in the thymus.

Activation of the JNK-c-Jun pathway in response to irradiation facilitates Fas ligand secretion in hepatoma cells and increases hepatocyte injury.

BackgroundIt is well established that some irradiated liver non-parenchymal cells secrete pro-inflammatory cytokines to facilitate the development of radiation-induced liver disease. However, little is known on whether the irradiated hepatoma cells-mediated non-irradiated hepatocyte injury occurs in HCC patients. Here, we elucidated the roles of the irradiated hepatoma cells in driving non-irradiated hepatocyte injury and its underlying mechanism.MethodsSMMC7721 cells were cultured and divided into irradiated (4-Gy X-ray, R) and non-irradiated (NR) groups. At 24th hour after irradiation, conditioned medium (CM) from these cultures was mixed with normal culture medium in specific proportions, and termed as 7721-R-CM and 7721-NR-CM. Following incubation with these CM compound, the biological characteristics of L02 cells related to liver cell injury including viability, apoptosis and liver dysfunction indices were comparatively analyzed. Simultaneously, the levels of proliferation- and apoptosis-related cytokines in irradiated and non-irradiated SMMC7721 cells were also measured. FasL as a cytokine with significantly differential expression, was selected to clarify its effects on L02 apoptosis. Subsequently, FasL expression following irradiation was examined in SMMC7721 and other HCC cells with varying malignant potentials, as well as in HCC tissues, the related mechanism of higher expression of FasL in irradiated HCC cells was further investigated.ResultsApoptosis and liver dysfunction indices were all significantly enhanced in L02 cells treated with 7721-R-CM, whereas viability was suppressed, compared to those with 7721-NR-CM stimulation. FasL was identified as a leading differential cytokine in the irradiated SMMC7721 cells. Higher proportion of apoptosis was also found in L02 cells following FasL incubation. A recombinant Fas-Fc protein, which blocks Fas-FasL interaction, ameliorated 7721-R-CM-induced apoptosis in L02 cells. FasL was highly expressed in a dose-dependent manner, and peaked at the 24th hour post-irradiation in different HCC cells and their culture supernatant. Meanwhile, phosphorylation levels of JNK, ERK, Akt, and p38 were all upregulated significantly in irradiated HCC cells. But, only JNK inhibition was validated to block radiation-induced FasL expression in HCC cells. c-Jun, the target transcription factor of JNK, was also activated.ConclusionIn HCC cells, the JNK-c-Jun pathway plays an important role in mediating irradiation- induced FasL expression, which may be critical in determining non-irradiated hepatocyte injury.Electronic supplementary materialThe online version of this article (doi:10.1186/s13046-016-0394-z) contains supplementary material, which is available to authorized users.

Thioreductase-Containing Epitopes Inhibit the Development of Type 1 Diabetes in the NOD Mouse Model.

Autoreactive CD4+ T cells recognizing islet-derived antigens play a primary role in type 1 diabetes. Specific suppression of such cells therefore represents a strategic target for the cure of the disease. We have developed a methodology by which CD4+ T cells acquire apoptosis-inducing properties on antigen-presenting cells after cognate recognition of natural sequence epitopes. We describe here that inclusion of a thiol-disulfide oxidoreductase (thioreductase) motif within the flanking residues of a single MHC class II-restricted GAD65 epitope induces GAD65-specific cytolytic CD4+ T cells (cCD4+ T). The latter, obtained either in vitro or by active immunization, acquire an effector memory phenotype and lyse APCs by a Fas–FasL interaction. Furthermore, cCD4+ T cells eliminate by apoptosis activated bystander CD4+ T cells recognizing alternative epitopes processed by the same APC. Active immunization with a GAD65 class II-restricted thioreductase-containing T cell epitope protects mice from diabetes and abrogates insulitis. Passive transfer of in vitro-elicited cCD4+ T cells establishes that such cells are efficient in suppressing autoimmunity. These findings provide strong evidence for a new vaccination strategy to prevent type 1 diabetes.

Modulation of Fas-Fas Ligand Interaction Rehabilitates Hypoxia-Induced Apoptosis of Mesenchymal Stem Cells in Ischemic Myocardium Niche.

Mesenchymal stem cells (MSCs) have the potential to repair and regenerate ischemic heart tissue; however, the poor viability of transplanted MSCs in the ischemic region is a major obstacle to their therapeutic use. This cell death is caused by Fas and Fas ligand (FasL) interactions under harsh conditions. To investigate improving the survival and therapeutic effects of MSCs, we focused our research on Fas-FasL-mediated cell death. In this study, we found that the poor viability of transplanted MSCs was caused by Fas-FasL interactions between host ischemic myocardial cells and implanted MSCs. In addition, we found that increased Fas expression and the corresponding decrease of cell survival were in close relation to hypoxic MSCs treated with FasL and H2O2. When MSCs were treated with a recombinant Fas/Fc chimera (Fas/Fc) inhibiting Fas-FasL interactions, the expressions of proapoptotic proteins including caspase-8, caspase-3, Bax, and cytochrome-c were attenuated, and the survival of MSCs was recovered. In ischemia-reperfusion injury models, the interaction between FasL in ischemic heart and Fas in implanted MSCs caused a loss of transplanted MSCs, whereas the inhibition of this interaction by Fas/Fc treatment improved cell survival and restored heart function. Thus, our study suggests that Fas-FasL interactions are responsible for activating cell death signaling in implanted stem cells and could be a potential target for improving therapeutic efficacy of stem cells in treating ischemic heart diseases.

IL-27 stimulates human NK-cell effector functions and primes NK cells for IL-18 responsiveness.

IL-27, a member of the IL-12 family of cytokines, is produced by APCs, and displays pro- and anti-inflammatory effects. How IL-27 affects human NK cells still remains unknown. In this study, we observed that mature DCs secreted IL-27 and that blockade of IL-27R (CD130) reduced the amount of IFN-γ produced by NK cells during their coculture, showing the importance of IL-27 during DC-NK-cell crosstalk. Accordingly, human rIL-27 stimulated IFN-γ secretion by NK cells in a STAT1-dependent manner, induced upregulation of CD25 and CD69 on NK cells, and displayed a synergistic effect with IL-18. Preincubation experiments demonstrated that IL-27 primed NK cells for IL-18-induced IFN-γ secretion, which was associated with an IL-27-driven upregulation of T-bet expression. Also, IL-27 triggered NKp46-dependent NK-cell-mediated cytotoxicity against Raji, T-47D, and HCT116 cells, and IL-18 enhanced this cytotoxic response. Such NK-cell-mediated cytotoxicity involved upregulation of perforin, granule exocytosis, and TRAIL-mediated cytotoxicity but not Fas-FasL interaction. Moreover, IL-27 also potentiated Ab-dependent cell-mediated cytotoxicity against mAb-coated target cells. Taken together, IL-27 stimulates NK-cell effector functions, which might be relevant in different physiological and pathological situations.

Abstract 959: FAS mutations induce therapeutic resistance in non-Hodgkin lymphomas

Abstract Lymphomas are common (1/30 Canadians), but responses to chemotherapy depend on the tumour biology. We sequenced > 300 lymphomas at diagnosis and at relapse, identified FAS as a possible tumour suppressor gene and found that mutant FAS is associated with therapeutic resistance. FAS is the death receptor that initiates the extrinsic apoptotic pathway once activated by FAS ligand (FASL). Our studies indicated that the most common FAS mutation is a dominant negative allele whose product inhibits FAS-mediated apoptosis. This allele induces resistance to doxorubicin in murine lymphoma cells transplanted into syngeneic immune competent C57BL/6 mice but, unexpectedly, the allele has no effect on chemosensitivity in cultured lymphoma lines in vitro. Because FAS signaling is initiated by FASL from neighboring cells, we asked whether chemotherapy induces FAS or FASL expression in immune cells, thereby activating apoptosis in vivo but not in vitro. Indeed, exposure to chemotherapy induced FAS in primary and malignant B cells and increased FASL in benign T cells. Thus, we hypothesize that chemotherapy may induce an anti-tumour immune response mediated by FAS-FASL interactions, and that FAS mutations cause therapeutic resistance by blocking the chemotherapy-induced immune response. We will extend this work by evaluating the role of the immune response in chemotherapy-induced lymphoma apoptosis and by identifying therapies that will target FAS mutant lymphomas. Citation Format: Nathalie Johnson, Denis Gaucher, Ryan Morin, Randy Gascoyne, Joseph Connors, Marco Marra, Jerry Pelletier, Hawley Rigsby, Koren Mann. FAS mutations induce therapeutic resistance in non-Hodgkin lymphomas. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 959. doi:10.1158/1538-7445.AM2014-959

Disruption of fas-fas ligand signaling, apoptosis, and innate immunity by bacterial pathogens.

Fas ligand (FasL, CD95L) is a type-II membrane protein withinthe tumor necrosis factor (TNF) superfamily of death receptors [1].FasL shares 25%–30% sequence homology with related familymember proteins such as tumor necrosis factor alpha (TNFa) andTNF-related apoptosis-inducing ligand (TRAIL), with the mostsimilarity present in the C-terminal homology ectodomain thatextends into the extracellular space for receptor binding [2]. FasLengages and trimerizes the death receptor Fas (CD95) on cellsurfaces to initiate the extrinsic apoptosis pathway [3]. The Fas-FasL interaction recruits the Fas-associated death domain adapterprotein (FADD) via death domain binding, which interacts withdimerized procaspase-8 to form the death-inducing signalingcomplex (DISC) [4]. Caspase-8 catalyzes its autoactivation,followed by the proteolytic conversion of downstream effectorcaspases such as caspase-3 and -7 into their mature forms [5].Effector caspases direct cell death by apoptosis, which results innuclear and cytoplasmic condensation followed by cellularfragmentation into membrane-bound apoptotic bodies [6].Caspase-activated DNase (CAD) cleaves genomic DNA betweennucleosomes to generate short fragments prior to cellularcondensation and membrane blebbing [7]. Membrane fragmentsare usually taken up by other cells and degraded in phagosomesvia a process known as efferocytosis. Efferocytosis of apoptotic cellscontributes to the resolution of inflammation by rapidly clearingcytotoxic cellular debris, and defects in this process can lead toinflammatory diseases such as acute lung injury [8].Although FasL is expressed by many cell types, it is primarilyrecognized as associated with activated T lymphocytes and naturalkiller (NK) cells. FasL-dependent apoptosis plays important rolesin tissue remodeling and the deletion of potentially autoreactivethymocytes to maintain immune tolerance during development,and it also contributes to tumor cell clearance by effector NK cells[9–11]. Though apoptosis has traditionally been defined asnoninflammatory during these processes, FasL-induced cell deathhas been shown to be highly proinflammatory in the context ofmicrobial infections [12].

CD80 (B7.1) and CD86 (B7.2) induce EBV-transformed B cell apoptosis through the Fas/FasL pathway

CD80 and CD86 expression is strongly regulated in B cells and is induced by various stimuli (e.g., cytokines, ligation of MHC class II and CD40 ligand). Epstein-Barr virus (EBV) infection activates B lymphocytes and transforms them into lymphoblastoid cells. However, the role of CD80 and CD86 in EBV infection of B cells remains unclear. Here, we observed that cross-linking of CD80 and CD86 in EBV-transformed B cells induced apoptosis through caspase-dependent release of apoptosis-related molecules, cytochrome c and apoptosis-inducing factor (AIF) from mitochondria, because Z-VAD-fmk (N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone) and N-acetylcysteine (NAC) blocked apoptosis and disruption of mitochondria. Stimulation of CD80 and CD86 induced expression of Fas ligand (FasL) on EBV-transformed B cells and upregulated Fas and FasL expression in IM-9 cells. Apoptosis through Fas-FasL interactions was blocked by treatment of cells with ZB4, an antagonistic anti-Fas antibody. These results suggest that the co-stimulatory molecules CD80 and CD86 induced by EBV infection stimulate apoptosis of EBV-transformed lymphoblastoid B cells via the Fas/FasL pathway.

Structural and Biophysical Characterization of the Interactions between the Death Domain of Fas Receptor and Calmodulin

The extrinsic apoptotic pathway is initiated by cell surface death receptors such as Fas. Engagement of Fas by Fas ligand triggers a conformational change that allows Fas to interact with adaptor protein Fas-associated death domain (FADD) via the death domain, which recruits downstream signaling proteins to form the death-inducing signaling complex (DISC). Previous studies have shown that calmodulin (CaM) is recruited into the DISC in cholangiocarcinoma cells, suggesting a novel role of CaM in Fas-mediated signaling. CaM antagonists induce apoptosis through a Fas-related mechanism in cholangiocarcinoma and other cancer cell lines possibly by inhibiting Fas-CaM interactions. The structural determinants of Fas-CaM interaction and the underlying molecular mechanisms of inhibition, however, are unknown. Here we employed NMR and biophysical techniques to elucidate these mechanisms. Our data show that CaM binds to the death domain of Fas (FasDD) with an apparent dissociation constant (Kd) of ~2 μM and 2:1 CaM:FasDD stoichiometry. The interactions between FasDD and CaM are endothermic and entropically driven, suggesting that hydrophobic contacts are critical for binding. We also show that both the N- and C-terminal lobes of CaM are important for binding. NMR and surface plasmon resonance data show that three CaM antagonists (N-(6-aminohexyl)-5-chloro-1-naphthalene sulfonamide, tamoxifen, and trifluoperazine) greatly inhibit Fas-CaM interactions by blocking the Fas-binding site on CaM. Our findings provide the first structural evidence for Fas-CaM interactions and mechanism of inhibition and provide new insight into the molecular basis for a novel role of CaM in regulating Fas-mediated apoptosis.

Increased Synapse Formation Obtained by T Cell Epitopes Containing a CxxC Motif in Flanking Residues Convert CD4+ T Cells into Cytolytic Effectors

The nature of MHC class II-binding epitopes not only determines the specificity of T cell responses, but may also alter effector cell functions. Cytolytic CD4+ T cells have been observed primarily in anti-viral responses, but very little is known about the conditions under which they can be elicited. Their potential as regulators of immune responses, however, deserves investigations. We describe here that inclusion of a thiol-disulfide oxidoreductase motif within flanking residues of class II-restricted epitopes results, both in vitro and in vivo, in elicitation of antigen-specific cytolytic CD4+ T cells through increased synapse formation. We show that both naïve and polarized CD4+ T cells, including Th17 cells, can be converted by cognate recognition of such modified epitopes. Cytolytic CD4+ T cells induce apoptosis on APCs by Fas-FasL interaction. These findings potentially open the way towards a novel form of antigen-specific immunosuppression.